Helmet

Abstract

To realize a helmet equipped with a novel impact absorbing liner.SOLUTION: A helmet (10) includes a shell (1) which is a molded body of a thermoplastic resin or a thermosetting resin, and an impact absorbing liner (20) disposed inside the shell (1), in which the impact absorbing liner (20) includes a foam layer (21) formed from a polycarbonate-based resin foam.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a helmet. [Background technology]

[0002] A helmet comprises a shell (outer skin) and an impact-absorbing liner (core material) disposed inside the shell (outer skin). Conventionally, impact-absorbing liners have been made of polystyrene-based resin foams, polyolefin-based resin foams such as polypropylene-based resin foams, and the like. Polystyrene-based resin foams have poor recovery properties after compression and release upon impact, and suffer from shrinkage and deformation at temperatures above 70°C. On the other hand, polypropylene-based resin foams have good energy absorption properties upon impact at room temperature, but suffer from significant temperature-dependent changes in energy absorption performance and a significant decrease in compressive strength at high temperatures, making them inadequate as impact absorbing materials.

[0003] For example, Patent Document 1 discloses a technology that uses an acrylonitrile-styrene copolymer resin foam as an impact absorbing liner. The acrylonitrile-styrene copolymer resin foam is a material that has heat resistance and excellent recovery properties after compression and release upon impact, and can improve the above-mentioned problems. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-80515 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is a demand for the development of a helmet equipped with a new impact absorbing liner that differs from the above-mentioned conventional technology.

[0006] One aspect of the present invention aims to provide a helmet with a novel impact absorbing liner. [Means for solving the problem]

[0007] In order to solve the above problems, one aspect of the present invention is as follows.

[0008] [1] A helmet comprising a shell that is a molded body of a thermoplastic resin or a thermosetting resin, and an impact absorbing liner disposed inside the shell, the impact absorbing liner comprising a foam layer formed from a polycarbonate-based resin foam.

[0009] [2] The helmet of [1], wherein the foam layer has a value obtained by dividing the absolute value of the difference between the 10% compressive strength at -30°C and the 10% compressive strength at 80°C by the 10% compressive strength at 23°C of 0.6 or less.

[0010] [3] The helmet of [1] or [2], wherein the impact absorbing liner is a single-layer structure consisting of the foam layer.

[0011] [4] The helmet of [1] or [2], wherein the impact absorbing liner is a multilayer structure having at least two layers: a high foam layer formed from a polycarbonate-based resin foam with a high foaming ratio, and a low foam layer formed from a polycarbonate-based resin foam with a low foaming ratio, the high foam layer constituting the inner surface of the impact absorbing liner, and the low foam layer constituting the outer surface of the impact absorbing liner.

[0012] [5] The helmet of [1] or [2], wherein the impact absorbing liner comprises a high foam layer formed from a polycarbonate-based resin foam with a high foaming ratio and a low foam layer formed from a polycarbonate-based resin foam with a low foaming ratio, and in the impact absorbing liner, the low foam layer is arranged in areas corresponding to the forehead and occipital region, and the high foam layer is arranged in areas corresponding to the parietal region and temporal region.

[0013] [6] The helmet according to [4] or [5], wherein the high foam layer has an expansion ratio of 10 times or more, and the low foam layer has an expansion ratio of less than 10 times.

[0014] [7] The helmet according to any one of [1] to [6], wherein the thermal conductivity of the impact absorbing liner is 0.040 W / m·K or less.

[0015] [8] The helmet according to any one of [1] to [7], wherein the shell is made of a polycarbonate resin. [Effects of the Invention]

[0016] According to one aspect of the present invention, a helmet can be realized in which a new material is used for the impact absorbing liner. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing a schematic configuration of a helmet according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged cross-sectional view showing the schematic configuration of an impact absorbing liner provided in the helmet according to the first embodiment of the present invention. [Figure 3] FIG. 10 is an enlarged cross-sectional view showing the schematic configuration of an impact absorbing liner provided in a helmet according to a second embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a schematic configuration of a helmet according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to these, and various modifications are possible within the scope of the description. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments and examples are also included in the technical scope of the present invention. In this specification, unless otherwise specified, "A to B" representing a numerical range means "A or more (including A and greater than A) and B or less (including B and less than B)."

[0019] [Embodiment 1] FIG. 1 is a cross-sectional view showing the schematic configuration of a helmet 10 according to this embodiment. Note that FIG. 1 shows a helmet 10 worn when driving a motorcycle. However, the helmet 10 according to this embodiment is not limited to the configuration shown in FIG. 1, and can also be applied to helmets worn when driving a four-wheeled vehicle and helmets worn during sports. In addition, in helmet 10, the side of the housing that houses the user's head is referred to as the "inside" and the opposite side is referred to as the "outside."

[0020] The helmet 10 according to this embodiment includes a shell 1 and an impact absorbing liner 20. The shell 1 is a molded body made of thermoplastic resin or thermosetting resin, and forms the outer surface of the main body of the helmet 10. The impact absorbing liner 20 is disposed inside the shell 1. More specifically, the impact absorbing liner 20 is fitted from the shell 1 to cover the entire inner surface of the shell 1.

[0021] Fig. 2 is an enlarged cross-sectional view showing a schematic configuration of the impact absorbing liner 20. As shown in Fig. 2, the impact absorbing liner 20 includes a foam layer 21 formed from a polycarbonate-based resin foam. More specifically, the impact absorbing liner 20 is a single-layer structure made of the foam layer 21.

[0022] As described above, the helmet 10 according to this embodiment uses a new material, polycarbonate-based resin foam, for the impact absorbing liner 20.

[0023] 1 is merely a schematic diagram of the helmet 10 to clarify the thickness and area ratios of the shell 1 and the impact absorbing liner 20. It goes without saying that the various dimensions of the helmet 10 can be set appropriately according to the characteristics and requirements of the market.

[0024] The shell 1 and the impact absorbing liner 20 will be described in more detail below.

[0025] (Shell 1; outer skin) In the helmet 10, the shell (outer skin) 1 is made of a thermoplastic or thermosetting resin, preferably a flexible, semi-flexible, or rigid material. Examples of materials for the shell 1 include polymeric resin materials such as polycarbonate resin, polyvinyl chloride resin, and acrylonitrile butadiene styrene (ABS) resin.

[0026] The shell 1 may also be made of a fiber-reinforced material containing the above-mentioned polymer resin material and a fiber material. This allows the thickness of the shell 1 to be reduced and impact resistance to be improved. By fiber-reinforcing the resin constituting the shell 1 with a fiber material containing glass fiber, carbon fiber, or aramid fiber, the shell can be made even thinner and impact resistance can be improved.

[0027] The shell 1 is a molded body and can be obtained by a processing method such as molding, thermoforming, or injection molding.

[0028] In a preferred embodiment, the shell 1 is made of a polycarbonate resin. Preferably, the shell 1 is a molded article obtained by molding, thermoforming, or injection molding a polycarbonate resin. As a result, in the helmet 10, both the shell 1 and the impact absorbing liner 20 are made of polycarbonate resin. By making the shell 1 and the impact absorbing liner 20 from the same material in this way, the helmet 10 has excellent material recyclability.

[0029] (Impact absorbing liner 20; core material) As described above, the impact absorbing liner 20 includes the foam layer 21 formed from a polycarbonate-based resin foam. The polycarbonate-based resin foam that makes up the foam layer 21 is heat-resistant, can suppress contraction and expansion at high temperatures, is tougher than conventional polystyrene-based resin foam, and exhibits less degradation in impact absorption performance at high temperatures than polyolefin-based resin foam. Therefore, according to the helmet 10 of this embodiment, the impact absorbing liner 20 (1) has excellent impact absorption performance, (2) is difficult to break, and (3) can exhibit stable, high impact absorption performance over a wide temperature range compared to conventional polystyrene-based resin foam or polyolefin-based resin foam.

[0030] Preferably, the foam layer 21 is formed from a polycarbonate-based resin foam molded body (hereinafter referred to as a PC foam molded body). The PC foam molded body can be produced by molding polycarbonate resin foam beads (hereinafter referred to as a PC foam beads) in a mold, or the like.

[0031] The polycarbonate resin has a polyester structure of carbonic acid and glycol or dihydric phenol, and is particularly preferably one containing an aromatic group. Examples of polycarbonate resins containing an aromatic group include aromatic polycarbonates derived from bisphenols, such as 2,2-bis(4-oxyphenyl)propane, 2,2-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)cyclohexane, 1,1-bis(4-oxyphenyl)butane, 1,1-bis(4-oxyphenyl)isobutane, and 1,1-bis(4-oxyphenyl)ethane. These polycarbonate resins are preferred because of their excellent heat resistance.

[0032] Furthermore, foam layer 21 may be formed from a resin foam containing a polycarbonate resin and other resins, without departing from the object and effect of the present invention. Examples of other resins include polypropylene resin, acrylic resin, saturated polyester resin, acrylonitrile butadiene styrene (ABS) resin, polystyrene resin, and polyphenylene oxide resin.

[0033] PC foam particles are obtained by impregnating polycarbonate resin particles containing a polycarbonate resin with a blowing agent and then foaming them. The blowing agent used to obtain PC foam particles can be a volatile blowing agent and / or an inorganic blowing agent. Specific examples of volatile blowing agents include aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons, aliphatic alcohols, aliphatic ketones, and halogenated hydrocarbons. Aliphatic hydrocarbons include propane, n-butane, i-butane, n-pentane, i-pentane, and hexane. Alicyclic hydrocarbons include cyclobutane, cyclopentane, and cyclohexane. Aromatic hydrocarbons include benzene, toluene, and xylene. Aliphatic alcohols include methanol, ethanol, and propanol. Aliphatic ketones include acetone and methyl ethyl ketone. Halogenated hydrocarbons include 1-chloro-1,1-difluoroethane, pentafluoroethane, 1,1,1,2-tetrafluoroethane, and 1,1-difluoroethane. Examples of inorganic foaming agents include inorganic gases such as carbon dioxide (CO2), nitrogen (N2), and air. In this embodiment, the foaming agents listed above can be used alone or in combination. For example, different types of foaming agents, such as an inorganic foaming agent and a volatile foaming agent, can also be used in combination. The amount of foaming agent used is appropriately determined depending on the type of foaming agent and the desired expansion ratio. When determining the amount of foaming agent used depending on the desired expansion ratio, the expansion ratio determines the density of the PC foam molded product, so the amount of foaming agent used is determined primarily by the desired density of the PC foam molded product.

[0034] In this embodiment, the polycarbonate-based resin particles used to obtain the PC foamed beads may contain, in addition to the polycarbonate-based resin, additives such as an antioxidant, a weather resistance improver, an antistatic agent, a colorant, a flame retardancy improver, and a conductivity improver, as necessary.

[0035] These additives may be conventionally known additives that can be used in the production of PC foamed beads. There are no limitations on the colorants used as additives. While PC foamed beads can be natural in color without the addition of colorants, they can also be colored to a desired color by adding colorants such as blue, red, or black to impart design features or to make stains that accumulate over time less noticeable.

[0036] In this embodiment, the PC foam molded article is produced by molding PC foam beads using a conventionally known method. In this embodiment, a preferred method for molding the PC foam molded article involves filling a mold with PC foam beads and further expanding them by steam heating to fuse the beads together to form the PC foam molded article. That is, the PC foam molded article is preferably produced by in-mold molding of PC foam beads. The reasons for this are: (1) it is relatively easy to produce even complex shapes, and (2) the PC foam molded article has excellent density uniformity, making it easy to obtain relatively uniform mechanical properties. As a result, when comparing foam molded articles of the same density, it is easier to achieve high compressive strength and high energy absorption performance using methods other than in-mold molding.

[0037] In the helmet 10 according to this embodiment, the expansion ratio of the PC foam molding that forms the foam layer 21 is 3 times or more (density: 400 kg / m 3 or less), preferably 4 times or more (density: 300 kg / m 3 The expansion ratio of the PC foam molding was calculated by submerging the density of the PC foam molding in water and subtracting the density of the polycarbonate resin (1,200 kg / m 3) by the calculated value (expansion ratio of PC foam molded product = density of polycarbonate resin / density of PC foam molded product).

[0038] The expansion ratio of the PC foam molding is less than 3 times (density: 400 kg / m 3 In addition, the upper limit of the expansion ratio of PC foam moldings is 50 times or less (density: 24.0 kg / m or less) in terms of the closed cell ratio and physical properties. 3 or more).

[0039] In the helmet 10, it is preferable that the foam layer 21 of the impact absorbing liner 20 has a value obtained by dividing the absolute value of the difference between the 10% compressive strength at -30°C and the 10% compressive strength at 80°C by the 10% compressive strength at 23°C (hereinafter sometimes referred to as the 10% compressive strength change rate) of 0.6 or less.

[0040] The 10% compressive strength change rate will be specifically described. First, the compressive strength of the PC foam molded article forming the foam layer 21 at 10% compression (10% compressive strength) at −30° C. was measured. (-30) The compressive strength at 10% compression at 80°C is C (80) The compressive strength at 10% compression at 23°C is C (23) The above 10% compressive strength change rate is C (-30) and C (80) The absolute value of the difference between (23) This is the value obtained by dividing by , and corresponds to the left side of the following formula (1). As shown in the following formula (1), the 10% compressive strength change rate is preferably 0.6 (60%) or less. More preferably, the 10% compressive strength change rate is 0.5 (50%) or less. Furthermore, the smaller the 10% compressive strength change rate, the better, but it is preferably 0.1 or more, and more preferably 0.2 or more. |C (-30) -C (80) | / C (23) ≦0.6 … (1) When the 10% compressive strength change rate is 0.6 or less, the 10% compressive strength of the foam layer 21 is less likely to change between low and high temperatures, and the 10% compressive strength at room temperature is relatively high. Therefore, the impact absorbing liner 20 exhibits little change in 10% compressive strength over a wide range from low to high temperatures (for example, a range of -30°C to 80°C), maintaining a stable shape, and exhibiting relatively high energy absorption performance. Here, when the 10% compressive strength at room temperature is high, the impact absorbing liner 20 absorbs energy with a small amount of displacement in response to impact force, making it difficult for the impact force to be transmitted to the head, thereby exhibiting relatively high energy absorption performance. On the other hand, when the 10% compressive strength at room temperature is low, the impact absorbing liner 20 absorbs energy with a large amount of displacement in response to impact force, making it easier for the impact force to be transmitted to the head, resulting in low energy absorption performance.

[0041] On the other hand, when the 10% compressive strength change rate exceeds 0.6, the superiority of the impact absorbing liner over the conventional polypropylene resin foam tends to decrease in terms of the temperature dependency of compressive strength.

[0042] In addition, the 10% compressive strength C at -30°C (-30) The 10% compressive strength C at 80°C is preferably 0.15 MPa to 6.0 MPa, and more preferably 0.20 MPa to 5.0 MPa. (80) The 10% compressive strength C at 23°C is preferably 0.08 MPa to 3.5 MPa, and more preferably 0.10 MPa to 3.0 MPa. (23) The 10% compressive strength C at -30°C is preferably 0.10 MPa to 4.2 MPa, and more preferably 0.16 MPa to 4.0 MPa. (-30) , 10% compressive strength at 80℃ C (80) , and 10% compressive strength C at 23°C (23) When the value of is in the above range, it is possible to obtain the effect of exhibiting stable and high impact absorbing performance over a wide temperature range.

[0043] 10% compressive strength at -30℃ C (-30), 10% compressive strength at 80℃ C (80) , and 10% compressive strength C at 23°C (23) can be measured in accordance with JIS K 7181:2011.

[0044] For example, by using the above-mentioned aromatic group-containing polycarbonate resin, which has high heat resistance, as the raw material for the PC foam molded article, the 10% compressive strength change rate can be reduced to 0.6 or less.

[0045] Furthermore, from the viewpoint of further increasing the above-mentioned 10% compressive strength, the closed cell ratio of the PC foam molded article is 70% or more, preferably 80% or more, and more preferably 85% or more.

[0046] Furthermore, from the viewpoint of improving the heat insulating properties of the helmet 10, the thermal conductivity of the impact absorbing liner 20 (foam layer 21) is preferably 0.040 W / m K or less, and more preferably 0.038 W / m K or less. This makes it difficult for external heat to be transmitted to the user's head through the helmet 10 when used in a high-temperature environment, such as in the summer.

[0047] [Embodiment 2] Other embodiments of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0048] The helmet according to this embodiment differs from embodiment 1 in that the impact absorbing liner has a multi-layer structure. The multi-layer structure has at least two layers: a high foam layer and a low foam layer.

[0049] Fig. 3 is a cross-sectional view showing the schematic configuration of the impact absorbing liner 20A provided in the helmet according to this embodiment. As shown in Fig. 3, the impact absorbing liner 20A has a two-layer structure made up of a high-foam layer 22 and a low-foam layer 23. The high-foam layer 22 is formed from a polycarbonate-based resin foam with a high expansion ratio, and the low-foam layer 23 is formed from a polycarbonate-based resin foam with a low expansion ratio. The high-foam layer 22 forms the inner surface of the impact absorbing liner 20A, and the low-foam layer 23 forms the outer surface of the impact absorbing liner 20A. The high-foam layer 22 and the low-foam layer 23 are joined together with an adhesive or the like.

[0050] In the helmet according to this embodiment, the impact absorbing liner 20A has a two-layer structure as described above, so that the two-layer structure deflects the impact energy acting on the impact absorbing liner 20A, and the high foam layer 22 and the low foam layer 23 can dissipate the energy of a relatively low-energy impact or a relatively high-energy impact. More specifically, when an impact force is applied to the helmet, the low foam layer 23 has a relatively high specific gravity, so it appropriately absorbs the impact force received from the shell 1, disperses the impact force over a wide range, and transmits it to the high foam layer 22. Because the impact force acting on the helmet is dispersed and absorbed over a wide range by the low foam layer 23, the pressure acting from the low foam layer 23 to the high foam layer 22 is low. Therefore, the high foam layer 22 has a relatively low specific gravity, so it easily compresses and deforms under the pressure and effectively absorbs the pressure. As described above, with the helmet of this embodiment, the two-layer structure provides good impact attenuation performance without requiring a special increase in the thickness of the impact absorbing liner 20A, and the user's head can be protected from impact forces.

[0051] Furthermore, conventional polystyrene-based resin foam molded products have low toughness, so impact absorbing liners made of polystyrene-based resin foam molded products are vulnerable to multiple impacts at the same location. On the other hand, conventional polypropylene-based resin foam molded products have a high temperature dependency of compressive strength, which is an index of impact absorbing performance.

[0052] As described above, the impact absorbing liner 20A of the helmet according to this embodiment has a two-layer structure consisting of the high foam layer 22 formed from a PC foam molded body with a high expansion ratio and the low foam layer 23 formed from a PC foam molded body with a low expansion ratio, which can improve the absorption performance against the second or more impacts to the same location.

[0053] The expansion ratio of the highly foamed layer 22 is preferably 10 or more, and more preferably 15 or more. In consideration of the impact absorption performance, the expansion ratio of the highly foamed layer 22 is preferably 50 or less, and more preferably 40 or less.

[0054] The expansion ratio of the low foam layer 23 is preferably less than 10, and more preferably less than 8. In consideration of lightness, the expansion ratio of the low foam layer 23 is preferably 3 or more, and more preferably 4 or more.

[0055] The impact absorbing liner provided in the helmet according to this embodiment is not limited to the two-layer structure shown in Fig. 3, but may be a multi-layer structure having at least two layers: a low-foam layer that forms the inner surface of the impact absorbing liner and a high-foam layer that forms the outer surface of the impact absorbing liner. For example, the impact absorbing liner may be a multi-layer structure in which any number of foam layers, such as one or two, are arranged between the high-foam layer 22 and the low-foam layer 23 in the configuration shown in Fig. 3.

[0056] [Embodiment 3] Further, for the sake of convenience, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0057] Fig. 4 is a cross-sectional view showing a schematic configuration of a helmet 10B according to this embodiment. As shown in Fig. 4, helmet 10B differs from embodiments 1 and 2 in that an impact absorbing liner 20B has a low foam layer and a high foam layer disposed in portions corresponding to respective parts of the user's head.

[0058] As shown in FIG. 4, the impact absorbing liner 20B includes low foam layers 24 and 26 and a high foam layer 25. The high foam layer 25 is formed from a polycarbonate-based resin foam with a high expansion ratio, and the low foam layers 24 and 26 are formed from a polycarbonate-based resin foam with a low expansion ratio. In the impact absorbing liner 20B, the low foam layers 24 and 26 are arranged in portions corresponding to the forehead and occipital region, respectively, and the high foam layer 25 is arranged in a portion corresponding to the crown region. Although not shown in FIG. 4, in the impact absorbing liner 20B of the helmet 10B, a high foam layer formed from a polycarbonate-based resin foam with a high expansion ratio is arranged in a portion corresponding to the temporal region. These low foam layer and high foam layer are joined to each other with an adhesive or the like.

[0059] According to the helmet 10B of this embodiment, as described above, the low foam layer and the high foam layer are arranged in the portions corresponding to the respective parts of the user's head, and therefore the energy impact applied to the respective parts of the head can be more effectively absorbed.

[0060] The expansion ratio of high-foam layer 25 and the high-foam layers arranged in the portions corresponding to the temporal region is preferably 10 or more, more preferably 15 or more. In consideration of impact absorption performance, the expansion ratio of high-foam layer 25 and the high-foam layers arranged in the portions corresponding to the temporal region is preferably 50 or less, more preferably 40 or less.

[0061] The expansion ratio of the low foam layers 24 and 26 is preferably less than 10, and more preferably less than 8. In consideration of lightness, the expansion ratio of the low foam layers 24 and 26 is preferably 3 or more, and more preferably 4 or more.

[0062] As described above, the helmets according to Embodiments 1 to 3, which are equipped with impact absorbing liners formed from PC foam molded articles having the above-described properties, have high energy absorption performance not only at room temperature but also at high temperatures, and exhibit little change in energy absorption performance (compression strength) due to temperature changes from low to high temperatures. Therefore, the helmets according to Embodiments 1 to 3 can be advantageously used in places or regions with high temperatures, or in places or locations where temperatures are high. Furthermore, because the helmets according to Embodiments 1 to 3 also have excellent energy absorption performance at low temperatures, they can be used over a wide temperature range. Furthermore, because the shell and impact absorbing liner of the helmets according to Embodiments 1 to 3 are made of the same type of material, material recycling is relatively easy. [Example]

[0063] Examples, comparative examples and reference examples are given below, but the present invention is not limited to these.

[0064] The measurement and evaluation methods used in the following examples and comparative examples are as follows.

[0065] <Measurement method> [Bulk expansion ratio of pre-expanded particles] The bulk expansion ratio of the pre-expanded particles was calculated by placing the pre-expanded particles in a measuring cylinder so that the volume was 1,000 cc, measuring the weight, and using the following formula. Bulk expansion ratio (cc / g) = 1,000 cc / [weight of pre-expanded particles (g)] ... (2) [density] The density of the foamed molded article was calculated according to the following formula in accordance with JIS K 7222:2005. Density (Kg / m 3 ) = Weight of foamed molded product (Kg) / Volume of foamed molded product (m 3 )…(3) [Measurement of thermal conductivity of foam layer] A sample measuring 300 mm in length, 300 mm in width, and 25 mm in thickness was prepared as the foam layer. This sample was allowed to stand at 60°C for 48 hours and then at 23°C for 24 hours. After that, the thermal conductivity (λ) was measured using a thermal conductivity measuring device (HC-074, manufactured by Eiko Seiki Co., Ltd.) according to JIS A1412-2:1999 by the heat flow meter method, with plate temperatures set to 10°C and 30°C (average temperature 20°C, temperature difference 20°C).

[0066] [Expansion ratio] The expansion ratio of the foamed molded article was calculated from the above density using the following formula. Expansion ratio (times) = 1,200 (Kg / m 3 ) / density(Kg / m 3 ) …(4) [10% compressive strength] The resulting foam molded article was cut into a 50 mm length x 50 mm width x 25 mm thickness test piece (excluding the foam molded article skin layer). Using a thermostatic chamber equipped with a Technograph universal material testing machine (manufactured by Minebea Co., Ltd.), the test environment temperature was set to -30°C to +80°C, and the test piece was left in the thermostatic chamber for 3 to 5 hours to adjust the test temperature to the test environment temperature. The compressive strength (MPa) was then measured at 10% compression (2.5 mm displacement) in the temperature range of -30 to +80°C at a compression rate of 10 mm / min.

[0067] The 10% compressive strength measured at temperatures of -30℃, 23℃, and 80℃ (C (-30) , C (23) , C (80) From the above, the 10% compressive strength temperature change rate was calculated based on the following formula (5). 10% compressive strength temperature change rate = |C (-30) -C (80) | / C (23) …(5) <Evaluation method> The following evaluation criteria were set and evaluated.

[0068] (23℃ 10% compressive strength: an evaluation index for energy absorption performance) Excellent: 23℃ 10% compressive strength is greater than 2.0 MPa Good: 23°C 10% compressive strength is 0.5-2.0 MPa Acceptable: 23°C 10% compressive strength 0.1-0.5MPa Not acceptable: 23°C 10% compressive strength less than 0.1 MPa.

[0069] (10% compressive strength change rate: an evaluation index for the temperature dependence of compressive strength) Excellent: 10% compressive strength change rate is less than 0.2 Good: 10% compressive strength change rate is 0.2 to 0.6 Acceptable: 10% compressive strength change rate is 0.6 to 1.0 Unacceptable: 10% compressive strength change rate is greater than 1.0.

[0070] (comprehensive evaluation) Excellent: Either the evaluation of 23°C 10% compressive strength or the evaluation of 10% compressive strength temperature change rate is "Excellent", and the other evaluations are "Good" or better. Thermal conductivity is 0.040 W / m K or less. Good: Both the 23°C 10% compressive strength evaluation and the 10% compressive strength temperature change evaluation are "Good", or either the 23°C 10% compressive strength evaluation or the 10% compressive strength temperature change evaluation is "Excellent" and the other evaluations are "Fair". Thermal conductivity is 0.040 W / m K or less. Pass: Both the 23°C 10% compressive strength evaluation and the 10% compressive strength temperature change evaluation are "passable," or either the 23°C 10% compressive strength evaluation or the 10% compressive strength temperature change evaluation is "good" and the other evaluation is "passable." Thermal conductivity is 0.040 W / m K or less. Unacceptable: Either the evaluation of 10% compressive strength at 23°C or the evaluation of the rate of temperature change of 10% compressive strength is "unacceptable." Thermal conductivity is greater than 0.040 W / m K.

[0071] Example 1 [Formation of expandable resin particles] 80 parts by weight of polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation; NOVAREX M7027BF), 20 parts by weight of polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Corporation; LUPILON H-4000), and 0.5 parts by weight of talc (manufactured by Hayashi Kasei Co., Ltd.; Talcan Powder TP-20) were fed into a 40 mm diameter co-meshing twin-screw extruder (first extruder) at a total feed rate of 50 kg / hr. The cylinder temperature after the raw material feed section of the twin-screw extruder was set to 260°C, and the feed materials were melt-kneaded. Next, 4.0 parts by weight of ethyl chloride and 4.0 parts by weight of cyclopentane as foaming agents were injected into the cylinder after the raw material feed section of the twin-screw extruder, per 100 parts by weight of the melt obtained by melt-kneading, and further melt-kneaded.

[0072] The resulting melt (melt impregnated with the blowing agent) was then supplied to a 90 mm diameter single-screw extruder (second extruder) through a continuation pipe set at 220°C. A gear pump set at 210°C and a diverter valve were connected to the tip of the single-screw extruder. A die was connected downstream of the diverter valve. The die had 55 small holes with a diameter of 0.65 mm and a land length of 5.0 mm and was set at a temperature of 270°C. The cylinder temperature of the single-screw extruder was then set at 210°C to knead the melt, and the melt obtained by melt kneading was extruded through the die connected to the tip of the single-screw extruder at an extrusion (discharge) rate of 54 kg / hr into pressurized water at a temperature of 94°C and a water pressure of 1.3 MPa.

[0073] Immediately after that, a rotary cutter having four blades was used to cut the melt into particles by rotating the cutter at a rotation speed of 2000 rpm, thereby forming expandable resin particles for molding in a mold.

[0074] [Formation of pre-expanded particles] The resulting expandable resin particles were placed in a pre-expanding machine and expanded by introducing steam at 0.16 MPa for 150 seconds. This resulted in the formation of pre-expanded particles. The bulk expansion ratio of the resulting pre-expanded particles was 30 times (cc / g).

[0075] [Production of foamed bead molded body (PC foamed molded body)] A sample of a PC foam molded article for compressive strength measurement was produced as follows. The obtained pre-expanded particles were filled into a mold (in-mold molding mold) attached to a foamed polypropylene molding machine, and water vapor of 0.24 MPa was introduced for 30 seconds to cause in-mold foaming. The resin foam molded article in the mold was then water-cooled until the pressure pressing the mold down to 0.015 MPa (gauge pressure), producing a sample of a PC foam molded article. The sample measured 370 mm long x 320 mm wide x 80 mm thick, with a density of 203 kg / m. 3 It is a rectangular shaped foamed molded body with an expansion ratio of 5.9 times and a closed cell ratio of 85%.

[0076] Test pieces for compressive strength were cut out from the PC foam molded articles. The test pieces were then subjected to compressive strength tests at temperatures of -30°C, 23°C, and 80°C, and the compressive strength at which the thickness displacement (strain) rate reached 10% (10% compressive strength) was determined. Thermal conductivity was also measured. The results are shown in Table 1.

[0077] On the other hand, using a mold for a helmet impact absorbing liner, the pre-expanded particles were foamed in the mold in the same manner as above to carry out the molding process for a helmet impact absorbing liner, and a single-layer impact absorbing liner product (average thickness: 42 mm) was produced.

[0078] Example 2 Density 111Kg / m 3 A PC foam molded sample and an impact absorbing liner were obtained in the same manner as in Example 1, except that the expansion ratio was 10.8 times and the closed cell ratio was 79%, and the PC foam molded sample was subjected to a compressive strength test and thermal conductivity measurement. The results are shown in Table 1.

[0079] Example 3 Density 74.9Kg / m 3A PC foam molded sample and an impact absorbing liner were obtained in the same manner as in Example 1, except that the expansion ratio was 16.0 times and the closed cell ratio was 75%. The PC foam molded sample was subjected to a compressive strength test and thermal conductivity measurement. The results are shown in Table 1.

[0080] Example 4 Density 60.2Kg / m 3 A PC foam molded sample and an impact absorbing liner were obtained in the same manner as in Example 1, except that the expansion ratio was 19.9 times and the closed cell ratio was 72%, and the PC foam molded sample was subjected to a compressive strength test and thermal conductivity measurement. The results are shown in Table 1.

[0081] Example 5 Density 40.2Kg / m 3 A PC foam molded sample and an impact absorbing liner were obtained in the same manner as in Example 1, except that the expansion ratio was 29.8 times and the closed cell ratio was 70%, and the PC foam molded sample was subjected to a compressive strength test and thermal conductivity measurement. The results are shown in Table 1.

[0082] Example 6 A sample of the PC foam molded article obtained in Example 1 (expansion ratio: 5.9) and a sample of the PC foam molded article obtained in Example 3 (expansion ratio: 16.0) were used to prepare an impact absorbing liner with a two-layer structure. Specifically, the sample of the PC foam molded article obtained in Example 1 was machined and arranged to serve as the low foam layer 23 in the impact absorbing liner 20A shown in FIG. 3. Next, a sample of the PC foam molded article obtained in Example 3 was machined and arranged to serve as the high foam layer 22 in the impact absorbing liner 20A shown in FIG. 3. In the obtained two-layer structure, the low foam layer 23 made from the PC foam molded article sample obtained in Example 1 had an average thickness of 17 mm, and the high foam layer 22 made from the PC foam molded article sample obtained in Example 3 had an average thickness of 25 mm.

[0083] The obtained two-layer structure sample was subjected to a compressive strength test and thermal conductivity measurement in the same manner as in Example 1. The results are shown in Table 1.

[0084] Example 7 The sample of the PC foam molded article obtained in Example 1 (expansion ratio: 5.9 times) and the sample of the PC foam molded article obtained in Example 3 (expansion ratio: 16.0 times) were used to prepare the impact absorbing liner shown in Figure 4. Specifically, the PC foam molded article obtained in Example 1 was cut and arranged in the positions of the low foam layers 24 and 26 in the impact absorbing liner 20B shown in Figure 4. Next, the PC foam molded article obtained in Example 3 was cut and arranged in the positions of the high foam layer 25 and the portion corresponding to the temporal region (not shown), thereby preparing an impact absorbing liner with different expansion ratios for different regions of the head.

[0085] The obtained sample was subjected to a compressive strength test and thermal conductivity measurement in the same manner as in Example 1. The results are shown in Table 1.

[0086] (Comparative Example 1) Density 175Kg / m 3 Except for using a foam molded article made of a polypropylene resin with an expansion ratio of 5.1 and a closed cell ratio of 93%, a compressive strength test and thermal conductivity measurement were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0087] (Comparative Example 2) Density 99Kg / m 3 Except for using a foam molded article made of a polypropylene resin with an expansion ratio of 9.0 and a closed cell ratio of 88%, a compressive strength test and thermal conductivity measurement were carried out in the same manner as in Example 1. The results are shown in Table 1.

[0088] [Table 1] [Explanation of symbols]

[0089] 1 shell 10, 10B helmet 20, 20A, 20B Impact absorbing liner 21 Foam layer 22, 25 High foam layer 23, 24 Low foam layer

Claims

1. a shell that is a molded body of a thermoplastic resin or a thermosetting resin; an impact absorbing liner disposed inside the shell, The helmet, wherein the impact absorbing liner comprises a foam layer formed from a polycarbonate-based resin foam.

2. 2. The helmet according to claim 1, wherein the foam layer has a value obtained by dividing the absolute value of the difference between the 10% compressive strength at -30°C and the 10% compressive strength at 80°C by the 10% compressive strength at 23°C of 0.6 or less.

3. 2. The helmet according to claim 1, wherein the impact absorbing liner is a single-layer structure made of the foam layer.

4. the impact absorbing liner is a multilayer structure having at least two layers: a high foam layer formed from a polycarbonate-based resin foam with a high foaming ratio, and a low foam layer formed from a polycarbonate-based resin foam with a low foaming ratio; 2. The helmet according to claim 1, wherein the high foam layer forms an inner surface of the impact absorbing liner, and the low foam layer forms an outer surface of the impact absorbing liner.

5. The impact absorbing liner comprises a high foam layer formed from a polycarbonate-based resin foam having a high foaming ratio, and a low foam layer formed from a polycarbonate-based resin foam having a low foaming ratio, In the impact absorbing liner, the low-foam layer is disposed in areas corresponding to the front and back of the head, The helmet according to claim 1 , wherein the high-foam layer is disposed in portions corresponding to the crown and sides of the head.

6. The high foam layer has an expansion ratio of 10 times or more, 6. The helmet according to claim 4, wherein the low foam layer has an expansion ratio of less than 10 times.

7. 6. The helmet according to claim 1, wherein the impact absorbing liner has a thermal conductivity of 0.040 W / m·K or less.

8. 6. The helmet according to claim 1, wherein the shell is made of a polycarbonate resin.

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