TWI911230B - Mixing equipment - Google Patents

Abstract

The mixing apparatus provided by this invention can suppress the addition of impurities and obtain recycled resin with a predetermined viscosity from recycled resin. The first mixing apparatus includes a second mixing machine that adds a second resin to a first resin that has been mixed in a first mixing machine and mixes it thereafter. The second mixing machine adjusts the amount of the second resin added according to the viscosity of the first resin mixed in the first mixing machine. The second mixing apparatus includes a second mixing machine that adds a second resin and a third resin to a first resin that has been mixed in a first mixing machine and mixes it thereafter. The second mixing machine adjusts the ratio of the amount of the second resin added to the amount of the third resin added according to the viscosity of the mixture extruded from the second mixing machine.

Description

Mixing equipment

This invention relates to a mixing device.

Various methods have been reviewed for recycling and reusing resin components that cannot be used practically, such as resin components recovered from waste (consumables) or resin components that do not meet the specifications of the products to be sold (off-grade materials) that are inevitably generated during the manufacturing process. (Hereinafter, the above-mentioned recycled resin components are also referred to as "recycled resins", and the resin components obtained by processing recycled resins into a form that can be reused are referred to as "regenerated resins".)

For example, the granulator described in Patent Document 1 includes: an extruder for melting, mixing and extruding waste plastic material, and a molding device for granulating the molten plastic extruded by the extruder into granules.

According to Patent 1, the melt flow rate (MFR) of waste plastics intended for reuse varies depending on their morphology and physical properties, making it difficult to granulate them into particles with a predetermined MFR. To solve this problem, Patent 1 adds peroxide to reduce the molecular weight of high-molecular-weight resins such as polyolefins. Specifically, the granulator described in Patent 1 includes: a first extruder for mixing waste plastics, and a second extruder located downstream of the first extruder for adding peroxide to the molten plastic extruded from the first extruder. Then, the granulator online measures the MFR of the molten plastic extruded from the first extruder. Based on this measured MFR, the amount of peroxide added in the second extruder is adjusted to produce granules with the predetermined MFR. [Previous Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Application Publication No. 2019-65092

(The problem that the invention aims to solve)

According to the granulator described in Patent Document 1, it is expected that granules with a predetermined MFR and viscosity can be obtained from waste plastic. However, in the granulator described in Patent Document 1, peroxides fed into the second extruder will also remain in the granulated granules. These peroxides become impurities in the granulated resin, which may cause changes in the physical properties of the resin.

In view of the above problems, the purpose of this invention is to provide a mixing apparatus that simultaneously suppresses the addition of impurities and obtains a recycled resin with a predetermined viscosity from recycled resin. (Technical means to solve the problem)

To solve the above problems, one aspect of the mixing apparatus of the present invention includes: a second mixing machine that adds a second resin to a first resin that has been mixed in a first mixing machine and mixes it. The second mixing machine adjusts the amount of the second resin added according to the viscosity of the first resin after being mixed in the first mixing machine.

Furthermore, another aspect of the mixing apparatus for solving the aforementioned problem includes a second mixing machine that adds a second resin and a third resin to a first resin that has been mixed in a first mixing machine and mixes them. The second mixing machine is configured to change the ratio of the amount of the second resin to the amount of the third resin by adjusting the viscosity of the mixture extruded from the second mixing machine. (Effects compared to prior art)

According to the present invention, a mixing apparatus is provided to suppress the addition of impurities and obtain a recycled resin with a predetermined viscosity from recycled resin.

The mixing apparatus of the present invention will now be described using a plurality of embodiments.

[First Embodiment] Figure 1 shows a schematic diagram of the mixing apparatus 100 according to the first embodiment of the present invention. The mixing apparatus 100 is used to melt and mix recycled resin, and regenerate it into a recycled resin of a predetermined viscosity.

The aforementioned recycled resins typically include, for example, resin components recovered from waste, or resin components that cannot be used in the final product and are inevitably generated during the manufacturing process. These recycled resins may contain various types of resins in different proportions, or contain metals other than resins, or additives such as pigments and release agents. After being crushed, the recycled resins are subjected to magnetic separation or similar methods to remove metal components such as iron, and then separated according to the individual resin types using gravity separation. However, even with these processes, it is almost impossible to completely separate them into their individual components.

For example, recycled resins from abandoned vehicles, after the removal of metal components, contain a mixture of polyethylene, polypropylene, polyamide, and polyurethane. Gravity separation can separate the mixture of polyethylene and polypropylene, as well as the polyamide. However, using gravity separation to separate polyethylene and polypropylene is impractical considering time and cost. Furthermore, the ratio of polyethylene to polypropylene varies depending on the type of vehicle and its parts.

Therefore, if recycled resin directly from the aforementioned discarded vehicles is melt-blended, the ratio of polyethylene to polypropylene in the resulting recycled resin will vary. Furthermore, depending on this ratio, the viscosity and flowability of the resulting recycled resin will also change. Because these viscosity and flowability are unpredictable, the resulting recycled resin is very difficult to reuse directly.

The mixing device 100 melts and mixes this recycled resin, and further generates a recycled resin with a predetermined viscosity by mixing and melting it with other resins.

The mixing apparatus 100 includes a first mixer 110 and a second mixer 120 connected downstream of the first mixer 110, and is a series extruder. A viscometer 130 is installed at the downstream end of the first mixer 110 and the front end of the second mixer 120 to measure the viscosity of the recycled resin mixed by the first mixer 110 online.

The first mixer 110 is a mixer (extruder) used for melting and mixing recycled resin.

The first mixing machine 110 includes: a long cylindrical drum 112, a screw 114 rotatably driven and disposed in the inner hole of the drum 112, a hopper 116 for feeding recycled resin into the drum 112, and an extrusion section 118 for extruding the mixed recycled resin.

The drum 112 is a container used to mix the recycled resin inside using the screw 114. The drum 112 may also be provided with a heating section for adjusting the internal temperature to melt the recycled resin.

One or more screws 114 are arranged inside the drum 112 and rotated by a motor (not shown) to mix the recycled resin inside the drum 112. A twin-screw extruder consisting of two screws combines screw elements with various mixing characteristics, such as forward thread, kneading, and reverse thread, allowing for adjustment of mixing characteristics and suitable selection based on the type and properties of the resin. Furthermore, an extruder consisting of multiple screw shafts can also be appropriately selected based on mixing performance.

The hopper 116 is an inlet for feeding recycled resin into the drum 112. In this embodiment, the hopper 116 feeds recycled resin containing polyethylene and polypropylene, which is obtained from scrapped vehicles, crushed, and separated by magnetic separation and gravity, into the drum 112.

The extrusion section 118 is connected to one end of the resin flow path 140, and extrudes the recycled resin, which is fed into the drum 112 and melted and mixed by the rotation of the screw 114, into the resin flow path 140 connected to the second mixer 120. The extrusion section 118 can be a known gear pump or the like.

The second mixer 120 is a mixer (extruder) that further melt-mixes the recycled resin that has been mixed by the first mixer 110 by adding other resins (hereinafter referred to as "added resins"), and adjusts the viscosity of the obtained recycled resin to a predetermined range.

Specifically, the second mixer 120 includes: a long cylindrical drum 122, a screw 124 configured to rotate and drive within the inner hole of the drum 122, an inlet 126 for introducing recycled resin melted and mixed by the first mixer 110 into the drum 122, a hopper 127a for adding resin into the drum 122, a hopper 127b for adding additives such as rubber and talc into the drum 122, and an extrusion section 128 for extruding the mixed recycled resin.

The drum 122 is a container used to mix the resin components that have been fed into it using a screw 124. The drum 122 may also have a heating section for adjusting the internal temperature to melt the resin components.

One or more screws 124 are arranged inside the drum 122 and rotated by a motor (not shown) to mix the resin components inside the drum 122. A twin-screw extruder consisting of two screws combines screw elements with various mixing characteristics, such as forward thread, kneading, and reverse thread, allowing for adjustment of mixing characteristics and suitable selection based on the type and properties of the resin. Furthermore, an extruder consisting of multiple screw shafts can also be selected appropriately based on mixing performance.

The inlet 126 is connected to the other end of the resin flow path 140. The recycled resin, which is melt-mixed by the first mixer 110 and extruded from the extrusion section 118, is introduced from the resin flow path 140 into the inside of the drum 122 of the second mixer 120.

Hopper 127a is an inlet for feeding the additive resin into the drum 122. The additive resin is a resin with a known viscosity, which is added to the recycled resin and mixed to adjust the viscosity of the recycled resin to a predetermined range. The additive resin can be the same type of resin as the recycled resin (in this embodiment, polyethylene or polypropylene), or it can be a different type of resin.

The amount of resin added varies depending on the viscosity of the recycled resin measured by the viscometer 130 in hopper 127a. The control of the amount of resin added from hopper 127a will be discussed later.

Hopper 127b is the inlet for feeding additives such as stabilizers, antioxidants, and nucleating agents, as well as fillers such as rubber, talc, and calcium carbonate, into the drum 122. It can also add reinforcing fibers such as glass fiber, carbon fiber, and organic fiber. Even with the addition of a certain amount of these fillers and reinforcing fibers, the resulting viscosity change is within a predictable range, both theoretically and empirically. Therefore, the viscosity of the resulting recycled resin is not unpredictable when adding these additives.

The extrusion section 128 is equipped with molds, etc., and extrudes recycled resin with a predetermined viscosity that has been melt-mixed by the first mixer 110 and the second mixer 120.

Viscometer 130 is an online viscometer used to measure the viscosity of recycled resin that has been melt-mixed in the first mixer. Viscometer 130 can measure the viscosity of a portion of the recycled resin that has been melt-mixed in the first mixer 110 and is moving towards the second mixer; it can be a known viscometer, such as those described in R. Gendron, L. E. Daigneault, J. Cell. Plast., 35, 221 (1999), or M. Lee, C. B. Park, C. Tzoganakis, Polym. Eng. Sci., 39, 99 (1999).

The resin flow path 140 is a flow path connecting the first mixer 110 and the second mixer 120, and has a diameter and structure that allows the recycled resin, which has been melt-mixed in the first mixer 110, to flow through. The resin flow path 140 may also be provided with a valve (not shown) for controlling the melt-mixed recycled resin moving from the first mixer 110 to the second mixer 120. Furthermore, the resin flow path 140 may also be provided with a heating section (not shown) for heating the recycled resin moving inside to maintain its flowability.

In this embodiment, the hopper 127a is used in conjunction with the viscosity of the recycled resin that has been melt-mixed in the first mixer 110, as measured by the viscometer 130 (in this specification, "viscosity" refers to melt viscosity), to change the amount of resin added.

Specifically, in this embodiment, hopper 127a is based on polymer admixture theories, such as the Double-Reptation theory (C. Tsenoglou, Macromolecules, 24, 1762-1767 (1991)), and is calculated as the volume fraction of the recovered resin relative to the total volume of resin recovered after being introduced into the second mixer 120 and the volume of resin added to the second mixer 120 (hereinafter also referred to as "total volume of resin components fed into the second mixer"). Using the viscosity _η _{_i} and the viscosity η_{_j} of the added resin, the required volume fraction of added resin relative to the total volume of resin components fed into the second mixer is calculated to obtain a recycled resin with a viscosity of η_{_Blend}. The _{corresponding} amount of added resin is fed into the drum 122.

According to the Double-Reptation theory, in the two-component system of this embodiment, the viscosity η _Blend of the mixture of the first resin and the second resin can be expressed by the following formula (1).

[Formula 1]・・・Form (1)

In addition, in equation (1), ₁ represents the volume fraction of the first resin (in this embodiment, "recycled resin") relative to the total volume of resin components fed into the second mixer; _η1 represents the viscosity of the first resin; ₂ represents the volume fraction of the second resin (in this embodiment, "added resin") relative to the total volume of the resin components fed into the second mixer; _η2 represents the viscosity of the second resin; _ηBlend represents the viscosity of the obtained mixture.

Here, the viscosity _η1 of the first resin is measured by viscometer 130 and is the viscosity of the recycled resin after being mixed in the first mixer. The viscosity _η2 of the second resin (the viscosity of the added resin) is known. In equation (1), the unknown value is... ₁ and _2. But, ₁ and _2. In this implementation form ₁ + ₂ = 1, therefore ₂ can also be referred to as "1- _1. That is, the unknown values in equation (2) are only 1. _That 's all.

Therefore, by substituting this equivalent value and the desired viscosity η _Blend value of the regenerated resin into equation (1), the volume fraction of the added resin to be added to the second mixer 120 can be calculated. _2. Then, the actual volume _V1 of the first resin can be obtained from the gear pump speed of the extrusion section 218 installed in the first mixer 110. Therefore, the volume _V2 of the second resin (added resin) that should be fed into the second mixer 120 from the hopper 127a can be obtained from _V1 × ( ₂ / ₁ ) Calculation. Since resin viscosity is shear rate dependent, it can be selected according to the shear rate conditions measured by the online viscometer. Another method is to import the model representing the shear rate dependence of resin viscosity (e.g., Cross model, Bird-Carreau model, Carreau-Yasuda model, etc.) into equation (1), and improve the accuracy of viscosity control by amplification.

For example, if the viscosity _η2 of the second resin (added resin) is 5.5 × ^10⁴ Pa·s, then the viscosity _η1 of the first resin (recycled resin mixed in the first mixer) measured by viscometer 130 is one of the values recorded in Table 1. In this case, if a recycled resin with a viscosity η _blend of 3.0 × ^10⁴ Pa·s is desired, then hopper 127a only needs to adjust the volume fraction of the first resin (recycled resin). Volume ratio of resin ₁ and resin 2 (added resin) The amount of resin added to the inside of the drum 122 can be determined by the _following ratio.

[Table 1] First resin (recycled resin) Second resin (added resin) The obtained regenerated resin Volume ratio ₁ (Calculated value) Viscosity (Pa・s) η ₁ (measured value) Volume ratio ₂ (Calculated value) Viscosity (Pa·s) η ₂ (known) Volume ratio Viscosity (Pa·s) η _blend (setting value) 0.272 1000 0.728 55000 1 30000 0.283 2000 0.717 55000 1 30000 0.294 3000 0.706 55000 1 30000 0.306 4000 0.694 55000 1 30000 0.319 5000 0.681 55000 1 30000

Accordingly, according to the first embodiment described above, by simply changing the amount of resin added to the second mixer, the viscosity of the obtained recycled resin can be adjusted to a predetermined range. Therefore, it does not require the addition of impurities, and the physical properties of the obtained recycled resin are less likely to undergo unpredictable changes. Furthermore, as described in Patent 1, the method of adjusting the MFR of recycled resin by adjusting the amount of additives other than the resin may not be applicable depending on the type of recycled resin. For example, while polypropylene uses peroxides to break the molecular chain and reduce the molecular weight, thus increasing the MFR, polyethylene undergoes crosslinking due to peroxides, leading to an increase in molecular weight and a decrease in MFR. In contrast, even in waste plastic mixtures containing polypropylene and polyethylene, the present invention can still homogenize the viscosity of recycled resin.

[Second Embodiment] Figure 2 shows a schematic diagram of the mixing apparatus 200 according to the second embodiment of the present invention. The mixing apparatus 200 is also a mixing apparatus for melt-mixing recycled resin to regenerate a recycled resin of a predetermined viscosity.

The mixing apparatus 200, like the mixing apparatus 100 in the first embodiment, includes a first mixer 210 and a second mixer 220 connected downstream of the first mixer 210, and is a series extruder. A viscometer 230 is installed at the connection between the first mixer 210 and the second mixer 220 to measure the viscosity of the recycled resin mixed using the first mixer 210 online.

The first mixing machine 210 includes: a long cylindrical drum 212, a screw 214 rotatably driven into the inner hole of the drum 212, a hopper 216 for feeding recycled resin into the drum 212, and an extrusion section 218 for extruding the mixed recycled resin. The configuration and function of these components are the same as those of the first mixing machine 110 of the first embodiment, including the drum 112, screw 114, hopper 116, and extrusion section 118, and therefore, repeated descriptions are omitted. Furthermore, the hopper 216 of this embodiment is also made from recycled scrap cars, crushed, and separated by magnetic separation and gravity, and then the recycled resin containing polyethylene and polypropylene is fed into the inside of the drum 212.

The second mixer 220 includes: a long cylindrical drum 222, a screw 224 that is rotated and driven within the inner hole of the drum 222, an inlet 226 that introduces recycled resin melted and mixed by the first mixer 210 into the drum 222, a hopper 227a that feeds added resin into the drum 222, a hopper 227b that feeds additives such as rubber and talc into the drum 222, and an extrusion section 228 that extrudes the mixed recycled resin. The composition and function of the rollers 212, screws 214, hoppers 227b, and extrusion section 218 are the same as those of the rollers 212, screws 214, hoppers 227b, and extrusion section 218 of the second mixer 120 of the first embodiment, and therefore, repeated descriptions are omitted.

Viscometer 230 is an online viscometer used to measure the viscosity of recycled resin that has been melt-mixed in the first mixer. Resin flow path 240 is a flow path connecting the first mixer 210 and the second mixer 220, and has a diameter and structure that allows the recycled resin melt-mixed in the first mixer 210 to flow. The structure and function of viscometer 230 and resin flow path 240 are the same as those of viscometer 130 and resin flow path 140 in the first embodiment, and therefore, repeated descriptions are omitted.

In this embodiment of the mixing apparatus 200, the hopper 227a of the second mixer 220 is used to feed two types of additive resins with different viscosities into the drum 222, unlike the mixing apparatus 100 of the first embodiment. Furthermore, the hopper 227a allows for independent adjustment of the feeding amounts of each of the two additive resins. Additionally, one of the two resins (hereinafter referred to as "the first additive resin") has a viscosity higher than the desired viscosity of the regenerated resin, while the other resin (hereinafter referred to as "the second additive resin") has a viscosity lower than the desired viscosity of the regenerated resin.

In this embodiment, the mixing apparatus 200 and the hopper 227a are used in conjunction with the viscometer 230 to measure the viscosity of the recycled resin after melting and mixing in the first mixer 210, thereby changing the amount of the first added resin and the second added resin.

According to the Double-Reptation theory, in the three-component system as described in this embodiment, the viscosity η _Blend of the mixture of the first resin, the second resin and the third resin can be expressed by the following formula (2).

[Equation 2]・・・Form (2)

In addition, in equation (2), ₁ represents the volume fraction of the first resin (in this embodiment, "recycled resin") relative to the volume of recycled resin introduced into the second mixer 220, the volume of the first added resin added into the second mixer 220, and the total volume of the second added resin added into the second mixer 220 (the total volume of resin components added into the second mixer); _η1 represents the viscosity of the first resin; _η2 represents the volume fraction of the second resin (in this embodiment, "the first added resin") relative to the total volume of the resin components fed into the second mixer; _η2 represents the viscosity of the second resin. ₃ represents the volume fraction of the third resin (in this embodiment, "second added resin") relative to the total volume of the resin components fed into the second mixer; _η3 represents the viscosity of the third resin; _ηBlend represents the viscosity of the obtained mixture.

In this embodiment, the viscosity _η1 of the first resin is measured by viscometer 230 and is the viscosity of the recycled resin after being mixed in the first mixer. Furthermore, the viscosity _η2 of the second resin (first added resin) and the viscosity _η3 of the third resin (second added resin) are known.

Furthermore, in this embodiment, the volume fraction of the first resin... The amount of recycled resin fed into the _first mixer 210 from the hopper 216 and the amount of regenerated resin to be obtained can be determined.

Furthermore, in equation (2), the unknown value is... ₂ and ₃ , but because ₁ . ₂ and _3. In this implementation form ₁ + ₂ + ₃ = 1, therefore ₃ can also be referred to as "1- ₁ - _2. That is, the unknown values in equation (2) are only 2. _That 's all.

Therefore, by substituting this equivalent value and the desired viscosity η _Blend value of the regenerated resin into equation (2), the volume fraction of the added resin to be added to the second mixer 220 can be calculated. ₂ , then from the calculated The value is ₂ , and the volume fraction of the first added resin (third resin) that should be added to the second mixing machine 220 can be calculated. ₃ .

Furthermore, by specifying the percentage of recycled resin content in the desired regenerated resin, this embodiment can adjust the volume of the obtained regenerated resin to a predetermined range.

As described above, this embodiment involves melt-blending recycled resins containing polyethylene and polypropylene. Compared to blends of the same type of resin, blends of different types of resins are more prone to strength reduction due to phase separation between the different resins. Therefore, the proportion of recycled resin in the recycled resin obtained through melt blending is preferably set to a maximum of approximately 30%. Furthermore, if a miscible solvent, such as a copolymer of polyethylene and polypropylene, is added together with the recycled resin into the first mixer, phase separation is less likely to occur. Additionally, by using the same type of resin (the second and third resins) (e.g., both polyethylene or both polypropylene), the reduction in strength due to phase separation between the different resins is less likely to occur.

At this point, if the volume fraction of the recycled resin (first resin) is set to a predetermined value (e.g., 30%), then the total volume fraction of the first additive resin (second resin) and the volume fraction of the second additive resin (third resin) added to the second mixer is also determined (e.g., 70%). Then, if the amount (volume) of recycled resin introduced into the second mixer 220 is set to a certain value, then the total amount (volume) of the first additive resin and the second additive resin input into the second mixer 220 also becomes a certain value [recycled resin volume × (70/30)]. In this embodiment, the total amount (volume) of recycled resin introduced into the second mixer 220, the amount (volume) of first added resin fed into the second mixer 220, and the amount (volume) of second added resin fed into the second mixer 220 can be set within a predetermined range, thereby also setting the amount (volume) of regenerated resin obtained within a predetermined range.

Then, by multiplying the volume fraction of the second resin (first added resin) and the third resin (second added resin) determined by this embodiment to obtain a regenerated resin with a predetermined viscosity by the sum of the volume fractions of the added resins added by the second mixer, the amount (volume) of the first added resin and the amount (volume) of the second added resin that should be added to the second mixer can be calculated.

Accordingly, according to this embodiment, by setting the ratio of recycled resin contained in the obtained recycled resin and the viscosity of the recycled resin, the amount (volume) of the obtained recycled resin can be set to a predetermined range, and the viscosity of the recycled resin can also be set to a predetermined range.

Specifically, the viscosity _η2 of the second resin (first added resin) is 2.0 × ^10⁵ Pa·s, and the viscosity _η3 of the third resin (second added resin) is 6.0 × ^10³ Pa·s. The viscosity _η1 of the recycled resin, measured by viscometer 230 and mixed in the first mixer, is set to the values recorded in Table 1. At this time, if the recycled resin content (equivalent to...) ₁ ) If the volume fraction is 30%, and a recycled resin with a viscosity η _blend of 3.0 × ^10⁴ Pa·s is desired, then hopper 227a only needs to be based on the volume fraction of the second resin (the first added resin). Volume ratio of ₂ and 3rd resins (2nd added resin) The amount of the second resin (first added resin) and the third resin (second added resin) added into the drum 222 can be varied by making the _following ratio.

[Table 2] First resin (recycled resin) Second resin (first added resin) Third resin (second added resin) The obtained regenerated resin Volume ratio ₁ (Settings) Viscosity (Pa・s) η ₁ (measured value) Volume ratio ₂ (Calculated value) Viscosity (Pa·s) η ₂ (known) Volume ratio ₃ (Calculated value) Viscosity (Pa·s) η ₃ (known) Volume ratio Viscosity (Pa·s) η _blend (setting value) 0.300 10000 0.317 200000 0.383 6000 1 30000 0.300 20000 0.282 200000 0.418 6000 1 30000 0.300 30000 0.253 200000 0.447 6000 1 30000 0.300 40000 0.229 200000 0.471 6000 1 30000 0.300 50000 0.207 200000 0.493 6000 1 30000

As shown in Table 2, according to this embodiment, when it is desired to obtain regenerated resin with a recycled resin content within a predetermined range, it is only necessary to adjust the ratio of the volume of the first added resin to the volume of the second added resin fed into the drum 122 from the hopper 227a, and then regenerated resin with a predetermined viscosity can be obtained.

Therefore, according to the second embodiment described above, simply changing the ratio of the volume of the first added resin to the volume of the second added resin in the second mixer is sufficient to adjust the viscosity of the obtained recycled resin to a predetermined range. Thus, no impurities are required, and the physical properties of the obtained recycled resin are less prone to unpredictable changes. Furthermore, by setting the amount of recycled resin fed into the first mixer and the recycled resin content of the obtained recycled resin, simply changing the ratio of the volume of the first added resin to the volume of the second added resin in the second mixer can also set both the viscosity and volume of the obtained recycled resin to a predetermined range.

[Third Embodiment] Figure 3 shows a schematic diagram of the configuration of the mixing apparatus 300 according to the third embodiment of the present invention.

The mixing apparatus differs from the mixing apparatus 100 in that it is equipped with a spectrophotometer 350 for measuring the infrared spectra of the recycled resin after melt mixing by the first mixer 110. Furthermore, since all other components are the same as in the first embodiment, repeated descriptions are omitted.

The spectrometer 350 can be a dispersion type or a Fourier transform (FT-IR) type, with the FT-IR type being preferred. A more suitable spectrometer 350 is the "ParticleTrack with FBRM technology" manufactured by YAMATO SCIENTIFIC Co., Ltd., which allows for high-speed online measurement. The spectrometer 350 can be, for example, an optical fiber 352 installed downstream of the extrusion section 118 (near the viscometer 130 or the resin flow path 140, etc.), as long as it can measure the infrared spectrophotometer of the recycled resin at that location.

The heat stabilizers used in polyethylene and polypropylene resins are generally hindered phenolic antioxidants. For example, Irganox 1010, a hindered phenolic antioxidant, exhibits CO expansion at 1300-1000 ^cm⁻¹ and C=O expansion at 1750-1735 ^cm⁻¹ in the IR spectrum. If these antioxidants, which are ignited during resin recycling, are consumed due to thermal degradation during use, these characteristic peaks will become smaller or disappear in the online IR spectrum. Here, in order to address the height of the IR spectral peak caused by the heat stabilizer as measured by the spectrophotometer 350, the amount of heat stabilizer added from the hopper 127b of the second mixer can be varied to adjust the amount of heat stabilizer in the obtained regenerated resin to a constant value. Furthermore, the amount of heat stabilizer added can be determined by pre-establishing a calibration curve for the IR spectral peak height and the amount added. Alternatively, the amount of heat stabilizer added can be varied empirically.

Furthermore, the additives that can vary the above-mentioned amounts are not limited to heat stabilizers; all types of additives may also be used.

Furthermore, although the above description illustrates an example of a mixing apparatus 100 in the first embodiment being equipped with a beam splitter 350, a beam splitter 350 may also be provided for a mixing apparatus 200 in the second embodiment.

[Other Embodiments] Furthermore, the embodiments described above are merely illustrative examples, and the invention is not limited to these embodiments. Of course, various other embodiments are possible within the scope of the inventive concept.

For example, in the embodiments described above, although a viscometer installed at the downstream end of the first mixer is used to measure the viscosity of the melt-mixed recycled resin, the viscometer can also be installed inside the first mixer or in the resin flow path connecting the first mixer and the second mixer. Furthermore, the viscometer can also be configured to measure the pressure and flow rate of the recycled resin extruded from the extrusion section of the first mixer, and then calculate the viscosity of the recycled resin from these values.

Furthermore, the above embodiments involve adding polyethylene or polypropylene additive resins to recycled resins containing polyethylene and polypropylene. However, the types of resins such as polyethylene monomers, polypropylene monomers, and polyester monomers in off-grade materials or recycled materials that have undergone separation and screening are not limited to these. The recycled resins and additive resins of the present invention may contain combinations of various resins such as polyamide, polystyrene, acrylonitrile-butadiene-styrene copolymer (ABS), polyvinyl chloride (PVC), polycarbonate, polyurethane, and polyester.

Furthermore, in the second embodiment described above, two types of additive resins are added to the recycled resin that has been melted and mixed in the first mixer, but three or more types of additive resins can also be added in the second mixer. Additionally, additives such as stabilizers, antioxidants, and nucleating agents; fillers such as rubber, talc, and calcium carbonate; and reinforcing fiber materials such as glass fiber, carbon fiber, and organic fiber can also be added to the second mixer.

Furthermore, although the above embodiments involve adding recycled resin to the first mixer, they are not limited to recycled resin. Virgin material or natural resin of unknown viscosity may also be added to the first mixer. Additionally, miscible solvents such as copolymers of polyethylene and polypropylene, for example, liquid ethylene-propylene rubber, granular ethylene-propylene rubber, ethylene-butene rubber, propylene-butene rubber, or propylene-butene-ethylene rubber, may also be added to the first mixer.

Furthermore, in the aforementioned embodiments, the extrusion section of the second mixing machine can extrude the recycled resin into any known shape, such as sheets, films, rods, plates, tubes, irregular cross-section molded articles, and strands. Additionally, a cutting blade or similar device can be installed at the rear of the extrusion section to process the extruded recycled resin into granules. Alternatively, a known forming machine can be installed at the rear of the extrusion section to shape the extruded recycled resin into a predetermined shape.

Furthermore, in the third embodiment described above, in addition to changing the amount or proportion of the added resin fed into hopper 127a or from hopper 227a, the amount or proportion of the added resin fed into hopper 127b or from hopper 227b may also be changed. However, it is also possible not to change the amount or proportion of the added resin, but to change only the amount of the additive in accordance with the infrared spectrophotometer measured by the spectrophotometer.

Furthermore, in each of the above embodiments, the mixing apparatus can also control the aforementioned actions using a control unit (not shown). Specifically, the control unit controls the operation of the hopper of the first mixing machine, and then feeds the recycled resin from the hopper into the drum of the first molding machine. Also, the control unit controls the operation of the drum and screw (or motor) of the first mixing machine, heating and melting the recycled resin fed into the drum, and then mixing it. Furthermore, the control unit controls the operation of the extrusion section of the first mixing machine, extruding the molten and mixed recycled resin from the first mixing machine, and then introducing it into the drum of the second mixing machine through the inlet of the second mixing machine. Furthermore, the aforementioned control unit controls the operation of the hopper of the second mixer, and adds one or more types of additive resins and any additives inside the drum of the second mixer. The control unit also controls the operation of the drum and screw (or motor) of the second mixer, heating and melting the recycled resin and additive resins (and additives) fed into the drum, and then mixing them. Finally, the control unit controls the operation of the extrusion section of the second mixer, and then extrudes the melted and mixed resin components from the second mixer. At this time, the aforementioned control unit adjusts the amount of additive resin (or the ratio of the second additive resin to the third additive resin) added from the hopper of the second mixer based on the viscosity of the recycled resin melted and mixed in the first mixer. (Industrial Applicability)

According to the mixing apparatus of the present invention, recycled resin with a predetermined viscosity can be obtained from recycled resin. Since it is not necessary to add substances to reduce the molecular weight of the resin as in Patent 1, the obtained recycled resin is less likely to retain unwanted impurities. The mixing apparatus of the present invention can homogenize the viscosity of recycled resin obtained from consumables or off-grade materials, and the regenerated resin can be easily used for a variety of applications. Therefore, the scope of reuse of such resin can be expected to be expanded, thus helping to improve the efficiency of resin recycling.

100, 200, 300: Mixing Unit 110, 210: First Mixer 112, 212: Drums 114, 214: Screws 116, 216: Hoppers 118, 218: Extrusion Section 120, 220: Second Mixer 122, 222: Drums 124, 224: Screws 126, 226: Inlet Ports 127a, 227a: Hoppers 127b, 227b: Hoppers 128, 228: Extrusion Section 130, 230: Viscometers 140, 240: Resin Flow Paths 350: Spectrophotometer 352: Optical Fiber

Figure 1 is a schematic diagram of the mixing apparatus according to the first embodiment of the present invention; Figure 2 is a schematic diagram of the mixing apparatus according to the second embodiment of the present invention; and Figure 3 is a schematic diagram of the mixing apparatus according to the third embodiment of the present invention.

100: Mixing device

110: No. 1 kneading machine

112: Rolling tube

114: Screw

116: Hopper

118: Extrusion Section

120: The second kneading machine

122: Rolling tube

124: Screw

126:Inlet

127a, 127b: Hoppers

128: Extrusion Section

130: Viscometer

140: Resin flow path

Claims (12)

A mixing apparatus includes: a second mixing machine for adding and mixing a second resin into a first resin that has been mixed in a first mixing machine; and a control unit for determining the volume fraction of the second resin relative to the total volume of the resin components added to the second mixing machine based on the viscosity of the first resin that has been mixed in the first mixing machine; wherein the second mixing machine is used to add an amount of the second resin corresponding to the volume fraction of the second resin calculated by the control unit. The mixing apparatus of claim 1 includes a viscometer capable of measuring the viscosity of the first resin after being mixed in the first mixing machine; the control unit calculates the volume fraction of the second resin relative to the total volume of resin components fed into the second mixing machine based on the viscosity of the first resin measured by the viscometer. As in the mixing apparatus of claim 1 or 2, the control unit calculates the volume fraction of the second resin relative to the total volume of resin components fed into the second mixing machine, based on the viscosity of the second resin and the viscosity of the first resin after being mixed in the first mixing machine. As in the mixing apparatus of claim 1 or 2, wherein the second mixing machine is used to feed the second resin and the third resin; the second mixing machine adjusts the amount of the second resin and the third resin fed in according to the viscosity of the first resin after being mixed by the first mixing machine. As in the mixing apparatus of claim 4, the second resin fed into the second mixing machine has a viscosity higher than that of the resin obtained by mixing in the second mixing machine; and the third resin fed into the apparatus has a viscosity lower than that of the resin obtained by mixing in the second mixing machine. The mixing apparatus of claim 1 or 2 includes a first mixing machine for mixing the first resin, and the second mixing machine is connected to the downstream side of the first mixing machine. A mixing apparatus includes: a second mixing machine for adding and mixing a second resin and a third resin to a first resin that has been mixed in a first mixing machine; wherein the ratio of the amount of the second resin to the amount of the third resin is varied according to the viscosity of the mixture obtained from the second mixing machine. As in the mixing apparatus of claim 7, the second resin fed into the second mixing machine has a viscosity higher than that of the resin obtained by mixing in the second mixing machine; and the third resin fed into the apparatus has a viscosity lower than that of the resin obtained by mixing in the second mixing machine. The mixing apparatus of claim 7 or 8 includes a first mixing machine for mixing the first resin, and the second mixing machine is connected to the downstream side of the first mixing machine. As in the mixing apparatus of claim 1 or 7, wherein the first resin is a mixture of polyethylene and polypropylene. The mixing apparatus of claim 1 or 7 includes: a spectrophotometer for measuring the infrared spectrophotometer of the first resin after being mixed by the first mixing machine; the second mixing machine is used in conjunction with the infrared spectrophotometer of the first resin measured by the spectrophotometer to change the amount of additive added. A mixing apparatus comprises: a second mixing machine for mixing a second resin and an additive into a first resin that has been mixed in a first mixing machine; and a spectrophotometer for measuring the infrared spectrophotometer of the first resin mixed in the first mixing machine; wherein the second mixing machine varies the amount of additive added in response to the infrared spectrophotometer of the first resin measured by the spectrophotometer.