Manufacturing method for synthetic resin containers

Abstract

To provide a method for manufacturing a synthetic resin container with enhanced liquid repellency without compromising the transparency of the container.SOLUTION: A method for manufacturing a synthetic resin container 100 in which the innermost layer is formed by an adhesive resin by blow molding, includes the steps of: forming a precursor in which the innermost layer is formed by the adhesive resin; blowing blow air into the precursor; and blowing hydrophobic particles into the precursor simultaneously with or before blowing the blow air.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a synthetic resin container. [Background Art]

[0002] Conventionally, development of containers having a liquid-repellent effect achieved by a combination of irregularities on the inner surface of the container and a liquid repellent has been progressing (for example, Patent Document 1). [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2020-117284 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, in the plastic container described in Patent Document 1, since the liquid repellent is applied by a method such as spraying, the liquid repellent exists as aggregates with a particle diameter of approximately 100 µm on the surface of the base material, which may whiten the appearance of the container and impair transparency, and there was room for improvement in this respect.

[0005] An object of the present disclosure is to solve such problems, and to provide a method for manufacturing a synthetic resin container with improved liquid repellency without impairing the transparency of the container. [Means for Solving the Problem]

[0006] In order to solve the above problems, the method for manufacturing a synthetic resin container according to the present disclosure includes: [1] A method for manufacturing a synthetic resin container wherein the innermost layer formed by blow molding is formed of an adhesive resin, the method comprising: forming a precursor in which the innermost layer is formed from said adhesive resin; blowing blow air into the precursor; The steps include blowing hydrophobic fine particles into the precursor at the same time as blowing in the blow air, or before blowing in the blow air, and Includes fruit, The tip of the blow nozzle that blows the hydrophobic fine particles into the precursor is provided with a mesh member that suppresses the aggregation of the hydrophobic fine particles. It is characterized by the following:

[0007] Furthermore, the method for manufacturing a synthetic resin container described herein is: [2] In the configuration described in [1] above, it is preferable that the step of blowing the hydrophobic fine particles into the precursor is performed simultaneously with the start of blowing the blow air.

[0009] Furthermore, the method for manufacturing a synthetic resin container described herein is: [ 3 ] Above [1] or [ 2] In the described configuration, the adhesive resin preferably includes a maleic acid-modified polyolefin resin.

[0010] Furthermore, the method for manufacturing a synthetic resin container described herein is: [ 4 ] From the above [1] [ 3 In the configuration described in any of the above, the hydrophobic fine particles preferably include hydrophobic silica fine particles.

[0011] Furthermore, the method for manufacturing a synthetic resin container described herein is: [ 5 ] the above[ 4 In the configuration described above, it is preferable that the hydrophobic silica nanoparticles include silica nanoparticles having a trimethylsilyl group in their structure.

[0012] Furthermore, the method for manufacturing a synthetic resin container described herein is: [ 6 ] From the above [1] [ 5 In the configuration described in any of the above, the blow molding is preferably extrusion blow molding. [Effects of the Invention]

[0013] According to the present disclosure, it is possible to provide a method for producing a synthetic resin container having improved liquid repellency without impairing the transparency of the container. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [Figure 1] It is a partial cross-sectional view of a synthetic resin container according to an embodiment of the present disclosure. [Figure 2] It is an enlarged cross-sectional view of a portion A in Figure 1. [Figure 3] It is a flow chart showing the implementation procedure of a method for producing a synthetic resin container according to an embodiment of the present disclosure. MODE FOR CARRYING OUT THE INVENTION

[0015] Hereinafter, the present disclosure will be illustrated and described in more detail with reference to the drawings.

[0016] Figure 1 is a partial front cross-sectional view showing the configuration of a synthetic resin container 100 according to an embodiment of the present disclosure. The synthetic resin container 100 has a bottle shape, and includes: a substantially cylindrical body portion 20 that is elastically deformable by pressing and forms an accommodation space S for contents; a cylindrical mouth portion 10 that is connected to the upper end of the body portion 20 via a shoulder portion 30 and internally forms an opening 10a for supplying and discharging contents; and a bottom portion 40 that closes the lower end of the body portion 20. As shown in Figure 1, an external thread portion 10b that allows a cap, pump or the like to be attached by screw engagement is provided on the outer peripheral surface of the mouth portion 10. Note that instead of the external thread portion 10b, a convex or concave engaged portion may be provided, and the cap may be held on the mouth portion 10 by the engagement of the convex or concave engaging portion provided on the cap with the engaged portion. Note that the body portion 20 does not necessarily have to be elastically deformable.

[0017] As shown in a partial cross-section in Figure 2, the synthetic resin container 100 comprises an inner layer 25 that forms a storage space S for containing contents, and an outer layer 21 that covers the inner layer 25 from the radially outer side. In this embodiment, the inner layer 25 is provided inward from the outer layer 21 in a way that prevents it from being peeled off, but the embodiment is not limited to this, and the inner layer 25 may be peelable from the outer layer 21.

[0018] In this specification, claims, and drawings, the side where the mouth 10 is located is considered the upper side (upper side in Figure 1), and the side where the bottom 40 is located is considered the lower side (lower side in Figure 1). Radial outward means the direction away from the central axis O of the synthetic resin container 100 in Figure 1, along a straight line passing through the central axis O and perpendicular to the central axis O, and radial inward means the direction toward the central axis O along the said straight line. Furthermore, in the description of the layer structure of the synthetic resin container 100, the side where the outer layer 21 is located is the outside, and the side where the inner layer 25 is located is the inside (container space S side) (see Figure 2).

[0019] The synthetic resin container 100 is made of synthetic resin and can be formed, for example, by co-extruding a synthetic resin forming the outer layer 21 and a synthetic resin forming the inner layer 25 in a molten state to form a cylindrical laminated parison, and then blow molding (extrusion blow molding) the laminated parison by sandwiching it in a mold. Alternatively, the synthetic resin container 100 can also be formed by biaxial stretch blow molding a preform with a laminated structure that has been formed in advance by injection molding or the like.

[0020] The shoulder portion 30 is connected to the lower end of the mouth portion 10 and expands radially outward toward the downward direction. In this embodiment, the shoulder portion 30 is inclined at a substantially constant angle with respect to the central axis O as shown in Figure 1, and has a flat shape with a straight outline. However, it is not limited to this, and may be dome-shaped, bulging outward toward the outside of the container, or conversely, inverted dome-shaped, concave toward the inside of the container.

[0021] The body portion 20 has its upper end connected to the lower end of the shoulder portion 30, and its lower end connected to the outer edge of the bottom portion 40. The body portion 20 is flexible and can be squeezed, and the contents can be dispensed by squeezing the body portion 20 at approximately the center height. The method of dispensing the contents is not particularly limited; for example, the contents may be dispensed by their own weight by inverting the synthetic resin container 100, or a dispensing cap with a pump mechanism may be attached to the mouth portion 10. Furthermore, the body portion 20 is curved and constricted as a whole, with the central position in the height direction (direction of the central axis O) being concave toward the central axis O. That is, the body portion 20 gradually decreases in diameter downward from the upper end connected to the shoulder portion 30, and gradually increases in diameter from the smallest diameter portion toward the lower end connected to the bottom portion 40.

[0022] In this embodiment, the outer layer 21 is made of low-density polyethylene (LDPE), a thermoplastic resin (manufactured by Sumitomo Chemical Co., Ltd., model number: F236-0), and the inner layer 25 is made of acid-modified polyolefin resin, an adhesive resin (manufactured by Mitsubishi Chemical Corporation, Modic®, model number: M522). Modic: M522 is a maleic acid-modified polyolefin and is a material approved for use as a food container (approving organization: Polyolefin Hygiene Council), and offers excellent safety when containing food. When containing contents other than food, various adhesive resins other than Modic: M522 may be used. By using an adhesive resin for the inner layer 25, hydrophobic silica fine particles, described later, can be embedded and fixed to the inner surface of the inner layer 25, forming irregularities in the hydrophobic silica fine particles to enhance liquid repellency, and effectively suppressing the detachment of the hydrophobic silica fine particles from the inner layer 25.

[0023] In this embodiment, hydrophobic silica microparticles are embedded on the inner surface of the inner layer 25. The hydrophobic silica microparticles embedded in the inner layer 25 are AEROSIL®, model name: R812S, manufactured by Nippon Aerosil Co., Ltd. AEROSIL:R812S is a product surface-modified with trimethylsilyl groups and has higher hydrophobicity. In order to ensure the transparency and liquid repellency of the container, the particle size of the hydrophobic silica microparticles is preferably in the range of approximately 7 nm to 40 nm.

[0024] Alternatively, instead of hydrophobic silica nanoparticles, other hydrophobic nanoparticles such as hydrophobic fluorine nanoparticles may be embedded and immobilized on the inner surface of the inner layer 25.

[0025] In this embodiment, the entire synthetic resin container 100, from the opening 10 to the bottom 40, has a two-layer structure with an outer layer 21 and an inner layer 25, and the inner layer 25 is formed of an adhesive resin, but the embodiment is not limited to this. For example, the body 20 that contains the contents may have a two-layer structure with an outer layer 21 and an inner layer 25 (adhesive resin), while the opening 10 may have only an outer layer 21. Alternatively, the synthetic resin container 100 may not have an outer layer 21 and may be composed of only one resin layer including an adhesive resin. However, it is preferable to provide an additional resin layer outside the adhesive resin, taking into consideration the strength of the container, etc. Furthermore, the synthetic resin container 100 may be composed of three or more resin layers, with the innermost layer being made of adhesive resin.

[0026] Next, the procedure for manufacturing the synthetic resin container 100 according to this embodiment will be explained with reference to Figure 3.

[0027] First, in order to manufacture the synthetic resin container 100 by extrusion blow molding, two layers of heated and molten parison corresponding to the outer layer 21 and inner layer 25 are extruded, cut to a certain length, and then sandwiched in a blow molding die (step S101 in Figure 3). When the synthetic resin container 100 is formed by extrusion blow molding, this molten parison becomes the precursor. If the synthetic resin container 100 is composed of three or more layers or a single layer, the molten parison is also composed of three or more layers or a single layer corresponding to the layer configuration of the container. In either layer configuration, an adhesive resin is used for the innermost layer of the parison.

[0028] On the other hand, when manufacturing a synthetic resin container 100 by, for example, biaxial stretch blow molding of a preform, a two-layer preform corresponding to an outer layer 21 and an inner layer 25 is prepared. The two-layer preform may be formed by, for example, co-injection molding, insert molding, or two-color molding, or two preforms manufactured in separate processes may be combined. When the synthetic resin container 100 is formed by biaxial stretch blow molding, this two-layer preform serves as a precursor.

[0029] Next, blow air is blown into the laminated parison, which is the precursor, from the blow nozzle of the blow molding apparatus, and hydrophobic fine particles are blown in at the same time (step S102 in Figure 3). In this embodiment, the blowing of hydrophobic fine particles is started at the start of blowing air (start of blowing). This is because a higher resin temperature of the precursor makes it easier for the hydrophobic fine particles to adhere to the innermost layer. The blow pressure when blowing in the hydrophobic fine particles is preferably, for example, 0.01 MPa or more and 0.5 MPa or less. Furthermore, the hydrophobic silica fine particles mentioned above are used as the hydrophobic fine particles.

[0030] Alternatively, hydrophobic silica particles may be blown into the laminated parison before blowing in compressed air.

[0031] Furthermore, it is preferable to place a mesh member at the tip of the blow nozzle of the blow molding apparatus and blow hydrophobic silica fine particles through this mesh. By placing the mesh member, it is possible to suppress the blowing of large hydrophobic silica fine particles that have aggregated from the hydrophobic silica fine particles blown into the precursor from the blow nozzle into the laminated parison.

[0032] In this context, "suppressing the aggregation of hydrophobic silica microparticles" means not trapping the aggregates with a mesh, but rather causing the aggregates to collide with the mesh and break them down into smaller particles (approaching the primary particle size). This improves the dispersibility when blowing in hydrophobic silica microparticles, removes larger hydrophobic silica microparticles that have formed aggregates, and allows only hydrophobic silica microparticles with a size roughly equivalent to the primary particle size (7 nm to 40 nm) to be blown into the layered parison.

[0033] After the blowing of hydrophobic silica particles into the molten parison is complete, for example, blow air is blown into the laminated parison while further increasing the blow air pressure (0.4 MPa to 0.8 MPa) to discharge excess hydrophobic silica particles to the outside of the container and complete the extrusion blow molding (step S103 in Figure 3).

[0034] Even when forming a synthetic resin container 100 by biaxial stretch blow molding, for example, the blowing of hydrophobic fine particles is started at the beginning of blowing air into the preform (at the start of blowing), and after the blowing of hydrophobic fine particles is completed, blow air is blown further into the preform to complete the biaxial stretch blow molding.

[0035] As described above, this embodiment is a method for manufacturing a synthetic resin container 100 in which the innermost layer is formed of an adhesive resin by blow molding, and includes the steps of forming a precursor in which the innermost layer is formed of an adhesive resin, blowing blow air into the precursor, and blowing hydrophobic fine particles into the precursor simultaneously with or before blowing blow air. By adopting this configuration, in the manufacturing process of the synthetic resin container 100 by blow molding, when blow air is supplied to the parison (precursor) in a molten state, hydrophobic fine particles can be blown into the parison almost simultaneously with the supply of blow air, thereby embedding and fixing the hydrophobic fine particles in the adhesive resin on the inner surface of the synthetic resin container 100. Therefore, a liquid-repellent container can be manufactured by blow molding alone without providing a separate liquid-repellent layer in a later process. Furthermore, in this embodiment, as in Patent Document 1, the hydrophobic fine particles are fixed to the innermost surface of the container by air pressure without dissolving them in a solvent, so that the hydrophobic fine particles do not easily aggregate. Therefore, the liquid-repellent properties of the container can be improved without impairing the transparency of the container after the hydrophobic fine particles have been fixed to the inner surface of the container.

[0036] Furthermore, in this embodiment, the step of blowing hydrophobic fine particles into the precursor (laminated parison) is configured to be performed simultaneously with the start of blowing in the blown air. By adopting this configuration, the hydrophobic fine particles are blown in while the temperature of the laminated parison is high, making it easier to fix the hydrophobic fine particles to the inner surface of the container.

[0037] Furthermore, in this embodiment, the tip of the blow nozzle that blows hydrophobic fine particles into the precursor is provided with a mesh member that suppresses the aggregation of hydrophobic fine particles. By adopting such a configuration, it is possible to easily maintain the particle size of the hydrophobic silica fine particles blown into the parison to be as small as the particle size of the primary particles.

[0038] Furthermore, in this embodiment, the adhesive resin is configured to include a maleic acid-modified polyolefin resin. By adopting such a configuration, the detachment of hydrophobic fine particles can be reliably prevented.

[0039] Furthermore, in this embodiment, the hydrophobic fine particles are configured to include hydrophobic silica fine particles. By adopting such a configuration, the liquid-repellent properties of the inner surface of the synthetic resin container 100 can be further improved.

[0040] Furthermore, in this embodiment, the hydrophobic silica nanoparticles are configured to include silica nanoparticles having a trimethylsilyl group in their structure. By adopting this configuration, the trimethylsilyl group, which does not have a hydroxyl group in its structure, acts in the direction of hydrophobicity, further enhancing the liquid-repellent properties.

[0041] Furthermore, in this embodiment, blow molding is configured as extrusion blow molding. By adopting this configuration, it is possible to manufacture containers with excellent liquid-repellent properties using only extrusion blow molding equipment, which is excellent for mass production.

[0042] While this disclosure has been described based on various drawings and embodiments, it should be noted that those skilled in the art will find it easy to make various modifications and alterations based on this disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present invention. For example, the functions included in each component can be rearranged in a logically consistent manner, and multiple components can be combined into one or separated. It should be understood that these are also included within the scope of the present invention.

[0043] For example, in this embodiment, the adhesive resin is composed of a maleic acid-modified polyolefin resin, but the embodiment is not limited to this, and may contain other resins in addition to the maleic acid-modified polyolefin resin. Alternatively, an adhesive resin that does not contain a maleic acid-modified polyolefin resin may be used.

[0044] Furthermore, although the hydrophobic fine particles in this embodiment are composed of hydrophobic silica fine particles, the embodiment is not limited to this configuration and may include fine particles other than hydrophobic silica fine particles, such as hydrophobic fluorine fine particles. Alternatively, the hydrophobic fine particles may not include hydrophobic silica fine particles and may consist only of other hydrophobic fine particles such as hydrophobic fluorine fine particles.

[0045] Furthermore, in this embodiment, hydrophobic silica nanoparticles having a trimethylsilyl group in their structure are used, but the embodiment is not limited to this, and hydrophobic silica nanoparticles without a trimethylsilyl group in their structure may also be used. [Explanation of Symbols]

[0046] 10 Mouth 10a opening 10b Male threaded section 10c outside air intake vent 20 Torso 21 Outer layer 25 Inner layer 30 Shoulder 40 bottom 100 synthetic resin containers O center axis S Containment space

Claims

1. A method for manufacturing a synthetic resin container in which the innermost layer is formed with an adhesive resin by blow molding, The steps include forming a precursor in which the innermost layer is formed of the adhesive resin, The steps include blowing air into the precursor, The steps include blowing hydrophobic fine particles into the precursor at the same time as blowing in the blow air, or before blowing in the blow air, and Includes, A method for manufacturing a synthetic resin container, wherein a mesh member is provided at the tip of a blow nozzle that blows the hydrophobic fine particles into the precursor, thereby suppressing the aggregation of the hydrophobic fine particles.

2. The method for manufacturing a synthetic resin container according to claim 1, wherein the step of blowing the hydrophobic fine particles into the precursor is performed simultaneously with the start of blowing the blow air.

3. The method for producing a synthetic resin container according to claim 1 or 2, wherein the adhesive resin includes a maleic acid-modified polyolefin resin.

4. The method for manufacturing a synthetic resin container according to claim 1 or 2, wherein the hydrophobic fine particles include hydrophobic silica fine particles.

5. The method for producing a synthetic resin container according to claim 4, wherein the hydrophobic silica fine particles include silica fine particles having a trimethylsilyl group in their structure.

6. The method for manufacturing a synthetic resin container according to claim 1 or 2, wherein the blow molding is extrusion blow molding.

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