JP2016190551A - Interior member for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an interior member for vehicle having a cushion layer which hardly causes volume shrinkage and flattening in a high temperature environment, and can obtain comfortable feeling.SOLUTION: An interior member 1 for vehicle has a stretchable bag body and a cushion layer 3 formed of foamed particles filling the inside of the bag body. The cushion layer 3 is exposed to at least a part of the surface of the interior member 1 for vehicle. A resin constituting the foamed particles is formed of a polyolefin resin. The foamed particles have an average particle size of 2 mm or less, a closed-cell ratio of 70% or more, and an average foam diameter of 100 μm or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a vehicle interior member having a cushion layer.

  A vehicle body member such as an armrest or a door trim comes into contact with a part of a body such as an arm of a passenger. Therefore, it is desired to provide a cushion layer having elasticity in the vehicle interior member. As the cushion layer, a widely used urethane foam resin has been studied. However, since the urethane foam resin is relatively heavy, there is room for improvement in terms of light weight. The urethane foam resin also has room for improvement in terms of touch when touched. Therefore, an interior member for a vehicle having a cushion layer filled with foamed particles made of foamed styrene resin or the like has been proposed (see Patent Document 1).

  The comfort of the cushion filled with foam particles has been confirmed to depend on the stretchability of the fabric and the particle diameter of the foam particles. It has been confirmed that Therefore, a cushion body is proposed in which minute foam particles made of polystyrene resin are filled in a stretchable bag body (see Patent Document 2).

Japanese Unexamined Patent Publication No. 2009-107489 JP 2004-223002 A

  However, a cushion using foamed particles made of polystyrene-based resin has a problem that settling is likely to occur. That is, the polystyrene-based resin expanded particles tend to be in a state of being crushed when compressed, and there is a problem that the expanded particles do not recover to the original shape after compression. This occurs when a load is applied to the cushion and the volume change of the polystyrene resin foam particles is repeated. In particular, polystyrene resins are highly brittle among thermoplastic resins, and when polystyrene resin foam particles are subjected to excessive compression or repeated compression over a long period of time, they tend to cause bubble buckling and rupture, resulting in settling. Prone to occur.

  Moreover, the vehicle interior member is easily exposed to a high temperature environment. Since the glass transition temperature of the polystyrene resin is around 100 ° C., the polystyrene resin foam particles are easily deformed and contracted in a high temperature environment inside the vehicle, and the foam particles contract in the high temperature environment and the volume is reduced. In addition, there is a risk of volumetric shrinkage of the cushion.

  On the other hand, since the polyolefin resin is more ductile than the polystyrene resin and has a higher heat distortion temperature, the expanded particles made of the polyolefin resin are excellent in recoverability at the time of compression, dimensional stability at high temperature, and the like. However, since the foaming of the polyolefin-based resin is completed in a very short time, it is very difficult to control the size of the bubbles in the foaming process, particularly to obtain a fine cell structure. Therefore, the present condition is that the expanded particle which consists of polyolefin resin, a particle diameter is small, and has a fine cell structure is not obtained. Therefore, it is difficult to realize a cushion that is less likely to cause volume shrinkage and settling under a high temperature environment.

  The present invention has been made in view of such a background, and an object of the present invention is to provide an interior member for a vehicle having a cushion layer that is less susceptible to volume shrinkage and settling in a high-temperature environment and that provides a comfortable feel.

One aspect of the present invention is a vehicle interior member having a cushion layer made of a stretchable bag and foamed particles filled in the bag,
At least a part of the cushion layer is exposed on the surface of the vehicle interior member,
The resin constituting the expanded particles is a polyolefin resin,
The average particle diameter of the foamed particles is 2 mm or less,
The foamed particles have a closed cell ratio of 70% or more,
In the vehicle interior member, the foamed particles have an average cell diameter of 100 μm or less.

  The vehicle interior member includes a cushion layer including a stretchable bag body and the fine foam particles having the predetermined average particle diameter filled in the bag body. Further, in the cushion layer, the fine foam particles flow smoothly, and the stretchable bag body can be deformed following the flow of the foam particles. Therefore, the cushion layer can be appropriately deformed with respect to a load from the outside, and exhibits a comfortable feeling. Further, fine foam particles made of a foamed polyolefin resin having a fine and independent cell structure are filled in the bag. Such foamed particles have a small volume reduction rate in a high temperature environment and excellent recoverability upon repeated compression, so that volume shrinkage and settling in a high temperature environment are unlikely to occur, and the above-mentioned good condition even in a high temperature environment It is possible to maintain a good feel and is suitable as a vehicle interior member.

1 is a schematic diagram of a vehicle interior member in Embodiment 1. FIG. The scanning electron micrograph of the resin particle (sample E1) in Example 1. The scanning electron micrograph of the expanded particle (sample E1) in Example 1. The electron micrograph of the cross section of the expanded particle (sample E1) in Example 1. FIG. The figure which shows the DSC curve of the resin particle (sample E1) in Example 1. FIG. The figure which shows the DSC curve of the resin particle (sample E1) in Example 1. FIG. The figure which shows the DSC curve of the expanded particle (sample E1) in Example 1. FIG. The figure which shows a time-dependent change of the volume change rate of the expanded particle (sample E1 and sample C4) in Example 1. FIG.

Next, a preferred embodiment of the vehicle interior member will be described.
As described above, the vehicle interior member has a cushion layer including a stretchable bag body and a foamed particle group made of a large number of polyolefin resin foam particles filled in the bag body.

[Olefin resin]
The resin constituting the expanded particles used in the present invention is a polyolefin resin. Examples of polyolefin resins include polyethylene resins and polypropylene resins. You may use these individually by 1 type or in mixture of 2 or more types. The “main component” means that the polyolefin resin is contained in the polyolefin resin particles in an amount of 50% by mass or more, preferably 75% by mass or more, more preferably 80% by mass or more, and still more preferably. Is preferably 90% by mass or more.

Examples of the polypropylene-based resin include a propylene homopolymer (homopolypropylene), a copolymer with another monomer copolymerizable with propylene, and the like. Other monomers copolymerizable with propylene include, for example, ethylene, 1-butene, isobutylene, 1-pentene, 3-methyl 1-butene, 1-hexene, 3,4-dimethyl-1-butene, 3 Examples include α-olefins having 4 to 10 carbon atoms such as methyl-1-hexene. The copolymer may be a random copolymer or a block copolymer, and may be not only a binary copolymer but also a ternary copolymer. More preferable polypropylene resins are a propylene homopolymer, a copolymer of propylene and ethylene, and a copolymer of propylene, ethylene and butene.
In the case where the polyolefin resin constituting the resin particles used for producing the foamed particles is a propylene homopolymer or a copolymer having a high content ratio of structural units derived from propylene, the liquid nitrogen described later is used. Freezing and pulverization becomes easy, and production of fine resin particles becomes easy. The content of other olefins copolymerizable with propylene in the copolymer is preferably 25% by mass or less, and more preferably 15% by mass or less. These propylene resins can be used alone or in admixture of two or more.

  Examples of the polyethylene resin include a resin containing 50% by mass or more of a structural unit derived from ethylene. Examples of such polyethylene resins include high density polyethylene, low density polyethylene, linear low density polyethylene, ethylene-vinyl acetate copolymer, ethylene-propylene copolymer, and ethylene-propylene-butene-1 copolymer. Examples thereof include an ethylene-butene-1 copolymer, an ethylene-hexene-1 copolymer, an ethylene-4-methylpentene-1 copolymer, and an ethylene-octene-1 copolymer. These can be used individually by 1 type or in mixture of 2 or more types.

  The polyolefin-based resin can contain other thermoplastic resin components and / or elastomer components and the like within a range that does not impair the effects of the present invention. Other thermoplastic resin components and elastomer components include, for example, vinyl acetate resin, thermoplastic polyester resin, acrylic ester resin, methacrylic ester resin, styrene resin, polyamide resin, fluororesin, ethylene-propylene rubber, ethylene- Examples include propylene-diene rubber, ethylene-acrylic rubber, chlorinated polyethylene rubber, and chlorosulfonated polyethylene rubber.

  From the viewpoint of being particularly excellent in the balance between mechanical strength and heat resistance, and from the viewpoint of facilitating the production of fine resin particles, the polyolefin resin is preferably a polypropylene resin.

[Average particle diameter of expanded particles]
The average particle diameter of the expanded particles is 2 mm or less. When the average particle diameter exceeds 2 mm, the good feel of the cushion layer may be impaired. In addition, when foamed particles flow in the cushion layer, there is a risk that unpleasant noise may be generated when the particles rub. The average particle diameter of the expanded particles is preferably 1.6 mm or less, and more preferably 1.3 mm or less. Further, from the viewpoint of preventing the elastic bag body from slipping through, the average particle diameter of the foamed particles is preferably 0.05 mm or more, and more preferably 0.1 mm or more. The average particle diameter of the expanded particles is an arithmetic average value of the diameters when the particles are completely spherical. On the other hand, when the expanded particle is not a perfect sphere such as an elliptical sphere, the average value of the maximum diameter (major axis) is the average particle diameter.

[Ratio of major axis to minor axis of expanded particles]
The ratio of the major axis to the minor axis (major axis / minor axis) of the expanded particles is preferably 1 to 1.3, more preferably 1 to 1.1. When the ratio of the major axis to the minor axis of the foam particles is 1 to 1.3, the flow of the foam particles in the cushion layer becomes smoother and the feel of the cushion layer becomes better.

[Bubble structure]
The closed cell ratio of the polyolefin resin expanded particles is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. As described above, when the closed cell ratio is high, even foamed particles having a small particle diameter are excellent in recoverability during repeated compression. The closed cell ratio is a ratio of the volume of closed cells to the volume of all the bubbles in the expanded particles, and is measured using an air comparison hydrometer based on ASTM-D2856-70.

[Average bubble diameter]
The average cell diameter of the expanded particles is 100 μm or less. In this case, the recoverability at the time of repeated compression is further improved. From the above viewpoint, the average cell diameter of the expanded particles is more preferably 80 μm or less. When the average cell diameter is within the range and the closed cell ratio is high, even polyolefin resin foamed particles having a small particle diameter are excellent in recoverability upon repeated compression. The average cell diameter of the expanded particles can be obtained by dividing the diameter (major axis) of the expanded particles by the number of cells.

[Number of bubbles]
The number of bubbles crossing a straight line passing through the center of the expanded particle along the major axis direction of the polyolefin resin expanded particle is preferably 10 or more, more preferably 15 or more. On the other hand, the upper limit of the number of bubbles is approximately 100, preferably 70. When the number of the bubbles is within the above range, the recoverability during repeated compression is further improved. In addition, when the polyolefin resin expanded particles are spherical (when the major axis and the minor axis are equal), the straight line passing through the center of the expanded particle along the major axis direction is particularly limited as long as the straight line passes through the center of the expanded particle. Not.

[Apparent density]
The apparent density of the expanded particles is preferably 10 to 300 g / L. In this case, it is possible to more easily provide a vehicle interior member that is excellent in light weight and excellent in shock-absorbing properties. The apparent density of the expanded particles is more preferably 15 to 100 g / L, and further preferably 20 to 100 g / L.

[Temperature and heat quantity of melting peak of expanded particles]
The expanded particle is a melting peak (inherent peak) derived from the crystal structure inherent in the polyolefin resin in the DSC curve when the expanded particle is heated from 20 ° C. to 200 ° C. at a temperature increase rate of 10 ° C./min. And a crystal structure showing two melting peaks, a melting peak (high temperature peak) located on the high temperature side of the intrinsic peak. In this case, as described above, it is easy to obtain fine expanded particles having a small average cell diameter and a high closed cell rate. In addition, a high temperature peak originates in the crystal | crystallization formed by performing an isothermal crystallization operation, when expanding the above-mentioned resin particle and obtaining a foamed particle.

  The foamed particles can be obtained, for example, by using resin particles described later having a specific crystal structure, and foaming the resin particles under conditions where a high temperature peak is formed. This high temperature peak is presumed to be caused by the formation of a microlamella having a purer crystal structure. As a result, it is considered that even if the particle size is small, it is possible to obtain expanded particles having a good fine cell structure.

When the polyolefin-based resin constituting the expanded particles is a polypropylene-based resin, the temperature (T) of the high-temperature peak of the two melting peaks described above is the amount of heat (ΔH) of the high-temperature peak and the temperature of the intrinsic peak (Tm). And the following formula (1). Foamed particles having a crystal structure satisfying such a relationship can form a particularly fine microbubble structure with a large number of bubbles and a high closed cell ratio even if the particle size is small.
T ≧ Tm + 19−0.27 × ΔH (1)

  As described above, the polyolefin resin foamed particles having a fine and independent cell structure can be obtained by foaming predetermined polyolefin resin particles (hereinafter referred to as “resin particles” as appropriate). Hereinafter, the resin particles used for producing the foamed particles will be described in detail.

[Crystal structure of resin particles]
As the polyolefin resin particles, the melting peak in the DSC curve obtained by differential scanning calorimetry (DSC) during the first heating in which the resin particles are heated from 20 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min. The top temperature (T ₁ ) is cooled from 200 ° C. to 20 ° C. at a rate of temperature decrease of 10 ° C./min following the first heating, and further from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min. It is preferable to use resin particles having a crystal structure that is 1.5 ° C. higher than the peak temperature (T ₂ ) of the melting peak in the DSC curve obtained by differential scanning calorimetry during the second heating. In other words, the expanded particles are preferably formed by expanding polyolefin resin particles that satisfy the relationship of the following formula (I).
T ₁ −T ₂ ≧ 1.5 (I)
(However, T ₁ is the melting in the DSC curve obtained by differential scanning calorimetry (DSC) during the first heating in which the polyolefin resin particles are heated from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min. T ₂ is the peak apex temperature, T ₂ is cooled from 200 ° C. to 20 ° C. at a rate of temperature decrease of 10 ° C./min following the first heating, and further 20 ° C. at a rate of temperature increase of 10 ° C./min. It is the peak temperature of the melting peak in the DSC curve at the time of the second heating which is heated from 200 to 200 ° C.)
By foaming such resin particles, it is possible to obtain fine foam particles having the above-mentioned desired cell structure. The peak temperature (T ₁ ) of the melting peak in the DSC curve during the first heating is referred to as the first temperature (T ₁ ), and the peak temperature of the melting peak in the DSC curve during the second heating. the (T _2), hereinafter referred to as a second temperature (T _2).

The first temperature (T ₁ ) is a melting temperature derived from melting of the crystal structure of the resin particles (a crystal structure generated by isothermal crystallization described later). On the other hand, the second temperature (T ₂ ) is a melting temperature derived from melting of the crystal structure of the polyolefin-based resin (crystal structure originally possessed by the polyolefin-based resin). The crystal structure inherent to the polyolefin resin is melted by heat treatment described later, and the melted polyolefin resin is crystallized isothermally to generate the crystal structure of the resin particles. Note that first temperature (T ₁₎ and the second temperature (T ₂₎ is the peak temperature of the melting peak is determined in accordance with JIS K7121 (1987), a melting peak at first heating above Is present, the melting point is the vertex temperature of the melting peak with the highest vertex height, based on the baseline on the high temperature side.

In the resin particles, the first temperature (T ₁ ) is preferably higher by 1.5 ° C. or higher and more preferably higher by 2 ° C. or higher than the second temperature (T ₂ ) as described above. The upper limit of the difference (T ₁ −T ₂ ) between the first temperature (T ₁ ) and the second temperature (T ₂ ) is about 10 ° C., preferably 8 ° C. By foaming the resin particles having such a crystal structure, it is possible to obtain the fine foamed particles having the above-described favorable fine cell structure.

[Heat treatment]
The resin particles having the above-mentioned characteristic crystal structure are produced by heat-treating pre-resin particles made of polyolefin resin. The heat treatment temperature is preferably 12 to 25 ° C. higher than the melting point of the pre-resin particles, and more preferably 15 to 22 ° C. higher. Thus, first temperature (T ₁₎ is a crystalline structure resin particles having a melting temperature of the second temperature (T ₂₎ higher 1.5 ° C. or more with respect to such first temperature (T ₁₎ Can be generated. The pre-resin particles are polyolefin resin particles before the above heat treatment. The pre-resin particles can be produced by, for example, using a commercially available polyolefin resin pellet to produce a strand-shaped molded body and cutting or pulverizing the molded body. The pre-resin particles have a crystal structure that the polyolefin resin particles originally have, and have a melting temperature of the second temperature (T ₂ ) described above.

The particle weight of the resin particles is preferably 2000 μg or less, more preferably 200 μg or less, further preferably 100 μg or less, and even more preferably 50 μg or less. When the particle weight of the resin particles is within the above range, fine foamed particles can be obtained. And since the resin particle has the above-mentioned specific crystal structure, even if the particle weight is small, it is possible to produce foamed particles having a good fine cell structure. The lower limit of the weight of the resin particles is about 5 × 10 ⁻⁴ μg, preferably 0.2 μg, and more preferably 0.5 μg.

[Shape of resin particles]
The ratio of the major axis to the minor axis (major axis / minor axis) of the resin particles is preferably 1 to 1.3. When the ratio of the major axis to the minor axis (major axis / minor axis) of the resin particles is 1 to 1.3, the ratio of the major axis to the minor axis (eg, major axis / minor axis) is 1 to 1.3. ) Foamed particles can be obtained. In addition, the distribution of bubbles in the expanded particles can be made more uniform, and the bubble diameter can be made more uniform.

  Foamed particles can be obtained by using the above-mentioned resin particles having a specific crystal structure and foaming the resin particles under conditions where a high temperature peak is formed.

[Method for producing foamed particles]
The method for producing expanded particles includes a step (A) of preparing pre-resin particles made of polyolefin resin, a step (B) of preparing resin particles by heat-treating the pre-resin particles, and a step (C) of foaming the resin particles. Including.

(Process (A))
In the step (A), pre-resin particles made of a polyolefin resin are prepared. The pre-resin particles can be produced, for example, as follows. The polyolefin resin pellets and predetermined additives are put into an extruder such as a ruder to produce a strand-like extrudate of the polyolefin resin. The produced strand-shaped extrudate is cut, and if necessary, the cut strand-like extrudate is further pulverized to produce polyolefin resin pre-resin particles. Examples of the pulverizer used for pulverizing the cut strand-shaped extrudate include a ball mill, a bead mill, a colloid mill, a conical mill, a disk mill, an edge mill, a milling mill, a hammer mill, a mortar, a pellet mill, a VSI mill, a wheelie mill, and a water wheel. (Pulverizer), roller mill, jet mill and the like. In addition, in order to make it easy to grind | pulverize the cut | disconnected strand shaped extrudate, you may immerse the cut | disconnected strand shaped extrudate in liquid nitrogen etc. before cooling, and may cool. Moreover, in order to make the size of the pre-resin particles in a specific range, the pre-resin particles may be classified using a classifier.

(Process (B))
In the step (B), the pre-resin particles are heat-treated as follows, for example, to produce polyolefin resin particles. Specifically, first, the pre-resin particles are put into a container containing a medium such as water, and the pre-resin particles are heat-treated while stirring the pre-resin particles in the medium. The temperature of the heat treatment is as described above. This heat treatment is preferably performed by holding at the above heat treatment temperature for 1 to 120 minutes, more preferably 15 to 60 minutes. The polyolefin resin particles produced by the step (B) are resin particles used for foaming.

(Process (C))
In the step (C), for example, the resin particles are foamed as follows. Specifically, first, a mixture containing a foaming agent, resin particles, and an aqueous medium to which a dispersant is added is put into a sealed container. Next, the mixture is impregnated with the foaming agent by heating the mixture to a temperature equal to or higher than the softening point of the resin particles in an airtight container, and is isothermally crystallized by holding in the above temperature range to show a high temperature peak. A crystal structure is formed. Then, by releasing the resin particles and the aqueous medium to the low pressure region, the resin particles are expanded to obtain expanded particles.

As described above, the expanded particles obtained by expanding the resin particles described above have an olefin-based resin in the DSC curve when the expanded particles are heated from 20 ° C. to 200 ° C. at a temperature increase rate of 10 ° C./min. It is preferable to have a crystal structure showing two melting peaks, a melting peak (inherent peak) derived from the inherent crystal structure and a melting peak (high temperature peak) located on the high temperature side of the intrinsic peak. In this case, as described above, it becomes easy to obtain fine foamed particles made of a foamed olefin resin having a large number of bubbles and a high closed cell ratio. The high temperature peak is derived from crystals formed by performing an isothermal crystallization operation when foaming the above-described resin particles to obtain expanded particles. Specifically, in the isothermal crystallization operation, when heating the resin particles are dispersed in a dispersion medium in a closed vessel, the resin particles melting point (hereinafter also referred to as Tm _A) 15 ° C. lower temperatures or higher than, the resin The temperature rise is stopped at a temperature (hereinafter also referred to as Ta) that is less than the melting end temperature (hereinafter also referred to as Te) at which the particles are completely melted, and the dispersion medium in which the resin particles are dispersed is sufficient at the temperature Ta. Hold time, preferably about 10-60 minutes. Thereby, the expanded particle which has a high temperature peak can be obtained. Thereafter, the temperature is adjusted to a temperature in the range of (Tm _A −5 ° C.) to (Te + 5 ° C.) (hereinafter also referred to as Tb), and the resin particles are discharged from the container to the low pressure region at that temperature to foam the resin particles. .
The formation of the high-temperature peak of the expanded particles and the magnitude of the heat quantity of the high-temperature peak are mainly due to the above-described temperature Ta with respect to the resin particles when the expanded particles are produced, the holding time at the temperature Ta, and the above-mentioned temperature Tb. It depends on the heating rate within the range of (Tm _A -15 ° C.) to (Te + 5 ° C.). The amount of heat at the high temperature peak of the expanded particles is such that the lower the temperature Ta or the temperature Tb within the above-mentioned temperature ranges, the longer the holding time in the range of (Tm _A -15 ° C.) or more and less than Te ° C., and It shows a tendency to increase as the rate of temperature increase in the range of (Tm _A -15 ° C.) or higher and lower than Te ° C. is slower. In addition, a temperature increase rate is normally selected within the range of 0.5-5 degreeC / min. On the other hand, the amount of heat at the high temperature peak of the expanded particles is such that the higher the temperature Ta or the temperature Tb is within the above temperature ranges, the shorter the holding time in the range of (Tm _A -15 ° C.) or more and less than Te ° C. And, the higher the temperature rising rate in the range of (Tm _A -15 ° C.) or higher and lower than Te ° C., the lower the temperature rising rate in the range of Te ° C. to (Te + 5 ° C.).

  Examples of the foaming agent include inorganic physical foaming agents such as nitrogen, oxygen, air, carbon dioxide, and water. In addition, water is generally used as the aqueous dispersion medium, but any solvent that does not dissolve the resin particles may be used, and it is not particularly limited to water. Examples of the dispersion medium other than water include ethylene glycol, glycerin, methanol, ethanol, and the like. Furthermore, examples of the dispersant include aluminum oxide and aluminosilicate. The pressure in the sealed container, that is, the pressure in the space in the container (gauge pressure) is, for example, 0.6 to 6.0 MPa.

[Bag body]
A bag body will not be specifically limited if it is a bag-shaped thing comprised with the fabric which has a stretching property. By using a stretchable bag body, an automotive interior member having excellent cushioning properties is obtained. Further, since the cushion layer is formed by filling the bag body with the foamed particles, in the cushion layer, the fine foam particles smoothly flow and the stretchable bag body flows into the foam particles. It can follow and deform. Further, at least a part of the cushion layer is exposed from the surface of the vehicle interior member. However, even in a high temperature environment, volume shrinkage and settling are unlikely to occur, and the above-described favorable condition is obtained even in a high temperature environment. The touch can be maintained, and the vehicle interior member is suitable.

Example 1
Next, examples of the vehicle interior member will be described. As shown in FIG. 1, the vehicle interior member 1 of this example is an example of a door trim. The vehicle interior member 1 of this example has a main body 2 and a cushion layer 3 embedded in the main body 2, and at least a part of the cushion layer 3 is exposed on the surface of the vehicle interior member 1. . Hereinafter, the vehicle interior member of this example will be described in detail.

  The cushion layer 3 is composed of a stretchable bag and a group of expanded particles composed of a large number of expanded particles filled in the bag. The bag body is a bag-like sewing product made of a spandex cloth material made of 15% by mass of urethane-based resin and 85% by mass of nylon-based resin. The expanded particles are made of a polyolefin resin. In this example, a plurality of vehicle interior members were produced using different foamed particles (Sample E1 to Sample E4 and Sample C1 to Sample C4). First, as a representative example, a method for manufacturing an interior member for a vehicle using the expanded particles of the sample E1 will be described in detail below.

  Specifically, first, a pellet of an ethylene-propylene random copolymer (polypropylene resin; ethylene content 3 mass%) having a melting point of 142 ° C. and a melt mass flow rate (MFR) of 5 g / 10 minutes, Zinc borate having an added amount of 500 ppm relative to the mass of the pellets is charged into an extruder (inner diameter 40 mm) set at a temperature of 200 ° C., melt-kneaded, and the melt-kneaded product is extruded to have a diameter of 1.25 mm. A strand-like extrudate was produced. Then, the strand-like extrudate was cut into a length (length 2.5 mm) so that the length / diameter value was 2, and a mini-pellet was produced. The average mass of the mini pellets was 1.0 mg / piece. The MFR of the polypropylene resin in the present specification is a value measured with a condition code M (temperature 230 ° C., load 2.16 kg) based on JIS K7210 (1999). As a measuring device, a melt indexer (for example, model L203 manufactured by Takara Kogyo Co., Ltd.) was used.

  Next, after exposing the mini-pellets to liquid nitrogen, the mini-pellets are pulverized by passing them through a sufficiently cooled pulverizer (trade name: SILAL MILL SP-420, manufactured by Seishin Enterprise Co., Ltd.). Obtained. The grinding conditions were a clearance of 0.5 mm, a rotational speed of 5000 rpm, and a throughput of 7 kg / hour. Then, it was divided into a 580 μm-classified sieve (hereinafter sometimes referred to as “ON”) and a sieve below (sometimes referred to as “PASS”). The average weight of the “ON” pre-resin particles was 180 μg, and the average weight of the “PASS” pre-resin particles was 30 μg.

  600 g of “ON” pre-resin particles, 3000 cc of water, 6 g of kaolin, 0.6 g of surfactant (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Neogen S20), and 0.15 g of aluminum sulfate While being stirred at a stirring speed of 200 rpm, the temperature was raised to 150 ° C. at a temperature rising rate of 2 to 3 ° C./min, and kept at this temperature of 150 ° C. for 5 minutes. Thereafter, the temperature was further raised from 150 ° C. to 5 ° C. and held for 5 minutes. When the temperature reached 165 ° C. (23 ° C. higher than the melting point), the temperature was held at 165 ° C. for 1 hour. Then, it stood to cool, and when the temperature of the contents of the autoclave reached 60 ° C., the contents were taken out. The contents were dried for 24 hours at a temperature of 60 ° C. using a dryer to obtain resin particles.

  Next, 300 g of resin particles, 3700 cc of water, 6 g of kaolin, 0.6 g of a surfactant (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Neogen S20), 0.15 g of aluminum sulfate, and 50 g of A foaming agent (dry ice) is put into a 5 L autoclave and heated to a temperature of 145 ° C. (5 ° C. lower than the foaming temperature) at a rate of 2-3 ° C./min while stirring at a stirring speed of 200 rpm. The temperature was held at 145 ° C. for 15 minutes. Thereafter, the temperature was raised to 150 ° C. (foaming temperature), and the temperature was held at 150 ° C. for 15 minutes. After holding for 15 minutes, one end of the autoclave was released, and the resin particles were foamed by releasing the contents in the autoclave into the atmosphere to obtain expanded particles (sample E1).

  Next, the foamed particles of Sample E1 were filled into a stretchable bag. And the vehicle interior member 1 was constructed | assembled by assembling | attaching the bag body filled with foamed particle to a main-body part (refer FIG. 1).

  Further, in this example, foamed particles (sample E2 to sample E4 and sample C1 to sample C4) are further produced by a manufacturing method different from that of sample E1, and each foamed particle is used for a vehicle similar to the above example. An interior member was produced.

Sample E2 is expanded particles produced by the same method as Sample E1, except that “PASS” pre-resin particles were used instead of “ON” pre-resin particles.
Sample E3 was prepared in the same manner as Sample E1, except that “PASS” pre-resin particles were used instead of “ON” pre-resin particles and the foaming temperature was changed from 150 ° C. to 148 ° C. Expanded foam particles.

  Sample E4 is expanded particles produced using homopolypropylene instead of the ethylene-propylene random copolymer pellets. Sample E4 uses “PASS” pre-resin particles instead of “ON” pre-resin particles, changes the heat treatment temperature to 180 ° C., changes the foaming temperature to 169 ° C., and changes the amount of foaming agent to 40 g. Except for the points described above, the sample was manufactured in the same manner as the sample E1.

Sample C1 is the same as Sample E1, except that the mini pellets are used as resin particles as they are, heat treatment is not performed, the mini pellets are foamed, and the foaming temperature is changed from 150 ° C. to 148 ° C. It is the expanded particle produced by the method.
Sample C2 is expanded particles produced by the same method as Sample E1, except that the mini pellets are used as resin particles as they are, heat treatment is not performed, and the mini pellets are expanded.
Sample C3 was obtained by using “PASS” pre-resin particles instead of “ON” pre-resin particles, and using the pre-resin particles as resin particles as they were (that is, pre-resin particles were not heat-treated). Except that the foaming temperature was changed from 150 ° C. to 148 ° C., the foamed particles were produced by the same method as Sample E1.
Sample C4 is expanded particles produced by expanding commercially available expandable polystyrene resin particles (manufactured by JSP Co., Ltd., model number: JK550).

In addition, the scanning electron micrograph of the resin particle used in the sample E1 among the resin particles produced in this example is shown in FIG. Moreover, the scanning electron micrograph of the expanded particle of the sample E1 is shown in FIG. 3, and the electron micrograph of the cross section of the expanded particle of the sample E1 is shown in FIG. Furthermore, the DSC curve of the resin particle used for preparation of the sample E1 is shown in FIGS. FIG. 5 is a DSC curve when heated from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min, and T _{1 in} the figure is the temperature of the melting peak. Further, FIG. 6 shows that after heating from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min, cooling from 200 ° C. to 20 ° C. at a rate of temperature decrease of 10 ° C./min, further increasing the temperature by 10 ° C./min It is a DSC curve when heated from 20 ° C. to 200 ° C. at a rate, and T _{2 in} the figure is the temperature of the melting peak. Moreover, the DSC curve of the expanded particle of sample E1 is shown in FIG. FIG. 7 is a DSC curve when heated from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min. T in the figure is the temperature of the high temperature peak of the two melting peaks, and Tm is the temperature of the intrinsic peak. Further, in the DSC curve, a point corresponding to the melting end temperature of the high temperature peak and a point corresponding to 80 ° C. are connected by a straight line, and between the temperature of the intrinsic peak (Tm) and the temperature of the high temperature peak (T) from the straight line. The straight line L ₁ perpendicular to the horizontal axis of the temperature is drawn in the valley (T _h ), and the heat quantity ΔH (J / g) of the melting peak on the high temperature side is calculated from the area surrounded by the straight line L ₁ and the base line L _2. Calculated.

[Evaluation results]
The manufacturing conditions and physical properties of each resin particle produced in this example and the manufacturing conditions and physical properties of the expanded particles are shown in Table 1 described later. Note that “present” in the frozen pulverization item in the table indicates that the cooled mini-pellet was pulverized, and “absent” indicates that the cooled mini-pellet was not pulverized. The measurement method of each evaluation item in the table is shown below.

(Measurement of melting peak temperature and melting peak calorie)
Differential scanning calorimetry (DSC) was performed on each resin particle and foamed particle. The measuring apparatus used is a heat flux differential scanning calorimeter (manufactured by TA Instruments Inc., model number: DSCQ1000).

In the case of resin particles, approximately 1 to 3 mg of a sample (resin particles) is placed in a measuring device and heated from 20 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min based on JIS K7121 (1987) ( 1st heating), then, further cool from 200 ° C. to 20 ° C. at a temperature decreasing rate of 10 ° C./min, and further heat from 20 ° C. to 200 ° C. at the temperature rising rate of 10 ° C./min (second heating). DSC curves were obtained for each. This measurement was performed five times using different samples. At this time, the arithmetic average value of the peak temperature of the melting peak at the first heating was T ₁ (° C.), and the arithmetic average value of the peak temperature of the melting peak at the second heating was T ₂ (° C.). The results are shown in Table 1.

  In the case of expanded particles, approximately 1 to 3 mg of sample (expanded particles) is placed in a measuring device, and differential scanning calorimetry is performed when heated from a temperature of 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min. DSC curve was obtained. This measurement was performed five times using different samples. At this time, the arithmetic average value of the peak temperature of the melting peak (inherent peak) on the low temperature side was Tm (° C.), and the arithmetic average value of the peak temperature of the melting peak (high temperature peak) on the high temperature side was T (° C.). Further, in each DSC curve, a point corresponding to the melting end temperature of the high temperature peak and a point corresponding to 80 ° C. are connected by a straight line, and between the temperature of the intrinsic peak (Tm) and the temperature of the high temperature peak (T) from the straight line. A straight line perpendicular to the horizontal axis of the temperature is drawn in the valley of the temperature, and the calorific value of the melting peak on the high temperature side is calculated from the area surrounded by the straight line and the baseline, and ΔH (J / g) is calculated from the arithmetic average thereof. Obtained. The results are shown in Table 1.

(SEM observation)
Using a scanning electron microscope, the foamed particles of each sample were observed, and the major axis and the ratio of the major axis to the minor axis (major axis / minor axis) were examined. Fifty expanded particles were observed for each sample. Then, the average value of the major axis of the expanded particles and the ratio of the major axis to the minor axis (major axis / minor axis) was determined. The results are shown in Table 1. Further, the foamed particles were cut into approximately two equal parts along the major axis direction of the foamed particles, and the cross section of the foamed particles was observed using a scanning electron microscope. And the number of the air bubbles which cross | intersect the virtual straight line which passes along the center of a foamed particle along the major axis direction of a foamed particle was investigated. Fifty expanded particles were observed for each sample, and the average number of measured bubbles was calculated. The results are shown in Table 1. Further, the average cell diameter was determined by dividing the major axis of the expanded particles by the number of cells. The results are shown in Table 1.

(Apparent density)
About each sample, the weight W (g) of the expanded particle group of about 500 cm ³ which was allowed to stand for 2 days under the conditions of 23 ° C., 50% relative humidity and 1 atm was measured. Next, the foamed particle group was submerged in a 1 L graduated cylinder containing 300 cc of 23 ° C. water using a wire mesh, and the volume V (cm ³ ) of the foamed particle group was determined from the scale of the rising water level. Then, the apparent density of the expanded particles was calculated by converting the value (W / V) obtained by dividing the weight W of the expanded particle group by the volume V into [g / L]. The results are shown in Table 1.

(Closed cell rate)
Condition adjustment was performed by leaving the foamed particles of each sample in a temperature-controlled room under conditions of 23 ° C., 50% relative humidity and 1 atm for 2 days. Next, in this temperature-controlled room, in accordance with the procedure C described in ASTM-D2856-70, the true volume of the expanded particles (the volume of the resin constituting the expanded particles and the closed cell portion in the expanded particles The value Vx of the total volume of bubbles was measured. An air comparison type hydrometer 930 manufactured by Toshiba Beckman Co., Ltd. was used for the measurement of the true volume Vx. Next, the closed cell ratio was calculated by the following formula (2), and the average value of the five measurement results was obtained. The results are shown in Table 1.
Closed cell ratio (%) = (Vx−W / ρ) × 100 / (Va−W / ρ) (2)
Vx: True volume of expanded particles measured by the above method (cm ³ )
Va: Apparent volume of expanded particles (cm ³ )
W: Weight of the foam particle measurement sample (g)
ρ: Density of resin constituting expanded particles (g / cm ³ )

(Feel test at room temperature)
Using a spandex cloth material made of 15% by weight urethane resin and 85% by weight nylon resin, a bag-like sewn product (capacity: 1 L) having a size of 10 cm × 20 cm was prepared. A group of expanded particles composed of expanded particles of each sample having a volume of about 1.5 L was encapsulated. The bag-like sewn product enclosing the foam particles was touched on the monitor, and the texture was examined. The case where the texture was good was evaluated as “A”, and the case where the texture was bad was evaluated as “B”. The results are shown in Table 1.

(Compression recovery rate)
Compressed recovery rate by adding foamed particles to a knitted fabric (100cm ² × 100mm thick) knitted with Lycra T400 manufactured by Toray Operontex Co., Ltd. I investigated. Specifically, first, the foam particle group was inserted into a rigid container having an opening area of 100 cm ² . At this time, a point where the aluminum plate was dropped by dropping an aluminum plate having a thickness of 100 cm ² × 10 mm on the upper part of the foamed particle group in the container was used as an initial marked line. Next, after the aluminum plate is taken out of the container, a rigid jig having a cross-sectional area (pressing area) of 25 cm ^{2 with} the tip end filled with a radius of curvature r = 5 mm is used as an initial mark of the container in which the foam particles are inserted. Pressing was repeatedly performed so as to enter 50 mm (50% compression in appearance) from the line. The pressing speed was adjusted from 0.1 Hz to 1 Hz. Then, after repeating the pressing 10,000 times, the rigid jig was removed, and a point where the aluminum plate having a thickness of 100 cm ² × 10 mm was dropped onto the upper part of the foamed particle group in the container and stopped was used as a post-test marked line. The compression recovery rate was calculated by a calculation method of compression recovery rate (%) = (1- (initial marked line−post-test marked line)) × 100. The results are shown in Table 1. In the table, the value of each compression recovery rate is shown. When the value exceeds 95%, the result is shown as “95 <”. The compression recovery rate of the expanded particle group is preferably 90% or more, and preferably 95% or more. In this case, the settling of the cushion layer can be more reliably suppressed.

(Volume reduction rate)
1 L of each expanded particle group was allowed to stand in a hot-air circulating oven at a temperature of 100 ° C., and the volume change with time was measured. As a representative example, FIG. 8 shows changes with time in the volume change rates of the sample E1 and the sample C4. And the volume reduction | decrease rate (%) when the expanded particle group which consists of the expanded particle of each sample was exposed for 6 hours on the conditions of the temperature of 100 degreeC was measured. The results are shown in Table 1. In the table, the value of each volume reduction rate is shown. When the value was less than 5%, the result was described as “<5”. The volume reduction rate is preferably 10% or less. In this case, the volume reduction of the expanded particle group in the vehicle assumed to be exposed to a high temperature environment up to nearly 100 ° C. is more reliably suppressed. Therefore, it is possible to more reliably maintain a good feel of the vehicle interior member.

  As is clear from the comparison of the evaluation results of the samples, the foamed particles (sample E1 to sample E4) made of polyolefin resin having a closed cell ratio of 70% or more and an average cell diameter of 100 μm or less have an average particle diameter. Since it is 2 mm or less, it is excellent in feel, shrinkage hardly occurs in a high temperature environment, and since the compression recovery rate is high, it is difficult to cause settling. Therefore, in the vehicle interior member 1 having the cushion layer 3 in which the foamed particles are filled in the stretchable bag body, the volume shrinkage of the cushion layer 3 in a high-temperature environment hardly occurs, and the cushion layer 3 is also loosened. It is difficult (see FIG. 1). Therefore, even under a high temperature environment, it is possible to maintain a good feel (feel) for a long period of time. In this example, an example of a door trim has been described. However, the same applies to other vehicle interior members such as an armrest having a cushion layer having the same configuration as that of this example.

  As mentioned above, although the Example of this invention was described in detail, this invention is not limited to the said Example, A various change is possible within the range which does not impair the meaning of this invention.

DESCRIPTION OF SYMBOLS 1 Interior member for vehicles 2 Main body 3 Cushion layer

Claims (7)

An interior member for a vehicle having a cushion layer made of a stretchable bag and foamed particles filled in the bag,
At least a part of the cushion layer is exposed on the surface of the vehicle interior member,
The resin constituting the expanded particles is a polyolefin resin,
The average particle diameter of the foamed particles is 2 mm or less,
The foamed particles have a closed cell ratio of 70% or more,
The vehicle interior member, wherein the foamed particles have an average cell diameter of 100 µm or less.   2. The vehicle interior member according to claim 1, wherein the apparent density of the expanded particles is 10 to 300 g / L.   The vehicle interior member according to claim 1 or 2, wherein the polyolefin resin is a polypropylene resin. The foamed particles are obtained by foaming polyolefin resin particles,
The above-mentioned polyolefin resin particles are the peak temperature (T ₁ ) of the melting peak at the first heating in the DSC curve obtained by heating the polyolefin resin particles from 20 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min. However, the DSC curve obtained by cooling from 200 ° C. to 20 ° C. at a rate of temperature decrease of 10 ° C./min following the first heating, and further heating from 20 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min. 4. The vehicle according to claim 1, wherein the resin particles are polyolefin-based resin particles that are 1.5 ° C. or more higher than the peak temperature (T ₂ ) of the melting peak at the time of second heating. Interior material.   The vehicle interior member according to any one of claims 1 to 4, wherein a volume reduction rate when the expanded particles are exposed to a temperature condition of 100 ° C for 6 hours is 10% or less.   The vehicle interior member according to any one of claims 1 to 5, wherein a compression recovery rate of the foamed particles is 90% or more.   The vehicle interior member according to any one of claims 1 to 6, wherein the vehicle interior member is an armrest or a door trim.