JPH11320778A - Polyolefin sheet laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyolefin sheet laminate composed only of a synthetic resin, easy to recycle, and excellent in strength and thermal dimensional stability. SOLUTION: A plurality of first stretched polyolefin sheets are laminated and integrated, and a plurality of first stretched polyolefin sheets stacked in the same stretching direction are different in stretching direction from the first stretched polyolefin sheet. So first
And a second stretched polyolefin sheet laminated on the stretched polyolefin sheet of (1).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin sheet laminate which can be suitably used, for example, as a member for automobiles, and more specifically, to a metal, metal-resin composite or resin-glass fiber composite. The present invention relates to a polyolefin sheet laminate excellent in strength and thermal dimensional stability that can be used.

[0002]

2. Description of the Related Art In order to reduce the weight of automobiles, various attempts have conventionally been made to replace members made of metal with members made of synthetic resin. For example, weather strips for airtight around the window glass, roof moldings attached to the ceiling and side surfaces of the vehicle interior, side moldings, garnishes or side sills, seat rails and seat frames that are members around the seats, etc.
Various members, such as a tonneau cover, which is a storage material for a luggage cover, and a bumper beam or a side impact beam that requires impact absorption, are being studied to be made of resin.

However, these members are required to have high mounting accuracy, excellent thermal dimensional stability, and excellent rigidity and impact resistance. Therefore, conventionally, the above-mentioned member has been constituted by a metal or a material obtained by coating a metal with a synthetic resin.

In recent years, in order to reduce the weight, a composite material obtained by combining glass fiber as a reinforcing material with synthetic resin in order to enhance rigidity and thermal dimensional stability has been used instead of metal in place of metal. . As such a composite material, a stampable sheet obtained by compounding a synthetic resin and glass fiber is known (for example, Japanese Patent Publication No. 54-36193).
JP-A-9-52322 and the like.

[0005]

However, in recent years,
In order to not only reduce the weight but also cause environmental pollution,
There is also a demand for automotive components to have recyclability. Therefore, there is a strong demand for a vehicle member made of a synthetic resin alone so as to facilitate disposal after disposal.

An object of the present invention is to meet the above-mentioned demands, and to provide a member which is composed only of a synthetic resin, is easy to recycle, and has excellent strength and thermal dimensional stability. .

[0007]

According to the first aspect of the present invention, there is provided a polyolefin sheet laminate obtained by laminating and integrating a plurality of polyolefin stretched sheets, wherein the plurality of polyolefin stretched sheets are laminated in the same stretching direction. And a first polyolefin stretched sheet, and at least one second polyolefin stretched sheet laminated so as to have a different stretching direction from the first polyolefin stretched sheet.

[0008] In the second aspect of the invention, the stretch ratio of the first and second stretched polyolefin sheets is in the range of 20 to 40 times. According to the third aspect of the present invention,
The coefficient of linear expansion of the second stretched polyolefin sheet is -2 ×
The range is 10 ⁻⁵ to + 2 × 10 ⁻⁵ .

The invention described in claim 4 is the first invention.
An automobile member constituted by using the polyolefin laminate according to any one of the above-described inventions. Hereinafter, details of the present invention will be described.

[0010] The polyolefin sheet laminate according to the present invention is constituted by laminating a plurality of stretched polyolefin sheets. The polyolefin constituting the polyolefin sheet is not particularly limited, and examples thereof include polyethylene, polypropylene, and homopolymers or copolymer components such as 1-butene and 1-pentene of 10% by weight or less. Or a copolymer obtained by copolymerizing these with a vinyl monomer, for example, vinyl acetate, vinyl alcohol, vinyl chloride, or acrylic acid, preferably at 10% by weight or less. In addition, the polyolefin,
It may be a mixed resin obtained by combining a plurality of the above-mentioned polyolefins.

Among them, high-density polyethylene or polypropylene is preferably used because of its high crystallinity and high rigidity after stretching. The weight average molecular weight of the polyolefin is preferably in the range of 100,000 to 500,000 because of excellent stretchability.

The melt index (MI) of the polyolefin is preferably in the range of 0.1 to 20, more preferably 1 to 10. When the MI is smaller than 0.1, a load is imposed on a molding machine such as an extruder, and when the MI is larger than 20, the stretchability may not be sufficient.

In producing the polyolefin sheet laminate according to the present invention, the above-mentioned polyolefin is supplied to an extruder, extruded from a T-die into a sheet, and cooled to obtain a raw sheet of polyolefin. In this case, the molding method and the cooling method are not particularly limited. The thickness of the raw sheet is not particularly limited, but is preferably in the range of 0.5 to 5 mm. 0.
If it is less than 5 mm or more than 5 mm, stretching performed later may be difficult.

Since the raw sheet is relatively thick, it is preferable to perform a rolling process before stretching. With the rolling process, the clearance between a pair of rolling rolls rotating in opposite directions is made smaller than the thickness of the raw sheet, the raw sheet is inserted between the rolling rolls, and the thickness of the raw sheet is reduced. , A process performed by extending in the length direction.

If the temperature of the raw sheet in the rolling step is too low, the rolling force is relatively large, so that it may be difficult to perform uniform rolling. If the temperature of the raw sheet is too high, the sheet may be rolled. Melting may occur during the process. Therefore, the temperature of the raw sheet in the rolling step is desirably 70 to 125 ° C, more preferably 90 to 120 ° C in the case of polyethylene. In the case of a raw sheet made of polypropylene, preferably 12
The temperature is desirably 0 to 160 ° C, more preferably 130 to 150 ° C.

If the rolling ratio is too low, not only the effect of the rolling cannot be expected, but also the burden on the subsequent stretching step will be increased. Conversely, if the rolling ratio is too high, the rolling force will increase, making uniform rolling difficult,
The thickness of the sheet after rolling becomes too thin, and the sheet may be cut in a subsequent stretching step. Therefore, the rolling ratio is preferably 2 to 10 times.

The rolling ratio in the present specification is defined by the following equation.

[0018]

(Equation 1)

After the raw sheet made of polyolefin is rolled as described above, it is stretched. In this case, a normal uniaxial stretching method is used as the stretching method. The uniaxial stretching method is a stretching method in which the sheet can be strongly oriented only in the uniaxial direction by pulling the sheet while being heated between two pairs of pinch rolls having different speeds. In this case, the rotation speed ratio of the roll becomes the stretching ratio. In the present invention, the speed ratio between the feeding roll and the take-off roll, that is, the stretching ratio is preferably 2 to 10 times.

In the present invention, the product of the above-mentioned rolling ratio and stretching ratio is defined as the total stretching ratio. The total stretching ratio is desirably 20 times or more, more preferably 25 times or more. If the total stretching ratio is less than 20 times, the rigidity of the obtained stretched polyolefin sheet may not be sufficiently increased, and the thermal dimensional stability may not be sufficiently enhanced. Also, if the total stretching ratio exceeds 40 times, the film may be locally stretched excessively, and the width of the sheet may not be stable,
Not preferred. More preferably, the total stretching ratio is desirably 35 times or less.

The thermal dimensional stability is usually evaluated by a coefficient of linear expansion. Automotive members require thermal dimensional stability comparable to that of metal. The coefficient of linear expansion of aluminum is 2.3 × 10
⁻⁵ (0 ° C. to 80 ° C.). Therefore, the linear expansion coefficient of the polyolefin sheet laminate according to the present invention is 2 × 10 ^{− in} the temperature range of 0 ° C. to 80 ° C. in consideration of the use of the above aluminum in place of the aluminum. ⁵ or less, and preferably -2 × 10 ^-5 or more.

The temperature of the polyolefin sheet during stretching is preferably in the range of 70 to 120 ° C. for polyethylene, and 100 to 160 ° C. for polypropylene.
The temperature is preferably set to Outside this temperature range, stretching of the sheet may easily occur during stretching.

As described above, a stretched polyolefin sheet is obtained. The thickness of the stretched polyolefin sheet is not particularly limited, but may be from 50 to 50.
Desirably, it is 500 μm. If it is less than 50 μm,
It is easily broken and may cause cracks in the laminating step. If it exceeds 500 μm, laminating later may be difficult.

The stretched polyolefin sheet may be subjected to a crosslinking treatment after the stretching treatment. By crosslinking treatment,
Heat resistance and creep resistance of the sheet can be improved. The crosslinking method is not particularly limited, and examples thereof include a chemical crosslinking method using silane, a crosslinking method using ultraviolet irradiation, and a crosslinking method using electron beam irradiation.

A gel fraction is used as an index of the crosslinking treatment. In this case, the crosslinked sheet is usually immersed in hot xylene at 120 ° C. for 24 hours, and the gel fraction is evaluated in terms of the weight percentage of the insoluble gel relative to the sheet before immersion. The gel fraction is preferably at least 25%, more preferably at least 50%. Gel fraction 2
If it is less than 0%, the heat resistance and the creep resistance may not be sufficiently increased by crosslinking.

The polyolefin sheet laminate according to the present invention is obtained by laminating a plurality of stretched polyolefin sheets obtained as described above. In this case, the number of stacked layers is not particularly limited, and is determined by the thickness required for the target member. Usually 5-10
Stretched polyolefin sheets are laminated in a range of 0 sheets.
When less than 5 polyolefin stretched sheets are used, the required rigidity may not be sufficiently exhibited,
Laminate more than 100 polyolefin stretched sheets,
In the case of joining, it is difficult to heat uniformly, and it may be difficult to surely laminate the polyolefin stretched sheets uniformly.

Since the polyolefin stretched sheet is uniaxially stretched as described above, it exhibits high thermal dimensional stability and rigidity in the stretching direction. However, the physical properties are considerably low in directions other than the stretching direction.

For example, when the automobile member to be applied has a long shape, a plurality of stretched polyolefin sheets are laminated so that the stretching direction coincides with the length direction. The thermal dimensional stability and rigidity can be significantly increased. However, automobile members are often required to have strength not only in the longitudinal direction but also in the lateral direction. In addition, it is necessary to withstand the process of opening a bolt hole.

Therefore, in the present invention, in order to increase the strength in directions other than the stretching direction, in addition to the plurality of first polyolefin stretched sheets laminated in the same stretching direction,
At least one second stretched polyolefin sheet is laminated such that the stretching directions are different.

That is, when laminating a plurality of polyolefin stretched sheets stretched in a certain direction, at least one second polyolefin having a different stretching direction from the plurality of first polyolefin stretched sheets having the same stretching direction. By laminating the stretched sheet and the stretching direction of the first polyolefin stretched sheet, the mechanical strength and the thermal dimensional stability in the stretching direction of the second polyolefin stretched sheet and in the direction between the two stretching directions are increased. Has been enhanced.

In particular, in order to enhance the shock absorbing property of an automobile member, in the case of a long member, not only the length direction but also a direction perpendicular to the length direction and an angle of 45 ° with the length direction. It is desirable to increase the physical properties in the crossing direction. For example, when applied to a long member such as a bumper beam, for example, a plurality of first polyolefin stretched sheets are laminated so that the stretching direction is aligned in the longitudinal direction, and the laminate is orthogonal to the longitudinal direction. It is preferable to stack the respective second polyolefin stretched sheets in which the direction in which the second direction crosses at a 45 ° angle is the stretching direction. As described above, as long as the stretching direction is different from that of the first polyolefin stretched sheet, each of the second polyolefin stretched sheets in two or more kinds of stretching directions may be used. When applied to the above bumper beam, etc., the first stretched polyolefin sheet and the second
As for the ratio (weight ratio) of the stretched polyolefin sheet, it is preferable to laminate the second stretched polyolefin sheet at a ratio of about 2 to 10 parts by weight with respect to 10 parts by weight of the first stretched polyolefin sheet. It is possible to enhance physical properties not only in the length direction but also in a direction perpendicular to the length direction and a direction intersecting the length direction at an angle of 45 °.

As described above, the method for laminating and joining and integrating the first and second stretched polyolefin sheets is not particularly limited. For example, in the state where a resin film having a melting point lower than the melting point of the polyolefin constituting the stretched polyolefin sheet is interposed between the stretched polyolefin sheets, the temperature between the melting point of the polyolefin and the melting point of the resin constituting the resin film is reduced. , And a method of heating and compression at a temperature of, followed by cooling to integrate them.

Alternatively, a solvent having a high affinity for polyolefin such as styrene, toluene, or xylene is applied to the surface of the stretched polyolefin sheet, and then a plurality of sheets of the polyolefin stretched sheet are heated at a temperature equal to or lower than the melting point of the polyolefin constituting the stretched polyolefin sheet. The polyolefin stretched sheets are laminated and heated and compressed to locally melt the surface portion of the polyolefin stretched sheet, and then cooled to be integrated.

The shape of the polyolefin sheet laminate obtained by joining and integrating as described above is not particularly limited, and is selected according to the shape of the target member.
For example, when a plate-like member is required, the above-mentioned laminating / joining step may be performed by a flat press molding method. Further, when a member having a pipe shape, a U-shape, or a complicated irregular shape is required, a method of extracting the polyolefin sheet laminate from the mold while pressing the inside of the mold having a desired cross-sectional shape is used. Adopt it. Further, press molding may be performed by a press having an irregular shape.

The polyolefin sheet laminate according to the present invention is suitably used as an automobile member. Examples of such automobile members include interior materials, exterior materials, internal members, and members that require shock absorption. As the interior material, for example, seat rail, seat frame, seat shell, garnish, side sill, tonneau cover, A
/ T shift pace, side mat guard, roof liner, door liner, trunk room lining, sunroof housing, sunshade, instrument panel, console box.

Examples of the exterior material include a side molding, a roof molding, a step, a rear spoiler, a rear fender, a head cover, a center pillar, an engine under cover, and a transmission cover.

As the internal member, for example, a weather strip, a battery tray, a fuel tank cover, an engine soundproof wall, a brake cover, an air cleaner case, a radiator support and the like can be mentioned.

Examples of the member required to absorb the impact include a side impact beam, a bumper beam, a bumper fascia, a bumper corner, and a bumper skirt.

However, the polyolefin sheet laminate according to the present invention can be used not only for automobile members but also for other uses. That is, because the mechanical strength is high in multiple directions and excellent in thermal dimensional stability,
It can also be suitably used for various long materials, members used on coasts and the like that make use of the chemical resistance of polyolefin, and road materials such as guardrails and guard balls that make use of high shock absorption.

(Function) In the polyolefin sheet laminate according to the first aspect of the present invention, a plurality of stretched polyolefin sheets having increased rigidity and thermal dimensional stability in the stretching direction are laminated. In addition, not only the first polyolefin stretched sheet laminated in the same stretching direction but also at least one second polyolefin stretched sheet is laminated so that the stretching direction is different from that of the first polyolefin stretched sheet. Therefore, the thermal dimensional stability and the mechanical strength are improved not only in the stretching direction of the first stretched polyolefin sheet, but also in the stretching direction of the second stretched polyolefin sheet. Therefore, for example, when used for a long member, when the stretching direction of the first polyolefin stretched sheet is matched with the length direction, not only in the length direction,
Mechanical strength and thermal dimensional stability in other directions that intersect the length direction are also increased.

According to the second aspect of the present invention, the stretching ratio of the first and second stretched sheets is set in the range of 20 to 40 times, and since the stretch ratio is high, the rigidity and thermal dimensional stability are reduced. More effectively enhanced.

According to the third aspect of the present invention, the first and second stretched polyolefin sheets have a coefficient of linear expansion of -2 × 10 ^-5 or ^less .
Since it is in the range of + 2 × 10 ⁻⁵ , it exhibits the same thermal dimensional stability as a metal such as aluminum. Moreover, the thermal dimensional stability is exhibited not only in the stretching direction of the first stretched polyolefin sheet, but also in the stretching direction of the second stretched polyolefin sheet and in a direction between these stretching directions.

According to the fourth aspect of the present invention, the first to third aspects are provided.
Since the automotive member is composed of the polyolefin sheet according to the invention described in the above, the mechanical strength and dimensional stability are increased not only in one direction, but also in the other direction, and from only synthetic resin. Can be provided.

[0044]

The present invention will be clarified by the following non-limiting examples.

Example 1 Weight Average Molecular Weight 3.3 × 10
⁵ , melt index (MI) = 1.0, melting point 135
℃ high-density polyethylene (manufactured by Nippon Polychem Co., grade: HY540) using a biaxial kneading extruder (manufactured by Ikegai Iron and Steel Co., Ltd., product number: PCM30), resin temperature about 100 ℃
, And formed into a sheet having a width of 70 mm and a thickness of 2.5 mm by a calendering machine controlled at a roll temperature of 90 ° C., and wound up. Thereafter, the rolled sheet was unwound and rolled nine times using a hot roll (made by Kodaira Seisakusho, roll diameter 6 inches) heated to 120 ° C. to obtain a rolled sheet.

Next, using a hot air heating type two-stage stretching machine, the stretching ratio of the first stage is set to 1.8 times and the stretching ratio of the second stage is set to 1.6 times so that the total stretching ratio is 2.9 times. The above-mentioned rolled sheet was stretched. The stretching temperature in the first and second stages of stretching was 100 ° C.

The total stretching ratio obtained by combining the above-mentioned rolling step and stretching step was about 26 times, the dimensions of the sheet after stretching were 35 mm in width × 200 μm in thickness, and the surface of the sheet was smooth.

[0048] A plurality of 18 stretched sheets obtained as described above were prepared. Thereafter, 12 of the stretched sheets were laminated as the first stretched polyolefin sheet in the same stretching direction. However, when laminating the first stretched polyolefin sheets, the six second stretched polyolefin sheets may be stretched in such a manner that the stretching direction is perpendicular to the first stretched polyolefin sheet.
Were laminated with the stretched polyolefin sheet interposed therebetween. The six second stretched polyolefin sheets were arranged between the first stretched polyolefin sheets so as to be uniformly distributed in the thickness direction between the first stretched polyolefin sheets 12. In order to obtain the above-mentioned laminate composed of the first and second polyolefin stretched sheets, a linear low-density polyethylene film (thickness: 30 μm) is interposed between the sheets.
m) was interposed.

The laminated body obtained as described above was heated and compressed for 2 minutes under the condition of a pressure of 0.5 MPa using a press set at a press heating temperature of 125 ° C., and integrated.
It was cooled to room temperature by a cooling press. In this way,
A polyolefin sheet laminate of Example 1 was obtained.

Example 2 2 parts by weight of benzophenone (manufactured by Nippon Kayaku Co., Ltd.) were blended with 100 parts by weight of high-density polyethylene (manufactured by Nippon Polychem Co., Ltd., grade: HY540). A stretched sheet was prepared in the same manner as described above.

Further, an output of 120 W was applied to the stretched sheet.
/ Cm high pressure mercury lamp and distance from stretched sheet is 50
mm, and irradiated with ultraviolet rays for 1 second to crosslink the stretched sheet. Regarding the degree of cross-linking, the stretched sheet sample after cross-linking was dissolved in xylene at 120 ° C. for 24 hours, and the weight percentage (gel fraction) of the undissolved portion relative to the sample before the dissolution treatment was performed.
Was measured and evaluated. The degree of crosslinking was about 60%.

A polyolefin sheet laminate was obtained in the same manner as in Example 1 except that the crosslinked stretched sheet obtained as described above was used.

Example 3 A polyolefin sheet laminate was obtained in the same manner as in Example 1 except that the lamination direction of the first and second stretched polyolefin sheets was changed as shown in Table 1 below. Was.

Example 4 100 parts by weight of a homopolypropylene resin (manufactured by Mitsubishi Chemical Corporation, grade: MA3) was mixed in a coaxial twin-screw extruder (manufactured by Ikegai Iron and Steel Company, product number: PCM30) at a resin temperature of about 200 ° C. Using a calendering machine in which the roll temperature is controlled at 90 ° C. and a width of 70 mm
× The sheet was formed into a sheet having a thickness of 2.5 mm and wound up. Thereafter, a hot roll heated to 150 ° C. (manufactured by Kodaira Seisakusho,
Rolled 9 times using a roll diameter of 6 inches) to obtain a rolled sheet.

Next, at a stretching temperature of 160 ° C., the stretching ratio of the first stage was set to 1.8 times and the stretching ratio of the second stage was set to 1.6 times using a hot air heating type two-stage stretching machine. A 2.9-fold stretching operation was performed to obtain a stretched sheet. The total stretching ratio of the above-mentioned rolling process and stretching process is about 26 times, and the stretched polyolefin stretched sheet has a width of 35 mm.
X The thickness was 200 µm, and the surface was smooth. In addition,
The stretching temperature in the first and second stages of stretching is 100 ° C.
And

The stretched polyolefin sheet obtained as described above is laminated as shown in Table 1 below, provided that
Unlike in Example 1, a film was not used between the polyolefin stretched sheets, and xylene was used.
The laminate was adhered to the surface of each stretched polyolefin sheet so as to be 2 parts by weight with respect to the parts by weight.

The obtained laminate was heated at a press heating temperature of 15
Using a press set at 0 ° C., the mixture was heated and compressed at a pressure of 0.5 MPa for 3 minutes, integrated, and cooled to room temperature by a cooling press. Thus, a polyolefin sheet laminate of Example 4 was obtained.

(Example 5) A polyolefin sheet laminate was obtained in the same manner as in Example 4, except that the lamination mode of the first and second stretched polyolefin sheets was changed as shown in Table 1 below. Was.

(Comparative Example 1) A polyolefin sheet laminate was obtained in the same manner as in Example 1, except that all the stretched polyolefin sheets were laminated in the same stretching direction.

(Comparative Example 2) A polyolefin sheet laminate was obtained in the same manner as in Comparative Example 1, except that a polyolefin stretched sheet was obtained so that the total stretch ratio was 15 times.

Comparative Example 3 A polyolefin sheet laminate was obtained in the same manner as in Example 4 except that 26 polyolefin stretched sheets were laminated so that the laminating direction was aligned with the stretching direction.

(Comparative Example 4) Except that the total stretching ratio of the laminated polyolefin stretched sheets was set to 15 times,
A polyolefin sheet laminate was obtained in the same manner as in Comparative Example 3.

(Comparative Example 5) As a conventional product, a commercially available glass fiber reinforced polyolefin composite (a stampable sheet)
Was prepared. This stampable sheet has a glass fiber content of 50% by weight, and is a unidirectionally reinforced type, manufactured by Ube Nitto Kasei Co., Ltd., trade name: AZDEL.

[0064]

[Table 1]

(Evaluation of Examples and Comparative Examples) With respect to the polyolefin sheet laminates obtained in Examples and Comparative Examples, the measurement of the bending elastic modulus and the bending strength, the measurement of the linear expansion coefficient, and the measurement of the shock absorption value were performed. . The results are shown in Table 2 below.

Measurement of bending elastic modulus and bending strength: JIS K
According to 7113, the bending elastic modulus and the bending strength of the polyolefin laminate in the main laminating direction, that is, the direction along the stretching direction of the first stretched polyolefin sheet, were measured.

Measurement of linear expansion coefficient: Using a thermal stress / strain measuring apparatus (TMA), the stretched polyolefin sheet prepared in each of Examples and Comparative Examples was heated four times at a rate of 2 ° C./min from 0 to 90 ° C. The measurement was repeated, and the average value of the coefficient of linear expansion from 0 to 90 ° C. was determined.

Measurement of shock absorption value: using a high-speed impact tester manufactured by Shimadzu Corporation, product number: HTM-1, at a test speed of 3 m / m
The impact absorption value was measured at 23 ° C. according to JIS K7084 under the conditions of minutes.

[0069]

[Table 2]

In Table 2, in Comparative Examples 2 and 4,
The value of the coefficient of linear expansion is not shown. Dust was in Comparative Examples 2 and 4.
In this case, since the variation in the linear expansion coefficient of the sheet is very large, measurement is impossible.

As is apparent from Table 2, in Comparative Examples 1 to 3 corresponding to Comparative Example 1 in which the laminating directions were aligned to form a polyolefin sheet laminate, in the stretching direction of the first polyolefin stretched sheet. The flexural modulus and flexural strength do not change much, but the shock absorption value is significantly increased. Similarly, in Comparative Examples 3 and 4, corresponding to Examples 4 and 5, the bending elastic modulus and the bending strength in the stretching direction of the first polyolefin stretched sheet are not so different. In Table 2, the shock absorption value is significantly increased.

This is because in Examples 1 to 3 and Examples 4 and 5, the direction orthogonal to the first stretched polyolefin sheet was as follows:
Alternatively, since the second polyolefin stretched sheet is further laminated in a direction intersecting at an angle of 45 °, the strength of the first polyolefin stretched sheet other than in the stretching direction is increased, thereby reducing the impact absorption value. It is considered enhanced.

Comparative Examples 2 and 4 in which the draw ratio was reduced
In comparison, in Examples 1 to 3 and Examples 4 and 5, respectively, the first polyolefin stretched sheet has a sufficiently high flexural modulus and flexural strength along the stretching direction and a higher shock absorption value. Recognize.

Further, in Examples 1 to 5, the shock absorption value is greatly increased as compared with Comparative Example 5 which is a conventional product.

[0075]

According to the polyolefin sheet laminate according to the first aspect of the present invention, the plurality of first stretched polyolefin sheets laminated in the same stretching direction and the first stretched polyolefin sheet have the same stretching direction. Since at least one stretched polyolefin sheet is laminated and integrated differently, not only the stretching direction of the first stretched polyolefin sheet, but also the stretching direction of the second stretched polyolefin sheet and the stretching direction of both. The physical properties are also improved in the direction of. Therefore, a polyolefin sheet laminate having high strength and excellent thermal dimensional stability can be obtained not only in the stretching direction of the first stretched polyolefin sheet, but also in these directions.

Therefore, when used for a long automobile member such as a bumper beam, for example, the mechanical strength and the thermal dimensional stability not only in the length direction of the long member but also in the direction intersecting the length direction. Is enhanced. Accordingly, it is possible to provide a structural material that is suitable as a member for automobiles and that is made of only synthetic resin.

The polyolefin sheet laminate according to the present invention is excellent in recyclability because it uses only a synthetic resin as described above, that is, does not require other materials such as glass fibers.

Accordingly, the polyolefin sheet laminate according to the present invention can be suitably used for members requiring high mechanical strength and thermal dimensional stability, such as various automotive members, and the recycling thereof can be easily performed. obtain.

Claims (4)

[Claims] 1. A polyolefin sheet laminate obtained by laminating and integrating a plurality of stretched polyolefin sheets, comprising: a plurality of first stretched polyolefin sheets laminated in the same stretching direction; A polyolefin sheet laminate comprising: at least one second stretched polyolefin sheet laminated so that the stretching direction is different from the stretched polyolefin sheet. 2. The polyolefin sheet laminate according to claim 1, wherein the stretch ratio of the first and second stretched polyolefin sheets is in the range of 20 to 40 times. 3. The method according to claim 1, wherein a linear expansion coefficient of the first and second stretched polyolefin sheets is in a range of −2 × 10 ⁻⁵ to + 2 × 10 ⁻⁵ . Polyolefin sheet laminate. 4. The polyolefin sheet laminate according to claim 1, which is a member for an automobile.