Method for calculating estimated MFR

Abstract

This invention provides an inexpensive and simple method for calculating the estimated MFR in a main channel with a relatively high shear rate. [Solution] A method for calculating the estimated MFR in a flow channel of resin containing molten recycled material.

Description

[Technical Field]

[0001] The present invention relates to a method for calculating estimated MFR, and more specifically, to a method for calculating estimated MFR for resins containing recycled materials. [Background technology]

[0002] In recent years, the use of resins containing recycled materials has been promoted with the aim of reducing environmental impact. However, because resins containing recycled materials are a mixture of multiple resins and additives, their composition is not constant. Therefore, when molding using resins containing recycled materials, depending on the composition of the recycled material, the fluidity may deteriorate, and the pressure of the molten resin in the flow path may become excessive, causing the extruder to stop due to the activation of safety devices, potentially resulting in production losses. In addition, it may affect the wall thickness of the molded product, potentially leading to inferior compressive strength and drop strength, and if the molded product is a container, dimensional errors may occur, potentially worsening the sealing performance.

[0003] On the other hand, MFR (Melt Flow Rate) is an indicator of the fluidity of thermoplastic resins. A higher MFR indicates better fluidity, while a lower MFR indicates poorer fluidity. Generally, MFR is measured using an MFR measuring device according to the method specified in JIS K 7210-1. In this method, thermoplastic resin is placed inside a cylinder, heated to a constant temperature, and a load is applied from above with a piston. The amount of resin extruded from a die located at the bottom of the cylinder is then measured. Furthermore, Annex B of JIS K 7210-1 contains JIS standards for MFR test conditions for each type of resin; for example, JIS K 6922-1 is the relevant standard for polyethylene. According to section 3.5.3 MFR of JIS K 6922-1, the MFR measurement of polyethylene must be performed at a temperature of 190°C and a load of 2.16 kg (when the MFR is 0.1 g / min or higher). However, the shear rate and shear stress generated under these specified measurement conditions are within a smaller range compared to the shear rate and shear stress generated in the resin molding channel.

[0004] Even when molding containers and other products using resins containing recycled materials, managing the MFR (Metal Fluid Ratio) during the molding process can prevent problems such as flow channel blockage and molding defects. However, since the composition of resins containing recycled materials is not constant, it is difficult to measure all possible MFRs by directly measuring the MFR of the resin containing recycled materials using an MFR measuring device according to the method specified in JIS K 7210-1. Therefore, it is necessary to continuously measure the MFR of the molten resin in the flow channel.

[0005] Several methods have been proposed for continuously measuring the MFR of molten resin in a flow path. For example, one method involves branching the flow path, creating a section in the branched path where the shear rate is lower, and performing various measurements at that section to calculate the MFR. However, this method requires branching the flow path, which results in a very expensive system. Another proposed method involves estimating and controlling the viscosity of the molten resin from equipment operating data (Patent Document 1). This method has the advantage of being able to measure in the main flow path where the shear rate is relatively high. However, it requires a gear pump, which results in an expensive system. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-81417 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Therefore, the object of the present invention is to provide an inexpensive and simple method for calculating the estimated MFR in a main channel with a relatively high shear rate. [Means for solving the problem]

[0008] According to the present invention, there is provided a method for calculating an estimated MFR in a resin flow path containing a recycled material in a molten state.

[0009] In the method for calculating the estimated MFR, the pressure loss in the flow path of the molten resin is measured, and the following formula (1) τ [Pa] = ΔP × r / 2L (1) where ΔP is the pressure loss [Pa], r is the radius of the flow path [mm], and L is the length of the flow path [mm], is used to calculate the shear stress τ, and the following formula (2) γ [sec -1 = 4Q / πr 3 (2) where Q is the flow rate [mm 3 / sec], and r is the radius of the flow path [mm], is used to calculate a reference value of the shear rate γ, Using a viscosity measuring device, a lower limit specified value τmin of the shear stress at the reference value of the shear rate γ for a resin of MFRa and an upper limit specified value τmax of the shear stress at the reference value of the shear rate γ for a resin of MFRb smaller than MFRa are measured in advance, It is preferable to calculate the estimated MFR of the molten resin by proportionally dividing the difference between the upper limit specified value τmax and the lower limit specified value τmin using the shear stress τ calculated by the above formula (1).

[0010] In the method for calculating the estimated MFR, it is preferable to calculate the estimated MFR using the following formula (3)

Equation

[0011] In the method for calculating the estimated MFR, it is preferable that the estimated MFR is the average value of MFRa and MFRb.

[0012] In the method for calculating the estimated MFR, the MFRa and the MFRb satisfy the following formula (4) and / or formula (5)

Number

Number

[0013] In the method for calculating the estimated MFR, it is preferable that the molten resin flowing out from the flow path is used for direct blow molding of the container.

[0014] According to the present invention, a program for causing a computer to execute the calculation of the estimated MFR is provided.

[0015] In the program, it is preferable to monitor the estimated MFR in real time and output an abnormal signal when the estimated MFR becomes equal to or higher than MFRa or when the estimated MFR becomes equal to or lower than MFRb.

Advantages of the Invention

[0016] In the method for calculating the estimated MFR of the molten resin of the present invention, since the estimated MFR of the molten resin in the main flow path where the shear rate is relatively large can be calculated, even when using a resin containing recycled materials with large fluctuations in MFR and difficult to measure, the estimated MFR can be calculated at low cost and simply. That is, in the molding process, when the estimated MFR of the molten resin shows an abnormal value, countermeasures can be taken immediately, and problems such as production losses due to the operation of the safety device and molding defects can be prevented. Furthermore, the wall thickness of the molded product can be appropriately controlled, the drop strength and compression strength can be improved, and when the molded product is a container, the sealing property can also be improved.

Brief Description of the Drawings

[0017] [Figure 1]An example diagram showing an enlarged cross-sectional view of the molding apparatus and measuring section. [Figure 2] This diagram illustrates a method for calculating the estimated MFR (Metal Fiber Rate) when high-density polyethylene is used as the resin containing recycled materials. [Figure 3] A flowchart of the program for performing the calculation of the estimated MFR of the present invention. [Figure 4] Another example diagram showing an enlarged cross-sectional view of the molding apparatus and measuring section. [Modes for carrying out the invention]

[0018] This invention relates to a method for calculating the estimated MFR (Metal Fluid Ratio) of a resin containing molten recycled material in a flow path. In this invention, the estimated MFR refers to the MFR calculated from known MFRs, not the MFR measured. That is, the estimated MFR calculation method of this invention, when used in a molding apparatus equipped with an extruder or the like, makes it possible to estimate the MFR of the recycled material-containing resin in the molding apparatus with almost accuracy.

[0019] <Forming equipment> Figure 1 shows an enlarged cross-sectional view of the molding apparatus 1 used in the present invention and a measuring section 4 provided in the molding apparatus 1. The molding apparatus 1 consists of a hopper 2, an extruder 3 provided at the bottom of the hopper, a measuring section 4 provided at the tip of the extruder 3, a head section 5 provided downstream of the measuring section 4, a parison molding section 6 provided at the bottom of the head section 5, and a mold 7. Cross-sections of the head section 5, the parison molding section 6, and the mold 7 are not shown, but for example, the inside of the head section 5 is provided with a flow path that communicates with the pipe section 8e, and the flow path is further bent downwards by 90 degrees inside the head section 5 and communicates with the blowing ports of the parison molding section 6 and the mold 7.

[0020] As shown in the enlarged cross-sectional view of the measuring section 4, a flow path 8 is provided inside the measuring section 4. The flow path 8 penetrates the measuring section 4 in the width direction and is formed from the upstream side as follows: a pipe section 8a with a diameter D1 that communicates with the tip of the extruder 3; a tapered section 8b that communicates with the pipe section 8a and gradually decreases in diameter; an orifice section 8c with a radius r (diameter 2r) that communicates with the tapered section 8b and has a smaller diameter than the pipe section 8a; a tapered section 8d that communicates with the orifice section 8c and gradually increases in diameter; and a pipe section 8e with a diameter D2 that communicates with the tapered section 8d. In the example in Figure 1, the diameter D1 of the pipe section 8a and the diameter D2 of the pipe section 8e are equal. A pressure gauge 9a is provided in the upper part of the orifice section 8c, upstream, and a pressure gauge 9b is provided at a distance L downstream from the pressure gauge 9a. Furthermore, a thermometer 10 is provided at the lower part of the orifice section 8c, at a distance of 1 / 2L downstream from the pressure gauge 9a (equally distanced from pressure gauges 9a and 9b).

[0021] <Container molding procedure> Referring to Figure 1, the procedure for molding a container using resin containing recycled material with the molding apparatus 1 will be explained. First, resin containing crushed or granular recycled material is put into hopper 2. The resin put into hopper 2 is supplied to extruder 3. In extruder 3, the resin is subjected to a strong shear force and becomes molten. The molten resin is extruded from extruder 3 and flows through the flow path 8 inside measuring section 4.

[0022] The molten resin flowing through the channel 8 passes through the pipe section 8a, tapered section 8b, orifice section 8c, tapered section 8d, and pipe section 8e in that order. The molten resin flows out of the channel 8, passes through the head section 5, and then flows into the parison molding section 6, where the parison is formed. The parison is further pushed out by the discharge pressure and gravity, and is sandwiched between the two divided molds 7 at the moment it passes the lower end of the mold, and air is blown into the inside of the parison, thereby performing direct blow molding of the container.

[0023] <Calculation of estimated MFR of molten resin> The procedure for calculating the estimated MFR in the above series of molding processes is described below.

[0024] In this invention, it is necessary to measure the relationship between shear stress and shear rate in advance using a viscosity measuring device for MFRa resin and MFRb resin, which has a viscosity smaller than MFRa. The relationship between shear stress and shear rate is, for example, the relationship shown by the dashed line in Figure 2, and it is necessary to measure such a relationship in advance. Here, MFRa resin and MFRb resin contain recycled materials in addition to the thermoplastic resin, but the MFR is relatively large or relatively small depending on the components of the recycled material and the proportion of recycled material. The measurement of MFRa and MFRb itself is performed using an MFR measuring device in accordance with the method specified in JIS K 7210-1.

[0025] Such MFRa and MFRb resins are empirically selected for each resin type based on the relationship between MFR and the variation in the wall thickness distribution of the molded product. When MFRa resin is used for molding, the fluidity becomes too high, resulting in a large parison drawdown (self-weight drop) and potentially causing localized thinning of the wall thickness distribution of the molded product. This can lead to a deterioration in strength such as compressive strength and drop strength, and if the molded product is a container, dimensional errors may occur, affecting the sealing performance. On the other hand, when MFRb resin is used for molding, the fluidity becomes too low, resulting in a small parison drawdown and potentially causing areas of thicker wall thickness distribution of the molded product. This can lead to defects such as increased product weight, reduced dimensions due to thermal shrinkage, and increased sink marks, and if the molded product is a container, dimensional errors may occur, affecting the sealing performance.

[0026] Next, the calculation procedure using various measurements of the molten resin by the molding apparatus 1 will be explained. The difference between the pressure of the molten resin measured by the pressure gauge 9a located upstream of the measurement section 4 and the pressure of the molten resin measured by the pressure gauge 9b located downstream is determined, and the pressure loss ΔP of the molten resin in the flow path is calculated. Note that the pressure loss ΔP occurs because frictional force is generated between the molten resin and the inner wall of the orifice section 8c as the molten resin flows through the orifice section 8c.

[0027] Using the obtained ΔP, the shear stress τ is calculated by the following equation (1). τ[Pa]=ΔP×r / 2L (1) In the equation, ΔP is the pressure loss [Pa], r is the radius of the flow path [mm], and L is the length of the flow path [mm]. Here, the radius of the flow path r refers to the radius of the flow path in which pressure gauges 9a and 9b are installed. The length of the flow path L refers to the distance between pressure gauges 9a and 9b.

[0028] Furthermore, the reference value for shear rate γ is calculated using the following formula (2). γ[sec -1 ]=4Q / πr 3 (2) In the formula, Q is the flow rate [mm²] 3 [ / sec], where r is the radius of the flow path [mm].

[0029] Furthermore, the flow rate Q is calculated from the set rotational speed of the extruder. The relationship between the rotational speed of the extruder and the amount of resin flowing out of the head outlet per unit time is measured in advance, and this relationship is used to calculate the flow rate Q from the actual rotational speed.

[0030] Then, using the relationship between shear stress and shear rate for the resin of MFRa and the resin of MFRb that have been previously measured by a viscosity measuring device, the lower limit specified value τmin of the shear stress of the resin of MFRa at the reference value of the shear rate γ obtained by Equation (2) is obtained. Similarly, the upper limit specified value τmax of the shear stress is obtained from the relationship between the shear stress and the shear rate of the resin of MFRb at the reference value of the shear rate γ obtained by Equation (2). That is, by obtaining the shear stress τ at the reference value of the shear rate γ respectively, the upper limit specified value τmax and the lower limit specified value τmin can be calculated. Then, using the shear stress τ calculated by Equation (1), the estimated MFR of the molten resin can be calculated by proportionally dividing the difference between the upper limit specified value τmax and the lower limit specified value τmin.

[0031] A more specific procedure for the proportional division will be described. Proportionally dividing the difference between the upper limit specified value τmax and the lower limit specified value τmin can be performed by the following Equation (3), and thereby the estimated MFR can be calculated. [Number] In the formula, τ is the shear stress measured by Equation (1), τmax is the shear stress of the upper limit specified value, τmin is the shear stress of the lower limit specified value, and MFRa and MFRb are values that satisfy MFRb < MFRa.

[0032] Furthermore, by multiplying the calculated estimated MFR by a temperature correction coefficient A, a more accurate estimated MFR can be obtained. The temperature correction coefficient A is a parameter used to correct the temperature error that occurs between the estimated MFR calculated by equation (3) and the MFR obtained when a resin containing recycled material is measured using an MFR measuring device according to the method specified in JIS K 7210-1. That is, the method for measuring MFR specified in JIS K 7210-1 specifies a reference measurement temperature T. However, in the method for calculating the estimated MFR of the present invention, even if the measurement unit 4 is set to the same temperature as the reference measurement temperature T, the actual temperature Ta measured by the thermometer 10 may deviate from the reference measurement temperature T due to the influence of the measurement environment, etc. When this temperature deviation occurs, temperature correction is necessary, so the temperature correction coefficient A must be considered. The reference measurement temperature T is the temperature at which the MFR of the resin of MFRa and the resin of MFRb, which were measured in advance using an MFR measuring device, were measured.

[0033] Furthermore, the temperature correction coefficient A is a value such that A = b^ΔT. ΔT is the temperature difference between the measured temperature Ta measured by the thermometer 10 and the reference measurement temperature T when measuring MFRa and MFRb. b is a temperature correction parameter, and this temperature correction parameter b is determined by measuring the MFR at two different reference measurement temperatures using an MFR measuring device in accordance with the method specified in JIS K 7210-1, using a resin similar to the resin containing recycled material used to determine the estimated MFR in this invention, and determining the effect per 1°C. A detailed method will be explained in the specific example described later.

[0034] When the temperature correction factor A is taken into consideration, the estimated MFR can be expressed as shown in equation (3') below, and by using equation (3'), a more accurate estimated MFR can be calculated.

number

[0035] Furthermore, by adding a correction term Z to the calculated estimated MFR as needed, a more accurate estimated MFR can be obtained. The correction term Z is a parameter used to ultimately correct the error between the estimated MFR calculated using equation (3') and the MFR measured using an MFR measuring device according to the method specified in JIS K 7210-1 for resin containing recycled material. Factors that cause this error include the deterioration of the recycled material and the discrepancy between the measured values ​​of temperature and pressure in the molding device and those measured using an MFR measuring device according to the method specified in JIS K 7210-1.

[0036] For example, regarding the degradation of recycled materials, virgin materials contain antioxidants and other additives to prevent immediate degradation after melting. However, in recycled materials, the effects of antioxidants and other additives have already been deactivated, and degradation may begin immediately after melting starts. As degradation progresses, the MFR (Metal Fluid Rating) is more likely to change, potentially leading to errors due to the degradation of the recycled material. It should be noted that the degradation of recycled materials often depends on the measurement time and measurement temperature. Furthermore, regarding temperature and pressure, errors may occur due to factors such as the fact that temperature is a variable value and therefore cannot be fully corrected by the temperature correction coefficient A, or that the pressure changes slightly compared to the conditions specified in JIS K 7210-1 due to molding conditions, etc. Therefore, by determining the difference between the estimated MFR calculated using equation (3') and the MFR obtained when resin containing recycled material is measured using an MFR measuring device according to the method specified in JIS K 7210-1, the measurement error caused by the above can be corrected.

[0037] Specifically, the correction term Z can be determined by calculating the difference between the MFR obtained by separately measuring the actual MFR using an MFR measuring instrument according to the method specified in JIS K 7210-1, for example, by taking out the resin containing recycled material from the hopper during molding, and the estimated MFR calculated using equation (3'). If these two values ​​match, the correction term Z = 0. In such cases, it can be considered that no degradation of the recycled material occurred and the estimated MFR was measured accurately.

[0038] When considering the temperature correction coefficient A and the correction term Z, the estimated MFR can be expressed as shown in equation (3'') below, and by using equation (3''), an even more accurate estimated MFR can be calculated.

number

[0039] Below, we will specifically explain, using Figure 2, how to calculate the estimated MFR, using high-density polyethylene as an example of a resin containing recycled material.

[0040] Figure 2 shows a method for calculating the estimated MFR when using high-density polyethylene containing recycled material. The two curves shown in Figure 2 represent the relationship between shear rate γ and shear stress τ, which were previously measured using a viscosity measuring device (reference measurement temperature T=190℃) with high-density polyethylene having measured MFR values ​​of MFRa = 0.40 g / 10 min and MFRb = 0.20 g / 10 min, respectively. In other words, it has been empirically observed that when using high-density polyethylene containing recycled material, if the MFR is 0.40 g / 10 min or higher, the fluidity becomes too high, which can cause localized thinning of the wall thickness distribution of the molded container. On the other hand, if the MFR is 0.20 g / 10 min or lower, the fluidity becomes too low, which can cause areas of thick wall thickness distribution of the molded container. Therefore, high-density polyethylene containing recycled material with MFRa = 0.40 g / 10 min and high-density polyethylene containing recycled material with MFRb = 0.20 g / 10 min are prepared, and the relationship between the shear rate γ and shear stress τ of each of the two resins is measured using a viscosity measuring device according to the method specified in JIS K 7210-1. Note that in Figure 2, a logarithmic graph is used to reduce errors, but it is not always necessary to take a logarithmic scale.

[0041] Furthermore, MFRa and MFRb are given by the following equations (4) and / or (5)

number

number

[0042] In the above specific example,

Number

[0043] Next, the reference values of the shear stress τ of the molten resin and the shear rate γ of the molten resin measured by the measurement unit 4 are calculated, and the lower limit specified value τmin of the shear stress and the upper limit specified value τmax of the shear stress are specified. Here, as an example, the estimated MFR at point D in FIG. 2 is obtained. First, the relationship between the rotational speed of the extruder and the amount of resin flowing out per unit time from the head outlet is measured in advance, and from this relationship, the flow rate Q = 1079.24 mm 3 / sec is obtained. Further, using the radius r = 4 mm of the orifice portion 8c, the distance L = 110 mm between the pressure gauge 9a and the pressure gauge 9b, and the pressure loss ΔP = 3.59 MPa of the molten resin obtained by the measuring device, the shear stress τ = 65273 Pa of the molten resin is obtained by formula (1). Further, from the radius r = 4 mm of the orifice portion 8c and the flow rate Q of the above molten resin, the shear rate is γ = 21.47 sec -1 is obtained. This γ = 21.47 sec -1 becomes the reference value of the shear rate γ. Using this reference value for shear rate γ, τmax and τmin are determined from the relationship between shear rate γ and shear stress τ, which was previously measured using a viscosity measuring device. These values ​​can be obtained, for example, by finding an approximation curve from the relationship between shear rate γ and shear stress τ, and substituting the reference value for shear rate γ into the function equation of each approximation curve. When MFRa = 0.40 g / 10 min and MFRb = 0.20 g / 10 min, γ = 21.47 sec. -1 The corresponding shear stresses can be determined as τmin = 55463 Pa for MFRa resin and τmax = 78705 Pa for MFRb resin.

[0044] Next, in order to determine the temperature correction coefficient A, we determine the temperature correction parameter b. First, we prepare high-density polyethylene containing recycled material similar to the resin used to determine the estimated MFR in this invention. We measure the MFR of this resin at two different reference measurement temperatures using an MFR measuring device according to the method specified in JIS K 7210-1 to determine the effect per 1°C. For example, if the MFR measured at a reference measurement temperature T=190°C is 0.30 g / 10 min, and the MFR measured at a reference measurement temperature T=230°C is 0.45 g / 10 min, then the MFR at a reference measurement temperature of 190°C is (0.30 / 0.45) times smaller than the MFR at a reference measurement temperature of 230°C. Since the effect of the change in MFR per 1°C acts as a multiplier, the temperature correction parameter b is calculated as follows.

number

[0045] Substituting the temperature correction coefficient A = 0.991 obtained above into equation (3''),

number

[0046] To determine Z, the resin was extracted from the hopper and the MFR was measured using an MFR measuring instrument. The MFR value obtained from this measurement was 0.30 g / 10 min. Since the estimated MFR calculated by equation (3') is 0.30 g / 10 min, it was found that the correction term Z = 0, and therefore it was determined that it does not need to be considered in this case. As a result, the estimated MFR is calculated to be 0.30 g / 10 min using equation (3') or equation (3'').

[0047] Furthermore, it is preferable that the estimated MFR calculated in this way is the average value of MFRa and MFRb. In the specific example above, the average value of MFRa and MFRb is 0.30 g / 10 min, which matches the calculation result of the estimated MFR, indicating that it is a desirable estimated MFR value.

[0048] The above shows the calculation results for point D. Using the same procedure, calculations were performed for points A-C and E-H in Figure 2 to obtain estimated MFRs. The calculation results, along with those for point D, are shown in Tables 1-3. The estimated MFR calculated using equation (3) before temperature correction was 0.29 to 0.33. Multiplying this value by the temperature correction coefficient to calculate the estimated MFR using equation (3') resulted in values ​​of 0.30 to 0.31 in all cases. Since the corrected estimated MFR matched or was close to the preferred estimated MFR value, it was determined that the measurement was performed accurately, and the correction term Z was not considered. Also, when determining the temperature correction coefficient A, the temperature correction parameter b did not change at each point, so it was calculated using b = 0.991.

[0049] [Table 1]

[0050] [Table 2]

[0051] [Table 3]

[0052] Using the method described above, it is possible to calculate the estimated MFR (Metal Flow Rate) of a resin containing molten recycled material within a flow path.

[0053] <Program> It is preferable to use a computer-based program to calculate the estimated MFR. Furthermore, it is preferable to use such a program to monitor the estimated MFR in real time and output an abnormality signal if the estimated MFR exceeds MFRa or falls below MFRb. Figure 3 shows an example of a program flow chart. By enabling real-time monitoring of the estimated MFR in this way, even if the estimated MFR shows an abnormal value, the abnormality can be detected quickly and countermeasures can be taken, preventing production losses due to the activation of safety devices due to deterioration of fluidity, as well as problems such as molding defects.

[0054] Furthermore, the measurements taken by pressure gauges 9a and 9b may instantaneously record maximum and minimum values ​​due to fluctuations in the state of the molten resin, and it is possible that the estimated MFR may momentarily exceed MFRa or fall below MFRb. Therefore, it is preferable that the program outputs an abnormal signal if the estimated MFR remains above MFRa or below MFRb for a certain period of time (for example, 5 seconds or more).

[0055] The method for calculating the estimated MFR described above can be modified in various ways without departing from the spirit of the present invention.

[0056] For example, in the example shown in Figure 2, high-density polyethylene was used as the resin containing recycled material for calculating the estimated MFR, but it is not limited to this, and any known thermoplastic resin can be used. Examples of the thermoplastic resins include polyolefins such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or random or block copolymers of α-olefins such as ethylene, propylene, 1-butene, and 4-methyl-1-pentene; cyclic olefin resins such as cyclic olefin copolymers and cyclic olefin polymers; ethylene-vinyl acetate copolymers, ethylene-vinyl alcohol copolymers, ethylene-vinyl chloride copolymers, and other ethylene-vinyl compound copolymers; polystyrene, acrylonitrile-styrene copolymers, ABS, and α-methylstyrene-styrene copolymers. Examples include lipids, polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinylidene chloride copolymers, polymethyl polyacrylate, polymethyl methacrylate and other polyvinyl compounds, polyamides such as nylon 6, nylon 6-6, nylon 6-10, nylon 11, and nylon 12, polyesters such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polycarbonates, polyphenylene oxide, and other biodegradable resins such as fluororesins, allyl resins, polyurethane resins, cellulose resins, polysulfone resins, polyethersulfone resins, ketone resins, amino resins, or polylactic acid. Furthermore, blends of these resins and resins modified by copolymerization as appropriate (for example, acid-modified olefin resins) are also included. Among these, low-density polyethylene, high-density polyethylene, or polypropylene are preferred.

[0057] Examples of recycled materials include resins discharged during the manufacturing process of bottles and other items using thermoplastic resins, and resins obtained by crushing and reducing bottles and other items. Alternatively, the resins may be recycled through mechanical recycling or chemical recycling. These resins may be of the same type as the aforementioned thermoplastic resin, or they may be different resins. Furthermore, substances other than resins, such as pigments and additives, may be blended into the materials. In the present invention, the content ratio of the thermoplastic resin to the recycled material is preferably 0:100 to 75:25, and more preferably 0:100 to 35:65.

[0058] In the example shown in Figure 1, the apparatus is configured for direct blow molding using a head unit 5, a parison molding unit 6, and a mold 7. However, it is also possible to replace the head unit 5, parison molding unit 6, and mold 7 with a T-die to create a sheet or film manufacturing apparatus. Furthermore, by replacing the head unit 5, parison molding unit 6, and mold 7 with a die, it is also possible to create a pellet or granulation apparatus.

[0059] In the present invention, it is possible to have a configuration without an orifice (i.e., a straight, equal-diameter flow path 8 without any reduction or expansion of its diameter), but it is preferable to provide an orifice 8c as shown in the example in Figure 1. One advantage of providing an orifice 8c is that the device can be miniaturized. In other words, pressure loss is caused by the frictional force between the molten resin and the inner wall of the flow path, and for accurate calculation of estimated MFR, a larger pressure loss reduces the error, so it is preferable to ensure a pressure loss of a certain level or higher. Here, if the flow path 8 is configured as a straight, equal-diameter flow path without any reduction or expansion of its diameter, a long flow path length is required to ensure a pressure loss of a certain level or higher, which leads to a larger device. Therefore, as shown in Figure 1, by providing an orifice 8c in the flow path 8, the diameter of a part of the flow path can be reduced, and since pressure loss is inversely proportional to the size of the flow path diameter, the pressure loss generated can be increased even with the same flow path length. Thus, by providing an orifice 8c, the flow path length required to obtain a pressure loss of a certain level or higher can be reduced, and the device can be miniaturized.

[0060] In the present invention, the positions of the pressure gauges 9a and 9b can be anywhere within the range of the flow path 8. However, when an orifice section is provided, it is preferable to install the pressure gauges 9a and 9b within the range of the orifice section 8c, as shown in the example in Figure 1, from the viewpoint of accurate measurement. This is because the flow of molten resin is often unstable and turbulent at the positions of the pipe sections 8a and 8e, and if pressure gauges are installed at these positions, the measurement error may become large.

[0061] Furthermore, in the example shown in Figure 2, the estimated MFR was calculated by calculating the reference value of the shear rate γ of the molten resin and identifying the lower limit specified value τmin of the shear stress and the upper limit specified value τmax of the shear stress. In other words, the estimated MFR of the molten resin was calculated by apportioning the proportion on the vertical axis of the graph. However, the estimated MFR may also be calculated by calculating the reference value of the shear stress τ of the molten resin and identifying the lower limit specified value γmin of the shear rate and the upper limit specified value γmax of the shear stress. In other words, the estimated MFR of the molten resin can also be calculated by apportioning the proportion on the horizontal axis of the graph from the reference value of the shear stress τ.

[0062] Furthermore, in the example shown in Figure 1, only one thermometer 10 was installed at a position equidistant from the pressure gauges 9a and 9b. However, from the viewpoint of reducing measurement errors, it is preferable to install two or more thermometers, and two thermometers 10a and 10b may be installed as shown in Figure 4. In this case, the measured temperature Ta is calculated using the average value of the temperatures indicated by thermometers 10a and 10b. As the number of thermometers increases, the measurement error of the temperature decreases, and the calculation of the estimated MFR can be performed more accurately.

[0063] Furthermore, with respect to the thermometer 10, it is preferable that the tip of the thermometer 10 is in direct contact with the molten resin, from the viewpoint of minimizing measurement errors. [Explanation of symbols]

[0064] 1 : Molding equipment 2: Hopper 3: Extruder 4: Measuring part 5: Head section 6: Parison molding section 7: Mold 8: Flow path 9a, 9b: Pressure gauge 10: Thermometer

Claims

1. A method for calculating the estimated MFR (Metal Fluid Ratio) of a resin containing molten recycled material in a flow channel.

2. The pressure loss in the flow path of the molten resin is measured and the following formula (1) τ[Pa]=ΔP×r / 2L (1) In the equation, ΔP is the pressure loss [Pa], r is the radius of the flow path [mm], and L is the length of the flow path [mm]. The shear stress τ is calculated using the following formula (2) c [sec] －１ ]=4Q / 2 ３ (2) In the formula, Q is the flow rate [mm²] ３ / sec], r is the radius of the flow path [mm], The reference value for shear rate γ is calculated accordingly. Using a viscosity measuring device, the lower limit specified value τmin of the shear stress at the reference value of the shear rate γ for MFRa resin and the upper limit specified value τmax of the shear stress at the reference value of the shear rate γ for MFRb resin (which is smaller than MFRa) are measured in advance. The method according to claim 1, wherein the estimated MFR of the molten resin is calculated by using the shear stress τ calculated by formula (1) above and apportioning the difference between the upper limit specified value τmax and the lower limit specified value τmin.

3. The estimated MFR is calculated using the following formula (3) [Math 1] In the formula, τ is the shear stress measured by formula (1), τmax is the upper limit specified shear stress, τmin is the lower limit specified shear stress, and MFRa and MFRb are values ​​satisfying MFRb < MFRa. A method for calculating the estimated MFR according to claim 2, which is calculated by the method described above.

4. The method according to claim 2, wherein the estimated MFR is the average value of MFRa and MFRb.

5. The MFRa and MFRb are given by the following formulas (4) and / or (5) [Math 2] [Math 3] The method according to claim 2 that satisfies the requirements.

6. The method according to claim 1, wherein the molten resin flowing out from the aforementioned channel is used for direct blow molding of a container.

7. A program for causing a computer to perform the calculation of the estimated MFR described in claim 2.

8. The program according to claim 7, which monitors the estimated MFR in real time and outputs an abnormal signal when the estimated MFR becomes MFRa or higher, or when the estimated MFR becomes MFRb or lower.

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