PVC (polyvinyl chloride) modification additive, preparation method and sealing strip PVC

Abstract

The invention relates to a PVC (polyvinyl chloride) modification aid, a preparation method and a sealing strip PVC, belonging to the technical field of polyvinyl chloride composition modification aids and organic high-molecular compounds. The hardness of soft PVC (polyvinyl chloride) is greatly influenced by temperature, the softness cannot be kept under a low-temperature condition, and a rubber sealing strip is greatly influenced by a rubber material and a vulcanizing agent and has relatively strong odor and poor processability. The raw materials comprise butadiene-isoprene rubber, a polar grafting modifier and hydrogenated butadiene-acrylonitrile rubber and are obtained by mixing the butadiene-isoprene rubber, the polar grafting modifier and the hydrogenated butadiene-acrylonitrile rubber according to the weight ratio of 100: (1-10): (3-8). The rubber and PVC are blended to form an interpenetrating network structure, the advantages of PVC and rubber serving as a sealing strip are combined, and the sealing strip has excellent processability, excellent high and low temperature resistance and good oil resistance.

Description

Technical Field

[0001] The invention discloses a PVC modification auxiliary agent, a preparation method and a sealing strip PVC, belonging to the technical field of polyvinyl chloride composition modification auxiliary agents and organic polymer compounds. Background Art

[0002] As the main component of refrigerator sealing, the door seal should play a sealing role on the refrigerator. During use, it reduces the heat exchange between the air in the box and the outside world. On the other hand, it reduces the heat conduction effect of the material itself, which is also conducive to reducing heat exchange. The material of the refrigerator seal needs to meet the following conditions: 1) good density, soft material that is not easy to leak the medium, and good sealing surface fit; 2) appropriate mechanical strength and hardness, and small friction coefficient; 3) meet the process requirements of extrusion and hot melt welding; 4) anti-corrosion performance of weak acid, weak alkali and grease; 5) does not decompose or soften at high temperature, and does not harden at low temperature; 6) high resilience, good aging resistance, durable and environmentally friendly.

[0003] At present, the traditional refrigerator sealing strip materials mostly use soft polyvinyl chloride, such as a thermoplastic reinforced silica gel particle and its preparation method and application disclosed in patent CN113881231A. The hardness of soft PVC is greatly affected by temperature. It cannot maintain flexibility under low temperature conditions, and the sealing effect is relatively poor, and the aging resistance is poor. Rubber is considered to be one of the best sealing materials. The sealing strip made of high-quality rubber raw materials has a tough and thick texture, good elasticity, corrosion resistance, strong adsorption and good sealing performance. However, the rubber sealing strip is affected by the rubber material and the vulcanizing agent. The odor is large, and the main odor is rubber smell and bad odor. Poor environmental protection. At the same time, rubber processing is difficult and requires special extrusion equipment. Summary of the invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a PVC modification auxiliary agent with low odor, good processing performance, good sealing performance and low temperature resistance, a preparation method and a sealing strip PVC.

[0005] The technical solution adopted by the present invention to solve the technical problem is: a PVC modification auxiliary agent, characterized in that the raw materials include isoprene butadiene rubber, a polar grafting modifier and hydrogenated nitrile rubber, and the PVC modification auxiliary agent is obtained by mixing the isoprene butadiene rubber, the polar grafting modifier and the hydrogenated nitrile rubber in a weight ratio of 100:1-10:3-8.

[0006] Among them, the polar grafting modifier introduces more polar groups into the molecular main chain of butadiene isoprene rubber, improving its compatibility with hydrogenated nitrile rubber; the glass transition temperature of butadiene isoprene rubber can reach -104℃, and the rubber has excellent high and low temperature performance and good dynamic mechanical properties, and has excellent bonding performance with other materials. Hydrogenated nitrile rubber has excellent resistance to chemical media and oil, and its saturated structure brings excellent resistance to high temperature and heat-oxidation aging.

[0007] The colorless and transparent low-temperature resistant isoprene rubber and hydrogenated nitrile rubber are combined into a low-temperature oil-resistant composite material and blended with PVC by adding an initiator. After blending, the PVC and modified rubber composite material form an interpenetrating network structure. The blended thermoplastic elastomer has a plastic phase (PVC) as a continuous phase and a rubber phase as a dispersed phase. During the processing, it exhibits the extrudability and hot-melt welding characteristics of the plastic, and has excellent processing performance; during use, it also exhibits the elasticity of rubber. As a sealing material, it has excellent processing performance compared to rubber. Compared with the traditional refrigerator sealing strip material soft PVC, the material density is lower, and the comprehensive performance of environmental protection, oil resistance and aging resistance is more outstanding.

[0008] Preferably, the polar grafting modifier is cardanol.

[0009] Cardanol is a natural plasticizer that increases the free volume of the molecular chain, thereby promoting the fluidity of the molecule. When it is used as a side chain grafted into the rubber macromolecule, it can reduce the crystallinity of the polymer molecular chain, and the elongation at break tends to increase slightly. The reason is that after the flexible side chain is grafted, the flexibility of the molecular chain is improved, resulting in an increase in the elongation at break. Non-polar isoprene rubber grafted with polar cardanol has good compatibility with hydrogenated nitrile rubber. Therefore, using cardanol as a polar grafting modifier can not only improve the low-temperature modification ability of the additive, but also improve the compatibility of the two rubbers.

[0010] Further preferably, the weight ratio of cardanol to isoprene rubber is 2 to 5: 100. Too little cardanol leads to low grafting rate, while too much cardanol leads to high grafting rate, increased molecular weight, enhanced entanglement, and rigid benzene rings on the side chains of the product hinder the movement of melt macromolecules, resulting in poor melt fluidity.

[0011] Preferably, the weight ratio of the isoprene butadiene rubber to the hydrogenated nitrile rubber is 100:4-6. If the content of hydrogenated nitrile rubber is too high, the low temperature resistance will decrease, and if it is too low, the heat oxygen aging resistance will decrease.

[0012] Preferably, the hydrogenated nitrile rubber has a saturation degree of 79-96%, and has a high saturated structure and excellent high temperature resistance and heat-oxidation aging resistance.

[0013] A method for preparing the PVC modification additive is characterized by comprising the following steps: 1) The isoprene-butadiene rubber and the polar grafting modifier are subjected to internal mixing at 90-140°C to initiate grafting to obtain polar modified isoprene-butadiene rubber; 2) The polar modified isoprene butadiene rubber is mixed with hydrogenated nitrile rubber at 30-60°C to obtain a PVC modification additive.

[0014] Firstly, the isoprene butadiene rubber is grafted with a polar grafting modifier to ensure the compatibility of the isoprene butadiene rubber and the hydrogenated nitrile butadiene rubber, and then the PVC modification auxiliary agent is obtained by mixing the mixture at a specific temperature.

[0015] Preferably, the internal mixing initiation in step 1) is mechanical shear initiation at a rotation speed of 50-70 rpm. The shear force and thermal effect generated by kneading in the internal mixer can make the polar grafting modifier grafted onto the molecular chain of the isoprene butadiene rubber. If the rotation speed is too low, it may lead to uneven grafting, and if it is too high, it may lead to a decrease in the grafting rate and incomplete grafting reaction.

[0016] Preferably, the internal mixing speed of step 2) is 30-50 rpm.

[0017] A sealing strip PVC, characterized in that the raw materials include 2-10 parts of PVC, 0.1-1.0 parts of initiator and 100 parts of PVC modification auxiliary agent by weight, and the raw materials are mixed and reacted to initiate the reaction.

[0018] Preferably, the initiator is dibenzoyl peroxide (BPO).

[0019] Preferably, the preparation method of the sealing strip PVC comprises the following steps: 1) PVC modification additives and PVC are mixed to obtain a premix; 2) Add initiator to the premix, perform reaction extrusion and granulation to obtain sealing strip PVC; the reaction extrusion temperature is 170-175°C. The screw rotation frequency used for extrusion is preferably 3-8 Hz.

[0020] Compared with the prior art, the present invention has the following beneficial effects: the plastic phase (PVC) is used as the continuous phase and the rubber phase is used as the dispersed phase. During the processing, the present invention exhibits the characteristics of plastic extrudability and hot-melt welding, and has excellent processing performance. During use, the present invention exhibits the elasticity of rubber. As a sealing material, the present invention has excellent processing performance compared with rubber. Compared with the traditional refrigerator sealing strip material soft PVC, the material density is lower, and the comprehensive performance of environmental protection, oil resistance and aging resistance is more prominent. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with the embodiments, and Embodiment 1 is the best embodiment of the present invention.

[0022] Example 1 A PVC modification additive and a preparation method thereof, and a sealing strip PVC are prepared by the following steps: 1) 100 kg of isoprene butadiene rubber (cis content greater than 98%) and 2 kg of cardanol were mixed in a mixing chamber at an initial temperature of 90°C at a speed of 60 rpm for 20 min until the temperature reached 140°C for rubber discharge to obtain polar modified isoprene butadiene rubber.

[0023] 2) 90 kg of polar modified isoprene butadiene rubber and 5 kg of hydrogenated nitrile rubber (acrylonitrile content 33%, saturation 79%) were mixed in a mixing chamber at an initial temperature of 50°C and a rotation speed of 40 rpm for 10 min to obtain a PVC modification additive.

[0024] 3) Add 5 kg of PVC (DH2500 produced by Sinopec Qilu Branch) to the PVC modification additive in step 2), and continue to mix for 20 minutes under the same conditions in the mixing chamber as in step 2) to obtain a premix.

[0025] 4) The premix is ​​put into a twin-screw extruder and 0.5 kg of BPO is added for reaction extrusion and granulation. The temperature is controlled at 170-175°C and the screw rotation frequency is 5 Hz to obtain sealing strip PVC granules.

[0026] The pellets were extruded into 2 mm thick TPV sheets on a Brabender single screw extruder at 170-185°C, and dumbbell-shaped specimens were cut out using a sample making machine.

[0027] Example 2 A PVC modification additive and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, step 1) cardanol is set to 5 kg, and other conditions are the same as Example 1.

[0028] Example 3 A PVC modification auxiliary agent and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the hydrogenated nitrile rubber is selected to have a saturation of 96%, and other conditions are the same as those in Example 1.

[0029] Example 4 A PVC modification auxiliary agent and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the amount of hydrogenated nitrile rubber in step 2) is set to 7.2 kg, and other conditions are the same as in Example 1.

[0030] Example 5 A PVC modification additive and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the amount of hydrogenated nitrile rubber in step 2) is set to 2.7 kg, and other conditions are the same as in Example 1.

[0031] Example 6 A PVC modification auxiliary agent and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the amount of cardanol in step 1) is set to 10 kg, and other conditions are the same as in Example 1.

[0032] Example 7 A PVC modification auxiliary agent and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the amount of cardanol in step 1) is set to 1 kg, and other conditions are the same as in Example 1.

[0033] Comparative Example 1 A sealing strip PVC is prepared by weighing 100 kg of PVC resin, 5 kg of calcium zinc stabilizer, 70 kg of plasticizer TOTM, 10 kg of calcium carbonate and 2 kg of lubricant, adding the mixture into a high-speed mixer, and then mixing the mixture at a high speed. When the final mixing temperature reaches 110-120° C., the mixture is put into a low-speed mixer, and the mixture is discharged when the temperature drops to 40-45° C.

[0034] First, a double-roll mill is used to refine a sheet with a thickness of about 2 mm, the roller temperature is 150°C, and the plasticizing time is 2 to 3 minutes. Then a hot mold press is used to press it into a sheet with a thickness of 1 mm, and a dumbbell-shaped specimen is cut out by a sample making machine.

[0035] Comparative Example 2 A sealing strip rubber, 100kg EPDM rubber, 5kg zinc oxide, 10kg calcium carbonate, 5kg white carbon black, 2kg silane coupling agent Si69, 2.0kg accelerator CZ, 5.0kg zinc oxide, 1.0kg stearic acid are weighed and kneaded in an internal mixer for 10 minutes, the initial temperature of the internal mixer is 55°C, the rubber discharge temperature is 110°C, 2.0kg sulfur S is added at 65°C, a sheet with a thickness of about 2mm is kneaded, and vulcanized after being left for 24 hours. The rubber cannot be extruded.

[0036] Use a sample making machine to cut out dumbbell-shaped specimens.

[0037] Comparative Example 3 A sealing strip PVC is prepared by weighing 95 kg of PVC resin and 5 kg of hydrogenated nitrile rubber (hydrogenation degree 79%), mixing them together in an internal mixer at 50°C to prepare a premix, adding the premix into a twin-screw extruder, adding 0.5 kg of initiator BPO, reacting and extruding, and granulating. The temperature of the twin-screw extruder is controlled at 170-175°C, and the screw rotation frequency is 5 Hz, so as to obtain sealing strip PVC pellets.

[0038] The pellets were extruded into 2 mm thick TPV sheets on a Brabender single screw extruder at 170-185°C and dumbbell-shaped specimens were cut out using a sample making machine.

[0039] Comparative Example 4 A PVC modification additive and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, step 1) does not add cardanol and directly proceeds to step 2), and other conditions are the same as Example 1.

[0040] Comparative Example 5 A PVC modification aid and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, step 2) is not performed, but 95 kg of polar modified isoprene rubber obtained in step 1) is directly used as the PVC modification aid to perform steps 3) and 4), and other conditions are the same as in Example 1.

[0041] Comparative Example 6 A PVC modification auxiliary agent and a preparation method thereof, and a sealing strip PVC are prepared at the same time. On the basis of Example 1, the amount of hydrogenated nitrile rubber in step 2) is set to 10 kg, and other conditions are the same as in Example 1.

[0042] Performance Testing The dumbbell-shaped specimens obtained in the above embodiments and comparative examples were subjected to performance tests, and the test results are shown in Table 1 below.

[0043] Among them, the tensile strength performance test standard: tested according to GB / T 528-2009 standard.

[0044] Elongation at break performance test standard: Tested according to GB / T 528-2009 standard.

[0045] Compression set performance test standard: Tested according to GB / T7759.1-2015 standard.

[0046] Brittle temperature test standard: DMA test tanδ-T curve scanning: sample size 80 mm×10 mm×2 mm, vibration frequency 10 Hz, heating rate 3℃ / min, scanning temperature range -100℃~100℃.

[0047] Odor level: Use the PV3900 odor test standard and specify the EINKOCISPA β container of LEIFHEIT as the standard container. Put 20±0.1g of pellets in the container and bake it in an oven at 80±2℃ for 2h±10min. Take it out and test the odor when it cools to 60±5℃. There must be no less than 3 testers.

[0048] Thermal conductivity test standard: The sample is a disc with a diameter of 50mm and a thickness of 2mm. During measurement, the temperatures of the two contact surfaces are 25℃ and 60℃ respectively. After the heat conduction is stable, the thermal conductivity of the sample is directly read.

[0049] Liquid resistance test: Test according to GB / T 1690-2010 "Test method for liquid resistance of vulcanized rubber or thermoplastic rubber".

[0050] Table 1 Performance test results .

[0051] According to the above performance test results, after the PVC modification additive is used in the embodiment, the low temperature performance, oil resistance and compression permanent deformation performance are significantly improved, and extrusion processing can be achieved, which is convenient for processing and reduces odor, meeting the use requirements of refrigerator sealing strips.

[0052] The above is only a preferred embodiment of the present invention, and does not limit the present invention in other forms. Any technician familiar with the profession may use the above disclosed technical content to change or modify it into an equivalent embodiment with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention without departing from the technical solution of the present invention still belongs to the protection scope of the technical solution of the present invention.

Claims

1. A PVC modification additive, characterized in that: The raw materials include isoprene butadiene rubber, polar grafting modifier and hydrogenated nitrile rubber, which are obtained by mixing the isoprene butadiene rubber, polar grafting modifier and hydrogenated nitrile rubber in a weight ratio of 100:1-10:3-8.

2. The PVC modification aid according to claim 1, characterized in that: The polar grafting modifier is cardanol.

3. The PVC modification aid according to claim 2, characterized in that: The weight ratio of the cardanol to the isoprene rubber is 2-5:

100.

4. The PVC modification aid according to claim 1, characterized in that: The weight ratio of the isoprene butadiene rubber to the hydrogenated nitrile rubber is 100:4-6.

5. The PVC modification aid according to claim 1, characterized in that: The hydrogenated nitrile rubber has a saturation degree of 79-96%.

6. A method for preparing a PVC modification additive according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) The isoprene-butadiene rubber and the polar grafting modifier are subjected to internal mixing at 90-140°C to initiate grafting to obtain polar modified isoprene-butadiene rubber; 2) The polar modified isoprene butadiene rubber is mixed with hydrogenated nitrile rubber at 30-60°C to obtain a PVC modification additive.

7. The method for preparing the PVC modification aid according to claim 6, characterized in that: The mixing initiation in step 1) is mechanical shearing initiation at a rotation speed of 50-70 rpm.

8. The method for preparing the PVC modification additive according to claim 6, characterized in that: The mixing speed of the internal kneading in step 2) is 30-50 rpm.

9. A sealing strip PVC, characterized by: The raw materials include 2-10 parts of PVC, 0.1-1.0 parts of initiator and 100 parts of PVC modification aid by weight, and the raw materials are mixed to initiate reaction; the PVC modification aid is prepared by the preparation method of the PVC modification aid described in any one of claims 1 to 5 or the PVC modification aid described in any one of claims 6 to 8.

10. The sealing strip PVC according to claim 9, characterized in that: The preparation method comprises the following steps: 1) PVC modification additives and PVC are mixed to obtain a premix; 2) Add initiator to premix, perform reaction extrusion and granulation to obtain sealing strip PVC; the reaction extrusion temperature is 170~175℃.