Living hinge member

Abstract

Provided is a living hinge member 10 comprising: a member 11 including a living hinge part 12; and an elastomer 13 disposed on the surface of an outdoor exposure side of the living hinge part 12.

Description

Living hinge material

[0001] The present disclosure relates to living hinge members.

[0002] There are living hinges that can be bent by thinning a portion of a component. Living hinges can be made by injecting molten resin into the gap in a mold, for example, to mold a container and lid into an integrated shape, allowing them to be bent. This method of manufacturing resin is called injection molding. Living hinges generally use relatively flexible polymer materials such as polypropylene and polyethylene. A properly designed living hinge is expected to withstand unlimited bending cycles (Non-Patent Document 1).

[0003] There are various injection molding techniques, one of which is called two-color molding. Two-color molding is a molding method that combines resins with different properties or colors (Non-Patent Documents 2-4). Research is also being conducted on a two-color molding technique that combines a hard material and an elastomer to produce a hinged opening and closing cap (Non-Patent Document 5).

[0004] Hidetoshi Yokoi, "Improvement of Hinge Characteristics by In-Mold Push-In Hinge Molding," Production Research, Vol. 42, No. 6, 1990, pp. 97-100. Yamashita Electric, "A Lively Partner in Molding Processing You Want to Know, See, and Visit: The Pioneer of Two-Color Molding," Molding Processing, 14, 07, 2002, pp. 454-455. Sanko Light Industry, "What is Sanko Light Industry's Two-Color Molding? Everything about Two-Color Molding," [online], Internet: <https: / / www.slkco.jp / tech / double / opinion / knowledge> Kanamori Sangyo, "What is Pla Quick Two-Color Molding (Double Mold)?" [online], Internet: <https: / / www.plaquick.com / information / 5623> Sanko Light Industry, "Advantages and Disadvantages of Two-Color Molding," [online], Internet: <https: / / www.slkco.jp / tech / double / opinion / compare / demerit> Kaori Negishi, "Microscopic Analysis of Degraded Living Hinges of Polypropylene Aerial Cable Closure," Zairyo-to-Kankyo, Vol. 72, No. 3, 2023, pp. 76-84. Aronkasei Co., Ltd., "Technical Data," [online], Internet: https: / / www.aronkasei.co.jp / new_aronkasei / html / elastomer / technology /

[0005] Living hinges are generally used indoors and are rarely exposed to harsh outdoor environments. However, there are cases where living hinges are used outdoors, and in such cases, cracks and breakage have been reported (Non-Patent Document 6). In particular, living hinges used outdoors are thought to deteriorate due to the interaction of bending and ultraviolet degradation.

[0006] Focusing on examples of deterioration of living hinges, it is believed that the outdoor-exposed surface is primarily deteriorated by ultraviolet rays, causing molecular chains to break and reducing strength. In addition, repeated opening and closing of the hinge makes the exposed surface, which has become particularly deteriorated and brittle, unable to withstand compressive stress, leading to cracks and fractures from the outdoor-exposed surface. In other words, if ultraviolet degradation of the outdoor-exposed surface of a living hinge can be prevented, it is believed that the durability of the living hinge can be improved.

[0007] One possible solution to this problem is to improve the weather resistance of the living hinge itself. However, the polypropylene commonly used in living hinges is a resin that is weak against ultraviolet rays. Polypropylene used outdoors is kneaded with ultraviolet inhibitors and antioxidants to improve durability, but the effect is limited.

[0008] It is also possible to replace only the hinge portion of the living hinge with another resin that is highly weather-resistant, but in that case, the boundary between the resin in the hinge portion and the resin in the areas other than the hinge portion will be weak.

[0009] The present disclosure has been made in consideration of the above circumstances, and aims to improve the durability of living hinge members used outdoors.

[0010] A living hinge member according to one aspect of the present disclosure comprises a member having a living hinge portion and an elastomer disposed on a surface of the living hinge portion that is exposed to the outdoors.

[0011] According to the present disclosure, it is possible to improve the durability of a living hinge member used outdoors.

[0012] FIG. 1A is an overall view of a living hinge member in a normal state. FIG. 1B is an overall view of a living hinge member when bent. FIG. 2A is a side view of a living hinge member showing an example of an elastomer arrangement. FIG. 2B is a side view of a living hinge member showing an example of an elastomer arrangement. FIG. 3A is a side view of a living hinge member of a comparative example. FIG. 3B is a side view of the destroyed living hinge member of FIG. 3A. FIG. 4A is a side view of a living hinge member of the present embodiment. FIG. 4B is a side view of the living hinge member of FIG. 4A with the destroyed elastomer. FIG. 5A is a side view of a living hinge member in which the member and the elastomer have uneven portions. FIG. 5B is a side view of a living hinge member in which the member and the elastomer have uneven portions. FIG. 6 is a side view of a living hinge member when bent. FIG. 7 is a side view of a living hinge member in which an elastomer is adhered to a hinge portion and bent. Figure 8A is a side view of a living hinge member in which the elastomer is bonded only to the periphery of the hinge portion. Figure 8B is a side view of a living hinge member in which a gap is provided between the elastomer and the living hinge. Figure 9 is a side view of a living hinge member in which the elastomer is bent without being bonded to the hinge portion. Figure 10 is a table showing the characteristics of elastomer materials.

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0014] An example of a living hinge member according to the present embodiment will be described with reference to Figures 1A and 1B. Figure 1A is an overall view of the living hinge member 10 in a normal state, and Figure 1B is an overall view of the living hinge member 10 when folded (in a folded state).

[0015] The living hinge member 10 includes a member 11 having a living hinge portion 12, and an elastomer 13 disposed on the surface of the living hinge portion 12 that is exposed to weather. The elastomer 13 may be disposed on the surface of the member 11 that is exposed to weather, including the periphery of the living hinge portion 12, or on the entire surface of the member 11 that is exposed to weather.

[0016] The member 11 has a structure that allows it to be bent (or opened and closed) by making the thickness of the living hinge portion 12 (hereinafter referred to as "hinge portion 12") thinner than other portions. In the illustrated example, the living hinge member 10 can be bent along the hinge portion 12. The width and thickness of the hinge portion 12 are designed appropriately depending on the application.

[0017] Note that, although the illustrated member 11 is a plate-shaped member, it is not limited to this. For example, the component on the left (or right) side of the hinge portion 12 may be a container, and the component on the right (or left) side of the hinge portion 12 may be a lid. In this case, the lid of the container can be closed by bending the hinge portion 12, and the lid of the container can be opened by extending the hinge portion 12. In this way, the member 11 has a structure that folds and connects two components, such as a container and a lid, at the hinge portion 12, which is the thinner part.

[0018] A material having flexibility enough to be bent is used for the member 11. For the member 11, a polymer material (resin) such as polyethylene or polypropylene can be used.

[0019] Elastomer 13 is a general term for polymeric materials that have viscoelasticity and small intermolecular interactions, and therefore have a small Young's modulus and large fracture strain compared to other materials, and there are several types of elastomers. In this embodiment, it is preferable to select an elastomer that has weather resistance that can withstand outdoor use and flexibility that does not crack even when bent by repeatedly opening and closing.

[0020] In the living hinge member 10 of this embodiment, an elastomer 13 is disposed (coated) on at least the surface of the outdoor-exposed side of the hinge portion 12. The hinge portion 12 is a location where stress is concentrated when the living hinge member 10 is bent.

[0021] The living hinge member 10 of this embodiment may be integrally molded by two-color molding. Two-color molding is a molding method that combines resins with different properties. Two-color molding is also called double molding because it combines two different resins in a single process or cycle. The molding machine has two nozzles and cylinders, and resins are injected and filled into the mold from each nozzle and cylinder in sequence to produce a single molded product.

[0022] 2A and 2B are side views showing an example of a living hinge member 10 in a normal state. The living hinge member 10 of this embodiment has an elastomer 13 on the outdoor-exposed side surface 14 of the member 11. As shown in FIG. 2A , the elastomer 13 may be disposed only in the hinge portion 12 of the outdoor-exposed side surface 14 of the member 11. Alternatively, as shown in FIG. 2B , the elastomer 13 may be disposed not only in the hinge portion 12 but also over a wide area of ​​the outdoor-exposed side surface 14 of the member 11, including the hinge portion 12. Alternatively, the elastomer 13 may be disposed over the entire outdoor-exposed side surface 14 of the member 11, including the area surrounding the living hinge portion 12 of the member 11.

[0023] 3A is a side view of a comparative example of a living hinge member manufactured by a typical two-color molding method. In the illustrated living hinge member, hinge portion 12A is formed from a resin different from the resin of other portion 11A. In this case, the joint between the different resins becomes a weak point. Therefore, there is a concern that the living hinge member may break at the joint due to ultraviolet light and repeated opening and closing, as shown in FIG. 3B.

[0024] FIG. 4A is a side view showing an example of a living hinge member 10 manufactured by two-color molding according to this embodiment. The structure of the living hinge member 10 of this embodiment also has a weak point at the joint between the different resins of the member 11 and the elastomer 13. However, the elastomer 13 prevents ultraviolet light from reaching the joint. Therefore, compared to FIGS. 3A and 3B , destruction at the joint is less likely to occur. Even if the elastomer 13 were to break as shown in FIG. 4B , the resin (e.g., polypropylene) forming the member 11 underneath would not break immediately. Therefore, the durability of the resin of the member 11 underneath the elastomer 13 allows it to withstand the damage for a while. During that time, appropriate operation, such as replacing the living hinge member 10, can be performed.

[0025] 4A and 4B, as shown in FIGS. 3A and 3B, only the hinge portion 12 of the member 11 may be formed with a two-tone resin different from the resin of the other portions, and elastomer 13 may be disposed on the outdoor-exposed side of the hinge portion 12 of this member 11. It is desirable that elastomer 13 be disposed not only in the hinge portion 12 but also in its surrounding area so as to cover the joints between the hinge portion 12 and the other portions of the member 11 made of different resin. This prevents ultraviolet rays from reaching the joints of the resin within the member 11, thereby improving the durability of the living hinge member 10.

[0026] 5A and 5B are side views showing an example of a living hinge member 10 in which a member 11 and an elastomer 13 are mechanically coupled together. In the example shown, a first surface of member 11 facing elastomer 13 and a second surface of elastomer 13 facing member 11 have recesses or concave portions such that the first surface and the second surface interlock with each other.

[0027] Fig. 5A shows an example in which a convex portion is provided on the member 11 and a concave portion is provided on the elastomer 13. Fig. 5B shows an example in which a concave portion is provided on the member 11 and a convex portion is provided on the elastomer 13. As a result, the member 11 and the elastomer 13 are engaged with each other, and are bonded and tightly attached to each other.

[0028] Two-color molding combines two types of materials, so the compatibility and adhesion between the materials must be taken into consideration. Molding incompatible materials together can easily cause peeling. In two-color molding, adhesion is good between amorphous resins, but when combining crystalline resins or a crystalline resin and an amorphous resin, adhesion is poor and peeling is likely to occur.

[0029] Crystalline resins (e.g., polypropylene) commonly used as the material for member 11 are relatively difficult to adhere to other materials. Therefore, it is desirable to provide anchor shapes such as concave and convex portions on member 11 and elastomer 13 to increase the contact area and mechanically bond them to enhance adhesion. Note that the shape of elastomer 13 is not limited to the shape shown in the figure, and any shape such as hooks, grooves, or undercuts may be used as long as it prevents elastomer 13 from peeling off member 11.

[0030] 6 is a side view of the living hinge member 10 of this embodiment when bent. The illustrated living hinge member 10 shows a state in which the member 11 and the elastomer 13 are in close contact with each other, and the elastomer 13 does not peel off from the member 11 even when the hinge portion 12 is bent nearly 180 degrees.

[0031] However, if the thickness of the hinge portion 12 itself is thick, or if the thickness of the hinge portion 12 is increased by placing the elastomer 13 in the hinge portion 12, the compressive stress generated on the inside (outdoor-exposed side 14) of the hinge portion 12 and the tensile stress generated on the outside (surface 15 not exposed to ultraviolet rays) will become large when the hinge portion 12 is bent, and there is a risk of damage such as cracks occurring, particularly in areas where the tensile stress is concentrated.

[0032] Specifically, as shown in Figure 7, when the hinge portion 12 is bent while the elastomer 13 is adhered to the outdoor-exposed side surface 14, the hinge portion 12 becomes thicker by the thickness of the elastomer 13, and excessive tensile stress is applied to the outside.

[0033] 8A , the elastomer 13 may be disposed on the surface of the member 11 exposed to the outdoors, including the periphery of the hinge portion 12, and only the elastomer 13 disposed on the periphery may be adhered or fused to the member 11. That is, the elastomer 13 in the portion excluding the hinge portion 12 may be adhered or fused to the member 11. Specifically, the elastomer 13 is fused only to both sides (periphery) of the hinge portion 12, and is not adhered or fused to the hinge portion 12. However, the elastomer 13 and the hinge portion 12 may be in contact with each other. In two-color molding, when the member 11 and the elastomer 13 are fused or bonded, a spacer or the like may be provided between the hinge portion 12 of the member 11 and the elastomer 13 to prevent the hinge portion 12 from fusing to the elastomer 13.

[0034] 8B , the elastomer 13 may be disposed on the surface of the member 11 exposed to the outdoors, including the periphery of the hinge portion 12, and only the elastomer 13 disposed in the periphery may be adhered or fused to the member 11, with a gap being formed between the member 11 and the elastomer 13 disposed in the hinge portion 12. That is, the elastomer 13 in the portion excluding the hinge portion 12 may be adhered or fused to the member 11, with a gap being formed between the elastomer 13 and the member 11. In two-color molding, when the member 11 and the elastomer 13 are fused or bonded together, a gap (space) can be formed between the hinge portion 12 and the elastomer 13 by providing a thick spacer or the like between the hinge portion 12 of the member 11 and the elastomer 13.

[0035] In this way, by not bonding or fusing the elastomer 13 on the outdoor-exposed side 14 of the hinge portion 12, or by leaving a gap between the elastomer 13 and the hinge portion 12, it is possible to create a structure in which excessive tensile stress is not generated on the outside even when the hinge portion 12 is bent, as shown in Figure 9.

[0036] 8A and 8B show an example in which the elastomer 13 is placed in an area including the periphery of the hinge portion 12, and only the periphery is adhered or fused; however, if the elastomer 13 is placed over the entire surface of the outdoor-exposed side 14 of the member 11, the elastomer 13 in the portion excluding the hinge portion 12 may be adhered or fused to the member 11.

[0037] FIG. 10 is a table showing the characteristics of several elastomers (elastomer materials) used when selecting a preferred elastomer 13. First, it is necessary to select a grade that has good adhesion to the resin (living hinge resin) of the component 11 of the living hinge member 10. Then, select an elastomer that has durability sufficient for outdoor use. It is also advisable to select the elastomer that is most suitable for the living hinge member 10, taking into account factors such as price.

[0038] Regarding the adhesion shown in FIG. 10 , for example, a dumbbell-shaped test piece may be fabricated by two-color molding using the following procedure. Specifically, a base dumbbell test piece (JIS No. 2) made of the resin of the member 11 is cut in half, the cut base dumbbell test piece is placed in an injection molding mold, and the elastomer 13 is injected into the mold and adhered to the base dumbbell test piece to create a dumbbell test piece. A tensile test is then performed on this dumbbell test piece. The adhesion between the member 11 and the elastomer 13 used in the test piece was evaluated according to the tensile strength. For example, if the tensile strength was 15 MPa or greater, the adhesion was evaluated as "Good," if it was less than 15 MPa but not less than 5 MPa, the adhesion was evaluated as "Average," and if it was less than 5 MPa, the adhesion was evaluated as "Poor." In this embodiment, an elastomer 13 with a tensile strength of 5 MPa or greater is considered to be the elastomer that fuses with the member 11. Note that the criteria for adhesion can be determined depending on the application and are not limited to the evaluation method described above.

[0039] Weather resistance may be evaluated using, for example, a weather resistance tester. For example, the weather resistance test is performed in accordance with "JIS K 5600-7-7" and "JIS K 7350-2," and is set, for example, as follows: black panel temperature 63°C, chamber temperature 38°C, humidity 50% RH, water spray time 18 minutes in 2 hours, ultraviolet radiation intensity 60 W / m at wavelengths of 300 nm to 400 nm. ２ .

[0040] Under these conditions, an accelerated aging test was conducted on the test specimens. Dumbbell-shaped test specimens were prepared for each of the multiple elastomers to be tested. The weather resistance of each elastomer 13 was evaluated using the ratio of the initial elongation retention rate to the elongation retention rate after the 2000-hour test. For example, if the elongation retention rate after the 2000-hour test was 75% or more compared to the initial elongation retention rate, the weather resistance was evaluated as "Good." If the elongation retention rate was between 75% and 50% or more, the weather resistance was evaluated as "Good." If the elongation retention rate was less than 50%, the weather resistance was evaluated as "Poor." Note that the weather resistance criteria can be determined depending on the application and are not limited to the above evaluation method.

[0041] Here, an example of selecting an appropriate elastomer for the polypropylene member 11 will be described. Styrene-based elastomers are examples of elastomers that are compatible with polypropylene. For example, Aronkasei's Allostomers (TF series and T series), Elastomer AR (AR-800 series, AR-1000 series, AR-2000 series, AR-SC series, AR-DM series, AR-NK series, AR-GB-75NY), and Arbus (VP ​​series) are suitable candidates (Non-Patent Document 7).

[0042] Of these, Allostomer (TF-A60NT-B1) and Elastomer AR (AR-BOIX-60B), which have relatively high weather resistance, are preferable for outdoor use. In addition, we narrowed down the materials based on factors such as price.

[0043] The thickness of a typical elastomer is about 1 to 2 mm, but as mentioned above, making the area corresponding to the hinge portion 12 of the living hinge member 10 thicker can lead to breakage. For this reason, it is preferable to make the elastomer thinner than usual, about 400 μm to 600 μm. Alternatively, as shown in Figures 8A and 8B, it is preferable to bond or fuse the elastomer 13 in the area excluding the hinge portion 12 to the member 11, thereby preventing excessive tensile stress from being applied.

[0044] Furthermore, a prototype may be manufactured before actual operation and tested to see if it can withstand operation, and then an appropriate elastomer material and dimensions such as the thickness of the elastomer material may be finally determined.

[0045] The living hinge member 10 of this embodiment described above comprises a member 11 having a hinge portion 12, and an elastomer 13 disposed on the surface of the hinge portion 12 on the outdoor exposure side.

[0046] As described above, in the living hinge member 10 of this embodiment, the elastomer 13 can prevent ultraviolet rays from reaching the outdoor-exposed surface of the hinge portion 12, thereby improving the durability of the living hinge member 10 used outdoors. In other words, by preventing ultraviolet rays from reaching the resin of the hinge portion 12, damage to the hinge portion 12 due to ultraviolet degradation can be avoided, and the lifespan of the living hinge member 10 can be extended.

[0047] In this embodiment, the first surface of the member 11 facing the elastomer 13 and the second surface of the elastomer 13 facing the member 11 may have a recess or recesses so that they can mesh with each other. This increases the contact area between the member 11 and the elastomer 13, and improves the adhesion between the member 11 and the elastomer 13.

[0048] Furthermore, in this embodiment, the elastomer 13 in the portion excluding the hinge portion 12 may be adhered or fused to the member 11. Also, a gap may be formed between the elastomer 13 arranged in the hinge portion 12 and the member 11. This makes it possible to achieve a structure in which stress concentration in the hinge portion 12 is less likely to occur when the hinge portion 12 is bent. Specifically, it is possible to reduce the risk of breakage caused by the increase in compressive stress generated on the inside (outdoor-exposed side) of the hinge portion 12 and the increase in tensile stress generated on the outside of the hinge portion 12.

[0049] In addition, the living hinge member 10 of this embodiment is formed by integrally molding the member 11 and the elastomer 13 using two-color molding, which prevents ultraviolet rays from hitting the hinge portion 12 and makes it relatively difficult for the elastomer 13 to peel off from the member 11.

[0050] The present disclosure is not limited to the above-described embodiments, and various modifications and combinations are possible within the technical concept of the present disclosure.

[0051] 10: Living hinge member 11: Member 12: Hinge portion 13: Elastomer 14: Outdoor-exposed side 15: Side not exposed to ultraviolet rays

Claims

1. A living hinge member comprising: a member having a living hinge portion; and an elastomer disposed on a surface of the living hinge portion that is exposed to the outdoors.

2. The living hinge member according to claim 1, wherein the member and the elastomer are mechanically bonded.

3. A living hinge member according to claim 2, wherein the first surface of the member facing the elastomer and the second surface of the elastomer facing the member have a recess or indentations so that the first surface and the second surface engage with each other.

4. A living hinge member according to claim 1, wherein the elastomer is disposed on the surface of the member that is exposed to the elements, including the periphery of the living hinge portion, or on the entire surface of the member that is exposed to the elements.

5. A living hinge member according to claim 4, wherein the elastomer in the portion excluding the living hinge portion is bonded or fused to the member.

6. The living hinge member according to claim 5, wherein there is a gap between the elastomer disposed in the living hinge portion and the member.

7. The living hinge member of claim 1, wherein said elastomer is fused to said member.

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