Vehicle seat core material

Abstract

The present invention provides a vehicle seat core material that is less likely to generate cracks or defects in a thin wall portion. The present invention employs a vehicle seat core material (100) that includes a thermoplastic resin foamed particle molded body (10) having a substantially rectangular shape in plan view, has a rear-side thin wall portion having a thickness (t) of 10 to 40 mm that is thinner than the average thickness of the foamed particle molded body, the average molded body density (Z) of the foamed particle molded body is 20 to 50 kg / m 3 , the ratio (Y / Z) of the molded body density (Y) of the rear-side thin wall portion to the average molded body density (Z) of the foamed particle molded body is 1.05 to 3, and the fusion rate of the rear-side thin wall portion of the foamed particle molded body (10) is 70% or more.

Description

TECHNICAL FIELD

[0001] The present application relates to a vehicle seat core. BACKGROUND

[0002] In recent years, as a vehicle seat core for a vehicle such as an automobile, a vehicle seat core composed of a thermoplastic resin foamed particle molded body (hereinafter, also referred to as "foamed particle molded body") is used. Further, there is a vehicle seat in which a cushioning material such as a polyurethane foam is layered on the upper surface side of the seat core, and further, a seat cover made of cloth, leather, or the like is disposed on the upper surface side of the polyurethane foam (for example, Patent Documents 1 and 2).

[0003] The seat core composed of the foamed particle molded body as described above has a thick-walled front portion and a thin-walled rear portion.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT DOCUMENTS

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-29844

[0007] Patent Document 2: International Publication No. 2017 / 135456 SUMMARY

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] However, there is a possibility that the mechanical strength in the thin-walled portion of the foamed particle molded body of the thin-walled portion is insufficient. Further, the foamed particle molded body can be broken or damaged at the time of transportation or the like. In particular, in a case where the front portion of the seat core composed of the foamed particle molded body is formed to be thick-walled, and the rear portion of the seat core is formed to be thin-walled, a hooking tool for a vehicle is sometimes provided to the molded body portion on the rear side that is thin-walled. The load by the hooking tool is applied to the thin-walled portion, and thus the molded body portion on the rear side that is thin-walled can be further broken or damaged.

[0010] The present application has been achieved in view of the above-described background art, and an object thereof is to provide a vehicle seat core in which a thin-walled portion of a seat core composed of a foamed particle molded body is less likely to be broken or damaged.

[0011] SOLUTION TO PROBLEM

[0012] In order to achieve the above object, the present application employs a vehicle seat core described in the following items [1] to [6].

[0013] 〔1〕 A seat core for a vehicle, characterized by comprising a molded body of thermoplastic resin foamed particles, the molded body of thermoplastic resin foamed particles being substantially rectangular in plan view, the average molded body density (Z) of the molded body of thermoplastic resin foamed particles being 20 to 50 kg / m 3 the molded body of thermoplastic resin foamed particles having a rear-side thin-walled portion having a thickness of 10 to 40 mm thinner than the average thickness of the molded body of thermoplastic resin foamed particles on the rear side of the molded body of thermoplastic resin foamed particles, the ratio (Y / Z) of the molded body density (Y) of the rear-side thin-walled portion to the average molded body density (Z) of the molded body of thermoplastic resin foamed particles being 1.05 to 3, and the sintering rate of the rear-side thin-walled portion of the molded body of thermoplastic resin foamed particles being 70% or more.

[0014] 〔2〕 The seat core for a vehicle according to the above item 〔1〕, characterized in that the molded body of thermoplastic resin foamed particles has a front-side thick-walled portion having a thickness of 80 mm or more on the front side of the molded body of thermoplastic resin foamed particles.

[0015] 〔3〕 The seat core for a vehicle according to the above item 〔2〕, characterized in that the sintering rate of the front-side thick-walled portion of the molded body of thermoplastic resin foamed particles is 40% or more.

[0016] 〔4〕 The seat core for a vehicle according to any one of the above items 〔1〕 to 〔3〕, characterized in that a frame member is embedded in the rear-side thin-walled portion of the molded body of thermoplastic resin foamed particles along the long dimension of the molded body of thermoplastic resin foamed particles.

[0017] 〔5〕 The seat core for a vehicle according to any one of the above items 〔1〕 to 〔4〕, characterized in that the foamed particles constituting the molded body of thermoplastic resin foamed particles are multilayer foamed particles having a foamed core layer and a coating layer covering the foamed core layer.

[0018] 〔6〕 The seat core for a vehicle according to the above item 〔5〕, characterized in that the melting point of the coating layer constituting the multilayer foamed particles is 1 to 25°C lower than the melting point of the foamed core layer.

[0019] Effects of the Invention

[0020] The seat core for a vehicle of the present invention described above comprises a molded body of thermoplastic resin foamed particles which is substantially rectangular in plan view, and the molded body of thermoplastic resin foamed particles has a rear-side thin-walled portion having a thickness of 10 to 40 mm thinner than the average thickness thereof on the rear side. Furthermore, the average molded body density (Z) of the molded body of thermoplastic resin foamed particles is 20 to 50 kg / m 3The ratio (Y / Z) of the density (Y) of the rear-side thin portion of the molded body described above to the average density (Z) of the molded body of the thermoplastic resin foamed particles is 1.05 to 3, and the fusion rate of the rear-side thin portion of the molded body of the thermoplastic resin foamed particles is 70% or more. Such a vehicle seat core material is a vehicle seat core material in which cracking and damage are less likely to occur even in the rear-side thin portion of the vehicle seat core material. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a conceptual perspective view showing one embodiment of the vehicle seat core material of the present application.

[0022] Figure 2 is a conceptual perspective view showing a frame member used in the vehicle seat core material shown in Figure 1

[0023] Figure 3A is an explanatory view conceptually showing a method of filling the foamed particles into a mold by cracking filling.

[0024] Figure 3B is a view showing the state of the foamed particles when the mold is completely closed.

[0025] Figure 4A is an explanatory view conceptually showing the front side, the rear side, and the thickness of each portion of the molded body of the foamed particles.

[0026] Figure 4B is an explanatory view conceptually showing the front side, the rear side, and the thickness of each portion of the molded body of the foamed particles. DETAILED DESCRIPTION

[0027] Hereinafter, an embodiment of the vehicle seat core material of the present application will be described in detail with reference to the accompanying drawings.

[0028] Note that in the following description, preferred numerical ranges of the present application are sometimes appropriately indicated, in which case the preferred range, the more preferred range, and the particularly preferred range of the upper limit and the lower limit of the numerical range can be determined in accordance with the combination of all the upper limits and the lower limits. Further, in the case where no specific description is given, the front-rear direction, the left-right direction, and the up-down direction of the vehicle seat core material are the same as the front-rear direction, the left-right direction, and the up-down direction of the vehicle when the vehicle seat core material is installed in the vehicle.

[0029] The vehicle seat core material 100 of the present application is as shown in Figure 1 ​As shown, a thermoplastic resin foamed particle molded body 10, which is formed into a thick wall on the front side, a thin wall on the rear side, and a substantially rectangular shape in plan view, forms the shape of the outer shape of the seat core material. A urethane foam or the like cushioning material is generally layered on the upper surface of the seat core material 100, and a cloth or leather seat cover is attached to the surface of the cushioning material. In this way, a vehicle seat including the seat core material, the cushioning material, and the seat cover is formed, and the vehicle seat is provided in a portion that becomes a seat of a vehicle.

[0030] A rear side thin wall portion (thin wall region) having a thickness thinner than the average thickness of the foamed particle molded body 10, and a thickness (t) of 10 to 40 mm is formed on the rear side of the foamed particle molded body 10. The rear side thin wall portion preferably has a portion in which the thickness (t) is formed to be 35 mm or less, and the portion having the thickness of 35 mm or less accounts for 70% or more of the volume of the rear side thin wall portion.

[0031] On the other hand, a front side thick wall portion (thick wall region) having a thickness (T) of 80 mm or more is preferably formed on the front side of the foamed particle molded body 10. The front side thick wall portion more preferably has a portion in which the thickness (T) is formed to be 85 mm or more, and the portion having the thickness of 85 mm or more accounts for 70% or more of the volume of the front side thick wall portion. Further, the front side thick wall portion particularly preferably has a portion in which the thickness (T) is formed to be 90 mm or more, and the portion accounts for 80% or more of the volume of the front side thick wall portion. On the other hand, the upper limit of the thickness (T) of the front side thick wall portion is approximately 150 mm.

[0032] Further, the front side thick wall portion of the foamed particle molded body 10 having a thickness (T) of 80 mm or more accounts for 50% or more of the volume of the entire foamed particle molded body 10, and further preferably accounts for 60% or more. Note that the upper limit is approximately 90%. If within the above range, it is easy to produce a vehicle seat core material composed of the foamed particle molded body 10, which is lightweight and has excellent seating feeling.

[0033] On the other hand, the rear side thin wall portion of the foamed particle molded body 10 having a thickness (t) of 10 to 40 mm accounts for 5% or more of the volume of the entire foamed particle molded body 10, and further preferably accounts for 8% or more. Note that the upper limit is approximately 20%. If within the above range, it is easy to produce a vehicle seat core material composed of the foamed particle molded body 10, which has excellent strength.

[0034] Note that, in the present specification, the front side of the foamed particle molded body 10 is as shown in FIG. 1, and the rear side is as shown in FIG. 2. Figure 4A , Figure 4BConceptually shown is a portion from the center in the front-rear direction of the foamed particle molded body 10 to the front. On the other hand, the rear side of the foamed particle molded body 10 is a portion from the center in the front-rear direction of the foamed particle molded body 10 to the rear.

[0035] Further, the thickness (T) of the foamed particle molded body 10 or the thickness (t) of the foamed particle molded body 10 is, for example, Figure 4A , Figure 4B Conceptually shown is the length in the vertical direction of the center line a of the thickness of the foamed particle molded body 10 at each position of the foamed particle molded body portion.

[0036] The foamed particle molded body 10 is a substantially rectangular shape in plan view, and further preferably an oblong shape in plan view. Further, the length (L) of the foamed particle molded body 10 is 1000 to 1500 mm, the width (W) of the foamed particle molded body 10 is about 400 to 600 mm, and the shape of the foamed particle molded body 10 is more preferably a substantially oblong shape.

[0037] Note that in the present specification, a substantially rectangular shape or a substantially oblong shape means, for example, that the corners of a rectangle or an oblong can have rounded corners. Further, a part or all of the sides constituting the rectangle or the oblong can be curved sides. Further, the dimensions of the length and the width of the substantially oblong shape of the foamed particle molded body 10 can be appropriately designed according to the vehicle to be installed. Therefore, the above dimensions are not limited in any way. Also, a through hole for coping with weight reduction or a through hole for corresponding to the positional relationship with other members can be formed at an appropriate position of the foamed particle molded body 10.

[0038] The average molded body density (Z) of the foamed particle molded body 10 is 20 to 50 kg / m 3 By setting the average molded body density of the foamed particle molded body 10 to the above range, a vehicle seat core material excellent in strength and lightness can be obtained. From this viewpoint, the lower limit of the average molded body density (Z) of the foamed particle molded body 10 is preferably 25 kg / m 3 , more preferably 27 kg / m 3 , and particularly preferably 30 kg / m 3 . The upper limit of the average molded body density (Z) of the foamed particle molded body 10 is preferably 45 kg / m 3 , more preferably 43 kg / m 3 , and particularly preferably 40 kg / m 3 .

[0039] Further, the ratio (Y / Z) of the density of the molded body of the rear-side thin wall portion (Y) to the average density of the molded body of the foamed particle molded body 10 (Z) is 1.05 to 3. By setting the density of the molded body of the rear-side thin wall portion (Y) to be higher than the average density of the molded body (Z) and satisfying the above range, the strength of the thin wall portion can be improved. From this viewpoint, the lower limit of the ratio (Y / Z) of the density of the molded body of the rear-side thin wall portion (Y) to the average density of the molded body of the foamed particle molded body (Z) is preferably 1.08, and more preferably 1.10. Further, the upper limit of the ratio (Y / Z) is preferably 2, and more preferably 1.5.

[0040] Further, the ratio (Y / X) of the density of the molded body of the rear-side thin wall portion (Y) to the density of the molded body of the front-side thick wall portion (X) of the foamed particle molded body 10 is preferably 1.1 to 3. By setting the density of the molded body of the rear-side thin wall portion (Y) to be higher than the density of the molded body of the front-side thick wall portion (X) and satisfying the above range, the strength of the thin wall portion can be improved. In particular, in the present application, the molded body satisfying the above ratio (Y / X) of the density of the molded body of the rear-side thin wall portion (Y) to the density of the molded body of the front-side thick wall portion (X) is formed as an integrally molded body, whereby the seat core material as a whole has excellent strength. From this viewpoint, the lower limit of the ratio (Y / X) of the density of the molded body of the rear-side thin wall portion (Y) to the density of the molded body of the front-side thick wall portion (X) is more preferably 1.1, and particularly preferably 1.15. Further, the upper limit of the ratio (Y / X) is more preferably 2, and particularly preferably 1.5.

[0041] Note that the average density of the molded body (Z) of the foamed particle molded body 10 can be measured as described below.

[0042] In the foamed particle molded body 10 after the end of the molding shrinkage, a cutting sample of a prescribed size is cut out from positions at which 15 or more positions are substantially equally spaced apart in the front-rear direction and the left-right direction. Then, the volume V (cm3) of the cutting sample is calculated, and the weight M (g) of the cutting sample is measured. Then, M / V is calculated by dividing the weight M (g) of the cutting sample by the volume V (cm3) of the cutting sample. The values of M / V calculated for each cutting sample can be arithmetically averaged to calculate the average density of the molded body (Z) of the foamed particle molded body 10. 3 3

[0043] Further, the density of the molded body of the front-side thick wall portion (X) can be measured as described below.

[0044] ​​A cut sample of a prescribed size is cut from a portion of the foamed particle molded body 10 located on the front side after the end of the molding shrinkage and having a thickness T satisfying T > 80 mm. For this cut sample, the value of Mx / Vx can be calculated by dividing the weight Mx (g) of the cut sample by the volume Vx (cm3) of the cut sample, and this value of Mx / Vx is taken as the molded body density (X) of the front side thick wall portion. 3 ) while the value of My / Vy is taken as the molded body density (Y).

[0045] Further, the molded body density (Y) of the rear side thin wall portion can be measured as described below.

[0046] A cut sample of a prescribed size is cut from a portion of the foamed particle molded body 10 located on the rear side after the end of the molding shrinkage and having a thickness t satisfying t < 40 mm. For this cut sample, the value of My / Vy can be calculated by dividing the weight My (g) of the cut sample by the volume Vy (cm3) of the cut sample, and this value of My / Vy is taken as the molded body density (Y). 3 ) while the value of My / Vy is taken as the molded body density (Y).

[0047] Note that in the case where the measurement portion described above is formed with projections and depressions, etc., it is preferable to avoid the projections and depression portions and sample the cut sample. Further, in the case where the foamed particle molded body is embedded with a frame member, the portion is removed and measurement is performed.

[0048] The foamed particle molded body 10 having a ratio (Y / Z) of the molded body density (Y) of the rear side thin wall portion to the average molded body density (Z) of the foamed particle molded body of 1.05 to 3, i.e., the foamed particle molded body 10 in which the molded body density (Y) of the rear side thin wall portion is made higher than the average molded body density (Z), can be obtained, for example, by performing molding using a crack filling method. Note that the crack filling method refers to a method in which, as shown in FIG. 6, a small gap (crack gap δ) is provided instead of completely closing the mold, and foamed particles are filled into the mold and molding is performed. According to the method described above, molded bodies having different densities can be obtained using one kind of foamed particles. Figure 3A

[0049] Thus, by performing crack filling and molding the foamed particle molded body serving as a seat core material into a specific shape so that the thin wall portion is compressed more than other portions in the mold, the molded body density (Y) of the thin wall portion can be made higher than the average molded body density (Z), and the thin wall portion can be made into a locally high density and a strong molded body.

[0050] ​Further, the fusion rate of the rear-side thin-walled portion of the foamed particle molded body 10 is 70% or more. This can set the molded body density (Y) of the rear-side thin-walled portion to be higher than the average molded body density (Z) as described above, and the fusion rate is also sufficiently high, thereby providing a vehicle seat core material in which cracking and defects are less likely to occur even in the rear-side thin-walled portion. From this viewpoint, the lower limit of the fusion rate of the rear-side thin-walled portion is preferably 75%, more preferably 78%, and particularly preferably 80%. The upper limit of the fusion rate of the rear-side thin-walled portion is preferably 95%, more preferably 93%, and particularly preferably 92%.

[0051] In the foamed particle molded body 10 described above, in order to prevent cracking and defects in the thin-walled portion and maintain the strength of the vehicle seat core material as a whole, it is important to increase the molded body density (Y) of the rear-side thin-walled portion and increase the fusion rate of the rear-side thin-walled portion.

[0052] Here, generally, if the molded body density is to be increased, the gaps between the foamed particles in the mold become narrow, the flow of the molding steam deteriorates, and thus there is a tendency for the fusion of the foamed particles to each other to decrease. However, in the thin-walled portion, the molded body thickness is thin, and thus the flow of the molding steam in the thickness direction is sufficiently ensured, and a decrease in the fusion is not observed. Therefore, in the case where the compression rate of the thin-walled portion is locally increased by molding using the crack filling method described above, the molded body density (Y) of the thin-walled portion can be increased without decreasing the fusion rate of the foamed particles of the entire molded body.

[0053] On the other hand, in the front-side thick-walled portion of the foamed particle molded body 10, the thickness of the molded body is thick, and thus the molding steam is less likely to penetrate to the inside in the thickness direction. Further, there is a tendency for the fusion of the foamed particles to each other in the thick-walled portion to easily decrease. Therefore, if the molding steam is planned to be increased in order to increase the fusion of the front-side thick-walled portion, on the other hand, the temperature in the thin-walled portion becomes superheated. Thus, it can be difficult to obtain a foamed particle molded body with a good appearance. Therefore, generally, in a foamed particle molded body having both a thick-walled portion and a thin-walled portion, it is difficult to maintain the appearance of the foamed particle molded body and integrally mold the thick-walled portion and the thin-walled portion.

[0054] In such a case, for example, as the foamed particles that form the foamed particle molded body 10, multilayer foamed particles having a foamed layer as a core layer and a coating layer on the surface of the foamed layer (core layer) described in detail later can also be used. In the case of such multilayer foamed particles, by using a resin with excellent fusion in the coating layer, the fusion of the foamed particles themselves can be increased. By using such multilayer foamed particles, a foamed particle molded body that maintains a good appearance and in which the fusion rate in the front-side thick-walled portion is increased and the strength of the rear-side thin-walled portion is also increased can be obtained.

[0055] Further, the multilayered foamed particles having good fusion property described above can be used, and a method in which molding steam easily flows in the mold at the time of molding can be adopted. That is, by locally forming more steam holes in the portion of the molding die corresponding to the thick wall portion, more heated steam is caused to flow into the molding space of the thick wall portion, and the fusion rate of the thick wall portion is locally increased.

[0056] Note that the lower limit of the fusion rate of the front-side thick wall portion is preferably 40%, more preferably 45%, and further preferably 50%. The upper limit of the fusion rate of the front-side thick wall portion is more preferably 90%, and further preferably 80%.

[0057] The fusion rate of the foamed particle molded body 10 described above can be found based on the proportion of the number of foamed particles in which the material is broken (fusion rate) among the foamed particles exposed on the fracture surface when the foamed particle molded body is broken.

[0058] Specifically, a sample of the foamed particle molded body is cut in a notch in the thickness direction of the foamed particle molded body using a cutter, and then the foamed particle molded body is broken from the notch. Next, the number of foamed particles (n) present on the fracture surface and the number of foamed particles in which the material is broken (b) are measured. Further, the ratio (b / n) of (b) to (n) can be expressed in percentage as the fusion rate (%).

[0059] Note that, in terms of the fusion rate of the front-side thick wall portion, a cutting sample of a prescribed size is cut from the portion of the foamed particle molded body 10 located on the front side after the molding shrinkage ends and having a thickness T of 80 mm or more, and the fusion rate is found for the cutting sample by the above-described method of measuring the fusion rate of the foamed particle molded body 10.

[0060] Further, in terms of the fusion rate of the rear-side thin wall portion, a cutting sample of a prescribed size is cut from the portion of the foamed particle molded body 10 located on the rear side after the molding shrinkage ends and having a thickness t of 40 mm or less, and the fusion rate is found for the cutting sample by the above-described method of measuring the fusion rate of the foamed particle molded body 10.

[0061] The foamed particles that form the foamed particle molded body 10 described above can be single-layered foamed particles composed only of a foamed layer, or multilayered foamed particles having a foamed layer as a core layer and a coating layer on the surface of the foamed layer (core layer).

[0062] In the case of the multilayered expanded particles, the resin constituting the expanded core layer and the resin constituting the coating layer are not particularly limited as long as they are thermoplastic resins, and for example, resins having the same properties or resins having different melting points can be used. In particular, the resin constituting the coating layer is preferably a resin having a lower melting point than the resin constituting the expanded core layer. Specifically, the melting point of the resin constituting the coating layer is preferably 1 to 25°C lower, more preferably 3 to 20°C lower, and particularly preferably 5 to 15°C lower than the melting point of the resin constituting the core layer. By setting the difference in melting point between the resin constituting the coating layer and the resin constituting the core layer to the above range, an expanded particle molded body having good fusion can be obtained even when in-mold molding is performed at a low molding vapor pressure.

[0063] Note that the melting point of the above resin is a value obtained as a peak temperature of an endothermic peak accompanying melting of the resin on a DSC curve when the DSC curve is plotted using a differential scanning calorimeter (DSC) at a heating rate of 10°C / min using "a case where the melting temperature is measured after a certain heat treatment" (both the heating rate and the cooling rate in the state adjustment of the test piece are set to 10°C / min) described in JIS K7121 (1987). Note that in the case where a plurality of endothermic peaks exist on the DSC curve, the peak of the endothermic peak having the largest area is taken as the melting point. As a measuring device, for example, DSC Q1000 manufactured by TA Instruments, Inc. or the like can be used.

[0064] As the base resin constituting the expanded particles, for example, polystyrene-based resins, polyolefin-based resins such as polyethylene or polypropylene, polyester-based resins such as polybutylene succinate, polyethylene terephthalate, or polylactic acid, or polycarbonate-based resins can be cited. In addition, a composite resin of a polystyrene-based resin and a polyolefin-based resin, a mixture of two or more of the above resins, or the like can be used. Among them, a thermoplastic resin containing a crystalline resin such as a polyolefin-based resin or a composite resin of a polyolefin-based resin and a polystyrene-based resin is preferable. As the above polyolefin-based resin, a polyethylene-based resin or a polypropylene-based resin is preferable, and from the viewpoint of strength and impact resistance, a polypropylene-based resin is more preferable.

[0065] In the case of the multilayered expanded particles, the base resins of the core layer and the coating layer can be the same resins as the above expanded particles. Among them, the core layer is preferably a polyolefin-based resin, and the coating layer is preferably a polyolefin-based resin, and more preferably the core layer is a polypropylene-based resin and the coating layer is a polypropylene-based resin or a polyethylene-based resin. The weight ratio of the coating layer to the core layer in the multilayered expanded particles is preferably 1:99 to 20:80, and more preferably 4:96 to 15:85.

[0066] In the foamed particle molded body 10, a frame member is sometimes embedded. Therefore, the seat core material includes a thermoplastic resin foamed particle molded body, and not only a case where only the foamed particle molded body 10 is used can be cited, but also a case where the foamed particle molded body 10 and the frame member are used can be cited. By embedding the frame member, the strength of the seat core material 100 is improved, and the mounting to the vehicle becomes easy. From this viewpoint, the frame member is preferably embedded at least in the thin-walled portion of the rear side of the foamed particle molded body 10. Further, it is particularly preferable that, as shown in Figure 1 FIG. 8, a ring-shaped frame member is embedded along the outer edge of the foamed particle molded body 10. In addition, the seat core material preferably does not contain urethane foam.

[0067] In Figure 1 the illustrated embodiment, a ring-shaped frame member 30 is embedded along the outer edge of the foamed particle molded body 10. The front hooking tool 31 and the rear hooking tool 32 are respectively arranged at appropriate portions of the ring-shaped frame member 30. Also, as shown in Figure 1 FIG. 8, a part of the hooking tools 31, 32 protrudes outward of the foamed particle molded body 10. Here, the ring-shaped frame member 30 includes a case where the wire constituting the frame member is seamlessly formed in a ring shape along the outer edge of the foamed particle molded body 10. In addition, a case where the wire constituting the frame member is joined to another member (for example, a plate-shaped sheet portion) to make the entire shape a ring shape is also included. Further, the seamless wire refers to not only one continuous wire, but also a continuous body of two or more wires that are joined to each other at prescribed portions by welding or the like.

[0068] The above-described wire and sheet constituting the frame member 30 are, for example, generally constituted by a metal member such as iron, aluminum, or copper, a resin member, or a member such as ceramic. Among them, from the viewpoint of durability, strength, and heat resistance to heat during molding of the foamed particle molded body, it is preferable to include a metal member. Among them, it is more preferable that the wire and sheet constituting the frame member 30 are substantially constituted by a metal member. As the above-described metal member, a steel material is particularly preferable. The frame member 30 can efficiently reinforce the foamed particle molded body 10 by joining and bending processing of these members by welding or the like. In addition, the frame member 30 supports the hooking tools 31, 32 by being joined to the hooking tools 31, 32 of the vehicle.

[0069] The above-described foamed particle molded body 10 in which the frame member 30 is embedded can be manufactured by the in-mold foaming method described below.

[0070] First, the frame member 30 is arranged at a prescribed position in a mold for molding a seat core material for a vehicle. Then, the foamed particle is filled into the mold by the above-described crack filling method, and the crack gap of the mold is closed.

[0071] Then, by introducing heated steam into the mold, the foamed particles are heated to be secondarily foamed, and the foamed particles are fused to each other.

[0072] Thus, the seat core material 100 composed of the composite molded body in which the frame member 30 is embedded in the foamed particle molded body 10 is manufactured.

[0073] The seat core material 100 thus manufactured is an integrally molded product of the foamed particle molded body 10 and the frame member 30, and the integrality of both is excellent.

[0074] The seat core material 100 of the present application described above includes a foamed particle molded body 10 of a thermoplastic resin having a substantially rectangular shape in plan view, and a rear-side thin-walled portion having a thickness (t) of 10 to 40 mm and a molded body density (Y) higher than the average molded body density (Z) of the foamed particle molded body 10. 3 The ratio (Y / Z) of the molded body density (Y) of the rear-side thin-walled portion to the average molded body density (Z) of the foamed particle molded body 10 is as high as 1.05 to 3, and the fusion rate of the rear-side thin-walled portion of the foamed particle molded body 10 is as high as 70% or more. Such a seat core material 100 for a vehicle is a seat core material for a vehicle in which cracking and damage are less likely to occur even in the rear-side thin-walled portion.

[0075] Example

[0076] The example and the comparison using the following multilayer foamed particles were carried out as described below.

[0077] Properties of the multilayer foamed particles (core layer: polypropylene-based resin, coating layer: polyethylene-based resin) used

[0078] Apparent density: 30 g / L.

[0079] High-temperature peak heat: 14.8 J / g.

[0080] Melting heat: 73.6 J / g.

[0081] Melting point of the core layer resin: 141.5°C.

[0082] Melting point of the coating layer resin: 131°C.

[0083] Weight ratio of the coating layer resin: 3%.

[0084] An iron wire having a diameter of 4.5 mm and a tensile strength (JIS G 3532 SWM-B) of 500 N / mm 2 and an iron sheet having a thickness of 1 mm, a width of 80 mm, and a length of 170 mm were used to manufacture a seat core material 100 for a vehicle. Figure 2The frame member 30 shown is constructed with the same frame member. For the iron U-hooks constituting the front hook tool 31 at both front sides and the rear hook tool 32 at one rear side, iron wire with a diameter of 5mm is used. The iron wire and iron sheet constituting the frame member 30 are joined by welding. Regarding the iron U-hook constituting the front hook tool 31, its two ends are joined to the iron sheet by welding.

[0085] The aforementioned frame component 30 is set in the fabrication Figure 1 The mold shown is used for molding the seat core material for vehicles. The mold has the following dimensions: total volume: 32L, length L: 1330mm, width W: 600mm, thickness T at front part A: 100mm, thickness T at front part B: 90mm, thickness T at front part C: 80mm, thickness t at rear part D: 35mm, thickness t at rear part E: 30mm, and thickness t at rear part F: 25mm. After molding, a seat core material corresponding to the shape of the mold is obtained.

[0086] Next, the mold is opened and closed in a direction roughly corresponding to the thickness direction of the front part of the seat core material, and the mold is closed until it is opened to 10mm (crack gap δ: 10mm). Then, the above-mentioned multi-layer foam particles are filled into the mold, and the mold is completely closed by flattening the filled multi-layer foam particles (crack filling method).

[0087] At this time, as Figure 3A As shown, if the interval of the crack gap is set to δ, then the thickness of the thick-walled portion on the front side of the seat core material becomes T+δ, and the thickness of the thin-walled portion on the rear side becomes t+δ (where t < T). Next, as... Figure 3B As shown, if the crack gap in the mold is closed, the front thick-walled portion of the seat core material is compressed from thickness T+δ to T. Therefore, the molded body density of the front thick-walled portion becomes (1+δ / T) times that before compression, resulting in the compression ratio shown in Table 1. On the other hand, the thickness of the rear thin-walled portion of the seat core material is compressed from t+δ to t. Therefore, the molded body density of the rear thin-walled portion becomes (1+δ / t) times that before compression, resulting in the compression ratio shown in Table 1. Thus, by performing crack molding, it is possible to achieve a higher molded body density for the rear thin-walled portion of the seat core material than for the front thick-walled portion, provided that the apparent density of the foam particles themselves is the same, and the filling density of the foam particles in the front thick-walled portion before the gap is closed is the same as that in the rear thin-walled portion.

[0088] Next, a preliminary heating (degassing step) was performed by supplying steam into the mold for 4 seconds in a state where the drain valves of the mold of both sides were opened. Then, heating was performed from one side at a molding steam pressure of 0.14 MPa (first heating), and then heating was performed from the opposite direction at a molding steam pressure of 0.20 MPa (second heating), and thereafter, formal heating was performed by supplying steam from both sides of the mold at a molding steam pressure of 0.28 MPa for 3 seconds.

[0089] After the heating was completed, the pressure of the mold was released, and then cooling was performed to obtain the foamed particle molded body 10.

[0090] After the obtained molded body was cured at 75°C for 12 hours, the molded body was slowly cooled for 6 hours. The cured molded body was used as a seat core material.

[0091] The average molded body density (Z) of the foamed particle molded body constituting the seat core material was 30 kg / m 3 .

[0092] With respect to the seat core material of the example obtained as described above, the compression ratio, the molded body density, the fusion ratio, and the tensile strength were measured for the portions of the wall thickness of the front portions A to C and the portions of the thin wall of the rear portions D to F of the foamed particle molded body 10 (refer to Figure 1 ). The measurement results are shown in Table 1.

[0093] Note that the compression ratio, the molded body density, and the like were calculated as described below.

[0094] (Calculation of the compression ratio)

[0095] The length of the mold in the moving direction of the mold in the portion corresponding to each portion (A to F) of the seat core molding mold described above was set to (a mm), and the foamed particles were filled in a state where the mold was opened by 10 mm from the fully closed state, and after the filling was completed, the compression ratio in the case where the mold was fully closed was calculated according to the following formula (10 mm / a mm) x 100.

[0096] (Sampling of the test pieces)

[0097] In the foamed particle molded body 10 after the molding shrinkage was completed, cut-out samples having a test piece length of 150 mm in the left-right direction of the foamed particle molded body 10, a test piece width of 25 mm in the thickness direction of the foamed particle molded body 10, and a test piece thickness of 20 mm in the front-rear direction of the foamed particle molded body 10 were cut out from six positions A to F shown in Figure 1 . Note that the test pieces were taken from the center portion in the thickness direction of the foamed particle molded body 10, and three test pieces were taken from each of the sample positions A to F described above.

[0098] (Measurement of molded body density)

[0099] The bulk volume (150 x 25 x 20 (mm 3 )) was calculated from the outer dimensions of each test piece. In addition, the weight (g) of each test piece was accurately measured. The weight of each test piece calculated as described above was divided by the bulk volume of the test piece to convert the unit, and thereby the density (kg / m 3 ) of the foamed particle molded body was calculated.

[0100] In addition, the molded body density (X) or (Y) of the sample positions of A to F described in Table 1 is an average value of three test pieces taken at each sample position in Figure 1 .

[0101] Note that the average molded body density (Z) of the foamed particle molded body 10 is an average value of the molded body densities of five positions each taken in the front side, the rear side, and the central portion in the left-right direction, calculated separately.

[0102] (Measurement of fusion rate)

[0103] From the six positions of A to F described in Figure 1 , a cut sample having a test piece length of 150 mm in the left-right direction of the foamed particle molded body 10, a test piece width of 75 mm in the thickness direction of the foamed particle molded body 10, and a test piece thickness of 25 mm in the front-rear direction of the foamed particle molded body 10 was cut out as a test piece.

[0104] A cut of 2 mm in depth was formed on one surface (one of the faces of 150 mm in length, 75 mm in width, and 25 mm in thickness) of the test piece (150 mm in length, 75 mm in width, and 25 mm in thickness) in a manner to cross the total width. Next, the test piece was bent in a direction to expand the cut of the test piece until the test piece broke, or the both end portions of the test piece abutted. Next, the broken surface of the test piece was observed, and the number of foamed particles whose interior broke and the number of foamed particles whose interface peeled off were visually measured, respectively. Next, the proportion of the number of foamed particles whose interior broke with respect to the total number of foamed particles whose interior broke and foamed particles whose interface peeled off was calculated.

[0105] Further specifically, first, for a molded body sample of a cuboid shape of 150 mm (length) x 75 mm (width) x 25 mm (thickness), a cut of a depth of 2 mm was made in the central portion in the length direction on one surface (one of the surfaces of 150 mm in length and 25 mm in width) in a manner to cross the total width, and this was used as a test piece. Next, the test piece was arranged in a manner that the face on which the cut was made faced downward and the length direction of the test piece was orthogonal to the support plate, in parallel with the distance between the centers being 70 mm, on two support plates of a rigid body composed of a height of 100 mm, a width of 80 mm or more, and a thickness of 10 mm, which were arranged in a manner that the upper end edges were curved with a radius of 5 mm. Then, a pressing plate of a rigid body composed of a height of 60 mm, a width of 80 mm, and a thickness of 10 mm, which was curved with a radius of 5 mm at the top end, was arranged in a manner that the central portion in the thickness direction of the pressing plate coincided with the cut of the test piece. Further, a three-point bending test was performed at a pressing speed of the pressing plate of 200 mm / min from the side opposite to the cut of the test piece. Note that the test piece was pressed with the pressing plate until the test piece broke or the test piece completely entered between the support plates while being separated from the support plates. Next, the fractured surface of the test piece was observed, and the number of foamed particles that were broken and fractured inside was measured by visual inspection. Separately, the number of foamed particles that were peeled at the interface of the fused foamed particles was measured. Next, the proportion of the number of foamed particles that were fractured inside to the total number of the number of foamed particles that were fractured inside and the number of foamed particles that were peeled at the interface was calculated, and this was expressed as a percentage as the fusion rate (%).

[0106] (Determination of tensile strength)

[0107] The determination of the tensile strength was performed in the same manner as described above for the test pieces of 10 mm in thickness of dumbbell-shaped No. 1 type shapes prescribed in JIS K6251 (2010) sampled from six positions of A to F, in accordance with the method for determining the tensile elongation prescribed in JIS K6767 (1999). In this case, after the test pieces taken out were left to stand for 24 hours under conditions of 23°C and a humidity of 50%, a tensile test was performed at a test speed of 500 mm / min, and the maximum point stress in the measurement was taken as the tensile strength. The above measurement was performed three times, and the addition average of the values obtained was used.

[0108] [Table 1]

[0109]

[0110] [Comparative Example]

[0111] The multilayered foamed particles were filled into the mold by the compression filling method (pressure: 0.2 MPa) instead of the crack filling method, and a seat core material was molded by the same method as in Example 1, which was used as a comparative example.

[0112] The average molded body density (Z) of the foamed particle molded body constituting the seat core material was 28 kg / m 3 Further, the molded body density (X) in a test piece (length 50 mm, width 50 mm, thickness 10 mm) cut out from the front side thick wall portion (thickness 90 mm) of the foamed particle molded body of the comparative example was 28 kg / m 3 , the fusion rate was 55%, and the tensile strength was 311 N. On the other hand, the molded body density (Y) in a test piece (length 50 mm, width 50 mm, thickness 10 mm) cut out from the rear side thin wall portion (thickness 30 mm) of the foamed particle molded body of the comparative example was 26 kg / m 3 , the fusion rate was 80%, and the tensile strength was 380 N. Therefore, the density ratio (Y / X) was 0.93, and the density ratio (Y / Z) was 0.93.

[0113] Note that the appearance of the obtained foamed particle molded body did not have local scorching, and the surface of the foamed particle molded body was beautiful.

[0114] Industrial applicability

[0115] The seat core material for a vehicle according to the present application is a seat core material for a vehicle in which cracking and defects are less likely to occur even in a rear side thin wall portion, and thus can be effectively used as a seat core material for various vehicles.

[0116] Explanation of reference numerals

[0117] 1: foamed particle; 10: foamed particle molded body; A, B, C: front portion of foamed particle molded body; D, E, F: rear portion of foamed particle molded body; 30: frame member; 31: front hooking tool; 32: rear hooking tool; 50: mold; 51: female mold; 52: male mold; 53: feeder; 100: seat core material for a vehicle.

Claims

1. A seat core material for vehicles, characterized in that, Contains thermoplastic resin foam particles molded parts. The thermoplastic resin foamed particle molded body is roughly rectangular in shape when viewed from above. The average bulk density Z of the thermoplastic resin foamed particle molded body is 20-50 kg / m³. 3 , The thermoplastic resin foam particle molded body has a rear side thin-walled portion with a thickness of 10-40 mm, which is thinner than the average thickness of the thermoplastic resin foam particle molded body. The ratio of the bulk density Y of the rear thin-walled portion to the average bulk density Z of the thermoplastic resin foam particle molded body, Y / Z, is 1.05 to 3. The portion whose rear side thin-walled portion accounts for more than 8% of the total volume of the foamed particle molded body. The fusion rate of the rear side thin-walled portion of the thermoplastic resin foamed particle molded body is 70% or more.

2. The vehicle seat core material according to claim 1, characterized in that, The thermoplastic resin foamed particle molded body has a front side thick wall portion with a thickness of 80 mm or more on the front side of the thermoplastic resin foamed particle molded body.

3. The vehicle seat core material according to claim 2, characterized in that, The fusion rate of the front thick-walled portion of the thermoplastic resin foamed particle molded body is 40% or more.

4. The vehicle seat core material according to any one of claims 1 to 3, characterized in that, A frame member is embedded in the rear side thin-walled portion of the thermoplastic resin foam particle molded body along the longitudinal dimension of the thermoplastic resin foam particle molded body.

5. The vehicle seat core material according to any one of claims 1 to 3, characterized in that, The foamed particles constituting the thermoplastic resin foamed particle molded body are multilayer foamed particles having a foamed core layer and a coating layer covering the foamed core layer.

6. The vehicle seat core material according to claim 5, characterized in that, The melting point of the coating layer constituting the multilayer foamed particles is 1 to 25°C lower than that of the foamed core layer.

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