Resin container and manufacturing method thereof

Abstract

A resin container that contains a resin material having a relatively low melt viscosity and yet is capable of being subjected to multi-layer direct blow molding, and a method for producing the same. [Solution] A first molten resin and a second molten resin are discharged from a multi-layer direct blow molding device, and the first molten resin has a lower melt viscosity than the second molten resin. Next, the temperature of the first molten resin is set lower than the temperature of the second molten resin, so that the first molten resin and the second molten resin discharged from the multi-layer direct blow molding device are laminated to form a parison. In this way, the multi-layer resin container 1 is manufactured, which includes an outer layer formed of the hardened first molten resin and an inner layer formed of the hardened second molten resin.

Description

[Technical field]

[0001] The present invention relates to a resin container having a multi-layer structure produced by multi-layer 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 makes it possible to obtain a high-value-added resin container with a multilayer structure including multiple resin layers, such as an outer layer for improving the texture of the appearance and a barrier layer for preventing oxygen penetration.

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

[0004] [Patent Document 1] JP 2006-312485 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, even if there is a resin material that has the desired function to be applied to 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 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 and the like. Thus, for example, a resin container body is produced by direct blow molding polypropylene or the like, and a specific paint is sprayed onto the resin container body, thereby manufacturing a resin container having a matte appearance (coating).

[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 the manufacturing cost. Moreover, the painting step requires a large amount of paint because the paint is sprayed onto the resin container body in a clean room, which causes a problem of a large environmental load. In addition, the painting step is prone to uneven painting, and even if a product is good enough in the blow molding step, it may become a defective product in the painting step, which causes a problem of low product yield.

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

[0009] 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 and an inner layer made of a second resin by using a multilayer direct blow molding device, 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 device to form a multilayer parison; and pressurizing the multilayer parison to blow mold the parison, wherein the MFR value of the first resin is higher than the MFR value 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, which 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, which 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 laminated together.

[0010] The inventors have found that, according to the above method, even if the MFR value of the outer layer is greater than that of the inner layer and is 4 g / 10 min to 6 g / 10 min, and the first molten resin of the outer layer cannot form a parison by itself, the first molten resin can be made to flow down together with the second molten resin by setting the temperatures and pressures of the first and second molten resins discharged from the head of the device as described above, and a multi-layered parison can be appropriately formed. As a result, it becomes possible to directly blow mold a resin container having a multi-layer structure, the outer layer of which contains a first molten resin that cannot form a parison by itself. In addition, a resin material that cannot form a parison by itself can be used for the outer layer, and resin materials having various functions can be applied to the outer layer. Moreover, since the outer layer and the inner layer have a multi-layer direct blow molding structure, a resin container can be obtained that has high solvent resistance and impact resistance compared to a case where the outer layer is a coating film.

[0011] A method for producing a resin container according to the present invention is a method for producing a resin container having a multi-layer 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 multi-layer direct blow molding device, the method including a step 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 multi-layer direct blow molding device to form a multi-layer parison, and a step of pressurizing the multi-layer parison to blow mold the multi-layer parison, the MFR value of the first resin being 4 g / 10 min or more and 6 g / 10 min or less, the IV value of the second resin being 0.7 or more and 1.2 or less, and the MFR value of the third resin being 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, which 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, which 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 laminated together.

[0012] The resin container of the present invention has multiple resin layers including an outer layer made of a first resin and an inner layer made of a second resin, and is a multi-layer direct blow molded resin container, 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 be given 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 has 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, and is a multi-layer direct blow molded resin container, wherein the first resin is a polypropylene resin containing an additive that imparts a matte appearance, 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 the first resin is formed over the entire outer surface of the resin container. Effect of the Invention

[0015] According to the present invention, it is possible to provide a resin container that is capable of being subjected to multi-layer direct blow molding even though it contains a resin material with a relatively high MFR value, and a method for producing the same. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a front view showing the appearance of a resin container in the first embodiment. [Diagram 2] FIG. 2 is an enlarged cross-sectional view showing a vertical section of the side wall portion A in FIG. [Diagram 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. [Diagram 5] FIG. 5 is an explanatory diagram showing a conventional method for manufacturing a resin container including a coating step. [Figure 6] FIG. 6 is a view corresponding to FIG. 2 and 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 PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. 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 the present embodiment 1 is a multi-layered 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, and drug containers, as well as other resin containers. In this specification, the term "multi-layered" 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, a resin container 1 having two resin layers consisting of the outer layer 11 and the inner layer 12 will be described as an example.

[0020] Furthermore, the present invention can also be applied to resin containers having three or more resin layers, and for example, the present invention may have 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] 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 in the figure, the neck portion 6 has a male threaded outer circumferential surface and is adapted to be closed by a cap (not shown) which is a separate part.

[0022] The inner layer 12 of the present embodiment 1 is made of polypropylene resin (PP) and occupies, 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 mixed with an additive that produces a matte appearance. The outer layer 11 occupies, 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] Moreover, 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 makes the entire outer surface of the resin container 1 have 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, whereas 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 it is a single layer, whereas the outer layer 11 has a melt viscosity that is not suitable for direct blow molding when it is a single layer. However, as described later, in this embodiment 1, by molding under predetermined conditions, even when the melt viscosity of the outer layer 11 is not suitable for direct blow molding when it is a single layer, the resin container 1 can be manufactured by multilayer direct blow molding.

[0025] Next, a method for producing a resin container 1 having a multilayer structure including the outer layer 11 and the inner layer 12 using a multilayer direct blow molding device will be described. Here, Fig. 3 is a table showing the production conditions of 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 a 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 produces 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, the polypropylene resin pellets that will become the matte outer layer 11 are heated and melted, and the polypropylene resin pellets that will become the inner layer 12 of the base layer are heated and melted. Furthermore, the molten resins 21, 22 that will become the outer layer 11 and the inner layer 12 are conveyed while being pressurized by a screw, and are discharged after being joined together 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 as a parison in a laminated state. Then, the parison with the multilayer structure is pressurized to manufacture a multilayer resin container 1 including an outer layer 11 formed by the hardened first molten resin 21 and an inner layer 12 formed by the hardened second molten resin 22.

[0031] Here, a resin material with an MFR value of 4 g / 10 min or more and 6 g / 10 min or less has too low a melt viscosity (i.e., too high a fluidity) and is particularly difficult to form a parison in a single layer. However, according to the first embodiment, even when a resin material with such an MFR value is included as the outer layer 11, it is possible to perform multi-layer direct blow molding by setting appropriate conditions such that the temperature of the first molten resin 21 that becomes the outer layer 11 is lower than the temperature of the second molten resin 22 that becomes 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 higher than 220° C., the first molten resin 21 will flow downward relative to the second molten resin 22 (12) as shown by the arrow 21 in Fig. 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, the temperature of first molten resin 21 is set lower than that of second molten resin 22, and in particular, the temperature of first molten resin 21 is set to 180° C. or higher and 220° C. or lower, so that first molten resin 21 can flow down from the discharge port together with second molten resin 22. This is believed to be because the effect of frictional resistance that first molten resin 21 receives from second molten resin 22 becomes large.

[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 where 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 in particular, to set the pressure of first molten resin 21 to 4.0 MPa or more and 9.0 MPa or less, and the pressure of second molten resin 22 to 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 makes it possible to more appropriately form 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 inherently 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 produce 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, a resin container that conventionally required two processes, a blow molding process for the inner layer and a painting process for the outer layer, can be manufactured in one blow molding process, so that the manufacturing cost can be dramatically reduced. Moreover, since the painting process that requires a large amount of paint is not necessary, the resin container 1 can be manufactured while keeping the environmental load low, and there is a remarkable effect that it is possible to eliminate waste such as the production of defective products due to 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 and attached to the neck portion 106. In this state, paint 111 is sprayed to form a coating film 107 on the container body 105. Therefore, the completed resin container 100 cannot have the coating film (outer layer) 107 formed on at least a part of the neck portion 106.

[0038] In contrast, the resin container 1 of the present embodiment 1 is manufactured by multi-layer direct blow molding, so that the matte outer layer 11 can be formed over the entire resin container 1, and a good appearance can be obtained. 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 are 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, the resin container 1 having a multi-layer structure consisting of two layers, the outer layer 11 and the inner layer 12, and the manufacturing method thereof have been described, but the second embodiment relates to a resin container 1 having a three-layer 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 produces a matte appearance, as in the above-mentioned embodiment 1. The outer layer 11 accounts for about 15% of the thickness of the entire resin layer. The adhesive layer 13 accounts for about 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 melt viscosity lower than that of 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 above-mentioned embodiment 1. Therefore, the inner layer 12 can be directly blow molded even by itself, whereas the outer layer 11 has a melt viscosity that is not suitable for direct blow molding by itself. Next, a method for producing the resin container 1 having a multi-layer structure including the outer layer 11, the inner layer 12 and the adhesive layer 13 using a multi-layer direct blow molding apparatus 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 produces 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] Next, the resin pellets that will become the outer layer 11, the inner layer 12, or the adhesive layer 13 are heated and melted, and each is conveyed while being pressurized, and the flows are 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 constituting second molten resin (PET) 22. The temperature setting of first molten resin 21 is the same as in the above-mentioned embodiment 1, for example, 180 degrees or more and 220 degrees or less (preferably, 185 degrees or more and 195 degrees or less). On the other hand, the temperature of second molten resin (PET) 22 is, for example, 195 degrees or more and 210 degrees or less. The temperature of third molten resin 23 which becomes adhesive layer 13 is also, for example, 195 degrees or more and 210 degrees or less.

[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. Meanwhile, the pressure of second molten resin (PET) 22 is, for example, 18 MPa or more and 28 MPa or less. Moreover, the pressure of the 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 parison with the multilayer structure is pressurized to produce a multilayer resin container 1 including an outer layer 11 formed by the hardened first molten resin 21, an inner layer 12 formed by the hardened second molten resin (PET) 22, and an adhesive layer 13 formed by the hardened third molten resin 23.

[0050] In the present embodiment 2, similarly to the above embodiment 1, a resin container 1 including an outer layer 11 having a low melt viscosity and high fluidity can be formed by multi-layer direct blow molding. That is, the inner layer 12 (and adhesive layer 13), which is a layer inside the outer layer 11, can be blow molded by itself, and the temperature of the first molten resin 21 which becomes the outer layer 11 is set to a lower temperature than the temperature of the second molten resin (PET) 22 which becomes the inner layer 12, and appropriate conditions are set. The third molten resin 23 which becomes the adhesive layer 13 is also set to the same temperature conditions as the second molten resin 22. It is considered that this increases the influence of frictional resistance that the first molten resin 21 receives from the second molten resin (PET) 22 and the third molten resin 23 which flow down together from the discharge port, and thus a parison of these three layers can be formed.

[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 together with second molten resin (PET) 22 and third molten resin 23 in a moldable state, and makes it possible to more appropriately form a laminated parison. Therefore, the second embodiment can also provide the same effects as the first embodiment.

[0052] In addition, the resin container 1 manufactured in the first and second embodiments can use a resin material having a lower melt viscosity than the inner layer 12 for the outer layer 11, thereby allowing resin materials having various functions to be applied to the outer layer 11. Moreover, since the outer layer 11 and the inner layer 12 have a multilayer direct blow molded structure, the resin container can have higher solvent resistance and strength than when the outer layer 11 is a coating film.

[0053] Here, an example of the present invention will be described. The following experiments were performed 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. Note that the surfaces of the resin containers of the example and comparative example are 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 Example were immersed in ethanol and acetone, respectively, and after a certain time, they were taken out and observed visually and with a confocal microscope. Figures 8 and 9 are microscope images showing the surfaces of the Example and Comparative Example 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, it was confirmed that many fine cracks had occurred in the Comparative Example (see Figure 9). Next, when the sample was immersed in acetone, whitening of the surface was visually confirmed in the comparative example, whereas no whitening was observed in the example. Therefore, from these results, it was confirmed that the resin container 1 according to the embodiment has higher solvent resistance than the comparative example. Example 2

[0056] In Example 1, a comparative experiment on surface strength was carried out. 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 with a confocal microscope, no cracks were found near the indentation on the surface of the Example (see FIG. 10). On the other hand, a relatively large crack (see FIG. 11) and numerous fine cracks (see FIG. 12) were found near the indentation on the surface of the Comparative Example. In particular, numerous fine cracks are relatively easy to grow, 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 embodiment 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 producing a resin container having a multi-layer structure including an outer layer made of a first resin and an inner layer made of a second resin by a multi-layer direct blow molding device, comprising: A step 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 laminated state from a head of the multilayer direct blow molding device to form a multilayer parison; and compressing the multi-layer parison to blow mold it. 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; 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, which is 180°C or higher and 220°C or lower, 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, which is 4 MPa or higher and 9 MPa or lower, thereby forming the multi-layer parison in which the first molten resin and the second molten resin are stacked on top of each other.

2. A method for producing a resin container having a multi-layer 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 multi-layer direct blow molding device, comprising: a step 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 layered state from a head of the multilayer direct blow molding device to form a multilayer parison; and compressing the multi-layer parison to blow mold it. The MFR value of the first resin is 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; The third resin has an MFR value of 0.7 g / 10 min or more and 2.6 g / 10 min or less, 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, which is 180°C or higher and 220°C or lower, 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, which is 4 MPa or higher and 9 MPa or lower, thereby forming the multi-layer parison in which the first molten resin, the second molten resin and the third molten resin are layered on top of each other.

3. A resin container having multiple resin layers including an outer layer made of a first resin and an inner layer made of a second resin, the resin container being multi-layer direct blow molded, The first resin is a polypropylene resin containing 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; A resin container, wherein the first resin is formed over the entire outer surface of the resin container.

4. A 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, the resin container being multi-layer direct blow molded, The first resin is a polypropylene resin containing an additive that gives the resin a matte appearance, The MFR value of the first resin is 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; The third resin has an MFR value of 0.7 g / 10 min or more and 2.6 g / 10 min or less, A resin container, wherein the first resin is formed over the entire outer surface of the resin container.

Images