Method for manufacturing recycled resin and method for manufacturing molded articles

Abstract

To separate a desired resin with a high purity from a resin composition containing two or more kinds of thermoplastic resins.SOLUTION: There is provided a manufacturing method for a recycled resin. The manufacturing method comprises the steps of: melting a resin composition containing a recycling resin A and a resin B having a higher melting point than the recycling resin A using an extruder; and subjecting the molten resin composition to treatment with a filter attached to a tip region of the extruder to separate the recycling resin A from the resin composition. The recycling resin A and the resin B are thermoplastic resins. A mesh opening of the filter used for filter treatment is large enough to inhibit passage of the resin B. A temperature of the resin composition when subjected to treatment with the filter is set to be equal to or higher than a melting point of the recycling resin A and lower than a melting point of the resin B, and a heating temperature of the extruder is set to be lower than the melting point of the resin B by 20°C or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for producing recycled resin. Furthermore, this invention relates to a method for producing a molded article using recycled resin. [Background technology]

[0002] Many packaging materials use thermoplastic composite materials and / or laminated materials. Packaging materials are molded into, for example, bottle containers and refill pouches. For functional reasons, packaging materials may be composed of completely different types of resin films. When packaging materials made of completely different types of resin films are recovered and the resin is recycled, the recycled resin contains the main polymer component and polymers that are incompatible with it. For example, polyethylene recycled from recovered pouches contains unmelted polyamide and polyethylene terephthalate (hereinafter also referred to as "PET"). Because polyamide and PET result in heterogeneous blends, the moldability of recycled resin is significantly reduced compared to virgin polyethylene. In particular, unmelted polyamide and PET are incompatible with polyethylene and are large in size, so they greatly affect the moldability of recycled resin.

[0003] Therefore, as a method for separating recycled resin from other resins, the methods described in, for example, Patent Documents 1 to 3 have been proposed. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2007-62070 [Patent Document 2] Japanese Patent Publication No. 2019-6043 [Patent Document 3] U.S. Patent Application Publication No. 2019 / 366591 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the methods proposed in Patent Documents 1 to 3 described above, there is a limit to separating the target resin for recycling with high purity. Therefore, an object of the present invention is to provide a method capable of separating a target resin from a resin composition containing two or more types of thermoplastic resins with high purity.

Means for Solving the Problems

[0006] The present invention melts a resin composition containing a resin A for recycling and a resin B having a melting point higher than that of the resin A for recycling by an extruder, and relates to a method for producing a resin for recycling, including a step of subjecting the melted resin composition to treatment with a filter attached to the tip region of the extruder to separate the resin A for recycling from the resin composition. In one embodiment, it is preferable that the resin A for recycling and the resin B are thermoplastic resins. In one embodiment, it is preferable that the aperture of the filter used for the treatment with the filter is such that it inhibits the passage of the resin B. In one embodiment, when the resin composition is subjected to treatment with the filter, the temperature is set to be not lower than the melting point of the resin A for recycling and lower than the melting point of the resin B, and it is preferable that the heating temperature of the extruder is set to be 20°C or more lower than the melting point of the resin B.

[0007] The present invention also relates to a method for producing a molded article, including a step of producing a resin for recycling and a step of molding using the resin for recycling.

Effects of the Invention

[0008] U EAccording to the present invention, a target resin can be separated from a resin composition containing two or more types of thermoplastic resins with high purity.

Embodiments for Carrying Out the Invention

[0009] The present invention will be described based on its preferred embodiments. The present invention relates to a method for producing a recycled resin, which includes a step of melting a resin composition containing a recycled resin and a step of separating the recycled resin from the resin composition.

[0010] First, the resin composition, which is the target for separating the recycled resin, will be described. The resin composition contains a recycled resin A and a resin B having a melting point higher than that of the recycled resin A. In the present invention, from the viewpoint of separating the target resin from the resin composition, it is preferable that both the recycled resin A and the resin B are thermoplastic resins.

[0011] Examples of the thermoplastic resin include polyolefin, polyamide, polyester, vinyl chloride, styrene, vinyl ether, polyvinyl alcohol, polycarbonate, polysulfone, and the like. Examples of the polyolefin include polyethylene, polypropylene, and the like. Examples of the polyamide include polycaproamide (polyamide-6), polyhexamethylene adipamide (polyamide-66), polycaproamide / polyhexamethylene adipamide copolymer (polyamide-6 / 66), polytetramethylene adipamide (polyamide-46), polyhexamethylene sebacamide (polyamide-610), polyhexamethylene dodecamide (polyamide-612), polyundecamide (polyamide-11), polydodecamide (polyamide-12), polyhexamethylene adipamide / polyhexamethylene terephthalamide copolymer (polyamide-66 / 6T), and the like. Examples of the polyester include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and the like. These can be used alone or in combination of two or more.

[0012] In this invention, any thermoplastic resins can be selected as recycled resin A and resin B, provided that resin B has a higher melting point than recycled resin A. Recycled resin A may be one type of resin or two or more types of resins with different melting points. Similarly, resin B may be one type of resin or two or more types of resins with different melting points. For example, consider a resin composition containing resins R1, R2, and R3, each with different melting points, in the order of increasing melting point of R1, R2, and R3. In this case, if resin R1 is selected as recyclable resin A, then resins R2 and R3 can be selected as resin B. If resin R2 is selected as recyclable resin A (in which case resin R1 is also selected), then resin R3 is selected as resin B. Even if the resin composition contains four or more types of resins, recyclable resins A and B can be selected according to the same reasoning. Which of the resins contained in the resin composition corresponds to recyclable resin A is determined by the temperature at which the resin composition is melted. All resins with a melting point below that temperature correspond to recyclable resin A. On the other hand, all resins with a melting point above that temperature correspond to resin B.

[0013] As described below, the manufacturing method of the present invention involves adjusting the temperature of the resin composition subjected to filter treatment so that it is higher than the melting point of the resin with the lowest melting point among the resins contained in the resin composition, thereby producing the regenerative resin by separating it from the resin composition. For this reason, in the present invention, it is preferable that the melting points of regenerative resins A and B contained in the resin composition are within a predetermined range. Specifically, the melting point of regenerative resin A is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. Alternatively, the melting point of regenerative resin A is preferably 200°C or lower, more preferably 180°C or lower, even more preferably 160°C or lower, and even more preferably 140°C or lower. A melting point of regenerative resin A of 80°C or higher allows the separated regenerative resin A to have sufficient moldability and mechanical properties such as elasticity, thereby expanding the recycling applications of regenerative resin A. A melting point of regenerative resin A of 200°C or lower makes it easier to differentiate it from the melting point of resin B, allowing regenerative resin A to be separated from the resin composition with high purity. If recycled resin A contains two or more resins with different melting points, the melting point of recycled resin A is the melting point of the resin with the highest melting point. If resin B contains two or more resins with different melting points, the melting point of resin B is the melting point of the resin with the lowest melting point.

[0014] The melting point of resin B is preferably 200°C or higher, more preferably 210°C or higher, and even more preferably 220°C or higher. Alternatively, the melting point of resin B is preferably 300°C or lower, more preferably 290°C or lower, and even more preferably 280°C or lower. Having a melting point of resin B of 200°C or higher makes it easier to differentiate it from the melting point of recycled resin A, allowing recycled resin A to be separated from the resin composition with high purity. Having a melting point of resin B of 300°C or lower helps to suppress the degradation of recycled resin A in the resin composition when the resin composition is melt-kneaded.

[0015] From the viewpoint of separating the regenerative resin A from the resin composition with high purity, it is also preferable that the difference between the melting point of regenerative resin A and the melting point of resin B is within a predetermined range. Specifically, the difference between the melting point of regenerative resin A and the melting point of resin B is preferably 20°C or more, more preferably 40°C or more, even more preferably 60°C or more, and even more preferably 80°C or more. Furthermore, the difference between the melting point of regenerative resin A and the melting point of resin B is preferably 200°C or less, more preferably 180°C or less, even more preferably 160°C or less, even more preferably 140°C or less, even more preferably 120°C or less, and particularly preferably 110°C or less. A difference of 20°C or more between the melting point of regenerative resin A and the melting point of resin B makes it easier to create a difference between the melting points of regenerative resin A and resin B, and allows for the separation of regenerative resin A from the resin composition with high purity. By having a difference of 200°C or less between the melting point of recycled resin A and the melting point of resin B, it becomes easier to control the melting temperature of the resin composition, and the productivity of recycled resin A is improved.

[0016] Examples of recyclable resin A having the above composition include polyethylene, polypropylene, polyolefins such as ethylene-α-olefin copolymers, acrylonitrile-styrene copolymers, acrylonitrile-butadiene-styrene copolymers, and polymethyl methacrylate. Of these resins, from the viewpoint of separating recyclable resin A from a resin composition with high purity, it is preferable that the recyclable resin A is a polyolefin. Among polyolefins, from the viewpoint of easily creating a difference between the melting point of recyclable resin A and resin B in the resin composition, and separating recyclable resin A from the resin composition with high purity, it is particularly preferable that the polyolefin is polyethylene. Furthermore, when polyethylene is used as the recycled resin A, it is preferable to use polyesters such as PET, PTT, PBT, PEN, and PBN, as well as polyamides such as polyamide 6, polyamide 66, polyamide 6 / 66, polyamide 46, polyamide 610, polyamide 612, polyamide 11, polyamide 12, and polyamide 66 / 6T (hereinafter also referred to as "PA") as the resin B, in relation to the melting point of polyethylene.

[0017] From the viewpoint of separating the regenerative resin A from the resin composition with high purity, it is also preferable that the content of the regenerative resin A in the resin composition is within a predetermined range. Specifically, the content of the regenerative resin A is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the mass of the resin composition. Furthermore, the content of the regenerative resin A is preferably 99% by mass or less, more preferably 95% by mass or less, and even more preferably 90% by mass or less, based on the mass of the resin composition. When the content of the regenerative resin A is 30% by mass or more, clogging of the filter is less likely to occur when the resin composition is subjected to filtration (i.e., filtration), so the increase in pressure applied to the resin composition can be suppressed, and thereby the regenerative resin A can be separated from the resin composition with high purity. When the content of the regenerative resin A is 99% by mass or less, the regenerative resin A can be easily separated from the resin composition with high purity. If recycled resin A contains two or more different types of resins, the content of recycled resin A refers to the total content of recycled resin A in the resin composition.

[0018] From the viewpoint of separating the recyclable resin A from the resin composition with high purity, it is also preferable that the content of resin B in the resin composition is within a predetermined range. Specifically, the content of resin B is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, relative to the mass of the resin composition. Furthermore, the content of resin B is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, relative to the mass of the resin composition. When the content of resin B is 1% by mass or more, the recyclable resin A can be easily separated from the resin composition with high purity. When the content of resin B is 50% by mass or less, clogging of the filter is less likely to occur when the resin composition is subjected to filter treatment, so the increase in pressure applied to the resin composition can be suppressed, and thereby the recyclable resin A can be separated from the resin composition with high purity. If resin B contains two or more different types of resins, the content of resin B refers to the total content of resin B in the resin composition.

[0019] Furthermore, from the viewpoint of separating the regenerative resin A from the resin composition with high purity, it is also preferable that the ratio of the content of regenerative resin A to the content of resin B in the resin composition is within a predetermined range. Specifically, the content of resin B in the resin composition is preferably 1 part by mass or more, more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, per 100 parts by mass of regenerative resin A. Also, the content of resin B in the resin composition is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less, per 100 parts by mass of regenerative resin A. By having a resin B content of 1 part by mass or more per 100 parts by mass of regenerative resin A, regenerative resin A can be easily separated from the resin composition with high purity. By ensuring that the content of resin B in the resin composition is 50 parts by mass or less per 100 parts by mass of recycled resin A, clogging of the filter is less likely to occur when the resin composition is subjected to filtration. This suppresses the increase in pressure applied to the resin composition, thereby enabling the separation of recycled resin A from the resin composition with high purity.

[0020] In the present invention, the resin composition may further contain a thermosetting resin C in addition to the recycled resin A and resin B described above. Since thermosetting resin C does not melt, the inclusion of thermosetting resin C in the resin composition makes it easier to recover the thermosetting resin C with a filter, and allows for the separation of recycled resin A from the resin composition with high purity. Examples of thermosetting resin C include urethane resin, epoxy resin, phenolic resin, furan resin, etc. These can be used individually or in combination of two or more types.

[0021] When the resin composition contains thermosetting resin C, it is also preferable that the total amount of resin B and thermosetting resin C in the resin composition is within a predetermined range, from the viewpoint of preventing clogging of the filter when the resin composition is subjected to filtration. Specifically, the total amount of resin B and thermosetting resin C is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more, relative to the resin composition. Furthermore, the total amount of resin B and thermosetting resin C is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, relative to the resin composition. When the total amount of resin B and thermosetting resin C is 10% by mass or more, it becomes easier to recover resin B and thermosetting resin C when the resin composition is subjected to filtration, and the regenerative resin A can be efficiently separated from the resin composition with high purity. By ensuring that the total amount of resin B and thermosetting resin C is 50% by mass or less, clogging of the filter is less likely to occur when the resin composition is subjected to filter treatment. This suppresses the increase in pressure applied to the resin composition, thereby enabling the separation of regenerative resin A from the resin composition with high purity. If thermosetting resin C contains two or more different types of resins, the content of thermosetting resin C refers to the total content of thermosetting resin C in the resin composition.

[0022] Furthermore, if the resin composition contains thermosetting resin C, the content of thermosetting resin C is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 4% by mass or more, relative to the mass of the resin composition. Also, the content of thermosetting resin C is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, relative to the mass of the resin composition. Since thermosetting resin C does not melt, a content of 1% by mass or more of thermosetting resin C makes it easier to recover the thermosetting resin C with a filter, and allows for the separation of regenerative resin A from the resin composition with high purity. A content of thermosetting resin C of 20% by mass or less makes it less likely for the filter to clog when the resin composition is subjected to filter processing, thereby suppressing the increase in pressure applied to the resin composition, and thereby allowing for the separation of regenerative resin A from the resin composition with high purity.

[0023] In the present invention, a resin for recycling is separated from a resin composition having the above-mentioned resin. As the resin composition, for example, used refill pouches, food retort pouches, detergent bottles, and other resin products can be recovered and preferably washed, dried, and crushed as needed. The resin recovered in this way may be used as is in the manufacturing method of the present invention. Alternatively, the recovered resin may be molded into pellets or the like by a known method such as melt kneading before being used in the manufacturing method of the present invention.

[0024] Used resin products that can be used as resin compositions typically have a laminated structure in which multiple sheet materials are stacked. Preferably, the resin product consists of a laminate with at least four layers, comprising at least a heat seal layer, a barrier layer, a printing layer, and a substrate layer. The heat seal layer forms the innermost layer of the resin product. The heat seal layer contains a thermoplastic resin such as polyethylene. In other words, the heat seal layer corresponds to the recycled resin A contained in the resin composition described above. The barrier layer is adjacent to the heat seal layer. The barrier layer contains a film on which inorganic materials such as metallic aluminum have been deposited or sputtered. In other words, the barrier layer is derived from components different from the recycled resin A, resin B, and thermosetting resin C mentioned above. The printed layer is adjacent to the side of the barrier layer opposite to the side facing the heat seal layer. The printed layer contains a thermosetting resin such as ink. In other words, the printed layer corresponds to the thermosetting resin C contained in the resin composition described above. The substrate layer is adjacent to the side of the printed layer opposite to the side facing the barrier layer. The substrate layer contains a thermoplastic resin, such as PET and / or PA, which has a higher melting point than the thermoplastic resin contained in the heat seal layer. In other words, the substrate layer corresponds to resin B contained in the resin composition described above. Such resin products, for example, have a barrier layer and a printed layer, and a barrier layer and a heat-seal layer, joined together by an adhesive.

[0025] When, for example, a used resin product is used as the resin composition, the resin composition contains various components in addition to the thermoplastic resins such as the recycled resin A and resin B mentioned above, and the thermosetting resin C. Even in this case, according to the present invention, recycled resin A can be separated from the resin composition with high purity. Examples of various components include laminating agents; inorganic substances such as metallic aluminum, alumina, and silicon dioxide; printing inks and pigments; and other additives. Other additives include, for example, plasticizers; nucleating agents; fillers (inorganic fillers, organic fillers); hydrolysis inhibitors; flame retardants; antioxidants; lubricants such as hydrocarbon waxes and anionic surfactants; UV absorbers; antistatic agents; antifogging agents; light stabilizers; pigments; fungicides; antibacterial agents; foaming agents; surfactants; polysaccharides such as starches, alginic acid, and cellulose fibers; natural proteins such as gelatin, glue, and casein; inorganic compounds such as tannins, zeolites, ceramics, and metal powders; fragrances; flow regulators; leveling agents; conductive agents; UV dispersants; and deodorizers. These can be used individually or in combination of two or more types.

[0026] When the resin composition contains various components, the content of each component is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, even more preferably 2% by mass or less, and even more preferably 0% by mass, relative to the mass of the resin composition. From the viewpoint of separating the regenerative resin A from the resin composition with high purity, the lower the content of each component in the resin composition, the better.

[0027] Next, the manufacturing method of the present invention will be described. The manufacturing method of the present invention includes a step of melting a resin composition containing a recyclable resin, and a step of separating the recyclable resin from the resin composition. The manufacturing method of the present invention also includes an extrusion step of supplying the resin composition to a kneading device in order to melt the resin composition.

[0028] In detail, first, a resin composition is prepared from which the recyclable resin is to be separated. As described above, the resin composition contains recyclable resin A and resin B having a higher melting point than recyclable resin A. The resin composition may further contain the thermosetting resin C and various other components as described above. If polyethylene is used as the recyclable resin A contained in the resin composition, then resin B can be, for example, PET and / or PA, and thermosetting resin C can be, for example, polyurethane.

[0029] Before supplying the resin composition to the kneading apparatus described later, the resin composition may be pulverized as needed. Pulverization can be carried out, for example, using a pulverizer or other pulverizing device. One way to easily achieve the separation of recyclable resin A with high purity is to make the size of the foreign matter contained in the resin composition greater than a predetermined value. Recyclable resin A is recovered, for example, by subjecting the resin composition to filtration. If the foreign matter has a certain size, it becomes difficult for the foreign matter to pass through the filter, and the recyclable resin A and the foreign matter can be easily separated. For this reason, it is preferable to grind the resin composition so that the particle size is 3 mm or more, more preferably 5 mm or more, and even more preferably 10 mm or more. The larger the particle size of the resin composition, the better, but the desired effect can be sufficiently achieved if it is about 20 mm in size.

[0030] The particle size of the resin composition after grinding (hereinafter also referred to as "ground particle size of the resin composition") can be measured by the following method. Specifically, first, the resin composition fragments are collected from the pulverizer. The resin composition fragments are photographed at 500x magnification using an optical microscope, and the area of ​​the photographed fragments is measured. The equivalent diameter of a circle is calculated from this area. This measurement is performed on any 100 resin composition fragments. The arithmetic mean of the obtained equivalent diameters of circles is taken as the pulverized particle size of the resin composition. The pulverized particle size of the resin composition generally coincides with the mesh opening of the pulverizer's screen.

[0031] Next, the resin composition is supplied to a resin mixing device for recycling. Any mixing device commonly used for the melt-mixing of this type of resin can be used without particular limitations. Typically, the mixing device comprises a hopper for supplying the resin composition, an extruder for extruding the resin composition while melt-mixing it, and a die. Examples of such mixing devices include closed-type kneaders, single-screw or twin-screw kneaders, and continuous kneaders such as open-roll type kneaders.

[0032] After supplying the resin composition, the resin composition is melted by an extruder. As described above, in order to separate the regenerative resin A with high purity, it is effective to make the size of the foreign matter contained in the resin composition greater than a predetermined value, and this size can also be controlled by the temperature at which the resin composition is melted.

[0033] Specifically, the temperature at which the resin composition is melted, i.e., the heating temperature of the extruder, is preferably the same as or higher than the melting point of the regenerative resin A. More specifically, the heating temperature of the extruder is preferably the same as or 10°C or more higher than the melting point of the regenerative resin A, more preferably 30°C or more higher, and even more preferably 50°C or more higher. By setting the heating temperature of the extruder 10°C or more higher than the melting point of the regenerative resin A, the regenerative resin A in the resin composition can be effectively melted, and when the resin composition is subjected to filtration, it becomes possible to separate the regenerative resin A from the resin composition with high purity.

[0034] Furthermore, it is preferable that the heating temperature of the extruder be lower than the melting point of resin B. Specifically, it is preferable that the heating temperature of the extruder be 20°C or more lower than the melting point of resin B, more preferably 50°C or more lower, and even more preferably 80°C or more lower. By setting the heating temperature of the extruder to be 20°C or more lower than the melting point of resin B, only the regenerative resin A in the resin composition can be effectively melted, and when the resin composition is subjected to filtration, it becomes possible to separate the regenerative resin A from the resin composition with high purity. In other words, it is preferable that the molten resin composition contains molten regenerative resin A and unmolten resin B.

[0035] In this way, the resin composition is melted by an extruder. This yields a resin composition in which the recycled resin A is melted, but resin B is not. If the resin composition contains thermosetting resin C, solid thermosetting resin C is present in the molten resin composition. If the resin composition contains the various components, the manner in which the various components exist in the molten resin composition differs depending on the type of component. The various components may be, for example, liquids or solids.

[0036] Next, the molten resin composition is subjected to filtration. This filtration can be carried out using a filter attached to the tip of the extruder. This filtration separates the regenerative resin A from the resin composition.

[0037] One of the characteristics of the manufacturing method of the present invention is that the temperature of the resin composition when subjected to filter treatment is within a predetermined range. In methods for separating recycled resin from other resins, there is a need to separate the recycled resin with high purity in order to improve the moldability of the film produced using the recycled resin. However, if a resin composition containing recycled resin is simply melted at a high temperature, impurities contained in the resin composition will also melt. As a result, even if the molten resin composition is subsequently subjected to filtration, impurities are separated in addition to the recycled resin, making it difficult to separate the recycled resin with high purity. In order to improve this point, the inventors diligently investigated and discovered that, unexpectedly, by adjusting the temperature of the resin composition according to the melting point of the regenerative resin to be separated from the resin composition and the melting point of other resins, it is possible to separate the regenerative resin from the resin composition with high purity, even when the molten resin composition is subjected to filtration.

[0038] Temperature T when the resin composition is subjected to filter treatment. F It is preferable to adjust the temperature T according to the melting points of the recycled resin A and the resin B. Specifically, the temperature T FIt is preferable that it be not less than the melting point of the resin A for recycling and less than the melting point of the resin B. Let the melting point of the resin A for recycling be T A and the melting point of the resin B be T B . When these melting points are such that the difference in melting points ΔT (= T B - T A ), it is preferably 60°C or higher, more preferably 80°C or higher, and still more preferably 100°C or higher. Thereby, a resin composition in which the resin A for recycling is effectively melted compared to the resin B can be obtained, and when the resin composition is subjected to treatment with a filter, the resin A for recycling can be separated from the resin composition with high purity. For this reason, the greater the difference in melting points ΔT, the more preferable it is, but the desired effect is sufficiently achieved if it is increased to about 180°C. For the same reason as described above, the temperature T F is preferably 20°C or lower, more preferably 30°C or lower, and still more preferably 50°C or lower than the melting point T B of the resin B. For the same reason as described above, the temperature T[[ID=I5]] F is preferably lower than the melting point T A as long as it is T B or higher, and the lower it is compared to the melting point T B , the more preferable it is, but the desired effect is sufficiently achieved if it is decreased to about 90°C compared to the melting point T When the resin composition is subjected to treatment with a filter, suppressing the increase in pressure applied to the resin composition and improving the productivity of the resin A for recycling, the temperature T F is preferably 30°C or higher, more preferably 40°C or higher, and still more preferably 50°C or higher than the melting point T A of the resin A for recycling. For this reason, the higher the temperature T F is compared to the melting point T A , the more preferable it is. These desired effects are sufficiently achieved if the temperature T F is increased to about 100°C compared to the melting point T B on the condition that it is less than T A .

[0039] The temperature T F when the resin composition is subjected to treatment with a filterThe melting point T of recycled resin A A The above describes the melting point T of resin B. B To make it less than the limit, the filter is heated to a temperature T L It is preferable to set the temperature within a predetermined range. Specifically, the heating temperature of the filter T L The melting point T of resin B B It is preferable that the temperature is 20°C or more lower than the specified temperature, more preferably 30°C or more lower, and even more preferably 50°C or more lower. Filter heating temperature T L The melting point T of resin B B It should be at least 90°C lower than that. For the same reasons as above, the heating temperature of the filter T L The melting point T of recycled resin A A It is preferable that the temperature is 30°C or more higher than the specified temperature, more preferably 40°C or more higher, and even more preferably 50°C or more higher. Filter heating temperature T L The melting point T of recycled resin A A It just needs to be at least 100°C higher than that. When the filter is heated, the filter temperature T L The temperature T of the resin composition subjected to the filtering process. F They generally agree.

[0040] Temperature T when the resin composition is subjected to filter treatment. F This refers to the temperature of the resin composition when it is extruded by the extruder, in other words, the set temperature T of the extruder. S It may be the same as, or it may be different from, [the other thing].

[0041] The manufacturing method of the present invention is also characterized by setting the mesh size of the filter used for processing with the filter to a size that inhibits the passage of resin B. That is, it is preferable that the mesh size of the filter is larger than the particle size of resin B. By configuring the filter in this way, when a resin composition in which the regenerative resin A is effectively melted compared to resin B is subjected to processing with the filter, the regenerative resin A can pass through the mesh size of the filter, but the resin B cannot. The resin B whose passage is inhibited can also be discharged from the filter using a different route from the regenerative resin A. As a result, it is possible to separate the regenerative resin A from the resin composition with high purity.

[0042] The mesh size of the filter is preferably 70% or less of the maximum dispersed particle size of resin B, more preferably 50% or less, and more preferably 30% or less. This allows for the effective separation of the regenerative resin A from the resin composition with high purity. Furthermore, the mesh size of the filter is preferably 3% or more of the maximum dispersed particle size of resin B, more preferably 6% or more, and even more preferably 10% or more. This makes it easy to set the difference D between the pressure P and the maximum point stress, which will be described later, within a predetermined range.

[0043] As described above, in order to separate the recyclable resin A with high purity, it is effective to make the size of the foreign matter contained in the resin composition greater than a predetermined value, and this size can also be controlled by making the maximum dispersed particle size of resin B greater than a predetermined value. Specifically, the maximum dispersed particle size of resin B is preferably 1 mm or larger, more preferably 2 mm or larger, even more preferably 3 mm or larger, and even more preferably 6 mm or larger. For the same reasons as above, the larger the maximum dispersed particle size of resin B, the better, but the desired effect is sufficiently achieved if it is about 20 mm in size. Furthermore, the maximum dispersed particle size of the thermosetting resin C is preferably 1 mm or larger, more preferably 2 mm or larger, even more preferably 3 mm or larger, and even more preferably 6 mm or larger. For the same reasons as above, the larger the maximum dispersed particle size of the thermosetting resin C, the better, but the desired effect is sufficiently achieved if it is about 20 mm in size. Furthermore, if the resin composition contains resin B and thermosetting resin C, it is sufficient that the maximum dispersed particle size of at least one of these resins is 1 mm or larger.

[0044] The maximum dispersed particle size of the resin can be measured by the following method. Specifically, first, in the process of subjecting the resin composition to filter treatment, a sample of the molten resin composition is taken from a position immediately before the filter. Separately, two mirror-finish metal plates (made of iron) with flat surfaces are prepared. A heat-resistant imide film is laid over the entire surface of one of the mirror-finish metal plates, and approximately 10 g of the sampled resin composition is placed in the center of the heat-resistant imide film. The resin composition is surrounded by a metal spacer (made of iron) with a 20 cm square cavity inside and a thickness of 0.4 mm. The other mirror-finish metal plate, which already has the heat-resistant imide film laid on it, is then placed on top of this so that the heat-resistant imide film is in contact with the resin composition, thereby obtaining a sample in which the resin composition is sandwiched between the mirror-finish metal plates. Next, the sample is placed on the plate of a press machine (Toyo Seiki Seisakusho Co., Ltd., Lab Press P2-30T), and pressed at 200°C and 0.4 MPa for 2 minutes, and then pressed again at 20 MPa for 2 minutes. Subsequently, the sample is compressed at 15°C and 0.4 MPa for 1 minute to cool and obtain a press sheet. One side of the press sheet is photographed with an optical microscope at 5000x magnification, and the area of ​​the captured resin is measured. The equivalent diameter of a circle is calculated from this area. The measurement is performed on any 100 resin samples. The largest particle size among the measured particles is defined as the maximum dispersed particle size of the resin. If the resin composition contains two or more resins other than the recycled resin A, the maximum dispersed particle size obtained by the method described above shall be used as the maximum dispersed particle size of the resin, without distinguishing between the two or more resins.

[0045] The maximum dispersed particle size of resin B can be adjusted by, for example, the extruder's set temperature, the screw's L / D ratio and compression ratio, and the residence time of the resin composition. Alternatively, it can be adjusted by the type of extruder. When using a single-screw or twin-screw extruder, for example, with a full-flight screw, the maximum dispersed particle size of resin B generally tends to be large. Therefore, when melt-kneading a resin composition using such an extruder, the maximum dispersed particle size of resin B can be increased to a predetermined value or higher by lowering the heating temperature of the extruder by 20°C or more below the melting point of resin B. When using a twin-screw extruder, for example, one equipped with a kneader, the maximum dispersed particle size of resin B generally tends to be small. Therefore, when melt-kneading a resin composition using such an extruder, the maximum dispersed particle size of resin B can be increased to a predetermined value or higher by setting the heating temperature of the resin composition immediately before the filter (the set heating temperature of the filter immediately before the resin composition passes through the filter) to be 100°C or more lower than the melting point of resin B.

[0046] The mesh size of the filter is preferably 1500 μm or less, more preferably 1200 μm or less, even more preferably 900 μm or less, even more preferably 800 μm or less, and even more preferably 600 μm or less. This allows for the separation of the regenerative resin A from the resin composition with high purity. Alternatively, the mesh size of the filter is preferably 60 μm or more, more preferably 90 μm or more, even more preferably 120 μm or more, even more preferably 250 μm or more, and even more preferably 400 μm or more. As the mesh size of the filter decreases, the opening ratio of the filter also decreases. By setting the mesh size of the filter to the above values ​​or higher, clogging of the filter that may occur due to an excessively small opening ratio can be suppressed. Furthermore, since the resin composition has a certain viscosity, the increase in pressure applied to the resin composition when it is subjected to filtration can be suppressed, making it more difficult for foreign matter to pass through the filter. Considering the above, the mesh opening of the filter is preferably 60 μm to 1500 μm, more preferably 90 μm to 1200 μm, even more preferably 120 μm to 900 μm, even more preferably 250 μm to 800 μm, and even more preferably 400 μm to 600 μm.

[0047] In the step of subjecting the resin composition to filtration, it is also preferable to set the pressure P (resin pressure) applied to the resin composition within a predetermined range. Specifically, it is preferable to set the pressure P lower than the maximum point stress of resin B during filtration. By setting such a pressure, it is possible to suppress the separation of resin B in addition to the recycled resin A, as unmelted resin B may be forcibly pushed out and pass through the filter when the resin composition is subjected to filtration. If resin B contains two or more resins with different maximum point stresses, the maximum point stress of resin B refers to the maximum point stress of the resin with the lowest melting point. "Pressure P applied to the resin composition" refers to the pressure applied to the resin composition immediately before it passes through the filter. The pressure P can be measured by the method described in the examples below. "The maximum point stress of resin B during processing with the filter" refers to the filter heating temperature T. L This refers to the maximum point stress of resin B in the given location. The "maximum point stress" can be measured using a bending tester with a constant temperature chamber, in accordance with JIS K7171. Details of the measurement method are described in the examples below.

[0048] Another means of easily achieving the separation of the regenerative resin A with high purity is to set the difference D between the pressure P and the maximum point stress within a predetermined range. This is because it is possible to suppress the separation of resin B in addition to regenerative resin A. For this reason, the difference D is preferably 1 MPa or more, more preferably 2 MPa or more, and even more preferably 4 MPa or more. Also, the difference D is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less. When the difference D is 1 MPa or more, when the resin composition is subjected to filtration, it is possible to suppress the separation of resin B in addition to regenerative resin A by preventing unmelted resin B from being forcibly pushed out and passing through the filter. When the difference D is 20 MPa or less, it is possible to separate the regenerative resin A from the resin composition with high purity and improve the productivity of the regenerative resin A by sufficiently pushing out the resin composition.

[0049] The pressure P is preferably 1 MPa or higher, more preferably 2 MPa or higher, and even more preferably 4 MPa or higher, from the viewpoint of suppressing the separation of resin B in addition to regenerative resin A and improving the productivity of regenerative resin A. Furthermore, the pressure P is preferably 20 MPa or lower, more preferably 15 MPa or lower, and even more preferably 10 MPa or lower.

[0050] The pressure P can be adjusted by changing the filter opening, filter area, viscosity of the resin composition, filter temperature, extruder heating temperature, resin composition temperature, etc. Alternatively, it can be adjusted by changing the rate at which the resin composition is supplied to the filter. As described above, in order to separate the regenerative resin A with high purity, it is effective to set the difference D within a predetermined range, and this difference D can also be controlled by changing the rate at which the resin composition is supplied to the filter. Specifically, from the viewpoint of improving the productivity of regenerative resin A, the rate at which the resin composition is supplied to the filter is preferably 10 kg / h or more, more preferably 15 kg / h or more, and even more preferably 20 kg / h or more. Furthermore, from the viewpoint of preventing unmelted resin B from being forcibly pushed out and passing through the filter, thus preventing the separation of resin B in addition to regenerative resin A, the rate at which the resin composition is supplied to the filter is preferably 70 kg / h or less, more preferably 50 kg / h or less, and even more preferably 30 kg / h or less.

[0051] The ratio of the mass of the resin composition that passed through the filter to the mass of the resin composition supplied to the filter, i.e., the yield of regenerated resin A, can also be adjusted by changing the pressure P. The yield of regenerated resin A is calculated based on the following formula (2). Details of the calculation method will be explained in the examples described later. Yield (%) = (Resin filtering rate per hour (kg / h)) / (Resin filtering rate per hour (kg / h) + Resin discharge rate per hour (kg / h)) × 100 ... (2) Specifically, the yield is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more, from the viewpoint of improving the productivity of the recycled resin A. Furthermore, the yield is preferably 85% or less, more preferably 80% or less, and even more preferably 75% or less, from the viewpoint of preventing unmelted resin B from being forcibly extruded and passing through the filter, thus preventing the separation of resin B in addition to recycled resin A.

[0052] As the filtration device used in the above-described filtration process, any device commonly used in this type of process can be used without particular limitation. The filtration process can be carried out, for example, by installing a filtration device between the extruder and the die described later, and replacing the filter after each process. Alternatively, by using a filtration device equipped with a backflush type screen changer that performs backwashing, the filter can be replaced continuously without stopping the discharge of the molten resin composition. Alternatively, by using a laser filter equipped with a foreign matter scraping mechanism and a foreign matter discharge mechanism, filter clogging and the rise in the pressure P can be suppressed, and operation for a long time can be performed without replacing the filter. From the viewpoint of improving the productivity of the regenerated resin A, it is preferable to use a laser filter as described above as the filtration device. Examples of laser filters include flat or drum-shaped metal filters and laser filter types using scrapers. Laser filters are preferable because the filter openings are less likely to deform even when high pressure is applied to them, thus preventing resin B and thermosetting resin C from passing through the filter openings.

[0053] In this manner, the resin composition is subjected to filtration, and the recycled resin A is recovered from the resin composition that has passed through the filter, thereby producing the recycled resin A. When a used resin product is used as the resin composition, for example, the heat seal layer constituting the resin product is recovered by this process. The purity of the recovered recycled resin A is preferably 80% by mass or higher.

[0054] The separated recycled resin A can be molded appropriately according to the purpose and application by known methods and reused. For example, the separated recycled resin A can be supplied to a die, and molded articles such as strands using the recycled resin A can be manufactured by the die. Films, sheets, fibers, filaments, injection molded articles, etc., can be manufactured using such molded articles as raw materials. The purity of the separated recycled resin A is preferably 80% or higher, more preferably 84% or higher, and more preferably 87% or higher. Furthermore, from the viewpoint of increasing productivity, the purity of the separated recycled resin A is preferably 99% or lower, more preferably 97% or lower, and even more preferably 95% or lower. When the purity of recycled resin A is 80% or higher, the number of fish eyes that occur in the molded article is reduced, and the thickness unevenness of the molded article is reduced, thus improving moldability. Furthermore, the hue of the separated recycled resin A is also improved. In addition, when the purity of recycled resin A is 99% or lower, the productivity of recycled resin A is improved, which is also advantageous from an economic standpoint. In the production of molded articles using recycled resin A, recycled resin A may be used alone, or, in order to improve moldability, other resins, such as polyolefins, may be used in combination with recycled resin A. The polyolefins described later are preferably used.

[0055] Furthermore, resins such as resin B and thermosetting resin C that did not pass through the filter can be subjected to further separation processes. Alternatively, they can be recovered and reused. If used resin products are used in the resin composition, for example, the base layer, printing layer, and barrier layer constituting the resin product can be recovered through this process.

[0056] The manufacturing method of the present invention may further include a step of adding a predetermined amount of polyolefin having a predetermined melt flow rate (hereinafter also referred to as "MFR") to the resin composition before the extrusion step using an extruder. The polyolefin may be added, for example, to the hopper of the extruder before the resin composition melts, or it may be added after the resin composition has melted and before it has passed through the filter. From the viewpoint of separating the recyclable resin A from the resin composition with high purity, it is preferable to add the polyolefin before the resin composition melts. This makes it easier for the resin composition and the polyolefin to mix, improves the fluidity of the resin composition when it is melt-kneaded by an extruder, and allows the temperature of the resin composition to be easily adjusted. It also makes it easier for the resin composition to pass through the filter. Furthermore, the difference D tends to fall within a predetermined range. As a result, the recyclable resin A can be separated from the resin composition with high purity. The polyolefin preferably has an MFR of 3 g / 10 min or more, more preferably 9 g / 10 min or more, and even more preferably 30 g / 10 min or more. Furthermore, it is preferable that the MFR be 130 g / 10 min or less, more preferably 110 g / 10 min or less, and even more preferably 90 g / 10 min or less. An MFR of 3 g / 10 min or more for the polyolefin improves the fluidity of the resin composition, allowing for the separation of the recycled resin A from the resin composition with high purity. An MFR of 130 g / 10 min or less for the polyolefin ensures sufficient moldability for producing films, sheets, fibers, filaments, and injection-molded articles from molded articles obtained from recycled resin A. Examples of such polyolefins include polyethylene and polypropylene. Among these polyolefins, polyethylene is preferred from the viewpoint of heat sealability. There are no restrictions on the type of polyethylene; HDPE, LDPE, LLDPE, etc., can be used. The aforementioned MFR is measured in accordance with JIS K7210, at 190°C and under a load of 2.16 kg.

[0057] From the viewpoint of separating the recyclable resin A from the resin composition with high purity, it is preferable to add 5% by mass or more of polyolefin to the resin composition, more preferably 7.5% by mass or more, and even more preferably 10% by mass or more. Furthermore, it is preferable to add less than 20% by mass of polyolefin to the resin composition, more preferably 15% by mass or less, and even more preferably 13% by mass or less. Adding 5% by mass or more of polyolefin to the resin composition improves the fluidity of the resin composition, allowing the recyclable resin A to be separated from the resin composition with high purity. Adding less than 20% by mass of polyolefin to the resin composition ensures sufficient moldability to manufacture films, sheets, fibers, filaments, injection molded articles, etc., using molded articles obtained from the recyclable resin A as raw materials.

[0058] Although the present invention has been described above based on its preferred embodiments, the present invention is not limited to the above embodiments. [Examples]

[0059] The present invention will be described in more detail below using examples. However, the scope of the present invention is not limited to these examples. Unless otherwise specified, "%" means "mass%".

[0060] [Example 1] First, a used resin product was prepared using resin composition a. The innermost layer of the resin product was formed by a heat-seal layer. A printed layer was adjacent to the heat-seal layer, and the heat-seal layer and the printed layer were joined by an adhesive. On the printed layer, a base layer was adjacent to the surface opposite to the surface facing the heat-seal layer. In the resin product, the heat-seal layers were bent so that they faced each other, and the ends of the resin product were fused together by heat sealing. Resin composition a was pulverized using a pulverizer (BO4B-480XKFS model, manufactured by Horai Co., Ltd.). The pulverizer was fitted with a screen with holes of the same size as the pulverized resin composition particle size shown in Table 1. Subsequently, resin composition a was fed into a twin-screw extruder and melt-kneaded by the extruder. The heating temperature of the extruder was as shown in Table 1. Details of resin composition a are as follows.

[0061] <Resin composition a> • Recycled resin A (heat seal layer): Polyethylene, melting point 120°C, content 79% • Resin B (base layer): Polyamide 6, melting point 225°C, content 8%, maximum point stress at 200°C 9 MPa, maximum point stress at 190°C 10.5 MPa, maximum point stress at 180°C 12 MPa, maximum point stress at 170°C 13.5 MPa, maximum point stress at 160°C 15 MPa • Resin B (base layer): PET, melting point 260℃, content 8%, maximum point stress at 200℃ 7MPa, maximum point stress at 190℃ 7.5MPa, maximum point stress at 180℃ 8MPa, maximum point stress at 170℃ 9.5MPa, maximum point stress at 160℃ 11MPa • Thermosetting resin C (printing layer and adhesive): Polyurethane, content 5%

[0062] Next, the melt-kneaded resin composition a was subjected to filtration. This separated the regenerative resin A from the resin composition a. This process was carried out using filter A (LF-400-W-G2-R, a laser filter manufactured by FUKURO Corporation) which was pre-installed between the extruder I (a twin-screw extruder with a full-flight screw) and the die. The separated regenerative resin A was recovered. The heating temperature of the extruder, the mesh size of the filter used, the heating temperature of the filter, and the rate at which the resin composition was supplied to the filter are as shown in Table 1.

[0063] [Example 2] In Example 1, extruder II (a twin-screw extruder with a kneading section) was used instead of extruder I. Also, filter B (LF-400-W, a laser filter manufactured by FUKURO Corporation) was used instead of filter A. Recycled resin A was recovered in the same manner as in Example 1.

[0064] [Examples 3 to 9] In Example 1, the heating temperature of the extruder, the type of extruder used, the mesh size of the filter used, the heating temperature of the filter, and the rate at which the resin composition was supplied to the filter were as shown in Table 1. Otherwise, the regenerative resin A was recovered in the same manner as in Example 1.

[0065] [Example 10] In Example 1, a screen with a mesh size of 6 mm was attached to the pulverizer and the material was pulverized. Otherwise, the recycled resin A was recovered in the same manner as in Example 1.

[0066] [Example 11] In Example 10, the heating temperature of the extruder, the heating temperature of the filter, and the rate at which the resin composition was supplied to the filter were as shown in Table 1. Otherwise, the recycled resin A was recovered in the same manner as in Example 10.

[0067] [Example 12] In Example 1, a screen with a mesh size of 3 mm was attached to the pulverizer and the material was pulverized. Otherwise, the recycled resin A was recovered in the same manner as in Example 1.

[0068] [Example 13] In Example 12, the heating temperature of the extruder, the heating temperature of the filter, and the rate at which the resin composition was supplied to the filter were as shown in Table 1. Otherwise, the recycled resin A was recovered in the same manner as in Example 10.

[0069] [Comparative Example 1] The crushed resin composition a was fed into extruder II and melt-kneaded. The molten resin composition a was fed directly into the die without being subjected to filtration, and recycled resin A was recovered. The heating temperature of the extruder and the rate at which the resin composition was supplied to the filter are as shown in Table 1.

[0070] [Comparative Example 2] In Example 1, the heating temperature of the extruder, the type of extruder used, the mesh size of the filter used, and the rate at which the resin composition was supplied to the filter were as shown in Table 1. Otherwise, the recycled resin A was recovered in the same manner as in Example 1.

[0071] [Example 14] In Example 2, resin composition b was used instead of resin composition a. Resin composition b was a used resin product. The composition of this resin product was the same as that of resin composition a, except that the content of recycled resin A, resin B, and thermosetting resin C differed from that of resin composition a. Details of resin composition b are as follows.

[0072] <Resin composition b> • Recycled resin A (heat seal layer): Polyethylene, melting point 120°C, content 72% • Resin B (base layer): Polyamide 6, melting point 225°C, content 11%, maximum point stress at 180°C 12 MPa • Resin B (base layer): PET, melting point 260°C, content 11%, maximum point stress at 180°C 8MPa • Thermosetting resin C (printing layer and adhesive): Polyurethane, content 6%

[0073] [Examples 15 and 16] In Example 2, resin composition b was used instead of resin composition a. Furthermore, before melting resin composition b in the extruder, polyolefin A (high-density polyethylene, manufactured by Prime Polymer Co., Ltd., Hyzex® 2110JH, MFR 9.1g / 10min) was supplied to the extruder hopper. The amount of polyolefin A added to resin composition b is shown in Table 2. Otherwise, the recycled resin A was recovered in the same manner as in Example 2.

[0074] [Example 17] In Example 15, polyolefin B (low-density polyethylene, manufactured by Prime Polymer, Evolu® SP1071C, MFR 10g / 10min) was used instead of polyolefin A. Otherwise, the recycled resin A was recovered in the same manner as in Example 15.

[0075] [Example 18] In Example 15, polyolefin C (low-density polyethylene, manufactured by Prime Polymer, Ultzex® 2020J, MFR 19g / 10min) was used instead of polyolefin A. Otherwise, the regenerative resin A was recovered in the same manner as in Example 15.

[0076] [Example 19] In Example 15, polyolefin D (low-density polyethylene, manufactured by Nippon Polyethylene Co., Ltd., Novatec® UJ790, MFR 50g / 10min) was used instead of polyolefin A. Otherwise, the recycled resin A was recovered in the same manner as in Example 15.

[0077] [Example 20] In Example 15, polyolefin E (low-density polyethylene, manufactured by Prime Polymer, Evolu® SP2320, MFR 4g / 10min) was used instead of polyolefin A. Otherwise, the recycled resin A was recovered in the same manner as in Example 15.

[0078] [Comparative Example 3] Resin composition b was supplied to an extruder and melt-kneaded. The molten resin composition b was supplied directly to a die without being subjected to filtration, and recycled resin A was recovered.

[0079] [Example 23] In Example 1, resin composition c was used instead of resin composition a. Resin composition c was a used resin product. The composition of this resin product was the same as that of resin composition a, except that the content of recycled resin A, resin B, and thermosetting resin C differed from that of resin composition a. Details of resin composition c are as follows.

[0080] <Resin composition c> • Recycled resin A (heat seal layer): Polyethylene, melting point 120°C, content 77% • Resin B (base layer): Polyamide 6, melting point 225°C, content 8%, maximum point stress at 190°C 10.5 MPa, maximum point stress at 180°C 12 MPa, maximum point stress at 170°C 13.5 MPa • Resin B (base layer): PET, melting point 260°C, content 8%, maximum point stress at 190°C 7.5 MPa, maximum point stress at 180°C 8 MPa, maximum point stress at 170°C 9.5 MPa • Thermosetting resin C (printing layer and adhesive): Polyurethane, content 7%

[0081] [Example 24] In Example 23, a screen with a mesh size of 5 mm was attached to the pulverizer and the material was pulverized. Otherwise, the recycled resin A was recovered in the same manner as in Example 1.

[0082] [Example 25] In Example 23, polyolefin A was supplied to the extruder hopper before the resin composition c was melted by the extruder. The amount of polyolefin A added to the resin composition c is shown in Table 3. The recycled resin A was recovered in the same manner as in Example 23.

[0083] [Examples 26 to 35] In Example 24, polyolefin A was supplied to the extruder hopper before the resin composition c was melted by the extruder. The amount of polyolefin A added to the resin composition c is shown in Table 3. The heating temperature of the extruder, the mesh size of the filter used, the heating temperature of the filter, and the rate at which the resin composition was supplied to the filter are shown in Table 3. The recycled resin A was recovered in the same manner as in Example 24.

[0084] 〔evaluation〕 The purity of recycled resin A recovered in the examples and comparative examples was calculated according to the following method. Furthermore, the maximum dispersed particle size of the resins that did not melt in the resin composition (i.e., resin B and thermosetting resin C) was measured according to the method described above. Furthermore, the yield was calculated according to the following method. Furthermore, the maximum point stresses of pressure P and resin B were measured according to the following method. Those results are shown in Tables 1 through 4.

[0085] [Calculation of the purity of recycled resin A] The recycled resin A recovered in the examples and comparative examples was immersed in xylene for 1 hour to elute the recycled resin A. This solution was filtered, and the eluted recycled resin A was removed from the filtrate. The filtrate contained components other than recycled resin A that were insoluble in xylene. The mass of the filtrate was then measured to determine the mass of the components other than recycled resin A. Separately, the mass of the resin composition used was measured in advance. The purity of recycled resin A was calculated based on the following formula (1). Purity of recycled resin A (%) = 1 - (components other than recycled resin A after elution (g) / mass of resin composition before elution (g)) × 100 ... (1) Furthermore, the recycled resin A obtained in Example 14 and polyolefin A were mixed in the proportions shown in Table 4, and the purity of recycled resin A was calculated in the same manner as described above (Examples 21 and 22).

[0086] [Calculation of yield] The yield (%) was calculated based on the following formula (2). The amount of resin passing through the filter per hour in equation (2) below was calculated using the following method. Specifically, first, the resin that had passed through the filter and been extruded from the die was collected for 3 minutes, and its mass was measured. The obtained value was then converted to the mass per hour to calculate the amount of resin passing through the filter per hour. The amount of resin discharged per hour in equation (2) below was calculated using the following method. Specifically, first, resin discharged from the contaminant discharge section of the extruder without passing through the filter was collected for 3 minutes, and the mass of the resin was measured. The obtained value was then converted to the mass per hour to calculate the amount of resin discharged per hour. Yield (%) = (Resin filtering rate per hour (kg / h)) / (Resin filtering rate per hour (kg / h) + Resin discharge rate per hour (kg / h)) × 100 ... (2)

[0087] [Measurement of pressure P] Immediately before the resin composition passed through the filter, the reading from the pressure gauge installed at the tip of the twin-screw extruder was taken. This value was defined as the pressure P.

[0088] [Maximum point stress of resin B] Using an injection molding machine (manufactured by Japan Steel Works, Ltd., J110AD-180H), test specimens (80 mm long x 10 mm wide x 4 mm thick) were injection molded from resin B. When polyamide 6 was used as resin B, the cylinder temperature was set to 240°C for the first 5 units from the nozzle tip side of the injection molding machine, 200°C for the remaining unit, 45°C below the hopper, and the mold temperature to 80°C. Subsequently, a bending test of the test specimens was performed using a universal testing machine with a constant temperature bath (INSTRON, model 5982) in accordance with JIS K7171, and the maximum point stress of resin B was measured. In the bending test, the crosshead speed was set to 2 mm / min, and the temperature of the resin composition when subjected to filtering was measured. L The experiment was conducted under the same temperature conditions.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] As is clear from the results shown in Tables 1 to 3, each example was able to separate the recycled resin A from the resin composition with higher purity than each comparative example. Furthermore, when films were formed using the recycled resin A obtained in each example and each comparative example, the films of each example showed a reduced number of fisheyes, reduced thickness unevenness, and improved moldability compared to the films of each comparative example. In addition, the hue of the separated recycled resin A was improved in each example compared to each comparative example. From the comparison between each example and each comparative example, it can be seen that the moldability of the film is improved by being able to separate the recycled resin A with high purity. Furthermore, when comparing Examples 1, 10, and 12, it can be seen that the larger the particle size of the resin composition, the higher the purity with which the recycled resin A can be separated from the resin composition. The same can be seen when comparing Examples 8, 11, and 13. Furthermore, comparing Examples 15, 16, 21, and 22, it can be seen that adding polyolefin before filtering the melt-kneaded resin composition allows for the separation of regenerative resin A with higher purity than adding polyolefin after filtering.

Claims

1. A resin composition containing recycled resin A and resin B having a higher melting point than recycled resin A is melted by an extruder. A method for producing a recycled resin, comprising the step of subjecting the molten resin composition to treatment with a filter attached to the tip of the extruder to separate the recycled resin A from the resin composition, The recycled resin A is polyethylene, and the resin B is polyester or polyamide. The mesh size of the filter used in the processing with the filter is such that it obstructs the passage of the resin B. The temperature at which the resin composition is subjected to treatment with the filter is set to be above the melting point of the regenerative resin A and below the melting point of the resin B. The heating temperature of the extruder is set to be 20°C or more lower than the melting point of resin B. A method for producing a regenerative resin, further comprising the step of adding a polyolefin having a melt flow rate of 3 g / 10 min or more to the resin composition in an amount of 5% by mass or more and less than 20% by mass, prior to the extrusion step by the extruder.

2. The manufacturing method according to claim 1, wherein the filter is a laser filter having a mechanism for scraping off foreign matter using a scraper.

3. The resin composition further comprises a thermosetting resin C, The manufacturing method according to claim 1, wherein the total amount of the resin B and the thermosetting resin C is 10% by mass or more relative to the resin composition.

4. The manufacturing method according to claim 1, wherein the resin pressure applied to the resin composition subjected to processing by the filter is lower than the maximum point stress of the resin B during processing by the filter.

5. The manufacturing method according to claim 4, wherein the difference between the resin pressure and the maximum point stress is 1 MPa or more and 20 MPa or less.

6. The manufacturing method according to claim 3, wherein the thermosetting resin C is a urethane resin, epoxy resin, phenolic resin, or furan resin.

7. The manufacturing method according to claim 1, wherein the difference between the melting point of the recycled resin A and the melting point of the resin B is 20°C or more and 200°C or less.

8. A step of manufacturing a recyclable resin using the manufacturing method described in any one of claims 1 to 7, The process of molding using the recycled resin, A method for manufacturing a molded article having the following characteristics.

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