Method for preparing a few-skin film suspension method PVC resin
By adding non-polar microspheres to the suspension polymerization of PVC resin, the problem of complex operation and difficulty in separating dispersants in the existing technology is reduced by using physical isolation methods. This achieves stable and easy preparation of PVC resin with less film, which is suitable for soft products and chlorinated modified products.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHINA PETROLEUM & CHEMICAL CORP
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies for preparing low- or low-film suspension PVC resins involve complex operations, difficulty in controlling the granulation process, and a tendency to produce coarse materials and sticky materials. Furthermore, the dispersant dosage is large and cannot be separated from the PVC resin.
By employing a physical isolation method, non-polar microspheres or materials that are sparsely related to VCM monomers are added during the polymerization process to reduce the probability of agglomeration during PVC particle formation. The morphology of resin particles is adjusted through the synergistic effect of microspheres and dispersants, thus preparing PVC resin with less film.
It enables simple and easy preparation of PVC resin, with stable resin performance, less film, and uniform particle distribution, making it suitable for PVC soft products and chlorinated modified products. Furthermore, the microspheres are recyclable and reusable, reducing production costs.
Smart Images
Figure CN122167627A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of polymer chemical raw material technology, specifically relating to a method for preparing PVC resin using a low-film suspension method. Background Technology
[0002] Polyvinyl chloride (PVC), one of the five major general-purpose synthetic resins, possesses excellent flame retardancy, chemical resistance, electrical insulation, transparency, and physical and mechanical properties. It is widely used in industry, agriculture, construction, packaging, power cables, medical applications, and public utilities, among other fields. The PVC industry and related industries occupy an important position in the national economy. With the development of VCM polymerization technology and the refinement of PVC, downstream customers are placing higher demands on the quality and differentiation of PVC resins. PVC resins with little or no film are mainly used in flexible products and chlorinated modified PVC, and have promising market prospects.
[0003] Currently, the preparation technology of suspension PVC resin with low or no film thickness is achieved through dispersants, auxiliary dispersants, surfactants, porosity regulators, and the addition of other functional components. For example, the United States has issued several patents for manufacturing skinless or low-film porous PVC resin, such as US4711908, US4775701, US4775702, and US4742085. This technology is applied in vinyl chloride suspension polymerization systems, and the special dispersion system mainly consists of: (a) an unneutralized ion-sensitive dispersant that thickens the aqueous medium as the main dispersant; (b) polyvinyl alcohol with a certain degree of alcoholysis; when the VCM conversion rate is 1-5%, a sufficient amount of an ionic compound is added. This ionic compound desorbs the ion-sensitive main dispersant, which constitutes the majority of the dispersion system, from the surface of the VCM droplets to produce skinless or low-film, high-porosity PVC resin. This technology uses a relatively special type of dispersant, is complex to operate, and is difficult to control the granulation process, easily resulting in coarse material and bridging.
[0004] Chinese patents CN1927898, CN101717459, CN102453176, CN101466743, CN110724215, CN115449003, CN114478883, CN1117362497, etc., all aim to prepare PVC resin with low film thickness and high porosity based on different types of dispersants, dosages, timing of addition, surfactants, functional additives, stirring speeds, and distributed addition of monomers. They use chemical methods to mix the dispersant with the PVC resin, resulting in a relatively large amount of dispersant and an inability to separate the dispersant from the PVC resin.
[0005] Therefore, it is necessary to develop a method for preparing PVC resin using a low-film suspension process to solve the above problems. Summary of the Invention
[0006] This invention provides a method for preparing a suspension PVC resin with less film. The method employs physical isolation by adding non-polar microbeads or microbeads that are sparsely distributed with VCM monomers during the polymerization process. This isolation reduces the probability of aggregation during PVC particle formation, thereby preparing a suspension PVC resin with less film.
[0007] The technical solution of this invention is as follows:
[0008] A method for preparing PVC resin using the low-film suspension method includes the following steps:
[0009] 1) Coat the polymerization reactor with an anti-sticking agent;
[0010] 2) Add the following parts by weight of material to the polymerization reactor:
[0011] 120-150 parts water
[0012] Compound initiator 0.001-0.120 parts
[0013] Dispersant 0.001-0.050 parts
[0014] 40-60 portions of microbeads
[0015] 3) Stir to prevent the agitator from breaking the microspheres too quickly. After evacuating to a vacuum of less than -0.1 MPa, add 100 parts of vinyl chloride monomer.
[0016] 4) Continue stirring for 10-15 minutes, raise the temperature to 50-60℃, and the polymerization reaction will begin. After the pressure in the polymerization reactor drops to the process control point, add 0.001-0.300 parts of terminator.
[0017] 5) After stirring for 10-20 minutes, recover the monomer, unload the slurry, and sieve it. The slurry that passes through the sieve is then air-extracted, centrifuged, and dried at 90-110℃ for 1-2 hours to obtain suspension PVC resin with less film.
[0018] Preferably, the anti-sticking agent in step 1) is NOXOL WSW.
[0019] Preferably, the water mentioned in step 2) is deionized water with a conductivity of 1-5 μS / cm. Excessive conductivity will affect the sticking to the reactor, the stability of the polymerization system, the thermal stability of the resin, and other properties.
[0020] Preferably, the initiator in step 2) is an azo initiator and / or a peroxide initiator, and the amount of the compound initiator is preferably 0.020-0.050 parts by mass.
[0021] Preferably, the compound initiator is two or more of azobisisoheptanenitrile, bis-2-ethylhexyl peroxydicarbonate (EHP), tert-amyl peroxypentanoate (TAPP), and tert-butyl peroxyneodecanate (TBPND).
[0022] Preferably, the dispersant is a polyvinyl alcohol dispersant with a low degree of polymerization and a low degree of alcoholysis, with a degree of polymerization not exceeding 1000 and a degree of alcoholysis of 48%-55%. This type of dispersant can penetrate into the interior of vinyl chloride VCM monomer droplets, mainly playing the role of adjusting porosity and preventing explosive polymerization. The preferred amount of dispersant is 0.020-0.040 parts by weight.
[0023] Preferably, the microspheres are non-polar or made of materials repellent to vinyl chloride monomer. The melting point of the microspheres is greater than 100°C. If the melting point is too low, they will soften at the polymerization temperature and will not be able to provide a barrier function. The density of the microspheres is between 0.9 and 1.1 g / cm³. 3 The particle size is close to that of water and VCM mixtures. Too large or too small a particle size is not conducive to stirring and dispersion. The particle size is between 280-400μm. Small particle size is easy to pass through the screen and is not conducive to separation from PVC resin particles. Large particle size has poor dispersion and isolation effect.
[0024] Preferably, the terminator is one or more of bisphenol A, acetone thiourea and diethyl hydroxylamine. The terminator can terminate the polymerization reaction of vinyl chloride and improve the whiteness of the resin.
[0025] Preferably, in step 3), the stirring speed is started and gradually increased to 150 r / min, with the speed change rate per minute not exceeding 50 r / min.
[0026] Compared with the prior art, the present invention has the following advantages:
[0027] 1. The suspension method for preparing PVC resin of the present invention is simple and easy to implement, uses less dispersant, produces less film, has a wide range of adjustable resin particle porosity, produces a stable and easy polymerization reaction, and results in stable resin performance.
[0028] 2. The PVC resin prepared by this invention has a large absorption capacity and fast absorption rate of plasticizer, making it particularly suitable for the field of PVC soft products and chlorinated modified products.
[0029] 3. This invention uses non-polar or vinyl chloride monomer-repellent microspheres to act as an isolation between water and vinyl chloride, reducing the probability of agglomeration during PVC particle formation through physical methods, thereby reducing film formation. The microspheres and dispersant work synergistically; the dispersant can adjust the morphology of resin particles, and the microspheres can reduce aggregation and adjust the particle size distribution of resin particles. Together, they form PVC resin with less film and a suitable particle size distribution.
[0030] 4. The microbeads of the present invention can be separated from the PVC resin by filtration after the PVC resin is prepared, and can be recycled and reused, thereby reducing production costs.
[0031] 5. This invention uses a compound initiator to ensure the stability of the polymerization system. The compound initiator is two or more of the following: azobisisoheptanenitrile, bis-2-ethylhexyl peroxydicarbonate (EHP), tert-amyl peroxypentanoate (TAPP), and tert-butyl peroxyneodecanate (TBPND). By controlling the type and content of the initiator, the appropriate initiation rate is ensured, which is neither too fast nor too slow. Attached Figure Description
[0032] Figure 1 This is a scanning electron microscope image of the PVC resin prepared in Example 1 of the present invention.
[0033] Figure 2 This is a scanning electron microscope image of the PVC resin prepared in Comparative Example 3 of this invention. Detailed Implementation
[0034] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.
[0035] Unless otherwise specified, the deionized water used in the examples and comparative examples has a conductivity of 3 μS / cm.
[0036] The anti-sticking agent used is NOXOL WSW, purchased from CIRS, Italy.
[0037] The dispersant used is PVA55, purchased from Japan Synthetic Chemicals, with a degree of polymerization of 700-800 and a degree of alcoholysis of 52%.
[0038] The polypropylene microspheres have a melting point of 158℃ and a density of 0.98 g / cm³. 3
[0039] The polyamide microspheres have a melting point of 172℃ and a density of 1.06 g / cm³. 3
[0040] Example 1
[0041] A method for preparing PVC resin using the low-film suspension method includes the following steps:
[0042] 1) Clean and rinse the polymerization reactor thoroughly, and apply NOXOL WSW anti-sticking agent;
[0043] 2) Add the following parts by weight of material to the polymerization reactor:
[0044] 150 parts deionized water
[0045] Initiator EHP 0.020 parts
[0046] Initiator TAPP 0.030 parts
[0047] Dispersant PVA55 0.030 parts
[0048] 40 parts of 280μm polypropylene microbeads
[0049] 3) Slowly start the stirring speed, gradually increase the speed to 150 r / min, with a speed change rate of 50 r / min per minute, and add 100 parts by weight of vinyl chloride monomer after evacuating to -0.1 MPa;
[0050] 4) Continue stirring for 15 minutes, raise the temperature to 58°C, and the polymerization reaction will begin. When the pressure in the polymerization reactor drops to 0.30 MPa, add 0.020 parts by weight of the terminator diethylhydroxylamine.
[0051] 5) After continuing stirring for 20 minutes, recover the monomer, discharge the slurry, and pass it through a 60-mesh sieve. The slurry passing through the sieve is then air-extracted at 100°C, centrifuged, and dried for 2 hours to obtain a suspension PVC resin with a low film formation. The resin particle morphology is as follows: Figure 1 As shown, the resin particles have almost no film on their surface.
[0052] Example 2
[0053] Unlike Example 1, the amount of polypropylene microbeads added in this example is 50 parts by weight, while the remaining steps and parameters are the same as in Example 1.
[0054] Example 3
[0055] Unlike Example 1, the amount of polypropylene microbeads added in this example is 60 parts by weight, while the remaining steps and parameters are the same as in Example 1.
[0056] Example 4
[0057] Unlike Example 1, the polypropylene microspheres in this example have a particle size of 350 μm, while the remaining steps and parameters are the same as in Example 1.
[0058] Example 5
[0059] Unlike Example 1, the polypropylene microspheres in this example have a particle size of 400 μm, while the remaining steps and parameters are the same as in Example 1.
[0060] Example 6
[0061] Unlike Example 1, the microbeads in this example are polyamide with a particle size of 280 μm, and the remaining steps and parameters are the same as in Example 1.
[0062] Example 7
[0063] Unlike Example 1, the amount of dispersant PVA55 used in this example is 0.020 parts by weight, while the remaining steps and parameters are the same as in Example 1.
[0064] Example 8
[0065] Unlike Example 1, the amount of dispersant PVA55 used in this example is 0.080 parts by weight, while the remaining steps and parameters are the same as in Example 1.
[0066] Comparative Example 1
[0067] Unlike Example 1, the amount of polypropylene microspheres used in this comparative example is 30 parts by weight. The remaining steps and parameters are the same as in Example 1. The polymerization system is unstable and large particles are generated in the resin.
[0068] Comparative Example 2
[0069] Unlike Example 1, no microbeads were added in this comparative example. The remaining steps and parameters were the same as in Example 1. The polymerization system became unstable, and the experiment could not be carried out normally.
[0070] Comparative Example 3
[0071] Unlike Example 1, this comparative example did not include microspheres, but instead added 0.050 parts by weight of a high-polymerization-degree, high-hydrolysis-degree polyvinyl alcohol dispersant, PVA80, with a degree of hydrolysis of 78% and a degree of polymerization of 4000. The remaining preparation methods and steps were the same as in Example 1, the polymerization system was stable, and the morphology of the prepared resin was as follows. Figure 2 As shown, the resin particles are completely covered by a film.
[0072] The performance of the PVC resins obtained in the above examples and comparative examples was tested. Specifically, the plasticizer absorption was tested according to the method specified in national standard GB / T 3400-2002. The plasticizer absorption time was measured using a Brabender star mixer under the following conditions: temperature 90℃, rotation speed 100 r / min. 10g of organotin stabilizer was added to 500g of resin, stirred evenly, and then added to the mixer. After mixing for 5 minutes, 250g of plasticizer was added until the plasticizer was completely absorbed. The time from the addition of the plasticizer to its complete absorption was defined as the plasticizer absorption time. The surface film condition of the resin particles was tested according to the method specified in Q / SH 3160.R062-2007. The test results are shown in Table 1.
[0073] Table 1
[0074]
[0075]
[0076] The PVC resins prepared in Examples 1-8 of this invention exhibit high plasticizer absorption capacity and rapid absorption rate, making them particularly suitable for PVC soft products and chlorinated modified products. The PVC resin film coverage is minimal, and the particles are uniform. Furthermore, within an appropriate range, the greater the amount of polypropylene microspheres added, the greater the plasticizer absorption capacity and the shorter the plasticizer absorption time. Compared to Example 1, Comparative Example 1 showed a smaller amount of polypropylene microspheres added, resulting in an unstable polymerization system and the formation of larger particles in the resin. This was mainly due to the reduced amount of microspheres, which failed to create sufficient separation between the aqueous and oil phases, causing the PVC resin particles to aggregate. In Comparative Example 2, the absence of microspheres led to instability in the polymerization system, preventing the experiment from proceeding normally. In Comparative Example 3, the PVC resin was completely covered by a film, with no primary particles exposed, affecting the subsequent application of the PVC resin.
[0077] Although the present invention has been described in detail by way of preferred embodiments, it is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing PVC resin using the low-film suspension method, characterized in that, Includes the following steps: 1) Coat the polymerization reactor with an anti-sticking agent; 2) Add the following parts by weight of material to the polymerization reactor: 3) Stir, evacuate to a pressure less than -0.1 MPa, and then add 100 parts of vinyl chloride monomer; 4) Continue stirring and heat to 50-60℃. The polymerization reaction will begin. After the pressure in the polymerization reactor drops to the process control point, add 0.001-0.300 parts of terminator. 5) Continue stirring, recover the monomer, discharge the slurry, and sieve it. The slurry that passes through the sieve is then air-extracted, centrifuged, and dried at 90-110℃ for 1-2 hours to obtain suspension PVC resin with less film.
2. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, In step 4), continue stirring for 10-15 minutes, and in step 5), continue stirring for 10-20 minutes.
3. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, The water mentioned in step 2) is deionized water, and the conductivity of deionized water is 1-5 μS / cm.
4. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, In step 2), the compound initiator is an azo initiator and / or a peroxide initiator.
5. The method for preparing PVC resin using the low-film suspension method as described in claim 4, characterized in that, The compound initiator is two or more of the following: azobisisoheptanenitrile, bis-2-ethylhexyl peroxydicarbonate, tert-amyl peroxypentanoate, and tert-butyl peroxyneodecanate.
6. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, The dispersant is a polyvinyl alcohol dispersant with low degree of polymerization and low degree of alcoholysis, with a degree of polymerization not exceeding 1000 and a degree of alcoholysis of 48%-55%.
7. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, The microspheres are non-polar or made of materials repellent to vinyl chloride monomer, with a melting point greater than 100℃ and a density between 0.9 and 1.1 g / cm³. 3 The particle size is between 280-400μm.
8. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, The terminator is one or more of bisphenol A, acetone thiourea, and diethylhydroxylamine.
9. The method for preparing PVC resin using the low-film suspension method as described in claim 1, characterized in that, In step 3), start the stirring speed and gradually increase the speed to 150 r / min, with the speed change rate not exceeding 50 r / min per minute.