JP2002079631A - Member for vehicle and cushioning member for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member for a vehicle which is lightweight and has high rigidity and consists of a polyolefin resin composite foam and a cushioning member for the vehicle exhibiting furthermore lower water absorption properties. SOLUTION: A face material is laminated on at least one face of a polyolefin resin foam sheet in which mean value of aspect ratios Dz/Dx of air bubbles existing inside is 1.1-5 and whose compression elasticity is 10 kgf/cm2 or larger.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a vehicle member and a vehicle cushioning member.

[0002]

2. Description of the Related Art Conventionally, on the lower surface of an engine of an automobile,
By attaching an under tray or the like, it has been practiced to prevent the engine from being splashed with water during traveling and pebbles or the like splashed by tires from hitting the engine.

However, the conventional under tray is usually
Iron plates, synthetic resins and the like are used. In this case, when an iron plate is used, there is a problem that when a pebble or the like bounced by a tire hits the engine, not only a loud impact sound is generated, but also the iron plate is corroded by rainwater or the like. In addition, when a synthetic resin is used, there is a problem that the tire is damaged by pebbles or the like splashed on the tire.

[0004] In order to solve the above-mentioned problems, Japanese Patent Laid-Open Publication No.
No. 92461, the surface of the thermoplastic resin sheet,
Attempts have been made to improve the drawbacks of the synthetic resin by attaching a stretched thermoplastic resin reinforcing member for heat fusion and integrating the thermoplastic resin sheet with the reinforcing member.

On the other hand, materials such as bumper springs for automobile suspensions used under high compression conditions are mainly vulcanized rubber. However, in order to solve the problems of running stability, ride comfort and weight reduction, Recently, members made of polyurethane elastomer sponge (hereinafter abbreviated as sponge) have been put to practical use.

[0006] However, sponges have the property of inherently high water absorption. Therefore, when they are used as materials for automobile parts, the following problems have occurred.

1: Absorbed water freezes at a low temperature of 0 ° C. or less, failing to obtain the sponge's original excellent buffering performance, and also causing early breakage under repeated high compression conditions, significantly lowering durability. I do.

2: The steel member constituting the buffer member and the like is corroded and abraded early by the absorbed water.

3: Adhesion peeling occurs at the interface between the steel member and the sponge member constituting the buffer member and the like due to the absorbed water, and the durability is reduced.

[0010]

The above-mentioned disadvantages of the sponge member are caused by the water absorption characteristic of the sponge and the cell shape of the sponge. The sponge is easy to absorb water because of its substantially open cell structure. Some sponges have a closed-cell structure, but they have a large cell size and are difficult to withstand repeated use under high compression conditions.

In order to solve these problems, a sponge member provided with a protective cover, a sponge member having a skin layer formed on the surface thereof, and a sponge member having a skin layer formed thereon are disclosed.
As described in Japanese Patent No. 453, a sponge member having a water-repellent skin layer formed on the surface thereof has been proposed. However, none of these has completely solved the above-mentioned problem.

[0012] In recent years, the use of urethane has been considered to be avoided from an environmental point of view, and there is a movement to remove urethane. Also, in the automotive industry, there is a movement to unify the materials using thermoplastic resins in consideration of the recyclability of used products, and polyolefin resins represented by polypropylene having high heat resistance are receiving attention.

However, the polyolefin resin alone has a specific gravity as high as about 0.9, and a composite foam using a general polyolefin resin foam has problems such as low compressive strength.

An object of the present invention is to provide a vehicle member made of a polyolefin resin composite foam which is lightweight and has high rigidity, and a vehicle cushion member exhibiting even lower water absorption in view of the above points. It is in.

[0015]

Means for Solving the Problems A vehicle member according to the present invention comprises:
The average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 5, and the face material is laminated on at least one surface of the polyolefin resin foam sheet having a compression modulus of 10 kgf / cm ² or more. It is a feature.

Examples of the vehicle member include impact-resistant vehicle members such as an under tray.

As the face material, a nonwoven fabric or a stretched sheet made of a polyolefin resin is preferable.

The polyolefin which is the main component of the polyolefin resin in the vehicle member of the present invention is a homopolymer of an olefinic monomer or a copolymer of a main component olefinic monomer and another monomer, and is particularly limited. Although not a thing, for example, polyethylene such as low-density polyethylene, high-density polyethylene, linear low-density polyethylene, homo-type polypropylene, random-type polypropylene, polypropylene such as block-type polypropylene, polybutene, ethylene-propylene copolymer, ethylene Examples include ethylene-based copolymers such as propylene-diene terpolymer, ethylene-butene copolymer, ethylene-vinyl acetate copolymer, and ethylene- (meth) acrylate copolymer. And two or more of these Or may be combined.

As the polyolefin constituting the main component of the polyolefin resin in the vehicle member of the present invention, one or a combination of two or more of the above-mentioned polyethylene and polypropylene is preferable.

The polyolefin resin in the vehicle member of the present invention usually means that the proportion of the polyolefin is 70%.
About 100% by weight. The resin other than the polyolefin constituting the polyolefin resin is not limited, and examples thereof include polystyrene and styrene elastomer. If the proportion of polyolefin in the polyolefin resin is less than 70% by weight, not only the characteristics of polyolefin such as light weight, chemical resistance, flexibility and elasticity cannot be exhibited, but also it is difficult to secure the melt viscosity required for foaming. This is not preferable because it may result in

As used herein, the term "aspect ratio" refers to the number (arithmetic) of the ratio of the maximum diameter in the fixed direction of bubbles in a polyolefin resin foam sheet (hereinafter sometimes simply referred to as "foam sheet"). ) Average value, diameter Dz in the sheet thickness direction and diameter Dxy in the in-plane direction
And expressed as a ratio Dz / Dxy.

That is, as shown in FIG. 1, an enlarged photograph (c) of 10 times the arbitrary cross section (b) parallel to the sheet thickness direction (called the z direction) of the foam sheet (a) is taken. Photo
(c) Measure the following two fixed-direction maximum diameters (Dz, Dxy) of at least 50 bubbles randomly selected in the above, and calculate the number average value.

Dz: the maximum diameter of the cells in the foam sheet parallel to the z direction Dxy: the sheet width or length direction of the cells in the foam sheet, that is, the plane direction perpendicular to the z direction (called the xy direction)
Maximum diameter parallel to

Here, the "in-plane direction" means any direction (also referred to as an xy direction) in the sheet surface of the foam sheet, and includes a length direction and a width direction.

A foam having spindle-shaped cells flattened in the z-direction, such as the foam sheet used in the present invention, has a high rigidity in the elastic deformation region with respect to the pressure in the z-direction. Although it functions, when a load or impact exceeding the compressive yield stress is applied, the bubble buckles, thereby absorbing the energy of the load or impact, and thus also functions as a shock absorber.

Further, since the compressive strength and elastic modulus are increased, when a face material having high tensile strength is laminated on the surface in the xy direction, the compressive fracture in the z direction is less likely to occur, and the flexural modulus and flexural strength of the composite foam are reduced. improves.

The average value of the aspect ratio of the foam sheet is 1.1 to 5, preferably 1.3 to 3. When the aspect ratio is less than 1.1, the bubbles become substantially spherical, and the improvement in the compressive strength due to the spindle shape cannot be obtained. As a result, the bending rigidity of the vehicle member decreases, and the shock absorption decreases. If the aspect ratio exceeds 5, the compressive yield stress becomes too high, so that the bubbles are unlikely to buckle, and the impact is stored as elastic energy and repelled. Also, the production of cells having an aspect ratio of more than 5 is extremely difficult because of excessive deformation of the polyolefin resin.

The expansion ratio of the foam sheet is preferably 3 to 30 times. When the expansion ratio exceeds 30 times, the thickness of the cell wall becomes thin, and the compressive strength decreases. If the expansion ratio is less than 3 times, the compression modulus becomes too high, and the cost increases, which is not practical.

The foam sheets include those obtained by chemical foaming and those obtained by physical foaming.

The chemical foaming means that a thermal decomposition type chemical foaming agent which generates a decomposition gas by heating is dispersed in a polyolefin resin composition in advance, and the obtained foamable composition is temporarily converted into a sheet-like raw material (hereinafter, referred to as a sheet material). (Hereinafter referred to as a “foamable sheet”), and then heated to foam with a gas generated from a foaming agent. Representative examples of the thermal decomposition type chemical foaming agent include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide, 4,4-oxybis (benzenesulfonyl hydrazide) and the like. The amount of the chemical foaming agent is preferably 2 to 100 parts by weight of the resin composition.
-20 parts by weight.

Physical foaming means that a physical foaming agent is once dissolved in a polyolefin resin composition under high pressure, and then the obtained foamable composition is placed under normal pressure to generate a gas.
It can be produced by foaming. Examples of physical blowing agents include water, carbon dioxide, nitrogen, organic solvents, and the like.

The vehicle cushioning member of the present invention has an average value of the aspect ratio Dz / Dxy of the internal bubbles of 1.1 to 4,
A face material is laminated on at least one surface of a polyolefin resin foam sheet having a compression elastic modulus of 10 kgf / cm ² or more and a closed cell rate of 60% or more.

In the vehicle cushioning member of the present invention, the foam sheet has an average aspect ratio of 1.1 to 4 and a closed cell rate of 60.
% Is the same as that of the above-described vehicle member of the present invention except that it is not less than%.

The closed cell rate is the ratio of the closed cell shape in the foam sheet. If the closed cell rate is 0%,
It means that the open cell shape is 100%. For example, a conventional sponge substantially has an open cell structure, and thus has a closed cell rate of 0%, easily absorbs water, and as described above, reduces the durability of the sponge member due to water absorption. Since the composite foam of the present invention has a closed cell rate of 60% or more, it has a low water absorption rate and is suitable as a vehicle cushioning member. The closed cell rate is 60% or more, indicating a sufficiently low water absorption, but the preferred closed cell rate is 70% or more.

It is preferable that the water absorption of the vehicular cushioning member is 20% or less.

As the face material, a nonwoven fabric or a stretched sheet made of a polyolefin resin is preferable.

Next, a method for producing the foam sheet used in the present invention will be described.

The method for producing the above foam sheet is not particularly limited, but preferably, the modified polyolefin is melt-mixed with a polyolefin resin and a modifying monomer to obtain a modified polyolefin, and the modified polyolefin is added to 100 parts by weight of azodicarbonamide. 2-20 thermal decomposition type chemical blowing agents such as
Parts by weight, and once forming the resulting foamable resin composition into a sheet, the resulting foamable sheet is heated above the decomposition temperature of the thermal decomposition type chemical foaming agent and chemically foamed. is there.

The modifying monomer is a compound having two or more functional groups capable of radical reaction in the molecule. As the functional group, an oxime group, a maleimide group, a vinyl group,
Examples thereof include an allyl group and a (meth) acryl group. The modifying monomer is preferably a dioxime compound, a bismaleimide compound, divinylbenzene, an allyl polyfunctional monomer, or a (meth) acrylic polyfunctional monomer. Further, the modifying monomer may be a cyclic compound having two or more ketone groups in the molecule, such as a quinone compound.

By adopting the resin modification method as described above,
In spite of the low degree of crosslinking of the formed foamable sheet, it can be foamed at normal pressure.

The term "low cross-linking degree" as used herein generally means a gel fraction of 25% or less.

In general, the measurement of the gel fraction is represented by the weight ratio of the initial weight of the sample to the sample obtained by dissolving the sample in hot xylene at 120 ° C. for 24 hours and drying the gel component.

The foamable sheet obtained by using the modified resin as described above has a lower gel fraction than a sheet crosslinked by an electron beam or a sheet crosslinked by a thermal decomposition type chemical crosslinking agent. It can be re-melted and has excellent recyclability.

As a method for shaping the foamable sheet, in addition to extrusion molding, a method generally used in plastic molding such as press molding, blow molding, calendaring molding, injection molding and the like can be applied. From the viewpoint of productivity, a method in which the foamable resin composition discharged from the screw extruder is immediately shaped is preferable. According to this method, a continuous foamable sheet having a fixed width can be obtained.

The chemical foaming of the foamable sheet is usually carried out in a temperature range from the decomposition temperature of the thermal decomposition type chemical foaming agent to the thermal decomposition temperature of the thermoplastic resin. In particular, as a continuous foaming apparatus, in addition to a take-up foaming machine that foams while taking out a foam sheet at an outlet side of a heating furnace, a belt-type foaming machine, a vertical or horizontal foaming furnace, a hot-air bath, or a hot bath Oil baths, metal baths, salt baths, etc., which are used for foaming, are used.

A foam sheet comprising the above-mentioned spindle-shaped cells,
That is, in order to obtain a foam sheet in which the average value of the aspect ratio Dz / Dxy of the cells is 1.1 to 5, a face material having a strength capable of suppressing the in-plane foaming force of the sheet being foamed is used. Laminate on at least one side of the foamable sheet. This is because suppressing foaming in the in-plane two-dimensional direction at the time of foaming allows the foamable sheet to be foamed only in the thickness direction, and as a result, the bubbles of the foam sheet have the same length. This is because it becomes a spindle shape in which the axis is oriented in the thickness direction. The face material is not limited as long as it can withstand the foaming temperature of the foamable sheet, that is, the melting point temperature of the polyolefin resin or higher, and the decomposition temperature of the pyrolytic foaming agent or higher. For example, paper, cloth, It can be appropriately selected from wood, iron, non-ferrous metal, non-woven fabric, cold gauze, glass fiber, inorganic fiber and the like.

As the face material, it is preferable to use a non-woven fabric or a stretched sheet made of a polyolefin resin. In this case, it can be thermally fused with a polyolefin-based resin foam, and the obtained foam sheet has excellent shaping workability by heat and pressure.

The method of laminating the face material and the foam sheet is not particularly limited. When roughly classified, the following lamination before foaming, lamination during foaming, and lamination after foaming are possible.

Lamination before foaming: By laminating the face material on the foamable sheet in advance, the foam having flat cells of the present invention can be produced as described above.

Lamination during foaming: A face material is placed along the inner surface of a mold for injection foaming or the like, and a foaming resin is injected inside the mold to reduce the pressure in the mold or to reduce the thickness of the mold. By foaming the resin only in the thickness direction by expanding the resin in the direction, a shaped foam sheet is obtained at one time.

Lamination after foaming: A foam sheet is prepared in advance, and a face material is laminated thereon.

The means for laminating is not particularly limited, and broadly includes heat fusion and use of an adhesive. The face material can also be thermally fused to the foam via a primer.

Next, a case where a stretched sheet made of a polyolefin resin is used as a face material will be described.

A face material composed of a stretched sheet of polyolefin resin having a coefficient of linear expansion of 5.0 × 10 ⁻⁵ / ° C. or less (hereinafter, may be simply referred to as “face material”) can be used.
The above-mentioned face material may be used alone, but may be used in a laminated manner on another face material as described above. Further, as another face material, a Teflon (registered trademark) sheet having a good release property is laminated on a foamable sheet and foamed in the thickness direction. Then, the face material is peeled off from the foam, and the foam material is removed. A face material made of the above-mentioned stretched sheet made of polyolefin resin may be laminated on the release surface.

The coefficient of linear expansion of the stretched sheet made of polyolefin resin is 5 × 10 ⁻⁵ (1 / ° C.) or less, preferably 3 × 10 ⁻⁵ (1 / ° C.).
10 ⁻⁵ (1 / ° C.) or less, more preferably 2 × 10
⁻⁵ (1 / ° C.) or less and −2 × 10 ⁻⁵ (1 / ° C.) or more. Here, the coefficient of linear expansion is a scale indicating the rate at which the dimensions of a substance expand with temperature. As a method of measuring the coefficient of linear expansion, there is a method of precisely measuring the size of a substance during temperature rise by TMA (thermomechanical analysis). In the present invention, as shown in Examples described later, 5 ° C. And 8
The value calculated simply from the difference in dimensions at 0 ° C. is defined as the linear expansion coefficient.

The stretched sheet made of polyolefin-based resin is not particularly limited, but generally the linear expansion coefficient of the polyolefin-based resin sheet is larger than 5 × 10 ⁻⁵ (1 / ° C.).
This is subjected to a process such as stretching or rolling to have a coefficient of linear expansion of 5
A stretched sheet made of a polyolefin-based resin having a density of ^10-5 (1 / ° C) or less is used. In a stretched sheet made of a polyolefin-based resin subjected to such a treatment, the linear expansion coefficient decreases as the stretch ratio increases.

The foam sheet itself used in the present invention comprises:
It shows a coefficient of linear expansion of approximately 5 × 10 ⁻⁵ to 15 × 10 ⁻⁵ (1 / ° C.), but by laminating the above face material on at least one surface of the foam sheet, thermal expansion and contraction is suppressed, and as a result, A foam sheet having a small expansion coefficient is obtained.

Further, since the stretched sheet made of a polyolefin-based resin has an increased draw ratio in order to reduce its linear expansion coefficient, the tensile strength and the tensile modulus in the stretch direction are also increased. Therefore, by laminating this on a polyolefin-based resin foam, the bending rigidity and bending strength of the obtained foam sheet can be dramatically improved.

When the stretched sheet made of a polyolefin resin has a coefficient of linear expansion exceeding 5 × 10 ⁻⁵ (1 / ° C.), the thermal expansion and contraction of the foam is too large to suppress the thermal expansion and contraction of the foam. Rigidity decreases.

The polyolefin resin constituting the stretched sheet made of polyolefin resin is not particularly limited, and examples thereof include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and homopolypropylene.
Block polypropylene or the like can be used. In consideration of the elastic modulus after stretching, it is preferable to use polyethylene having a high theoretical elastic modulus, and high density polyethylene having high crystallinity is particularly preferable.

The molecular weight of the polyolefin for the stretched sheet is not particularly limited, but preferably, a polyolefin having a weight average molecular weight of 500,000 or less is used. If the weight average molecular weight exceeds 500,000, it is difficult to form a stretched raw sheet when obtaining a stretched sheet made of a polyolefin-based resin, and the stretchability is deteriorated, so that stretching at a high magnification may not be possible. The lower limit of the weight average molecular weight of the polyolefin resin is not particularly limited, but may be 10
If it is smaller than 10,000, the resin itself becomes brittle, and the stretchability may be impaired. Therefore, polyolefins having a weight average molecular weight in the range of 100,000 to 500,000, particularly high density polyethylene, are preferred.

As a method for measuring the weight average molecular weight,
After dissolving the sample in a heated solvent such as o-dichlorobenzene, the solution is injected into a column, and the elution time is measured.
A method of measuring by a so-called gel permeation chromatography method (high-temperature GPC method) is generally used,
Also in this specification, the weight average molecular weight measured by this method is described.

In consideration of the above range of the weight average molecular weight in view of the melt flow rate (hereinafter abbreviated as MI), those having MI of about 0.1 to 20/10 minutes are preferable. If the MI is out of this range, high-magnification stretching may be difficult. The melt flow rate is defined as JI
An index indicating the melt viscosity of a thermoplastic resin limited to SK6760.

Next, a method for producing a polyolefin resin stretched sheet used as a face material of the foam sheet used in the present invention will be described.

The method for producing a stretched sheet of polyolefin resin having a coefficient of linear expansion of 5 × 10 ⁻⁵ (1 / ° C.) or less is not particularly limited, but it is preferable to subject the polyolefin resin sheet to a treatment such as stretching or rolling. .

In obtaining the above-mentioned stretched sheet made of polyolefin-based resin, a crosslinking aid, a photo-radical polymerization initiator and the like may be added to the polyolefin, if necessary. Examples of the crosslinking auxiliary include polyfunctional monomers such as triallyl cyanurate, trimethylolpropane triacrylate, and diallyl phthalate, and examples of the photoradical polymerization initiator include benzophenone, thioxanthone, and acetophenone. it can. The amount of these crosslinking aids and radical photopolymerization initiators to be added is not particularly limited. However, in order to promptly proceed with crosslinking, the polyolefin resin 100 constituting the stretched sheet made of polyolefin resin is usually used. 1 part by weight
It is preferably in the range of 0 to 2.0 parts by weight.

The method for obtaining the polyolefin-based resin sheet before stretching is not particularly limited, and a method in which the above-mentioned polyolefin-based resin is plasticized by an extruder or the like, extruded into a sheet through a sheet die, and cooled. can do. The thickness of the polyolefin-based resin sheet before stretching is preferably in the range of 0.5 to 4 mm. If it is less than 0.5 mm, the sheet thickness after stretching is too thin, and the strength may not be sufficient during handling.
If it exceeds 4 mm, stretching may be difficult.

When the polyolefin resin sheet before stretching obtained as described above is stretched to obtain a stretched sheet made of polyolefin resin, the stretching ratio is set so as to satisfy the above-mentioned coefficient of linear expansion. Specifically, the stretching ratio is in the range of 5 to 40 times, preferably 20 to 40 times. If the stretching is less than 5 times, regardless of the type of the polyolefin-based resin, the coefficient of linear expansion does not decrease and the effect of increasing the mechanical strength (tensile properties) may be small.
If the stretching ratio exceeds 40 times, it may be difficult to control the stretching operation.

The stretching temperature for obtaining a stretched sheet made of polyolefin resin is not particularly limited,
The temperature is preferably in the range of 5 to 120 ° C. When the temperature exceeds 120 ° C., the sheet is easily cut, and it may be difficult to perform high-magnification stretching.

Although the stretching method is not particularly limited, a usual uniaxial stretching method, in particular, a roll stretching method is used. The roll stretching method is a method in which a raw material to be stretched is sandwiched between two pairs of rolls having different speeds, and the raw material is stretched while being heated. The molecular stretching can be strongly performed only in the uniaxial stretching direction. In this case, the speed ratio of the two pairs of rolls is the stretching ratio.

In the case of a relatively thick sheet, smooth stretching may be difficult only by the roll stretching method. In such a case, roll rolling may be performed prior to roll stretching. Roll rolling process, by inserting a stretched raw material thicker than the interval between the rolling rolls between a pair of rolls rotating in opposite directions, reducing the thickness of the raw material and simultaneously elongating in the length direction. Done. Since the sheet subjected to the roll rolling process has been subjected to the orientation process in advance,
By the next roll stretching, the film is smoothly stretched in the uniaxial direction.

In order to achieve a predetermined stretching temperature in the stretching step, the preheating temperature, the roll temperature and / or the ambient temperature of the sheet may be adjusted.

The above-mentioned stretched sheet made of a polyolefin resin may be subjected to a cross-linking treatment in order to increase heat resistance or to increase heat resistance and creep resistance of a final polyolefin molded article. Crosslinking can be performed by electron beam irradiation or ultraviolet irradiation.

The amount of electron beam irradiation varies depending on the composition and thickness of the stretched polyolefin sheet used, but is usually 1 to 20 Mrad, preferably 3 to 10 Mrad. In the case of crosslinking by electron beam irradiation, if a crosslinking aid is added to the stretched polyolefin sheet, the crosslinking proceeds smoothly.

The irradiation amount of ultraviolet light is usually 50 to 800 mW
/ Cm ² , preferably 100 to 500 mW / cm ² . In the case of crosslinking by ultraviolet irradiation, crosslinking can be easily performed by adding a photopolymerization initiator or a crosslinking assistant.

The degree of cross-linking is preferably such that the gel fraction determined by a measuring method described later is about 50 to 90%.

The method of laminating the face material composed of the stretched sheet made of the polyolefin resin on the polyolefin resin foam sheet is not particularly limited, and examples thereof include adhesion with an adhesive and heat fusion by heating. It is preferably used.

The method for producing a foam sheet by heat fusion is not particularly limited. In the case of chemical foaming, it is roughly classified as follows.

(1) A face material made of a stretched sheet made of a polyolefin resin is laminated on at least one surface of the foamable polyolefin resin sheet, and then heated and foamed.

(2) At least one surface of the foamed polyolefin resin sheet is laminated with another face material for suppressing foaming in the in-plane direction, and after heating and foaming, at least one of the obtained polyolefin resin foam sheets is obtained. On one side, a face material composed of a stretched sheet made of a polyolefin resin is laminated.

(3) A face material made of a stretched sheet made of a polyolefin resin is laminated on the polyolefin resin foamable sheet during heating and foaming.

The method (1) can be carried out if the polyolefin-based resin stretched sheet does not undergo thermal deformation at the temperature at which the polyolefin-based resin foamable sheet is heated and foamed.
The foaming temperature of the polyolefin resin foamable sheet is usually 1
Since the temperature is about 80 to 250 ° C., the method (2) or (3) is preferably used.

When the polyolefin-based resin foam sheet and the polyolefin-based resin stretched sheet are heat-sealed, a surface treatment or a primer may be used. A method in which a polyolefin-based resin film having a melting point equal to or lower than the temperature at which the stretched sheet made of a polyolefin-based resin is thermally deformed is preferably used between the two.

The laminating direction of the stretched sheet made of a polyolefin resin is not particularly limited, but the mechanical properties in the stretched direction are particularly improved. Alternatively, it is preferable to stack the layers at other angles. Further, the number and thickness of the sheets to be laminated are appropriately determined according to the intended mechanical properties and the like.

The heating and pressurizing conditions for heat fusion are as follows:
Since it depends on the polyolefin resin stretched sheet to be used, it cannot be unambiguously determined.
A pressure in the range of kg / cm ² and a temperature below the melting point of the polyolefin resin are preferred. If the pressure is outside the above range, the shape of the laminate may be disturbed during molding, and if the heating temperature at the time of bonding exceeds the melting point of the polyolefin resin, the shape of the laminate is disturbed due to shrinkage or the like during molding. And may adversely affect the linear expansion coefficient.

The laminate obtained as described above is lightweight, has high compressive strength and bending rigidity, has high shock absorption and dimensional stability, and has a high closed cell rate and a high water absorption rate. Since it is low, as a vehicle member, for example, a shock-resistant vehicle member such as an under tray under an engine; a door core material, a bumper core material, an engine spacer, a body pillar, a locker, a bonnet structure material, various frames, Further, it can be suitably used as a buffer member for vehicles such as a bumper spring for suspension.

(Function) In the vehicle member of the present invention, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 5
Since the face material is laminated on at least one surface of the polyolefin resin foam sheet having a compression elastic modulus of 10 kgf / cm ² or more, the foam shape of the polyolefin resin foam sheet is in the sheet thickness direction. For the compressive force, a force is applied in the major axis direction of the spindle-shaped bubble, so that it exhibits high compressive strength, and for a load exceeding the compressive yield point, the bubble buckles, Can absorb impact energy. Therefore, it can be suitably used as an impact vehicle member.

When a nonwoven fabric or a stretched sheet made of a polyolefin resin is used as the face material, the stretched sheet made of the polyolefin resin has a large tensile elastic modulus and a small linear expansion coefficient, and therefore has a large flexural modulus. A vehicle member having a small linear expansion coefficient can be obtained. Further, since the face material made of this sheet is mainly made of a thermoplastic resin, it can be subjected to secondary shaping by heat.

In the vehicle cushioning member of the present invention, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 4.0.
Since the polyolefin resin foam sheet having a compression elastic modulus of 10 kgf / cm ² or more and a closed cell rate of 60% or more has a face material laminated on at least one surface, the above polyolefin resin foam The bubble shape of the body sheet shows a high compressive strength because a force is applied in the long axis direction of the spindle-shaped bubble with respect to the compressive force in the sheet thickness direction, and at a load exceeding the compressive yield point. The
The buckling of the bubbles can absorb impact energy. In addition, the closed cell rate is high and the water absorption rate is low. In particular,
Like bumper springs for automobile suspensions,
When a polyolefin resin foam sheet is used for a buffer member exposed to water such as rainwater under high compression conditions,
Low water absorption makes it hard to corrode and can be recycled.

[0090]

EXAMPLES The present invention will be described more specifically with reference to examples.

Example 1 (1) Preparation of Modified Polyolefin Resin As a modifying screw extruder, a co-rotating twin screw extruder (Model “BT” manufactured by Plastic Engineering Laboratory Co., Ltd.)
40 "). It has a self-wiping double-start screw with an L / D of 35 and a D of 39 mm.
Cylinder barrels from upstream to downstream of extruder
Consisting of a barrel, the die was a three-hole strand die, and a vacuum vent was installed in the fourth barrel to collect volatiles.

The operating conditions are as follows.

Cylinder barrel set temperature: 1st barrel; 180 ° C 2nd to 6th barrel; 220 ° C die; 220 ° C Screw rotation speed: 150 rpm

First, the polyolefin resin is charged into the extruder from the rear end hopper into the modifying screw extruder having the above structure, and the mixture of the modifying monomer and the organic peroxide is injected into the extruder from the third barrel. These were melt-mixed to obtain a modified resin. At this time, the volatile components generated in the extruder were evacuated by a vacuum vent.

The polyolefin resin is a polypropylene random copolymer (manufactured by Nippon Polychem Co., Ltd., product number “EX6”,
MI = 1.8 / 10 minutes, density: 0.9 g / cm ³ ), and the supply amount was 10 kg / h. The modifying monomer was divinylbenzene, and the supply amount was 0.5 parts by weight based on 100 parts by weight of the polyolefin resin. The organic peroxide is 2,5-dimethyl-2,5-di (t
-Butylperoxy) hexyne-3, and the supply amount was 0.1 parts by weight based on 100 parts by weight of the polyolefin resin.
Parts by weight were used.

The modified resin obtained by melt-mixing the polyolefin resin, the modifying monomer and the organic peroxide was discharged from a strand die, cooled with water, and cut with a pelletizer to obtain pellets of the modified resin.

(2) Preparation of foamable resin composition The screw extruder for kneading the foaming agent is a co-rotating twin screw extruder (Model "TEX-44", manufactured by Nippon Steel Works, Ltd.).
, Which has a self-wiping double-start screw with an L / D of 45.5 and a D of 47 mm. The cylinder barrel comprises first to twelfth barrels from upstream to downstream of the extruder, and the forming die is a 7-hole strand die.
The temperature setting categories are as follows.

The first barrel is constantly cooled. The first zone; the second to fourth barrels; the second zone; the fifth to eighth barrels; the third zone; the ninth to twelfth barrels; the fourth zone;

A side feeder is installed in the sixth barrel to supply the foaming agent, and the eleventh barrel is used to collect volatile components.
A vacuum vent is installed in the barrel. The operating conditions are as follows.

[0100] -Screw rotation speed: 40 rpm

The modified resin obtained as described above and a homo-type polypropylene (manufactured by Nippon Polychem Co., Ltd., product number “FY4”, MI = 5.0 / 10 min, density: 0.9 g /
cm ³ ) were supplied to the blowing agent kneading screw extruder at a supply rate of 10 kg / h. A foaming agent was supplied to the extruder from the side feeder. The blowing agent is azodicarbonamide, and the supply amount is 1.0 kg /
h. Thus, a foamable resin composition was obtained by kneading the modified resin and the foaming agent.

(3) Preparation of Polyolefin Resin Foamable Sheet This foamable resin composition was extruded from a T-die and had a width of 350
A polyolefin resin foamable sheet having a size of 0.5 mm × 0.5 mm was obtained.

(4) Preparation of Foamable Laminate Sheet A nonwoven fabric made of polyethylene terephthalate (trade name “Spanbond Equle 6301A” manufactured by Toyobo Co., Ltd., weighing 3) is provided on both sides of the polyolefin resin foam sheet.
0 g / m ² ), and the temperature is adjusted to 18 using a press molding machine.
Press molding was performed at 0 ° C. and a pressure of 19.6 MPa to obtain a foamed laminated sheet.

(5) Foaming Remove the edges from the obtained foamable laminated sheet, and remove
A 00 mm square sample was obtained. This sample is 23
The foamed composite sheet was foamed by heating in an oven at 0 ° C. for about 5 minutes to obtain a 5 mm-thick laminate of the foam sheet and the face material.

(Example 2) As in Example 1, (1) preparation of a modified polyolefin resin, (2) preparation of a foamable resin composition, (3) preparation of a polyolefin resin foam sheet,
A polyolefin resin foam sheet was obtained through the steps of (4) preparation of a foamable composite sheet and (5) foaming.

(6) Preparation of stretched sheet made of polyolefin resin 1) Preparation of extruded sheet High density polyethylene (manufactured by Mitsubishi Chemical Corporation, product number “HY54”)
0 ", MI = 1.0 / 10 min, melting point 133 ° C., weight average molecular weight 300,000), 100 parts by weight of benzophenone (photopolymerization initiator), and 1 part by weight of this compound.
mm at a resin temperature of 200 ° C using a twin screw extruder.
It was extruded into a sheet by a die and cooled by a cooling roll to obtain an unstretched sheet. 2) Rolling / Crosslinking The unstretched sheet was heated at a surface temperature of 100 ° C.
Using an inch roll (manufactured by Kodaira Mfg. Co., Ltd.), roll rolling is performed at a rolling ratio of 8 times, and then the obtained rolled sheet is fed out with a roll at a feeding speed of 2 m / min. It was taken up with a roll at a speed of 8 m / min, stretched by a factor of 4 and rolled up. Then, the obtained sheet was irradiated with a high-pressure mercury lamp from both sides for 5 seconds to perform a crosslinking treatment. Finally, the obtained sheet was subjected to a relaxation treatment at 130 ° C. for 1 minute under no tension.

The stretched sheet obtained through the above operation had a size of 50 mm in width and 0.09 mm in thickness, and was transparent. The total stretching ratio of this sheet is about 30 times, the coefficient of linear expansion is -1.4 × 10 ^-5 , and the melting point of this stretched sheet [peak temperature in DSC (differential scanning calorimeter)].
Was 139 ° C., and the tensile modulus was 15,000 MPa. The tensile modulus and coefficient of linear expansion of each sample were measured in accordance with the tensile test method of JIS K7113.

3) Lamination and heat fusion As shown in FIG. 2, a low-density polyethylene film (manufactured by Mitsubishi Chemical Corporation, product number “UF230”, thickness 30 μm) is provided on both sides of the polyolefin resin foam sheet obtained earlier.
, And the above-mentioned stretched sheet made of a polyolefin-based resin was further disposed thereon to obtain a laminated product of three types and five layers. In hand press molding machine, temperature 125 ° C, pressure 98kPa
For 2 minutes, and then water-cooled with a water-cooled press (pressure 98 kPa) to obtain a 5 mm-thick laminate of a foam sheet and a face material. I got

Example 3 A laminate of a foam sheet and a face material was obtained in the same manner as in Example 1 except that the thickness of the polyolefin resin foamable sheet was 1 mm.

Comparative Example 1 2.15 parts by weight of a 50% by weight aqueous solution of a fatty acid sulfonate was mixed with 124 parts by weight of a prepolymer (polyester adipate-based glycol and 1,5-
(A reaction product with naphthylene diisocyanate), and the resulting mixture was charged into a mold and subjected to heat treatment to obtain a sponge molded product.

Comparative Example 2 80 parts by weight of toluene was mixed with 20 parts by weight of a molten fluorine-based water repellent, and the obtained water repellent solution was spray-coated on the inner surface of a mold. Then, a sponge molded product was obtained in the same manner as in Comparative Example 1.

Evaluation test of foam sheet The foam sheets obtained in the above Examples and Comparative Examples were evaluated for the following items. The results are summarized in Table 1.

Apparent density: Apparent density was measured based on JIS K6767.

Expansion ratio: After the face material was scraped off from the foam sheet with a cutter, the expansion ratio of the foam was measured in accordance with JIS K6767.

Bubble shape (average aspect ratio): The foam sheet was cut in the thickness direction (z direction), and a 15-fold enlarged photograph was taken while observing the center of the cross section with an optical microscope.
The Dz and Dxy of all the bubbles in the photograph were measured with calipers, Dz / Dxy was calculated for each bubble, and the number average of Dz / Dxy for 100 bubbles was calculated to obtain the average aspect ratio. However, during measurement, Dz (actual diameter) is 0.05 mm
The following bubbles and bubbles of 10 mm or more were excluded.

Compressive modulus According to JIS K7203, test speed 10 mm / mi
n was measured and the compression modulus was calculated.

The closed cell rate The sum of the volumes of the resin and the closed cells (referred to as A (cm ³ )) was measured by an air-comparison hydrometer, and the closed cell rate was calculated by the following equation.

(A−W / ρ) / [(W + B) / ρ _W −W /
ρ] where W: foam sheet weight (g) ρ: resin density (g / cm ³ ) = 0.9 B: buoyancy (g) ρ _W : density of water (g / cm ³ ) = 1

Water absorption rate A water-absorbing rate at a compression rate of 0 to 70% was repeated twice per second while spraying water on the molded article in a mist state. It was measured.

[0120]

[Table 1]

[0121]

According to the present invention, it is possible to provide a vehicle member comprising a lightweight and high-rigidity polyolefin-based resin foam sheet and a vehicle cushion member exhibiting even lower water absorption. . Further, when a material made of a polyolefin resin is used as the face material, the vehicle member and the vehicle cushioning member according to the present invention are excellent in recyclability.

[Brief description of the drawings]

FIG. 1A is a schematic perspective view of a spindle-shaped bubble, and FIG.
1B is an enlarged schematic view of a part of a cross section parallel to the z direction in FIG.

FIG. 2 is a schematic diagram showing a laminated configuration of a second embodiment.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4F100 AH01 AH02 AH03 AK03A AK03B AK03C AK05 AK06 AK07 AK42 AL02 AL06 AT00B AT00C BA03 BA06 CA01 CA30 DG15B DG15C DJ01A DJ02A EH17 EJ05 EJ17 JEJBJAJJEJB EJ37 EJ37 EJ37

Claims (6)

[Claims] 1. An aspect ratio Dz / Dx of an inherent bubble.
The average value of y is 1.1 to 5, and the compression modulus is 10 kgf /
A vehicle member characterized in that a face material is laminated on at least one side of a polyolefin resin foam sheet having a size of ² cm2 or more. 2. The vehicle member according to claim 1, wherein the vehicle member is a shock-resistant vehicle member. 3. The vehicle member according to claim 1, wherein the face material is a nonwoven fabric or a stretched sheet made of a polyolefin resin. 4. An aspect ratio Dz / Dx of an inherent bubble.
The average value of y is 1.1 to 4.0, and the compression modulus is 10 kg.
A cushioning member for a vehicle, wherein a face material is laminated on at least one surface of a polyolefin-based resin foam sheet having an f / cm ² or more and a closed cell rate of 60% or more. 5. The cushioning member for a vehicle according to claim 4, wherein the water absorption rate is 20% or less. 6. The cushioning member for a vehicle according to claim 4, wherein the face material is a nonwoven fabric or a stretched sheet made of a polyolefin resin.