Method of manufacturing resin material, and resin material

Abstract

To provide a method for manufacturing a resin material, which can increase a recycling efficiency of a recovered resin.SOLUTION: A method for manufacturing a reusable resin material from a recovered resin of the present invention includes the steps of: melting and kneading the recovered resin; measuring a viscosity of the recovered resin that is made in a fluid state by the melting and kneading; adjusting the viscosity of the melted-kneaded recovered resin to a target viscosity determined according to a molding method for reusing the resin material; and storing the melted-kneaded recovered resin into a storage container.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a resin material and to a resin material. [Background technology]

[0002] Various methods are being considered for recovering resin materials that are not put to practical use, such as resin materials recovered from waste products (consumer materials) and resin materials that do not meet the standards for sales products (off-grade materials) that are inevitably produced in the manufacturing process, and processing them so that they can be reused (hereinafter, the above-mentioned recovered resin materials will be referred to simply as "recovered resins," and resin materials obtained by processing recovered resins into a form suitable for reuse will be referred to simply as "resin materials" or "recycled resins").

[0003] However, resin materials have the problem that the properties of the recovered resin used as raw material are not constant, and the properties of the resulting resin material are also not stable. For this reason, in Patent Document 1, the rheological properties of used plastics are measured and the rheological data is labeled on the recycled plastic. Patent Document 1 claims that this method makes it possible to produce small batches of material with known quality characteristics.

[0004] On the other hand, in Patent Document 2, the molecular weight of the melt-kneaded recycled polyethylene terephthalate (PET) resin is measured with a sensor, and a chain extender is added based on the measurement results to adjust the molecular weight, thereby stabilizing the properties of the resulting recycled PET resin. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2014-526674 [Patent Document 2] Patent Publication No. 2022-062162 Summary of the Invention [Problem to be solved by the invention]

[0006] The method described in Patent Document 1 allows users to know the properties of the obtained resin material. However, this method does not result in a resin material having properties suitable for the intended use. Furthermore, resin materials that have unintended properties cannot be reused. Therefore, the method described in Patent Document 1 cannot increase the recycling efficiency of recovered resin.

[0007] Moreover, the method described in Patent Document 2 is expected to make the characteristics of the recovered PET resin uniform. However, according to the study by the present inventors, the characteristics of the recovered resin can vary greatly. Therefore, even with the method described in Patent Document 2, the characteristics of the obtained resin material cannot be completely uniform, and the occurrence of large variations cannot be prevented. Furthermore, since the resin material that has become undesired in characteristics cannot be reused, the recycling efficiency of the recovered resin cannot be improved.

[0008] In view of the above problems, an object of the present invention is to provide a method for producing a resin material that can increase the recycling efficiency of recovered resins, and a resin material produced by said method. [Means for solving the problem]

[0009] A method for producing a resin material according to one embodiment of the present invention for solving the above problems relates to the following items [1] to

[10] . [1] A method for producing a reusable resin material from recycled resin, comprising: A step of melting and kneading the recovered resin; measuring the viscosity of the recovered resin that has been made fluid by the melt-kneading; adjusting the viscosity of the melt-kneaded recovered resin to a target viscosity determined according to a molding method for reusing the resin material; and storing the viscosity-adjusted recovered resin in a storage container as the reusable resin material. A method for producing a resin material. [2] In the melt-kneading step, the reusable resin material obtained by adjusting the viscosity is mixed with the recovered resin and melt-kneaded. A method for producing the resin material described in [1]. [3] A step of determining the target viscosity according to a molding method when reusing the resin material from the measured viscosity of the recovered resin. A method for producing the resin material according to [1] or [2]. [4] A step of providing information indicating the target viscosity to the contained resin material. A method for producing a resin material according to any one of [1] to [3]. [5] The information to be provided further includes traceability information, or information indicating additives or stabilizers. A method for producing the resin material according to [4]. [6] The information to be provided includes at least one of the target viscosity, a melt flow rate calculated from the target viscosity, and a molding method set according to the target viscosity. A method for producing the resin material according to [4] or [5]. [7] The information to be provided includes a molding method set according to the target viscosity. A method for producing a resin material according to any one of [4] to [6]. [8] The information provided further includes information indicating the viscosity of the recovered resin. A method for producing a resin material according to any one of [4] to [7]. [9] In the storing step, the reusable resin material is stored in a different storage container according to the target viscosity. A method for producing a resin material according to any one of [1] to [8].

[10] A step of changing a container for containing the reusable resin material according to the target viscosity. A method for producing a resin material according to any one of [1] to [9].

[0010] Further, a resin material according to another embodiment of the present invention for solving the above-mentioned problems relates to the following

[11] .

[11] A resin material produced by the method for producing a resin material according to any one of [1] to

[10] . Effect of the Invention

[0011] According to the present invention, there are provided a method for producing a resin material, which can increase the recycling efficiency of recovered resins, and a resin material produced by said method. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a flow chart of a method for producing reusable resin materials from recycled resins, according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic diagram showing a schematic configuration of a production apparatus (kneading apparatus) for a resin material used in one embodiment of the present invention. [Diagram 3] FIG. 3 is a block diagram showing a main functional configuration of the kneading device shown in FIG. [Figure 4] FIG. 4 is an exemplary graph for explaining a method in which the control unit determines the molding method in the fourth step. [Diagram 5] FIG. 5 is an exemplary graph for explaining a method in which the control unit determines the molding method in the fourth step. [Figure 6] FIG. 6 is a schematic diagram showing how the recovered resin is stored in the sixth step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] For numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages.

[0014] FIG. 1 is a flow chart of a method for producing reusable resin materials from recycled resins, according to one embodiment of the present invention.

[0015] In this embodiment, first, the recovered resin is selected (first step: step S110). Next, the selected recovered resin is melt-kneaded (second step: step S120), and the viscosity of the recovered resin in a fluid state by melt-kneading is measured (third step: step S130). Then, a target viscosity of the resin material to be reused is determined from the measured viscosity of the recovered resin (fourth step: step S140), and the viscosity of the melt-kneaded recovered resin is adjusted to the target viscosity (fifth step: step S150). After that, the reusable resin material obtained by adjusting the viscosity is stored in a storage container (sixth step: step S160), and information is imparted to the stored resin material (seventh step: step S170).

[0016] In this specification, the viscosity of the recovered resin and the added resin is the ratio of shear stress to shear rate. The melt viscosity of the resin has temperature dependency and shear rate dependency. The viscosity of the resin material may be, for example, a value measured by an in-line viscometer of a kneader, or may be a viscosity measurement value of the resin material sampled offline. As the in-line viscometer, a commercially available viscometer (a rotational viscometer or a capillary viscometer) can be used.

[0017] In the following description, first, the kneading device used in the second to fifth steps of this embodiment will be described, and then the operation of the kneading device will be described along with each of the above steps.

[0018] [Kneading equipment] Fig. 2 is a schematic diagram showing the schematic configuration of a resin material production apparatus (kneading apparatus) used in this embodiment, and Fig. 3 is a block diagram showing the main functional configuration of the kneading apparatus.

[0019] The kneading device 100 is a tandem-type extruder having a first kneader 110 and a second kneader 120 connected downstream of the first kneader 110. At a position following the first kneader 110 and preceding the second kneader 120, there are disposed a viscometer 130 for in-line measurement of the viscosity of the recovered resin (hereinafter also simply referred to as "first resin") kneaded by the first kneader 110, and a thermometer 135 for measurement of the temperature of the resin when the viscosity is measured.

[0020] The first kneader 110 is a kneader (extruder) for melting and kneading the recovered resin.

[0021] The first kneader 110 has a long cylindrical cylinder 112, a screw 114 rotatably arranged in the inner bore of the cylinder 112, a hopper 116 for feeding recovered resin into the cylinder 112, and an extrusion section 118 for extruding the kneaded recovered resin.

[0022] The cylinder 112 is a container for kneading the recovered resin put inside with a screw 114. The cylinder 112 may have a heating section for adjusting the internal temperature to melt the recovered resin.

[0023] One or more screws 114 are arranged inside the cylinder 112, and are rotated by a motor (not shown) to knead the recovered resin inside the cylinder 112. A twin-screw extruder consisting of two screws can adjust the kneading characteristics by appropriately combining screw segments with various types of kneading characteristics such as forward flight, kneading, and reverse flight, and can therefore be appropriately selected depending on the type of resin and its physical properties. Furthermore, the combination of multiple screw shafts that make up the extruder can also be appropriately selected depending on the kneading performance.

[0024] The hopper 116 is an inlet for feeding recovered resin into the inside of the cylinder 112. For example, the hopper 116 can feed recovered resin containing polypropylene that has been collected from discarded automobiles and sorted after being crushed into the inside of the cylinder 112.

[0025] The extruding unit 118 communicates with one end of the resin flow path 140, and extrudes the recovered resin that has been fed into the cylinder 112 and melted and kneaded by the rotation of the screw 114, into the resin flow path 140 that communicates with the second kneader 120. The extruding unit 118 can be a known gear pump or the like.

[0026] The second kneader 120 is a kneader (extruder) for adjusting the viscosity of the resulting resin material within a predetermined range by adding another resin (hereinafter simply referred to as "additive resin") to the recovered resin kneaded in the first kneader 110 and further melt-kneading the resin.

[0027] Specifically, the second kneader 120 has a long cylindrical cylinder 122, a screw 124 rotatably arranged in the inner bore of the cylinder 122, an inlet 126 for introducing the recovered resin melted and kneaded by the first kneader 110 into the cylinder 122, a hopper 127a for introducing added resin into the cylinder 122, a hopper 127b for introducing additives such as rubber and talc into the cylinder 122, and an extrusion section 128 for extruding the kneaded recovered resin.

[0028] The cylinder 122 is a container for kneading the resin material introduced therein with a screw 124. The cylinder 122 may have a heating section for adjusting the internal temperature to melt the resin material.

[0029] One or more screws 124 are arranged inside the cylinder 122, and are rotated by a motor (not shown) to knead the resin material inside the cylinder 122. A twin-screw extruder consisting of two screws can adjust the kneading characteristics by appropriately combining screw segments with various types of kneading characteristics such as forward flight, kneading, and reverse flight, and can therefore be appropriately selected depending on the type of resin and its physical properties. Furthermore, the combination of multiple screw shafts that make up the extruder can also be appropriately selected depending on the kneading performance.

[0030] The inlet 126 is connected to the other end of the resin flow path 140, and introduces the recovered resin that has been melted and kneaded in the first kneader 110 and extruded from the extrusion section 118 from the resin flow path 140 into the inside of the cylinder 122 of the second kneader 120.

[0031] The hopper 127a is an inlet for feeding two types of additive resins having different viscosities into the cylinder 122. Of the two types of resins, one resin (hereinafter also simply referred to as "second resin") is a resin having a higher viscosity than the viscosity of the resin material to be obtained (all viscosities among the target viscosities described below), and the other resin (hereinafter also simply referred to as "third resin") is a resin having a lower viscosity than the viscosity of the resin material to be obtained (all viscosities among the target viscosities described below).

[0032] The two types of additive resins are both resins with known viscosities, and are added to and mixed with the recovered resin to adjust the viscosity of the recovered resin to a predetermined range. The additive resin may be the same type of resin as the recovered resin, or may be a different type of resin from the recovered resin. The additive resin may be a virgin material that has not been used after production, or may be a recycled resin with a known viscosity. As the additive resin, a reusable resin material with a known viscosity obtained by carrying out up to the fifth step (described later) of this embodiment may be used. Alternatively, a virgin material may be used for one of the two types of additive resin, and a recycled resin or a reusable resin material obtained by this embodiment may be used for the other.

[0033] The hopper 127a changes the amounts of the two types of added resins added depending on the viscosity of the recovered resin measured by the viscometer 130. The control for changing the amount of added resin added from the hopper 127a will be described later.

[0034] The hopper 127b is an inlet for feeding additives such as stabilizers, antioxidants, and crystal nucleating agents, and fillers such as rubber, talc, and calcium carbonate into the cylinder 122. It is also possible to add reinforcing fiber materials such as glass fiber, carbon fiber, and organic fiber. The addition of these fillers and reinforcing fibers greatly affects the viscosity, but the viscosity of the resin at the time of addition is uniformly controlled, and even if a certain amount of filler or reinforcing fiber is added, the change in viscosity due to the addition is within a range that can be predicted by theoretical formulas or empirical formulas, so the addition of these additives does not make the viscosity of the resulting resin material unpredictable.

[0035] The extrusion section 128 has a die and the like, and extrudes the resin material having a predetermined viscosity that has been melt-kneaded by the first kneader 110 and the second kneader 120 .

[0036] The viscometer 130 is an in-line viscometer that measures the viscosity of the recovered resin melted and kneaded in the first kneader. The viscometer 130 may be any known viscometer that measures the viscosity of a portion of the recovered resin that is melted and kneaded in the first kneader 110 and moves to the second kneader.

[0037] The thermometer 135 is disposed at the same position as the viscometer 130, and measures the temperature of the resin when the viscosity is measured. The thermometer 135 may be any known thermometer.

[0038] The resin flow path 140 is a flow path that communicates between the first kneader 110 and the second kneader 120, and has a diameter and structure that allows the recovered resin melted and kneaded in the first kneader 110 to flow through it. The resin flow path 140 may have a valve (not shown) for controlling the movement of the melted and kneaded recovered resin from the first kneader 110 to the second kneader 120. The resin flow path 140 may also have a heating section (not shown) for heating the recovered resin moving inside to maintain its fluidity.

[0039] The operations of the first kneader 110 and the second kneader 120 are controlled by a control unit 150 (see FIG. 3).

[0040] The control unit 150 may be a known computer, and has a CPU 152 (Central Processing Unit), a RAM 154 (Random Access Memory), a ROM 156 (Read Only Memory), and a storage unit 158. The CPU 152 reads out various control programs and setting data stored in the ROM 156, stores them in the RAM 154, and executes the programs to perform various arithmetic processing. The CPU 152 also controls the overall operation of the kneading device 100 including the first kneader 110, the second kneader 120, and the viscometer 130. The RAM 154 provides a working memory space for the CPU 152 and stores temporary data. The RAM 154 may include a non-volatile memory. The ROM 156 stores various control programs and setting data executed by the CPU 152. Instead of the ROM 156, a rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read Only Memory) or a flash memory may be used. The storage unit 158 ​​stores jobs and data related to the jobs input from the outside via the input / output interface 160. As the storage unit 158, for example, a HDD (Hard Disk Drive) is used, and a DRAM (Dynamic Random Access Memory) or the like may also be used in combination.

[0041] The method for producing a resin material according to this embodiment, which comprises the first to seventh steps, will be described below.

[0042] [Sorting of recovered resin (first step: step S110)] In the first step, the recovered resins are sorted into resin types.

[0043] The collected and recovered resin is usually a mixture of various types of resins such as polyethylene, polypropylene, polystyrene, polyamide, polyvinyl chloride, polyethylene terephthalate (PET), and other resins. Therefore, the recovered resin is first sorted by resin. The sorting method is not particularly limited, and the resins may be sorted manually, by weight or specific gravity, or optically. Among these, optical sorting is preferred because it is simple and can be quickly sorted, and also causes less damage to the recovered resin.

[0044] In the optical sorting method, it is preferable to use near-infrared light. For example, the recovered resins can be sorted based on the transmittance or reflectance of near-infrared light irradiated onto the recovered resins, or based on the spectrum obtained by spectroscopic analysis of the transmitted or reflected light. The sorting using near-infrared light may be performed multiple times to improve the accuracy of the sorting. For example, polyethylene and polypropylene may be sorted from other resins in the first sorting, and polyethylene and polypropylene may be sorted in the second sorting under changed conditions.

[0045] The sorted recovered resins are sent to the next or subsequent steps according to the resin type. At this time, the recovered resins may be washed, dried, or crushed as necessary.

[0046] [Melting and kneading the recovered resin (second step: step S120)] In the second step, the hopper 116 supplies the selected recovered resin to the inside of the cylinder 112 of the first kneader 110. Specifically, the hopper 116 supplies the recovered resin that has been selected and temporarily stored to the inside of the cylinder 112. Note that, by controlling the cylinder 112 (or the heating unit) by the control unit 150, the temperature inside the cylinder 112 in this step is set to a temperature at which the recovered resin melts or flows.

[0047] The first kneader 110 kneads the recovered resin that has been supplied into the cylinder 112 and is molten inside the cylinder 112. Specifically, the first kneader 110 rotates the screw 114 under the control of the control unit 150 to knead the recovered resin and move the kneaded recovered resin toward the outlet of the cylinder 112 (toward the extrusion unit 118). The rotation speed of the screw 114 at this time is adjusted to a rotation speed at which a target discharge amount is obtained, and can be changed as needed depending on the properties and shape of the recovered resin.

[0048] [Measurement of Viscosity (Third Step: Step S130)] In the third step, the viscometer 130 measures the viscosity η of the recovered resin that has been mixed and made fluid by the first mixer 110. r The viscosity measured here is the so-called melt viscosity. The viscosity in this specification means the melt viscosity based on a reference state of a measurement temperature of 230° C. and a shear rate of 1.0 (1 / s) during measurement, but the measured viscosity at other temperatures and shear rates can be easily converted to the same temperature and shear rate by using the relational expression described later. Therefore, the measurement conditions of the viscosity can be freely set without particular restrictions, or linked to the temperature conditions and operation information of the extruder (note that these measurement conditions are for resins containing polyethylene or polypropylene, and when other resins are used, the measurement conditions commonly used for the resins may be used). The viscometer 130 transmits the measured viscosity to the CPU 152. The CPU 152 temporarily stores the viscosity of the resin in the memory unit 158.

[0049] [Determination of target viscosity (fourth step: step S140)] In the fourth step, the control unit 150 calculates the viscosity η r The target viscosity of the resin material to be manufactured is determined from the above.

[0050] The resin material can be subjected to various molding methods such as spinning, injection molding, extrusion molding, and blow molding. The viscosity of the resin material suitable for each molding method is different. For example, in relation to these molding methods, a resin material with a low viscosity is suitable for spinning, and the suitable viscosity increases in the order of injection molding, extrusion molding, and blow molding. In this process, the control unit 150 uses the viscosity η temporarily stored in the memory unit 158 ​​to r Based on this, the viscosity η r A suitable molding method is determined according to the requirements, and a target viscosity of the resin material is determined according to the molding method.

[0051] 4 and 5 are exemplary graphs for explaining a method in which the control unit 150 determines the molding method in this process. As shown in FIG. 4 and FIG. 5, the viscosity η r changes over time depending on factors such as the source of the recovered resin (e.g., a recycler), the date of collection, the type of resin, its shape (flake or pellet form), the presence or absence of coloring or additives, its weight, and its molecular weight.

[0052] In this embodiment, the viscosity η of the recovered resin r A suitable molding method is set in advance in accordance with the viscosity. Specifically, a predetermined viscosity range suitable for each molding method is set for each molding method. Then, for each measured viscosity, a suitable molding method corresponding to the viscosity is determined. In the example shown in FIG. 4, a viscosity η measured and stored at a certain time point a is a The preferred molding method for this is blow molding. Also, the viscosity η measured and stored at a certain time b b The preferred molding method for the above is extrusion molding. Also, the viscosity η measured and stored at a certain time c c The preferred molding method for this is injection molding. Also, the viscosity η measured and stored at a certain time d d The preferred forming method for this is said to be spinning.

[0053] The preferred molding method is not limited to the above four types, and one, two, three, five, six, or more types of molding methods can be arbitrarily determined. The method of determining the preferred molding method is also not limited to the above methods, and may be determined taking into consideration the rate of change in viscosity, the residence time of the recovered resin in the cylinder 112, and the like.

[0054] In this embodiment, a target viscosity of the resin material to be produced is set for each molding method. In the example shown in Fig. 4 and Fig. 5, the target viscosity for blow molding is viscosity η A The target viscosity for extrusion molding is η B The target viscosity for injection molding is η C The target viscosity for spinning is η D It is said that.

[0055] Based on this preset information, the control unit 150 calculates the viscosity η r Based on this, the control unit 150 determines a suitable molding method and a target viscosity corresponding to the molding method for the resin material to be produced from the recovered resin being melted and kneaded at that time. In the example shown in FIG. 4, the control unit 150 determines the viscosity η a For the recovered resin, the preferred molding method is blow molding, and the target viscosity of the resin material produced is viscosity η A The control unit 150 also determines that the viscosity η b For the recovered resin, the preferred molding method is extrusion molding, and the target viscosity of the resin material produced is viscosity η B The control unit 150 also determines that the viscosity η c For the recovered resin, the preferred molding method is injection molding, and the target viscosity of the resin material produced is viscosity η C In addition, the control unit 150 determines that the viscosity η d For the recovered resin, the preferred molding method is spinning, and the target viscosity of the produced resin material is viscosity η D It is decided that.

[0056] [Adjustment of Viscosity (5th Step: Step S150)] In the fifth step, the control unit 150 controls the viscosity η of the resin material to be produced. Final The amount of the additive resin (second resin and third resin) supplied from the hopper 127a of the second kneaded gas 20 to the inside of the cylinder 122 is changed so that the viscosity of the mixture becomes the target viscosity set in the previous step (fourth step).

[0057] In this step, the control unit 150 first calculates the volume fraction φ1 of the recovered resin (first resin), the known viscosities η2 and η3 of the added resins (second and third resins), and the measured viscosity η of the recovered resin based on theories regarding polymer blends, such as the Double-Reptation theory (C. Tsenoglou, Macromolecules, 24, 1762-1767 (1991)). r From these, the volume fractions φ2 and φ3 of the added resins (second resin and third resin) are calculated.

[0058] According to the Double-Reptation theory, in a three-component system, the viscosity η of a mixture of a first resin, a second resin, and a third resin is Blend can be expressed by the following equation (1).

[0059]

number

[0060] In addition, in the formula (1), φ1 represents the volume fraction of the recovered resin with respect to the total amount (total volume of the resin material charged into the second kneader) of the volume of the first resin (recovered resin) introduced into the second kneader 120, the volume of the second resin (added resin) charged into the second kneader 120, and the volume of the third resin (added resin) charged into the second kneader 120, η1 represents the viscosity of the recovered resin, φ2 represents the volume fraction of the second resin with respect to the total volume of the resin material charged into the second kneader, η2 represents the viscosity of the second resin, φ3 represents the volume fraction of the third resin (the third resin in this embodiment) with respect to the total volume of the resin material charged into the second kneader, η3 represents the viscosity of the third resin, and η Blend represents the viscosity of the resulting mixture.

[0061] In this embodiment, the viscosity η1 of the first resin is the viscosity η of the recovered resin kneaded in the first kneader 110 measured by the viscometer 130. r In addition, the viscosity η2 of the second resin and the viscosity η3 of the third resin are known.

[0062] In this embodiment, the volume fraction φ1 of the first resin can be calculated from the amount of recovered resin fed from the hopper 116 to the first kneader 110 and the amount of the resin material to be obtained.

[0063] In formula (1), the unknown values ​​are φ2 and φ3, but in this embodiment, φ1, φ2, and φ3 are φ1+φ2+φ3=1, so φ3 can be read as 1-φ1-φ2. In other words, the only unknown value in formula (1) is φ2.

[0064] Therefore, these values ​​and the target viscosity of the resin material determined in the previous process (= viscosity η Blend ) into equation (1), the volume fraction φ2 of the second resin to be added to the second kneader 120 can be calculated, and the volume fraction φ3 of the third resin to be added to the second kneader 120 can be calculated from the calculated value of φ2.

[0065] Then, under the control of the control unit 150, the hopper 127a pours the second resin and the third resin into the cylinder 122 in amounts according to the calculated volume fraction φ2 of the second resin and the volume fraction φ3 of the third resin.

[0066] In this manner, the control unit 150 calculates the viscosity η a For the recovered resin, the volume fraction φ2 of the second resin and the volume fraction φ3 of the third resin fed from the hopper 127a are changed to increase the viscosity of the resin material produced, and the viscosity is increased to the target viscosity η determined in the previous step. A (η Blend Similarly, the control unit 150 determines the viscosity η b For the recovered resin, the volume fraction φ2 of the second resin and the volume fraction φ3 of the third resin fed from the hopper 127a are changed to lower the viscosity of the resin material produced, and the viscosity is reduced to the target viscosity η determined in the previous step. B (η Blend Similarly, the control unit 150 determines the viscosity η c For the recovered resin, the volume fraction φ2 of the second resin and the volume fraction φ3 of the third resin fed from the hopper 127a are changed to increase the viscosity of the resin material produced, and the viscosity is increased to the target viscosity η determined in the previous step. C (η Blend Similarly, the control unit 150 determines the viscosity η d For the recovered resin, the volume fraction φ2 of the second resin and the volume fraction φ3 of the third resin fed from the hopper 127a are changed to lower the viscosity of the resin material produced, and the viscosity is reduced to the target viscosity η determined in the previous step. D (η Blend )

[0067] In this embodiment, the viscosity is measured (step 3), the target viscosity is determined (step 4), and the viscosity is adjusted (step 5) continuously or periodically, so that a resin material suitable for a molding method according to the viscosity of the recovered resin being added at that time can be obtained.

[0068] As a result, in the example shown in FIG. 4 and FIG. 5, the viscosity is ηA A resin material for blow molding having a viscosity of η B During the period γ, the viscosity of the resin material for extrusion molding is η C A resin material for injection molding having a viscosity of η D Thus, a resin material for spinning is obtained.

[0069] The volume fraction φ1 of the recovered resin (first resin) can be set to a predetermined range, for example, from 0.1 to 0.7 (from 10 volume % to 70 volume %), preferably from 0.2 to 0.6 (from 20 volume % to 60 volume %), and more preferably from 0.3 to 0.5 (from 30 volume % to 50 volume %).

[0070] (Regarding viscosity handling) The temperature dependency and shear rate dependency of the melt viscosity of the added resin can be determined by the following method.

[0071] Using a commercially available rotational rheometer or other device for measuring the melt viscoelasticity of polymers (e.g., Discovery Hybrid Rheometer (DHR10) manufactured by TA Instruments), three to five temperature levels are appropriately selected in the temperature range of the melting point Tm+10°C to Tm+100°C for crystalline resins, and in the temperature range of the glass transition temperature Tg+10°C to Tg+200°C for amorphous resins, and the linear viscoelastic functions (G', G'') are measured in the frequency range ω = 0.1 to 500 (rad / s).

[0072] From this linear viscoelastic function, a master curve is created based on the time-temperature conversion rule with the reference temperature T0 = 230° C. This operation can be easily performed using the software attached to the above rheometer.

[0073] The ratio of the viscosity at the reference temperature T0 to the viscosity at another temperature T is the shift factor a of the time-temperature conversion rule obtained when creating the master curve. T It is expressed as follows:

[0074]

number

[0075] This shift factor is often expressed by the Arrhenius equation for crystalline resins, where E is the activation energy (J / mol) and R is the gas constant.

[0076]

number

[0077] From the complex viscosity |η*(ω)|, which is a linear viscoelastic function, the Cox-Marz law (Cox, WP and Merz, EH: J. Polym. Sci., 28, 619 (1958)) is used to calculate the frequency (ω) = shear rate (γ SR ) to determine the temperature dependence and shear rate dependence of the melt viscosity.

[0078] In addition, the shear rate r SR In the formula, is represented by the following symbol:

[0079]

number

[0080] Rheological model expressing the shear rate dependence of melt viscosity (Carreau-Yasuda model: Yasuda, K., Armstrong, RC and Cohen, RE: Rheol. Acta, 20, 163 (1981))

[0081]

number

[0082] where η0, n, λ, and a are model parameters that represent the zero shear viscosity, the non-Newtonian exponent, the relaxation time, and the parameter related to the transition from the Newtonian region to the non-Newtonian region, respectively.

[0083] Combining equation (3), which expresses the shear rate dependency of viscosity, with equation (4), which expresses the temperature dependency, the viscosity is expressed as follows:

[0084]

number

[0085] By fitting the above measurement results to this equation and determining the parameters, the viscosity at any temperature and shear rate can be immediately calculated.

[0086] If the resin is the same type, η1, η r , η Final The parameters of the temperature dependence of the viscosity of the resin in equation (3) are almost the same as those of the added resin, so the same parameters as those of the added resin may be used.

[0087] The shear rate is η r Alternatively, an in-line viscometer capable of simultaneously measuring viscosities at three or more shear rates may be used to obtain the model parameters of Eq. (4).

[0088] Melt flow rate is often used as an indicator of resin fluidity. Commercially available resins have their melt flow rate listed on their brand list, so it is convenient to use this value as a reference when selecting additive resins (secondary resin, third resin).

[0089] The relationship between the melt viscosity of the added resin and the melt flow rate can be considered as follows. (Takeharu Izaki, Molding and Processing, Vol. 22, October issue, pp. 556-561 (2010))

[0090] Melt flow rate (MFR) is the flow rate of a polymer melt from a capillary under a constant load. It is expressed as σ=ηγ when a constant load F is applied. SR can be calculated from equation (5). The relationship between the shear rate and the flow rate Q is expressed by equation (6).

[0091]

number

[0092] That is, the shear rate γ obtained by viscosity measurement SR - The shear rate at which the stress (σ = 19,360 Pa) corresponds to a load of 2.16 kg is calculated from equation (5) and the flow rate Q [(m 3 / s]), multiplying it by the density ρ and converting the units to [(g / 10min]), the MFR can be calculated from this flow rate.

[0093]

number

[0094] where MFR is (g / 10 min), ρ is polymer density (g / cm 3 ), r: MFR gauge hole radius (cm), γ SR : Shear rate (1 / s).

[0095] The amount of the added resin (second resin and third resin) may be determined in consideration of the melt-kneading time of the recovered resin (the time the resin is retained in the extruder). For example, the frequency of measuring the viscosity in the third step (sampling interval) may be determined according to the melt-kneading time, and the amount of the added resin may be determined according to the viscosity measured at this frequency.

[0096] [Storage in a storage container (sixth step: step S160)] In this step, the reusable resin material obtained by adjusting the viscosity is stored in a storage container. Specifically, the extrusion section 128 of the second kneader 120 extrudes resin materials with different viscosities according to the target viscosity determined in the fourth step and adjusted in the fifth step. In the example shown in Fig. 4 and Fig. 5, the viscosity η A , viscosity η B , viscosity η C , and viscosity η D A resin material having any one of the viscosities is extruded from the extrusion section 128.

[0097] The extruded resin material is cooled and solidified, and cut (pelletized) into a predetermined size as necessary, formed into pellets or flakes, and stored in a storage container. FIG. 6 is a schematic diagram showing how the resin material is stored. In this embodiment, four types of storage containers are prepared according to the target viscosity. The viscosity determined in the fourth step and adjusted in the fifth step is called the viscosity η A The resin material having a viscosity of η is stored in a first storage container 610 for storing a resin material for blow molding. The viscosity determined in the fourth step and adjusted in the fifth step is a viscosity η B The resin material having a viscosity of η is stored in the second storage container 620 for storing the resin material for molding. The viscosity determined in the fourth step and adjusted in the fifth step is the viscosity η C The resin material having a viscosity of η is stored in a third storage container 630 that stores a resin material for injection molding. The viscosity determined in the fourth step and adjusted in the fifth step is a viscosity η D The resin material to be spun is stored in a fourth storage container 640 that stores a resin material to be spun. Selection of these storage containers is performed under the control of the control unit 150 by appropriately changing the flow path, etc.

[0098] The type of container for containing the resin material is not particularly limited, and any known container such as a flexible container bag can be used.

[0099] In this way, by changing the container depending on the target viscosity, a plurality of resin materials having viscosities suitable for each molding method can be obtained.

[0100] [Information assignment (7th step: step S170)] In this step, information indicating the target viscosity determined in the fourth step is provided to the contained resin material.

[0101] The method of adding information is not particularly limited, and a label (label 612, label 622, label 632, label 642 shown in FIG. 6) may be attached to the storage container, or text information, graphic information, or electronic information may be added directly to the storage container with ink or the like. An identification medium such as an ID tag or a QR (registered trademark) code sheet or sticker may be added, and quality information may be stored in the identification medium. It may also be printed as a paper quality guarantee. Information may also be managed using blockchain technology, which makes it impossible to tamper with the information.

[0102] The information to be given may be the target viscosity itself, a molding method corresponding to the target viscosity, or a melt flow rate (MFR) corresponding to the target viscosity.

[0103] At this time, information indicating the type or characteristics of the recovered resin, information indicating the type or characteristics of the additive or filler added from hopper 127b, information indicating the kneading conditions used by cylinders 112 and 122, information indicating the manufacturing conditions of the resin material, information indicating the characteristics of the resin material, and traceability information may be added at the same time.

[0104] Examples of the information indicating the type or characteristics of the recovered resin include information indicating the source of recovery (whether the resin was recovered in compliance with laws such as the Container and Packaging Recycling Law, the Home Appliance Recycling Law, and the Automobile Recycling Law, whether the resin was recovered via a unique route, the name of the local government, the name of the recycling company, etc.), the date of recovery, the type of resin, the shape (whether in a flexi-con or bale form), the presence or absence of coloring or additives, the weight at the time of receipt, the weight after cleaning, the recovered product lot number, the pallet number, the status at the time of delivery, and alerts such as sorting errors. In addition, information indicating the viscosity of the recovered resin before adjustment may be added as information indicating the characteristics of the recovered resin. The information indicating the viscosity may be the viscosity itself, or may be a statistical value of the viscosity (maximum, minimum, standard deviation, etc.), or may be both of these.

[0105] Examples of the information indicating the type or characteristics of the additive or filler include information indicating the manufacturer, brand, MFR, melting point, and type of resin.

[0106] Examples of information indicating the above-mentioned mixing conditions include the source of collection (whether it was collected in accordance with laws such as the Containers and Packaging Recycling Law, the Home Appliance Recycling Law, or the Automobile Recycling Law, or whether it was collected through a unique route, the local government, the name of the recycler, etc.), the date of collection, the type of resin, the shape (flexi-con container or bale), the presence or absence of coloring or additives, the weight at the time of receipt, the weight after cleaning, the molecular weight, the lot number of the collected item, the pallet number, the status at the time of delivery, and information indicating any alerts such as sorting errors.

[0107] Examples of information indicating the manufacturing conditions of the above-mentioned resin material include information indicating the production equipment (extruder diameter, whether it is twin-screw or single-screw, whether or not an in-line viscometer is present), manufacturing time, production volume (discharge volume from extrusion section 128), kneading conditions (kneading temperature, kneader rotation speed, etc.), manufacturing date and time, etc.

[0108] Examples of information indicating the characteristics of the resin material include information indicating the lot number of the resin material, the pallet number used, the sales destination, the shipping destination, pass / fail information of the shipping inspection, the calculated viscosity value for each lot, the calculated MFR value for each lot, the weight for each lot, the size or weight of the pellets or flakes, etc.

[0109] Examples of the traceability information include information indicating the lot number of the resin material, the pallet number used, incoming and outgoing item information, the sales destination, the shipping destination, the processing cost, the shipping date, the weight, the sales amount, and the like.

[0110] For example, by providing traceability information or information indicating additives or stabilizers, it becomes easier for a purchaser of a resin material to decide how to reuse the resin material.

[0111] [summary] According to this embodiment, a resin material having a viscosity suited to a molding method can be obtained, and a resin material that is easy to reuse can be obtained. Therefore, in this embodiment, the recycling efficiency of the recovered resin is improved.

[0112] In addition, according to this embodiment, the closest target viscosity is determined according to the viscosity of the recovered resin, so that the change range of the viscosity of the recovered resin can be made small. Therefore, the viscosity of the resin material to be manufactured is easily adjusted, and the viscosity of the resin material is less likely to vary. In addition, since the target viscosity is set according to the molding method of the resin material, a resin material that can be suitably used for various molding methods can be obtained. In this embodiment, since a reusable resin material can be produced so as to fall within the target viscosity, the recovered resin as a raw material is less likely to be wasted, and the recycling efficiency is high. In this way, in this embodiment, the recycling efficiency of the recovered resin can be further increased.

[0113] Furthermore, since various information is provided for each resin material, the resin materials can be efficiently reused. Since the viscosity of the recycled resin material is known, it can be used for various molding applications, and can also be suitably used as a dilution resin (such as the second resin or third resin in this embodiment) to be added when recycling recovered resin.

[0114] [Other embodiments] It should be noted that the above-described embodiment shows an example of the present invention, and the present invention is not limited to the above-described embodiments. It goes without saying that various other embodiments are possible within the scope of the concept of the present invention.

[0115] In the above embodiment, the resin material is produced by a two-stage kneading device having the first kneader 110 and the second kneader 120, but the resin material may be produced by using only one kneader that introduces the recovered resin and the added resin into the cylinder. When the above embodiment is performed using only one kneader, the viscosity measured by the viscometer 130 in the third step is the viscosity of the mixture in which the second resin and the third resin that are being introduced at that time are mixed with the recovered resin. In such a case, since the volume fractions of the second resin and the third resin are known, the viscosity η1 of the recovered resin in the third step can be found based on a theory (such as the Double-Reptation theory) that shows the relationship between the amount of each polymer and the viscosity of the mixture.

[0116] In addition, in the above-described embodiment, the supply amount of the added resin (volume fractions φ2 and φ3 of the second and third resins) was determined by the double-reptation theory, but other theories that show the relationship between the amount of each polymer and the viscosity of the mixture when blending polymers may be used.

[0117] In the above embodiment, two types of additive resins are added to the recovered resin, but three or more types of additive resins may be added, or one type of additive resin may be added. For example, the above calculation can be extended to the case where three or more types of additive resins are added by changing only the amounts of the two types of additive resins and keeping the amounts of the other additive resins constant. In addition, additives such as stabilizers, antioxidants, and crystal nucleating agents, fillers such as rubber, talc, and calcium carbonate, and reinforcing fiber materials such as glass fibers, carbon fibers, and organic fibers can be added to the cylinder 122.

[0118] Furthermore, the method for adjusting the viscosity in the fifth step is not limited to the above-mentioned method, and may be other known methods such as the addition of an additive such as a molecular weight modifier.

[0119] In the above embodiment, recovered resin is added to the cylinder 122, but not only recovered resin, but also virgin material may be added to the cylinder 122, or natural resin or biomass plastic with unknown viscosity may be added to the cylinder 122. In addition, liquid ethylene-propylene rubber, pelletized ethylene-propylene rubber, ethylene-butene rubber, propylene-butene rubber, or propylene-butene-ethylene rubber may be added to the cylinder 122 as a compatibilizer such as a copolymer of polyethylene and polypropylene.

[0120] The recycled resins and added resins can be a combination of various resins including polyamide, polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS), polyvinyl chloride (PVC), polycarbonate, polyurethane, and polyester. These resins can be off-grade materials or separated and sorted recycled materials. From the perspective of reducing carbon dioxide emissions, biomass plastics made from plant resources, plastics that contain some biomass raw materials using the mass balance method, and biodegradable plastics can also be used.

[0121] In the above-described embodiment, the extrusion unit may extrude the resin material into any known shape, including a sheet, a film, a rod, a plate, a pipe, a modified cross-section molded product, a strand, etc. In addition, a known molding machine according to the target viscosity may be disposed downstream of the extrusion unit to mold the extruded resin material into a predetermined shape. In this case, the molding machine into which the resin material is introduced may be changed according to the target viscosity. [Industrial Applicability]

[0122] According to the present invention, the recycling efficiency of recovered resin can be improved. [Explanation of symbols]

[0123] 100 Kneading device 110 First Mixer 112 cylinders 114 Screw 116 Hopper 118 Extrusion section 120 Second Mixer 122 cylinders 124 Screw 126 Introduction 127a, 127b Hopper 128 Extrusion section 130 Viscometer 135 Thermometer 140 Resin flow path 150 Control section 152 CPU 154 RAM 156 ROM 158 Memory section 160 Input / Output Interface 610 First Containment Container 620 Secondary Containment Container 630 Third Containment Container 640 Fourth Containment Container 612, 622, 632, 642 Labels

Claims

1. A method for producing a reusable resin material from recycled resin, comprising: A step of melting and kneading the recovered resin; measuring the viscosity of the recovered resin that has been made fluid by the melt-kneading; adjusting the viscosity of the melt-kneaded recovered resin to a target viscosity determined according to a molding method for reusing the resin material; and storing the viscosity-adjusted recovered resin in a storage container as the reusable resin material. A method for producing a resin material.

2. In the melt-kneading step, the reusable resin material obtained by adjusting the viscosity is mixed with the recovered resin and melt-kneaded. A method for producing the resin material of claim 1.

3. determining the target viscosity according to a molding method for reusing the resin material from the measured viscosity of the recovered resin; A method for producing the resin material of claim 1.

4. providing information indicating the target viscosity to the contained resin material; A method for producing the resin material of claim 1.

5. The information to be provided further includes traceability information or information indicating an additive or stabilizer; A method for producing the resin material according to claim 4.

6. The information to be provided includes at least one of the target viscosity, a melt flow rate calculated from the target viscosity, and a molding method set according to the target viscosity. A method for producing the resin material according to claim 4.

7. The information to be provided includes a molding method set according to the target viscosity. A method for producing the resin material according to claim 4.

8. The information to be provided further includes information indicating a viscosity of the recovered resin. A method for producing the resin material according to claim 4.

9. In the storing step, the reusable resin material is stored in different storage containers according to the target viscosity. A method for producing the resin material of claim 1.

10. A step of changing a container that contains the reusable resin material according to the target viscosity. A method for producing the resin material of claim 1.

11. A resin material produced by the method for producing a resin material according to any one of claims 1 to 10.

Images