Resin container and method for manufacturing the same

Abstract

To provide a resin container which enables multilayer direct blow molding while containing a resin material having comparatively low melt viscosity, and a method for manufacturing the same.SOLUTION: As for a first molten resin and a second molten resin discharged from a multilayer direct blow molding device, melt viscosity of the first molten resin is made to be lower than that of the second molten resin. Then, the first molten resin and the second molten resin discharged from the multilayer direct blow molding device are laminated to form a parison by setting the temperature of the first molten resin lower than the temperature of the second molten resin. Thus, a resin container 1 including multilayers including an outer layer formed by curing the first molten resin, and an inner layer formed by curing the second molten resin is manufactured.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a resin container having a multilayer structure obtained by multilayer direct blow molding, and a method for producing the same. [Background technology]

[0002] Resin containers molded from synthetic resin materials are widely used, for example, as cosmetic containers and food containers. This type of resin container can be manufactured by multilayer direct blow molding. This allows for the production of high-value-added resin containers with a multilayer structure that includes multiple resin layers, such as an outer layer to enhance the appearance and a barrier layer to prevent oxygen penetration.

[0003] For example, Patent Document 1 describes a multilayered resin container made by direct blow molding a thermoplastic synthetic resin, in which all layers of the multilayered resin container are made of polyethylene terephthalate resin that can be directly blow molded, and the outermost transparent polyethylene terephthalate resin layer is made of a resin containing a luster pigment. This multilayered structure allows the container to have a glossy appearance and properties. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-312485 Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if there is a resin material with the desired functionality for the outer layer, if its MFR value is too low (for example, a resin material for injection molding), it is usually not possible to form a parison from the resin material, and therefore the resin material cannot be used for multilayer direct blow molding.

[0006] In response to this, it is also known that a desired appearance can be obtained by applying a coating to the surface of a blow-molded resin container body. For example, there is a need for a matte appearance with reduced gloss in cosmetic containers, etc. Therefore, for example, a resin container body can be produced by direct blow molding polypropylene or the like, and then a predetermined paint can be sprayed onto the resin container body, thereby producing a resin container with a matte appearance (coating film).

[0007] However, the conventional method of forming the outer layer by painting requires two steps: a blow molding step and a painting step, which inevitably increases manufacturing costs. Furthermore, the painting step involves spraying paint onto the resin container body in a clean room, which requires a large amount of paint and poses a significant environmental burden. Furthermore, the painting step is prone to uneven coating, which can lead to defective products even if they are good in the blow molding step, resulting in poor product yields.

[0008] The present invention has been made in consideration of these points, and its main object is to provide a resin container and a manufacturing method thereof that can be subjected to multilayer direct blow molding, even though it includes an outer layer made of a resin material with a relatively high MFR value. [Means for solving the problem]

[0009] The method for manufacturing a resin container according to the present invention is a method for manufacturing a resin container having a multilayer structure including an outer layer made of a first resin and an inner layer made of a second resin using a multilayer direct blow molding machine, and includes the steps of: discharging a first molten resin, which is the first resin in a molten state, and a second molten resin, which is the second resin in a molten state, in a layered state from a head of the multilayer direct blow molding machine to form a multilayer parison; and pressurizing the multilayer parison to blow-mold the parison, wherein the MFR of the first resin is higher than that of the second resin and is 4 g / 10 min or more and 6 g / 10 min or less. In the parison formation step, the temperature of the first molten resin discharged from the head is set to a temperature lower than the temperature of the second molten resin discharged from the head, that is 180°C or more and 220°C or less, and the pressure of the first molten resin discharged from the head is set to a pressure lower than the pressure of the second molten resin discharged from the head, that is 4 MPa or more and 9 MPa or less, thereby forming the multilayer parison in which the first molten resin and the second molten resin are layered together.

[0010] The inventors have discovered that, according to the above method, even if the MFR of the outer layer is greater than that of the inner layer and is between 4 g / 10 min and 6 g / 10 min, and the first molten resin of the outer layer cannot form a parison by itself, by setting the temperatures and pressures of the first and second molten resins discharged from the head of the device as described above, the first molten resin can be caused to flow down together with the second molten resin, thereby properly forming a multilayered parison.As a result, it is possible to directly blow mold a multilayered resin container whose outer layer contains a first molten resin that cannot form a parison by itself. In addition, resin materials that cannot be used alone to form a parison can be used for the outer layer, and resin materials with various functions can be applied to the outer layer. Moreover, since the outer and inner layers have a multilayer direct blow-molded structure, the resin container can have higher solvent resistance and impact resistance than when the outer layer is a coating.

[0011] The method for producing a resin container according to the present invention is a method for producing a resin container having a multilayer structure including an outer layer made of a first resin, an inner layer made of a second resin, and an adhesive layer made of a third resin interposed between the outer layer and the inner layer, by using a multilayer direct blow molding device, the method comprising the steps of: discharging a first molten resin, which is the first resin in a molten state, a second molten resin, which is the second resin in a molten state, and a third molten resin, which is the third resin in a molten state, in a laminated state from a head of the multilayer direct blow molding device to form a multilayer parison; and pressurizing the multilayer parison to blow mold the multilayer parison, wherein the MFR value of the first resin is 4 g / 10 min or more and 6 g / 10 min or less, the IV value of the second resin is 0.7 or more and 1.2 or less, and the MFR value of the third resin is 0.7 g / 10 min or more and 2.6 g / 10 min or less, and in the parison forming process, the temperature of the first molten resin discharged from the head is set to a temperature lower than the temperature of the second molten resin discharged from the head, that is, 180°C or more and 220°C or less, and the pressure of the first molten resin discharged from the head is set to a pressure lower than the pressure of the second molten resin discharged from the head, that is, 4 MPa or more and 9 MPa or less, thereby forming the multi-layer parison in which the first molten resin, the second molten resin, and the third molten resin are layered one on top of another.

[0012] The resin container according to the present invention is a multi-layer direct blow-molded resin container having multiple resin layers including an outer layer made of a first resin and an inner layer made of a second resin, wherein the first resin is a polypropylene resin blended with an additive that gives the resin a matte appearance, the MFR value of the first resin is greater than the MFR value of the second resin and is 4 g / 10 min or more and 6 g / 10 min or less, and the first resin is formed over the entire outer surface of the resin container.

[0013] According to the above configuration, a resin material that cannot form a parison by itself can be used for the outer layer, and the entire outer surface of the resin container can have a matte appearance, while still providing a resin container with high solvent resistance and high impact resistance.

[0014] The resin container according to the present invention is a multi-layer direct blow-molded resin container having multiple resin layers including an outer layer made of a first resin, an inner layer made of a second resin, and an adhesive layer made of a third resin interposed between the outer layer and the inner layer, wherein the first resin is a polypropylene resin blended with an additive that imparts a matte appearance, the first resin has an MFR value of 4 g / 10 min or more and 6 g / 10 min or less, the second resin has an IV value of 0.7 or more and 1.2 or less, and the third resin has an MFR value of 0.7 g / 10 min or more and 2.6 g / 10 min or less, and the first resin is formed over the entire outer surface of the resin container. [Effects of the Invention]

[0015] According to the present invention, it is possible to provide a resin container that can be subjected to multilayer direct blow molding even when it contains a resin material with a relatively large MFR value, and a method for producing the same. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a front view showing the appearance of a resin container according to the first embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing a vertical cross section of the side wall portion A in FIG. [Figure 3] FIG. 3 is a table showing the manufacturing conditions of the resin container in the first embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing a parison of a reference example. [Figure 5] FIG. 5 is an explanatory diagram showing a conventional method for manufacturing a resin container including a painting step. [Figure 6] FIG. 6 is a view equivalent to FIG. 2, showing a vertical cross section of a resin container in the second embodiment. [Figure 7] FIG. 7 is a table showing the manufacturing conditions of the resin container in the second embodiment. [Figure 8] FIG. 8 is a microscope image showing the surface of the example after immersion in ethanol. [Figure 9] FIG. 9 is a microscope image showing the surface of the comparative example after immersion in ethanol. [Figure 10] FIG. 10 is a microscope image showing the vicinity of the indentation on the surface of the example. [Figure 11] FIG. 11 is a microscope image showing the vicinity of the indentation on the surface of the comparative example. [Figure 12] FIG. 12 is a microscope image showing the vicinity of the indentation on the surface of the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments. First Embodiment Fig. 1 is a front view showing the appearance of a resin container 1 in the present embodiment 1. Fig. 2 is an enlarged cross-sectional view showing a vertical cross section of a side wall portion A in Fig. 1.

[0018] The resin container 1 in this embodiment 1 is a multilayer direct blow molded resin container 1, and is suitable for use as, for example, a cosmetic container. The resin container 1 is not limited to cosmetic containers, and can be widely used as, for example, beverage containers, food containers, medicine containers, and other resin containers. In this specification, "multilayer" refers to two or more layers.

[0019] 2, the resin container 1 has multiple resin layers including an outer layer 11 and an inner layer 12. In the present embodiment 1, as an example, a resin container 1 having two resin layers consisting of the outer layer 11 and the inner layer 12 will be described.

[0020] Furthermore, the present invention can also be applied to resin containers having three or more resin layers, for example, a three-layer structure in which an adhesive layer is interposed between the outer layer 11 and the inner layer 12 in this embodiment 1.

[0021] As shown in Fig. 1, the resin container 1 has a hollow container body 5 and a cylindrical neck portion 6 that is integrally formed and continues from the upper part of the container body 5. Although not shown, the neck portion 6 has a male-threaded outer circumferential surface, and is closed by a cap (not shown), which is a separate part.

[0022] The inner layer 12 of the first embodiment is made of polypropylene resin (PP) and accounts for, for example, 80% to 85% of the thickness of the entire resin layer. Therefore, the inner layer 12 serves as a base layer of the resin container 1, which has a relatively large thickness. The inner layer 12 may contain a pigment that exhibits a desired color. On the other hand, the resin material constituting the outer layer 11 is a polypropylene resin blended with an additive that imparts a matte appearance. The outer layer 11 accounts for, for example, 15% to 20% of the thickness of the entire resin layer. Thus, the thickness of the outer layer 11 is thinner than the thickness of the inner layer 12.

[0023] The outer layer 11 is formed over the entire outer surface of the resin container 1 from the container body 5 to the neck portion 6. This gives the entire outer surface of the resin container 1 a matte finish.

[0024] The resin material constituting the outer layer 11 has a lower melt viscosity than the resin material constituting the inner layer 12. As shown in FIG. 3 , the MFR (melt mass flow rate) value of the inner layer 12 is 0.75 g / 10 min or more, while the MFR value of the outer layer 11 is 4 g / 10 min or more and 6 g / 10 min or less. Therefore, the inner layer 12 can be directly blow molded even when used alone, while the outer layer 11 has a melt viscosity that is not suitable for direct blow molding when used alone. However, as will be described later, in this embodiment 1, by molding under specified conditions, a resin container 1 can be produced by multilayer direct blow molding even when the melt viscosity of the outer layer 11 when used alone is not suitable for direct blow molding.

[0025] Next, a method for producing a resin container 1 having a multilayer structure including the outer layer 11 and inner layer 12 using a multilayer direct blow molding device will be described. Here, Fig. 3 is a table showing the production conditions for the resin container 1 in the present embodiment 1. Fig. 4 is an explanatory diagram showing a parison of a reference example.

[0026] When manufacturing a resin container 1 having a two-layer structure consisting of an outer layer 11 and an inner layer 12, first, for the first molten resin 21 and the second molten resin 22 discharged from the multilayer direct blow molding device, the first molten resin 21 is selected to have a lower melt viscosity than the second molten resin 22. Here, the first molten resin 21 is a polypropylene resin blended with an additive that imparts a matte finish to form the outer layer 11, and as described above, has an MFR value of 4 g / 10 min or more and 6 g / 10 min or less. On the other hand, the second molten resin 22 is a polypropylene resin that forms the inner layer 12, and has an MFR (melt flow rate) value of 0.75 g / 10 min or more.

[0027] Next, pellets of polypropylene resin that will become the matte outer layer 11 are heated and melted, and pellets of polypropylene resin that will become the inner layer 12 of the base layer are heated and melted. Furthermore, the molten resins 21 and 22 that will become the outer layer 11 and the inner layer 12 are conveyed while being pressurized by screws, and are then merged and discharged in a laminated state at the head of the device.

[0028] At this time, the temperature of first molten resin 21 is set lower than the temperature of second molten resin 22. The temperature of first molten resin 21 is set, for example, to be 180°C or higher and 220°C or lower. As shown in the table of Fig. 3, it is more preferable that the temperature of first molten resin 21 is set to be 185°C or higher and 195°C or lower. On the other hand, the temperature of second molten resin 22 is set to be, for example, 195°C or higher and 210°C or lower.

[0029] Furthermore, the pressure of first molten resin 21 is set lower than the pressure of second molten resin 22. For example, as shown in the table of Fig. 3, the pressure of first molten resin 21 is set to, for example, 4.0 MPa or more and 9.0 MPa or less. On the other hand, the pressure of second molten resin 22 is set to, for example, 20 MPa or more and 35 MPa or less.

[0030] As a result, the first molten resin 21 and the second molten resin 22 discharged from the multilayer direct blow molding device are formed into a parison in a laminated state. Then, the multilayer parison is pressurized to produce a multilayer resin container 1 including an outer layer 11 formed by hardening the first molten resin 21 and an inner layer 12 formed by hardening the second molten resin 22.

[0031] Resin materials with an MFR value of 4 g / 10 min or more and 6 g / 10 min or less have too low a melt viscosity (i.e., too high a fluidity) and are therefore particularly difficult to form into a single-layer parison. However, according to the first embodiment, even when a resin material with such an MFR value is used as the outer layer 11, multilayer direct blow molding is possible by appropriately setting the temperature of the first molten resin 21 that forms the outer layer 11 lower than the temperature of the second molten resin 22 that forms the inner layer 12.

[0032] For example, if the temperature of the first molten resin 21 is higher than the temperature of the second molten resin 22 and is greater than 220°C, the first molten resin 21 will flow downward relative to the second molten resin 22 (12), as shown by arrow 21 in Figure 4. Therefore, the first molten resin 21 and the second molten resin 22 will not be in a laminated state, and a parison with a multi-layer structure cannot be formed.

[0033] In contrast, according to the first embodiment, even if the melt viscosity of first molten resin 21 is lower than that of second molten resin 22 and first molten resin 21 cannot form a parison by itself, by setting the temperature of first molten resin 21 lower than that of second molten resin 22, and in particular, by setting the temperature of first molten resin 21 to be 180°C or higher and 220°C or lower, it becomes possible to cause first molten resin 21 to flow down from the discharge port together with second molten resin 22. This is thought to be because the effect of frictional resistance that first molten resin 21 receives from second molten resin 22 becomes greater.

[0034] Furthermore, if the pressure of first molten resin 21 is lower than 4.0 MPa, it is difficult to form a parison in a state in which first molten resin 21 is laminated on second molten resin 22. Therefore, it is preferable to set the pressure of first molten resin 21 lower than the pressure of second molten resin 22, and particularly to set the pressure of first molten resin 21 to be 4.0 MPa or more and 9.0 MPa or less, and the pressure of second molten resin 22 to be 20 MPa or more and 35 MPa or less. This allows first molten resin 21 to flow down stably together with second molten resin 22 in a moldable state, and more appropriately forms a laminated parison.

[0035] Therefore, according to this embodiment 1, even if the outer layer 11 is made of a resin material that has a relatively low melt viscosity and is originally unsuitable for direct blow molding, such as a polypropylene resin containing an additive that produces a matte finish, it is possible to perform multilayer direct blow molding to create a resin container 1 in which the outer layer 11 and the inner layer 12 have a laminated structure.

[0036] Furthermore, according to the present embodiment 1, resin containers that conventionally required two processes, a blow molding process for the inner layer and a painting process for the outer layer, can now be manufactured in a single blow molding process, thereby dramatically reducing manufacturing costs. Moreover, because the painting process, which requires a large amount of paint, is not necessary, the resin container 1 can be manufactured while minimizing the environmental impact, and there are significant effects such as eliminating waste, such as defective products resulting from uneven painting, even when there is no problem with the blow molding itself.

[0037] 5 is an explanatory diagram showing a conventional method for manufacturing a resin container including a coating process. In the conventional coating process, a blow-molded container body 105 is turned upside down, and a jig 110 is fitted onto the neck portion 106. In this state, paint 111 is sprayed onto the container body 105 to form a coating film 107. Therefore, the completed resin container 100 cannot have a coating film (outer layer) 107 formed on at least a portion of its neck portion 106.

[0038] In contrast, the resin container 1 of the first embodiment is manufactured by multilayer direct blow molding, so that the matte outer layer 11 can be formed over the entire resin container 1, resulting in a good appearance. Second Embodiment

[0039] Next, a second embodiment of the present invention will be described. In the following embodiments, the same parts as those in the first embodiment will be given the same reference numerals, and detailed description thereof will be omitted. Here, Fig. 6 is a view equivalent to Fig. 2 showing a vertical cross section of the resin container 1 in the second embodiment. Fig. 7 is a table showing the manufacturing conditions of the resin container 1 in the second embodiment.

[0040] In the above-mentioned first embodiment, a resin container 1 having a multi-layer structure consisting of two layers, an outer layer 11 and an inner layer 12, and a method for manufacturing the same were described, but the second embodiment relates to a resin container 1 having a three-layer resin structure.

[0041] 6, the resin container 1 has an outer layer 11, an inner layer 12, and an adhesive layer 13 provided between the outer layer 11 and the inner layer 12. The adhesive layer 13 bonds the outer layer 11 and the inner layer 12 so that they do not peel off from each other.

[0042] The inner layer 12 of the second embodiment is made of polyethylene terephthalate (PET) and accounts for, for example, about 80% of the thickness of the entire resin layer, serving as the base layer of the resin container 1. The inner layer 12 may be transparent or may contain a pigment that exhibits a desired color.

[0043] The resin material constituting the outer layer 11 is a polypropylene resin blended with an additive that imparts a matte appearance, as in the first embodiment. The outer layer 11 accounts for approximately 15% of the thickness of the entire resin layer. The adhesive layer 13 accounts for approximately 5% of the thickness of the entire resin layer. Thus, the thickness of the outer layer 11 is thinner than the thickness of the inner layer 12 and thinner than the thickness of the layers inside the outer layer 11 (i.e., the adhesive layer 13 and the inner layer 12).

[0044] The resin material constituting the outer layer 11 has a lower melt viscosity than the resin material constituting the inner layer 12. As shown in Fig. 7, the IV value of the inner layer 12 (PET) is 0.7 or more and 1.2 or less, and the MFR value of the outer layer 11 is 4 g / 10 min or more and 6 g / 10 min or less, the same as in the first embodiment. Therefore, the inner layer 12 can be directly blow molded even when used alone, whereas the outer layer 11 has a melt viscosity that is not suitable for direct blow molding when used alone. Next, a method for producing the resin container 1 having a multilayer structure including the outer layer 11, the inner layer 12, and the adhesive layer 13 using a multilayer direct blow molding device will be described.

[0045] As in the first embodiment, the first molten resin 21 is selected to have a melt viscosity lower than that of the second molten resin (PET) 22. The first molten resin 21 is a polypropylene resin containing an additive that imparts a matte finish and serves as the outer layer 11, as in the first embodiment. The MFR value of the adhesive layer 13 is 0.7 g / 10 min or more and 2.6 g / 10 min or less, as shown in the table of FIG.

[0046] Subsequently, resin pellets that will become the outer layer 11, inner layer 12, or adhesive layer 13 are heated and melted, and are conveyed while being pressurized, and are then merged in a laminated state at the head of the device and discharged.

[0047] At this time, the temperature of first molten resin 21 is set lower than the temperature of second molten resin (PET) 22 that constitutes it. The temperature setting of first molten resin 21 is the same as in the first embodiment, for example, 180°C or higher and 220°C or lower (preferably 185°C or higher and 195°C or lower). On the other hand, the temperature of second molten resin (PET) 22 is set, for example, 195°C or higher and 210°C or lower. The temperature of third molten resin 23 that becomes adhesive layer 13 is also set, for example, 195°C or higher and 210°C or lower.

[0048] Furthermore, the pressure of first molten resin 21 is set lower than the pressure of second molten resin (PET) 22. For example, as shown in the table of FIG. 7, the pressure of first molten resin 21 is the same as in the first embodiment, for example, 4.0 MPa or more and 9.0 MPa or less. On the other hand, the pressure of second molten resin (PET) 22 is, for example, 18 MPa or more and 28 MPa or less. Furthermore, the pressure of third molten resin that becomes adhesive layer 13 is, for example, 10 MPa or more and 20 MPa or less.

[0049] As a result, the first to third molten resins discharged from the multilayer direct blow molding device are formed into a parison in a laminated state. Then, the multilayer parison is pressurized to produce a multilayer resin container 1 including an outer layer 11 formed by hardening the first molten resin 21, an inner layer 12 formed by hardening the second molten resin (PET) 22, and an adhesive layer 13 formed by hardening the third molten resin 23.

[0050] As in the first embodiment, the second embodiment also allows for multilayer direct blow molding of a resin container 1 including an outer layer 11 with low melt viscosity and high fluidity. That is, the inner layer 12 (and adhesive layer 13), which is a layer inside the outer layer 11, can itself be blow molded, and appropriate conditions are set by setting the temperature of the first molten resin 21 that will become the outer layer 11 lower than the temperature of the second molten resin (PET) 22 that will become the inner layer 12. The third molten resin 23 that will become the adhesive layer 13 is also set to the same temperature conditions as the second molten resin 22. This increases the effect of frictional resistance that the first molten resin 21 experiences from the second molten resin (PET) 22 and the third molten resin 23 that flow down together from the discharge port, making it possible to form a parison of these three layers.

[0051] Furthermore, the pressure of first molten resin 21 is set to be lower than the pressure of second molten resin (PET) 22, and in particular, the pressure of first molten resin 21 is set to be 4.0 MPa or more and 9.0 MPa or less, and the pressure of second molten resin (PET) 22 is set to be 18 MPa or more and 28 MPa or less. The pressure of third molten resin 23 is also set to be 10 MPa or more and 20 MPa or less, so that the pressure of first molten resin 21 is lower. This allows first molten resin 21 to flow down stably in a moldable state together with second molten resin (PET) 22 and third molten resin 23, and more appropriately forms a laminated parison. Therefore, the second embodiment can also achieve the same effects as the first embodiment.

[0052] Furthermore, in the resin container 1 manufactured in the first and second embodiments, by using a resin material having a lower melt viscosity than the inner layer 12 for the outer layer 11, it is possible to apply resin materials having various functions to the outer layer 11. Moreover, since the outer layer 11 and the inner layer 12 have a multilayer direct blow-molded structure, it is possible to obtain a resin container with higher solvent resistance and strength than when the outer layer 11 is a coating film.

[0053] Here, examples of the present invention will be described. The following experiments were conducted on an example of a resin container in which a matte outer layer 11 was formed by multilayer direct blow molding, and a comparative example of a resin container having an outer layer made of a coating film. Here, the example is a resin container having an inner layer 12 made of PET, an adhesive layer 13, and an outer layer 11 made of matte PP. The comparative example is a resin container having an inner layer made of PET and an outer layer made of a matte coating film. The surfaces of the resin containers of the example and comparative example were each printed for decoration. Example 1

[0054] In Example 1, a comparative experiment of solvent resistance was conducted. The resin containers of the Example and Comparative Examples were immersed in ethanol and acetone, respectively, and then removed after a certain period of time and observed visually and with a confocal microscope. Figures 8 and 9 are microscopic images showing the surfaces of the Example and Comparative Examples after immersion in ethanol, respectively.

[0055] When immersed in ethanol, no noticeable difference was observed visually between the two. Furthermore, when observed with a confocal microscope, no cracks were found on the surface of the Example (see Figure 8). On the other hand, the Comparative Example was found to have many fine cracks (see Figure 9). Next, when the sample was immersed in acetone, whitening of the surface was visually confirmed in the comparative example, while no whitening was observed in the example. Therefore, from these results, it was confirmed that the resin container 1 according to the example had higher solvent resistance than the comparative example. Example 2

[0056] In Example 1, a comparative experiment on surface strength was conducted. A point load of 60 kgf was applied to the surfaces of the resin containers of the Example and Comparative Example using a Rockwell testing machine, and the results were observed. Figure 10 is a microscope image showing the vicinity of the indentation on the surface of the Example. Figures 11 and 12 are microscope images showing the vicinity of the indentation on the surface of the Comparative Example.

[0057] As a result of observation using a confocal microscope, no cracks were observed near the indentation on the surface of the Example (see Figure 10). On the other hand, relatively large cracks (see Figure 11) and numerous fine cracks (see Figure 12) were confirmed near the indentation on the surface of the Comparative Example. In particular, numerous fine cracks are relatively easy to propagate, and are thought to lead to a decrease in impact resistance. Therefore, from these results, it was confirmed that the resin container 1 according to the example had a higher surface strength than the comparative example. [Industrial Applicability]

[0058] INDUSTRIAL APPLICABILITY As described above, the present invention is useful for a resin container having a multilayer structure obtained by multilayer direct blow molding, and a method for producing the same. [Explanation of symbols]

[0059] 1 resin container 11 Outer layer 12 Inner layer 13 Adhesive layer 21 First molten resin 22 Second molten resin 23 Third molten resin

Claims

1. A method for manufacturing a resin container using a multi-layer direct blow molding device, comprising: Regarding the first molten resin and the second molten resin discharged from the multilayer direct blow molding device, the first molten resin has a melt viscosity lower than that of the second molten resin, a parison is formed by laminating the first molten resin and the second molten resin discharged from the multilayer direct blow molding device in a laminated state by setting the temperature of the first molten resin lower than the temperature of the second molten resin; A method for manufacturing a resin container, which manufactures a multi-layer resin container including an outer layer formed by hardening the first molten resin and an inner layer formed by hardening the second molten resin.

2. The method for manufacturing a resin container according to claim 1 , wherein the pressure of the first molten resin is lower than the pressure of the second molten resin.

3. The method for manufacturing a resin container according to claim 1, wherein the resin material constituting the outer layer has an MFR value of 4 g / 10 min or more and 6 g / 10 min or less.

4. The method for manufacturing a resin container according to claim 1 , wherein the temperature of the first molten resin is 180° C. or higher and 220° C. or lower.

5. A resin container having multiple resin layers including an outer layer and an inner layer, which is multilayer direct blow molded, the resin material constituting the outer layer has a melt viscosity lower than that of the resin material constituting the inner layer, A resin container, wherein the outer layer is formed over the entire outer surface of the resin container.

6. The resin container according to claim 5 , wherein the resin material constituting the outer layer is a polypropylene resin containing an additive that gives the outer layer a matte appearance.

7. 6. The resin container according to claim 5, wherein the resin material constituting the outer layer has an MFR value of 4 g / 10 min or more and 6 g / 10 min or less.

Images