Method for manufacturing resin compositions

Abstract

To recycle a resin section containing hard polyvinyl chloride as a main component, and easily produce a resin composition of soft polyvinyl chloride.SOLUTION: A method for producing a resin composition produces a resin composition of soft polyvinyl chloride using a resin section containing hard polyvinyl chloride as a main component in a raw material. A method for producing a resin composition includes: a crushing step of crushing a resin section and forming a crushed material; and a mixing step of kneading the crushed material, a pellet made of soft polyvinyl chloride while heating, and producing a resin composition in which the crushed material and the pellet are mixed. The mixing step includes a step of kneading a kneaded product of the crushed material and the pellet while raising a heating temperature.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing a resin composition for producing a resin composition of soft polyvinyl chloride.

Background Art

[0002] In fittings such as resin windows, resin profiles mainly composed of rigid polyvinyl chloride are used. The resin profile is produced by heating and melting a resin material of rigid polyvinyl chloride and extruding the melted resin material. When recycling such a resin profile to produce a resin composition of soft polyvinyl chloride, for example, a pulverized material obtained by pulverizing the resin profile and a liquid plasticizer are kneaded, and the rigid polyvinyl chloride of the pulverized material is softened by the plasticizer to produce a resin composition of soft polyvinyl chloride.

[0003] However, in the resin profile after production, the resin particles are crushed by extrusion molding, and there are almost no voids in the resin particles that existed before extrusion molding. Along with this, during the kneading of the pulverized material of the resin profile and the plasticizer, it becomes difficult for the plasticizer to penetrate into the pulverized material, and the pulverized materials easily slide by the plasticizer. Therefore, it becomes difficult to knead the pulverized material of the resin profile and the plasticizer, and it becomes difficult to soften the rigid polyvinyl chloride of the pulverized material with the plasticizer. On the other hand, conventionally, a method for producing a vinyl chloride-based resin composition in which a pulverized product of a rigid vinyl chloride-based resin molded product, a plasticizer, and an inorganic filler are kneaded by a heating kneader to produce a vinyl chloride-based resin composition is also known (see Patent Document 1).

[0004] In the conventional method for manufacturing vinyl chloride resin compositions described in Patent Document 1, the plasticizer is absorbed by an inorganic filler, and the plasticizer is kneaded together with the inorganic filler into the pulverized material. However, because an inorganic filler is required for the absorption of the plasticizer, the amount of plasticizer that can be added is limited, which may make it difficult to manufacture a soft vinyl chloride resin composition. Furthermore, increasing the amount of plasticizer added requires increasing the amount of inorganic filler added, which may affect the physical properties of the vinyl chloride resin composition. Since the amount of plasticizer added depends on the type of inorganic filler, the design of the vinyl chloride resin composition may also be limited. Therefore, there is room for improvement in the conventional method for manufacturing vinyl chloride resin compositions from the viewpoint of easily manufacturing vinyl chloride resin compositions. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5446104 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to easily produce a flexible polyvinyl chloride resin composition by recycling a resin profile mainly composed of rigid polyvinyl chloride. [Means for solving the problem]

[0007] The present invention A method for producing a resin composition of flexible polyvinyl chloride using a resin profile mainly composed of rigid polyvinyl chloride as a raw material, A grinding step of grinding the aforementioned resin profile to form a pulverized material, The process includes a mixing step of kneading the pulverized material and pellets made of soft polyvinyl chloride while heating them to produce the resin composition in which the pulverized material and pellets are mixed, The aforementioned mixing step is A step of dispersing the pulverized material and the pellets, and kneading the pulverized material and the pellets to produce a mixture of the pulverized material and the pellets,The heating temperature of the mixture of the crushed material and the pellets At the first temperature A process of kneading while raising the temperature. The process involves kneading the mixture of the crushed material and the pellets while lowering the heating temperature from the first temperature to the second temperature, to have death, The first temperature is 160-200°C. The second temperature is at least 10°C lower than the first temperature. This is a method for producing a resin composition. [Effects of the Invention]

[0008] According to the present invention, a resin composition of flexible polyvinyl chloride can be easily produced by recycling a resin profile mainly composed of rigid polyvinyl chloride. [Brief explanation of the drawing]

[0009] [Figure 1] This flowchart shows the manufacturing procedure for the flexible polyvinyl chloride resin composition of this embodiment. [Figure 2] This diagram schematically shows the state of each stage in the manufacturing process of the flexible polyvinyl chloride resin composition of this embodiment. [Figure 3] This figure shows an example of a pulverized material that is kneaded by the heating kneader of this embodiment. [Figure 4] This figure shows another example of the resin profile of this embodiment. [Figure 5] These are the stress-strain curves for the comparative example and the example. [Modes for carrying out the invention]

[0010] One embodiment of a method for producing the resin composition of the present invention will be described with reference to the drawings. In the resin composition manufacturing method of this embodiment, a resin profile mainly composed of rigid polyvinyl chloride is used as a raw material to manufacture a resin composition of flexible polyvinyl chloride. This allows the manufactured resin profile to be reused, recycled into a new resin composition, and then a new resin composition to be generated.

[0011] Figure 1 is a flowchart showing the manufacturing procedure (process) of the flexible polyvinyl chloride resin composition of this embodiment. Figure 2 is a schematic diagram showing the state of each stage in the manufacturing process of the flexible polyvinyl chloride resin composition of this embodiment.

[0012] As shown in the figure, the discarded resin profile 10 (see Figure 2A) is recovered (S101 in Figure 1). The resin profile 10 is a profile (extruded profile) formed by resin extrusion molding. The resin is rigid polyvinyl chloride, and the resin profile 10 is a rigid polyvinyl chloride profile made of rigid polyvinyl chloride. The rigid polyvinyl chloride is polyvinyl chloride (PVC) without plasticizers, although other components (for example, various stabilizers and modifiers) may be mixed with the polyvinyl chloride. Note that Figure 2A shows a cross-section perpendicular to the longitudinal direction of the resin profile 10.

[0013] Here, the resin profile 10 is a molded resin product used in resin windows, which are building fixtures. A resin window has a resin frame and a sash that includes a resin frame, and the resin frame and resin frame are each made of the resin profile 10. In addition, the resin profile 10 is made from scraps of resin profile 10 from resin windows. The scraps of resin profile 10 are, for example, scraps from the resin window manufacturing site or scraps collected as market waste. On the other hand, the resin profile 10 may also be discarded resin profile 10.

[0014] Next, the recovered resin profile 10 is crushed by a crusher to form crushed resin profile 10 material 20 (see Figure 2B) (S102 in Figure 1). The crusher is, for example, an impact crusher. If the resin profile 10 is long or large, it is cut or otherwise modified to a size that can be crushed by the crusher before being crushed by the crusher. Alternatively, the resin profile 10 may be crushed in two stages. In this case, the resin profile 10 is roughly crushed by a first-stage coarse crusher, and then the coarse crushed material 20 is crushed into fine crushed material 20 by a second-stage fine crusher. In this way, crushed resin profile 10 material 20 is produced.

[0015] The resin molded article 10 is part of the raw material of a resin composition of soft polyvinyl chloride. Soft polyvinyl chloride is polyvinyl chloride mixed with a plasticizer and contains the plasticizer. Further, the resin composition is a composition having soft polyvinyl chloride as the main component and serves as the raw material for a molded article of soft polyvinyl chloride. The plasticizer is an additive that imparts flexibility to rigid polyvinyl chloride and softens rigid polyvinyl chloride.

[0016] Examples of the plasticizer include phthalate plasticizers such as dibutyl phthalate (DBP), diisodecyl phthalate (DIDP), bis(2-ethylhexyl) phthalate (DOP), butyl benzyl phthalate (BBP), diisononyl phthalate (DINP), etc.; aliphatic dibasic acid ester plasticizers such as tris(2-ethylhexyl) trimellitate (TOTM), bis(2-ethylhexyl) adipate (DOA), diisononyl adipate (DINA), dicyclohexyl adipate (DIDA), dibutyl sebacate (DBS), etc.; phosphate ester plasticizers such as tris(2-ethylhexyl) phosphate (TOP), triphenyl phosphate (TPP), etc.; or plasticizers such as polyesters and epoxidized soybean oil.

[0017] After the resin molded article 10 is pulverized, the pulverized material 20 of the resin molded article 10 and pellets 30 made of soft polyvinyl chloride containing a plasticizer (see FIG. 2C) are kneaded while being heated by a heat kneader to produce a resin composition of soft polyvinyl chloride in which the pulverized material 20 and the pellets 30 are mixed (S103 in FIG. 1). The heat kneader is, for example, a Banbury mixer, a kneader, or a Brabender, and applies a shearing force to the kneaded material during kneading. By the heat kneader, the pulverized material 20 and the pellets 30 are heated under predetermined temperature conditions and kneaded under the predetermined temperature conditions.

[0018] Pellet 30 is a granular material of flexible polyvinyl chloride molded into granules, and its main component is flexible polyvinyl chloride. Therefore, pellet 30 already contains plasticizers contained in flexible polyvinyl chloride. The resin composition is a mixture of crushed material 20 made of rigid polyvinyl chloride and pellet 30 made of flexible polyvinyl chloride, and is composed of flexible polyvinyl chloride. Flexible polyvinyl chloride is produced by mixing the rigid polyvinyl chloride contained in crushed material 20 and the flexible polyvinyl chloride contained in pellet 30.

[0019] Figure 3 shows an example of the crushed material 20 that is kneaded by the heating kneader of this embodiment. As shown in the figure, crushing the resin profile 10 forms crushed material 20 of various shapes and with a maximum dimension 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 used for kneading is 15 mm or less. Therefore, when crushing the resin profile 10, the resin profile 10 is crushed so that the maximum dimension R of the crushed material 20 is 15 mm or less. Alternatively, after crushing the resin profile 10, a separation device or the like is used to separate and remove the crushed material 20 with a maximum dimension R greater than 15 mm, and the crushed material 20 with a maximum dimension R of 15 mm or less is selected. The crushed material 20 with a maximum dimension R of 15 mm or less is kneaded with pellets 30.

[0020] The kneading of the crushed material 20 and the pellets 30 produces a mixture of the crushed material 20 and the pellets 30. By kneading the mixture of the crushed material 20 and the pellets 30, the rigid polyvinyl chloride of the crushed material 20 and the flexible polyvinyl chloride of the pellets 30 are mixed, and the plasticizer contained in the flexible polyvinyl chloride softens the rigid polyvinyl chloride. This produces flexible polyvinyl chloride.

[0021] By adjusting the ratio of pellets 30 to crushed material 20, the concentration of plasticizer contained in the flexible polyvinyl chloride resin composition and the hardness of the resin composition are adjusted. The concentration of plasticizer contained in pellets 30 varies. Therefore, the ratio of pellets 30 to crushed material 20 is adjusted in accordance with the concentration of plasticizer contained in pellets 30 to adjust the concentration of plasticizer contained in the resin composition to the target concentration. This adjusts the hardness of the resin composition to the target hardness.

[0022] The softening temperature of a resin is the temperature at which the resin begins to soften and deform (softening point). The softening temperatures of the crushed material 20 made of rigid polyvinyl chloride and the pellets 30 made of flexible polyvinyl chloride are different, with the softening temperatures of rigid polyvinyl chloride and the crushed material 20 being higher than those of flexible polyvinyl chloride and the pellets 30.

[0023] Therefore, when mixing the mixture of crushed material 20 and pellets 30, if the heating temperature of the mixture is suitable for mixing the flexible polyvinyl chloride and pellets 30 (low temperature), the pellets 30 will soften sufficiently and become easy to mix, but the crushed material 20 will not soften sufficiently and will be difficult to mix. As a result, the mixing of the mixture will not proceed smoothly. On the other hand, if the heating temperature of the mixture is suitable for mixing the rigid polyvinyl chloride and crushed material 20 (high temperature), the crushed material 20 will soften sufficiently and become easy to mix, but the pellets 30 will become too soft and will be difficult to mix. As a result, the mixing of the mixture will not proceed smoothly.

[0024] Therefore, when kneading the mixture of crushed material 20 and pellets 30, the heating temperature of the mixture is changed during kneading. Specifically, kneading is started, and the heating temperature of the mixture is increased while kneading is performed. During the kneading of the mixture, the heating temperature of the mixture is gradually increased to a predetermined temperature, thereby changing the viscosity of each part of the mixture (the part of crushed material 20, the part of pellets 30, and the part where crushed material 20 and pellets 30 are kneaded together), and the kneading is carried out to gradually knead the mixture uniformly.

[0025] Here, the mixing of the mixture is carried out by first performing a heating-increasing mixing process (heat-increasing mixing), and then performing a heating-increasing mixing process (cool-down mixing), while the heating temperature of the mixture is being lowered. In heating-increasing mixing, the heating temperature of the mixture is raised to a first temperature, and in cooling-down mixing, the heating temperature of the mixture is lowered from the first temperature to a second temperature lower than the first temperature. The mixture is kneaded by sequentially changing the heating temperature of the mixture of crushed material 20 and pellets 30 between the first and second temperatures.

[0026] The first temperature is suitable for mixing rigid polyvinyl chloride (crushed material 20) rather than flexible polyvinyl chloride (pellets 30), and the viscosity of the rigid polyvinyl chloride becomes suitable for mixing rigid polyvinyl chloride. When the heating temperature of the mixture is the first temperature, the rigid polyvinyl chloride of crushed material 20 becomes easier to mix than the flexible polyvinyl chloride of pellets 30. The second temperature is suitable for mixing flexible polyvinyl chloride rather than rigid polyvinyl chloride, and the viscosity of the flexible polyvinyl chloride becomes suitable for mixing flexible polyvinyl chloride. When the heating temperature of the mixture is the second temperature, the flexible polyvinyl chloride of pellets 30 becomes easier to mix than the rigid polyvinyl chloride of crushed material 20.

[0027] The first temperature is the temperature at which the heating of the kneaded material ends (heat-increasing kneading), and is between 160 and 200°C. The second temperature is the temperature at which the heating of the kneaded material ends (cool-down kneading), and is at least 10°C lower than the first temperature. Here, the first temperature is 190°C and the second temperature is 160°C. In the heating of the kneaded material, the heating temperature of the kneaded material is increased from 160°C to 190°C in 5 minutes. Therefore, the heating temperature of the kneaded material increases by 6°C per minute, and the heating rate of the kneaded material is 6°C / min. In the cooling of the kneaded material, the heating temperature of the kneaded material is decreased from 190°C to 160°C in 5 minutes. Therefore, the heating temperature of the kneaded material decreases by 6°C per minute, and the cooling rate of the kneaded material is 6°C / min.

[0028] When mixing the mixture of crushed material 20 and pellets 30, the mixing is started, and the heating temperature of the mixture is gradually increased, allowing for continuous mixing. This causes the heating temperature of the mixture to pass through the second temperature and rise to the first temperature, which is higher than the second temperature. In this way, in rising-temperature mixing, the mixture is kneaded while gradually increasing the heating temperature of the mixture to the first temperature. When the heating temperature of the mixture reaches the first temperature, the heating temperature increase is stopped. Subsequently, the process moves to cooling-temperature mixing, where the heating temperature of the mixture is gradually decreased from the first temperature to the second temperature while mixing is carried out. By performing rising-temperature mixing and cooling-temperature mixing in sequence, the viscosity of each part of the mixture is sequentially changed, and the mixture is kneaded until it becomes gradually uniform. Next, after the heating temperature of the mixture reaches the second temperature, the decrease in the heating temperature of the mixture is stopped, and the mixing of the mixture is completed.

[0029] After the production of the flexible polyvinyl chloride resin composition is completed by kneading the mixed materials, the molten resin composition is discharged from the heating kneader and passed between parallel rolls (S104 in Figure 1). At this time, the resin composition is compressed by passing it between the outer surfaces of two or more opposing rolls. Subsequently, the resin composition is extruded using an extrusion molding machine, and the extruded resin composition is sequentially cut to form flexible polyvinyl chloride pellets (S105 in Figure 1). After that, flexible polyvinyl chloride molded products are formed using the flexible polyvinyl chloride pellets (S106 in Figure 1). Flexible polyvinyl chloride molded products are, for example, airtight materials and gaskets used in building fixtures.

[0030] In the resin composition manufacturing method described above, the mixture of crushed material 20 and pellets 30 can be kneaded while increasing the heating temperature, allowing the mixture to be gradually kneaded uniformly. Therefore, a resin composition of flexible polyvinyl chloride can be easily manufactured by recycling a resin profile 10 mainly composed of rigid polyvinyl chloride. Furthermore, the hardness of the flexible polyvinyl chloride resin composition can be adjusted by adjusting the ratio of pellets 30 to crushed material 20 in accordance with the concentration of plasticizer contained in the pellets 30.

[0031] In addition to temperature-increasing kneading, which involves kneading the mixture while raising the heating temperature to a first temperature, cooling kneading, which involves kneading the mixture while lowering the heating temperature from the first temperature to a second temperature, allows for more uniform kneading of the mixture. When the resin profile 10 used as a raw material for the resin composition is scrap of resin profile 10 (in this case, resin profile 10 for a resin window), the scrap of resin profile 10 can be recycled to reduce the cost of the resin composition.

[0032] When heating the mixture of crushed material 20 and pellets 30 at a first temperature, if the first temperature is higher than 200°C, the viscosity of the rigid polyvinyl chloride in the crushed material 20 will decrease, which may make it difficult to mix the mixture. If the first temperature is lower than 160°C, the viscosity of the rigid polyvinyl chloride will increase, which may make it difficult to mix the mixture. In contrast, if the first temperature is within the range of 160 to 200°C (160°C or higher and 200°C or lower), the rigid polyvinyl chloride will have a viscosity that makes it easy to mix, allowing the mixing of the mixture to proceed smoothly.

[0033] When heating the mixture of crushed material 20 and pellets 30 at a second temperature, if the difference between the first and second temperatures is less than 10°C, the viscosity of the flexible polyvinyl chloride in the pellets 30 will decrease, which may make it difficult to knead the mixture. On the other hand, if the second temperature is 10°C or more lower than the first temperature, the flexible polyvinyl chloride will reach a viscosity that is easy to knead as the heating temperature of the mixture decreases from the first temperature to the second temperature, allowing the mixing of the mixture to proceed smoothly. The first temperature is more preferably 190°C, and the second temperature is more preferably 160°C. This allows the mixing of the mixture to proceed more smoothly.

[0034] When the maximum dimension R of the crushed material 20 of the resin profile 10 is greater than 15 mm, the larger size of the crushed material 20 may make it difficult to mix the crushed material 20 with the pellets 30. In contrast, when the maximum dimension R of the crushed material 20 is 15 mm or less, the crushed material 20 and pellets 30 can be dispersed and mixed smoothly. It is more preferable that the maximum dimension R of the crushed material 20 is 8 mm or less. This allows for smoother mixing of the crushed material 20 and pellets 30.

[0035] In this embodiment, the mixture is kneaded by raising the temperature, followed by kneading by lowering the temperature. However, if the mixture is uniformly kneaded by raising the temperature alone, the kneading by lowering the temperature may be omitted. In this case, the mixture is kneaded by raising the temperature while kneading, and the kneading process is completed. On the other hand, if the mixture is not sufficiently kneaded by raising the temperature alone, the mixture can be kneaded sufficiently by performing the raising and lowering temperature kneading in sequence.

[0036] Figure 4 shows another example of the resin profile 10 of this embodiment, and shows a cross-section perpendicular to the longitudinal direction of the resin profile 10. As shown in the figure, the resin profile 10 here has a main body 11 mainly composed of rigid polyvinyl chloride and an attachment 12 mainly composed of flexible polyvinyl chloride. The attachment 12 is a flexible part attached to the rigid main body 11, and is formed to be smaller than the main body 11 and protrudes from the main body 11. When crushing the resin profile 10 (S102 in Figure 1), the resin profile 10 with the attachment 12 attached to the main body 11 is crushed without removing the attachment 12 from the main body 11 to form crushed resin profile 10 material 20.

[0037] The resulting crushed material 20 includes crushed material 20 of only the main body 11, crushed material 20 of only the accessory part 12, and crushed material 20 containing both the main body 11 and the accessory part 12. The crushed material 20 is kneaded with pellets 30 to produce a flexible polyvinyl chloride resin composition. In this way, the resin profile 10 can be easily recycled without separating the main body 11, which is made of rigid polyvinyl chloride, from the accessory part 12, which is made of flexible polyvinyl chloride.

[0038] Next, examples and comparative examples of methods for producing flexible polyvinyl chloride resin compositions will be described, but the present invention is not limited to the following examples. In the examples, a flexible polyvinyl chloride resin composition was produced according to the flowchart shown in Figure 1. In this process, the mixture of crushed material 20 and pellets 30 was kneaded while increasing the heating temperature to a first temperature, and then the mixture was kneaded while decreasing the heating temperature from the first temperature to a second temperature to produce the resin composition. For comparison with the examples, in the comparative examples, only pellets 30 were kneaded to produce a flexible polyvinyl chloride resin composition.

[0039] [Table 1]

[0040] Table 1 shows the parts by weight (phr) of the crushed resin material 20 and the flexible polyvinyl chloride pellets 30 for one comparative example and seven examples (Examples 1 to 7). The parts by weight of the crushed material 20 and the pellets 30 are the parts by weight when the flexible polyvinyl chloride resin composition is set to 100 parts by weight, and the total is 100 parts by weight. Also, the pellets 30 used in the comparative example and Examples 1 to 7 are the same pellets 30.

[0041] Test specimens were prepared using the resin composition after manufacturing, and tensile tests were performed on the specimens. In the tensile tests, the test specimens were subjected to tensile testing in accordance with the Japanese Industrial Standard (JIS K 6251:2017) "Vulcanized rubber and thermoplastic rubber - Method for determining tensile properties," and the stress-strain curve (SS curve) of the test specimens was determined.

[0042] Figure 5 shows the stress-strain curves for the comparative example and Examples 1-7. The symbols H, F1, F2, F3, F4, F5, F6, and F7 attached to the eight stress-strain curves in Figure 5 correspond to the symbols shown in Table 1, indicating that they represent the stress-strain curves for the comparative example, Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, and Example 7, respectively. As shown in the figure, the tensile properties and degree of softening of the resin composition after manufacturing changed in correspondence with the ratio of crushed material 20 to pellets 30.

[0043] As described above, this embodiment discloses a method for producing the resin composition described in (1) to (5) below.

[0044] (1) A method for producing a resin composition of flexible polyvinyl chloride using a resin profile mainly composed of rigid polyvinyl chloride as a raw material, A grinding step of grinding the aforementioned resin profile to form a pulverized material, The process includes a mixing step of kneading the pulverized material and pellets made of soft polyvinyl chloride while heating them to produce the resin composition in which the pulverized material and pellets are mixed, The above mixing step is a method for producing a resin composition, comprising the step of kneading a mixture of the crushed material and the pellets while increasing the heating temperature. In the method for producing the resin composition described in (1), a resin composition of flexible polyvinyl chloride can be easily produced by recycling a resin profile mainly composed of rigid polyvinyl chloride.

[0045] (2) In the method for producing the resin composition described in (1), In the step of kneading while increasing the heating temperature, the kneaded mixture of the crushed material and the pellets is kneaded while increasing the heating temperature to a first temperature. A method for producing a resin composition, further comprising the step of kneading a mixture of the crushed material and the pellets while lowering the heating temperature from a first temperature to a second temperature. (2) In the method for producing the resin composition described above, the mixture of crushed material and pellets can be kneaded more uniformly.

[0046] (3) In the method for producing the resin composition described in (2), The first temperature is 160-200°C. A method for producing a resin composition, wherein the second temperature is 10°C or more lower than the first temperature. In the method for producing the resin composition described in (3), the mixing of the crushed material and the pellets can be carried out smoothly.

[0047] (4) In a method for producing a resin composition as described in any of (1) to (3), A method for producing a resin composition in which the maximum size of the pulverized material is 15 mm or less in the mixing step. In the method for producing the resin composition described in (4), the crushed material and pellets can be dispersed and the crushed material and pellets can be smoothly kneaded together.

[0048] (5) In a method for producing a resin composition as described in any of (1) to (4), A method for producing a resin composition, comprising grinding a resin profile having a main body made of rigid polyvinyl chloride and an attached part made of flexible polyvinyl chloride, in the grinding step. (5) In the method for producing the resin composition described above, the resin profile can be easily recycled without separating the main body from the attached parts of the resin profile. [Explanation of Symbols]

[0049] 10... Resin profiles, 11... Main body, 12... Accessories, 20... Crushed material, 30... Pellets, R... Maximum dimensions.

Claims

1. A method for producing a resin composition of flexible polyvinyl chloride using a resin profile mainly composed of rigid polyvinyl chloride as a raw material, A grinding step of grinding the aforementioned resin profile to form a pulverized material, The process includes a mixing step of kneading the pulverized material and pellets made of soft polyvinyl chloride while heating them to produce the resin composition in which the pulverized material and pellets are mixed, The mixing step includes: dispersing the pulverized material and the pellets and kneading the pulverized material and the pellets to produce a mixture of the pulverized material and the pellets; kneading the mixture of the pulverized material and the pellets while increasing the heating temperature to a first temperature; and kneading the mixture of the pulverized material and the pellets while decreasing the heating temperature from the first temperature to a second temperature. The first temperature is 160 to 200°C. A method for producing a resin composition, wherein the second temperature is 10°C or more lower than the first temperature.

2. In the method for producing the resin composition described in claim 1, A method for producing a resin composition in which the maximum size of the pulverized material is 15 mm or less in the mixing step.

3. In a method for producing a resin composition according to claim 1 or 2, A method for producing a resin composition, comprising grinding a resin profile having a main body made of rigid polyvinyl chloride and an attached part made of flexible polyvinyl chloride, in the grinding step.

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