JP2001301078A - Polyolefinic resin composite foam, and vehicular member and shock absorbing member consisting of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polylefinic resin composite foam having lightweight properties and high rigidity and based on a polyolefinic resin, and a vehicular member and a shock absorbing member consisting of the same. SOLUTION: The polyolefinic resin composite foam is obtained by laminating a surface material consisting of an inorganic long fiber reinforced thermoplastic resin sheet on at least the single surface of a polyolefinic resin foam sheet containing cells of which the aspect ratio Dz/Dxy is 1.1-4.0 on an average and having an expansion ratio of 3-30 times. The vehicular member and the shock absorbing member consist of the polyolefinic resin composite foam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight and highly rigid polyolefin resin composite foam, and to a vehicle member and a shock absorbing member made of the foam.

[0002]

2. Description of the Related Art The core materials of interior and exterior materials of automobiles are:
From the viewpoint of easy attachment to other members, rigidity and shapeability are required. Conventionally, as such a core material, a hard board core material obtained by shaping a mixture of a wood fiber, a reinforcing material and a binder resin with a molding die has been used. For example, Japanese Unexamined Patent Publication No. Hei 4-363214 discloses that natural wood or synthetic fiber 20 to 75 parts by weight, glass fiber 8 to 50 parts by weight, an appropriate amount of thermosetting resin, There has been proposed a deep-drawing molding material obtained by mixing a thermoplastic resin in accordance with the requirements.

[0003]

However, the above-mentioned hard board core material changes in size due to moisture absorption, and has a specific gravity of 0.8.
There is a disadvantage that the above is heavy.

[0004] In the automotive industry, in consideration of the recyclability of used products, there has been a movement to unify the materials using thermoplastic resins, and polyolefin resins represented by polypropylene having high heat resistance have attracted attention. Furthermore, in order to protect the human body from accidents such as collisions, the importance of shock absorbing performance of members has been emphasized.

However, when a foam made of a polyolefin resin alone is used as the material of the core material, the specific gravity of the resin is about 0.9, which is heavy, and the core material changes in size due to temperature.
There is a problem.

A composite in which a face material made of inorganic fibers is laminated on both surfaces of a polyolefin resin foam is lightweight and has dimensional stability. However, since the foam has low compressive strength, the flexural rigidity of the composite is low. However, it is difficult to absorb energy of a certain degree or more because of its fluffy nature and low impact absorption.

An object of the present invention is to solve the above-mentioned problems,
It is an object of the present invention to provide a lightweight and highly rigid composite foam made of a polyolefin resin, a vehicle member and a shock absorbing member made of the foam.

[0008]

According to the first aspect of the present invention,
An inorganic long fiber reinforced thermoplastic is provided on at least one surface of a polyolefin resin foam sheet having an average value of the aspect ratio Dz / Dxy of the internal bubbles of 1.1 to 4.0 and an expansion ratio of 3 to 30 times. A polyolefin-based resin composite foam (hereinafter, referred to as a “first composite foam”), wherein face materials made of a resin sheet are laminated.

The invention according to claims 2 and 3 is a vehicle member and a shock absorbing member comprising the above-mentioned polyolefin resin composite foam.

According to the fourth and fifth aspects of the present invention, the average value of the aspect ratio Dz / Dxy of the internal bubbles is 1.1 to 1.1.
A face material comprising a stretched polyolefin-based resin sheet having a linear expansion coefficient of 5.0 × 10 ⁻⁵ / ° C. or less on at least one surface of a polyolefin-based resin foam sheet having a 4.0 and an expansion ratio of 3 to 30 times. Polyolefin-based resin composite foam (hereinafter referred to as "second composite foam")
And a shock absorbing member.

The polyolefin as a main component of the polyolefin resin in the present invention is a homopolymer of an olefinic monomer or a copolymer of a main component olefinic monomer and another monomer, and is not particularly limited. 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-propylene-diene Copolymers containing ethylene as a main component such as a terpolymer, an ethylene-butene copolymer, an ethylene-vinyl acetate copolymer, and an ethylene- (meth) acrylate copolymer are exemplified. A combination of two or more It may be.

As the polyolefin which is the main component of the polyolefin resin in the present invention, one or a combination of two or more of the above-mentioned polyethylenes and polypropylenes is preferable.

The polyolefin resin in the present invention refers to a resin composition in which the proportion of the polyolefin is 70 to 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

The term "aspect ratio" used in the present specification is the number (arithmetic) average value of the ratio of the maximum diameter in the fixed direction in the cells in the foamed thermoplastic resin sheet. Ratio Dz with diameter Dxy in the direction
/ 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 first and second composite foams, functions as having high rigidity in the elastic deformation region with respect to the pressure in the z-direction. However, when a load or impact exceeding the compressive yield stress is applied, the bubbles buckle, thereby absorbing the energy of the load or impact, and thus function as a shock absorbing material.

Further, since the compressive strength and elastic modulus are increased, when a high-tensile face material is laminated on the surface in the xy direction, 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 composite foam according to the present invention is 1.1 to 4.0, preferably 1.3 to 3.0.
It is. When the aspect ratio is less than 1.1, the cells become substantially spherical, and the improvement in compressive strength due to the spindle shape cannot be obtained. As a result, the flexural rigidity of the composite foam decreases, and the shock absorption decreases. Aspect ratio of 4.0
If it exceeds, 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 exceeding 4.0 is extremely difficult because of excessive deformation of the polyolefin resin.

The expansion ratio of the composite foam according to the present invention is 3 to
It is 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 foams of the composite foam according to the present invention include those obtained by chemical foaming and those obtained by physical foaming.

In the former foam, a thermally decomposable chemical blowing agent which generates a decomposed gas by heating is dispersed in a polyolefin resin composition in advance, and the obtained foamable composition is temporarily formed into a sheet-like raw material. After shaping, it can be manufactured by heating and foaming with a gas generated from a foaming agent. Representative examples of the thermal decomposition type chemical blowing agent include azodicarbonamide, benzenesulfonyl hydrazide, dinitrosopentamethylenetetramine, toluenesulfonyl hydrazide,
4,4-oxybis (benzenesulfonyl hydrazide)
And the like. The amount of the chemical foaming agent is 10
It is preferably 2 to 20 parts by weight based on 0 parts by weight.

The latter foam is obtained by temporarily dissolving a physical foaming agent in a polyolefin resin composition under high pressure,
It can be produced by placing the obtained foamable composition under normal pressure to generate gas and foaming. Examples of physical blowing agents include water, carbon dioxide, nitrogen, organic solvents, and the like.

Next, a method for producing a composite foam according to the present invention will be described.

The method for producing the composite foam of the present invention 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. 2 to 20 thermal decomposition type chemical blowing agents such as amide
Parts by weight are dispersed and the obtained foamable resin composition is once formed into a sheet-like raw material, and then the obtained foamable sheet is heated to a temperature equal to or higher than the decomposition temperature of the thermal decomposition type chemical foaming agent to perform chemical foaming. It is a way to make it.

The modifying monomer used in the method of the present invention is a compound having two or more functional groups capable of undergoing a radical reaction in a molecule. Examples of the functional group include an oxime group, a maleimide group, a vinyl group, 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,
Despite the low degree of cross-linking of the molded foam sheet,
This can be foamed at normal pressure.

Here, the low degree of crosslinking means that the gel fraction is 2%.
The range is within 5%.

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 cross-linked by an electron beam or a sheet cross-linked by a thermal decomposition type chemical cross-linking agent. It can be re-melted and has excellent recyclability.

As a method for shaping the sheet-like foamable raw material,
In addition to extrusion molding, methods commonly used in plastic molding, such as press molding, blow molding, calendaring molding, and injection molding, can be applied, but the foamable resin composition discharged from the screw extruder can be used immediately after The shaping method is preferable from the viewpoint of productivity. According to this method, a continuous raw sheet having a fixed width can be obtained.

The chemical foaming of the sheet-form raw material 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 at the 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 An oil bath, a metal bath, a salt bath or the like for foaming is used.

The above-mentioned foam composed of spindle-shaped cells, that is, the average value of the aspect ratio Dz / Dxy of the cells is 1.1.
In order to obtain a foam having a thickness of up to 4.0, a face material having a strength capable of suppressing an in-plane foaming force of the raw fabric during foaming is laminated on at least one surface of the raw fabric before foaming. This is because by suppressing foaming in a two-dimensional direction in the plane during foaming, it becomes possible to foam the raw material only in the thickness direction. This is because it becomes a spindle shape oriented in the thickness direction. This face material has a foaming temperature of the raw material, that is, the melting point temperature of the polyolefin resin or higher.
Any material that can withstand the environment at or above the decomposition temperature of the pyrolytic foaming agent may be used. For example, it can be appropriately selected from paper, cloth, wood, iron, non-ferrous metal, nonwoven fabric, cold gauze, glass fiber, inorganic fiber, and the like. .

To construct the first composite foam, a face material made of an inorganic long fiber reinforced thermoplastic resin sheet is used, and to construct the second composite foam, the linear expansion coefficient is 5.0 × 10 ^-5. /
A face material composed of a stretched polyolefin resin sheet at a temperature of not more than ° C is used. The above-mentioned inorganic long fiber reinforced thermoplastic resin sheet surface material and the above-mentioned polyolefin resin stretched sheet surface material may be used alone, but may also be used in a laminated form on other surface materials as described above. Also, as another face material, a Teflon (registered trademark) sheet having good releasability is laminated on the raw material and foamed in the thickness direction, and then the face material is peeled off from the foam to remove the foam. The face material of the inorganic long fiber reinforced thermoplastic resin sheet or the face material of the stretched polyolefin resin sheet may be laminated on the surface.

The inorganic long fiber reinforced thermoplastic resin sheet used as a face material in the first composite foam will be described.

The material of the inorganic long fibers for reinforcing the sheet of the face material of the first composite foam is not particularly limited, and for example, glass, carbon (graphite), boron, or the like is used. The inorganic long fibers can take the form of spun long fibers, for example. Such long fibers can enhance the strength of the resin sheet, suppress thermal expansion and contraction, and have good shock absorption.

The form of the long fiber is not particularly limited, and is appropriately determined in consideration of desired rigidity, heat shapeability, and the like. Considering the rigidity and the like, the form of roving or yarn is preferable. Rovings and yarns are woven, braided, or matted non-directionally, depending on the desired physical properties. Examples of weaving methods include plain weave, plain plain weave, twill weave, satin weave, and blind weave.

The method for producing a thermoplastic resin sheet reinforced with inorganic long fibers is not particularly limited, but a resin impregnated in an inorganic long fiber mat or sheet, a resin sheet laminated, or an inorganic long fiber and heat An inorganic long fiber reinforced thermoplastic resin sheet can be obtained by applying heat and pressure to integrate the mixed mat or sheet of the plastic resin.
Heat or pressure may be applied at any stage, such as before foaming, during foaming, or during lamination after foaming, and an efficient manufacturing process can be selected.

The weight ratio of the inorganic long fibers to the thermoplastic resin is also determined appropriately according to the desired physical properties. From the viewpoint of rigidity and heat shaping properties, the weight ratio of the inorganic long fibers is 10 to 80%. Is preferred.

Since the face material is made of an inorganic long fiber reinforced thermoplastic resin sheet, it can be heat-sealed with a polyolefin resin foam, and the obtained composite foam can be applied by heat or pressure. Excellent in formability.

The method of laminating the face material comprising the inorganic long fiber reinforced thermoplastic resin sheet and the polyolefin resin foam 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 face materials in advance on a raw material, 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, for example, by expanding in the direction, a shaped composite foam is obtained at one time.

Lamination after foaming: A polyolefin resin foam 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, the face material of the second composite foam will be described.

The face material constituting the second composite foam is made of a stretched polyolefin resin sheet. The coefficient of linear expansion of the stretched polyolefin resin sheet is 5 × 10 ^−5.
(1 / ° C.) or less, preferably 3 × 10 ⁻⁵ (1 / ° C.) or less, more preferably 2 × 10 ⁻⁵ (1 / ° C.) or less, and −2 × 10 ⁻⁵ (1 / ° C.) or more It is. 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, TM
A (mechanical analysis) is a method for precisely measuring the size of a substance during temperature rise. In the present invention, however, a simple method is used based on the difference between the sizes at 5 ° C. and 80 ° C., as shown in Examples described later. Is calculated as the linear expansion coefficient.

The stretched polyolefin resin sheet is not particularly limited, but generally has a coefficient of linear expansion greater than 5 × 10 ⁻⁵ (1 / ° C.), and is subjected to a treatment such as stretching or rolling. 5 × linear expansion coefficient
A stretched polyolefin-based resin sheet of 10 ⁻⁵ (1 / ° C.) or less is used. In the stretched polyolefin-based resin sheet subjected to such a treatment, the linear expansion coefficient decreases as the stretching ratio increases.

The foam itself of the second composite foam exhibits a linear expansion coefficient of about 5 × 10 ⁻⁵ to 15 × 10 ⁻⁵ (1 / ° C.), but the above-mentioned face material is laminated on at least one surface of the foam. By doing so, thermal expansion and contraction is suppressed, and as a result, a composite foam having a small linear expansion coefficient is obtained.

The stretched polyolefin-based resin sheet has a large stretch ratio in order to reduce its linear expansion coefficient, and therefore has a large tensile strength and tensile modulus in the stretch direction. Therefore, by laminating this on a polyolefin-based resin foam, the bending rigidity and bending strength of the obtained composite foam can be dramatically improved.

When the coefficient of linear expansion of the stretched polyolefin resin sheet exceeds 5 × 10 ⁻⁵ (1 / ° C.), the thermal expansion and contraction of the foam is too large, and the thermal expansion and contraction of the foam cannot be suppressed. Decrease.

The polyolefin resin constituting the stretched polyolefin resin sheet is not particularly limited. For example, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, homopolypropylene, block polypropylene or the like may be used. Can be. 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 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 polyolefin-based resin sheet, and the stretchability also deteriorates, making it impossible to stretch at a high magnification.
The lower limit of the weight average molecular weight of the polyolefin resin is not particularly limited, but if it is less than 100,000, 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 an MI of about 0.1 to 20 are preferable. If the MI is out of this range, high-magnification stretching may be difficult. In addition, the melt flow rate is JISK
An index indicating the melt viscosity of a thermoplastic resin limited to 6760.

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

The method for producing a stretched polyolefin resin sheet 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 polyolefin-based resin sheet, a crosslinking aid, a photoradical polymerization initiator, and the like may be added to the polyolefin, if necessary. Examples of the crosslinking assistant include polyfunctional monomers such as triallyl cyanurate, trimethylolpropane triacrylate, and diallyl phthalate.As the photoradical polymerization initiator, benzophenone, thioxanthone,
Acetophenone and the like can be exemplified. The amount of these crosslinking aids and photo-radical polymerization initiators to be added is not particularly limited. However, in order to promptly proceed with crosslinking, the amount of the polyolefin-based resin constituting the stretched polyolefin-based resin sheet is usually 100% by weight. 1.0-2.
It is preferably in the range of 0 parts by weight.

The method for obtaining the polyolefin-based resin sheet before stretching is not particularly limited, and a method is employed in which the above-described polyolefin-based resin is plasticized by an extruder or the like, and then 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 polyolefin resin sheet, 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 the stretched polyolefin-based resin sheet is not particularly limited.
It is preferable that the temperature be in the range of 120 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, roll temperature and / or ambient temperature of the sheet may be adjusted.

The stretched polyolefin-based resin sheet is as follows:
Crosslinking treatment may be performed to increase heat resistance or to increase heat resistance and creep resistance of the 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 to be 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 rays 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 polyolefin-based resin sheet on the polyolefin-based resin foam sheet is not particularly limited, and examples thereof include adhesion with an adhesive and heat fusion by heating. Used for

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

(1) At least one surface of a foamed polyolefin-based resin sheet is laminated with a face material composed of a stretched polyolefin-based resin sheet, and then heated to form a composite foam.

(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 made of a stretched polyolefin resin sheet is laminated to form a composite foam.

(3) The face material composed of the stretched polyolefin-based resin sheet is laminated on the polyolefin-based resin foamable sheet during heating and foaming.

The method (1) can be carried out at a temperature at which the polyolefin-based resin foamable sheet is heated and foamed, if the stretched polyolefin-based resin sheet does not undergo thermal deformation, but the foaming temperature of the polyolefin-based resin foamable sheet is usually 18
Since the temperature is about 0 to 250 ° C., the method (2) or (3) is preferably used.

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

The laminating direction of the stretched polyolefin resin sheet is not particularly limited, but the mechanical properties in the stretched direction are particularly improved. Therefore, the sheet may be stretched in one direction or two directions (orthogonal or orthogonal) depending on the intended use. It is preferable to stack them 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 uniquely determined, but is usually 0.1 to 5 k.
A pressure in the range of g / 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, the shape of the laminate may be distorted due to shrinkage or the like during molding. And also has a bad influence on the linear expansion coefficient.

The polyolefin resin composite foam according to the present invention is lightweight, has high compressive strength and bending rigidity, and also has high shock absorption and dimensional stability. For example, it is suitably used as a material for a door core material, a bumper core material and the like.

[0080]

According to the cell shape of the polyolefin resin composite foam of the present invention, a force is applied in the long axis direction of the spindle-shaped cells with respect to the compression force in the sheet thickness direction. In addition, when the load exceeds the compression yield point, the bubble buckles, thereby absorbing the impact energy.

Further, the inorganic long fiber reinforced thermoplastic resin sheet or the stretched polyolefin resin sheet has a large tensile modulus of elasticity and a low coefficient of linear expansion, so that the sheet is used as a face material to at least one side of the polyolefin resin foam sheet. By laminating, a composite foam having a large flexural modulus and a small linear expansion coefficient can be obtained.

Further, since the face material composed of any of the above sheets is mainly made of a thermoplastic resin, it can be subjected to secondary shaping by heat.

[0083]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described more specifically with reference to embodiments.

Example 1 (1) Preparation of Modified Polyolefin Resin A BT40 (plastic engineering laboratory) co-rotating twin screw extruder was used as a screw extruder for modification. It has a self-wiping double-start screw with an L / D of 35 and a D of 39 mm. The cylinder barrel is composed of first to sixth barrels from upstream to downstream of the extruder. The die is a three-hole strand die, and a vacuum vent is provided in the fourth barrel to collect volatile components.

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 (“EX6” manufactured by Nippon Polychem, MI;
1.8, density; 0.9 g / cm ³ ), and the supply amount was 10 kg / h. The modifying monomer is divinylbenzene, and its supply amount is 10
0.5 parts by weight with respect to 0 parts by weight. The organic peroxide is 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3, and the supply amount is 0.1 part by weight based on 100 parts by weight of the polyolefin resin. And

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 TEX-44 type (manufactured by Nippon Steel Corporation) co-rotating twin screw extruder,
It is equipped with a self-wiping double screw and its L
/ D is 45.5 and D is 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.

Cylinder barrel set temperature: 1st zone; 150 ° C 2nd zone; 170 ° C 3rd zone; 180 ° C 4th zone; 160 ° C Screw rotation speed: 40 rpm

The modified resin obtained as described above and a homo-type polypropylene (“FY” manufactured by Nippon Polychem)
4 ", MI: 5.0, density: 0.9 g / cm3) 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 (ADCA), and the supply amount is 1.0 kg / h.
And Thus, a foamable resin composition was obtained by kneading the modified resin and the foaming agent.

(3) Preparation of Polyolefin Resin Foamable Sheet The 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 Composite Sheet A long glass fiber reinforced polypropylene sheet (“Preglon LF15”, manufactured by Mitsui Chemicals, weighing 330 g / m ² ) was laminated on both sides of the polyolefin resin foamable sheet, and a press molding machine was used. 180 ° C., pressure 19.6 using
Press molding was performed at a pressure of MPa (200 kgf / cm ² ) to obtain an expandable composite sheet.

(5) Foaming Remove the edge from the obtained foamable composite sheet,
A 00 mm square sample was obtained. This sample is 23
The mixture was heated in an oven at 0 ° C. for about 5 minutes to foam the foamable composite sheet to obtain a composite foam having a thickness of 5 mm.

Example 2 (1) Preparation of Modified Polyolefin Resin A modified polyolefin resin was obtained in the same manner as in Example 1.

(2) Preparation of foamable resin composition A foamable resin composition was obtained in the same manner as in Example 1 except that the supply amount of ADCA was changed to 1.5 kg / h.

(3) Preparation of Polyolefin Resin Foamable Sheet A foamable resin sheet was obtained in the same manner as in Example 1 except that the thickness was changed to 0.35 mm.

(4) Preparation of Expandable Composite Sheet A nonwoven fabric made of polyethylene terephthalate (“Toyobo Co., Ltd.,“ Spanbond Equore 6301A ”, weighing 30 g / m ² ) was laminated on both sides of the obtained foamable resin sheet. 180 ° C., pressure 19.6 using a press molding machine
Press molding was performed at a pressure of MPa (200 kgf / cm ² ) to obtain an expandable composite sheet.

(5) Foaming The edge was removed from the foamable composite sheet and 300
mm square samples were obtained. 230 ° C
Was heated in an oven for about 5 minutes to foam the foamable composite sheet to obtain a 5 mm thick polyolefin-based resin foam sheet.

(6) Preparation of stretched polyolefin resin sheet 1) Preparation of extruded sheet High density polyethylene (trade name: HY540, manufactured by Mitsubishi Chemical Corporation, MI = 1.0, melting point 133 ° C., weight average molecular weight 30)
1 part by weight of benzophenone (photopolymerization initiator) is blended with 100 parts by weight of 100,000), and the mixture is melt-kneaded at a resin temperature of 200 ° C. with a 30 mm twin screw extruder and formed into a sheet by a T-die. Extruded, cooled with a cooling roll, thickness 1.0m
m, an unstretched sheet having a width of 100 mm was obtained.

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, and is taken through a heating furnace set to an ambient temperature of 85 ° C. 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 stretch 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 K 7113.

3) Lamination and heat fusion As shown in FIG. 2, a low-density polyethylene film (thickness 30 μm, UF230, manufactured by Mitsubishi Chemical Corporation) was placed on both sides of the polyolefin resin foam sheet obtained earlier. The stretched polyolefin-based resin sheet was disposed thereon, the low-density polyethylene film was further disposed thereon, and the stretched polyolefin-based resin sheet was further disposed thereon, thereby obtaining three types and nine layers of laminated products. In a hand press molding machine, a temperature of 125 ° C. and a pressure of 98 kPa (1 kgf / cm
Press molding was performed for 2 minutes in ² ), and then water-cooled with a water-cooled press (pressure 98 kPa) to obtain a composite foam having a thickness of 5 mm.

(Comparative Example 1) Steps from step (1) of Example 2
A polyolefin resin foam sheet was obtained in the same manner as (5).

(Comparative Example 2) The same glass fiber reinforced polypropylene sheet as in Example 1 was laminated on both sides of a polypropylene foam (“Softlon SP # 1005” manufactured by Sekisui Chemical Co., Ltd., expansion ratio: 10 cc / g, thickness: 5 mm). Using a press molding machine at a temperature of 180 ° C. and a pressure of 0.098 MPa
(1 kgf / cm ² ) to obtain a composite foam.

(Comparative Example 3) Two hard boards (manufactured by Nichiha Corporation, thickness: 2.5 mm) were laminated with an adhesive to obtain a laminated product having a thickness of 5 mm.

Evaluation Test of Composite Foam The composite foams obtained in the above Examples and Comparative Examples were evaluated for the following items. The results are summarized in Table 1.

Apparent density: The apparent density was measured according to JIS K6767.

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

Bubble shape (average aspect ratio): The composite 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 m
m or less, and 10 mm or more bubbles were excluded.

[0114] Linear expansion coefficient: After marking the sample with marked lines at intervals of about 150 mm, the sample was placed in a thermostat at 5 ° C for 1 hour.
After leaving for a time, the distance between the marked lines was measured. Next, the sample was allowed to stand in a constant temperature bath at 80 ° C. for 1 hour, and then the distance between marked lines was measured in the same manner. Repeat this operation three times,
The average of the distances between the marked lines at 5 ° C. and 80 ° C. in the second round was determined, and the coefficient of linear expansion was calculated by the following equation.

[0115]

(Equation 1)

Flexural modulus Based on JIS K 7203, test speed 10 mm / m
The measurement was performed in, and the flexural modulus was calculated. Directional samples were evaluated in the length and width directions.

Izod impact value An Izod impact test based on JIS K 7110 was performed. No notch. Weighing 2.75 J, hammer hitting speed 3.5 / sec, hammer cutting edge radius 0.8 mm.

[0118]

[Table 1]

[0119]

According to the present invention, lightweight and strong rigidity is achieved.
A composite foam made of a polyolefin-based resin as a material, a vehicle member and a shock absorbing member made of the foam can be provided.

[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.

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Claims (5)

[Claims] 1. An aspect ratio Dz / Dx of an inherent bubble.
The average value of y is 1.1 to 4.0 and the expansion ratio is 3
A polyolefin-based resin composite foam, characterized in that a polyolefin-based resin foam sheet having an inorganic long fiber reinforced thermoplastic resin sheet is laminated on at least one surface of a polyolefin-based resin foam sheet having a size of up to 30 times. 2. A vehicle member comprising the polyolefin-based resin composite foam according to claim 1. 3. An impact absorbing member comprising the polyolefin resin composite foam according to claim 1. 4. An aspect ratio Dz / Dx of an inherent bubble.
The average value of y is 1.1 to 4.0 and the expansion ratio is 3
Polyolefin resin foam sheet having a linear expansion coefficient of 5.0 × 10 ⁻⁵ / ° C. or less laminated on at least one surface of a polyolefin resin foam sheet having a thickness of up to 30 times. A vehicle member made of a resin-based composite foam. 5. An aspect ratio Dz / Dx of an inherent bubble.
The average value of y is 1.1 to 4.0 and the expansion ratio is 3
Polyolefin resin foam sheet having a linear expansion coefficient of 5.0 × 10 ⁻⁵ / ° C. or less laminated on at least one surface of a polyolefin resin foam sheet having a thickness of up to 30 times. Shock absorbing member made of resin-based composite foam.