A PVC material with continuously gradient distribution of mildew resistance and a preparation method thereof

Abstract

The application discloses a kind of preparation methods of the continuous gradient distribution of mildew-proof performance polyvinyl chloride material, mixed polyvinyl chloride resin, plasticizer, mildew-proof agent and heat stabilizer are respectively obtained surface layer premix and bottom layer premix, the mass ratio of mildew-proof agent in surface layer premix is higher than the mass ratio of mildew-proof agent in bottom layer premix;The surface layer initial mixture and bottom layer initial mixture are respectively extruded melt plasticization, and are introduced into multilayer co-extrusion die and are co-extruded composite, and the composite type blank with double-layer structure is obtained;The composite type blank is heat-pressed, and when heat-pressed, the first heat-pressing surface temperature that contacts with surface layer remains constant, and the second heat-pressing surface temperature that contacts with bottom layer gradually increases from the glass transition temperature of polyvinyl chloride to not higher than the temperature of the first heat-pressing surface;The material after heat pressing is cooled and shaped to obtain finished product.The application also discloses polyvinyl chloride material prepared by the method.The application can realize the continuous gradient distribution of mildew-proof performance without adding low surface carrier.

Description

Technical Field

[0001] This invention relates to the field of polyvinyl chloride (PVC) materials technology, and in particular to a PVC material with a continuously gradient distribution of anti-mildew properties and its preparation method. Background Technology

[0002] Anti-mildew polyvinyl chloride (PVC) materials are mostly produced by integral mixing, with the anti-mildew agent evenly dispersed inside the PVC. The drawbacks of this method are: (1) The anti-mildew agent inside is encapsulated in the matrix and cannot come into contact with mold, resulting in a huge waste of resources. (2) In order to ensure long-term effect, excessive anti-mildew agent is often added, which not only greatly increases the cost, but may also lead to excessive migration of the anti-mildew agent into the environment, bringing biosafety risks. (3) High doses of anti-mildew agent can sometimes damage the mechanical properties and processing stability of PVC, especially when PVC is used as an insulating material, it is even more necessary to avoid adding excessive additives.

[0003] To address the aforementioned issues, existing technologies employ methods that utilize dispersants to enrich surface antifungal components. While this reduces the total consumption of antifungal agents to some extent, it heavily relies on external migration carriers with low surface energy and high fluidity (such as siloxanes or fluorinated siloxanes). This leads to excessive "blooming" or "oiling" of antifungal agent molecules on the material surface during migration. "Blooming" and "oiling" can easily become sites of mechanical failure, affecting the appearance and mechanical properties of the product. Furthermore, in polyvinyl chloride materials produced using existing technologies, the concentration of the antifungal agent changes gradually from the outer surface to the interior of the material, failing to create a unidirectional gradient of antifungal agent concentration between the two surface layers. Summary of the Invention

[0004] To address the aforementioned deficiencies in the prior art, the present invention aims to provide a polyvinyl chloride (PVC) material with a continuously gradient distribution of anti-mildew properties and its preparation method. This method aims to eliminate the mechanical failure and appearance contamination risks caused by abrupt changes in composition in multilayer co-extruded polymer materials without introducing an external low-surface-energy migration carrier, thereby achieving a unidirectional gradient change in the concentration of anti-mildew agents between different surface layers of the PVC material.

[0005] The technical solution of this invention is as follows: A method for preparing a polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties, comprising: Polyvinyl chloride resin, plasticizer, mildew inhibitor, and heat stabilizer are mixed to obtain a surface premix and a bottom premix, respectively, wherein the mass percentage of mildew inhibitor in the surface premix is ​​higher than that in the bottom premix; The surface premix and the bottom premix are extruded, melted and plasticized, and then introduced into a multi-layer co-extrusion die for co-extrusion composite to obtain a composite preform with a double-layer structure. The composite preform is hot-pressed. During hot pressing, the temperature of the first hot-pressing surface that is in contact with the side of the composite preform with a higher mass ratio of antifungal agent remains stable, while the temperature of the second hot-pressing surface that is in contact with the side of the composite preform with a lower mass ratio of antifungal agent gradually increases from the glass transition temperature of polyvinyl chloride to a temperature not higher than that of the first hot-pressing surface. The hot-pressed material is cooled and shaped to obtain the finished product.

[0006] Furthermore, during the process of gradually increasing the temperature of the second hot-pressing surface in contact with the side of the composite preform where the antifungal agent has a lower mass ratio from the glass transition temperature of polyvinyl chloride to a temperature not higher than that of the first hot-pressing surface, multiple heat preservation temperature points are set, and the temperature is maintained at each heat preservation temperature point for 1 to 5 minutes. By setting multiple heat preservation points, a stepped temperature control is formed, making the change in the antifungal agent concentration gradient smoother and more continuous.

[0007] Furthermore, the temperature of the first hot-pressing surface is 160–180°C, and the initial temperature of the second hot-pressing surface is 80–105°C.

[0008] Furthermore, the insulation temperature points are 110–130℃, 130–150℃, and 150–160℃.

[0009] Furthermore, the mass ratio of the antifungal agent to the polyvinyl chloride resin in the surface premix is ​​2% to 4%.

[0010] Furthermore, the mass ratio of the antifungal agent to the polyvinyl chloride resin in the underlying premix is ​​0.

[0011] Further, the antifungal agent is at least one of 2-octyl-4-isothiazolinone-3-one, pentachlorophenol, sodium pentachlorophenolate, salicylaniline, 8-hydroxyquinoline copper bis(tri-n-butyltin) oxide, N-(trichloromethylthio)phthalimide, and 2,2'-dihydroxy-5,5'-dichlorodiphenylmethane.

[0012] Further, the plasticizer is at least one selected from dioctyl phthalate, diisononyl phthalate, dioctyl adipate, trioctyl decaminate, polyester malonic acid, polyester adipate, epoxidized soybean oil, terephthalate, and citrate.

[0013] Further, the heat stabilizer is at least one of tribasic lead sulfate, dibasic lead phosphite, dibasic lead stearate, lead stearate, tin thiolate, dibutyltin dilaurate, dibutyltin maleate, calcium stearate, barium stearate, epoxidized soybean oil, pentaerythritol, and triphenyl phosphite.

[0014] Another technical solution of the present invention is: a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties, which is prepared by the aforementioned preparation method, and the anti-mildew agent of the polyvinyl chloride material is distributed from the surface layer to the bottom layer to 10% to 100% of the thickness direction.

[0015] This invention achieves thermal relaxation of the PVC macromolecular chains in the bottom layer by gradually narrowing the temperature difference gradient between the two sides during hot pressing above the glass transition temperature. The previously frozen free volume of PVC opens and releases layer by layer in a stepwise manner. The small molecules of the antifungal agent continue to steadily advance into the inner depth under the replenishment of thermal energy, in accordance with the newly released microscopic network channels, forming a smooth and continuous sliding gradient distribution with a concentration that monotonically decreases from the material surface to the bottom layer.

[0016] Compared with the prior art, the advantages of the technical solution of the present invention are as follows: This invention achieves a gradient distribution of the antifungal agent without the need for dispersants and surface treatment agents. Through a multi-segment asymmetric gradient temperature field hot-pressing process, it ensures excellent antifungal effects while avoiding "blooming" or "oiling" phenomena on the product, thus improving the product's appearance and mechanical stability.

[0017] This invention employs a dual-drive approach of temperature and concentration differences to induce a deep, controllable, kinetic-directional micro-diffusion of small antifungal molecules into the inner layer. This is a non-steady-state diffusion process that follows Fick's second law, with a gradient distribution covering 10% to 100% of the total thickness. The advantage of this continuous gradient is that when the antifungal agent on the outermost surface is depleted due to external factors, the high-concentration area in the subsurface can dynamically adapt to the newly formed local concentration gradient, continuously diffusing to replenish the surface layer. This endows the material with excellent physical durability and long-term antifungal stability. Detailed Implementation

[0018] The present invention will be further described below with reference to embodiments, but these are not intended to limit the scope of the invention.

[0019] Example 1

[0020] By weight fraction, the surface premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, 3 parts mildew inhibitor: 2-octyl-4-isothiazolinone-3-one, and 3 parts heat stabilizer: tribasic lead sulfate; the bottom premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, 0.01 parts mildew inhibitor: 2-octyl-4-isothiazolinone-3-one, and 3 parts heat stabilizer: tribasic lead sulfate.

[0021] The surface premix and the bottom premix are melt-plasticized separately using independent extruders and then co-extruded into a multi-layer co-extrusion die to obtain a composite preform with a two-layer structure. The surface layer of this composite preform, which is the side formed by the surface premix and has a higher proportion of antifungal agent, is defined as the top surface; the surface layer of the composite preform, which is the side formed by the surface premix and has a lower proportion of antifungal agent, is defined as the bottom surface.

[0022] The resulting double-layered composite preform was immediately placed in a hot press equipped with an independent dual temperature control system for multi-stage asymmetric gradient temperature rise hot pressing. Specifically, the temperature of the first hot pressing surface of the hot press, which contacts the top surface of the composite preform, was set constant at 180°C. The initial temperature of the second hot pressing surface, which contacts the bottom surface of the composite preform, was set within the glass transition temperature range of polyvinyl chloride (PVC), specifically 100°C in this embodiment, and maintained at a hot pressing pressure of 8 MPa for 3 minutes. While maintaining the temperature of the first hot pressing surface, the temperature of the second hot pressing surface was increased stepwise using a programmed temperature control method, holding at multiple holding temperature points for 3 minutes each to complete the entire hot pressing process. These holding temperature points were 120°C, 140°C, and 160°C.

[0023] The material after hot pressing is immediately cooled and shaped to freeze the free volume of PVC and the slip gradient concentration distribution of the anti-mildew agent, thus obtaining a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties.

[0024] Example 2

[0025] By weight fraction, the surface premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, 2 parts mildew inhibitor: 2-octyl-4-isothiazolinone-3-one, and 3 parts heat stabilizer: tribasic lead sulfate; the bottom premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, and 3 parts heat stabilizer: tribasic lead sulfate.

[0026] The surface premix and the bottom premix are melt-plasticized separately using independent extruders and then co-extruded into a multi-layer co-extrusion die to obtain a composite preform with a two-layer structure. The surface layer of this composite preform, which is the side formed by the surface premix and has a higher proportion of antifungal agent, is defined as the top surface; the surface layer of the composite preform, which is the side formed by the surface premix and has a lower proportion of antifungal agent, is defined as the bottom surface.

[0027] The resulting double-layered composite preform was immediately placed in a hot press equipped with an independent dual temperature control system for multi-stage asymmetric gradient temperature rise hot pressing. Specifically, the temperature of the first hot pressing surface of the hot press, which contacts the top surface of the composite preform, was kept constant at 160°C. The initial temperature of the second hot pressing surface, which contacts the bottom surface of the composite preform, was set within the glass transition temperature range of polyvinyl chloride (PVC), and in this embodiment, 105°C was selected. This temperature was maintained for 1 minute under a hot pressing pressure of 6 MPa. While maintaining the temperature of the first hot pressing surface, the temperature of the second hot pressing surface was increased stepwise using a programmed temperature control method, and held for 1 minute at each of the multiple holding temperature points to complete the entire hot pressing process. The holding temperature points were 130°C, 150°C, and 155°C.

[0028] The material after hot pressing is immediately cooled and shaped to freeze the free volume of PVC and the slip gradient concentration distribution of the anti-mildew agent, thus obtaining a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties.

[0029] Example 3

[0030] By weight fraction, the surface premix consists of 100 parts polyvinyl chloride resin, 2 parts plasticizer (dioctyl phthalate), 4 parts mildew inhibitor (2-octyl-4-isothiazolinone-3-one), and 3 parts heat stabilizer (tribasic lead sulfate); the bottom premix consists of 100 parts polyvinyl chloride resin, 2 parts plasticizer (dioctyl phthalate), 0.02 parts mildew inhibitor (2-octyl-4-isothiazolinone-3-one), and 3 parts heat stabilizer (tribasic lead sulfate).

[0031] The surface premix and the bottom premix are melt-plasticized separately using independent extruders and then co-extruded into a multi-layer co-extrusion die to obtain a composite preform with a two-layer structure. The surface layer of this composite preform, which is the side formed by the surface premix and has a higher proportion of antifungal agent, is defined as the top surface; the surface layer of the composite preform, which is the side formed by the surface premix and has a lower proportion of antifungal agent, is defined as the bottom surface.

[0032] The resulting double-layered composite preform was immediately placed in a hot press equipped with an independent dual temperature control system for multi-stage asymmetric gradient temperature rise hot pressing. Specifically, the temperature of the first hot pressing surface of the hot press, which contacts the top surface of the composite preform, was kept constant at 170°C. The initial temperature of the second hot pressing surface, which contacts the bottom surface of the composite preform, was set within the glass transition temperature range of polyvinyl chloride (PVC), specifically 95°C in this embodiment, and maintained at a hot pressing pressure of 12 MPa for 5 minutes. While maintaining the temperature of the first hot pressing surface, the temperature of the second hot pressing surface was increased stepwise using a programmed temperature control method, holding at multiple holding temperature points for 5 minutes each to complete the entire hot pressing process. The holding temperature points were 110°C, 130°C, and 150°C.

[0033] The material after hot pressing is immediately cooled and shaped to freeze the free volume of PVC and the slip gradient concentration distribution of the anti-mildew agent, thus obtaining a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties.

[0034] Example 4

[0035] By weight fraction, the surface premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, 3 parts mildew inhibitor: 2-octyl-4-isothiazolinone-3-one, and 3 parts heat stabilizer: tribasic lead sulfate; the bottom premix is ​​composed of 100 parts polyvinyl chloride resin, 2 parts plasticizer: dioctyl phthalate, 0.01 parts mildew inhibitor: 2-octyl-4-isothiazolinone-3-one, and 3 parts heat stabilizer: tribasic lead sulfate.

[0036] The surface premix and the bottom premix are melt-plasticized separately using independent extruders and then co-extruded into a multi-layer co-extrusion die to obtain a composite preform with a two-layer structure. The surface layer of this composite preform, which is the side formed by the surface premix and has a higher proportion of antifungal agent, is defined as the top surface; the surface layer of the composite preform, which is the side formed by the surface premix and has a lower proportion of antifungal agent, is defined as the bottom surface.

[0037] The resulting double-layer composite preform was immediately placed in a hot press equipped with an independent dual temperature control system for asymmetric temperature rise hot pressing. Specifically, the temperature of the first hot pressing surface of the hot press, which contacts the top surface of the composite preform, was set to a constant 180°C, and the temperature of the second hot pressing surface, which contacts the bottom surface of the composite preform, was set to a constant 150°C. The preform was then hot-pressed at 8 MPa for 15 minutes to complete the molding process.

[0038] The material after hot pressing is immediately cooled and shaped to freeze the free volume of PVC and the slip gradient concentration distribution of the anti-mildew agent, thus obtaining a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties.

[0039] All of the above embodiments can produce polyvinyl chloride materials in which the mass concentration of the antifungal agent decreases continuously along its thickness direction. In addition, by controlling the mass ratio of the surface premix and the bottom premix during co-extrusion and the time of the hot pressing process, different polyvinyl chloride materials with the antifungal agent distributed from the surface to the bottom layer in the thickness direction of 10% to 100% can be easily obtained as needed.

[0040] The polyvinyl chloride (PVC) materials obtained in Examples 1-4 were sealed at the bottom layer and then cultured in agar nutrient medium at 37°C and 90% relative humidity for 24 hours. No mold growth, blooming, or oiling was observed on the surface. In the elongation at break test, the elongation at break retention rates (elongation at break after experiment / elongation at break before experiment) of the PVC materials in Examples 1-4 were 86%, 82%, 79%, and 71%, respectively.

[0041] Finally, it should be noted that the antifungal agents, plasticizers, and heat stabilizers used in the foregoing embodiments are only illustrative. In some other embodiments, the antifungal agents may also be selected from one or more of pentachlorophenol, sodium pentachlorophenolate, salicylaniline, 8-hydroxyquinoline copper bis(tri-n-butyltin) oxide, N-(trichloromethylthio)phthalimide, and 2,2'-dihydroxy-5,5'-dichlorodiphenylmethane; the plasticizers may also be selected from one or more of diisononyl phthalate, dioctyl adipate, trioctyl decanteryltrimethyl phthalate, polyester malonic acid, polyester adipate, epoxidized soybean oil, terephthalate, and citrate; and the heat stabilizers may also be selected from one or more of dibasic lead phosphite, dibasic lead stearate, lead stearate, tin thiolate, dibutyltin dilaurate, dibutyltin maleate, calcium stearate, barium stearate, epoxidized soybean oil, pentaerythritol, and triphenyl phosphite.

Claims

1. A method for preparing a polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties, characterized in that, include: Polyvinyl chloride resin, plasticizer, mildew inhibitor, and heat stabilizer are mixed to obtain a surface premix and a bottom premix, respectively, wherein the mass percentage of mildew inhibitor in the surface premix is ​​higher than that in the bottom premix; The surface premix and the bottom premix are extruded, melted and plasticized, and then introduced into a multi-layer co-extrusion die for co-extrusion composite to obtain a composite preform with a double-layer structure. The composite preform is hot-pressed. During hot pressing, the temperature of the first hot-pressing surface that is in contact with the side of the composite preform with a higher mass ratio of antifungal agent remains stable, while the temperature of the second hot-pressing surface that is in contact with the side of the composite preform with a lower mass ratio of antifungal agent gradually increases from the glass transition temperature of polyvinyl chloride to a temperature not higher than that of the first hot-pressing surface. The hot-pressed material is cooled and shaped to obtain the finished product.

2. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, During the process of gradually increasing the temperature of the second hot-pressing surface in contact with the side of the composite preform where the antifungal agent has a lower mass ratio from the glass transition temperature of polyvinyl chloride to a temperature not higher than that of the first hot-pressing surface, multiple heat preservation temperature points are set, and the temperature is maintained at the heat preservation temperature points for 1 to 5 minutes.

3. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, The temperature of the first hot-pressing surface is 160-180℃, and the initial temperature of the second hot-pressing surface is 80-105℃.

4. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 2, characterized in that, The temperature of the first hot-pressing surface is 160-180℃, the initial temperature of the second hot-pressing surface is 80-105℃, and the heat preservation temperature points are 110-130℃, 130-150℃, and 150-160℃.

5. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, The surface premix contains 2% to 4% by mass of antifungal agent.

6. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1 or 5, characterized in that, The mass percentage of the antifungal agent in the underlying premix is ​​0.

7. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, The antifungal agent is at least one of 2-octyl-4-isothiazolinone-3-one, pentachlorophenol, sodium pentachlorophenolate, salicylaniline, 8-hydroxyquinoline copper bis(tri-n-butyltin) oxide, N-(trichloromethylthio)phthalimide, and 2,2'-dihydroxy-5,5'-dichlorodiphenylmethane.

8. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, The plasticizer is at least one of dioctyl phthalate, diisononyl phthalate, dioctyl adipate, trioctyl decaminate, polyester malonic acid, polyester adipate, epoxidized soybean oil, terephthalate, and citrate.

9. The method for preparing polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties according to claim 1, characterized in that, The heat stabilizer is at least one of the following: tribasic lead sulfate, dibasic lead phosphite, dibasic lead stearate, lead stearate, tin thiolate, dibutyltin dilaurate, dibutyltin maleate, calcium stearate, barium stearate, epoxidized soybean oil, pentaerythritol, and triphenyl phosphite.

10. A polyvinyl chloride material with a continuously gradient distribution of anti-mildew properties, characterized in that, The polyvinyl chloride material is prepared by the method of preparing a polyvinyl chloride material with a continuous gradient distribution of anti-mildew properties as described in any one of claims 1 to 9, wherein the anti-mildew agent of the polyvinyl chloride material is distributed from the surface layer to the bottom layer to 10% to 100% of the thickness direction.