High-molecular-weight, high-elasticity, high-heat-resistance extruded PVC material and its preparation method

Abstract

The application discloses a high-molecular-weight high-elasticity high-heat-resistance extruded PVC material and a preparation method thereof. High-molecular-weight PVC, active calcium carbonate, phthalate compounds and additives are heated and mixed, then powder butyronitrile is cold-mixed and added, the mixture is sieved after mixing, and then the mixture is extruded and granulated to obtain the high-molecular-weight high-elasticity high-heat-resistance extruded PVC material. The high-molecular-weight PVC resin powder and a small amount of butyronitrile rubber are matched, calcium carbonate is supplemented, and a limited dispersion modifier is matched to prepare soft PVC material with high elasticity and high surface appearance quality, which is successfully used in the seal strip product with the highest requirement on the surface of an automobile.

Description

Technical Field

[0001] This invention pertains to plastic modification technology, specifically relating to a high molecular weight, high elasticity, and high heat-resistant extruded PVC material and its preparation method. Background Technology

[0002] PVC is one of the most widely produced general-purpose plastics, with advantages in low overall cost and excellent surface appearance, making it a promising material for development and application. Currently, automotive sealing strips often use environmentally friendly thermoplastic elastomers such as PVC and TPV. Compared to other thermoplastic elastomers, PVC has a significant deficiency in compression set (i.e., elasticity), often putting it at a disadvantage in this area. Current methods to improve PVC elasticity mainly involve adding various rubber modifiers, such as adding more than 10% powdered nitrile rubber, which can effectively improve PVC elasticity and also enhance its low-temperature brittleness. This is the most common method for improving PVC elasticity. Existing technology uses a water and hydrazine method to hydrogenate nitrile latex, preparing powdered hydrogenated nitrile rubber (PHNBR) through a coagulation method. After adding powdered rubber, the material modulus decreases; however, with increasing amounts of powdered hydrogenated nitrile rubber, the tensile strength does not change significantly, while the elongation at break increases, and the toughness is improved. Existing technology uses powdered nitrile rubber Chemgium P83 to modify soft PVC, significantly improving its oil resistance. However, existing powdered nitrile rubber modified products are prone to forming appearance defects such as particles on the surface of PVC extruded sealing strips, which reduces the product qualification rate. Summary of the Invention

[0003] This invention employs a method combining high molecular weight PVC resin powder and a small amount of nitrile rubber, along with calcium carbonate and phthalate compounds, to prepare a soft PVC material with high elasticity and excellent surface appearance quality. This material has been successfully used in automotive sealing strips, which have the highest surface requirements.

[0004] The present invention adopts the following technical solution: A high molecular weight, high elasticity, and high heat resistance extruded PVC material includes high molecular weight PVC, activated calcium carbonate, phthalate compounds, powdered nitrile butadiene, and additives.

[0005] This invention discloses a method for preparing the above-mentioned high molecular weight, high elasticity, and high heat resistance extruded PVC material, comprising the following steps: heating and mixing high molecular weight PVC, activated calcium carbonate, phthalate compounds and additives, then cold mixing with powdered nitrile, mixing, sieving the mixture, and then extruding and granulating to obtain high molecular weight, high elasticity, and high heat resistance extruded PVC material.

[0006] In this invention, the PVC resin powder is a thermoplastic polymeric resin. The high molecular weight PVC of this invention has a degree of polymerization of 1500 or higher, such as 1600-2500, preferably 1800-2000, referring to the average degree of polymerization. The activated calcium carbonate is selected as 1000-1500 mesh activated heavy calcium carbonate. The phthalate compound is DINP: diisononyl phthalate. The processing agents are conventional components in existing PVC processing, mainly some additives that improve processing fluidity and stability.

[0007] In this invention, the mass ratio of high molecular weight PVC, activated calcium carbonate, phthalate compound, powdered nitrile butadiene oxide, and additives is 100:(30-50):(50-70):(3-9):(5-15). Preferably, the mass ratio of high molecular weight PVC, activated calcium carbonate, phthalate compound, powdered nitrile butadiene oxide, and additives is 100:(35-45):(55-65):(4-8):(7-12). More preferably, the mass ratio of high molecular weight PVC and powdered nitrile butadiene oxide is 100:(4-6).

[0008] In this invention, high molecular weight PVC, activated calcium carbonate, a portion of phthalate compounds, and additives are mixed and heated to 80–90°C. The remaining phthalate compounds are then added, and the temperature is raised to 140–160°C. After mixing, the mixture is cooled, and powdered nitrile is added. The mixture is then passed through a 20–50 mesh sieve and extruded to granulate, yielding a high molecular weight, high elasticity, and high heat-resistant extruded PVC material. Preferably, the cooling rate to room temperature is 5–15°C / min, more preferably 8–12°C / min.

[0009] This invention discloses the application of the above-mentioned high molecular weight, high elasticity, and high heat resistance extruded PVC material in the preparation of automotive sealing strip materials.

[0010] This invention discloses an automotive sealing strip material, which is prepared from the above-mentioned high molecular weight, high elasticity, and high heat-resistant extruded PVC material.

[0011] Currently, the problems with modified PVC are: the high cost of nitrile rubber reduces the cost advantage of PVC, and the product appearance is poor; the uneven particle size of powdered nitrile rubber easily forms visible particles, and nitrile rubber also tends to agglomerate during mixing, affecting the product's appearance. This invention significantly reduces the amount of powdered nitrile rubber modifier used, achieving an absolute cost advantage. It uses high molecular weight PVC resin powder combined with dispersants and fillers, while still meeting the elasticity requirements of automotive sealing strips. This invention effectively disperses the powdered nitrile rubber, and combined with the smaller amount of powdered nitrile rubber used, results in a highly elastic soft PVC with an excellent appearance, meeting customer appearance requirements. Attached Figure Description

[0012] Figure 1The material prepared for the product of Example 2 of this invention has a very good appearance.

[0013] Figure 2 This is a defect that has occurred in existing PVC extruded products. Detailed Implementation

[0014] This invention relates to a high-molecular-weight, high-elasticity, and high-heat-resistant extruded PVC material prepared from high-molecular-weight PVC, activated calcium carbonate, phthalate compounds, powdered nitrile butadiene rubber, and additives. By selecting a high-polymerization-degree resin and reducing the use of nitrile butadiene rubber, combined with an improved mixing process, it is unexpected that a higher elasticity PVC can be produced at normal granulation temperature without increasing the temperature, and the test pieces show excellent appearance.

[0015] This invention first involves high-molecular-weight PVC, activated calcium carbonate, phthalate compounds, and additives, which are then mixed at high speed under heating. Next, powdered nitrile butadiene is added and mixed at low speed under cold conditions. Finally, the mixture is sieved and granulated. Specifically, it consists of three steps: 1. Hot mixing: First, put high molecular weight PVC resin powder, active calcium carbonate powder and additives into a pot, then add 60-70 wt% DINP, heat and stir, add the remaining DINP at about 85℃ to prevent resin gelation, and then stir at 145-155℃ for 30-50 minutes to obtain the premix. 2. Cold mixing: The cooling rate is 5-15℃ / min. The temperature of the premix is ​​reduced to below 60℃. Powdered nitrile rubber is added and stirred until room temperature is reached to obtain the mixture. 3. Granulation: First, sieve the mixture on a vibrating screen, then take the sieve material and select a twin-screw granulator with a length-to-diameter ratio of (50-80):1. The granulation temperature is 140±5℃ to successfully granulate and obtain high molecular weight, high elasticity, and high heat resistance extruded PVC material.

[0016] The technical solution of the present invention and the resulting technological advancements are illustrated below through specific embodiments and comparative examples. The raw materials involved are all conventional products in the field, which can meet the conventional requirements for plastic modification. The specific preparation operations and performance tests are conventional techniques, such as a stirring speed of 500 to 2000 rpm. Example

[0017] Material Specifications. PVC Resin Powder (Formosa Plastics): Thermoplastic polymer resin, PVC resin powder manufactured by the ethylene process, S-70 / S-80 / S-85; Activated Calcium Carbonate, Jiangxi Guangyuan, selected 1250 mesh activated heavy calcium carbonate; Powdered Nitrile Rubber, Lanxess 3446.

[0018] Weathering agent, BASF UV-P; antioxidant, Ningbo Baizhi 1076; heat stabilizer, Jiangsu Biaopu 91660KA-2; lubricant, Anhui Shafeng 230P; processing aid, Ningbo Baizhi P-201; colorant, 1935E. The weathering agent, antioxidant, heat stabilizer, lubricant, processing aid, and colorant are mixed in a mass ratio of 1:0.5:0.8:1:1:1.5.

[0019] DINP: diisononyl phthalate; DOP: dioctyl phthalate.

[0020] Based on the raw material composition in Table 1, PVC materials are prepared using the following processing method: 1. Hot mixing: Select a 500L mixer. First, put all the PVC resin powder, calcium powder and additives into the pot, then add 2 / 3 of the DINP, heat from room temperature to 85℃ at 5℃ / min, then add the remaining DINP, and then heat to 150℃ and mix for 40 minutes to obtain the premix. 2. Cold mixing: Add the premix to a 1000-liter mixer and cool it down at a rate of 10℃ / min. When the temperature of the premix drops to 60℃, add the powdered nitrile rubber and stir until it reaches room temperature to obtain the mixture. 3. Granulation: First, sieve the mixture on a 30-mesh vibrating screen, then take the sieve material and select a conical twin-screw granulator with a length-to-diameter ratio of 65:1. Granulation can be successfully completed at a granulation temperature of 145℃ to prepare PVC material.

[0021] Material testing methods: Compression set: Requires less than 50% at 70°C for 22 hours, in accordance with ISO 815.

[0022] Elongation: According to ISO 37, 500 mm / min, the requirement is above 350%.

[0023] Shore Hardness: According to ISO 868, 15s reading, Shore A, requirement 70±5A. Tensile Strength: According to ISO 37, 500mm / min, requirement ≥12MPa. Hot Air Aging Resistance: According to the ISO 188 standard for automotive parts, after storage at 85℃ for 72h, the hardness change rate should be ≤8%, and the change rate of tensile strength and elongation at break should be ≥-20%. Thermal Stability: According to GB / T 2917.1, PVC thermal stability must be maintained at 180℃ for 2h without decomposition, and the appearance should not cause discoloration of Congo red test paper. Low Temperature Resistance: According to GB / T 5740, at -40℃, it should not break under low temperature impact. The products in Example 2 all meet the above requirements, with a Shore hardness of 68A, a tensile strength of 13.72MPa, a hardness change of +0.7% after hot air aging, a tensile strength change of +1.2% after hot air aging, and an elongation change of -1.3%.

[0024] Test film production method: A. First, use a two-roll mill to produce sample sheets. The machine surface temperature is 150℃, the temperature of soft materials is close to the lower limit, and the temperature of hard materials is close to the upper limit. After maintaining the constant temperature for 30 minutes, start extruding the sheets, which will be 2.2mm thick.

[0025] B. Then, the sample is molded in the molding machine. After the mold temperature is kept constant for half an hour, the sample is added and kept warm for 30 minutes; pressure is applied (10MPa) and held for 4 hours (opening and closing the mold two or three times to release air); heating is stopped and the temperature is lowered; the demolding temperature is 40℃, and the test sample is obtained.

[0026] Evaluation method for specimen appearance: Extrude a 1mm thin specimen using a torque rheometer and observe the particle count on its surface under strong light. A smooth, particle-free surface is acceptable; otherwise, it is not. Some particles with a compression set of more than 50% were not tested for specimen fabrication.

[0027] Table 1. Raw materials for the examples and comparative examples, in kg.

[0028] The data comparison in Table 1 shows that the material properties of the PVC particles prepared in Examples 2, 3, 4, and 5 all meet the requirements. Further testing of sample processing revealed that 8 parts of powdered nitrile had an impact on the processing. In summary, Example 2 is the best verified solution, as it meets the performance requirements, the appearance of the sample meets the requirements, and the processing is simple. Replacing the best-performing PVC material currently used by the customer with Example 2, production verification was conducted, and no products with poor appearance were observed. Figure 1 This is one piece, but existing PVC materials have poor appearance, resulting in a low pass rate and high cost.

[0029] Based on Example Group 2, the amount of powdered nitrile was adjusted to 4.5 kg or 6 kg, while the rest remained the same. All properties of the obtained PVC particles met the requirements, the test pieces met the requirements, and the processing was simple.

[0030] Currently, the problems with modified PVC are: the high cost of nitrile rubber reduces the cost advantage of PVC, and the product appearance is poor; the uneven particle size of powdered nitrile rubber easily forms visible particles, and nitrile rubber also tends to agglomerate during mixing, forming visible particles that affect the product's appearance. In current production, when using PVC extrusion for automotive seals, poor appearance leads to a low pass rate. Figure 2The images show defective products during the production process. Combined with the high price of powdered nitrile rubber, this makes PVC seals even more expensive. This invention abandons conventional rubber modification methods, reducing costs and simplifying complex processes. While improving process conditions and reducing costs, it also ensures product quality and high appearance requirements. This invention significantly reduces the amount of powdered nitrile rubber modifier used, giving it an absolute cost advantage. It uses high molecular weight PVC resin powder combined with dispersants and fillers to achieve the same elasticity requirements for automotive sealing strips. This invention effectively disperses the powdered nitrile rubber, and combined with the smaller amount of powdered nitrile rubber used, results in a highly elastic, soft PVC with an excellent appearance, meeting customer appearance requirements.

Claims

1. A high molecular weight, high elasticity, and high heat-resistant extruded PVC material, characterized in that, It is prepared from high molecular weight PVC, activated calcium carbonate, phthalate compound, powdered nitrile butadiene, and additives; the mass ratio of high molecular weight PVC, activated calcium carbonate, phthalate compound, powdered nitrile butadiene, and additives is 100:(35-45):(55-65):(4-6):(7-12); the phthalate compound is DINP; the additives are a mixture of weathering agent, antioxidant, heat stabilizer, lubricant, processing aid, and colorant in a mass ratio of 1:0.5:0.8:1:1:1.5; the degree of polymerization of high molecular weight PVC is 1800; the activated calcium carbonate is selected as 1000-1500 mesh activated heavy calcium carbonate; the weathering agent is BASF UV-P, and the processing aid is Ningbo Baizhi P-201.

2. The method for preparing the high molecular weight, high elasticity, and high heat-resistant extruded PVC material according to claim 1, characterized in that, The process includes the following steps: heating and mixing high molecular weight PVC, activated calcium carbonate, phthalate compounds and additives, then cold mixing with powdered nitrile, then sieving the mixture, and finally extruding and granulating it to obtain a high molecular weight, high elasticity and high heat resistance extruded PVC material.

3. The method for preparing high molecular weight, high elasticity, and high heat-resistant extruded PVC material according to claim 2, characterized in that, High molecular weight PVC, activated calcium carbonate, some phthalate compounds and additives are mixed and heated to 80-90°C. The remaining phthalate compounds are then added and the temperature is raised to 140-160°C. After mixing, the mixture is cooled and powdered nitrile is added. The mixture is then passed through a 20-50 mesh sieve and extruded to obtain a high molecular weight, high elasticity and high heat resistance extruded PVC material.

4. The application of the high molecular weight, high elasticity, and high heat resistance extruded PVC material according to claim 1 in the preparation of automotive sealing strip materials.

5. An automotive sealing strip material, prepared from the high molecular weight, high elasticity, and high heat-resistant extruded PVC material as described in claim 1.

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