JP2003306862A - Polyolefin-based film composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyolefin-based film composite where a filament nonwoven fabric and a microporous polyethylene film are favorably joined each other. <P>SOLUTION: The polyolefin-based film composite is a laminate composed of the filament nonwoven fabric and the microporous polyethylene film. The filament nonwoven fabric comprises sheath/core-type conjugate filaments each of which is composed of a polyethylene sheath and a polyester core, wherein the polyethylene is 0.890-0.920 g/cm<SP>3</SP>in density and 75-115°C in melting point, being prepared using a metallocene-based polymerization catalyst, its Q-value (weight-average molecular weight/number-average molecular weigh) being preferably 1.5-3.5, and the polyester is ≥45°C higher in melting point than the polyethylene. The filament nonwoven fabric is laminated with the microporous polyethylene film by melting or softening the polyethylene sheath of the conjugate filaments to form the polyolefin-based film composite. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composite of a long fiber non-woven fabric and a microporous polyethylene film which can be used in a wide range of fields such as medical materials, hygiene materials, general industrial materials, agricultural materials and daily life materials. .

[0002]

2. Description of the Related Art Conventionally, a nonwoven fabric obtained by a spunbond method, that is, a thermoplastic resin is melted, and a spun yarn group is drawn by a high-speed air stream, drawn, opened, and collected on a net conveyor. The long-fiber non-woven fabric in which fibers are integrated by melting and adhering fibers to each other by forming a nonwoven web by stacking,
Higher productivity than dry and wet type nonwoven fabrics.
It is well known for its excellent mechanical properties such as tensile strength.

In such spunbonded non-woven fabrics, however, long-fiber non-woven fabrics containing a single component of a thermoplastic resin such as polyamide or aromatic polyester as a constituent polymer have excellent non-woven fabric strength, but flexibility and heat sealing. It cannot be said that it can be suitably used for applications requiring properties and the like.

On the other hand, spunbonded nonwoven fabrics made of olefin polymers such as polyethylene and polypropylene are excellent in flexibility and heat sealability, but fibers made of olefin polymers are polyamide or polyester polymers. There is a problem in that the fiber strength is inferior to that of the fiber made of, and therefore the strength of the non-woven fabric is weak and the strength of the heat-sealed portion is weak accordingly.

A core-sheath type long-fiber non-woven fabric having polyethylene in the sheath and polyester or polypropylene in the core is inferior in strength to a non-woven fabric made of polyamide or aromatic polyester alone, but is made of a polyolefin polymer alone. It is well known that it is stronger than non-woven fabric and has good heat sealability. In this core-sheath type long-fiber nonwoven fabric, the polyethylene of the sheath has a density of 0.9.
High density polyethylene above 2 g / m ³ is most commonly used. Such high-density polyethylene has a melting point of about 130 ° C.
The heat treatment temperature is set to 0 ° C. or higher. In recent years, composites of non-woven fabrics and other materials have been often performed, and a wide variety of materials have been used for bonding. As another composite material, for example, in the case of thermally adhering to a material having a large heat shrinkage such as a microporous film containing a polyethylene polymer as a main component, a material having a temperature of 130 ° C. or higher in order to melt the high-density polyethylene in the sheath portion. When the heat treatment temperature is applied, there is a problem that the polyethylene microporous film is significantly heat-shrinked or the adhesive surface is distorted, and the resulting composite material has a poor appearance due to film shrinkage, etc. It cannot be said that good adhesion could be achieved in the state of having the property. Also,
When the heat treatment temperature is lowered, there is a problem that the adhesive force between the two becomes weak.

As a means for solving this problem, it is conceivable to use polyethylene obtained by a Ziegler-Natta catalyst having a melting point of about 100 ° C. instead of the high-density polyethylene, whereby the heat treatment temperature is higher than that of the above-mentioned high-density polyethylene. It can be expected to be set low. However, when polyethylene with a Ziegler-Natta catalyst is placed in the sheath part and a thermoplastic resin having a high melting point such as polyester is placed in the core part to perform core-sheath type composite spinning, when the spinning temperature is set, It is necessary to set the spinning temperature to a temperature at which the polyester having a high melting point melts. Then, there is a large difference between the spinning temperature and the melting point of polyethylene by the Ziegler-Natta catalyst, and the polyethylene by the Ziegler-Natta catalyst contains many low molecular weight substances and copolymers. There has been a problem that the low molecular weight substance undergoes thermal decomposition, and the spinnability and spreadability are deteriorated due to smoke generation directly under the spinneret and stickiness of the spun yarn surface.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and has heat sealability, and particularly has excellent heat-adhesion performance in heat seal processing in a low temperature range and has mechanical strength. An excellent long-fiber non-woven fabric, and in manufacturing, using a long-fiber non-woven fabric excellent in spinnability and openability so that it can be suitably combined with a microporous polyethylene film, that is, a microporous polyethylene film It is an object of the present invention to prevent heat shrinkage that occurs and to allow good composite formation in a state of having microporosity.

[0008]

Means for Solving the Problems That is, the present invention provides a composite of a continuous fiber non-woven fabric comprising a core-sheath type composite continuous fiber and a microporous polyethylene film, wherein the core-sheath type composite continuous fiber has a sheath portion. However, the density is 0.890-0.920 g / cm
^{3. The} long-fiber non-woven fabric made of polyethylene having a melting point of 75 to 115 ° C., the core made of polyester having a melting point of 45 ° C. or more higher than the melting point of the polyethylene, and the polyethylene of the sheath being melted or softened. The present invention relates to a polyolefin-based film composite, wherein the microporous polyethylene film and the microporous polyethylene film are composite.

The long-fiber nonwoven fabric of the present invention comprises a core-sheath type composite long fiber, and the sheath has a density of 0.890 to.
It is made of polyethylene (hereinafter, referred to as low density polyethylene) having a melting point of 75 to 115 ° C. and 0.920 g / cm ³ .

The density of the low-density polyethylene in the sheath is 0.9
When it exceeds 20 g / cm ³ , the melting point of the low-density polyethylene becomes high, and the long-fiber nonwoven fabric has poor thermal adhesiveness in a low temperature range, so that the object of the present invention cannot be achieved. On the other hand, the density of low density polyethylene is 0.890 g /
When it is less than m ³ , the surface of the long fiber becomes sticky, and the openability when obtaining the long fiber non-woven fabric by the spun bond method is deteriorated, so that the long fiber non-woven fabric has poor texture and texture. .

The low-density polyethylene of the sheath has a melting point peak of 75 to 115 ° C, preferably 90 to 1
It is of 10 ° C. If the melting point peak exceeds 115 ° C, the heat-sealing property at low temperature is inferior, which is not the object of the present invention. On the other hand, if the melting point peak is less than 75 ° C, the long-fiber nonwoven fabric is melted during production. The spun long fibers are difficult to cool, and the surface of the long fibers is sticky, resulting in poor openability, and the obtained long fiber nonwoven fabric has poor texture.

The low-density polyethylene constituting the sheath is preferably obtained by a metallocene-based polymerization catalyst, and its Q value (weight average molecular weight / number average molecular weight) is 1.5 to 3.5. It is preferable. The smaller the Q value, the more uniform the crystal size and the narrower the molecular weight distribution in the molecular structure of the low density polyethylene. When the Q value of low-density polyethylene exceeds 3.5, the number of relatively low-molecular-weight ones increases, so that the low-molecular-weight ones are thermally decomposed or produce smoke during melt spinning. It becomes inferior in sex. On the other hand, low-density polyethylene with a Q value of less than 1.5 makes it difficult to produce polyethylene itself,
Even if it can be manufactured, the manufacturing cost is extremely high.

As will be described later, the melting point difference between the low density polyethylene arranged in the sheath and the polyester arranged in the core is 45.
In order to set the temperature at or above 0 ° C, the polyester having a melting point of about 200 to 260 ° C is more preferably used, and the spinning temperature at the time of melt spinning is 250 ° C to It will be in the range of 295 ° C. At such temperatures, the low molecular weight polyethylene present in low density polyethylene undergoes thermal decomposition, smokes, and has poor spinnability. Therefore, in the present invention, it is preferable to set the Q value to a specific range, thereby reducing the amount of low-molecular-weight polyethylene as much as possible and reducing the thermal decomposition of polyethylene in the sheath during high-temperature spinning, The spinnability can be improved. In the molecular structure of low-density polyethylene, those having a relatively uniform crystal size and a narrow molecular weight distribution exhibit excellent spinnability during melt spinning.

The low-density polyethylene used in the present invention preferably has a melt flow rate of 10 to 60 g / 10 minutes. This melt flow rate is 60 g / 10
If it exceeds the minute, the melt viscosity is too low and the uniformity of the fibers is poor, and the spinning state tends to deteriorate. On the other hand, if the melt flow rate is less than 10 g / 10 minutes, the melt viscosity tends to be too high, and the high-speed yarn formability tends to be poor.

In the present invention, the above-mentioned low density polyethylene is used as the component constituting the sheath portion, but a small amount of high density polyethylene or polypropylene may be blended within a range not impairing the object of the present invention. The blending amount of the polymer other than the low density polyethylene is 3
It is preferably less than 0% by mass, more preferably,
It is less than 10% by mass. The blending amount of other polymer is 30
When the content is more than mass%, the heat-sealing property at low temperature becomes poor and the object of the present invention cannot be achieved.

The low-density polyethylene that constitutes the sheath includes
If desired, various additives such as matting agents, pigments, crystal nucleating agents and the like may be added within a range that does not impair the effects of the present invention.

The core portion of the core-sheath type composite continuous fiber is made of polyester having a melting point higher by 45 ° C. or more than the melting point of the low density polyethylene constituting the sheath portion.

When the difference between the melting point of the low-density polyethylene and the melting point of the polyester of the core is less than 45 ° C., the polyester of the core is heated by heat during heat sealing or heat treatment for compounding with other materials. Are damaged, and the mechanical strength of the obtained long-fiber nonwoven fabric or composite material is reduced. Further, when the difference between the melting point of the low density polyethylene used in the present invention and the melting point of the polyester is less than 45 ° C, the melting point is 16
A polyester having a melting point of less than 0 ° C. and having such a low melting point is inferior in productivity, operability, and cost, which is not preferable.

Polyethylene terephthalate, polybutylene terephthalate, and polytrimethylene terephthalate are preferably used as the polyester constituting the core. It is also possible to use a copolyester obtained by copolymerizing a small amount of the above-mentioned alkylene terephthalate as a main component with other components. As the other components, as acid components, carboxylic acids such as isophthalic acid and adipic acid, and diols. Examples of the component include glycol components such as tetramethylene glycol and neopentyl glycol. When a copolyester is used, the alkylene terephthalate unit content is preferably 80 mol% or more from the viewpoint of heat resistance and fiber strength of the polymer itself. This is because if the copolymerization component exceeds 20 mol%, the orientation of the fibers is poor and the melting point is lowered.

Particularly in the present invention, polyethylene terephthalate is preferably used, and as the copolyester, those obtained by copolymerizing ethylene terephthalate as a main component and isophthalic acid in a range of less than 20 mol% are preferably used. it can.

Considering the heat resistance of the polyester constituting the core, the melting point thereof is preferably 160 ° C. or higher, more preferably 200 ° C. or higher. Further, the upper limit of the melting point of the polyester is set to about 260 ° C. in consideration of the difference in the melting point between the polyester and the low density polyethylene of the sheath portion.

The intrinsic viscosity [η] of the polyester used in the present invention is preferably 0.5 or more, more preferably 0.6 or more, from the viewpoints of spinnability and mechanical strength of the resulting long fibers.

The composite ratio of the core portion and the sheath portion of the core-sheath type composite filament in the present invention may be appropriately determined according to the application.
When the ratio of the sheath portion is too small, the heat-sealing property tends to be poor, while when the ratio of the sheath portion is too large,
The fiber strength and the strength of the nonwoven fabric tend to be inferior. Generally, the composite ratio (mass ratio) of the core part and the sheath part is 20/80 to 8
It is preferably in the range of 0/20.

The long-fiber nonwoven fabric of the present invention is one in which the core-sheath type composite fibers are deposited and integrated. As a method for forming a non-woven fabric for integration, a general non-woven fabric means may be used. For example, by heat treatment such as hot embossing treatment or hot air treatment, the fibers are thermally bonded by melting or softening the sheath portion. Examples include heat-bonded nonwoven fabrics, and entangled nonwoven fabrics in which fibers are mechanically entangled by needle punching or the like. In the present invention, it is preferable that the long-fiber nonwoven fabric is partially heat-bonded by hot embossing.

Next, a preferred method for producing the long fiber nonwoven fabric of the present invention will be described.

The long-fiber nonwoven fabric of the present invention can be efficiently manufactured by the so-called spunbond method. That is, a polyester polymer chip is used as the core part, a low density polyethylene is used for the sheath part, or a polymer chip in which polypropylene or high density polyethylene is mixed with low density polyethylene by a dry blend method or the like is used as the core part. Melt spinning is performed using a spinneret having a sheath-type composite cross section. The spinning temperature at this time is 30 to 30% higher than the melting point of the core.
Set a high temperature of about 40 ° C. Therefore, when the above-mentioned preferred polyester is used, the spinning temperature is 2
It is in the range of 50 ° C to 295 ° C.

Then, the obtained spun yarn is pulled and thinned by a suction device so as to have a desired fineness, and is taken up. And after opening the yarn group discharged from the suction device,
A nonwoven web can be obtained by accumulating on a conveyor net, and the nonwoven web can be introduced into a hot embossing device and subjected to a heat press contacting treatment to obtain a long-fiber nonwoven fabric composed of core-sheath type composite long fibers.

The long-fiber non-woven fabric used in the present invention has the above-mentioned constitution and has a good heat-sealing property in a low temperature region, and therefore can be suitably used for applications requiring heat-sealing.

Further, this long-fiber nonwoven fabric can be laminated by melting or softening the low-density polyethylene of the sheath portion and using this as an adhesive component and adhering it to another material. In the present invention, , A microporous polyethylene film is used as another material.

Since the microporous polyethylene film has compatibility with the low-density polyethylene in the sheath portion of the core-sheath type composite long fibers, it can be preferably compounded and can be suitably used as a packaging material or a sanitary material.

Further, since the long-fiber nonwoven fabric used in the present invention has a low melting point of the low-density polyethylene in the sheath portion, it is sufficiently softened or melted even when the heat treatment temperature is set to about 100 ° C. to form a composite with the microporous polyethylene film. Can be converted. Then, the microporous polyethylene film can be satisfactorily bonded (composited) without damaging the microporosity of the microporous polyethylene film and without shrinking the microporous polyethylene film.

The long fiber non-woven fabric and the microporous polyethylene film can be combined by the following method. That is, heat treatment such as a hot roll or hot air melts or softens the low-density polyethylene that constitutes the sheath portion of the long-fiber nonwoven fabric, adheres the microporous polyethylene film, and if necessary, heat or pressure is applied to both. By bonding and integrating
Get the complex.

[0033]

EXAMPLES The present invention will now be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, each characteristic value in the examples was obtained as follows.

(1) Intrinsic viscosity [η] of polyester; 100 mixed solvent of phenol and ethane tetrachloride in equal mass ratio
A 0.5 g sample was dissolved in cc and measured.

(2) Melting point (° C.); using a differential scanning calorimeter DSC-7 type manufactured by Perkin Elmer Co., Ltd., heating rate 20 ° C.
It was measured in minutes.

(3) Melt flow rate of polyethylene (g / 10 minutes); measured by the method described in JIS K 6922 (temperature 190 ° C., load 21.18 N).

(4) Polypropylene melt flow rate (g / 10 minutes): Measured by the method described in JIS K 6921 (temperature 230 ° C., load 21.18 N).

(5) Fiber opening property of long fibers: A yarn group which is melt-spun from a spinneret having a core-sheath type composite cross section and is thinned by a suction device is discharged from the fiber opening device through a suction device. The state was observed and evaluated in the opened state. The evaluation was performed in the following four stages. ⊚: There is no bundled yarn, and the opened state is extremely good. ○: There are some bundled yarns, but the opened state is relatively good. Δ: There are many bundled yarns, and the opened state is poor. X: Most of the yarn groups are in close contact with each other and the fibers are not opened.

(6) Tensile strength of long fiber non-woven fabric (N / 5c
m width); Synthetic long fiber non-woven fabric test method (JIS L 190
Tensilon RT manufactured by Toyo Baldwin Co., Ltd. according to 6)
Using the M-500 type, a test piece having a width of 50 mm and a length of 200 mm was held at a gripping interval of 100 mm and a pulling speed of 100 mm /
It was measured under the condition of minutes, and the average value of 10 points of the sample was obtained to obtain the tensile strength. The tensile strength was determined in both the MD direction (machine direction) and the CD direction (direction orthogonal to the MD direction) of the long fiber nonwoven fabric.

(7) Heat sealing strength (N); 30 mm
(CD direction) x 150 mm (MD direction) Two sample pieces (long fiber nonwoven fabric) are superposed, and 50 mm from the longitudinal direction (MD direction) tip is thermocompression bonded with a heat seal tester (die temperature 100 ° C, Each temperature of 110 ℃ and 120 ℃ is set, surface pressure 98 N / cm ² , adhesive area 10 m
m (MD direction) × 30 mm (CD direction)). The peel strength of the heat-bonded portion is in accordance with the T peel measuring method of JIS L 1089, and Tensilon RTM-5 manufactured by Toyo Baldwin Co., Ltd.
Using a 00 type, a test piece with a width of 30 mm was held at a gripping interval of 10
mm, the tensile speed was 100 mm / min, and the average value of 5 points was calculated to obtain the heat sealing strength.

[Production Example 1 of long-fiber non-woven fabric] Polyester terephthalate having a melting point of 260 ° C. and an intrinsic viscosity of 0.70 was used as the polyester of the core part, and was polymerized using a metallocene-based polymerization catalyst as the polyethylene of the sheath part. Melt flow rate 20 g / 10 minutes, Q value 2.2, density 0.
A low-density polyethylene having a melting point of 102 ° C. and 904 g / cm ³ was used to produce a core-sheath long-fiber nonwoven fabric by the following spunbond method.

Using the above polyester and low-density polyethylene as raw materials and using a known melt spinning device, a spinning temperature of 28
At 0 ° C., melt spinning is performed from a spinneret having a core-sheath composite cross section so that the mass ratio of the sheath part to the mass of the fiber is 50% by mass, and finely drawn by a suction device to a fineness of 3.3 dTex. After the yarn group discharged from the suction device was opened, it was collected and accumulated on the moving collecting surface to obtain a nonwoven web in which long fibers were accumulated. This non-woven web is embossed (21% area ratio of embossed protrusions)
It was introduced into a hot embossing device consisting of a flat roll and a flat roll, and subjected to a partial heat-pressing treatment under the conditions of a surface temperature of both rolls of 95 ° C. and a linear pressure of 294 N / cm to obtain a long-fiber nonwoven fabric having a basis weight of 40 g / m ² . .

[Production Example 2 of long-fiber non-woven fabric] As a sheath part,
Melting point 130 ° C, melt flow rate 20g / 10 minutes, Q
A fabric weight of 40 was obtained in the same manner as in Production Example 1 except that high-density polyethylene having a value of 4.9 and a density of 0.957 g / cm ³ was used.
A g / m ² core-sheath type long-fiber nonwoven fabric was produced.

[Production Example 3 of long-fiber non-woven fabric] As a sheath part,
Melting point 126 ° C, melt flow rate 25g / 10 minutes, Q
A core-sheath type continuous fiber nonwoven fabric having a basis weight of 40 g / m ² was produced in the same manner as in Production Example 1 except that a linear low-density polyethylene having a value of 3.7 and a density of 0.925 g / cm ³ was used.

[Production Example 4 of long-fiber non-woven fabric] As the core part,
Melting point 159 ° C., melt flow rate 48 g / 10 min,
A core-sheath type long-fiber nonwoven fabric having a basis weight of 40 g / m ² was prepared in the same manner as in Production Example 1 except that polypropylene having a Q value of 2.2 and a density of 0.920 g / cm ³ was used and the spinning temperature was 230 ° C. Manufactured.

Table 1 shows the openability of the yarn groups discharged from the suction device in Production Examples 1 to 4. In addition, Production Example 1
Table 1 shows the physical properties of the long-fiber nonwoven fabrics obtained in Nos. 4 to 4.

[0047]

[Table 1]

As is clear from Table 1, the long fiber nonwoven fabric of Production Example 1 is excellent in nonwoven fabric strength and thermal adhesiveness,
The spreadability in the spunbond method was also good, and the texture of the obtained nonwoven fabric was extremely excellent.

On the other hand, the long fiber non-woven fabric of Production Example 2 is
Nonwoven fabric strength and openability were excellent as in Production Example 1, but
There was almost no heat sealability in the low temperature range (100 to 120 ° C.), which was not the object of the present invention.

The long-fiber non-woven fabric of Production Example 3 was in a state in which the yarn groups were remarkably adhered to each other, the fibers were hardly opened, the texture was poor, and the non-woven fabric product could not be used.

The long-fiber nonwoven fabric of Production Example 4 had relatively good openability, but the nonwoven fabric strength and heat sealability were significantly inferior to those of Production Example 1, and it is not the object of the present invention. There wasn't.

Example 1 The long fiber nonwoven fabric obtained in Production Example 1 and a microporous film were laminated. That is, one side of the long fiber non-woven fabric obtained in Production Example 1 was brought into contact with a roll heated to 80 ° C., and then the microporous film made of linear low density polyethylene and the long fiber non-woven fabric were heated. Lay them so that the surface in contact with the roll is the film side, 10
By passing between a pair of rolls heated to 0 ° C. and applying pressure, the two were stuck together to obtain a polyolefin film composite.

The obtained polyolefin-based film composite had good adhesion between the long-fiber nonwoven fabric and the microporous film, and maintained the moisture permeability and texture of the microporous film.

Comparative Example 1 Micropores were obtained in the same manner as in Example 1 except that the long fiber nonwoven fabric obtained in Production Example 2 was used in place of the long fiber nonwoven fabric obtained in Production Example 1. It was laminated with a film. As a result, the microporous film did not adhere to the long-fiber nonwoven fabric, and a composite could not be obtained.

Comparative Example 2 In Example 1, the long fiber nonwoven fabric obtained in Production Example 2 was used in place of the long fiber nonwoven fabric obtained in Production Example 1, and the temperature of a pair of heated rolls was set to 130 ° C. Other than the setting,
The microporous film was attached in the same manner as in Example 1. As a result, the resulting composite was unsatisfactory in appearance because the microporous film shrank and the surface became uneven, and the pores of the microporous film were crushed and the moisture permeability was not maintained.

[0056]

In the core-sheath type composite long fibers constituting the long-fiber nonwoven fabric used in the present invention, the sheath has a density of 0.89 to 0.92.
0 g / cm ³ , polyethylene having a melting point of 75 to 115 ° C., and the core portion made of polyester having a melting point of 45 ° C. or more higher than the melting point of the polyethylene, resulting in excellent flexibility, texture, and texture, and the core portion. The polyester has a high nonwoven fabric strength, and the sheath has a low melting point and low density polyethylene, so it is good even in the low temperature range (around 100 ° C). Has excellent thermal adhesiveness. Further, since the difference in melting point between the core and the sheath is large, high strength can be maintained even in the heat-sealed portion without the core being damaged by heat.

[0057]

Therefore, the long-fiber nonwoven fabric and the microporous polyethylene film are laminated (combined) by laminating or softening the polyethylene in the sheath portion of the core-sheath type composite long-fiber. The body does not undergo large heat shrinkage in the microporous polyethylene film and retains microporosity, and is suitable for use in packaging materials and sanitary materials that require strength, flexibility and heat sealability at the same time. it can.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4L047 AA14 AA21 AA27 AB03 AB10                       BA08 BB01 BB09 CA06 CB01                       CC03 CC14 CC15

Claims (2)

[Claims] 1. A composite of a long-fiber non-woven fabric comprising a core-sheath type composite continuous fiber and a microporous polyethylene film, wherein the core-sheath type composite continuous fiber has a sheath portion having a density of 0.890 to.
It is made of polyethylene with 0.920 g / cm ³ and a melting point of 75 to 115 ° C., and the core part has a melting point of 4 or more than the melting point of the polyethylene.
A polyolefin-based film composite comprising a polyester having a high melting point of 5 ° C. or more, wherein the polyethylene in the sheath is melted or softened to form a composite of the long-fiber nonwoven fabric and the microporous polyethylene film. . 2. The polyethylene of the sheath is obtained by a metallocene-based polymerization catalyst, and its Q value (weight average molecular weight / number average molecular weight) is 1.5 to 3.5. Polyolefin film composite.