Method for separating recycled resin

Abstract

To provide a method for separating a recyclable resin with high purity from a resin composition containing two or more types of resins. [Solution] A method for separating recycled resin A from a resin composition containing recycled resin A, resin B, and component C, comprising a kneading step of kneading the resin composition in a kneader, wherein the kneader has a melting zone in which the temperature of the resin composition is heated to a temperature above the melting point of the resin having the highest melting point in the resin composition, and a subsequent coagulation zone in which the temperature of the resin composition is heated to a temperature below the crystallization temperature of the mixture of resin B and component C, and the ratio of the flow path length of the coagulation zone to the flow path length of the melting zone is 1.25 or more, for separating recycled resin A.

Description

[Technical Field]

[0001] The present invention relates to a method for separating recyclable resins. [Background technology]

[0002] Many packaging materials currently on the market are made from thermoplastic composite materials and / or laminated materials, and are molded into, for example, bottles, refill pouches, etc. For functional reasons, these materials may be composed of completely different types of resin films. Therefore, when packaging materials made from these materials are recovered and the resin is recycled, the material will contain polymers that are incompatible with the main polymer component. For example, polyethylene resin recovered and recycled from pouches contains unmelted polyamide resin and PET, and since polyamide resin and PET result in a heterogeneous blend, the moldability of the film is significantly reduced compared to virgin polyethylene. In particular, resins such as unmelted polyamide resin and PET are incompatible with polyethylene resin and are large in size, so they have a significant impact on the moldability of the recovered and recycled polyethylene resin.

[0003] Therefore, as a method for separating the recyclable resin from other resins, for example, the methods described in Patent Documents 1 and 2 can be cited. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2022-230331 [Patent Document 2] U.S. Patent Application Publication No. 2021 / 114335 [Overview of the project] [Problems that the invention aims to solve]

[0005] Although Patent Documents 1 and 2 describe methods for separating a target thermoplastic resin (recyclable resin) from a mixture of thermoplastic resins, a method for separating the recyclable resin with high purity is desired.

[0006] The present invention relates to a method for separating a recyclable resin with high purity from a resin composition containing two or more types of resins. [Means for solving the problem]

[0007] The present invention relates to the following [1] to [5]. [1] A method for separating recycled resin A from a resin composition containing recycled resin A, resin B, and component C, The process includes a kneading step in which the resin composition is kneaded in a kneader. The kneader has a melting zone that heats the resin composition to a temperature above the melting point of the resin with the highest melting point in the resin composition, and a subsequent coagulation zone that heats the resin composition to a temperature below the crystallization temperature of the mixture of resin B and component C. The ratio of the flow path length of the agglomeration zone to the flow path length of the molten zone ([flow path length of agglomeration zone] / [flow path length of molten zone]) is 1.25 or greater. A method for separating recycled resin A. [2] The method for separating the regenerative resin A according to [1], further comprising a separation step of subjecting the kneaded resin composition obtained in the kneading step to a filter to separate the regenerative resin A. [3] A method for separating the recyclable resin A as described in [2], wherein the temperature of the separation step is above the melting point of the recyclable resin A and below the melting point of the mixture of resin B and component C. [4] The recycled resin A is a thermoplastic resin, Resin B contains polyester resin P, and, Component C is a compound that increases the contact angle of the recycled resin A with respect to the mixture of polyester resin P and component C, compared to the contact angle of the recycled resin A with respect to polyester resin P. A method for separating the recyclable resin A described in any one of the above items [1] to [3]. [5] A method for increasing the purity of recycled resin A separated from a resin composition containing recycled resin A, resin B, and component C, The process includes a kneading step in which the resin composition is kneaded in a kneader, and a separation step in which the kneaded resin composition is subjected to a filter to separate the regenerative resin A. The kneader has a melting zone that heats the resin composition to a temperature above the melting point of the resin with the highest melting point in the resin composition, and a subsequent coagulation zone that heats the resin composition to a temperature below the crystallization temperature of the mixture of resin B and component C. The ratio of the flow path length of the agglomeration zone to the flow path length of the molten zone ([flow path length of agglomeration zone] / [flow path length of molten zone]) is 1.25 or greater. A method for increasing the purity of recycled resin A. [Effects of the Invention]

[0008] The method of the present invention makes it possible to separate a regenerative resin with high purity from a resin composition containing two or more types of resins. [Modes for carrying out the invention]

[0009] The present invention relates to a method for separating recyclable resin A from a resin composition containing recyclable resin A, resin B, and component C, comprising a kneading step of kneading the resin composition in a kneader, wherein the kneader has a melting zone in which the temperature of the resin composition is heated to a temperature equal to or greater than the melting point of the resin having the highest melting point in the resin composition, and a subsequent coagulation zone in which the temperature of the resin composition is heated to a temperature equal to or greater than the crystallization temperature of the mixture of resin B and component C, and the ratio of the flow path length of the coagulation zone to the flow path length of the melting zone ([flow path length of coagulation zone] / [flow path length of melting zone]) is 1.25 or greater.

[0010] The inventors of the present invention focused on the ratio of the flow path length of the coagulation zone to the flow path length of the melting zone in a kneader, and found that by setting the flow path length of the coagulation zone to the flow path length of the melting zone within a specific range, the purity of the separated regenerative resin A can be increased. As a mechanism for exerting such an effect, by sufficiently securing an aggregation zone for aggregating resin B or the like corresponding to the impurities in the present invention, it becomes possible to reduce resin B or the like mixed in the recycling resin A. As a result, it is presumed that the purity of the separated recycling resin A is improved.

[0011] In the present invention, a separation step is further provided in which the kneaded resin composition obtained in the kneading step is subjected to a filter to separate the recycling resin A, and the temperature of the separation step is set to be not less than the melting point of the recycling resin A and less than the melting point of the mixture of resin B and component C. Thus, the recycling resin A that has passed through the melting zone and the aggregation zone is in a molten state, and resin B and component C are in a particulate solid state, and the recycling resin A can be separated from resin B more efficiently.

[0012] In the present invention, the recycling resin A is preferably a thermoplastic resin. The thermoplastic resin is not particularly limited, and examples thereof include polyolefin resins, vinyl chloride resins, styrene resins, vinyl ether resins, polyvinyl alcohol resins, polycarbonate resins, polysulfone resins, and the like.

[0013] Among thermoplastic resins, as the recycling resin A to be separated by the production method of the present invention, a polyolefin resin that is generally often used as the main raw material of packaging materials and has a high demand for recycling is preferable, a polyethylene resin or a polypropylene resin is more preferable, among polyolefin resins, a polyethylene resin having a relatively low melting point is even more preferable, a low-density polyethylene is even more preferable, and a linear low-density polyethylene is even more preferable.

[0014] From the viewpoint of the productivity of the separation step, the melting point of the recycling resin A is preferably 80°C or higher, more preferably 90°C or higher, and even more preferably 100°C or higher. And from the viewpoint of the melting point difference from resin B, it 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.

[0015] The content of the resin A for regeneration in the resin composition is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 75% by mass or more from the viewpoints of the yield of the separation step and the improvement of the purity of the resin A for regeneration after separation, and is preferably 99% by mass or less, more preferably 95% by mass or less, still more preferably 90% by mass or less from the viewpoint of easy separability.

[0016] From the viewpoint of separating the resin for regeneration with high purity, resin B preferably contains the polyester resin P.

[0017] Examples of the polyester resin P include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), and the like.

[0018] Examples of the resin B other than the polyester resin P include, for example, polyamide resins. The polyamide resin in the present invention is a high molecular compound having an amide bond and is a polycondensate of a carboxylic acid component and an amine component. Specific examples of the polyamide resin include, for example, drawn nylon (ONy), undrawn nylon (CNy), nylon 6, nylon 66, nylon 11, nylon 12, MXD6, and the like.

[0019] The content of the polyester resin P in the resin B is preferably 10% by mass or more, more preferably 30% by mass or more, still more preferably 40% by mass or more, still more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more from the viewpoint of coarsening the particles of the polyester resin P contained in the resin B by the addition of the component C, and is preferably 90% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, still more preferably 50% by mass or less from the viewpoint of separating the resin A for regeneration with high purity.

[0020] 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, from the viewpoint of the difference in melting point with that of recycled resin A, and preferably 300°C or lower, more preferably 290°C or lower, and even more preferably 280°C or lower, from the viewpoint of suppressing the deterioration of recycled resin A during the kneading process. If resin B consists of two or more types of resin, it is preferable that each resin has the above melting point.

[0021] The difference in melting points between recycled resin A and resin B is preferably 20°C or higher, more preferably 40°C or higher, even more preferably 60°C or higher, and still more preferably 80°C or higher, from the viewpoint of improving the productivity of the separation process and the purity of recycled resin A after separation, and preferably 200°C or lower, more preferably 180°C or lower, even more preferably 160°C or lower, even more preferably 140°C or lower, even more preferably 120°C or lower, and still more preferably 110°C or lower, from the viewpoint of suppressing the deterioration of recycled resin A in the kneading process. If resin B consists of two or more types of resin, it is preferable that the difference in melting points between the resin with the lowest melting point and recycled resin A is within the above range.

[0022] The content of resin B in the resin composition is preferably 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of easy separation, and preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 25% by mass or less, from the viewpoint of improving the yield of the separation process and the purity of the regenerative resin A after separation.

[0023] Furthermore, from the viewpoint of easy separation, 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, and even more preferably 10 parts by mass or more, per 100 parts by mass of recycled resin A, and from the viewpoint of improving the yield of the separation process and the purity of recycled resin A after separation, it is preferably 100 parts by mass or less, more preferably 60 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less.

[0024] Component C is preferably a compound that increases the contact angle of the regenerating resin A with respect to the mixture of polyester resin P and component C compared to the contact angle of the regenerating resin A with respect to polyester resin P.

[0025] If the contact angle of the regenerating resin A with respect to the polyester resin P is CA1, and the contact angle of the regenerating resin A with respect to the mixture of component C and polyester resin P is CA2, then the larger the difference between CA1 and CA2, the greater the difference in interfacial tension, and the greater the effect of coarsening the particles of polyester resin B. From this viewpoint, the difference between CA1 and CA2 is preferably 1° or more, more preferably 3° or more, even more preferably 5° or more, and preferably 30° or less, more preferably 28° or less, and even more preferably 25° or less. In this specification, the contact angle of the regenerating resin with respect to the polyester resin P or the mixture of component C and polyester resin P is measured by the method described in the examples below. Furthermore, the mixture of component C and polyester resin P is the state in which both are uniformly mixed in a molten state and then solidified, and the mixture includes both reactants in which part of the two have reacted and reactants in which all of the two have reacted.

[0026] Component C is more preferably a compound having a functional group that can react with polyester resin P. Examples of such functional groups include epoxy groups, carbodiimide groups, oxazoline groups, and acid anhydride groups. Among these, epoxy groups or carbodiimide groups are preferred, and epoxy groups are more preferred, from the viewpoint of separating the regenerative resin A with higher purity. From the viewpoint of separating the regenerative resin A with high purity, compounds containing epoxy groups and compounds containing carbodiimide groups are preferred as compounds having these functional groups, glycidyl methacrylate copolymers, mono or dicarbodiimide compounds, and polycarbodiimide compounds are more preferred, glycidyl methacrylate copolymers, monocarbodiimide compounds, and aromatic polycarbodiimide compounds are even more preferred, and glycidyl methacrylate copolymers are even more preferred.

[0027] Examples of compounds containing epoxy groups include copolymers of glycidyl methacrylates such as poly(styrene-methyl methacrylate-glycidyl methacrylate) and poly(styrene-glycidyl methacrylate). Such compounds are commercially available, for example, Joncryl ADR 4468 (manufactured by BASF).

[0028] Compounds containing a carbodiimide group include diisopropylcarbodiimide, dioctyldecylcarbodiimide, dicyclohexylcarbodiimide, diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, di-2,6-diisopropylphenylcarbodiimide, N-toluyl-N'-phenylcarbodiimide, di-p-nitrophenylcarbodiimide, di-p-aminophenylcarbodiimide, di-p-hydroxyphenylcarbodiimide, di-p-chlorophenylcarbodiimide, di-p-methoxyphenylcarbodiimide, di-3,4-dichlorophenylcarbodiimide, di-2,5-dichlorophenylcarbodiimide, di-o-chlorophenylcarbodiimide, p-phenylene-bis-di-o-toluylcarbodiimide, p-phenylene-bis-dicyclohexylcarbodiimide, and p-phenylene-bis Examples include mono- or dicarbodiimide compounds such as -di-p-chlorophenylcarbodiimide and ethylene-bis-diphenylcarbodiimide; and polycarbodiimide compounds such as poly(4,4'-diphenylmethanecarbodiimide), poly(3,5'-dimethyl-4,4'-biphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(3,5'-dimethyl-4,4'-diphenylmethanecarbodiimide), poly(naphthylenecarbodiimide), poly(1,3-diisopropylphenylenecarbodiimide), poly(1-methyl-3,5-diisopropylphenylenecarbodiimide), poly(1,3,5-triethylphenylenecarbodiimide), and poly(triisopropylphenylenecarbodiimide), and poly(4,4'-dicyclohexylmethanecarbodiimide).

[0029] Component C is more preferably a compound with low compatibility with the regenerative resin A, and even more preferably a compound that does not react with the regenerative resin A. For example, if the regenerative resin A is a polyolefin resin, a compound that does not have polyolefin chains is preferred.

[0030] When component C is a polymer compound, the weight-average molecular weight is preferably 100 or more, more preferably 1,000 or more, even more preferably 3,000 or more, and preferably 100,000 or less, more preferably 20,000 or less, and even more preferably 10,000 or less, from the viewpoint of increasing the contact angle of the regenerative resin A with respect to the mixture of component C and polyester resin P and separating the regenerative resin A with high purity.

[0031] The functional group equivalent of component C is preferably 10 g / mol or more, more preferably 100 g / mol or more, even more preferably 200 g / mol or more, and preferably 5,000 g / mol or less, more preferably 1,000 g / mol or less, even more preferably 800 g / mol or less, even more preferably 600 g / mol or less, and even more preferably 400 g / mol or less, from the viewpoint of increasing the contact angle of the regenerating resin A with respect to the mixture of component C and polyester resin P and separating the regenerating resin with high purity.

[0032] The content of component C in the resin composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.5% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 2% by mass or less, from the viewpoint of increasing the contact angle of the regenerative resin A with the mixture of component C and polyester resin P and separating the regenerative resin A with higher purity.

[0033] Furthermore, the content of component C in the resin composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less, from the viewpoint of increasing the contact angle of the regenerative resin A with the mixture of component C and polyester resin P and separating the regenerative resin A with higher purity, per 100 parts by mass of resin B.

[0034] The resin composition may contain resins other than recycled resin A and resin B, such as thermosetting resins, laminating agents, inorganic substances such as aluminum, alumina oxide, and silicon oxide, printing inks, pigments, and other additives. However, the total content of recycled resin A, resin B, and component C in the resin composition is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, even more preferably 98% by mass or more, and even more preferably 100% by mass. Other additives include 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.

[0035] As a preferred embodiment of the resin composition in the present invention, The recycled resin A is a thermoplastic resin, Resin B contains polyester resin P, and, Component C is a compound that increases the contact angle of the recycled resin A with respect to the mixture of polyester resin P and component C, compared to the contact angle of the recycled resin A with respect to polyester resin P. These are some examples. In other words, packaging materials such as bottle containers and refill pouches contain thermoplastic resins such as polyethylene resin and polyester resins P such as PET or polyamide resins, as described above. Therefore, a mixture of such packaging material and component C is a more preferred embodiment of the resin composition in the present invention. Therefore, for example, used packaging materials such as refill pouches, food retort pouches, and detergent bottles can be collected and component C added to them to obtain the resin composition that is the target of the separation method of the present invention. Accordingly, the present invention provides a method for recovering thermoplastic resin from such used packaging materials and a method for recycling used packaging materials.

[0036] The separation method of the present invention includes a kneading step in which the resin composition is kneaded in a kneader. One of the features of the separation method of the present invention is that the kneader has (1) a melting zone and (2) a subsequent coagulation zone, and the ratio of the flow path length of the coagulation zone to the flow path length of the melting zone ([flow path length of coagulation zone] / [flow path length of melting zone]) is 1.25 or more.

[0037] In the melting zone, the temperature of the resin composition is heated to a temperature above the melting point of the resin with the highest melting point in the resin composition. By heating in this way, the recycled resin A, resin B, and component C contained in the resin composition melt, and these components are melt-kneaded together.

[0038] Regarding the relationship between the heating temperature in the melting zone and the melting point of resin B, from the viewpoint of melting resin B once, the temperature is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 15°C or higher than the melting point of resin B. On the other hand, from the viewpoint of reducing environmental impact and suppressing resin degradation, the difference from the melting point of resin B is preferably 100°C or lower, more preferably 70°C or lower, and even more preferably 50°C or lower. If resin B consists of two or more types of resin, it is preferable that the difference from the melting point of the resin with the highest melting point is within the above range.

[0039] Specific examples of the temperature of the resin composition in the melting zone are, from the same viewpoint as above, preferably 180°C or higher, more preferably 200°C or higher, and even more preferably 220°C or higher. On the other hand, from the same viewpoint as above, preferably 350°C or lower, more preferably 330°C or lower, and even more preferably 310°C or lower.

[0040] As a specific example of the flow path length in the melting zone, from the viewpoint of melting resin B once, it is preferably 100 mm or more, more preferably 200 mm or more, and even more preferably 300 mm or more. On the other hand, from the viewpoint of ease of installation of the kneader and suppression of resin deterioration, it is preferably 2,000 mm or less, more preferably 1,700 mm or less, and even more preferably 1,400 mm or less.

[0041] Specific examples of the residence time of the resin composition in the molten zone include, from the viewpoint of melting resin B once, preferably 6 seconds or more, more preferably 12 seconds or more, and even more preferably 18 seconds or more. On the other hand, from the viewpoint of reducing environmental impact and suppressing resin degradation, preferably 300 seconds or less, more preferably 240 seconds or less, and even more preferably 180 seconds or less.

[0042] In the aggregation zone, the temperature of the resin composition is heated to a temperature below the crystallization temperature of the mixture of resin B and component C. By heating in this way, the difference in interfacial tension between the mixture of resin B and component C and the recycled resin A is increased, promoting aggregation of the mixture of resin B and component C. In addition, the shear force applied to the resin composition by the kneader induces crystallization due to the orientation of the mixture of resin B and component C. Furthermore, it is thought that the size of the dispersed particle size of the mixture of resin B and component C increases as the mixture of resin B and component C coalesces. As a result, the separation of the mixture of resin B and component C from the recycled resin A is promoted, and the purity of the separated recycled resin A is improved.

[0043] The temperature of the resin composition in the aggregation zone is preferably the crystallization temperature (Tc) of the mixture of resin B and component C, from the viewpoint of improving the yield of the separation process and the purity of the regenerative resin A after separation. BC) less than, more preferably (Tc BC -5°C or lower, more preferably (Tc BC -10°C or lower, more preferably (Tc BC The temperature is below -30°C. Here, the crystallization temperature of the mixture of resin B and component C can be measured by the method described in the examples below. The mixing ratio of the mixture of resin B and component C can be determined by analyzing the content ratio of resin B and component C in the resin composition to be kneaded. Therefore, a mixture having a mixing ratio corresponding to the analytical value can be prepared and its crystallization temperature measured.

[0044] On the other hand, the lower limit of the temperature of the resin composition in the aggregation zone is preferably higher than the melting point of the regenerative resin A, from the viewpoint of improving the yield of the separation process and the purity of the regenerative resin A after separation, preferably 1°C or more above the melting point, more preferably 5°C or more above the melting point, even more preferably 10°C or more above the melting point, and even more preferably 20°C or more above the melting point.

[0045] Specific examples of heating temperatures in the aggregation zone are, from the same viewpoint as above, preferably 160°C or higher, more preferably 170°C or higher, and even more preferably 175°C or higher. On the other hand, from the same viewpoint as above, preferably 250°C or lower, more preferably 210°C or lower, and even more preferably 200°C or lower.

[0046] The flow path length of the agglomeration zone is preferably 100 mm or more, more preferably 200 mm or more, and even more preferably 300 mm or more, from the viewpoint of agglomerating the mixture of resin B and component C. On the other hand, from the viewpoint of ease of installation of the kneader and improvement of productivity, it is preferably 3,000 mm or less, more preferably 2,700 mm or less, and even more preferably 2,400 mm or less.

[0047] The residence time of the resin composition in the aggregation zone is preferably 10 seconds or more, more preferably 30 seconds or more, even more preferably 50 seconds or more, and even more preferably 60 seconds or more, from the viewpoint of agglomerating the mixture of resin B and component C. On the other hand, from the viewpoint of improving productivity, it is preferably 300 seconds or less, and more preferably 240 seconds or less.

[0048] In the kneader, the ratio of the flow path length of the agglomeration zone to the flow path length of the melting zone ([flow path length of agglomeration zone] / [flow path length of melting zone]) is 1.25 or higher. From the viewpoint of promoting the agglomeration of the mixture of resin B and component C, the above ratio is preferably 1.3 or higher, more preferably 1.4 or higher. On the other hand, from the viewpoint of melting resin B once, the above ratio is preferably 2.2 or lower, more preferably 2.0 or lower, and even more preferably 1.8 or lower.

[0049] The sum of the flow path length in the melting zone and the flow path length in the agglomeration zone is preferably at least 500 mm, more preferably 600 mm or more, and even more preferably 700 mm or more, from the viewpoint of melting resin B once and promoting the agglomeration of the mixture of resin B and component C. On the other hand, from the viewpoint of ease of installation of the kneader, the sum of the above flow path lengths is preferably 4,000 mm or less, more preferably 3,000 mm or less, and even more preferably 2,000 mm or less.

[0050] The sum of the residence time in the molten zone and the residence time in the agglomeration zone of the resin composition is preferably 10 seconds or more, more preferably 20 seconds or more, and even more preferably 30 seconds or more, from the viewpoint of melting resin B once and promoting the agglomeration of the mixture of resin B and component C. On the other hand, from the viewpoint of improving productivity, it is preferably 600 seconds or less, more preferably 360 seconds or less, even more preferably 300 seconds or less, and even more preferably 240 seconds or less.

[0051] As the discharge rate of the resin composition in the kneader, from the viewpoint of improving productivity, it is preferably 1.0 kg / h or more, more preferably 1.5 kg / h or more, still more preferably 5 kg / h or more, and even more preferably 10 kg / h or more. On the other hand, from the viewpoint of reducing the load of the kneader, it is preferably 300 kg / h or less, more preferably 150 kg / h or less, still more preferably 100 kg / h or less.

[0052] The treatment in the melting zone and the treatment in the agglomeration zone can be carried out using a known kneader. For example, it can be carried out as a series of kneading steps using a continuous kneader such as a single-screw or double-screw kneader, an open-roll type kneader, etc. Also, regarding the operating conditions of the kneader such as the temperature, flow path length, discharge rate, residence time, etc. of each zone, they can be appropriately set by the method described in the instruction manual of the known kneader.

[0053] It may further have a separation step of subjecting the kneaded resin composition obtained in the kneading step to a filter to separate the recycled resin A. By such a separation step, the separation of the recycled resin A can be carried out efficiently.

[0054] The temperature of the separation step is preferably the melting point (Mp A ) or higher of the recycled resin A, more preferably (Mp A + 10) °C or higher, still more preferably (Mp A + 20) °C or higher, and even more preferably (Mp A + 30) °C or higher, from the viewpoint of improving the purity of the recycled resin A. On the other hand, from the viewpoints of the yield of the separation step and improving the purity of the recycled resin A after separation, it is preferably lower than the melting point (Mp BC ) of the mixture of resin B and component C, more preferably (Mp BC - 10) °C or lower, still more preferably (Mp BC - 20) °C or lower, and even more preferably (Mp BC - 30) °C or lower. Here, the melting point of the mixture of resin B and component C can be measured by the method described in the examples below. The mixing ratio of resin B and component C can be determined by analyzing the content ratio of resin B and component C in the resin composition to be kneaded; therefore, a mixture having a mixing ratio corresponding to the analytical values ​​can be prepared and its melting point measured.

[0055] Specific examples of temperatures in the separation process are, from the same viewpoint as above, preferably 130°C or higher, more preferably 140°C or higher, and even more preferably 150°C or higher. On the other hand, from the same viewpoint as above, preferably 240°C or lower, more preferably 230°C or lower, and even more preferably 220°C or lower.

[0056] The separation process can be carried out, for example, by placing a filter between the kneader and the die, but it can also be carried out continuously using a device equipped with a filter screen changer. Examples of continuous processing devices equipped with a screen changer include plate type using metal mesh, backflush type with backwashing, and laser filter type using flat plate or drum-shaped metal filters and scrapers.

[0057] The separation process allows for the efficient separation and recovery of the regenerative resin A that has passed through the filter from the resin composition.

[0058] For the filter, a pore size is appropriately selected that inhibits the passage of resin B and component C, depending on the dispersion particle size of these components. Preferred pore sizes include preferably 10 μm or larger, more preferably 50 μm or larger, and even more preferably 200 μm or larger. On the other hand, a pore size of 1,000 μm or smaller is preferable, more preferably 800 μm or smaller, and even more preferably 600 μm or smaller.

[0059] In the separation process, a cooling zone may be provided. It is preferable to provide the cooling zone immediately before the filter. Providing a cooling zone is preferable because it can promote the solidification of resin B. One preferred configuration of a kneader that includes a cooling zone is one that is equipped with [melting zone] - [coagulation zone] - [cooling zone] - [filter] in this order.

[0060] The flow path length of the cooling zone is not particularly limited, but is preferably 50 mm or more, more preferably 100 mm or more, and even more preferably 150 mm or more. On the other hand, it is preferably 4,000 mm or less, more preferably 3,000 mm or less, and even more preferably 2,000 mm or less.

[0061] The residence time in the cooling zone is not particularly limited, but is preferably 3 seconds or more, more preferably 5 seconds or more, and even more preferably 10 seconds or more. On the other hand, it is preferably 360 seconds or less, more preferably 300 seconds or less, and even more preferably 240 seconds or less.

[0062] The recycled resin A separated by the separation method of the present invention can be molded appropriately according to the purpose and application by known methods and reused. For recycled resin A to be used as a raw material for pouches used in daily necessities, the purity of recycled resin A is preferably 85% or higher, more preferably 92% or higher, and even more preferably 95% or higher. When recycled resin A is polyethylene resin and resin B is polyamide resin and / or polyester resin, the purity of recycled resin A can be determined by the method described in the examples below.

[0063] Furthermore, component C removed by the separation method of the present invention can be reused as an additive component to be mixed with the resin composition when the separation method of the present invention is performed continuously.

[0064] Furthermore, the present invention relates to a method for increasing the purity of recycled resin A separated from a resin composition containing recycled resin A, resin B, and component C. in particular, The process includes a kneading step in which the resin composition is kneaded in a kneader, and a separation step in which the kneaded resin composition is subjected to a filter to separate the regenerative resin A. The kneader has a melting zone that heats the resin composition to a temperature above the melting point of the resin with the highest melting point in the resin composition, and a subsequent coagulation zone that heats the resin composition to a temperature below the crystallization temperature of the mixture of resin B and component C. The ratio of the flow path length of the agglomeration zone to the flow path length of the molten zone ([flow path length of agglomeration zone] / [flow path length of molten zone]) is 1.25 or greater. This is a method for increasing the purity of recycled resin A. Here, the preferred ranges for the mixing process, separation process, flow path length, and various other conditions are as described above. [Examples]

[0065] The present invention will be specifically described below with reference to examples. These examples are merely illustrative and do not imply any limitation. Unless otherwise specified, "parts" in the examples refer to parts by mass, and "%" refers to mass percent. The physical properties of the resin, etc., were measured by the following method.

[0066] [Melting point] Using a differential scanning calorimetry analyzer "DSC8500" (PerkinElmer), 10 mg of the sample is weighed into a standard aluminum pan and heated from 25°C to 280°C at a rate of 15°C / min. The peak of the endothermic peak is defined as the melting point. If multiple peaks appear on the DSC curve, the peak of the highest temperature peak is defined as the melting point. The melting point of the mixture of resin B and component C is measured using a sample of the mixture prepared in the mass ratios listed in Table 1.

[0067] [Crystallization temperature] Using a differential scanning calorimetry analyzer "DSC8500" (PerkinElmer), 10 mg of the sample is weighed into a standard aluminum pan and cooled from 280°C to 15°C at a rate of 15°C / min. The peak of the exothermic peak is defined as the crystallization temperature. If multiple peaks appear on the DSC curve, the peak of the lowest temperature exothermic peak is defined as the crystallization temperature. The crystallization temperature of the mixture of resin B and component C is measured using a sample of the mixture prepared in the mass ratios listed in Table 1.

[0068] [Contact angle] (1) Contact angle 1: Contact angle of recycled resin with respect to polyester resin The recycled resin is dropped onto a sheet of polyester resin, and the contact angle of the recycled resin with respect to the polyester resin is measured. The same resins used in the examples and comparative examples are used for the polyester resin and recycled resin, respectively. (a) Preparation of the sheet 20g of dry polyester resin is placed between a 200mm x 200mm x 0.4mm metal spacer and metal plate in a press molding machine (manufactured by Toyo Seiki Seisakusho Co., Ltd.), heated to 270°C in an auto press, and melt-compressed at 0.5 MPa for 2 minutes, then at 20 MPa for 2 minutes. Immediately afterward, it is transferred to a hand press and held at 20 MPa and 150°C for 10 minutes to crystallize. After crystallization, it is cooled at 15°C and 0.5 MPa for 1 minute to form a sheet. (b) Measurement of contact angle The contact angle of the sheet obtained by dropping the recycled resin onto it in a 230°C chamber is captured using a shell-type temperature-variable contact angle meter (DMC-3, manufactured by KYOWA). The contact angle after droplet contact is measured at 1-minute intervals, and the endpoint is defined as the point where the contact angle reaches equilibrium. The contact angle is determined from the captured image using the θ / 2 method. The measurement is performed twice, and the average value is calculated.

[0069] (2) Contact angle 2: Contact angle of the recycled resin with respect to the mixture of polyester resin and component C The polyester resin (PET) and component C listed in Table 1 are mixed in the mass ratio shown in Table 1. The mixture is then melt-kneaded using a twin-screw kneader (manufactured by Japan Steel Works, Ltd., TEX28V (screw diameter 28 mm, L / D=42)) at a discharge rate of 1.5 kg / h, a rotation speed of 70 r / min, and 270°C, and then allowed to cool to obtain a mixture of polyester resin and component C. A sheet of the mixture is prepared in the same manner as in (1) above, except that the obtained mixture is used instead of the polyester resin, and the contact angle of the recycled resin with respect to the mixture of polyester resin and component C is measured.

[0070] [Mixing process] Examples 1-2, Comparative Examples 1-2 The recycled resins A, B, and C shown in Table 1 were mixed to form a resin composition, which was then melt-kneaded using a twin-screw kneader. More specifically, in Example 1 and Comparative Example 1, a twin-screw kneader (Shibaura Machinery Co., Ltd., TEM-41SS (screw diameter 41 mm, L / D=60)) was used to melt-knead the mixture at a discharge rate of 75.0 kg / h and a rotation speed of 230 r / min at the temperatures shown in Table 1. In addition, in Example 2 and Comparative Example 2, a twin-screw kneader (manufactured by Japan Steel Works, Ltd., TEX28V (screw diameter 28 mm, L / D=42)) was used to melt and knead the mixture at a discharge rate of 1.5 kg / h and a rotation speed of 70 r / min at the temperatures shown in Table 1. The temperature and flow path length of the melting zone, the temperature and flow path length of the coagulation zone, and the ratio of flow path lengths are shown in Table 1.

[0071] [Separation process] Example 1, Comparative Example 1 A laser filter (FUKURO Corporation, LF-400-W-G2-R, pore size: 250 μm) was placed between the twin-screw kneader and the die to separate regenerative resin A from the resin composition. Regenerative resin A passed through the laser filter, while resin B and component C formed aggregates and could not pass through the laser filter. The material that passed through the laser filter was cooled and recovered as a solid. The purity of the recycled resin A in the separated solid and the purity increase rate were then measured using the following method. The results are shown in Table 1.

[0072] [Separation process] Example 2, Comparative Example 2 A die was installed in the discharge section of a twin-screw mixer, and an 80-mesh metal mesh was further installed between the discharge section and the die as a filter. For reinforcement, three metal meshes of 60-mesh / 80-mesh / 60-mesh were stacked in sequence. The above mixture was supplied and the twin-screw mixer was operated to perform the filtering process. If the metal mesh became clogged and the resin pressure inside the kneader exceeded 5 MPa within 2 minutes of the start of the separation process, the filtration process was stopped at that point, and the regenerative resin A separated from the start to the stop of the separation was evaluated. On the other hand, if clogging did not occur before 2 minutes had elapsed since the start of the separation process and the resin pressure inside the kneader did not exceed 5 MPa, the recycled resin A separated from the start of separation to 2 minutes after the start of separation was evaluated. The results are shown in Table 1.

[0073] [Purity of separated recycled resin A] After weighing the separated solids, they were immersed in a sufficient amount of hexafluoro-2-propanol at room temperature for 1 hour. After immersion, the liquid and solid components were separated, and the mass of the solid component was weighed. The purity of the separated regenerative resin A was then calculated using the following formula. Since polyamide resins and polyester resins dissolve in hexafluoro-2-propanol, the larger the mass of the solid component after immersion treatment, the higher the purity of the recycled resin A in the solid material. Purity of recycled resin A (%) = [Mass of solid components after immersion treatment (g) / Mass of solid matter before immersion treatment (g)] × 100

[0074] [Purity increase rate] The purity increase rate of recycled resin A was calculated using the following formula. Purity increase rate (%) = [Purity of separated recycled resin A (%) - Concentration of recycled resin A in the resin composition during the kneading process (%)] / [Concentration of recycled resin A in the resin composition during the kneading process (%)] × 100 The "concentration (%) of regenerative resin A in the resin composition during the kneading process" was calculated from the composition of the resin composition.

[0075] [Table 1]

[0076] *: The ratio of the flow path length is [flow path length in the aggregation zone] / [flow path length in the melting zone].

[0077] It was found that the purity of the recycled resin A in Examples 1 and 2 was 91-97%, while the purity in Comparative Examples 1 and 2, where the ratio of the above-mentioned flow path length was less than 1.25, was 87-88%. If the purity of the recycled resin A, in this case polyethylene, is 91-97%, it can be recycled as polyethylene without further purification. Therefore, the separation method of the present invention shown in Examples 1 and 2 can be evaluated as an excellent method. On the other hand, the purity of the polyethylene in Comparative Examples 1 and 2 remained at 87-88%, and at this purity level, additional purification operations are necessary for use as recycled polyethylene. Therefore, the separation methods under the conditions of Comparative Examples 1 and 2 can be evaluated as inferior to the separation method of the present invention.

[0078] Details of the resins used in the examples are as follows. • LLDPE: Linear low-density polyethylene, manufactured by Prime Polymer, Evolu SP0510, melting point: 120℃ Ny6: Nylon 6 (Polyamide 6), manufactured by Ube Industries, Ltd., UBE Nylon1022B, melting point: 225℃, crystallization temperature: 188℃ • PET: Polyethylene terephthalate, manufactured by Unitika Corporation, MA-2103, melting point: 255℃, crystallization temperature: 221℃ Joncryl ADR 4468: Poly(styrene-methyl methacrylate-glycidyl methacrylate), manufactured by BASF, weight-average molecular weight 7,250, functional group equivalent 310 g / mol [Industrial applicability]

[0079] The recyclable resin that can be separated by the method of the present invention is suitably used as packaging material for bottles, refill pouches, and other products used in various fields such as daily necessities like shampoos, detergents, and cosmetics, as well as food products.

Claims

1. A method for separating recycled resin A from a resin composition containing recycled resin A, resin B, and component C, The process includes a kneading step in which the resin composition is kneaded in a kneader. The kneader has a melting zone that heats the resin composition to a temperature above the melting point of the resin with the highest melting point in the resin composition, and a subsequent coagulation zone that heats the resin composition to a temperature below the crystallization temperature of the mixture of resin B and component C. The ratio of the flow path length of the agglomeration zone to the flow path length of the molten zone ([flow path length of agglomeration zone] / [flow path length of molten zone]) is 1.25 or greater. A method for separating recycled resin A.

2. A method for separating the regenerative resin A according to claim 1, further comprising a separation step of subjecting the kneaded resin composition obtained in the kneading step to a filter to separate the regenerative resin A.

3. A method for separating recycled resin A according to claim 2, wherein the temperature of the separation step is above the melting point of recycled resin A and below the melting point of the mixture of resin B and component C.

4. The recycled resin A is a thermoplastic resin. Resin B contains polyester resin P, and, Component C is a compound that increases the contact angle of the recycled resin A with respect to the mixture of polyester resin P and component C, compared to the contact angle of the recycled resin A with respect to polyester resin P. A method for separating the recyclable resin A as described in claim 1.

5. A method for increasing the purity of recycled resin A separated from a resin composition containing recycled resin A, resin B, and component C, The process includes a kneading step in which the resin composition is kneaded in a kneader, and a separation step in which the kneaded resin composition is subjected to a filter to separate the regenerative resin A. The kneader has a melting zone that heats the resin composition to a temperature above the melting point of the resin with the highest melting point in the resin composition, and a subsequent coagulation zone that heats the resin composition to a temperature below the crystallization temperature of the mixture of resin B and component C. The ratio of the flow path length of the agglomeration zone to the flow path length of the molten zone ([flow path length of agglomeration zone] / [flow path length of molten zone]) is 1.25 or greater. A method for increasing the purity of recycled resin A.

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