PVC modification aid, preparation method and sealing strip PVC

Abstract

The application discloses a PVC modification aid, a preparation method and a sealing strip PVC, and belongs to the technical fields of polyvinyl chloride composition modification aids and organic polymer compounds. The hardness of soft PVC is greatly affected by temperature, and the softness cannot be maintained under low-temperature conditions. Rubber sealing strips are greatly affected by rubber materials and vulcanizing agents in terms of odor and processing performance. The raw materials of the application include butyl isoprene rubber, a polar graft modifier and hydrogenated butyl nitrile rubber, and are obtained by mixing the butyl isoprene rubber, the polar graft modifier and the hydrogenated butyl nitrile rubber according to a weight ratio of 100:1-10:3-8. After being blended with PVC, the butyl isoprene rubber, the polar graft modifier and the hydrogenated butyl nitrile rubber form an interpenetrating network structure, and have excellent processing performance, excellent high and low temperature resistance and good oil resistance while combining the advantages of PVC and rubber as sealing strips.

Description

TECHNICAL FIELD

[0001] The application relates to a PVC modification aid, a preparation method and a sealing strip PVC, and belongs to the technical field of polyvinyl chloride composition modification aids and organic polymer compounds. BACKGROUND

[0002] As a main part of refrigerator sealing, the door sealing strip needs to play a sealing role on the refrigerator and reduce the heat exchange between the air in the refrigerator and the outside in the use process. On the other hand, the heat conduction effect of the material itself is reduced, which is also beneficial to reducing the heat exchange. The refrigerator sealing strip material needs to meet the following conditions: 1) a soft material with good tightness and not easy to leak medium, and good sealing surface adhesion; 2) appropriate mechanical strength and hardness, and small friction coefficient; 3) meeting the process requirements of extrusion and hot melt welding; 4) corrosion resistance to weak acid, weak base and oil; 5) not decomposed and softened at high temperature, and not hardened at low temperature; 6) high resilience, good aging resistance, durable and environmentally friendly.

[0003] At present, the traditional refrigerator sealing strip material mostly adopts soft polyvinyl chloride. For example, the patent CN113881231A discloses a thermoplastic reinforced silica gel particle and a preparation method and application thereof. The hardness of the soft PVC is greatly affected by temperature, and the softness cannot be maintained under low temperature conditions, so that 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 is tough, thick, elastic, corrosion-resistant, has strong adsorption and good sealing performance, but the rubber sealing strip is greatly affected by the rubber material and vulcanizing agent, and the odor is mainly rubbery and smelly. The environmental protection is poor. At the same time, the rubber is difficult to process and special extrusion equipment is needed. SUMMARY

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

[0005] The technical scheme adopted by the application to solve the technical problem is that the PVC modification aid is characterized in that the raw materials include butyl isoprene rubber, a polar graft modifier and hydrogenated butyl nitrile rubber, and the butyl isoprene rubber, the polar graft modifier and the hydrogenated butyl nitrile rubber are mixed at a weight ratio of 100:1-10:3-8.

[0006] The polar grafting modifier introduces more polar groups into the molecular main chain of the butadiene isoprene rubber, thereby improving the compatibility with the hydrogenated nitrile rubber; the butadiene isoprene rubber has a cold resistance of -104℃, excellent high and low temperature performance, and good dynamic mechanical performance, and excellent adhesion to other materials. The hydrogenated nitrile rubber has excellent chemical medium resistance and oil resistance, and excellent high temperature resistance and heat aging resistance due to the saturated structure.

[0007] The colorless and transparent butadiene isoprene rubber with low temperature resistance is combined with the hydrogenated nitrile rubber to form a low temperature oil resistant composite material, and the PVC is added with an initiator and blended. After the blending, the PVC and the 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, and has excellent extrudability and hot melt weldability in the processing process. In the use process, the blended thermoplastic elastomer also has excellent elasticity as a rubber. Compared with traditional refrigerator sealing strip materials, the blended thermoplastic elastomer has lower material density, and has more outstanding comprehensive performance in environmental protection, oil resistance and aging resistance.

[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 molecules. When it is grafted as a side chain to the rubber macromolecule, the crystallinity of the polymer molecular chain is reduced, and the elongation at break shows a slight increasing trend. After the non-polar butadiene isoprene rubber is grafted with the polar cardanol, the butadiene isoprene rubber has good compatibility with the hydrogenated nitrile rubber. Therefore, the use of cardanol as a polar grafting modifier can improve the low temperature modification ability of the additive and the compatibility of the two rubbers.

[0010] Further preferably, the weight ratio of the cardanol to the butadiene isoprene rubber is 2-5:100. If the amount of cardanol is too small, the grafting rate is low, and if the amount of cardanol is too large, the grafting rate is high, the molecular weight increases, the entanglement effect increases, and the rigid benzene ring on the side chain of the product hinders the movement of the melt macromolecule, and the melt fluidity becomes poor.

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

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

[0013] A method for preparing the PVC modification additive is characterized by comprising the following steps:

[0014] 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;

[0015] 2) Polar modified isoprene butadiene rubber is mixed with hydrogenated nitrile butadiene rubber at 30-60°C to obtain a PVC modification additive.

[0016] 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 additive is obtained by mixing the mixture at a specific temperature.

[0017] Preferably, the internal mixing initiation in step 1) is mechanical shear initiation at a rotational speed of 50-70 rpm. The shear force and thermal effects generated by kneading in an internal mixer can cause the polar graft modifier to be grafted onto the isoprene-butadiene rubber molecular chains. Too low a rotational speed may result in uneven grafting, while too high a rotational speed may result in a decreased grafting rate and incomplete grafting reaction.

[0018] Preferably, the internal mixing speed of step 2) is 30-50 rpm.

[0019] A sealing strip PVC is 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 in parts by weight, and the raw materials are mixed and reacted to initiate the reaction.

[0020] Preferably, the initiator is dibenzoyl peroxide (BPO).

[0021] Preferably, the preparation method of the sealing strip PVC comprises the following steps:

[0022] 1) PVC modification additives and PVC are mixed to obtain a premix;

[0023] 2) Adding an initiator to the premix, extruding, and granulating to obtain the sealing strip PVC; the reaction extrusion temperature is 170-175°C. The screw rotation frequency used for extrusion is preferably 3-8 Hz.

[0024] Compared with the existing technology, 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, it exhibits the extrudability and hot-melt welding properties of plastic, with excellent processing performance. During use, it also exhibits the elasticity of rubber. As a sealing material, it 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 outstanding. DETAILED DESCRIPTION

[0025] The application will be further described in connection with the following examples, of which example 1 is the best mode of the application.

[0026] Example 1

[0027] A PVC modifying agent and its preparation method, and a sealing strip PVC are prepared simultaneously, using the following steps:

[0028] 1) 100 kg of butadiene isoprene rubber (cis content greater than 98%) is mixed with 2 kg of cardanol in a mixing chamber at an initial temperature of 90°C, at a speed of 60 rpm for 20 min to 140°C to discharge the rubber, to obtain polar modified butadiene isoprene rubber.

[0029] 2) The polar modified butadiene isoprene rubber 90 kg is mixed with hydrogenated butadiene nitrile rubber (acrylonitrile content 33%, saturation degree 79%) 5 kg in a mixing chamber at an initial temperature of 50°C, at a speed of 40 rpm for 10 min to obtain a PVC modifying agent.

[0030] 3) Add 5 kg of PVC (DH2500 produced by Qilu Branch of Sinopec) to the PVC modifying agent of step 2), continue mixing in the mixing chamber of step 2) for 20 min to obtain a premix.

[0031] 4) Put the premix into a twin-screw extruder and add BPO 0.5 kg for reaction extrusion, granulation, temperature control at 170~175°C, screw rotation frequency 5 Hz, to obtain sealing strip PVC granules.

[0032] The granules are extruded into 2mm thick TPV sheets on a Brabender single screw extruder set at 170~185°C, and dumbbell-shaped samples are cut out using a sample preparation machine.

[0033] Example 2

[0034] A PVC modifying agent and its preparation method, and a sealing strip PVC are prepared simultaneously, on the basis of example 1, step 1) cardanol is set to 5 kg, and other conditions are the same as example 1.

[0035] Example 3

[0036] A PVC modifying agent and its preparation method, and a sealing strip PVC are prepared simultaneously, on the basis of example 1, hydrogenated butadiene nitrile rubber is selected as hydrogenated butadiene nitrile rubber with a saturation degree of 96%, and other conditions are the same as example 1.

[0037] Example 4

[0038] A PVC modification aid and a preparation method thereof, and a sealing strip PVC is prepared simultaneously, on the basis of example 1, in step 2), the amount of hydrogenated butyl rubber is set to 7.2 kg, and other conditions are the same as in example 1.

[0039] Example 5

[0040] A PVC modification aid and a preparation method thereof, and a sealing strip PVC is prepared simultaneously, on the basis of example 1, in step 2), the amount of hydrogenated butyl rubber is set to 2.7 kg, and other conditions are the same as in example 1.

[0041] Example 6

[0042] A PVC modification aid and a preparation method thereof, and a sealing strip PVC is prepared simultaneously, on the basis of example 1, in step 1), the amount of cardanol is set to 10 kg, and other conditions are the same as in example 1.

[0043] Example 7

[0044] A PVC modification aid and a preparation method thereof, and a sealing strip PVC is prepared simultaneously, on the basis of example 1, in step 1), the amount of cardanol is set to 1 kg, and other conditions are the same as in example 1.

[0045] Comparative example 1

[0046] A sealing strip PVC, 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 are weighed and added to a high-speed mixer, and then high-speed mixed. When the final mixing temperature reaches 110-120℃, the material is placed in a low-speed mixer. When the material drops to 40-45℃, the material is discharged.

[0047] First, a sheet with a thickness of about 2 mm is opened on a two-roll mill, the roll temperature is 150℃, and the plasticizing time is 2-3 min. Then, a hot die press is used to press the sheet into a thickness of 1 mm. A dumbbell-shaped sample is cut out by a sample preparation machine.

[0048] Comparative example 2

[0049] A sealing strip rubber, 100 kg of ethylene-propylene-diene rubber, 5 kg of zinc oxide, 10 kg of calcium carbonate, 5 kg of white carbon black, 2 kg of silane coupling agent Si69, 2.0 kg of accelerator CZ, 5.0 kg of zinc oxide, and 1.0 kg of stearic acid are weighed and mixed in an internal mixer for 10 min. The initial temperature of the internal mixer is 55℃, and the discharge temperature is 110℃. Sulfur S2.0 kg is added to the opening mill at 65℃, and a sheet with a thickness of about 2 mm is opened. After 24 hours, the rubber is vulcanized. The rubber cannot be processed by extrusion.

[0050] A dumbbell-shaped sample is cut out by a sample preparation machine.

[0051] Comparative Example 3

[0052] A sealing strip PVC is prepared by weighing 95 kg of PVC resin and 5 kg of hydrogenated nitrile rubber (hydrogenation degree 79%), mixing the mixture together at 50° C. in an internal mixer to prepare a premix. The premix is ​​then added to a twin-screw extruder and 0.5 kg of initiator BPO is added for reaction extrusion and pelletization. The temperature of the twin-screw extruder is controlled at 170-175° C., and the screw rotation frequency is 5 Hz, to obtain sealing strip PVC pellets.

[0053] 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.

[0054] Comparative Example 4

[0055] A PVC modification additive and a preparation method thereof, and a sealing strip PVC are also prepared. Based on Example 1, step 1) does not add cardanol and step 2 is directly performed. Other conditions are the same as in Example 1.

[0056] Comparative Example 5

[0057] A PVC modification agent and a preparation method thereof, and a sealing strip PVC are also prepared. Based on Example 1, step 2) is omitted, and instead, 95 kg of polar-modified isoprene butadiene rubber obtained in step 1) is directly used as the PVC modification agent to carry out steps 3) and 4). Other conditions are the same as in Example 1.

[0058] Comparative Example 6

[0059] A PVC modification additive and a preparation method thereof, and a sealing strip PVC are also prepared. Based on Example 1, the amount of hydrogenated nitrile rubber used in step 2) is set to 10 kg, and other conditions are the same as in Example 1.

[0060] Performance Testing

[0061] 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.

[0062] Among them, the tensile strength performance test standard: tested according to GB / T528-2009 standard.

[0063] Elongation at break performance test standard: tested according to GB / T528-2009 standard.

[0064] Compression set performance test standard: tested according to GB / T7759.1-2015 standard.

[0065] Brittle temperature test standard: DMA test tanδ-T curve scanning: sample size 80mm×10mm×2mm, vibration frequency 10Hz, heating rate 3℃ / min, scanning temperature range -100℃~100℃.

[0066] Odor level: Use the PV3900 odor test standard and designate the EINKOCISPAβ container of LEIFHEIT as the standard container. Place 20±0.1g of pellets in the container and bake in an oven at 80±2℃ for 2h±10min. Then take out and test the odor when the temperature cools to 60±5℃. There must be no less than 3 testers.

[0067] 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. The thermal conductivity of the sample is directly read after the heat conduction stabilizes.

[0068] Liquid resistance test: Test according to GB / T1690-2010 "Test method for liquid resistance of vulcanized rubber or thermoplastic rubber".

[0069] Table 1 Performance test results

[0070] .

[0071] 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 to process and the odor is reduced, meeting the use requirements of refrigerator sealing strips.

[0072] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A PVC modification additive, characterized in that: The raw materials include isoprene butadiene rubber, a polar graft modifier and hydrogenated nitrile rubber, and are obtained by mixing the isoprene butadiene rubber, the polar graft modifier and the hydrogenated nitrile rubber in a weight ratio of 100:1-10:3-8; the polar graft modifier is cardanol; the weight ratio of cardanol to isoprene butadiene rubber is 2-5:100; and the weight ratio of isoprene butadiene rubber to hydrogenated nitrile rubber is 100:4-6.

2. The PVC modification agent according to claim 1, characterized in that: The saturation degree of the hydrogenated nitrile rubber is 79-96%.

3. A method for preparing the PVC modification additive according to any one of claims 1 to 2, 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) Polar modified isoprene butadiene rubber is mixed with hydrogenated nitrile butadiene rubber at 30-60°C to obtain a PVC modification additive.

4. The preparation method of the PVC modification additive according to claim 3, wherein: The mixing initiation in step 1) is mechanical shearing initiation at a rotation speed of 50-70 rpm.

5. The preparation method of the PVC modification additive according to claim 3, wherein: The mixing speed of the internal kneading in step 2) is 30-50 rpm.

6. A PVC sealing strip, characterized by: The raw materials include 2 to 10 parts of PVC, 0.1 to 1.0 parts of initiator and 100 parts of PVC modification aid in parts by weight, and the raw materials are mixed and reacted to initiate the reaction; the PVC modification aid is prepared by the preparation method of the PVC modification aid according to any one of claims 1 to 2 or the PVC modification aid according to any one of claims 3 to 5.

7. The PVC sealing strip according to claim 6, characterized in that: The preparation method comprises the following steps: 1) PVC modification additives and PVC are mixed to obtain a premix; 2) Adding an initiator to the premix, reacting, extruding, and granulating to obtain sealing strip PVC; the reaction extrusion temperature is 170~175℃.