Method of manufacturing preform, and method of manufacturing container made of polyester-based resin

Abstract

To efficiently enhance a crystallinity with a smaller amount of heat when enhancing a crystallinity of a mouth portion of a molded preform.SOLUTION: A method of manufacturing a preform is characterized by recovering a powdery granular material generated in a process of recycling a polyester-based resin molded article, adding fine particles with an average particle diameter of 1 mm or less contained in the recovered powdery granular material to a polyester-based resin as a main raw material in a ratio of 0.1 wt% or more to prepare a molding material, and molding the preform by using the molding material.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a preform for blow molding a polyester-based resin container, and a method for producing a polyester-based resin container. [Background technology]

[0002] Conventionally, polyester-based resin containers have been known which are produced by preparing a preform using a polyester-based resin such as polyethylene terephthalate and then molding this preform into a predetermined container shape by biaxial stretch blow molding, etc. This type of container is generally called a PET bottle, and is used in a wide range of fields as a container for various beverages, various seasonings, etc.

[0003] Furthermore, one known method for filling this type of container with contents is to fill the container with heat-sterilized contents while the contents are still hot. In containers used for such purposes, the mouth of the container is heat-treated to increase the crystallinity and improve heat resistance so that the heat from the contents does not cause deformation of the mouth of the container and impair its sealing ability (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-260197 Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the background art, the inventors of the present invention have conducted extensive research to find a way to increase the crystallinity of the mouth portion efficiently with less heat, and as a result have completed the present invention. [Means for solving the problem]

[0006] The method for manufacturing a preform according to the present invention involves recovering powder and granular material generated in the process of recycling polyester-based resin molded products, adding fine particles with an average particle size of 1 mm or less contained in the recovered powder and granular material to a polyester-based resin as the main raw material in a proportion of 0.1% by weight or more to prepare a molding material, and then molding a preform using the molding material.

[0007] In addition, the method for manufacturing a polyester-based resin container according to the present invention is a method in which the mouth of a preform manufactured by the above-mentioned preform manufacturing method is heat-treated to increase the crystallinity, and then the preform is blow-molded. [Effects of the Invention]

[0008] According to the present invention, when increasing the crystallinity of the mouth portion of a molded preform, the crystallinity can be increased efficiently with a smaller amount of heat. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present invention will now be described.

[0010] In this embodiment, polyester resin molded products, preferably PET bottles, are targeted for recycling, and powders generated during the recycling process are collected.

[0011] Generally, methods for recycling PET bottles include material recycling, which recycles PET bottles into raw materials such as fibers or films (cascade recycling), mechanical recycling, which recycles PET bottles into raw materials for new PET bottles (horizontal recycling / bottle-to-bottle), and chemical recycling. In all of these methods, the PET bottles to be recycled are washed and crushed into flakes, and then treated according to the respective method. In this embodiment, there is technical significance in recovering and effectively utilizing powder and granules generated during such recycling processes. However, powder and granules generated from pre-consumer materials for polyester resin molded products can also be used in combination, and such powder and granules can be effectively utilized as recycled materials.

[0012] Most of the powder and granular material generated during the recycling process is generated when polyester resin molded products such as PET bottles to be recycled are crushed, but the powder and granular material to be collected may be any material originating from the material to be recycled. This does not necessarily mean that the powder and granular material is collected from a crushing device that crushes the material to be recycled, but it may also be powder and granular material collected from a bag filter of a dryer or dust collector. The powder and granular material collected from a crushing device that crushes the material to be recycled contains powder and granular material of various particle sizes, but the powder and granular material collected from a bag filter of a dryer or dust collector is often composed of relatively uniform fine particles.

[0013] In this embodiment, a molding material is prepared by adding fine particles having an average particle size of 1 mm or less contained in the recovered powder and granules to a polyester resin as a main raw material. If necessary, the recovered powder and granules are preferably classified into fine particles having an average particle size of 1 mm or less by sieving or the like before addition. A preform is then molded using the molding material prepared in this manner. To mold a preform, for example, the polyester resin as a main raw material and the fine particles having an average particle size of 1 mm or less contained in the recovered powder and granules are charged together or separately into an injection unit, melt-kneaded, and then injected into a preform mold.

[0014] When a test piece was cut from the preform thus molded and subjected to differential scanning calorimetry, the crystallization exothermic peak temperature (Tc1(2nd)) during heating, as determined from the DSC curve obtained by the second differential scanning calorimetry, was found to be lower than that of a preform molded without the addition of fine particles with an average particle size of 1 mm or less contained in the recovered powder. Therefore, when increasing the crystallinity of the mouth of the molded preform, it is possible to efficiently increase the crystallinity with less heat. This is presumably due to the action of the added fine particles as crystal nuclei.

[0015] Examples of polyester resins used as main raw materials include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polyethylene furanoate, and copolymers thereof. These polyester resins may be copolymerization products of chemically synthesized diol components and dicarboxylic acid components, or may be polyester resins with an increased biomass content, such as those using ethylene glycol or derivatives thereof derived from plant-derived bioethanol as the diol component, terephthalic acid or derivatives thereof derived from plant-derived bioparaxylene as the dicarboxylic acid component, or furandicarboxylic acid or derivatives thereof derived from plant-derived fructose as the dicarboxylic acid component.

[0016] When fine particles having an average particle size of 1 mm or less contained in the recovered powder or granules are added to such a polyester resin, the amount added is 0.1 wt % or more, preferably 0.3 wt % or more, and the upper limit of the amount added is preferably less than 2.0 wt %. If the amount of fine particles added is too small, the desired effect cannot be obtained, and if the amount of fine particles added is too large, whitening tends to occur easily in the body of the molded container when the preform is blow molded. When adding fine particles with an average particle size of 1 mm or less contained in the recovered powder or granular material, as long as the fine particles with an average particle size of 1 mm or less are added in the above-mentioned amount, powder or granular material with an average particle size exceeding 1 mm may be mixed in as long as it does not interfere with molding.

[0017] To blow mold a preform, it is heated to soften it so that it can be blow molded, and then set in a blow mold. Then, for example, the portion directly below the mouth of the preform supported by the blow mold is used as the starting point for stretching, and the preform is stretched in the axial direction by a stretching rod while being stretched in the axial and radial directions by blow air, thereby transferring the cavity shape of the blow mold to the stretched portion, and a container having a predetermined container shape can be blow molded.

[0018] In this case, prior to blow molding the preform into a predetermined container shape, the mouth of the preform can be heat-treated to increase the crystallinity. In other words, the mouth of the preform is heat-treated to increase the crystallinity, and then the preform is blow-molded. This improves the heat resistance of the container obtained by blow-molding the preform, and as mentioned above, the crystallinity can be increased efficiently with a smaller amount of heat. [Example]

[0019] The present invention will be described in more detail below with reference to specific examples.

[0020] [Preparation of powder and granular materials] Preforms were injection-molded using commercially available polyester pellets for PET bottles, which were obtained by copolymerizing a chemically synthesized diol component and a dicarboxylic acid component. The resulting preforms were then crushed in a crushing device, and the resulting crushed material, including the resulting powder and granules, was sieved. The crushed material was sieved, in this order, through a first sieve with a mesh size of approximately 2 mm, a second sieve with a mesh size of approximately 1.5 mm, a third sieve with a mesh size of approximately 1.0 mm, and a fourth sieve with a mesh size of approximately 0.5 mm. The powder and granules that passed through the first sieve but not the second sieve were designated Sample 1, the powder and granules that did not pass through the third sieve were designated Sample 2, the powder and granules that did not pass through the fourth sieve were designated Sample 3, and the powder and granules that passed through the fourth sieve were designated Sample 4. These represent the powder and granules generated during the recycling of polyester-based resin molded products. When the particle size of each of Samples 1 to 4 was measured, the average particle size of Sample 1 was 3 mm, the average particle size of Sample 2 was 2 mm, the average particle size of Sample 3 was 1 mm, and the average particle size of Sample 4 was 0.5 mm.

[0021] For the crushed material before sieving and each of Samples 1 to 4, a first differential scanning calorimetry measurement was performed, which included a heating process from 40°C to 290°C at a heating rate of 10°C / min, an isothermal process at 290°C for 3 minutes, and a cooling process from 290°C to 40°C at a heating rate of 300°C / min. A second differential scanning calorimetry measurement was performed, which included a heating process from 40°C to 290°C at a heating rate of 10°C / min. The melting endothermic peak temperature (Tm(1st)) during heating was determined from the DSC curve obtained by the first differential scanning calorimetry, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by the second differential scanning calorimetry. The results are shown in Table 1.

[0022] The IV values ​​of the crushed material before sieving and Samples 1 to 4 were measured by a standard method in accordance with JIS K7390. The IV values ​​were measured by dissolving a polyester resin test piece in a phenol:tetrachloroethane (1:1) solvent to prepare a solution, and then adjusting the temperature to 25°C using a relative viscometer (Viscotec Y501C, manufactured by Malvern Panalytical). The results are shown in Table 1.

[0023] [Table 1]

[0024] From these results, it was confirmed that no significant changes were observed in the physical properties of the crushed product before sieving and Samples 1 to 4.

[0025] [Control example] A preform was produced by injection molding using the polyester pellets for PET bottles described above as the molding material. A test piece was cut out from the produced preform, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by the second differential scanning calorimetry in the same manner as described above. The result was 153°C.

[0026] [Example 1] Sample 4 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.1 wt% to prepare a molding material, and preforms were injection molded. Test specimens were cut from the prepared preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage reduction in Tc1(2nd) compared to the control.

[0027] [Example 2] Sample 4 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.3 wt% to prepare a molding material, and preforms were injection molded. Test specimens were cut from the prepared preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage reduction in Tc1(2nd) compared to the control.

[0028] [Example 3] Sample 4 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.5 wt% to prepare a molding material, and preforms were injection molded. Test specimens were cut from the prepared preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage reduction in Tc1(2nd) compared to the control.

[0029] [Example 4] Sample 3 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.3 wt% to prepare a molding material, and preforms were injection molded. Test specimens were cut from the prepared preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage reduction in Tc1(2nd) compared to the control.

[0030] [Example 5] Sample 3 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.5 wt% to prepare a molding material, and preforms were injection molded. Test specimens were cut from the prepared preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0031] [Example 6] Sample 3 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.7 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0032] [Comparative Example 1] Sample 2 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.3 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0033] Comparative Example 2 Sample 2 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.5 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) of the crushed product.

[0034] Comparative Example 3 Sample 2 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.7 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) of the crushed product.

[0035] Comparative Example 4 Sample 1 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.3 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0036] Comparative Example 5 Sample 1 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.5 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry measurement in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0037] Comparative Example 6 Sample 1 was added to the aforementioned polyester pellets for PET bottles at a ratio of 0.7 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0038] Comparative Example 7 Sample 1 was added to the aforementioned polyester pellets for PET bottles at a ratio of 1.0 wt% to prepare a molding material, and preforms were produced by injection molding. Test specimens were cut from the produced preforms, and the crystallization exothermic peak temperature (Tc1(2nd)) during heating was determined from the DSC curve obtained by a second differential scanning calorimetry in the same manner as described above. The results are shown in Table 2, along with the percentage decrease in Tc1(2nd) compared to the crushed product.

[0039] [Table 2]

[0040] From the above results, no significant changes were observed in the melting endothermic peak temperature (Tm(1st)), crystallization exothermic peak temperature (Tc1(2nd)), or intrinsic viscosity (IV) of Samples 1 to 4. However, by preparing the molding material by adding Sample 3 or Sample 4, which has an average particle size of 1 mm or less, a decrease of 4.6% or more was observed in the crystallization exothermic peak temperature (Tc1(2nd)) of the molded preform when heating. This confirms that when increasing the crystallinity of the mouth of the molded preform, it is possible to increase the crystallinity efficiently with a smaller amount of heat.

[0041] The present invention has been described above by showing preferred embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention.

Claims

1. We collect powder generated during the recycling process of polyester resin molded products, preparing a molding material by adding fine particles having an average particle size of 1 mm or less contained in the recovered powder or granules in a proportion of 0.1% by weight or more to a polyester-based resin as a main raw material; A method for producing a preform, comprising molding a preform using the molding material.

2. The method for producing a preform according to claim 1, wherein the fine particles are added in an amount of 0.3% by weight or more and less than 2.0% by weight.

3. 2. The method for producing a preform according to claim 1, wherein the polyester resin molded article is a PET bottle.

4. A method for producing a polyester-based resin container, comprising heat-treating the mouth of a preform produced by the preform production method according to any one of claims 1 to 3 to increase the crystallinity, and then blow-molding the preform.

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