Resin mixtures, preforms, biaxially oriented molded articles, resin pellets, and methods for manufacturing biaxially oriented molded articles

Abstract

To provide a resin mixture that allows for stable stretch blow molding even with PET resins having a molecular weight lower than that of PET resins used for blow molding. [Solution] A resin mixture comprising polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. JPEG2026058846000015.jpg27152 (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.)

Description

Technical Field

[0005] ,

[0004] , , ,

[0006]

[0001] The present disclosure relates to a resin mixture, a preform, a biaxially stretched molded article, resin pellets, and a method for producing a biaxially stretched molded article.

Background Art

[0002] As a container having a bottle shape, since the bottle requires strength such as not breaking even when dropped, a molded article obtained by injection molding a polyethylene terephthalate (hereinafter also referred to as "PET") resin and performing stretch blow molding is used (Patent Document 1).

[0003] In recent years, from the viewpoint of environmental protection, recycling PET bottles as PET bottles again has been widely carried out. Here, as a method for recycling PET, chemical recycling and material recycling as described in paragraphs

[0008] to

[0009] of Patent Document 3 are known.

[0004] Chemical recycling requires multi-step processes as disclosed in Patent Document 2, and thus requires decomposition equipment and polymerization equipment, resulting in high recycling costs. In addition, the environmental impact is also large. On the other hand, the PET resin obtained by material recycling may be hydrolyzed by the absorption of moisture in the air by the PET resin and subsequent heating for pelletization, resulting in a decrease in molecular weight.

[0005] A molded article obtained using a PET resin with a reduced molecular weight may have unstable strength. As a method for compensating for such disadvantages of material recycling, there is mechanical recycling in which a step of repolymerizing to adjust the intrinsic viscosity is added as described in paragraph

[0010] of Patent Document 3. However, solid-phase polymerization known as a method for repolymerizing PET resin also requires a large amount of thermal energy and has a large environmental impact.

[0006] Incidentally, the PET resin used in PET bottles has a molecular weight suitable for blow molding, and this molecular weight is a value called the intrinsic viscosity, or IV value, when PET is dissolved in a solvent. Generally, a viscosity of around 0.70 to 0.85 is used for PET bottles.

[0007] The IV value represents a value dependent on molecular weight. When the IV value is less than 0.69, if an injection-molded product called a preform (a test tube-shaped part) is blow-molded, the low molecular weight causes the preform to crystallize (spherulite) during molding. Because the preform hardens due to crystallization during blow molding, it does not expand and bursts. Even if blow molding is possible, the strength (elastic modulus) of the bottle decreases, and the bottle may break when dropped.

[0008] While recycling PET bottles into other PET bottles is currently practiced, PET resin is used in many other applications, such as sheets and fibers. The PET resin used in these applications almost always has an IV value of less than 0.69, and as mentioned above, it cannot be recycled for use in PET bottles. Therefore, it is mostly recycled into sheets or fibers, or incinerated for thermal recycling.

[0009] However, in order to address environmental problems, plastics should be recycled, and it is desirable to be able to recycle PET resin, even in the form of sheets and fibers, in the form of bottles, which have many uses. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2001-42626 [Patent Document 2] Japanese Patent Publication No. 2000-169623 [Patent Document 3] Japanese Patent Publication No. 2014-198422 [Patent Document 4] Japanese Patent Publication No. 2013-159681 [Overview of the project] [Problems that the invention aims to solve]

[0011] As described above, since the molecular weight of PET resin generated by recycling is lower than that of PET resin used for blow molding, there has been a problem in that it is not possible to manufacture PET containers again from the recycled PET resin by stretch blow molding. Therefore, the purpose of this disclosure is to provide a resin mixture that can be stably stretch blow molded even with PET resin that has a molecular weight lower than that of PET resin used for blow molding. Furthermore, the purpose of this disclosure is to provide resin pellets, preforms, biaxially oriented molded articles, and methods for manufacturing the same. [Means for solving the problem]

[0012] To address the above issues, this disclosure provides: A resin mixture comprising polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), The resin mixture is characterized by having a melt flow rate (MFR) of 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) Furthermore, this disclosure relates to a preform for blow molding, which comprises the above-mentioned resin mixture. Furthermore, this disclosure relates to a biaxially oriented molded article containing the above-mentioned resin mixture. Furthermore, this disclosure relates to resin pellets containing the above-mentioned resin mixture. Furthermore, this disclosure is, The process of creating a preform from a resin mixture, The process of blow-molding the preform and Includes, The resin mixture contains a polyethylene terephthalate resin and a polycarbodiimide represented by the following formula (1), It is a method for manufacturing a biaxially stretched molded article, characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more.

Chemical formula

Advantages of the Invention

[0013] According to one aspect of the present disclosure, a resin mixture capable of stably performing stretch blow molding can be obtained even by using a recycled PET material of a recovered sheet or fiber having an MFR value of 41 g / 10 min or more. Further, according to another aspect of the present disclosure, the resin mixture can be manufactured. According to still another aspect of the present disclosure, a high-quality biaxially stretched blow molded article can be stably manufactured.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic diagram of an image forming apparatus according to the present disclosure. [Figure 2] It is a schematic diagram showing a method for molding a preform according to the present disclosure. [Figure 3] It is a schematic diagram showing a blow molding method according to the present disclosure. [Figure 4] It is a uniaxial stretching S-S curve according to the present disclosure. [Figure 5] It is a sample shape for uniaxial stretching according to the present disclosure. [Figure 6] It is a uniaxial stretching S-S curve of a temperature difference sample according to the present disclosure. [Figure 7] It is a schematic diagram of a biaxial extruder according to the present disclosure. [Figure 8] It is a schematic diagram of one-stage method blow molding according to the present disclosure. [Figure 9] It is a uniaxial stretching S-S curve of Examples 1 to 4 according to the present disclosure. [Figure 10] This is a schematic diagram of the blow-molded bottle related to this disclosure. [Figure 11] These are the uniaxially elongated SS curves of Comparative Examples 1 and 2 relating to this disclosure. [Figure 12] This is a schematic diagram of the pellet shape related to this disclosure. [Modes for carrying out the invention]

[0015] In this disclosure, unless otherwise specified, the expressions "XX or more and YY or less" and "XX to YY" that represent numerical ranges mean numerical ranges including the lower and upper limits which are the endpoints, and when numerical ranges are described in steps, any combination of the upper and lower limits of each numerical range is also disclosed.

[0016] The following describes exemplary embodiments for carrying out this disclosure with reference to the drawings. However, the scope of this invention is not limited to the following embodiments. In the following description, unless otherwise specified, "%" means "mass%".

[0017] According to the inventors' research, recycled PET materials from recovered sheets and fibers (also referred to in this disclosure as "material recycled PET" or "MR-PET") have a low molecular weight, as mentioned above. Furthermore, even recycled materials derived from PET bottles may have their molecular weight reduced through compounding or other processes. Such low-molecular-weight MR-PET forms spherulites very easily because its molecular chains are shortened.

[0018] Therefore, even if a preform formed from MR-PET pellets with a molecular weight, i.e., an IV value of less than 0.69, is to be subjected to biaxial stretch blow molding (also referred to in this disclosure as "stretch blow molding" or "blow molding"), the spherulites of the MR-PET grow rapidly during the stretching process. As a result, the hardness of the preform increases rapidly in certain areas, and parts that cannot keep up with the stretching occur. Consequently, it is believed that the preform will rupture in those areas.

[0019] Alternatively, even if a bottle is formed, stress is concentrated in the areas where spherulites have grown, resulting in reduced strength. Furthermore, low-molecular-weight PET resin does not easily increase in strength when stretched by stretch blow molding. This is thought to be because, due to the low molecular weight, when the molecular chains are stretched, the shorter molecular chains make it difficult for the density of adjacent molecular chains to increase, thus making it difficult for sufficient stretch crystallization to occur.

[0020] Due to these challenges, PET resins for stretch blow molding require an IV value exceeding 0.70. On the other hand, increasing the molecular weight of MR-PET through solid-phase polymerization requires a great deal of energy, as mentioned above. Therefore, we recognized the need to develop a resin mixture that can stably perform stretch blow molding even when using MR-PET with an IV value of less than 0.69.

[0021] In this disclosure, the IV value, which represents a value dependent on the molecular weight of the PET resin, will be expressed using the melt flow rate (MFR) value, which is an indicator of the viscosity of the PET resin mixture when it melts, because the value changes depending on the type of solvent, etc.

[0022] The measurement was performed in accordance with JIS K7210-1:2014, with a measurement temperature of 265°C, a load of 2.16 kg, and the use of a standard die (nominal length 8.000 mm, nominal pore diameter 2.095 mm). The PET composition of this disclosure was dried at 150°C for 5 hours or more, and the time from removal from the dryer to the start of measurement was kept to within 1 minute and 30 seconds. The temperature of 265°C, which is close to the melting point of PET, reduces the effects of hydrolysis. The reason for keeping the time from removal from the dryer to measurement within 1 minute and 30 seconds is to reduce moisture absorption of the PET resin composition and minimize the effects of hydrolysis.

[0023] Furthermore, the shape of the material used to measure MFR can be pellets or preforms, or preforms that have been crushed to a size of about 2-3 mm. If the material is in bottle form, it is preferable to crush it into flakes, compress the flakes using a stick maker manufactured by Toyo Seiki Seisakusho Co., Ltd., and then measure the MFR.

[0024] For the IV value to be less than 0.69 in this MFR, the MFR value is 41g / 10min or higher. At least one aspect of this disclosure aims to provide a resin mixture that enables stable stretch blow molding even when using MR-PET with an MFR of 41 g / 10 min or higher, i.e., a PET resin with a molecular weight lower than that of blow-molded PET resin. Another aspect of this disclosure aims to provide resin pellets, preforms, biaxially oriented molded articles, and methods for manufacturing the same.

[0025] <First Embodiment> The first embodiment relates to a resin mixture. The resin mixture disclosed herein is A resin mixture comprising polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), The resin mixture is characterized by having a melt flow rate (MFR) of 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.)

[0026] (resin mixture) The resin mixture relating to this disclosure satisfies the following two conditions a) and b). Condition a) The resin mixture comprises a polycarbodiimide represented by the following formula (1) and a polyethylene terephthalate resin. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) The number of repetitions n is more preferably 5 to 30, and even more preferably 10 to 30. Condition b) The resin mixture has an MFR of 41 g / min or more.

[0027] Resin mixtures that satisfy conditions a) and b) above suppress the formation of spherulites when stretch blow molding is performed, which can prevent breakage during stretching and a decrease in the strength of the molded product. As mentioned above, when the PET resin molded product that is the source of recycling for MR-PET is a sheet or fiber, the molecular weight is lower than that for blow molding, and even when recycled material is made from bottles, the molecular weight may be lower due to hydrolysis.

[0028] Furthermore, MR-PET that has been reduced in molecular weight to such a degree and has an MFR of 41 g / 10 min or higher is prone to forming spherulites. Therefore, the inventors attempted to modify MR-PET by reacting MR-PET with an MFR of 41 g / 10 min or higher with polycarbodiimide. It is already known, as described in Patent Document 4, that reacting PET with polycarbodiimide improves the hydrolysis resistance of PET.

[0029] However, as a result of the inventors' research, reacting PET with an MFR of 41 g / 10 min or more with polycarbodiimide makes it less likely to crystallize, even if it is a low-molecular-weight MR-PET. As a result, even PET that satisfies condition b) is less likely to break during the stretching process when stretch blow molding.

[0030] The PET relating to condition b) above (hereinafter also referred to as "modified PET") is obtained by reacting PET to be modified (hereinafter also referred to as "unmodified PET") with polycarbodiimide. The unmodified PET may be MR-PET, or it may be virgin PET with a low molecular weight that is not intended for blow molding. However, when MR-PET, which has the problem of easily forming spherulites, is used as the unmodified PET, the effects of this disclosure are more pronounced. The presence and quantification of imide bonds in the modified PET can be done, for example, by measurement using FT-IR.

[0031] When performing stretch blow molding, it is important to understand the stretching properties of the material. However, it is not possible to directly measure the stress during stretching from the blow-molded preform. Thus, it is difficult to confirm how the properties of a biaxially stretched blow-molded product change in the biaxially stretched state, but it is possible to confirm this for uniaxial stretching. Figure 4 illustrates how the properties of PET resin change due to uniaxial stretching.

[0032] (Method for evaluating resin mixtures) This document describes a method for evaluating resin mixtures, specifically a method for producing Charpy strips from PET resin and measuring their properties after uniaxial stretching. First, PET resin is molded into a sample shape (Charpy piece d in Figure 5) in accordance with JIS K7111 using an injection molding machine to obtain an unstretched molded product. In the center of the Charpy piece, as shown in Figure 5, a notch (cut) is created by cutting from both directions (direction e and direction f) using a notching machine (not shown). Cutting is continued until the distance g between the deepest part of the notch created from direction e and the deepest part of the notch created from direction f is 2.00 mm. The angle θ of the notch is set to 45°.

[0033] The shaved Charpy piece (test specimen) is heated with a heat gun until it reaches the normal blow temperature. At this time, the area between the part that is not stretched, i.e., the part that was cut by the notching machine and the part that was chucked by the tensile testing machine, should be protected with insulating sponge or similar material to prevent the temperature from rising. It is preferable that the time it takes to reach the predetermined temperature (e.g., 100°C) with the heat gun be 90 seconds or less.

[0034] When the temperature of the stretched portion reaches a predetermined temperature, a tensile test is performed at a speed of 500 mm / min using a tensile testing machine (Instron 5582; manufactured by Instron) conforming to JIS K7161, and a strain-stress curve, i.e., an SS curve, is output. The resin mixture according to this disclosure preferably has a stress of 2.0 MPa or more and 15.0 MPa or less at the time of 5x stretching, as read from the SS curve. By keeping the stress at 5x stretching within the above range, biaxial stretch blow molding of the preform can be performed more easily. As a result, PET bottles with excellent strength and uniform stretch crystallization can be obtained more easily.

[0035] (Example of evaluation of resin mixtures) As a specific example, Figure 4 shows the SS curves at 100°C for the PET samples a and b below. Sample A: Amorphous sample consisting of 100% PET resin (product name: TN-8550FF; manufactured by Teijin, IV value = 0.77 dL / g). The MFR value of this PET resin was 25 g / 10 min. Sample b: PET resin (product name: TN-8550FF; manufactured by Teijin, IV value = 0.77 dL / g) was extruded using the twin-screw extruder shown in Figure 7 and hydrolyzed, resulting in an MFR value of 48 g / 10 min (equivalent to an IV value of 0.63). Figure 7 shows an apparatus in which a masterbatch pellet 204 containing polycarbodiimide and unmodified PET 203 are fed from a hopper 202 into an extruder 201, heated to above the melting point of PET, specifically above 250°C, and especially above 260°C to melt and knead, then extruded into a string shape, cooled through a water tank 205, and pelletized in a pelletizer 206.

[0036] As shown in Figure 4, the amorphous sample a showed a low strain, i.e., a stress of 2.9 MPa when the stretch ratio reached 5 times, and 5.1 MPa when it reached 10 times. Furthermore, the stretch ratio at which it broke was also very high, exceeding 20 times. This state represents the stress at which the material is easily stretched by a stretching rod during longitudinal stretching using a stretching rod in stretch blow molding, and it can be expanded without bursting even in blow molding.

[0037] Sample b in Figure 4 has a low molecular weight and a fast crystallization rate, so the Charpy piece became cloudy and crystallized when heated with a heat gun. As a result, the stress when the stretch ratio reached 5 times was 19.1 MPa. Furthermore, it fractured when the stretch ratio slightly exceeded 9 times. For this reason, even when attempting to stretch blow mold sample b after actually creating the preform and heating it to 100°C, biaxial stretch blow molding of the preform could not be performed.

[0038] Thus, there is a strong correlation between the crystallization state of PET and its stretch blow moldability, and it is considered that measuring stress during uniaxial stretching after heating to the blow temperature is suitable for determining whether biaxial stretch blow molding is feasible.

[0039] Furthermore, a key feature of this disclosure is that even with PET resins having an MFR of 41 g / 10 min or higher, blow molding at a lower temperature than the normal blow molding temperature improves the strength (mainly the modulus of elasticity) of the blow-molded product. In conventional methods, the strength during stretch blow molding may decrease as the molecular weight of the PET resin decreases. This is because, as the molecular chains of the crystals become shorter (lower molecular weight) due to stretching, the bonds between the crystals weaken, making the crystal portions more susceptible to fracture.

[0040] The solution to this problem is to lower the blow molding temperature. This will be explained below using Figure 6. Sample c: PET (MFR 56g / 10min (equivalent to IV 0.58)) 99.7% Polycarbodiimide (Carbodilite HMV-15CA) 0.3% The above formulation was melt-mixed using a twin-screw extruder (PCM-46, manufactured by Ikegai Co., Ltd.) at 260°C and a screw rotation of 300 rpm. By incorporating polycarbodiimide, the low molecular weight PET polymerized, creating sample c with an MFR of 45 g / 10 min (equivalent to IV 0.65). Sample c was formed into Charpy strips and notched using the same method as samples a and b, and tensile tests were performed at heating temperatures of 100°C, 90°C, and 85°C (Figure 6). Table 1 below shows the stress and the elongation ratio to fracture when the elongation ratio is 5x and 10x.

[0041] [Table 1]

[0042] At a heating temperature of 90°C, the stress at 10x stretching was 10.38 MPa, more than twice the stress at 100°C. At 85°C, the stress was 18.03 MPa, approximately four times that of 100°C. This is thought to be because lowering the temperature during stretching restricts molecular movement, forcing the PET molecular chains to align in the stretching direction, resulting in the formation of a strong stretched crystal.

[0043] Thus, even when PET resin is normally reduced in molecular weight, resulting in a weaker stretched crystal structure, it is possible to mold it without reducing its strength (elastic modulus) depending on the stretching temperature. In the case of samples b, where polycarbodiimide is not included, the reduced molecular weight PET cannot be molded at all, so this effect can only be achieved with the resin composition disclosed herein.

[0044] Furthermore, the feature of this disclosure that lowers the blow temperature means that the amount of energy required to heat the preform can be reduced, thus achieving energy savings, which is one of the goals of recycling, and contributing to the reduction of CO2 emissions.

[0045] Furthermore, the crystallization of the preform in this disclosure is different from the crystallization of the stretched form. The crystal of the preform is an isothermal crystal (spherulite) and is opaque, while the stretched crystal is transparent. Although both are called crystals, isothermal crystals are formed when molecular chains are folded, while stretched crystals are formed when molecular chains are stretched in the stretching direction, causing them to be regularly arranged in that direction and increasing density. Therefore, their crystal shapes are significantly different.

[0046] Furthermore, while isothermal crystals are formed differently depending on temperature and time, stretched crystals are formed when the crystal is stretched, and the stretching time is only about 1 second, so crystallization is completed in a short time. Thus, isothermal crystals and stretched crystals are very different, and in this disclosure, it is not inconsistent that stretched crystals can be formed even in materials where isothermal crystallization is unlikely.

[0047] Preferably, when a Charpy test is performed on a Charpy sample of the resin mixture of this disclosure at 90°C, the tensile stress at a stretch ratio of 10 times is twice or more than the tensile stress at a stretch ratio of 2 times. Furthermore, preferably, when a tensile test is performed on a Charpy sample of the resin mixture of this disclosure at 85°C, the tensile stress at a stretch ratio of 10 times is twice or more than the tensile stress at a stretch ratio of 2 times. By doing so, more stable blow molding can be performed using the resin mixture of this disclosure, and higher quality PET containers can be obtained.

[0048] (PET) PET is obtained by a condensation reaction or transesterification reaction between terephthalic acid or its ester-forming derivative and 1,2-ethanediol or its ester-forming derivative. It may be either copolymerized PET or homopolymer.

[0049] (Polycarbodiimide) As described above, the modified PET relating to this disclosure is obtained by reacting PET with polycarbodiimide. The polycarbodiimide used for modification has two or more carbodiimide groups represented as "-N=C=N-" in its molecule.

[0050] The presence of two or more carbodiimide groups allows for the linking of two or more PET molecules, thus increasing the apparent molecular weight. This suppresses crystallization. Furthermore, in the state of equation (1), the structure linked to the PET molecule forms a so-called comb shape, making it a structure less prone to crystallization. Polycarbodiimide can be produced, for example, by heating an organic isocyanate in the presence of a catalyst and undergoing a decarboxylation reaction.

[0051] Examples of such organic isocyanates include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Specific examples of polycarbodiimides include aromatic polycarbodiimides such as poly(4,4'-diphenylmethanecarbodiimide), poly(p-phenylenecarbodiimide), poly(m-phenylenecarbodiimide), poly(diisopropylphenylcarbodiimide), and poly(triisopropylphenylcarbodiimide), as well as alicyclic polycarbodiimides such as poly(dicyclohexylmethanecarbodiimide).

[0052] These polycarbodiimides may be used individually or in any combination of two or more. Among these polycarbodiimides, aliphatic polycarbodiimides are preferred from the viewpoint of further reducing the density of the modified PET.

[0053] Aliphatic polycarbodiimides are commercially available, for example, as "Carbodilite HMV-15CA," "Carbodilite LA-1," and "Carbodilite HMV-5CA-LC" (all are trade names, manufactured by Nisshinbo Chemical Co., Ltd.).

[0054] The amount of polycarbodiimide added to unmodified PET is preferably 0.02 parts by mass or more and 1.0 part by mass or less, when the amount of unmodified PET is 100 parts by mass. If the amount is less than 0.02 parts by mass, the effect of preventing crystallization will be reduced, which is undesirable. If it exceeds 1.0 part by mass, the molecular weight will increase too much, and if the molding temperature is lowered, the initial stress during stretching will increase, making it prone to bursting, similar to crystallization, which is also undesirable.

[0055] One method for reacting polycarbodiimide with unmodified PET is to heat a mixture of polycarbodiimide and unmodified PET using an extruder to a temperature above the melting point of PET, specifically 250°C or higher, and especially 260°C or higher, to melt and knead the mixture. Alternatively, since polycarbodiimide is in powder form, when reacting with an injection molding machine, a masterbatch may be used, which is made by diluting and kneading polycarbodiimide with PET resin to form pellets.

[0056] Furthermore, methods for confirming the presence of polycarbodiimide in the resin composition of this disclosure include, but are not limited to, XPS (X-ray electron spectroscopy) and FT-IR (Fourier transform infrared spectroscopy). Also, when performing analysis, the analysis may be conducted not only on blow-molded products (biaxially oriented molded products) as described later, but also on preforms and resin pellets.

[0057] <Resin pellets> The resin pellets of this disclosure include the resin mixture of this disclosure. Resin pellets are obtained by, for example, melting the resin mixture of this disclosure in a resin extruder (single-screw, twin-screw, etc.), extruding it into a string-like shape (also called a strand), cooling it in a water tank or the like, and then cutting it into granules with a cutting device called a strand cutter.

[0058] <Preform> The preforms of this disclosure are preforms for blow molding and include the resin mixture of this disclosure. A preform is an intermediate product manufactured for biaxial stretch molding from the resin mixture or resin pellets of this disclosure, and is, for example, in the shape of a test tube. This preform can be placed in a mold and blown while heated to expand the preform in the mold and produce a biaxially stretched molded product.

[0059] <Biaxially stretched molded product> The biaxially oriented molded articles of this disclosure include the resin mixture of this disclosure. The biaxially oriented molded articles of this disclosure are produced by blow molding a preform of this disclosure into which gas is introduced while the preform of this disclosure is at a predetermined temperature (for example, around 100°C for PET resin), thereby increasing the overall length and diameter of the preform. There are two types of uniaxial stretching: one in which the overall length is increased, and another in which the diameter is increased. A molded article that exhibits both of these uniaxial stretching processes is called a biaxially oriented molded article. Typical biaxially oriented molded articles include PET bottles for beverages, PET bottles for soy sauce and cosmetics, and PET bottles for various containers such as toner containers for photocopiers. This disclosure can be used for these applications.

[0060] <Toner Bottle> Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram illustrating the configuration of a four-color image forming apparatus using an electrophotographic method, where 80 is the main body of the image forming apparatus. This image forming apparatus 80 is configured as a so-called intermediate transfer tandem type image forming apparatus, in which four color image forming units are arranged side by side on an intermediate transfer belt.

[0061] In this image forming apparatus 80, image formation is performed as follows. First, based on the print data, the image forming apparatus 80 uses an exposure unit 50 (50y, 50m, 50c, 50bk) to form an electrostatic latent image on the photosensitive drum 17 (17y, 17m, 17c, 17bk). Then, the image forming apparatus 80 develops the formed electrostatic latent image using a developing unit 21 (21y, 21m, 21c, 21bk) to form a toner image.

[0062] In this image forming apparatus 80, the toner image is transferred onto an intermediate transfer body 62 by a primary transfer device 60 (60y, 60m, 60c, 60bk), and then transferred onto a sheet material S supplied from a paper feed device 63 by a secondary transfer unit 64 (64a, 64b). Next, in this image forming apparatus 80, the toner image transferred onto the sheet material S is fixed to the sheet material S by a fixing means 68, and then discharged onto a paper output tray 70.

[0063] Furthermore, in this image forming apparatus 80, a toner image is formed in the developing apparatus 21, and a detachable toner bottle 3 (3Y, 3M, 3C, 3Bk) is used to supply toner to the developing apparatus 21. The toner bottle of this disclosure is a toner bottle 3 used in this manner.

[0064] <Second Embodiment> The second embodiment relates to a method for manufacturing a biaxially stretched molded product. The method for manufacturing a biaxially stretched molded article according to this disclosure is: The process of creating a preform from a resin mixture, The process of blow-molding the preform and Includes, The resin mixture comprises polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), The resin mixture is characterized by having a melt flow rate (MFR) of 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) In the following sections, items described in the first embodiment may be omitted to avoid repetition.

[0065] The use of the PET bottles described herein is explained below as a toner bottle for use in electrophotography (image forming apparatus). One embodiment of a method for manufacturing a toner bottle by biaxial stretch blow molding using the resin mixture relating to this disclosure is described below.

[0066] (The process of creating a preform from a resin mixture) The present disclosure's method for manufacturing an axially stretched molded article includes a step of preparing a preform from a resin mixture. First, as shown in Figure 2, a preform 104 having a test tube-like shape is molded by injection molding. The preform is an injection molded article required in an intermediate step of biaxial stretch blow molding, and high-pressure gas is introduced from this test tube state to form a container shape. Specifically, the preform molding method involves a heating cylinder 105 heating the material fed into the injection molding machine 101 to a molten state, and an extrusion screw 207 injecting the molten material into preform molds 102 and 103 to mold the preform 104.

[0067] (The process of blow-molding the preform) The method for manufacturing an axially stretched molded product according to this disclosure includes a step of blow molding a preform. Next, as shown in Figure 3, biaxial stretch blow molding is performed. First, the preform 104 is placed in a heating furnace 107 and heated to a temperature at which it can be stretched. The heating time at this time is preferably 3 minutes or less. By limiting the heating time to 3 minutes or less, it is possible to prevent the crystallization of crystalline polyester from progressing inside the preform during heating. After heating, the heated preform 104 is removed from the heating furnace 107 and placed in the mouth of a blow mold 108, which has a cavity formed inside by combining the left mold 108-1 and the right mold 108-2.

[0068] A heated preform placed inside a blow mold 108 is stretched longitudinally using a stretching rod 109. This stretching is called primary stretching. At this time, it is preferable to introduce gas so that the preform 104 does not come into contact with the stretching rod 109, and the pressure of this gas is called the primary blow pressure.

[0069] After the primary stretching, gas 110 is introduced through the preform opening 106 to expand the preform laterally (circumferentially). This is called secondary stretching. The gas pressure at this time is called the secondary blow pressure. Examples of gases to be injected include air, nitrogen, carbon dioxide, and argon.

[0070] Through these primary and secondary stretching processes, the preform 104 expands in the directions indicated by the arrows 301, adhering tightly to the inner wall of the blow mold 108, where it cools and solidifies. Next, the blow-molded product 112 is removed from the blow mold 108 by separating the left mold 108-1 and the right mold 108-2. Because this blow-molded product 112 is stretched in both the longitudinal and transverse directions, it becomes a molded product with high strength.

[0071] Thus, in the stretching process of injection stretch blow molding, it is important that the preform is in an amorphous state (non-crystalline). If it is in an amorphous state and at the blow molding temperature, blowing, or biaxial stretching, will cause the PET to stretch and crystallize in the direction of stretching, making it possible to form a high-strength bottle.

[0072] There are two methods for injection stretch blow molding: the one-stage method and the two-stage method. The one-stage method uses the residual heat of the preform immediately after removal from the mold to perform stretch blow molding, either directly or with controlled temperature. The two-stage method involves cooling the preform to room temperature, and then reheating and stretch blow molding the preform again.

[0073] In the one-stage method, as shown in Figure 8, a preform 104 is injected from an injection molding machine 101. To prevent the preform 104 from falling below the glass transition temperature of PET, cooling is completed in a short time of 10 seconds or less during injection molding. Then, it is immediately heated to a blow molding temperature (e.g., 100°C) and blow molded to obtain a blow-molded product 112. An integrated injection molding apparatus and blow molding apparatus is used.

[0074] The two-stage method involves injection molding a preform, then cooling and removing the preform below the glass transition temperature of PET, and finally heating it to the blow molding temperature (e.g., 100°C) in a separate blow molding apparatus to perform blow molding. This method utilizes a system where the injection molding apparatus and the blow molding apparatus are separate.

[0075] The one-stage method is preferable because it does not require the energy of reheating compared to the two-stage method, as the preform is not cooled below the glass transition temperature. However, after injection molding, the longer time the PET is held at its crystallization temperature makes it easier for the isothermal crystals of the low-molecular-weight PET to crystallize.

[0076] Therefore, the resin composition disclosed herein exhibits the effect of being less susceptible to isothermal crystallization in both the one-stage and two-stage methods, but the effect is particularly high in the one-stage method due to its faster crystallization rate. Furthermore, even with a two-stage process, crystallization occurs if the heating time is prolonged, which also increases the effectiveness in that case. A preferred method for producing the PET resin composition with an MFR of 41 g / 10 min or more used in this disclosure is a method using a twin-screw extruder.

[0077] Recycled materials mainly consist of PET bottles and PET films collected from the market. These are crushed, washed, and then distributed as flakes. These flakes do not easily get caught in the screw of an injection molding machine if fed directly into it. Therefore, they are fed into a twin-screw extruder, plasticized, and formed into pellets. Once formed into pellets, they have a shape similar to virgin PET pellets, making them easier to get caught in the screw of an injection molding machine.

[0078] However, while commercially available virgin PET resin is solid-phase polymerized, the extruded pellets have a low degree of crystallinity. The degree of crystallinity in solid-phase polymerization is about 61-63% by density method, but the degree of crystallinity in the extruded state is almost 0%. If left as is, when placed in a dryer before molding, the pellets will soften when the temperature exceeds the glass transition temperature, causing them to stick together and form a lumpy substance in which the pellets retain their individual shapes. Therefore, the extruded pellets need to be crystallized.

[0079] Normally, crystallization is carried out at around 150°C while stirring the pellets, and the degree of crystallization at this time is about 35%. In this state, even if the pellets are put into a dryer and dried, they will not form the aforementioned lumpy substance.

[0080] However, when the pellets of this disclosure were crystallized at 150°C, they did not form lumps, but during injection molding, the engagement with the screw was sometimes unstable. Therefore, when the degree of crystallinity was increased to 40% or higher, the engagement became stable. Thus, it is preferable that the pelletized PET resin composition used in this disclosure has a degree of crystallinity of 40% or higher.

[0081] To increase the degree of crystallinity, it is advisable to raise the temperature during the crystallization process. Specifically, to achieve a crystallinity of 40% or more, a temperature of 180°C or higher is preferable. While increasing the temperature increases the degree of crystallinity, PET will oxidize and degrade if the temperature exceeds 200°C, so the upper limit temperature for crystallization should preferably be below 200°C.

[0082] It was also found that pellet size contributes to chewing stability. Although the pellets are cylindrical, they are also elliptical as shown in Figure 12, so chewing stability deteriorates when the length of the major axis, minor axis, and cylindrical length are such that the minor axis length is less than 2 mm. The preferred pellet size range is one in which the short axis length is 2 mm or more, the long axis length is 3 mm or more, and the cylindrical length is 3 mm or more.

[0083] (others) The method for manufacturing a biaxially oriented molded article according to this disclosure comprises a resin mixture containing polyethylene terephthalate resin and a polycarbodiimide represented by the following formula (1), wherein the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) [Examples]

[0084] The present disclosure will be described in detail below with reference to examples and comparative examples. However, the present disclosure is not limited to these examples. In the examples and comparative examples, the following items were measured and evaluated. In the following examples, unless otherwise specified, "%" means "mass%".

[0085] (Example 1) <Production of recycled pellets> PET bottles that had been used for beverages in the market and then collected were crushed into flakes approximately 5-10 mm square using a crusher. After washing these flakes, they were melt-kneaded using a twin-screw extruder (PC-46, manufactured by Ikegai Co., Ltd.) at a temperature of 260°C, a screw rotation speed of 200 rpm, and a discharge rate of 100 kg / h, according to the mixing ratios shown in Table 2 below, and then pelletized.

[0086] [Table 2]

[0087] The MFR value of this pellet was 42 g / 10 min (equivalent to IV of 0.68). Crystallization was performed by maintaining a temperature of 180°C for 3 hours. The degree of crystallinity was 42%. The average size of 10 pellets measured was 3.2 mm in major diameter, 2.3 mm in minor diameter, and 3.3 mm in length. This is referred to as MR-PET pellet (a).

[0088] A sample of the obtained pellet (a) was prepared for the tensile test described above, and a tensile test was performed at 100°C to create an SS curve. The results are shown in Figure 9. From this, the stress at 5 times elongation was calculated. The result was 2.92 MPa.

[0089] <Making toner bottles> A toner bottle 3 (total length 439.5 mm, diameter 101 mm) shown in Figure 10 was manufactured using a one-stage blow molding machine (ASB-70DPH, manufactured by Nissei ASB Machinery Co., Ltd.). The blow stretching ratio was set to "longitudinal ratio × transverse ratio = 6.7". The "longitudinal ratio" of the blow-stretch ratio is calculated by dividing the "total length after stretching" by the "total length (before stretching) of the part of the preform that reaches the stretching temperature (heated part)." The "lateral ratio" of the blow-drying stretch ratio is calculated by dividing the "diameter of the middle section after stretching" by the "diameter of the middle section of the preform (before stretching)".

[0090] <Blow molding conditions> The resin mixture pellets dried as described above were fed into the extrusion molding device of a one-stage stretch blow molding machine (product name: ASB-70DPH; manufactured by Nissei ASB Machine Co., Ltd.), and toner bottles were formed by biaxial stretch blow molding. The one-stage stretch blow molding machine described above can perform the process of obtaining a test tube-shaped preform by injection molding and the process of obtaining a bottle-shaped molded product by biaxial stretch blow molding of the preform in a continuous manner. The screw diameter of the injection molding machine in this molding machine was 54 mm.

[0091] First, a mold was prepared for molding preforms with an outer diameter of 30 mm, a wall thickness of 3.7 mm, and a length of 220 mm. Then, the preforms were molded under the following molding conditions. Screw diameter: 54mm • Screw position before filling the cavity with resin mixture: 95mm ·Injection speed Until the propeller is advanced 5mm: 50% of maximum speed Until the propeller is advanced another 20mm: 30% of maximum speed Until the propeller is advanced another 35mm: 25% of maximum speed PV switching position: 35mm · Injection pressure • PV switchover time: 12.0 MPa • After switching to PV: 4.5 MPa (holding pressure) • Holding pressure time after PV switchover ·4.57 seconds ·Heating tube temperature: 280℃ ·Cooling time: 8.0 seconds • Mold temperature: 18℃

[0092] After a cooling time of 8.0 seconds, the preform was demolded and transported to the biaxial stretch blow station of the one-stage stretch blow molding machine. The temperature of the preform during transport was controlled as follows. • Preform heating temperature 170°C, 10% of the preform's total length from the top of the preform. 190°C, 25% of the preform's total length from the top of the preform. 190°C, 50% of the preform's total length, from the top of the preform. 170°C, 75% of the preform's total length, from the top of the preform.

[0093] Next, the preform, adjusted to the above temperature, was placed in a cylindrical mold sized to match the toner bottle size and adjusted to a temperature of 18°C, and a blow-molded bottle was created by biaxial stretch blow molding. During transport, the preform was heated, and the surface temperature of the center of the preform just before being placed in the cylindrical mold was 95°C.

[0094] First, the stretching rod was inserted into the preform from its retracted position through the opening and advanced until it contacted the top of the preform. Next, the stretching rod was further advanced with an air pressure of 1.2 MPa driving it. Then, 0.5 seconds after the start of the further advancement of the stretching rod, primary air was introduced into the preform through the opening. The pressure of the primary air was set to 1.0 MPa.

[0095] Next, secondary air was introduced 0.15 seconds after the primary air was introduced. The pressure of the secondary air was set to 2.9 MPa. Then, air was introduced into the preform for 7.0 seconds from the start of the primary air introduction. Subsequently, the pressure inside the preform was returned to atmospheric pressure over 2.5 seconds. In this way, a blow-molded bottle was formed.

[0096] As a result, the blow-molded bottles could be formed without the preforms rupturing during the process. Furthermore, visual inspection of the resulting blow-molded bottles revealed no distortion caused by the formation of PET spherulites. When the central part of this bottle was cut out and its tensile modulus was measured, it was found to be 4050 MPa, indicating high strength.

[0097] (Example 2) <Production of recycled pellets> PET film that had been used in the market and then recovered was crushed into flakes approximately 5-10 mm square using a pulverizer. These flakes were then melt-kneaded using a twin-screw extruder (PC-46, manufactured by Ikegai Co., Ltd.) at a temperature of 260°C, a screw rotation speed of 200 rpm, and a discharge rate of 100 kg / h, according to the mixing ratios shown in Table 3 below, and then pelletized.

[0098] [Table 3]

[0099] The MFR value of this pellet was 54 g / 10 min (equivalent to an IV of 0.59). Crystallization was performed by maintaining a temperature of 180°C for 3 hours. The degree of crystallinity was 43%. The average size of 10 pellets measured was 3.1 mm in major diameter, 2.2 mm in minor diameter, and 3.2 mm in length. This is referred to as MR-PET pellet (b).

[0100] A sample of the obtained pellet (b) was prepared for the tensile test described above, and a tensile test was performed at 100°C to create an SS curve and calculate the stress at 5x stretching. The result was 1.72 MPa. The stress at 10x stretching was 2.69 MPa. At 100°C, the stress change from 5x to 10x stretching was 1.56 times, which was a small change, so it is thought that stretch crystallization did not occur much.

[0101] <Making blow-molded bottles> Except for using resin mixture No. 1, biaxial stretch blow molding was performed using the aforementioned one-stage stretch blow molding machine under the same blow molding conditions as described above. As a result, blow bottles could be molded without the preform bursting during the process.

[0102] When the central part of this bottle was cut out and its tensile modulus was measured, it was found to be 2500 MPa. As indicated by the SS measurement, it is possible to mold it, but it is thought that only a small amount of stretched crystals have formed.

[0103] (Example 3) A sample of pellet (b) was prepared for the aforementioned tensile test, and a tensile test was performed at 90°C to create an SS curve and calculate the stress at 5x stretching. The result was 3.61 MPa. Furthermore, the stress at 10x stretching was 7.26 MPa. At 90°C, the stress change from 5x to 10x stretching was 2.01 times, which is a larger change than at 100°C. Moreover, the absolute value of the stress at 10x stretching was 7.26 MPa compared to 2.69 MPa at 100°C, suggesting that stretch crystals were formed and the bottle strength increased.

[0104] Furthermore, the pellets (b) were molded into blow bottles in the same manner as in Example 2, but the preform heating temperature was changed as follows. 168°C, 10% of the preform's total length from the top of the preform. 187°C, 25% of the preform's total length from the top of the preform. 187°C, 50% of the preform's total length from the top of the preform. 168°C, 75% of the preform's total length from the top of the preform.

[0105] As a result, the surface temperature of the center of the preform just before it was placed inside the cylindrical mold was 90°C. When the central part of this bottle was cut out and its tensile modulus was measured, it was found to be 3500 MPa, which is higher than the modulus in Example 2. This is thought to be because the stretched crystals became stronger due to the 5°C decrease in the blow molding temperature.

[0106] (Example 4) A sample of pellet (b) was prepared for the aforementioned tensile test, and a tensile test was performed at 85°C to create an SS curve and calculate the stress at 5x stretching. The result was 5.56 MPa. The stress at 10x stretching was 14.64 MPa. At 90°C, the stress change from 5x to 10x stretching was 2.63 times, which is a larger change than at 100°C. Furthermore, the absolute value of the stress at 10x stretching was 14.64 MPa compared to 2.69 MPa at 100°C, which is more than twice the stress at 5x stretching. This result suggests that the degree of crystallinity of the stretched crystals will further increase and form, leading to an increase in bottle strength.

[0107] Furthermore, the pellets (b) were molded into blow bottles in the same manner as in Example 2, but the preform heating temperature was changed as follows. 165°C, 10% of the preform's total length from the top of the preform. 185°C, 25% of the preform's total length from the top of the preform. 185°C, 50% of the preform's total length from the top of the preform. 165°C, 75% of the preform's total length from the top of the preform. As a result, the surface temperature of the center of the preform just before it was placed inside the cylindrical mold was 85°C.

[0108] When the central part of this bottle was cut out and its tensile modulus was measured, it was found to be 3900 MPa, which is the same modulus as in Example 1. From this result, it was found that even with recycled PET for film with a high MFR value, i.e., low molecular weight, it is possible to create blow-molded products with sufficient strength even without a high IV for blow molding by lowering the blow molding temperature by 15°C compared to Example 2.

[0109] (Comparative Example 1) Only the recovered PET bottle flakes used in Example 1 were melted and kneaded using a twin-screw extruder (PC-46, manufactured by Ikegai Co., Ltd.) at a temperature of 260°C, a screw rotation speed of 200 rpm, and a discharge rate of 100 kg / h, and then pelletized to form pellet (c). The MFR value of this pellet (c) was 49 g / 10 min (IV equivalent to 0.62), and it was crystallized by maintaining a temperature of 150°C for 3 hours. The degree of crystallinity was 35%. The average size of 10 pellets measured was a major diameter of 2.8 mm, a minor diameter of 1.8 mm, and a length of 3.0 mm. This is referred to as MR-PET pellet (c).

[0110] A sample of pellet (c) was prepared for the aforementioned tensile test, and a tensile test was performed at 100°C to create an SS curve. The results are shown in Figure 11. From this, the stress at 5 times the normal stretch was calculated. The result was 19.58 MPa. The stress at 10 times the normal stretch was 26.79 MPa. The high stress at 5 times the normal stretch suggests isothermal crystallization, and the result indicates that it will burst when blown, as it no longer stretches.

[0111] A blow bottle was prepared using pellet (c) in the same manner as in Example 1. However, the metering was unstable during injection molding. Although blow molding was then attempted, the preform burst while being stretched in one axial direction with a stretching rod, making blow molding impossible.

[0112] (Comparative Example 2) Only the recovered PET film flakes used in Example 2 were melt-kneaded using a twin-screw extruder (PC-46, manufactured by Ikegai Co., Ltd.) at a temperature of 260°C, a screw rotation speed of 200 rpm, and an extrusion rate of 100 kg / h, and then pelletized to form pellet (d). The MFR value of this pellet (d) was 72 g / 10 min (equivalent to IV of 0.48), and it was crystallized by maintaining a temperature of 150°C for 3 hours. The degree of crystallinity was 35%. The average pellet size measured from 10 pellets was 2.7 mm in major diameter, 1.9 mm in minor diameter, and 2.8 mm in length.

[0113] A sample of pellet (d) was prepared for the tensile test described above, and a tensile test was performed at 100°C to create an SS curve. The results are shown in Figure 11. From this, the stress at 5 times the normal stretch was calculated. The result was 24.56 MPa. Furthermore, it fractured without being able to be stretched 10 times. The extremely high stress at 5 times the normal stretch suggests isothermal crystallization, and the result indicates that it will burst when blown, as it no longer stretches.

[0114] A blow-molded bottle was prepared using this pellet (d) in the same manner as in Example 1. However, metering was unstable during injection molding. Although blow molding was then attempted, the preform burst while being stretched in one axial direction with a stretching rod, making blow molding impossible. In addition, the screw stopped midway through injection molding, making molding impossible.

[0115] This embodiment includes the following configurations and methods. (Composition 1) A resin mixture comprising polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), A resin mixture characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) (Configuration 2) A preform for blow molding, A preform comprising the resin mixture described in Composition 1. (Composition 3) A biaxially oriented molded article containing the resin mixture described in Composition 1. (Composition 4) A resin pellet comprising the resin mixture described in Composition 1. (Composition 5) The resin mixture according to Configuration 1, wherein when a Charpy piece is subjected to a tensile test at 90°C, the tensile stress at a stretch ratio of 10 times is greater than or equal to the tensile stress at a stretch ratio of 2 times. (Composition 6) The resin mixture according to composition 1 or 2, wherein when a Charpy piece is subjected to a tensile test at 85°C, the tensile stress at a stretch ratio of 10 times is twice or more than the tensile stress at a stretch ratio of 2 times. (Method 1) The process of creating a preform from a resin mixture, The process of blow-molding the preform and Includes, The resin mixture comprises polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), A method for producing a biaxially oriented molded article, characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. [ka] (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.) [Explanation of symbols]

[0116] 3 Toner Bottles 17 Photosensitive drum 21 Developing device 50 Exposure apparatus 60 Primary Transfer Apparatus 62 Intermediate Transfer Form 64 Secondary transfer section 68 Fixing means 80 Image forming apparatus 104 Preform 112 Blow molded product d Charpy crumbs

Claims

1. A resin mixture comprising polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), A resin mixture characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. 【Chemistry 1】 (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.)

2. A preform for blow molding, A preform comprising the resin mixture described in claim 1.

3. A biaxially oriented molded article comprising the resin mixture described in claim 1.

4. A resin pellet comprising the resin mixture described in claim 1.

5. The resin mixture according to claim 1, wherein when a Charpy piece is subjected to a tensile test at 90°C, the tensile stress at a stretch ratio of 10 times is twice or more than the tensile stress at a stretch ratio of 2 times.

6. The resin mixture according to claim 1, wherein when a Charpy piece is subjected to a tensile test at 85°C, the tensile stress at a stretch ratio of 10 is 2 times or more than the tensile stress at a stretch ratio of 2.

7. The process of creating a preform from a resin mixture, The process of blow-molding the preform and Includes, The resin mixture comprises polyethylene terephthalate resin and polycarbodiimide represented by the following formula (1), A method for producing a biaxially oriented molded article, characterized in that the melt flow rate (MFR) of the resin mixture is 41 g / 10 min or more. 【Chemistry 2】 (In formula (1), R is an alkylene group having 1 to 12 carbon atoms, and n is an integer between 2 and 100.)

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