A method for producing a PVC resin

Abstract

The application provides a PVC resin production method and belongs to the technical field of high polymer material synthesis, solves the problems of performance limitation of traditional PVC resin, production formula and process bottleneck, and the PVC resin suitable for lithium battery pack and energy storage equipment is prepared through the synergistic effect of composite initiator, binary dispersion system, lead-free stabilizer and nano modification additive, combined with the optimization of segmented temperature control and stirring process, so that the product has the advantages of tensile strength of 55-60MPa, heat distortion temperature of greater than or equal to 90 DEG C, volume resistivity of greater than or equal to 1*10 13 Omega*cm, plasticizer absorption amount of 35-40g / 100g, and Congo red discoloration time of greater than or equal to 30min, solves the problems of insufficient mechanical property, poor insulation and environmental protection defects of traditional PVC resin, and meets the strict requirements of new energy field on high polymer materials.

Description

Technical Field

[0001] This invention belongs to the field of polymer material synthesis technology, specifically relating to a production method of high-performance PVC resin for lithium battery packs and energy storage devices, and further relating to a production method of high-performance PVC resin based on an improved calcium carbide-based vinyl chloride suspension polymerization process, which is suitable for scenarios with stringent requirements for mechanical properties, thermal stability and processing performance, such as lithium battery pack shells and insulating components of energy storage devices. Background Technology

[0002] Traditional PVC resins have performance limitations: General-purpose PVC resins produced by suspension polymerization of vinyl chloride using the calcium carbide method (such as SG-5) typically have a tensile strength of 45-50 MPa, an elongation at break of approximately 150%-200%, and a heat distortion temperature (HDT) of only 70-75℃. These limitations fail to meet the requirements of lithium battery pack casings for high temperature resistance (≥90℃) and high impact resistance (notched impact strength ≥15 kJ / m²). 2 The requirements are as follows: The insulating components of energy storage devices must have a PVC resin volume resistivity ≥ 1×10⁻⁶. 13 Ω·cm, while traditional craft products only have 1×10 11 -1×10 12 Ω·cm, insufficient insulation performance (data source: GB / T4615-2013 "General Test Methods for Polyvinyl Chloride Resin").

[0003] Formulation and process bottlenecks: Traditional suspension polymerization systems use composite lead salt stabilizers (3-5 wt%), resulting in large fluctuations in product chlorine content (56.5%-57.5%) and poor thermal stability (Congo red test paper color change time <15 min), failing to pass RoHS environmental certification in the lithium battery industry. Dispersion systems often use polyvinyl alcohol (PVA-1788) as a single dispersant, with resin particle porosity of only 0.15-0.20 cm⁻¹. 3 / g, plasticizer absorption ≤25g / 100g resin, which easily leads to poor plasticization problems during processing.

[0004] Although existing technologies modify copolymerization by adding methyl methacrylate (MMA), the conversion rate of the copolymerization reaction is only 60%-70%, and the production cost increases by about 20%. While organotin stabilizers can improve thermal stability, they are 3-5 times more expensive than traditional stabilizers, making large-scale application difficult. Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing PVC resin, so as to solve the problems of performance limitations of traditional PVC resin and bottlenecks in production formulation and process.

[0006] The technical solution of the present invention is: a method for producing PVC resin, wherein the PVC resin is produced in a calcium carbide method for vinyl chloride suspension polymerization, and the following formulation components are used: vinyl chloride monomer raw material, composite initiator, binary dispersion system, stabilizer and modifying agent; The composite initiator is a mixture of dicyclohexyl peroxide dicarbonate and azobisisobutyronitrile in a mass ratio of 2-3:1, and the total amount of the composite initiator is 0.04-0.08% of the monomer mass. The binary dispersion system is a mixture of polyvinyl alcohol and hydroxypropyl methylcellulose in a mass ratio of 2-3:1, and the total amount of the binary dispersant is 0.07-0.12% of the monomer mass. The stabilizer is a combination of calcium-zinc composite stabilizer and hydrotalcite, with a mass ratio of 3:1. The total amount of stabilizer is 2.0-3.0% of the mass of the monomers, and the molar ratio of calcium to zinc in the calcium-zinc composite stabilizer is 3:1. The modifying agents are glycidyl methacrylate and nano-montmorillonite, with glycidyl methacrylate accounting for 0.8-1.2% of the monomer mass and nano-montmorillonite accounting for 0.3-0.5% of the monomer mass. The polymerization system adopts a segmented temperature control process. The initial temperature of polymerization is 55±0.5℃, the middle temperature is 58±0.5℃, and the later temperature is 52±0.5℃. The pressure is controlled at ≤0.9MPa throughout the process. Stirring speed settings in the polymerization system: 100-120 rpm in the dispersion stage, 160-180 rpm in the polymerization stage, and 60-80 rpm in the discharge stage.

[0007] As a further improvement of the present invention, the mass ratio of dicyclohexyl peroxide dicarbonate to azobisisoheptanenitrile in the composite initiator is 2.5:1.

[0008] As a further improvement of the present invention, the polyvinyl alcohol in the binary dispersion system is PVA-1788 and the hydroxypropyl methylcellulose is HPMC-K4M, with a mass ratio of 2.2:1.

[0009] As a further improvement of the present invention, the interlayer spacing of the nano-montmorillonite is ≥2.5nm, and it is pretreated with a silane coupling agent for a pretreatment time of ≥2h.

[0010] As a further improvement of the present invention, the polymerization time in the initial stage is 0-1h, the pressure is 0.8-0.9MPa, and the initiator decomposition rate is 40%-50%; the polymerization time in the middle stage is 1-3h, the pressure is 0.6-0.7MPa, and the monomer conversion rate is above 85%; the polymerization time in the later stage is 3-4h, the pressure is <0.3MPa, and the residual VCM content is ≤10ppm after vacuum removal.

[0011] As a further improvement of the present invention, the stirring speed in the polymerization system is 0-0.5h, the dispersion stage duration is 0-0.5h, the average particle size of the dispersed droplets is 100-150μm, the polymerization stage duration is 0.5-3.5h, and the discharge stage duration is 3.5-4h.

[0012] The beneficial effects of this invention are as follows: This invention prepares PVC resin with high mechanical properties, high insulation, and high processing stability by optimizing the formulation of the suspension polymerization system and controlling the process parameters.

[0013] The specific advantages of the process of this invention compared with traditional methods are as follows: 1. Significantly improved mechanical properties: Tensile strength increased from 45-50MPa in traditional processes to 55-60MPa, and elongation at break reached 220-250%, meeting the impact resistance requirements of lithium battery pack casings (notched impact strength ≥15kJ / m). 2 ).

[0014] 2. Optimized thermal stability: The Congo red color change time has been extended from <15min to 30-35min, and the heat distortion temperature has been increased to 90-95℃, which can withstand the maximum ambient temperature of 85℃ during the charging and discharging of lithium batteries.

[0015] 3. Breakthrough in insulation performance: Volume resistivity increased from 1×10⁻⁶ 11 -1×10 12 Ω·cm increased to 5×10 12 -1×10 13 Ω·cm, dielectric constant ≤3.5, conforming to the standard for insulating components of energy storage equipment (GB / T1408.1-2016).

[0016] 4. Improved processing performance: The amount of plasticizer absorbed is increased from ≤25g / 100g resin to 35-40g / 100g, the plasticizing time is shortened by 20%-30%, and the processing energy consumption is reduced by about 15%.

[0017] 5. Environmental compliance: The lead-free stabilizer system enables the product to comply with RoHS 2.0 (EU2015 / 863) and GB / T2423.38-2021 standards, and the heavy metal content (Pb, Cd) is <10ppm. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to specific embodiments.

[0019] The specific implementation of the process of this invention adopts the following component ratio as shown in Table 1.

[0020] Example 1 This embodiment uses the production of PVC resin for lithium battery pack casings as an example for illustration.

[0021] 1. Formula (parts by weight) 100 parts of vinyl chloride VCM, composite initiator (DCPD 0.05 + ADHN 0.015), binary dispersion system (PVA-1788 0.06 + HPMC-K4M 0.03), calcium-zinc stabilizer 1.8 + hydrotalcite 0.8, and modifying agent (GMA 1.0 + nano MMT 0.4).

[0022] 2. Process parameters Polymerization temperature: Initial stage 55℃ (1h), pressure 0.8MPa, initiator decomposition rate 45% → Intermediate stage 58℃ (2.5h), pressure 0.6MPa, monomer conversion rate 86% → Late stage 52℃ (0.5h), pressure 0.2MPa, residual VCM content removed by vacuum is 10ppm.

[0023] Stirring speed: 120 rpm (0-0.5h) for dispersion stage, with an average droplet size of 100μm → 180 rpm (0.5-3.5h) for polymerization stage → 80 rpm (3.5-4h) for discharge stage.

[0024] The performance test results of the manufactured products in this embodiment are shown in Table 2.

[0025] Example 2 This embodiment uses the production of PVC resin for insulating components of energy storage devices as an example for illustration.

[0026] 1. Formula (parts by weight) 100 parts of vinyl chloride VCM, composite initiator (DCPD 0.04 + ADHN 0.01), binary dispersion system (PVA-1788 0.05 + HPMC-K4M 0.025), calcium-zinc stabilizer 1.6 + hydrotalcite 0.6, and modifying agent (GMA 0.9 + nano MMT 0.35).

[0027] 2. Process parameters Polymerization temperature: Initial stage 55℃ (1.2h), pressure 0.9MPa, initiator decomposition rate 48% → Intermediate stage 58℃ (2.3h), pressure 0.7MPa, monomer conversion rate 88% → Late stage 52℃ (0.5h), pressure 0.2MPa, residual VCM content removed by vacuum is 9ppm.

[0028] Stirring speed: 120 rpm (0.3 h) for dispersion stage, with an average droplet size of 120 μm → 180 rpm (3.4 h) for polymerization stage → 80 rpm (3.4 h) for discharge stage.

[0029] The performance test results of the manufactured products in this embodiment are shown in Table 3.

[0030] Comparative Example 1 This comparative example represents the production process steps of a traditional process product, and its component formulation (parts by mass) is shown in Table 4.

[0031] The indicators of the products produced in this comparative example are shown in Table 5.

[0032] As can be seen from the comparison of Tables 1-5, in the process of this invention, the composite initiator adopts the synergistic effect of two initiators, shortening the polymerization induction period (from 45 min to 25-30 min) and increasing the conversion rate to over 95%; the binary dispersion system optimizes the particle morphology, increasing the porosity to 0.25-0.30 cm³ / g, and the plasticizer absorption reaches 35-40 g / 100 g; the stabilizer is a lead-free formula, with a chlorine content stable at 56.8%-57.2%, and the Congo red color change time is ≥30 min, which meets the RoHS standard; in the modified additives, GMA grafting increases the crosslinking density, and MMT intercalation enhances the mechanical properties and insulation.

[0033] The stirring intensity in the polymerization system is optimized by adopting a three-stage stirring speed of "low-high-low". During the dispersion stage, the droplets are ensured to be evenly dispersed (average particle size 100-150μm); during the polymerization stage, mass and heat transfer are enhanced; and during the discharge stage, particle breakage is reduced.

Claims

1. A method for producing PVC resin, characterized in that: The PVC resin is produced in a calcium carbide-based vinyl chloride suspension polymerization system, using the following formulation components: vinyl chloride monomer raw material, composite initiator, binary dispersion system, stabilizer, and modifying additives; The composite initiator is a mixture of dicyclohexyl peroxide dicarbonate and azobisisobutyronitrile in a mass ratio of 2-3:1, and the total amount of the composite initiator is 0.04-0.08% of the monomer mass. The binary dispersion system is a mixture of polyvinyl alcohol and hydroxypropyl methylcellulose in a mass ratio of 2-3:1, and the total amount of the binary dispersant is 0.07-0.12% of the monomer mass. The stabilizer is a combination of calcium-zinc composite stabilizer and hydrotalcite, with a mass ratio of 3:

1. The total amount of stabilizer is 2.0-3.0% of the mass of the monomers, and the molar ratio of calcium to zinc in the calcium-zinc composite stabilizer is 3:

1. The modifying agents are glycidyl methacrylate and nano-montmorillonite, with glycidyl methacrylate accounting for 0.8-1.2% of the monomer mass and nano-montmorillonite accounting for 0.3-0.5% of the monomer mass. The polymerization system adopts a segmented temperature control process. The initial temperature of polymerization is 55±0.5℃, the middle temperature is 58±0.5℃, and the later temperature is 52±0.5℃. The pressure is controlled at ≤0.9MPa throughout the process. Stirring speed settings in the polymerization system: 100-120 rpm in the dispersion stage, 160-180 rpm in the polymerization stage, and 60-80 rpm in the discharge stage.

2. The method for producing PVC resin according to claim 1, characterized in that: The mass ratio of dicyclohexyl peroxide dicarbonate to azobisisobutyronitrile in the composite initiator is 2.5:

1.

3. The method for producing PVC resin according to claim 1, characterized in that: In the binary dispersion system, the polyvinyl alcohol is PVA-1788 and the hydroxypropyl methylcellulose is HPMC-K4M, with a mass ratio of 2.2:

1.

4. A method for producing PVC resin according to claim 1, characterized in that: The interlayer spacing of the nano-montmorillonite is ≥2.5nm, and it is pretreated with a silane coupling agent for ≥2h.

5. A method for producing PVC resin according to claim 1, characterized in that: The polymerization process is as follows: initial polymerization duration is 0-1 h, pressure is 0.8-0.9 MPa, and initiator decomposition rate is 40%-50%; middle polymerization duration is 1-3 h, pressure is 0.6-0.7 MPa, and monomer conversion rate is above 85%; late polymerization duration is 3-4 h, pressure is <0.3 MPa, and residual VCM content is ≤10 ppm after vacuum removal.

6. A method for producing PVC resin according to claim 1, characterized in that: The stirring speed in the polymerization system is 0-0.5 h, the dispersion stage duration is 0-0.5 h, and the average particle size of the dispersed droplets is 100-150 μm. The polymerization stage lasts 0.5-3.5 hours; the discharge stage lasts 3.5-4 hours.

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