Method for producing resin composition

Abstract

To remove a lead of a resin molding containing a lead-based stabilizer containing polyvinyl chloride as a main component, recycle the resin molding, and efficiently produce a resin composition of polyvinyl chloride.SOLUTION: A method for producing a resin composition removes a lead of a resin molding containing a lead-based stabilizer containing polyvinyl chloride as a main component, and produces a resin composition of polyvinyl chloride. The method for producing the resin composition includes: a crushing step of crushing a resin molding and forming a crushed material; a dissolution step of immersing the crushed material in an acidic or alkaline liquid, and dissolving the lead contained in the lead-based stabilizer in the liquid from the crushed material; and a separation step of separating the crushed material from the liquid where the lead is dissolved.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a polyvinyl chloride resin composition from a polyvinyl chloride resin molded article containing a lead-based stabilizer. [Background technology]

[0002] Resin molded products such as resin profiles mainly composed of polyvinyl chloride are used for fittings such as resin windows. Conventionally, resin molded products containing a lead-based stabilizer as a thermal stabilizer have been used. When such resin molded products containing a lead-based stabilizer are recycled to produce a polyvinyl chloride resin composition, it is preferable to remove the lead from the resin molded products from the viewpoint of safety, etc. In response to this, a method for recovering polyvinyl chloride by removing heavy metals from a waste polyvinyl chloride resin composition has been known (see Patent Document 1).

[0003] In the conventional method for recovering polyvinyl chloride described in Patent Document 1, a waste vinyl chloride resin composition is dissolved in an organic solvent to prepare a polymer solution. In addition, after the polymer solution is brought into contact with an adsorbent, heavy metals are removed from the polymer solution by solid-liquid separation. However, the process of dissolving the waste vinyl chloride resin composition in an organic solvent and the process of preparing the polymer solution can be time-consuming. In addition, when recovering polyvinyl chloride from the polymer solution from which heavy metals have been removed, it is necessary to bring the polymer solution into contact with a precipitation solution to precipitate polyvinyl chloride, and there is a risk that the process for recovering and reusing polyvinyl chloride will become complicated. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2008-174666 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned conventional problems, and an object of the present invention is to remove lead from a resin molded article containing polyvinyl chloride as a main component and a lead-based stabilizer, thereby recycling the resin molded article, and to efficiently produce a polyvinyl chloride resin composition. [Means for solving the problem]

[0006] The present invention relates to A method for producing a polyvinyl chloride resin composition by removing lead from a resin molded article containing polyvinyl chloride as a main component and a lead-based stabilizer, comprising the steps of: A crushing step of crushing the resin molded product to form a crushed material; a dissolving step of immersing the pulverized material in an acidic or alkaline liquid to dissolve the lead contained in the lead-based stabilizer from the pulverized material into the liquid; a separation step of separating the pulverized material from the liquid in which the lead has been dissolved; The present invention relates to a method for producing a resin composition having the above structure. Effect of the Invention

[0007] According to the present invention, lead can be removed from a resin molded article containing polyvinyl chloride as a main component and a lead-based stabilizer, the resin molded article can be recycled, and a polyvinyl chloride resin composition can be efficiently produced. [Brief description of the drawings]

[0008] [Figure 1] 1 is a flowchart showing a procedure for producing a polyvinyl chloride resin composition of the present embodiment. [Diagram 2] FIG. 2 is a diagram showing a schematic diagram of each stage of the production process of the polyvinyl chloride resin composition of the present embodiment. [Diagram 3] 1A to 1C are diagrams showing examples of pulverized material to be immersed in an acidic or alkaline liquid in this embodiment. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of an extruder used to melt pulverized material in this embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] An embodiment of the method for producing a resin composition of the present invention will be described with reference to the drawings. In the method for producing a resin composition according to the present embodiment, lead is removed from a resin molded article containing polyvinyl chloride as a main component and a lead-based (Pb-based) stabilizer to produce a polyvinyl chloride resin composition. This allows the resin molded article once produced to be reused, recycled into a resin composition, and a new resin composition is produced.

[0010] Fig. 1 is a flow chart showing the procedure (steps) for producing the polyvinyl chloride resin composition of the present embodiment. Fig. 2 is a diagram showing the state of each stage of the process for producing the polyvinyl chloride resin composition of the present embodiment.

[0011] As shown in the figure, a resin molded product 10 (see FIG. 2A) that is no longer needed is collected (S101 in FIG. 1). The resin molded product 10 is a molded product made by molding a synthetic resin. The synthetic resin is polyvinyl chloride (PVC), and the resin molded product 10 is a polyvinyl chloride molded product that contains polyvinyl chloride as the main component and a lead-based stabilizer. The polyvinyl chloride is either hard polyvinyl chloride with no plasticizer added, or soft polyvinyl chloride with a plasticizer added. The plasticizer is an additive that gives flexibility to polyvinyl chloride and softens it.

[0012] The stabilizer is a heat stabilizer that suppresses the thermal decomposition of polyvinyl chloride, and suppresses the decomposition of polyvinyl chloride due to heat when polyvinyl chloride is heated and molded. The lead-based stabilizer is a stabilizer that contains lead as an ingredient, such as lead stearate, tribasic lead sulfate, dibasic lead phthalate, and dibasic lead stearate. The resin molded product 10 is made of polyvinyl chloride and contains various additives (e.g., improvers) in addition to the lead-based stabilizer. The resin molded product 10 is, for example, a resin profile, an injection molded product of synthetic resin, a resin sheet, or a resin hose.

[0013] Here, the resin molded product 10 is a resin shaped material, and Fig. 2A shows a cross section perpendicular to the longitudinal direction of the resin molded product 10. The resin shaped material is a material (extruded material) formed by extrusion molding of a synthetic resin, and the resin molded product 10 is a polyvinyl chloride shaped material made of polyvinyl chloride. Specifically, the resin molded product 10 is a resin molded product (resin shaped material) used in a resin window, which is a fixture. The resin window has a frame (resin frame) made of synthetic resin, and a paper screen including a stile (resin frame) made of synthetic resin, and the resin frame and the resin frame are each made of the resin molded product 10.

[0014] In this way, the resin molded product 10 is a resin molded product (waste resin molded product) that is a discarded resin shaped material. The resin molded product 10 is used as a raw material to remove lead contained in the lead-based stabilizer from the resin molded product 10, and a polyvinyl chloride resin composition is manufactured. At that time, the lead contained in the resin molded product 10 is removed and reduced by a lead removal process, and polyvinyl chloride is recovered from the resin molded product 10. In the manufactured polyvinyl chloride resin composition, the lead concentration is reduced compared to the lead concentration in the original resin molded product 10. The polyvinyl chloride resin composition is a composition mainly composed of polyvinyl chloride, and is used as a raw material for polyvinyl chloride molded products (recycled molded products).

[0015] Prior to the lead removal process, the collected resin molded articles 10 are crushed by a crusher to form crushed material 20 of the resin molded articles 10 (see FIG. 2B) (S102 in FIG. 1). The crusher is, for example, an impact crusher, which is an impact type crusher. When the resin molded articles 10 are long or large, the resin molded articles 10 are cut or otherwise formed into a size that can be crushed by the crusher before being crushed by the crusher. In this manner, the crushed material 20 is generated by crushing the resin molded articles 10. The crushed material 20 is formed into, for example, a flake-like, granular, or powder-like shape.

[0016] After crushing the resin molded product 10 (see FIG. 2C), the crushed material 20 of the resin molded product 10 is immersed in an acidic or alkaline liquid 30, and the lead contained in the lead-based stabilizer of the resin molded product 10 is dissolved from the crushed material 20 into the liquid 30 (S103 in FIG. 1). The acidic or alkaline liquid 30 is a dissolving liquid that dissolves the lead in the crushed material 20, and is contained in a container 31. The acidic liquid 30 is, for example, hydrochloric acid, sulfuric acid, or nitric acid, and is various acids that are not diluted with water or various acids that are diluted with water. The alkaline liquid 30 is, for example, an aqueous solution of sodium hydroxide.

[0017] The crushed material 20 is placed in the liquid 30 in the container 31, and the crushed material 20 is immersed in the liquid 30. While the crushed material 20 is immersed in the liquid 30, the lead in the crushed material 20 gradually dissolves in the liquid 30. Also, the lead on the surface of the crushed material 20 dissolves in the liquid 30 first, and the lead inside the crushed material 20 gradually dissolves. The dissolution of lead in the liquid 30 removes the lead from the crushed material 20.

[0018] FIG. 3 is a diagram showing an example of the pulverized material 20 to be immersed in the acidic or alkaline liquid 30 of this embodiment. As shown in the figure, the resin molded product 10 is crushed to form crushed materials 20 of various shapes and maximum dimensions R. The maximum dimension R of the crushed material 20 is the dimension of the largest part of the outer shape of each crushed material 20. The maximum dimension R of the crushed material 20 to be immersed in the liquid 30 is within a range of 200 μm to 10 mm. Therefore, when crushing the resin molded product 10, the resin molded product 10 is crushed so that the maximum dimension R of the crushed material 20 is 200 μm to 10 mm. Alternatively, after crushing the resin molded product 10, a separator or the like is used to separate and remove the crushed material 20 having a maximum dimension R smaller than 200 μm and the crushed material 20 having a maximum dimension R larger than 10 mm, and the crushed material 20 having a maximum dimension R of 200 μm to 10 mm is selected. The crushed material 20 having a maximum dimension R of 200 μm to 10 mm is immersed in the liquid 30.

[0019] In the process of removing lead from the pulverized material 20 (resin molded product 10) by immersing the pulverized material 20 in the liquid 30 (process of removing lead from the pulverized material 20 by immersion), the pulverized material 20 is immersed in the liquid 30 while stirring the pulverized material 20 and the liquid 30. In addition, the pulverized material 20 is immersed in the liquid 30 for a predetermined time while the liquid 30 and the pulverized material 20 are heated to a predetermined temperature. For example, the pulverized material 20 is immersed in the liquid 30 for a predetermined time while stirring the pulverized material 20 and the liquid 30 while the temperature of the liquid 30 and the pulverized material 20 is maintained at a predetermined temperature by a thermostatic device.

[0020] Next, the crushed material 20 is taken out from the liquid 30 in which the lead is dissolved, and the crushed material 20 is separated from the liquid 30 (S104 in FIG. 1). Next, the crushed material 20 is washed with water by a water washing device. The liquid 30 is washed away from the crushed material 20 with water, and the crushed material 20 is washed. After that, the water is removed from the crushed material 20 by a drying device, and the crushed material 20 is dried.

[0021] In the crushed material 20 of the resin molded product 10 immersed in the liquid 30, the degree of dissolution of lead differs between the surface side and the center side. Therefore, after the lead removal process of the crushed material 20 by immersion, a process of removing lead from the molten material 21 of the crushed material 20 (see FIG. 2D) by melting the crushed material 20 with an adsorbent 40 (removal process of lead from the molten material 21 by the adsorbent 40) is performed (S105 in FIG. 1). This removes the lead remaining in the crushed material 20 after immersion.

[0022] The molten material 21 is a molten polyvinyl chloride product of the pulverized material 20, and contains a lead-based stabilizer. When the pulverized material 20, which is polyvinyl chloride, is heated and melted, the lead contained in the lead-based stabilizer becomes a cation in the molten material 21, and the lead ion, which is the cation of lead, suppresses the thermal decomposition of the polyvinyl chloride. In response to this, by adding an adsorbent 40 to the molten material 21, the lead ion is adsorbed by the adsorbent 40, and the lead is removed from the molten material 21.

[0023] The adsorbent 40 is a solid cation adsorbent that adsorbs cations, and adsorbs lead ions, which are cations, in the molten material 21 of the pulverized material 20. The adsorbent 40 is, for example, zeolite, chitosan, a porous material, or a double hydroxide such as layered double hydroxide (LDH), and is formed in a powder or granular form. An inorganic adsorbent is used for the adsorbent 40 so that it does not decompose even at the temperature of the molten material 21.

[0024] The adsorbent 40 is added to the pulverized material 20 before melting, and the pulverized material 20 is melted, thereby adding the adsorbent 40 to the molten material 21. Alternatively, the adsorbent 40 is added to the molten material 21 after the pulverized material 20 is melted. Here, the pulverized material 20 and the powdered adsorbent 40 (adsorbent powder) are fed into an extruder, and the pulverized material 20 is melted by the extruder. Therefore, the adsorbent 40 is added to the pulverized material 20 before melting, and the pulverized material 20 is melted.

[0025] FIG. 4 is a diagram showing a schematic configuration of an extruder 50 used to melt the pulverized material 20 in this embodiment. As shown in the figure, the pulverized material 20 and the adsorbent 40, together with various additives, are fed into the extruder 50 from the inlet 51 (hopper) of the extruder 50. Inside the extruder 50, the extruder 50 heats the pulverized material 20 and the adsorbent 40 to raise the temperature, melting the pulverized material 20 and generating a molten material 21 of the pulverized material 20 (S105-1 in FIG. 1). In this way, the pulverized material 20 separated from the liquid 30 is melted to obtain a molten material 21 of the pulverized material 20.

[0026] The extruder 50 heats and kneads the pulverized material 20 and the adsorbent 40, and the pulverized material 20 is heated and melted. As a result, inside the extruder 50, the solid adsorbent 40 that adsorbs lead ions is added to the molten material 21 of the pulverized material 20. In addition, lead ions are generated in the molten material 21 as the pulverized material 20 melts. Inside the extruder 50, a screw (not shown) is provided. The extruder 50 stirs and kneads the molten material 21 and the adsorbent 40 with the rotating screw. The extruder 50 stirs the molten material 21 to which the adsorbent 40 has been added, kneads the molten material 21 and the adsorbent 40, and adsorbs the lead ions in the molten material 21 with the adsorbent 40 (S105-2 in FIG. 1). Lead is removed from the molten material 21 by the adsorption of lead ions to the adsorbent 40.

[0027] Here, the polyvinyl chloride, which is the main component of the resin molded product 10, is rigid polyvinyl chloride, and the polyvinyl chloride resin composition produced is a rigid polyvinyl chloride resin composition. Therefore, the melt 21 of the pulverized material 20 is heated to a temperature suitable for melting the rigid polyvinyl chloride. Specifically, the pulverized material 20 is heated to a temperature within a range of 180 to 210°C to melt the pulverized material 20. The melt 21 to which the adsorbent 40 has been added is heated to a temperature within a range of 180 to 210°C, and the melt 21 and the adsorbent 40 are stirred at a temperature of 180 to 210°C, and the lead (lead ions) contained in the melt 21 is removed by the adsorbent 40.

[0028] Next, the adsorbent 40 that has adsorbed the lead ions is separated from the molten material 21 (S105-3 in FIG. 1) to produce a polyvinyl chloride resin composition from which lead has been removed. Inside the extruder 50, a filter 52 used for separating the adsorbent 40 is provided. The filter 52 is a sieve that filters the adsorbent 40 from the molten material 21, and prevents the adsorbent 40 from passing through while allowing the molten material 21 to pass through. The extruder 50 passes the molten material 21 through the filter 52, and the adsorbent 40 is separated from the molten material 21 by the filter 52.

[0029] The mesh (number) of the filter 52 is 20 to 100 mesh. The molten material 21 is passed through the filter 52 having a mesh size within the range of 20 to 100 mesh, and the adsorbent 40 is separated from the molten material 21 by the filter 52 having a mesh size of 20 to 100 mesh. The mesh of the filter 52 is a sieve mesh specified in the ASTM standard (ASTM E11-04) and complies with the ASTM standard. The mesh size of the 20-mesh filter 52 is about 0.80 mm, and the mesh size of the 100-mesh filter 52 is about 0.15 mm. Therefore, the mesh size of the filter 52 is about 0.15 to 0.80 mm.

[0030] Inside the extruder 50, the pulverized material 20 is melted, the molten material 21 to which the adsorbent 40 has been added is stirred (the adsorbent 40 adsorbs lead ions), and the adsorbent 40 is separated from the molten material 21 in succession. The extruder 50 then extrudes the molten material 21 that has passed through the filter 52 from an extrusion port 53 (die) to extrude the molten material 21 (S105-4 in FIG. 1). The extrusion of the molten material 21 extruded from the extrusion port 53 is cut in sequence to form pellets 22 (see FIG. 2E).

[0031] The polyvinyl chloride resin composition extruded as the molten material 21 is processed to form pellets 22 made of the polyvinyl chloride resin composition (S106 in FIG. 1). The pellets 22 are granular material containing polyvinyl chloride as a main component, and are formed into a granular shape. The polyvinyl chloride pellets 22 are then used to form a polyvinyl chloride molded product (S107 in FIG. 1). The polyvinyl chloride molded product is, for example, a resin shaped material that is molded by extrusion molding and used for building fixtures.

[0032] In the method for producing a polyvinyl chloride resin composition according to the present embodiment described above, lead is removed from a resin molded article 10 containing polyvinyl chloride as a main component and a lead-based stabilizer, and the resin molded article 10 is recycled, thereby efficiently producing a polyvinyl chloride resin composition. Also, the lead in the resin molded article 10 can be easily removed.

[0033] Before the adsorbent 40 is used to remove lead from the molten material 21, the pulverized material 20 is subjected to a process of removing lead by immersion. This allows the lead to be removed from the pulverized material 20 before the adsorbent 40 and the molten material 21 of the pulverized material 20 are mixed together, thereby reducing the lead content of the pulverized material 20 and the molten material 21.

[0034] When the maximum dimension R of the pulverized material 20 is smaller than 200 μm, it becomes difficult to separate the pulverized material 20 from the liquid 30. There is also a risk that it becomes difficult to wash and dry the pulverized material 20 after it is separated from the liquid 30. In addition, when the maximum dimension R of the pulverized material 20 is larger than 10 mm, the surface area (specific surface area) per unit mass of the pulverized material 20 becomes small, which may affect the efficiency of dissolving the lead of the pulverized material 20 into the liquid 30. There is also a risk that it becomes difficult to feed the pulverized material 20 into the extruder 50.

[0035] On the other hand, when the maximum dimension R of the pulverized material 20 is within the range of 200 μm to 10 mm (200 μm or more and 10 mm or less), the pulverized material 20 can be easily separated from the liquid 30. In addition, the specific surface area of ​​the pulverized material 20 can be secured, and the lead of the pulverized material 20 can be efficiently dissolved in the liquid 30. The pulverized material 20 can be smoothly washed with water, dried, and fed into the extruder 50. It is more preferable that the maximum dimension R of the pulverized material 20 is within the range of 2 to 8 mm. This allows the pulverized material 20 to be smoothly separated from the liquid 30, and the efficiency of dissolving the lead of the pulverized material 20 in the liquid 30 can be secured.

[0036] When the polyvinyl chloride is rigid polyvinyl chloride, if the temperature at which the molten material 21 to which the adsorbent 40 is added is stirred (the stirring temperature of the molten material 21) is lower than 180°C, the viscosity of the molten material 21 increases, making it difficult for the molten material 21 to flow, which may affect the stirring of the molten material 21. It also becomes difficult to extrude the molten material 21 using the extruder 50. In addition, if the stirring temperature of the molten material 21 is higher than 210°C, the rigid polyvinyl chloride of the molten material 21 may thermally decompose.

[0037] In contrast, when the stirring temperature of the molten material 21 is within the range of 180 to 210°C (180°C or higher and 210°C or lower), it is possible to prevent thermal decomposition of the rigid polyvinyl chloride in the molten material 21 while making the viscosity of the molten material 21 suitable for stirring, and to promote stirring due to the flow of the molten material 21. It is more preferable that the stirring temperature of the molten material 21 is within the range of 190 to 200°C. This makes it possible to reliably prevent thermal decomposition of the rigid polyvinyl chloride in the molten material 21 while maintaining the viscosity of the molten material 21 at a viscosity suitable for stirring.

[0038] The filter 52 allows the adsorbent 40 to be easily separated from the molten material 21 of the pulverized material 20. However, when the filter 52 is a filter coarser than 20 mesh (a filter with a smaller mesh number), there is a risk that the adsorbent 40 cannot be completely separated from the molten material 21. Furthermore, when the filter 52 is a filter finer than 100 mesh (a filter with a larger mesh number), the pressure applied to the molten material 21 to pass through the filter 52 becomes high, and there is a risk that the efficiency of separating the adsorbent 40 from the molten material 21 is affected. If the pressure of the extruder 50 extruding the molten material 21 becomes high, there is a risk that the productivity of the polyvinyl chloride resin composition is affected, and there is also a concern that the filter 52 will be damaged by the pressure of the molten material 21.

[0039] In contrast, when the mesh of the filter 52 is within the range of 20 to 100 mesh (20 mesh or more and 100 mesh or less), the adsorbent 40 can be stably separated from the melt 21 of the pulverized material 20, and the pressure applied to the melt 21 can be prevented from increasing, thereby ensuring the efficiency of separating the adsorbent 40 from the melt 21. In addition, the pressure of the extrusion of the melt 21 by the extruder 50 can be prevented from increasing, ensuring the productivity of the polyvinyl chloride resin composition, and preventing the filter 52 from being damaged by the pressure of the melt 21. It is more preferable that the mesh of the filter 52 is within the range of 40 to 80 mesh. This allows the adsorbent 40 to be efficiently separated from the melt 21 without applying high pressure to the melt 21.

[0040] In addition, when melting the pulverized material 20, polyvinyl chloride that does not contain lead (lead-based stabilizer) may be added to the pulverized material 20 separated from the liquid 30, and the added polyvinyl chloride and the pulverized material 20 may be melted and mixed to produce a polyvinyl chloride resin composition. The polyvinyl chloride added to the pulverized material 20 is a solid polyvinyl chloride, and is formed, for example, in a powdered or granular form. The polyvinyl chloride added to the pulverized material 20 may be unused polyvinyl chloride that does not contain lead, or polyvinyl chloride obtained by crushing a molded product of polyvinyl chloride that does not contain lead, and may be either unused polyvinyl chloride or polyvinyl chloride obtained by crushing a molded product. The pulverized material 20, the adsorbent 40, and the lead-free polyvinyl chloride are fed into an extruder, and the pulverized material 20 to which the lead-free polyvinyl chloride has been added is melted by the extruder 50 to obtain a melt 21 of polyvinyl chloride and the pulverized material 20. By adding lead-free polyvinyl chloride, the concentration of lead contained in the polyvinyl chloride resin composition can be reduced.

[0041] In the method for producing a polyvinyl chloride resin composition described above, the lead removal process of the crushed material 20 by immersion (see FIG. 2C) is performed, and then the lead removal process of the molten material 21 by the adsorbent 40 is performed (see FIG. 2D). In contrast, the lead removal process of the crushed material 20 by immersion may be performed without performing the lead removal process of the molten material 21 by the adsorbent 40 to produce a polyvinyl chloride resin composition. Even in this way, lead can be removed. In particular, when the lead concentration in the polyvinyl chloride resin composition can be reduced to a target concentration by the lead removal process of the crushed material 20 by immersion, it is effective to perform the lead removal process of the crushed material 20 by immersion without performing the lead removal process of the molten material 21 by the adsorbent 40. However, the lead concentration in the polyvinyl chloride resin composition can be further reduced by performing the lead removal process of the molten material 21 by the adsorbent 40 after performing the lead removal process of the crushed material 20 by immersion.

[0042] As described above, the present embodiment discloses the method for producing a resin composition described in the following (1) to (3).

[0043] (1) A method for producing a polyvinyl chloride resin composition by removing lead from a resin molding containing polyvinyl chloride as a main component and a lead-based stabilizer, comprising the steps of: A crushing step of crushing the resin molded product to form a crushed material; a dissolving step of immersing the pulverized material in an acidic or alkaline liquid to dissolve the lead contained in the lead-based stabilizer from the pulverized material into the liquid; a separation step of separating the pulverized material from the liquid in which the lead has been dissolved; A method for producing a resin composition comprising the steps of: In the method for producing a resin composition described in (1), lead is removed from a resin molded article containing polyvinyl chloride as a main component and a lead-based stabilizer, and the resin molded article is recycled, thereby making it possible to efficiently produce a polyvinyl chloride resin composition.

[0044] (2) A method for producing a resin composition according to (1), comprising the steps of: A method for producing a resin composition, wherein in the dissolving step, the pulverized material has a maximum size of 200 μm to 10 mm. In the method for producing a resin composition described in (2), the ground material can be easily separated from the liquid, and the lead in the ground material can be efficiently dissolved in the liquid.

[0045] (3) A method for producing a resin composition according to (1) or (2), comprising the steps of: A method for producing a resin composition, comprising a mixing step of adding lead-free polyvinyl chloride to the ground material separated from the liquid, and melting and mixing the polyvinyl chloride and the ground material. In the method for producing a resin composition described in (3), the concentration of lead contained in the polyvinyl chloride resin composition can be reduced by adding lead-free polyvinyl chloride. [Explanation of symbols]

[0046] 10···Resin molded product, 20···Ground material, 21···Melted material, 22···Pellets, 30···Liquid, 31···Container, 40···Adsorbent, 50···Extruder, 51···Inlet, 52···Filter, 53···Extrusion outlet, R···Maximum dimension.

Claims

1. A method for producing a polyvinyl chloride resin composition by removing lead from a resin molded article containing polyvinyl chloride as a main component and a lead-based stabilizer, comprising the steps of: A crushing step of crushing the resin molded product to form a crushed material; a dissolving step of immersing the pulverized material in an acidic or alkaline liquid to dissolve the lead contained in the lead-based stabilizer from the pulverized material into the liquid; a separation step of separating the pulverized material from the liquid in which the lead has been dissolved; A method for producing a resin composition comprising the steps of:

2. The method for producing a resin composition according to claim 1, In the dissolving step, the maximum dimension of the pulverized material is 200 μm to 10 mm.

3. The method for producing the resin composition according to claim 1 or 2, A method for producing a resin composition, comprising a mixing step of adding lead-free polyvinyl chloride to the ground material separated from the liquid, and melting and mixing the polyvinyl chloride and the ground material.

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