Solvent-resistant non-migration PVC (polyvinyl chloride) adhesive and preparation method thereof

Abstract

The invention discloses a solvent-resistant non-migration PVC (polyvinyl chloride) adhesive and a preparation method thereof, and belongs to the field of PVC materials. The PVC glue comprises PVC resin, an adipate polyester plasticizer, a calcium-zinc stabilizer and a functional aid, the adipate polyester plasticizer limits specific viscosity and acid value, the calcium-zinc stabilizer and the functional aid are compounded in a specific proportion, and the PVC resin is prepared through specific raw materials and a specific process. The preparation method comprises the following steps: heating, stirring at a high speed, plasticizing for the first time, filtering, plasticizing for the second time, multi-roller gradient calendering and cooling to obtain a finished product. By optimizing the component proportion and the preparation process, zero migration of the plasticizer is achieved, the tolerance to various organic solvents is remarkably improved, and meanwhile the plasticizer has good mechanical property and thermal stability and is suitable for medical treatment, laboratories, chemical engineering and other multi-solvent contact scenes.

Description

Technical Field

[0001] This invention relates to the field of PVC materials, and in particular to a solvent-resistant, non-migratory PVC adhesive and its preparation method. Background Technology

[0002] PVC adhesives are widely used in various fields such as medical, laboratory, and chemical industries for countertop installation and equipment encapsulation due to their good bonding strength, processability, and cost advantages. However, in these applications, PVC adhesives often come into contact with a variety of solvents, including not only alcohol commonly used for hospital disinfection, but also various organic solvents such as isopropanol, acetone, ethyl acetate, butanone, and methanol.

[0003] In existing technologies, common PVC adhesives generally use traditional plasticizers such as phthalates. These plasticizers have poor compatibility with PVC resin and are prone to migrating and precipitating from the PVC system during long-term use. However, the migration of plasticizers leads to voids and defects in the internal structure of the PVC adhesive, significantly deteriorating its mechanical properties, manifesting as decreased bonding strength, loss of flexibility, and brittleness. Furthermore, the micropores formed by migration become channels for solvent molecules to penetrate, accelerating the erosion of the PVC adhesive by solvents, causing the adhesive layer to swell, dissolve, delaminate, or even detach, affecting its stability and service life. For example, acetone, frequently encountered on laboratory countertops, can interact with the migrated defects in the PVC adhesive, rapidly destroying the integrity of the adhesive layer.

[0004] Furthermore, the solvent resistance of traditional PVC adhesives deteriorates further in complex scenarios involving alternating contact with various solvents, and plasticizer migration may also pose environmental safety hazards. Therefore, there is an urgent need to develop a PVC adhesive that can inhibit plasticizer migration by optimizing the plasticizer system and its supporting components, while also exhibiting excellent resistance to a variety of organic solvents. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a solvent-resistant, non-migrating PVC adhesive and its preparation method, aiming to solve the problems of easy migration of plasticizers and poor solvent resistance in existing PVC adhesives.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A solvent-resistant, non-migratory PVC adhesive comprises the following components by weight: 100 parts PVC resin, 50-60 parts adipate polyester plasticizer, 3-5 parts calcium-zinc stabilizer, and 2-4 parts functional additives; wherein the adipate polyester plasticizer has a viscosity of 2300-3500 cps at 25°C and an acid value ≤1 KOH mg / g.

[0007] The solvent-resistant, non-migratory PVC adhesive wherein the adipate polyester plasticizer has a viscosity of 2800 cps at 25°C and an acid value ≤0.5 KOH mg / g.

[0008] The solvent-resistant, non-migratory PVC adhesive, wherein the mass ratio of calcium salt to zinc salt in the calcium-zinc stabilizer is (2-3):1.

[0009] The solvent-resistant, non-migratory PVC adhesive, wherein the functional additives are butyl stearate and phenolic antioxidants; the mass ratio of butyl stearate to phenolic antioxidants is (2-3):1.

[0010] The solvent-resistant, non-migratory PVC adhesive wherein the degree of polymerization of the PVC resin is 1800–2200 and the K value is 75–82.

[0011] The solvent-resistant, non-migratory PVC adhesive, wherein the raw materials for preparing the PVC resin include the following components by mass: 100 parts vinyl chloride monomer, 150-180 parts deionized water, 0.1-0.2 parts particle modifier, 0.8-1.2 parts composite emulsifier, 0.05-0.08 parts oil-soluble initiator, 0.03-0.05 parts chain transfer agent, and 0.1-0.2 parts pH adjuster.

[0012] The solvent-resistant, non-migratory PVC adhesive, wherein the composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of (2-3):1.

[0013] The solvent-resistant, non-migratory PVC adhesive, wherein the particle modifier is calcium stearate; the oil-soluble initiator is di(2-ethylhexyl) peroxide dicarbonate; the chain transfer agent is dodecyl mercaptan; and the pH adjuster is an aqueous solution of sodium bicarbonate.

[0014] A method for preparing a solvent-resistant, non-migratory PVC adhesive includes the following steps: thoroughly stirring the raw materials and then performing a primary plasticizing process; filtering the primary plasticized material and then performing a secondary plasticizing process; calendering and cooling the secondary plasticized material to obtain the aforementioned solvent-resistant, non-migratory PVC adhesive.

[0015] The method for preparing the solvent-resistant, non-migratory PVC adhesive includes: stirring the raw materials at a temperature of 100–110°C and a rotation speed of 1200–1500 r / min for 360–400 s; primary plasticizing at a temperature of 210–220°C for 300–320 s; secondary plasticizing at a temperature of 190–200°C for 300–320 s; and employing a multi-roll calendering process, wherein the temperatures of the first roll are 220°C, the second roll is 220°C, the third roll is 210°C, the fourth roll is 210°C, the fifth roll is 200°C, the sixth roll is 185–190°C, and the calendering speed is 1.5–2.0 m / min.

[0016] Beneficial effects: This invention provides a solvent-resistant, non-migrating PVC adhesive and its preparation method. The selected adipate polyester plasticizer possesses excellent non-migrating and compatibility properties, forming a stable binding system with PVC resin. This fundamentally inhibits plasticizer migration, avoiding structural defects caused by migration in traditional PVC adhesives. The combination of calcium-zinc stabilizers and functional additives plays a synergistic stabilizing and dispersion-optimizing role, effectively inhibiting resin degradation, improving the uniformity of component mixing, and further enhancing the density of the adhesive layer structure, reducing the channels for solvent molecule penetration, and improving the product's resistance to organic solvents. Simultaneously, the PVC resin preparation process, combined with subsequent heating and stirring, secondary plasticizing, and multi-roll gradient calendering processes, ensures deep integration and uniform dispersion of the components, while also improving the density and molding stability of the adhesive layer, resulting in a product with both good mechanical strength and flexibility. Detailed Implementation

[0017] This invention provides a solvent-resistant, non-migratory PVC adhesive and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the following embodiments are provided to further illustrate the invention in detail. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the scope of protection of the invention.

[0018] This invention provides a solvent-resistant, non-migratory PVC adhesive, comprising the following components by weight: 100 parts PVC resin, 50-60 parts adipate polyester plasticizer, 3-5 parts calcium-zinc stabilizer, and 2-4 parts functional additives; wherein the adipate polyester plasticizer has a viscosity of 2300-3500 cps at 25°C and an acid value ≤1 KOH mg / g.

[0019] Adipate polyester plasticizer is added at a ratio of 50-60 parts. This dosage not only fully utilizes its excellent plasticizing effect, improving the flexibility and processing flow of PVC resin, but also avoids the migration risk caused by improper dosage of traditional plasticizers due to its good compatibility with PVC resin. Furthermore, its viscosity range of 2300-3500 cps and acid value of ≤1 KOH mg / g further enhance the binding stability with the resin system, inhibiting the formation of micropores and reducing solvent penetration channels. Calcium-zinc stabilizer is added at a ratio of 3-5 parts. This ratio effectively inhibits the thermal degradation of PVC resin during processing and use, preventing structural defects caused by degradation from affecting solvent resistance and non-migration properties. Simultaneously, it works synergistically with the adipate polyester plasticizer to improve the overall stability of the system and extend product service life. Functional additives are added at a dosage of 2 to 4 parts to optimize the dispersion uniformity of each component during processing, avoid performance fluctuations caused by local agglomeration, enhance the anti-aging ability and interfacial bonding of the adhesive layer, further improve the adhesive layer's resistance to various organic solvents, and ensure the stability of use in complex solvent contact scenarios.

[0020] Preferably, the adipate polyester plasticizer has a viscosity of 2800 cps at 25°C, an acid value ≤0.5 KOH mg / g, an APHA of 60, and a relative density of 1.06 g / cm³ at 25 / 25°C. 3 The refractive index is 1.464, the freezing point is -22℃, and the migration resistance is 1.8%. Specifically, the adipate polyester plasticizer selected is GLOBINEX W-8000. Its viscosity of 2800cps provides excellent compatibility with PVC resin, ensuring uniform dispersion and fusion of components during processing and tight bonding with the resin skeleton after molding, reducing interfacial voids. A low acid value of ≤0.5 KOH mg / g effectively reduces the risk of hydrolysis, preventing resin degradation or impact on the plasticizer due to excessively high acid values, thus improving the long-term stability of the product. Color ensures the clean appearance of the finished PVC adhesive. The relative density closely matches the density of PVC resin, further optimizing system compatibility and reducing the risk of delamination. The refractive index is similar to the refractive characteristics of PVC resin, preventing optical defects in the adhesive layer and helping to improve the bonding force between components. The low freezing point of -22℃ ensures that the PVC adhesive maintains good flexibility in low-temperature environments, expanding its application range. Its 1.8% migration resistance index further highlights its main advantage, far superior to traditional plasticizers, and it can remain stably in the PVC system for a long time.

[0021] In some embodiments, the mass ratio of calcium salt to zinc salt in the calcium-zinc stabilizer is (2-3):1. Calcium salt exhibits excellent long-term thermal stability, continuously inhibiting resin thermal degradation during PVC processing and use, and reducing the damage to the system structure caused by HCl precipitation. Zinc salt, on the other hand, demonstrates highly efficient initial thermal stabilization, quickly responding to the high-temperature environment at the initial stage of processing and preventing drastic resin degradation in a short period. This combination of the two compensates for the deficiencies of insufficient initial stability of calcium salt and the lack of long-term stability of zinc salt alone. Furthermore, the calcium-zinc composite system at this ratio shows better compatibility with PV resin, adipate polyester plasticizer, and functional additives, without affecting the dispersion uniformity of each component or causing additional migration risks.

[0022] In some embodiments, the functional additives are butyl stearate and phenolic antioxidants; the mass ratio of butyl stearate to phenolic antioxidants is (2-3):1. Butyl stearate, as a highly efficient lubricant, can reduce frictional resistance between components, promote the uniform dispersion of PVC resin, adipate polyester plasticizer, and calcium-zinc stabilizer, avoid structural defects caused by local agglomeration, and reduce adhesion between processing equipment and materials, improving molding smoothness. Its good compatibility with the system components can also help improve the flexibility of the adhesive layer and avoid brittleness. Phenolic antioxidants (such as 1010 and 1076) can capture free radicals generated by oxidation in the system, inhibit the oxidative degradation of PVC resin and plasticizer, and delay the aging of the adhesive layer. Especially in long-term use or complex environments, it can effectively maintain the stability of the mechanical properties and solvent resistance of the adhesive layer. When the two are combined in this ratio, the lubricating and dispersing effect of butyl stearate creates a uniform system environment for the antioxidant to exert its effect, while the anti-aging properties of the antioxidant extend the effect time of butyl stearate, forming a synergistic effect and further enhancing the structural integrity and service durability of PVC adhesive.

[0023] In some embodiments, the PVC resin has a degree of polymerization of 1800–2200 and a K value of 75–82. The resin molecular chain length at this degree of polymerization is moderate; it avoids the problems of a brittle and insufficiently strong adhesive layer due to excessively short chains, and poor processing fluidity and compatibility with plasticizers due to excessively long chains. This ensures the mechanical strength of the adhesive layer while allowing for thorough integration with the adipate polyester plasticizer, forming a dense system. The aforementioned K value range reflects the molecular weight distribution and solubility of the resin. Resins within this range exhibit stronger interfacial bonding with plasticizers, calcium-zinc stabilizers, and functional additives, reducing compatibility defects between components, preventing localized voids, and optimizing the melt plasticizing effect during processing, resulting in a more uniform structure after the adhesive layer is formed.

[0024] In some embodiments, the raw materials for preparing the PVC resin include: 100 parts of vinyl chloride monomer (VCM), 150-180 parts of deionized water, 0.1-0.2 parts of particle modifier (calcium stearate), 0.8-1.2 parts of composite emulsifier (the composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of (2-3):1), 0.05-0.08 parts of oil-soluble initiator (di(2-ethylhexyl) peroxide dicarbonate EHP), 0.03-0.05 parts of chain transfer agent (dodecyl mercaptan), and 0.1-0.2 parts of pH adjuster (sodium bicarbonate aqueous solution).

[0025] Vinyl chloride monomer serves as the polymerization base material. Combined with deionized water, the water-to-oil ratio is controlled to provide a stable system for the polymerization reaction, preventing particle agglomeration due to insufficient water or efficiency reduction due to excessive water. Calcium stearate refines resin particles through steric hindrance, reducing agglomeration and ensuring compatibility with plasticizers, resulting in a more uniform material structure. The compounded emulsifier stabilizes vinyl chloride droplets, improves dispersion, and facilitates the formation of fine-particle-size emulsions. EHP is used to regulate the polymerization rate and prevent excessive reaction and byproduct generation. Dodecyl mercaptan stabilizes the degree of polymerization and K-value of the resin. Sodium bicarbonate aqueous solution maintains a suitable pH in the system. All raw materials work synergistically to prepare a high-performance PVC resin with a suitable system.

[0026] The preparation of PVC resin using a micro-suspension polymerization process includes the following steps: Pre-emulsification: Add demineralized water and composite emulsifier to the pre-emulsification tank, start stirring at 700-800 rpm, and heat to 40-45°C (to improve emulsification efficiency). Stir for 10 minutes until the emulsifier is completely dissolved. While stirring, slowly add calcium stearate and stir for 5 minutes to ensure the particle modifier is evenly dispersed in the aqueous phase. Then add vinyl chloride monomer, initiator, and chain transfer agent at a feeding rate of 5-8 parts / min (to avoid local overfeeding that could lead to droplet aggregation). The feeding process should continue for 20-30 minutes. Turn on the high-shear homogenizer inside the tank at 10,000-12,000 rpm and homogenize for 15-20 minutes, maintaining the system temperature at 40-45°C during this period using jacket temperature control. During homogenization, samples were taken every 5 minutes, and droplet size was measured using a laser particle size analyzer until D50 stabilized at 0.8–1.2 μm and D90 ≤ 1.8 μm. If the particle size was too large, the homogenization time was extended by 2–3 minutes; if it was too small, the homogenization speed was reduced by 500 r / min. Sodium bicarbonate aqueous solution was added to adjust the pH of the preemulsion to 6.0–7.0 (too low a pH can lead to rapid decomposition of the initiator, while too high a pH can affect resin stability). After stirring for 5 minutes, the homogenizer was turned off to obtain a homogeneous vinyl chloride preemulsion.

[0027] Polymerization reaction: Pump the pre-emulsion into the polymerization reactor (equipped with a stirrer, jacket, and reflux condenser), close the feed valve, and introduce high-purity nitrogen into the reactor for purging three times (each time at a nitrogen pressure of 0.2 MPa, held for 5 minutes) to remove oxygen from the reactor. Heating initiation (first stage): Start the jacketed hot water circulation and heat to 50–52°C at a rate of 1.5–2°C / min, while simultaneously starting the stirrer (250–300 r / min). At this point, the initiator EHP begins to decompose, and the polymerization reaction starts. Isothermal polymerization (second stage): When the pressure inside the reactor reaches its peak and begins to decrease (after approximately 30–40 minutes), it indicates that VCM has partially converted. Maintain the temperature at 50–52°C and the stirring speed at 250 r / min to enter the isothermal polymerization stage, which lasts for 2–2.5 hours. Samples are taken every 30 minutes to test the polymerization conversion rate (gravimetric method: after sampling, dry to constant weight and calculate the solid content). When the conversion rate reaches 70%–75%, the heating stage begins. Third stage of increasing conversion rate by heating: Increase the temperature to 55-58℃ at a rate of 1℃ / min, increase the stirring speed to 300r / min, and continue for 1-1.5h. When the pressure inside the reactor drops to 0.3-0.4MPa and the conversion rate reaches 90%-95%, stop heating and the polymerization reaction ends.

[0028] Post-treatment: Removal of residual VCM, unreacted emulsifiers, and byproducts. The polymerized latex solution is fed into a high-speed centrifuge (8000–10000 r / min) to separate the PVC latex particles (solid phase) from the aqueous phase (containing unreacted emulsifier and byproducts) for 15–20 min. The solid latex particles are collected and washed three times with deionized water (each time using 1.5 times the mass of the latex particles) to remove residual emulsifier. The washed latex particles are then fed into a spray drying tower, with the inlet temperature controlled at 160–170℃ and the outlet temperature at 70–75℃, for 15–20 s. The moisture content of the dried resin should be ≤0.3%. If the moisture content is too high, the inlet temperature should be increased by 5–10℃. The dried resin is then passed through a 100-mesh sieve (to remove a small amount of agglomerated particles) to obtain the finished PVC resin.

[0029] This invention also provides a method for preparing a solvent-resistant, non-migratory PVC adhesive, comprising the following steps: The raw materials are stirred at a temperature of 100-110℃ and a high speed of 1200-1500r / min for 360-400s. By controlling the temperature, the viscosity of each raw material is reduced, the aggregation state of PVC resin particles is broken, and the raw materials are quickly fused together.

[0030] The raw material is then fed into a screw extruder for primary plasticization. The extruder barrel temperature is set to 210–220°C, the screw speed to 30–40 r / min, and the plasticization time to 300–320 s. This step allows the premixed raw material to fully melt, disrupting the crystalline structure of the PVC resin and enabling plasticizers, stabilizers, and other components to deeply integrate with the resin molecular chains, initially forming a uniform molten system. This is crucial for achieving interfacial fusion of the components and avoids the residue of unmelted resin particles.

[0031] The material after primary plasticization is filtered through a 250-mesh filter to remove impurities and incompletely melted particles. The raw material is then fed into a screw extruder, with the barrel temperature set at 190–200°C and the screw speed at 20–25 r / min. Secondary plasticization lasts 300–320 seconds. The secondary plasticization temperature is slightly lower than the primary plasticization temperature. This avoids over-plasticization leading to resin degradation, compensates for potential uneven plasticization issues from the primary process, and allows for thorough maturation of the molten material through lower speed and temperature, further improving the system's compatibility and structural density.

[0032] The material after secondary plasticization is calendered using gradient calendering: the temperature of the first roll is 220℃, the second roll is 220℃, the third roll is 210℃, the fourth roll is 210℃, the fifth roll is 200℃, and the sixth roll is 185-190℃, with a calendering speed of 1.5-2.0 m / min. After cooling, a solvent-resistant, non-migratory PVC adhesive is obtained. Gradient cooling maintains the material in a molten state through the high temperature of the first two rolls, ensuring the material's fluidity and ductility during calendering. The gradual cooling of subsequent rolls achieves stable cooling and shaping, avoiding stress concentration, cracking, or shrinkage deformation in the adhesive layer caused by sudden cooling. Simultaneously, gradient calendering further compacts the material, eliminating residual air bubbles and pores, and improving the density and surface smoothness of the adhesive layer.

[0033] To further illustrate the present invention In summary, the present invention provides the following embodiments through a solvent-resistant, non-migratory PVC adhesive and its preparation method.

[0034] Example 1 A solvent-resistant, non-migratory PVC adhesive is composed of the following components in parts by weight: 100 parts of PVC resin (degree of polymerization 2000, K value 78), 50 parts of adipate polyester plasticizer (GLOBINEX W-8000), 3 parts of calcium zinc stabilizer (3:1), and 3 parts of functional additives (the mass ratio of butyl ester and phenolic antioxidant 1010 is 2.5:1).

[0035] The raw materials for preparing the PVC resin include: 100 parts of vinyl chloride monomer, 180 parts of deionized water, 0.1 parts of particle modifier (calcium stearate), 1.2 parts of composite emulsifier (the composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of 3:1), 0.07 parts of oil-soluble initiator (di(2-ethylhexyl) peroxide dicarbonate EHP), 0.03 parts of chain transfer agent (dodecyl mercaptan), and 0.2 parts of pH adjuster (sodium bicarbonate aqueous solution).

[0036] A method for preparing a solvent-resistant, non-migratory PVC adhesive includes the following steps: The raw material is stirred at 105°C and a high rotation speed of 1300 r / min for 360 s. Then, it is fed into a screw extruder for primary plasticization at 210°C and 35 r / min for 310 s. The material after primary plasticization is filtered through a 250-mesh filter, and then fed back into the screw extruder at 190°C and 25 r / min for secondary plasticization for 310 s. Gradient calendering is employed: the temperatures of the first roll are 220°C, the second roll is 220°C, the third roll is 210°C, the fourth roll is 210°C, the fifth roll is 200°C, and the sixth roll is 190°C, with a calendering speed of 1.5 m / min.

[0037] Example 2 A solvent-resistant, non-migratory PVC adhesive is composed of the following components in parts by weight: 100 parts of PVC resin (degree of polymerization 1800, K value 75), 55 parts of adipate polyester plasticizer (GLOBINEX W-8000), 4 parts of calcium-zinc stabilizer (2:1), and 3 parts of functional additives (the mass ratio of butyl ester and phenolic antioxidant 1010 is 3:1).

[0038] The raw materials for preparing the PVC resin include: 100 parts vinyl chloride monomer, 160 parts deionized water, 0.1 parts particle modifier (calcium stearate), 0.8 parts composite emulsifier (the composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of 2.5:1), 0.08 parts oil-soluble initiator (di(2-ethylhexyl) peroxide dicarbonate EHP), 0.05 parts chain transfer agent (dodecyl mercaptan), and 0.1 parts pH adjuster (sodium bicarbonate aqueous solution).

[0039] A method for preparing a solvent-resistant, non-migratory PVC adhesive includes the following steps: The raw material is stirred at 110°C and a high rotation speed of 1500 r / min for 360 s. Then, it is fed into a screw extruder for primary plasticization at 210°C and 35 r / min for 320 s. The material after primary plasticization is filtered through a 250-mesh filter, and then fed back into the screw extruder at a set temperature of 195°C and a rotation speed of 25 r / min for secondary plasticization for 300 s. Gradient calendering is used: the temperatures of the first roll are 220°C, the second roll is 220°C, the third roll is 210°C, the fourth roll is 210°C, the fifth roll is 200°C, and the sixth roll is 190°C, with a calendering speed of 1.5 m / min.

[0040] Example 3 A solvent-resistant, non-migratory PVC adhesive is composed of the following components in parts by weight: 100 parts of PVC resin (degree of polymerization 2200, K value 82), 60 parts of adipate polyester plasticizer (GLOBINEX W-8000), 5 parts of calcium-zinc stabilizer (2.5:1), and 4 parts of functional additives (the mass ratio of butyl ester and phenolic antioxidant 1010 is 2:1).

[0041] The raw materials for preparing the PVC resin include: 100 parts of vinyl chloride monomer, 170 parts of deionized water, 0.2 parts of particle modifier (calcium stearate), 1 part of composite emulsifier (the composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of 2:1), 0.05 parts of oil-soluble initiator (di(2-ethylhexyl) peroxide dicarbonate EHP), 0.04 parts of chain transfer agent (dodecyl mercaptan), and 0.1 parts of pH adjuster (sodium bicarbonate aqueous solution).

[0042] A method for preparing a solvent-resistant, non-migratory PVC adhesive includes the following steps: The raw material is stirred at 100°C and a high rotation speed of 1200 r / min for 400 s. Then, it is fed into a screw extruder for primary plasticization at 220°C and 35 r / min for 300 s. The material after primary plasticization is filtered through a 250-mesh filter, and then fed back into the screw extruder at 200°C and 25 r / min for secondary plasticization for 300 s. Gradient calendering is employed: the temperatures of the first roll are 220°C, the second roll is 220°C, the third roll is 210°C, the fourth roll is 210°C, the fifth roll is 200°C, and the sixth roll is 190°C, with a calendering speed of 1.5 m / min.

[0043] Comparative Example 1: The plasticizer used was a traditional phthalate plasticizer, and the rest was the same as in Example 1.

[0044] Comparative Example 2: A barium-zinc stabilizer was used instead of the calcium-zinc stabilizer in Example 1. Everything else was the same as in Example 1.

[0045] Comparative Example 3: Only the first plasticization was performed, and the rest was the same as in Example 1.

[0046] Performance testing: 1. Plasticizer migration: Tested according to GB / T 23296.26-2009.

[0047] 2. Solvent resistance: 50% ethanol, acetone and ethyl acetate were selected as test solvents respectively. According to GB / T11547-2008, the samples were soaked for a specified time, and the appearance changes were observed and the adhesion strength retention rate was tested.

[0048] 3. Mechanical properties: Tensile strength and elongation at break shall be tested in accordance with GB / T 1040.3-2006.

[0049] 4. Thermal stability: The thermal stability time (200℃) was tested using the Congo red test paper method, referring to GB / T 2917.1-2017.

[0050]

[0051] Results analysis: No plasticizer migration was detected in this embodiment. The selected adipate polyester plasticizer is non-migratory and forms a stable, compatible system with PVC resins of specific parameters. It exhibits excellent solvent resistance, maintaining no change in appearance after prolonged immersion in various common solvents. It possesses excellent mechanical properties, combining high strength with good flexibility. It also demonstrates good thermal stability, ensuring the product is not easily degraded by heat during processing and use.

[0052] Comparative Example 1: Traditional phthalate plasticizers have poor compatibility with PVC resin, leading to significant plasticizer migration. This migration forms micropores within the adhesive layer, creating channels for solvent molecules to penetrate and affecting solvent resistance. Simultaneously, plasticizer migration disrupts the bond state of the resin molecular chains, resulting in decreased mechanical properties and a shortened thermal stability time.

[0053] Comparative Example 2: The compatibility of barium-zinc stabilizer with other components is not as good as that of calcium-zinc stabilizer, leading to trace migration of plasticizer, damage to the integrity of the adhesive layer structure, and weakened solvent resistance. At the same time, the barium-zinc stabilizer's ability to inhibit resin degradation is weaker than that of calcium-zinc stabilizer, and its uneven dispersion with other components results in a decline in mechanical properties and a shortened thermal stability time.

[0054] Comparative Example 3: After omitting secondary plasticizing, the material exhibits localized uneven plasticizing, resulting in insufficient system density and trace migration of plasticizers. Solvent resistance is compromised, as the localized porous structure caused by uneven plasticizing provides pathways for solvent penetration. Mechanical properties and thermal stability are also lower than in the examples due to insufficient component dispersion uniformity and the presence of minute defects within the adhesive layer.

[0055] It is understood that those skilled in the art can make equivalent substitutions or changes to the technical solution and inventive concept of the present invention, and all such changes or substitutions should fall within the protection scope of the present invention.

Claims

1. A solvent-resistant, non-migratory PVC adhesive, characterized in that, The product comprises the following components by weight: 100 parts PVC resin, 50-60 parts adipate polyester plasticizer, 3-5 parts calcium zinc stabilizer, and 2-4 parts functional additives; the adipate polyester plasticizer has a viscosity of 2300-3500 cps at 25°C and an acid value ≤1 KOH mg / g.

2. The solvent-resistant, non-migratory PVC adhesive according to claim 1, characterized in that, The adipate polyester plasticizer has a viscosity of 2800 cps at 25°C and an acid value ≤0.5 KOH mg / g.

3. The solvent-resistant, non-migratory PVC adhesive according to claim 1, characterized in that, The mass ratio of calcium salt to zinc salt in the calcium-zinc stabilizer is (2-3):

1.

4. The solvent-resistant, non-migratory PVC adhesive according to claim 1, characterized in that, The functional additives are butyl stearate and phenolic antioxidants; the mass ratio of butyl stearate to phenolic antioxidants is (2-3):

1.

5. The solvent-resistant, non-migratory PVC adhesive according to claim 1, characterized in that, The degree of polymerization of the PVC resin is 1800–2200, and the K value is 75–82.

6. The solvent-resistant, non-migratory PVC adhesive according to claim 5, characterized in that, The raw materials for preparing the PVC resin include the following components by weight: 100 parts vinyl chloride monomer, 150-180 parts deionized water, 0.1-0.2 parts particle modifier, 0.8-1.2 parts composite emulsifier, 0.05-0.08 parts oil-soluble initiator, 0.03-0.05 parts chain transfer agent, and 0.1-0.2 parts pH adjuster.

7. The solvent-resistant, non-migratory PVC adhesive according to claim 6, characterized in that, The composite emulsifier is a compound product of sorbitan monostearate and polyoxyethylene dehydrated sorbitan monolaurate in a mass ratio of (2-3):

1.

8. The solvent-resistant, non-migratory PVC adhesive according to claim 6, characterized in that, The particle modifier is calcium stearate; the oil-soluble initiator is di(2-ethylhexyl) peroxide dicarbonate; the chain transfer agent is dodecyl mercaptan; and the pH adjuster is an aqueous solution of sodium bicarbonate.

9. A method for preparing a solvent-resistant, non-migratory PVC adhesive, characterized in that, The process includes the following steps: thoroughly mixing the raw materials and then performing primary plasticization; filtering the primary plasticized material and then performing secondary plasticization; calendering and cooling the secondary plasticized material to obtain the solvent-resistant non-migratory PVC adhesive as described in any one of claims 1-8.

10. The method for preparing the solvent-resistant, non-migratory PVC adhesive according to claim 9, characterized in that, The raw materials are stirred at a temperature of 100–110℃ and a rotation speed of 1200–1500 r / min for 360–400 s; the temperature of the first plasticizing is 210–220℃ and the time is 300–320 s; the temperature of the second plasticizing is 190–200℃ and the time is 300–320 s; a multi-roll calendering process is adopted, wherein the temperature of the first roll is 220℃, the temperature of the second roll is 220℃, the temperature of the third roll is 210℃, the temperature of the fourth roll is 210℃, the temperature of the fifth roll is 200℃, the temperature of the sixth roll is 185–190℃, and the calendering speed is 1.5–2.0 m / min.

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