JP2007045979A - Interior material for automobile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interior material for automobiles that satisfies all requirements such as weight saving, mechanical properties, acoustic absorption and reduction in costs, by imparting the acoustic absorption to a polyolefin expansion molded object excellent in the mechanical properties, heat resistance, chemical resistance and the weight saving, using a simple and inexpensive manufacturing method. <P>SOLUTION: This polyolefin resin expansion object the air flow resistance of which at 0.02 m thickness is >3,000 N×s/m<SP>3</SP>and ≤50,000 N×s/m<SP>3</SP>is applied to the interior material for the automobile. The expansion object is superior in the mechanical properties, the acoustic absorption and the reduction in cost compatibly. Particularly, the expansion object is suitable for an impact absorbing material for use in lower limb protection of a crew, a side collision pad material for use in crew protection upon the side collision and the impact absorbing material in an inside pillar. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automobile interior material made of a polyolefin resin foam, and further relates to an automobile interior material made of a polyolefin resin foam molded article that achieves both shock absorption and in-car quietness.

  In automobiles, in order to protect the occupant from impacts, the foamed resin molded body is used inside the bumpers, pillars, and doors to minimize damage to the passenger compartment. In addition to providing a shock absorbing material (Patent Document 1) as a material, recently a knee pad for the purpose of protecting an occupant's leg or a tibia pad for absorbing an impact from the sole for the purpose of protecting the lower limbs ( Patent document 2) is being widely applied.

  In particular, the interior material applied to the passenger compartment side is being widely used in the form of foamed polystyrene, foamed polypropylene, and foamed polyethylene that are easy to recycle, lightweight, and excellent in impact absorption performance. Recently, among these foamed resins, in order to reduce heat resistance and VOC, foamed polypropylene and foamed polyethylene are suitable.

  However, these foamed resins are excellent in light weight and shock absorption properties, but the material itself does not have sound absorption performance, which is an important factor in the interior silence. The sound-absorbing material and a sound-insulating carpet laminated with a sound-insulating film were used in combination. Therefore, in such a case, the weight of the sound insulating material cannot be reduced in order to maintain the quietness in the vehicle, and it has been difficult to reduce the weight. Furthermore, in order to improve sound absorption performance in some car models, high performance, that is, expensive felt is necessary, and because it is inevitable to apply laminated products, the overall cost increases due to the increase in assembly man-hours or the number of parts. Down was considered difficult.

  On the other hand, there is an example in which sound-absorbing foamed plastic is applied to a car floor raising material (Patent Document 3). Here, what has provided through-holes or bottomed holes for imparting sound absorbing properties to foamed plastics by devising the mold or post-processing has been introduced. In this case, it is particularly necessary to increase the cost due to the complexity of the mold to provide a large number of sound absorbing holes in the product, or to perform processing to provide sound absorbing holes in post-processing on a product that does not absorb sound. As a result, there was a problem of increased processing costs.

In the field of lower limb protection materials, a material that achieves both shock absorption and sound absorption is being developed (Patent Document 4). According to the present invention, a recess is provided in a conventional foam having no sound absorbing performance, and a sound absorbing material such as felt or sponge is packed in the recess (sound absorbing chamber). Since this is a method of combining two or more different materials, the number of parts increases, the number of man-hours and the processing cost increase, so that the problems of both cost reduction and sound absorption performance have not been solved.
Japanese Patent Laid-Open No. 11-286217 Japanese Patent Laid-Open No. 2005-67481 JP 2003-335893 A JP 2005-81958 A

  Therefore, the object of the present invention is to perform foam molding by a simple and economical production method without impairing the excellent properties of the polyolefin-based foam molded article excellent in mechanical properties, heat resistance, chemical resistance, and weight reduction. An object of the present invention is to provide an interior material for automobiles that imparts sound absorbing performance to the body.

As a result of intensive studies to solve the above problems, the present inventors have an air flow resistance value of more than 3000 N · s / m ³ and 50000 N · s / m ³ or less when the thickness is 0.02 m, In addition, by adopting a polyolefin-based resin foam having a ratio of a static compressive stress at a strain rate of 10% to a static compressive stress at a strain rate of 50%, which is 0.3 or more and 0.5 or less, The present inventors have found that an automotive interior material having sound absorption performance can be obtained without impairing the excellent characteristics of the polyolefin-based foam molded article excellent in characteristics, heat resistance, chemical resistance, and weight reduction.

That is, the first invention is less large 50000N · s / m ³ air flow resistance than 3000N · s / m ³ when the thickness of 0.02 m, when 50% strain rate of static compressive stress It is related with the interior material for motor vehicles which consists of a polyolefin-type resin foam whose ratio with the static compressive stress at the time of the strain rate of 10% with respect to is 0.3-0.5.

As a preferred embodiment,
(1) The polyolefin resin foam is a foam obtained by filling a polyolefin resin foam particle in a mold and heating and foaming the foamed particle by steam, followed by a cooling step. The polyolefin resin expanded particles have a columnar shape with an average L / D of 2 or more and 3 or less, a cell diameter of 30 μm or more and 150 μm or less, and two DSC curves obtained by differential scanning calorimetry, From polyolefin resin expanded particles having β / (α + β) of 0.35 or more and 0.75 or less when the heat of fusion α (J / g) of the side peak and the heat of fusion β (J / g) of the high temperature side peak are used. The porosity of the obtained foam is 25% or more and 50% or less,
(2) The automobile interior material is a leg protection material,
(3) The automobile interior material is a head protecting material disposed in a pillar,
(4) The automobile interior material is a side collision pad,
(5) The passenger compartment side surface of the polyolefin resin foam is covered with a breathable sheet,
(6) The automotive interior material according to the above, wherein the surface of the polyolefin resin foam on the passenger compartment side is covered with a non-breathable sheet.

In the present invention, by using a value of the airflow resistance is increased 50000N · s / m ³ or less than 3000N · s / m ³ when the thickness 0.02m members of the passenger side, polyolefin-based resin foam molded Sound absorption performance can be imparted to the body. Furthermore, the ratio of the static compressive stress at the strain rate of 10% to the static stress at the strain rate of 50% is 0.3 or more and 0.5 or less, compared with the conventional shock absorber, Automotive interior materials with soft shock absorption characteristics can be obtained. That is, it is suitable for a member on the passenger side for the purpose of absorbing impact energy for maintaining quietness in the vehicle and protecting the occupant.

  Specifically, the lower limb protector for absorbing the impact from the occupant's sole, the side impact pad for absorbing the impact from the side of the vehicle, the head in the pillar for protecting the head By applying it to the protective material, it is possible to absorb not only the impact energy absorption performance but also the noise transmitted from the outside of the vehicle to the passenger compartment side, particularly the engine sound, so that the transmission of noise to the passenger compartment can be suppressed. That is, it is possible to achieve both the impact absorption performance and the sound absorption performance with one vehicle interior material. That is, it is possible to reduce the amount of use of other sound absorbing material or sound insulating material without deteriorating noise vibration (hereinafter sometimes referred to as NV) performance, and as a result, weight reduction and cost reduction can be realized.

  Furthermore, it is preferable to use the sound insulation sheet in combination with the sound insulation sheet in order to improve the NV performance because it can block the NV from the outside of the vehicle and absorb the sound transmitted to the inside of the vehicle from the gap of the vehicle component. In addition, in the case of combined use with a breathable sheet, noise that has entered the vehicle is absorbed by both the breathable sheet and the interior material of the present invention to which sound absorption is imparted, thus contributing to more quietness. This is preferable.

  The polyolefin-based resin foam used in the present invention provides innumerable small voids that contribute to sound absorption in the molded body by producing predetermined pre-expanded particles and molding in a mold under predetermined molding conditions. A structure having air permeability can be formed.

As a method for evaluating the air permeability, there is a measurement of air flow resistance. If the air flow resistance is too large or too small, an optimum sound absorbing effect cannot be obtained. If the air flow resistance value is too large, sound cannot enter the molded body, and a sound absorbing effect cannot be obtained. On the other hand, if the air flow resistance is too small, thermal energy conversion due to viscous resistance when sound passes through the molded body or air resonance due to the Helmholtz effect cannot be generated, and sound absorption performance may be exhibited. Can not. In the present invention, it is necessary to void as air flow resistance value becomes 50000N · s / m ³ or less larger than 3000N · s / m ³ when the thickness of 0.02 m. More preferably not more than 8000N · s / m ³ or more 30000N · s / m ^3. The air flow resistance (R) in the present invention is based on ISO 9053, when the sample thickness is 0.02 m, and the flow velocity v (m / s) and 0.0005 m / s are supplied. It is obtained from P (N / m ² ) and is represented by the following formula.

また、本発明に用いるポリオレフィン系樹脂発泡体は、発泡体内に無数の小空隙を有しているため、ひずみ率５０％時の静的圧縮応力に対するひずみ率１０％時の静的圧縮応力との比が０．３以上０．５以下、好ましくは０．３以上０．４以下である。

In addition, since the polyolefin resin foam used in the present invention has innumerable small voids in the foam, it has a static compressive stress at a strain rate of 10% with respect to a static compressive stress at a strain rate of 50%. The ratio is 0.3 or more and 0.5 or less, preferably 0.3 or more and 0.4 or less.

  The ratio of the static compressive stress at the strain rate of 10% to the static compressive stress at the strain rate of 50% is from 0.3 to 0.5. Comparison with density shows that the rise of static compressive stress with respect to strain is moderate. This is because, in the low strain region immediately after the start of compression, since the void portion in the molded body begins to fill up, the rise of the compression stress (reaction force) becomes gentler than that of the foamed molded body having no porosity. After distortion becomes large and the voids in the molded body are filled, the foamed molded body is simply compressed, so that it behaves like a conventional polyolefin foamed resin. Such an impact energy absorption waveform is suitable for a member for directly protecting an occupant from an impact, such as a leg protection material or a side impact pad. However, since the impact stress value required for each vehicle type is different, it is preferable to perform energy absorption design and shape design in consideration of impact energy absorption. Generally, the impact energy absorption may be adjusted by adopting a structure in which the foamed body is provided with a recess or a rib structure, and the target load-displacement curve is adjusted by adjusting the density of the foam. May be designed. By adding such a device, a predetermined impact energy absorption design for each vehicle type can be freely performed to some extent.

  Thus, in the automotive interior material of the present invention, the shock absorbing material (tibia pad) for protecting the lower limbs of the occupant, the shock absorbing material (knee pad) for protecting the knee, and the pillar are arranged inside the pillar. It can be suitably used for an impact absorbing material for protecting the head and an impact absorbing material (side impact pad) for protecting an occupant during a side collision.

  Next, a manufacturing method for forming a polyolefin resin foam having sound absorption performance and soft impact energy absorption characteristics used in the present invention will be described.

  Examples of polyolefin resins that can be used in the present invention include low, medium, high density polyethylene, linear low, ultra low density polyethylene, ethylene resins represented by ethylene-vinyl acetate copolymers, polypropylene, and ethylene-propylene. Examples thereof include a propylene-based resin represented by a random copolymer and an ethylene-propylene block copolymer. Among these, polyolefin resin is preferably used, and polypropylene resin is more preferably used.

  The polypropylene resin usable in the present invention is a polymer comprising propylene monomer units of 50% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and is a Ziegler type titanium chloride catalyst or metallocene catalyst. A polymer having a high degree of stereoregularity polymerized in (1) is preferred. Specific examples include, for example, propylene homopolymer, ethylene-propylene random copolymer, propylene-butene random copolymer, ethylene-propylene-butene random copolymer, ethylene-propylene block copolymer, maleic anhydride -Propylene random copolymer, maleic anhydride-propylene block copolymer, propylene-maleic anhydride graft copolymer, etc. are mentioned, and each is used alone or in combination. In particular, an ethylene-propylene random copolymer, a propylene-butene random copolymer, and an ethylene-propylene-butene random copolymer can be suitably used. Further, these polypropylene resins are preferably non-crosslinked, but crosslinked resins can also be used.

  Furthermore, the polypropylene resin used in the present invention has a melt index (hereinafter referred to as MI) measured at a temperature of 230 ° C. and a load of 2.16 kg in a range of 0.1 g / 10 min to 7 g / 10 min in accordance with JIS K7210. More preferably, it is 2 g / 10 min or more and 6 g / 10 min or less. When MI is less than 0.1 g / 10 min, the foaming force when producing pre-expanded particles is low, and it tends to be difficult to obtain pre-expanded particles with a high expansion ratio. Moreover, it tends to be difficult to ensure the fusion strength between the pre-expanded particles when a foamed molded body is obtained. When MI exceeds 7 g / 10 minutes, it tends to be difficult to control the porosity of the foamed molded product with a stable value.

  The polypropylene resin preferably has a melting point of 130 to 168 ° C, more preferably 135 to 160 ° C, and particularly preferably 140 to 155 ° C in order to obtain a foamed molded article having excellent mechanical strength and heat resistance. It is. When the melting point is within this range, there is a strong tendency to easily balance moldability, mechanical strength, and heat resistance. Here, the melting point means that 1 to 10 mg of resin is heated from 40 ° C. to 220 ° C. at a rate of 10 ° C./min by a differential scanning calorimeter, then cooled to 40 ° C. at a rate of 10 ° C./min, and again The peak temperature of the endothermic peak in the DSC curve obtained when the temperature is increased to 220 ° C. at a rate of 10 ° C./min.

  The expanded olefin resin particles used in the present invention are those using the polyolefin resin as a base resin, and it is preferable to use columnar olefin resin expanded particles having an average L / D of 2 or more and 3 or less.

  Here, the average L / D referred to in the present invention, as shown in FIG. 6, L is the length of the longest part of the expanded particles, D is the average value of the maximum diameter Dmax and the minimum diameter Dmin in a cross section perpendicular to the L direction. And is calculated by the following formula.

Ｌ方向に垂直な断面形状は、円、楕円等の凹部のない閉じた曲線であり、ＤｍａｘおよびＤｍｉｎはＬ方向に沿って略一定の値をとる。柱状形状のポリオレフィン系樹脂発泡粒子の具体例としては、円柱形状、楕円柱形状が挙げられる。

The cross-sectional shape perpendicular to the L direction is a closed curve without a concave portion such as a circle or an ellipse, and Dmax and Dmin take substantially constant values along the L direction. Specific examples of the columnar-shaped polyolefin resin expanded particles include a columnar shape and an elliptical columnar shape.

  By setting L / D to 2 or more and 3 or less, it is possible to form a high void while maintaining an appropriate contact area between the expanded particles when the mold is filled for molding. When L / D is less than 2, it is difficult to obtain a foamed molded article having a sufficient porosity when filled in a mold. When L / D is more than 3, clogging at the filling port is likely to occur when filling the mold, causing not only filling failure but also variation in the void ratio between the foamed molded products. It becomes easy.

  The polyolefin resin foamed particles used in the present invention preferably have a cell diameter of 30 μm to 150 μm, and more preferably 50 μm to 100 μm. When the cell diameter is within this range, it is easy to firmly fuse the foamed particles while maintaining the voids generated when filling the mold. When the cell diameter is less than 30 μm, sinking and shrinkage are likely to occur when the foamed molded article is formed, and the shape retainability deteriorates. When the cell diameter exceeds 150 μm, the porosity of the foamed molded product tends to be low. In particular, the porosity tends to decrease in the surface layer in contact with the mold surface.

  Furthermore, the expanded particles used in the present invention have two melting peaks in the DSC curve obtained by differential scanning calorimetry, the heat of fusion α (J / g) of the low temperature side peak, and the heat of fusion β of the high temperature side peak. Β / (α + β) when (J / g) is 0.35 or more and 0.75 or less, more preferably 0.55 or more and 0.65 or less. When β / (α + β) is less than 0.35, it is difficult to increase the porosity of the foamed molded product. This is presumably because the secondary foaming power of the foamed particles is increased and the porosity is reduced during molding. When β / (α + β) exceeds 0.75, fusion between the expanded particles becomes difficult. When the temperature of the steam used for molding is increased in order to promote fusion, the porosity of the foamed molded product is lowered, so that it is difficult to ensure both porosity and fusion.

  Here, the DSC curve obtained by differential scanning calorimetry of the expanded particles is obtained when 1 to 10 mg of expanded particles are heated from 40 ° C. to 220 ° C. at a temperature increase rate of 10 ° C./min by a differential scanning calorimeter. The contact on the low temperature side between the straight line passing through the maximum point A of the obtained DSC curve and the DSC curve is B, and the contact on the high temperature side is C. From the area surrounded by the line segment AB and the DSC curve, the heat of fusion α (J / g) of the low temperature side peak, and from the area surrounded by the line segment AC and the DSC curve, the heat of fusion β (J / g) of the high temperature side peak. Calculated.

  By using foamed particles that satisfy the above requirements, a foamed molded article having a porosity of preferably 25% or more and 50% or less can be easily obtained. The porosity of the foamed molded product is strongly related to the sound absorption characteristics, and the porosity is preferably 25% to 50%, more preferably 30% to 45%. When the porosity is less than 25%, the sound absorption rate at the peak frequency is lowered, and sufficient sound absorption characteristics may not be obtained. If the porosity exceeds 50%, the contact area between the expanded particles is reduced and cracking of the foamed molded product is likely to occur, and the mechanical strength is decreased and may not be practically used.

  Next, a method for producing the expanded polypropylene resin particles of the present invention will be described. The polypropylene resin is melted using a known method, for example, using an extruder, a kneader, a Banbury mixer (trademark), a roll or the like, in a columnar shape, and the weight of one grain is 0.2 to 10 mg. Preferably, it is processed into 0.5 to 6 mg of resin particles. Generally, it melts using an extruder and is manufactured by a strand cut method. For example, a polypropylene resin extruded in a strand from a circular die is cooled and solidified with water, air or the like to obtain resin particles having a desired shape.

  Due to the heat treatment at the time of producing foamed particles from the resin particles, the resin particles cause residual strain relaxation, and thus shrinkage occurs in the stretching direction. Therefore, in the production of resin particles, it is necessary to take into account the shrinkage in the stretching direction and to have a resin particle shape that provides the desired L / D foamed particles. Specifically, it is necessary to make resin particles having a larger L / D with respect to the L / D of the intended expanded particles. The L / D of the resin particles to be produced varies depending on the MI of the polypropylene resin to be used, the molecular weight distribution, the degree of stretching during the production of the resin particles, etc., but cannot be defined unconditionally, but is generally in the range of 4-9.

  During the production of the resin particles, the cell diameter of the expanded particles is adjusted to a desired value by adding a cell nucleating agent. As the cell nucleating agent, inorganic nucleating agents such as talc, calcium carbonate, silica, kaolin, titanium oxide, bentonite and barium sulfate are generally used. The amount of cell nucleating agent added varies depending on the type of polypropylene resin used and the type of cell nucleating agent, and cannot be specified unconditionally, but is generally 0.001 to 2 parts by weight per 100 parts by weight of polypropylene resin. It is.

  Furthermore, during the production of the resin particles, various additives can be added as necessary within a range that does not impair the properties of the polypropylene resin. Examples of additives include: colorants such as carbon black and organic pigments; antistatic agents comprising nonionic surfactants such as alkyldiethanolamides, alkyldiethanolamines, hydroxyalkylethanolamines, fatty acid monoglycerides, and fatty acid diglycerides; IRGANOX 1010 ( Hindered phenolic antioxidants such as IRGAFOS 168 ™, IRGAFOS P-EPQ ™, IRGANOX 1076 ™, IRGANOX 1330 ™, IRGANOX 1425WL ™, IRGANOX 3114 ™, ULTRANOX 626 ™; Phosphorus processing stabilizers such as IRGAFOS 126 (trademark) and WESTON 619 (trademark); Lactic processing stabilizers such as HP-136 (trademark) Hydroxylamine processing stabilizers such as FS042 ™, metal deactivators such as IRGANOX MD1024 ™; benzotriazole UV absorbers such as TINUVIN326 ™ and TINUVIN327 ™; TINUVIN120 ™ Benzoate light stabilizers; hindered amine light stabilizers such as CHIMASSORB 119 (trademark), CHIMASSORB 944 (trademark), TINUVIN 622 (trademark), TINUVIN 770 (trademark); flame retardant aids such as halogen flame retardants and antimony trioxide; (Trademark), non-halogen flame retardants such as MELAPUR MC25 (trademark); acid neutralizers such as hydrotalcite and calcium stearate; IRGASTAB NA11 (trademark), etc. Crystal nucleating agent; erucamide, such as lubricants, such as stearic acid amide are exemplified.

  A conventionally known method can be used for producing the expanded particles in the present invention. For example, an aqueous dispersion medium containing the resin particles, the foaming agent, the dispersant, and the dispersion aid is charged into a sealed container, and the temperature is raised while stirring to increase the temperature of the resin particles as a constant temperature (hereinafter sometimes referred to as the foaming temperature). After impregnating with a foaming agent, add additional foaming agent as necessary to maintain the inside of the sealed container at a constant pressure (hereinafter sometimes referred to as foaming pressure), and then remove the contents from the bottom of the sealed container. Foamed particles are produced by a method of releasing in a lower pressure atmosphere. The airtight container to be used is not particularly limited and may be any container that can withstand the pressure in the container and the temperature in the container at the time of producing the foamed particles, and examples thereof include an autoclave type pressure resistant container.

  Examples of the blowing agent include aliphatic hydrocarbons such as propane, isobutane, normal butane, isopentane, and normal pentane, and mixtures thereof; inorganic gases such as air, nitrogen, and carbon dioxide; and water. In order to obtain expanded particles having a higher expansion ratio, it is preferable to use isobutane, normal butane and a mixture thereof as a foaming agent. In order to obtain expanded particles with low expansion ratio and small expansion ratio variation, it is preferable to use water as a foaming agent.

  When water is used as a foaming agent, it is preferable to add a water absorbing agent such as sodium ionomer, potassium ionomer, melamine, or isocyanuric acid when the resin particles are produced.

  The amount of foaming agent used varies depending on the type of polypropylene resin used, the type of foaming agent, the target foaming ratio, etc., and cannot be specified unconditionally, but is generally 2 to 60 with respect to 100 parts by weight of the polypropylene resin. The range is parts by weight.

  Examples of the dispersing agent include poorly water-soluble inorganic compounds such as basic tricalcium phosphate, basic magnesium carbonate, calcium carbonate, and aluminum oxide. Examples of the dispersing aid include dodecylbenzene sulfonic acid soda and linear alkyl fin sulfonic acid soda. Anionic surfactants such as are used. Among these, the use of basic tricalcium phosphate and linear alkyl fin sulfonic acid soda is preferable for obtaining good dispersibility. The amount of these dispersants and dispersion aids used varies depending on the type, the type and amount of the polypropylene resin used, the type of foaming agent, etc., but usually 0.1 to 3 dispersants per 100 parts by weight of water. It is preferable that the amount is 0.0001 to 0.1 part by weight of a dispersion aid.

  In order to improve the dispersibility of the resin particles in water, it is usually preferable to use 20 to 100 parts by weight of resin particles with respect to 100 parts by weight of water.

  The aqueous dispersion of polypropylene resin particles thus adjusted in a closed container is heated to a predetermined foaming temperature with stirring, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. At the same time, the pressure in the sealed container rises, and the foaming agent is impregnated with the resin particles. Thereafter, the foaming agent is additionally supplied until a predetermined foaming pressure is reached, and is maintained for a certain time, usually 5 to 180 minutes, preferably 10 to 60 minutes. Thus, an aqueous dispersion of polypropylene resin particles held at the foaming temperature and foaming pressure is released into a low-pressure atmosphere (usually atmospheric pressure) by opening a valve provided at the bottom of the sealed container. Resin foam particles can be produced.

  When the aqueous dispersion of resin particles is discharged into a low-pressure atmosphere, it can also be discharged through an opening orifice of 2 to 10 mmφ for the purpose of adjusting the flow rate and reducing the magnification variation. In some cases, the low-pressure atmosphere is filled with saturated steam for the purpose of increasing the expansion ratio.

  The foaming temperature varies depending on the melting point [Tm (° C.)] of the polypropylene resin used, the type of foaming agent, etc., and cannot be specified unconditionally, but is generally determined from the range of Tm−30 (° C.) to Tm + 10 (° C.). . The foaming pressure varies depending on the type of polypropylene resin to be used, the type of foaming agent, and the foaming ratio of the desired foamed particles, and cannot be specified unconditionally, but is generally determined from the range of 1 to 8 MPa (gauge pressure).

  The value of β / (α + β) of the expanded particles calculated from the DSC curve can be adjusted by adjusting the expansion temperature. When the foaming temperature is increased, β / (α + β) is decreased, and when the foaming temperature is decreased, β / (α + β) is increased. However, when an aliphatic hydrocarbon is used as the foaming agent, the melting point of the polypropylene resin is lowered due to the plasticizing effect, so the value of β / (α + β) is affected by the amount of foaming agent impregnation, that is, the foaming pressure. Therefore, the value of β / (α + β) is adjusted by adjusting the foaming temperature and the foaming pressure. When the foaming pressure is increased, β / (α + β) is decreased, and when the foaming pressure is decreased, β / (α + β) is increased.

  The polypropylene resin expanded particles obtained as described above can be formed into a polypropylene resin expanded molded article having a porosity of preferably 25% to 50% by a conventionally known molding method. For example, a) A method in which foamed particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the foamed particles to give a predetermined pressure inside the foamed particles, filled in a mold, and heated and fused with water vapor. In particular, a method such as a method in which expanded particles are filled in a mold without pretreatment and heat-sealed with water vapor can be used.

  Among the molding methods described above, the foamed particles are pressurized with an inorganic gas, impregnated with the inorganic gas in the foamed particles to give a predetermined foamed particle internal pressure, filled into a mold, and heated and fused with water vapor. Is more preferable, and the internal pressure of the expanded particle is more preferably 0.12 MPa or more and 0.18 MPa or less in absolute pressure. By setting the internal pressure of the expanded particles to 0.12 MPa or more and 0.18 MPa or less, it becomes easier to control the porosity of the molded product, and a foamed molded product having a porosity of 25% to 50% can be more stably produced. .

  As the inorganic gas, air, nitrogen, oxygen, helium, neon, argon, carbon dioxide gas, or the like can be used. These may be used alone or in combination of two or more. Among these, highly versatile air and nitrogen are preferable.

  In the present invention, foamed particles are heated and fused with water vapor during molding. If the water vapor temperature at this time is too low, the fusion is insufficient and the shape as a foamed molded article cannot be maintained. On the contrary, when the water vapor temperature is too high, the porosity of the foamed molded product is lowered, and the sound absorption performance tends to deteriorate. In order to satisfy both the fusion property between the foamed particles and the porosity, when the melting point of the polypropylene resin used as the base resin is Tm (° C), the temperature is Tm-25 (° C) to Tm (° C). It is preferable to mold with water vapor, and it is more preferable to mold with water vapor having a temperature of Tm-20 (° C) to Tm-5 (° C).

  Next, FIG. 1 shows a vehicle floor structure according to an embodiment configured by applying the lower limb protection structure of the present invention. The floor structure according to the present embodiment constitutes a floor portion on the driver's seat side in the passenger compartment, and includes a plate-like floor panel 1. Of course, it is preferable that the passenger seat side has the same configuration. The floor panel 1 has a dash panel 2 that is an inclined portion on the front side (engine room side), and the inclined portion extends obliquely upward to the front. An engine room 3 is generally disposed in front of the dash panel 2. On the driver's seat side, a brake pedal and an accelerator pedal (not shown) are arranged above the dash panel 2.

  A lower limb protection member 4 for protecting the lower limbs is disposed above the floor panel 1, that is, with a boundary between the dash panel 2 and the horizontal portion behind it. The shape of the lower limb protection member 4 is a substantially square plate, with the front portion disposed above the dash panel 2 and the rear portion disposed in the horizontal portion. The upper part is a breathable sheet (sound-absorbing carpet 5) or the sheet that is not breathable on the lower limb protection material side and the seat is substantially integrated with a sound-absorbing material such as felt on the passenger compartment side (sound insulation) Sex carpet 5) is laminated. Eventually, the soles (buttocks) of the occupant are disposed on the carpet 5. Further, in order to prevent rubbing noise between the lower limb protection material 4 and the dash panel 2, a fibrous material 6 may be integrated on the vehicle body side of the lower limb protection material. In this case, the lower limb protection material 4 is As the core material, a sound-absorbing carpet or sound-insulating carpet and a felt or fibrous material are laminated on two opposing surfaces.

  With the configuration of the lower limb protection material 4 and the sound absorbing carpet 5, the transmitted sound from the engine room is absorbed by the lower limb protection material 4 having the sound absorption performance of the present invention, and noise entering the passenger compartment is also First, the sound absorbed by the carpet 5 and then transmitted through the carpet 5 can be absorbed by the lower limb protection material 4. Thus, by arranging the lower limb protection material 4 having the sound absorbing performance and the sound absorbing carpet 5 together, it is possible to absorb the sound entering and exiting the passenger compartment, thereby preventing a decrease in the NV performance. Moreover, when it is set as the structure with a sound insulation carpet, the lower limb part protection material 4 of this invention will absorb and attenuate the transmitted sound from an engine room. Since the attenuated transmitted sound can be easily sound-insulated by the sound-insulating carpet, the NV performance can be effectively prevented from being lowered even in such a configuration.

  2 and 3 show the structure of a vehicle front side door 7 according to an embodiment in which the present invention is applied to a side projection. In the structure of the front side door 7 according to the present embodiment, a side door 10 having a closed cross-sectional shape including a door outer panel 8 and a door inner panel 9 is provided, and a door trim 11 is provided on the passenger compartment side of the side door body 7. Yes. An upper shock absorber 12 and a lower shock absorber 13 are provided on the door trim 11 so as to protrude toward the passenger compartment corresponding to the chest and waist of the occupant, and between the door inner panel 9 and the door trim 11, The side collision pad 14 of the present invention is disposed inside the upper protrusion 12 and the lower protrusion 13. With such an arrangement, road noise transmitted between the door panels or NV from the engine compartment can be effectively absorbed, and the interior of the vehicle can be kept quiet.

  An embodiment in which the present invention is applied to a shock absorber 16 inside a front pillar 15 of an automobile will be described. As shown in FIGS. 4 and 5, the front pillar 15 is provided with a pillar body 19 having a closed cross-section formed of a pillar outer panel 17 and a pillar inner panel 18, and a pillar trim 20 is disposed on the passenger compartment side of the pillar body 19. Is provided. An impact energy absorber 16 is provided between the pillar inner panel 18 and the pillar trim 120. By applying the present invention to the impact energy absorbing member 16, it is possible to absorb NV entering from the outside of the vehicle or from the engine room and keep the inside of the vehicle quietly. Although the present invention is applied to the front pillar 15, the present invention can be similarly applied to the center pillar 21 and the rear pillar 22.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example.

Example 1
First, in order to produce the pre-expanded particles made of polypropylene of the present invention, as a base resin, MI: 4.5 g / 10 min, melting point: 144 ° C., ethylene content: 2.8%, butene content: 1.3 %, Using 300% talc as a cell nucleating agent, melt-kneaded in an extruder, extruded into a strand from a circular die, cooled with water, cut with a cutter, and the weight of one grain is 1.8 mg / grain, Resin particles having a cylindrical shape and L / D of 6.3 were obtained. 100 parts by weight (65 kg) of the obtained resin particles, 200 parts by weight of water, 0.5 parts by weight of basic tricalcium phosphate and 0.01 parts by weight of sodium alkyl sulfonate are charged into a pressure-resistant autoclave having a capacity of 0.35 m ³ . Under stirring, 16 parts of isobutane was added as a blowing agent, and then the autoclave contents were heated to a foaming temperature of 135 ° C. Thereafter, isobutane was additionally injected and the pressure was increased to a foaming pressure of 2.2 MPa. After maintaining the foaming temperature and the foaming pressure for 30 minutes, the valve at the bottom of the autoclave was opened, and the autoclave contents were passed through a 4.4 mmφ orifice. Release under atmospheric pressure to obtain expanded particles. The obtained expanded particles had L / D: 2.2, cell diameter: 103 μm, β / (α + β): 0.60, and bulk density: 30 kg / m ³ . Air was pressed into the pre-expanded particles by air pressure treatment to the polypropylene-based pre-expanded particles obtained here, and finally the pressure inside the pre-expanded particles was 0.14 MPa in absolute pressure.

Next, molding will be described. The mold used was a block shape of 0.9 × 0.9 × 0.05 m. First, the cracking was set to 0.005 m, and the pre-expanded particles were filled into the mold with the mold slightly opened. Heating is performed in the exhaust process 5 seconds (fixed, moving drain valve opened), one heating 10 seconds, reverse one heating 5 seconds, double-sided heating 20 seconds (vapor pressure 0.18 MPa), After precooling 5 seconds (cooling with the drain valve closed) and water cooling 30 seconds, the product was released. Subsequently, after standing to cool in the air for 1 hour, left in a drying room at 75 ° C. for 24 hours, taken out from the drying room and allowed to cool at room temperature for 3 hours, and then the following porosity and air flow resistance: The performance of sound absorption coefficient or static compression characteristics was evaluated. The foam density after drying was 34 kg / m ³ .

Each measurement method is described below.
(Porosity)
A 0.02 × 0.02 × 0.040 m rectangular parallelepiped sample was cut out from the obtained foamed molded product having an approximate size of 0.9 × 0.9 × 0.05 m so as not to include the surface skin layer. The apparent volume V ₁ (m ³ ) was determined. Further, the rectangular parallelepiped sample was immersed in a graduated cylinder containing a certain amount of ethanol, and the increased volume V ₂ (m ³ ) at that time was measured and determined by the following equation.

（流れ抵抗）
ＩＳＯ ９０５３に準拠し流れ抵抗の測定を行った。流速ｖ（ｍ／ｓ）、０．０００５ｍ／ｓを供給した時に、試料前後の圧力差△Ｐ（Ｎ／ｍ²）より、試料の所定厚さにおける流れ抵抗Ｒ（Ｎ・ｓ／ｍ³）は式１により算出される。特に、ここでの流れ抵抗の定義は、試料厚みが０．０２ｍとした時のものとした。
（垂直入射式吸音測定）
ＪＩＳ Ａ１４０５に準拠し、試料厚み０．０３ｍで５００〜６４００Ｈｚでの垂直入射吸音率を測定した。試料は得られた発泡体より、表面スキン層を有する面が音波入射面となるように、厚み０．０３ｍで切り出した。測定は、音波を反射する剛体壁と試料が密着した状態、つまり背後空気が無い状態でおこなった。測定には小野測器社製の垂直入射吸音率測定装置ＳＲ−４１００を用いた。
（残響室による吸音測定）
残響室による測定は、ＪＩＳ Ａ１４０９に従い、９ｍ³の残響室（日東紡音響エンジニアリング製）にて行った。試料は発泡体０．９×０．９×０．０５ｍを０．７×０．７×０．０３ｍにスライス加工した。残響室内での試料の設置は、試料の側面からの音の侵入を防止するために金属製の治具を周囲に取り付け、スキン面を上側（吸音面）に、スライス面を下側（床面）となるように設置し、周波数５００〜５０００Ｈｚの範囲で測定した。また、通気性を有する繊維質との組合せの吸音測定は、スキン面を上側にした試料の上側に通気性を有する繊維質を積層した状態での吸音測定を行った。
（静的圧縮試験）
ここで本発明における静的圧縮応力の測定は、ＮＤＳＺ０５０４に準拠して、温度２３℃、湿度６５％の恒温恒湿室にて、試料寸法０．１×０．１×０．０２５ｍを用い、圧縮スピード０．０１ｍ／分で圧縮測定を行った
（実施例２）
実施例１とまったく同様の操作にてポリプロピレン系樹脂発泡体を成形、吸音測定用の試料０．７×０．７×０．０３ｍを作成した。この発泡成形品の上部に吸音特性を有する樹脂カーペットを積層し、残響室での吸音測定を行った。
（比較例１）
セル造核剤としてタルク１００ｐｐｍを添加した以外は実施例１と同様の方法で発泡成形体を得た。成形に用いた発泡粒子は、Ｌ／Ｄが１．０、セル径が２２０μｍ、β／（α＋β）が０．２６のポリプロピレン系予備発泡粒子であった。ここで得られたポリプロピレン系予備発泡粒子に空気加圧処理により空気を予備発泡粒子内に圧入し、絶対圧力で０．２ＭＰａとした。実施例と同じ金型を用いて成形した結果、該発泡粒子は従来から一般的に用いられている発泡粒子の特性を有しており、発泡粒子間に空隙のない発泡成形体が得られた。成形条件は、クラッキングを５ｍｍに設定し金型が僅かに開いた状態で原料を充填した。加熱は排気工程５秒（固定、移動のドレン弁を開いた状態）で行い、一方加熱１０秒、逆一方加熱５秒、両面加熱２０秒（蒸気圧力０．３２ＭＰａ）で加熱工程を完了し、予冷１０秒（ドレン弁を閉じた状態で冷却）、水冷１８０秒を行った後、製品を離型した。これ以降の乾燥工程は実施例１と同様の操作を行うとともに、同様の物性測定を行った。乾燥後の発泡体密度は３０ｋｇ／ｍ³であった。

(Flow resistance)
The flow resistance was measured according to ISO 9053. When a flow velocity v (m / s), 0.0005 m / s is supplied, the flow resistance R (N · s / m ³ ) at a predetermined thickness of the sample from the pressure difference ΔP (N / m ² ) before and after the sample. Is calculated by Equation 1. In particular, the definition of the flow resistance here is that when the sample thickness is 0.02 m.
(Normal incidence type sound absorption measurement)
In accordance with JIS A1405, the normal incident sound absorption coefficient at 500 to 6400 Hz was measured with a sample thickness of 0.03 m. The sample was cut out from the obtained foam with a thickness of 0.03 m so that the surface having the surface skin layer was the sound wave incident surface. The measurement was performed in a state where the sample was in close contact with the rigid wall that reflects sound waves, that is, in the absence of air behind. For the measurement, a normal incidence sound absorption measuring device SR-4100 manufactured by Ono Sokki Co., Ltd. was used.
(Sound absorption measurement by reverberation room)
The reverberation chamber was measured in a 9 m ³ reverberation chamber (Nittobo Acoustic Engineering) according to JIS A1409. The sample was sliced from foam 0.9 × 0.9 × 0.05 m to 0.7 × 0.7 × 0.03 m. The sample is placed in the reverberation chamber by attaching a metal jig around it to prevent sound from entering from the side of the sample, with the skin surface on the upper side (sound absorbing surface) and the slice surface on the lower side (floor surface) ) And measured in a frequency range of 500 to 5000 Hz. Further, the sound absorption measurement in combination with the fiber having air permeability was performed by measuring the sound absorption in a state where the fiber having air permeability was laminated on the upper side of the sample with the skin surface on the upper side.
(Static compression test)
Here, the measurement of the static compressive stress in the present invention is based on NDSZ0504, using a sample size of 0.1 × 0.1 × 0.025 m in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 65%. Compression measurement was performed at a compression speed of 0.01 m / min (Example 2).
A polypropylene resin foam was molded in the same manner as in Example 1 to prepare a sample for measuring sound absorption 0.7 × 0.7 × 0.03 m. A resin carpet having sound absorption characteristics was laminated on the foam molded product, and the sound absorption was measured in a reverberation chamber.
(Comparative Example 1)
A foamed molded article was obtained in the same manner as in Example 1 except that 100 ppm of talc was added as a cell nucleating agent. The expanded particles used in the molding were polypropylene pre-expanded particles having an L / D of 1.0, a cell diameter of 220 μm, and β / (α + β) of 0.26. The polypropylene pre-expanded particles obtained here were pressed into the pre-expanded particles by an air pressurizing process to an absolute pressure of 0.2 MPa. As a result of molding using the same mold as in the examples, the foamed particles had characteristics of foamed particles generally used from the past, and a foamed molded product having no voids between the foamed particles was obtained. . The molding conditions were such that the cracking was set to 5 mm and the raw material was filled with the mold slightly opened. Heating is performed in the exhaust process 5 seconds (fixed, moving drain valve is open), one heating 10 seconds, reverse one heating 5 seconds, double-sided heating 20 seconds (vapor pressure 0.32 MPa), complete the heating process, After pre-cooling 10 seconds (cooling with the drain valve closed) and water cooling 180 seconds, the product was released. The drying process after this performed the same operation as Example 1, and measured the same physical property. The foam density after drying was 30 kg / m ³ .

  The performance of the examples and comparative examples of the present invention will be described.

The porosity of the sample of Example 1 was 28%, and the air flow resistance value with a thickness of 0.02 m was 12000 N · s / m ³ . Since the sample of Comparative Example 1 had a porosity of 0% and lacked air permeability, the air flow resistance could not be measured.

  First, the sound absorption characteristics were compared. In the comparison of the sound absorption curve by the normal incidence measurement of the example and the comparative example (FIG. 7), since the example 1 had an appropriate porosity and air flow resistance, the maximum sound absorption coefficient 0.97 (frequency 1650 Hz) was good. In contrast to the sound absorption curve, in Comparative Example 1, since there was no continuous air gap, the maximum sound absorption rate was 0.1 or less in the frequency range before measurement, and the sound absorption performance was not exhibited. From the sound absorption measurement result by the reverberation chamber measurement method, a result showing the same tendency as the normal incidence type measurement is obtained (FIG. 8).

  Furthermore, in order to approximate the state of an actual vehicle, the sound absorption of the reverberation chamber was measured in a state where the resin carpet having the sound absorbing performance shown in FIG. 9 and the product of the present invention were laminated. As a result (FIG. 10), by laminating the resin carpet on the sound absorbing performance of the present invention, the sound absorbing performance that is the sum of the sound absorbing performance of the single unit was developed, and the sound absorbing performance was remarkably improved. In particular, the present invention adds a sound absorption characteristic in the high frequency range of the resin carpet, and a sound absorption performance in a wide frequency range is obtained. As described above, the present invention exhibits good sound absorbing performance even when it is a simple substance, and it is possible to further improve sound absorbing performance by using it together with a fibrous sheet containing felt.

Next, static compression characteristics will be described. FIG. 11 shows strain-compression stress curves of Example 1 and Comparative Example 1. FIG. 12 is a plot of the compressive stress at 10% strain in FIG. 11 versus the foam density, and FIG. 13 shows the compressive stress at 50% strain. Example 1 has a density of 34 kg / m ³ , and Comparative Example 1 is only an example of a density of 30 kg / m ^{3. In} FIGS. 12 and 13, measurements were performed in a wider range of density and compared. As is clear from FIG. 12, in the comparison at the time of 10% strain, the compressive stress of Example 1 is about 60% compared to Comparative Example 1, and it can be seen that the load increase curve is gentle in the low strain region. This is because the void portion of the foam having voids is mainly compressed in the low strain region, and thus the load value is lower than that of Comparative Example 1 (without voids). On the other hand, in the 50% strain region portion, the void portion has already disappeared, and compression of the foamed resin portion has occurred, so the difference between Example 1 and Comparative Example 1 tends to be small (FIG. 13). The ratio of 10% strain load to 50% strain load of the present invention was 0.37 in the example and 0.6 in the comparative example 1.

  The present invention having such characteristics can be used for an impact absorbing material for protecting an occupant. In particular, when protecting the lower limbs of the occupant and absorbing the collision energy at the time of a side collision, the collision energy can be absorbed without increasing the extreme load value (reaction force value). Is preferred.

  As described above, by applying the present invention as described above, it is possible to provide a foamed molded article having sound absorbing performance by a simple and economical manufacturing method. Furthermore, the present invention is suitable for a lower limb protection material that requires both an impact energy absorbing material and a sound absorbing material at the time of a collision, or a side impact pad, and an impact absorbing material inside a pillar.

Lower limb protection structure diagram for automobile according to an embodiment of the present invention Schematic of a front door for an automobile according to an embodiment of the present invention AA sectional view of a front door for an automobile according to an embodiment of the present invention. Schematic of an automobile pillar according to an embodiment of the present invention BB sectional drawing of the pillar for motor vehicles concerning an embodiment of the invention. Definition diagram of L / D in the present invention Sound absorption data by normal incidence measurement Sound absorption measurement data by reverberation room Sound absorption data of resin carpet (reverberation room measurement) Sound absorption data (reverberation room measurement) when resin carpet and the present invention are laminated Static compression characteristics (strain-compressive stress curve) of the present invention Compressive stress with strain of 10% in static compression measurement Compression stress of 50% strain in static compression measurement

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Floor panel 2 Dash panel 3 Engine room 4 Lower limb protection material 5 Carpet 6 Fibrous material 7 Front side door 8 Door outer panel 9 Door inner panel 10 Side door 11 Door trim 12 Upper shock absorber 13 Lower shock absorber 14 Side impact pad 15 Front pillar 16 Shock absorber 17 Pillar outer panel 18 Pillar inner panel 19 Pillar body 20 Pillar trim 21 Center pillar 22 Rear pillar

Claims (7)

Air flow resistance value when the thickness of 0.02m is less large 50000N · s / m ³ than 3000N · s / m ^3, the static time 10% strain rate for the static compressive stress at 50% strain rate An automotive interior material comprising a polyolefin resin foam having a ratio to a compressive stress of 0.3 to 0.5.   The polyolefin resin foam is a foam obtained by filling a polyolefin resin foam particle in a mold, heating with water vapor, foaming and fusing the foamed particle, and then undergoing a cooling step. The average L / D of the resin-based resin expanded particles is 2 or more and 3 or less, the cell diameter is 30 μm or more and 150 μm or less, and the DSC curve obtained by differential scanning calorimetry has two melting peaks. It consists of polyolefin resin expanded particles having β / (α + β) of 0.35 or more and 0.75 or less when the heat of fusion α (J / g) and the heat of fusion β (J / g) at the high temperature side peak are obtained. The automobile interior material according to claim 1, wherein the porosity of the obtained foam is 25% or more and 50% or less.   The automotive interior material according to claim 1 or 2, wherein the automotive interior material is a lower limb protection material.   The automotive interior material according to claim 1 or 2, wherein the automotive interior material is a head protecting material disposed in a pillar.   The automotive interior material according to claim 1 or 2, wherein the automotive interior material is a side impact pad.   The interior material for automobiles according to any one of claims 1 to 5, wherein a surface of the polyolefin resin foam on the passenger compartment side is covered with a sheet having air permeability.   The interior material for automobiles according to any one of claims 1 to 5, wherein a surface of the polyolefin resin foam on the passenger compartment side is covered with a non-breathable sheet.

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