JPH0230514A - Ultrahigh molecular-weight biaxially oriented polyethylene film and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a low water vapor permeable factor and kinetic coefficient of friction and excellent shock strength and tensile strength at fracture point by making use of ultrahigh-molecular weight polyethylene whose intrinsic viscosity [eta] measured within a decalin solvent at 135 deg.C is at least 5dl/g. CONSTITUTION:A skived sheet or an inflated film comprised of ultrahigh- molecular weight polyethylene whose intrinsic viscosity [eta] measured within a decalin solvent at 135 deg.C is at least 5dl/g is made into a thickness of 0.5-500mum by orienting at least four times respectively in a longitudinal and lateral directions under a temperature range extending from a temperature lower by 10 deg.C than the melting point of the ultrahigh-molecular weight polyethylene to a temperature higher by 15 deg.C than the melting point of the same at an orientation rate of not exceeding 30mm/minute. Draw ratios of a longitudinal and lateral directions are both at least four times, a thickness is 0.5-500mum, moreover shock strength is at least 5000kg.cm/cm, tensile strength at fracture point is at least 700kg/cm<2>, a kinetic coefficient of friction is not exceeding 0.2 and a water vapor factor is less than 0.45g.mm/m<2>.24 hours, in an obtained ultrahigh-molecular weight polyethylene biaxially oriented film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a uniaxially stretched film made of ultra-high molecular weight polyethylene and a method for producing this biaxially stretched film. The present invention also relates to a thin axially stretched film with excellent sliding properties and a method for producing the biaxially stretched film.

Technical background of the invention and its problems Ultra-high molecular weight polyethylene has superior properties such as impact resistance, abrasion resistance, chemical resistance, and tensile strength compared to conventionally used general-purpose polyethylene. Therefore, its use as an engineering plastic is expanding.

However, compared to general-purpose polyethylene, ultra-high molecular weight polyethylene has an extremely high melt viscosity and low fluidity, so when molding such ultra-high molecular weight polyethylene, conventional inflation molding methods etc. Molding methods such as extrusion molding or injection molding have the problem of being difficult to use. For this reason, compression molding is mainly used as a method for molding ultra-high molecular weight polyethylene, and the only other method proposed is to extrude rods and the like at a very low speed.

In addition, as a method for producing ultra-high molecular weight polyethylene film, after sintering ultra-high molecular weight polyethylene powder, it is heated to a temperature higher than the melting point of the ultra-high molecular weight polyethylene used, and heated and compressed between a pair of belts. A method of producing a film by cooling (see Japanese Patent Publication No. 48-11576), or an ultra-high molecular weight polyethylene sheet obtained by sintering ultra-high molecular weight polyethylene powder from a temperature above the secondary transition temperature to a melting point A method of orienting using a pressure roll at a temperature within the range below (see JP-A-53-45376) has been proposed.

Although it is possible to produce a film with a good appearance by the above method, since the melt viscosity of ultra-high molecular weight polyethylene is extremely high, it is very difficult to keep the thickness of the obtained film below a certain level. In addition, especially in the latter method, since the heating temperature is lower than the melting point, the viscosity of the ultra-high molecular weight polyethylene becomes even higher, making it impossible to obtain a thin film even if rolling is performed using a pressure roll. Ta.

In addition, one possible method for producing thin films is to stretch a thick sheet, but since ultra-high molecular weight polyethylene has a very high molecular weight, even if normal stretching conditions are used, the film will There were problems in that smooth stretching could not be performed, such as frequent cutting.

Another possibility is to roll a sheet of ultra-high molecular weight polyethylene using a pressure roll to produce a thin film, but this is because heating crystalline polyethylene above its melting point usually increases its stickiness and decreases its viscosity. In fact, even with ultra-high molecular weight polyethylene, as described in the above-mentioned Japanese Patent Application Laid-open No. 53-45376, above the melting point, the molten resin sticks to the pressure roll, resulting in poor performance. It is stated that it is not possible to produce a film that has an external appearance.

On the other hand, the present applicant has already filed an application for a method for producing a biaxial film of ultra-high molecular weight polyethylene by extrusion molding (see Japanese Patent Laid-Open No. 59-227420).

The method for producing a biaxially stretched film according to this application is a method in which ultra-high molecular weight polyethylene is mixed with a large amount of plasticizer and then extruded.

The biaxially oriented ultra-high molecular weight polyethylene obtained by this method has extremely excellent mechanical properties such as tensile strength and impact strength, but a considerable amount of plasticizer remains in the resulting film, and When the plasticizer is extracted and removed, voids are created in the area where the plasticizer was present, which increases the moisture permeability of the resulting ultra-high molecular weight polyethylene film, making it difficult to use in some applications. there were.

SUMMARY OF THE INVENTION The present invention aims to solve the problems associated with the prior art as described above. It is an object of the present invention to provide a molecular weight polyethylene film and a method of manufacturing this film.

Nine skin examples and 1 The ultra-high molecular weight polyethylene biaxially stretched film according to the present invention has an intrinsic viscosity [η] measured at 135°C in a decalin solvent.
It is made of ultra-high molecular weight polyethylene with a molecular weight of 5 dl/g or more, has a stretching ratio of 4 times or more in both the longitudinal and lateral directions, has a thickness of 0.5 to 500 μm, and has an impact strength of 5000 kg-CIII/■ The dynamic friction coefficient is 0.02 or less, the tensile strength at break is 700 kg/cd or more, and the moisture permeability coefficient is 0.45 g-mm/rr.
It is characterized by being less than 24 hours.

Furthermore, the method for producing a biaxially stretched ultra-high molecular weight polyethylene film according to the present invention includes a skive sheet or a blown film made of ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of 5 dl/g or more as measured in a decalin solvent at 135°C. is stretched 4 times or more in the longitudinal and transverse directions, respectively, at a stretching speed of 30 mm/min or less at a temperature range of 10° C. lower than the melting point of the ultra-high molecular weight polyethylene to 15° C. higher than the melting point of the ultra-high molecular weight polyethylene. It is characterized by having a thickness of ~500 μm.

According to the production method of the present invention, a thin biaxially stretched film can be produced using ultra-high molecular weight polyethylene with low formability.

The ultra-high molecular weight polyethylene biaxially stretched film produced in this manner is thin, has a low moisture permeability coefficient and a low dynamic friction coefficient, and has high impact strength and tensile strength at break.

Detailed Description of the Invention The biaxially stretched ultra-high molecular weight polyethylene film of the present invention and the method for producing the ultra-high molecular weight polyethylene film will be specifically described below.

The ultra-high molecular weight polyethylene biaxially stretched film of the present invention is
The intrinsic viscosity [η] measured at 135°C in decalin solvent is 5
It is a biaxially stretched film made of ultra-high molecular weight polyethylene of dl/g or more and has a thickness of 0.5 to 500 μm. In this biaxially stretched film, the stretching ratio in both the longitudinal direction and the transverse direction is 4 times or more.

The biaxially stretched film of the present invention has a dynamic friction coefficient of 0.
．． 2 or more, the tensile strength at break is 700 kg/aJ or more in both the longitudinal and lateral directions, and the impact strength is 5000 kg/aJ or more.
kg-am/an or more, and the moisture permeability coefficient is 0
, 45 g-mm/rrr・less than 24 hours.

The biaxially stretched film according to the present invention is prepared in a decalin solvent with 13
It can be produced by biaxially stretching a blown film or skive sheet made of ultra-high molecular weight polyethylene having an intrinsic viscosity [η] of 5 dJl/g or more measured at 5° C. at a specific temperature.

The ultra-high molecular weight polyethylene used in the present invention is a polymer or copolymer containing a structural unit derived from ethylene. In the present invention, when the ultra-high molecular weight polyethylene is a copolymer, the structural units constituting the ultra-high molecular weight polyethylene together with the ethylene structural unit include propylene,
Structural units derived from α-olefins such as 1-butene, 1-hexene, 1-octene and 4-methyl-1-pentene can be mentioned.

The ultra-high molecular weight polyethylene used in the present invention has an intrinsic viscosity [η] measured at 135°C in a decalin solvent or 5 dj/s.
r or more, preferably 8 to 25 (Hit). When ultra-high molecular weight polyethylene with the above-mentioned intrinsic viscosity [η] of less than 5 dl/g is used, it has excellent properties such as sufficient tensile strength at break. However, by using ultra-high molecular weight polyethylene with an intrinsic viscosity of 8 dj/g or more, it is possible to obtain a biaxially stretched film with particularly good properties such as mechanical strength such as tensile strength at break. The upper limit of the intrinsic viscosity [η] of the ultra-high molecular weight polyethylene used in the present invention is not particularly limited, but for example, ultra-high molecular weight polyethylene having an intrinsic viscosity exceeding 25 dfJ/f is used. In this case, the melt viscosity becomes too high, making it difficult to produce a blown film or skive sheet used in producing an axially stretched film.

The melt flow rate (HFR: 8S'THD12) of the ultra-high molecular weight polyethylene used in the present invention is
38, F) is usually 0.01 g/10 minutes or less.

The weight average molecular weight of such ultra-high molecular weight polyethylene is usually within the range of 50 to 500.

Such ultra-high molecular weight polyethylene is usually crystalline.

In the present invention, ultra-high molecular weight polyethylene can be used alone, but additives such as heat-resistant stabilizers, weather-resistant stabilizers, lubricants, nucleating agents, dyes, pigments, and fillers may be used for the purpose of the present invention. may be added as long as it does not impair it.

The biaxially stretched film according to the present invention is manufactured using a blown film or skive sheet manufactured using ultra-high molecular weight polyethylene as described above.

Inflated film is an example of a patent application filed in 1986.
It can be manufactured according to the method for manufacturing a blown film described in Japanese Patent No. 75792 and the like.

FIG. 1 shows an example of a manufacturing apparatus capable of manufacturing a blown film used in manufacturing the biaxially stretched film of the present invention.

The blown film manufacturing apparatus preferably used in the present invention is comprised of an extruder 1 and a tube tie 2 connected to the extruder 1.

The extruder 1 consists of a cylindrical grooved cylinder 3 having a groove 31 inside, and a screw 4 rotatably mounted inside the cylindrical grooved cylinder 3. A tube tie 2 is connected to the screw 4. A mandrel 5 that is joined and rotates as the screw 4 rotates, and an outer die 6 that has a through hole into which the mandrel 5 is inserted.
It consists of

Further, the screw 4 and the mandre 5 are provided with a gas introduction pipe 7 through which gas is blown to expand the ultra-high molecular weight polyethylene extruded from the tip of the tube tie 2.

In order to produce a blown film using ultra-high molecular weight polyethylene, the compression ratio between the grooved cylinder 3 and the screw 4 is usually 1 to 2.5, preferably 1.3.
It is desirable to use equipment within the range of ~1.8. In addition, the L/L of the tube tie 2 in such a device is
The value of D is usually 5 or more, preferably 10 or more,
Particularly preferably, it is within the range of 20 to 70. Further, the ratio (S1/S2) between the cross-sectional area S1 of the resin flow path in the inlet portion 21 of the tube tie 2 and the cross-sectional area S of the resin flow path in the intermediate portion 22 of the tube tie 2 is usually 0.5 to 3. 0, preferably 1.0 to 2.0, and the ratio of the cross-sectional area S2 of the resin flow path in the intermediate portion 22 to the cross-sectional area S3 of the resin flow path in the outlet portion 23 of the tube tie 2 (S2/S3). is usually 1.0 to 3.0
, preferably 1.1 to 2.0.

Ultra-high molecular weight polyethylene is charged from the hopper 8 of the above-mentioned apparatus 6. The charged ultra-high molecular weight polyethylene is heated to a temperature higher than the melting point of the ultra-high molecular weight polyethylene, preferably 200 to 330, by heating means provided in extrusion a1. ℃ and becomes molten. The ultra-high molecular weight polyethylene thus molten is sent toward the duplex tie as the screw 4 rotates. tube die 2
The ultra-high molecular polyethylene sent to the tube moves through a gap formed by the mandrel 5 rotating together with the screw 4 and the outer die 6 toward the exit portion 23 of the tube die. In the present invention, from this inlet portion 21 to the intermediate portion 22
The temperature during heating is preferably 180 to 330'C. Further, the temperature from the intermediate portion 22 to the outlet portion 23 is preferably 136 to 170°C. By setting the temperature to such a temperature, it is possible to effectively prevent lund melt fracture from occurring inside the tube tie.

A compressed gas such as air is blown into the extruded ultra-high molecular weight polyethylene tube through the gas introduction pipe 7 so that the swelling ratio of the tubular film 9 is 1.1 to 20 times. In the present invention, the compressed gas is preferably air at a pressure of 3 to 20 atmospheres. By blowing compressed gas in this way, the thickness of the tubular film can be reduced.
Usually 10 to 1000 μm, preferably 30 to 800 μm
become. After inflating the tube in this manner, a blown film can be manufactured by cooling the tube with a cooling ring 101, folding the film with a stabilizer plate 102, pressing it with a pinch roll 103, and winding it up.

Further, the skive sheet used in the present invention is produced by manufacturing a rod-shaped body, preferably a cylinder, made of ultra-high molecular weight polyethylene having the above-mentioned intrinsic viscosity, and then rotating the rod-shaped body or cylinder. Depending on the cutting blade, the sheet thickness is usually 10 to 1000 μm,
Preferably, it can be manufactured by cutting into a sheet to have a thickness of 30 to 800 μm.

The blown film or skive sheet thus obtained was blown into 4 pieces in each of the longitudinal and transverse directions.
Particularly in the present invention, it is preferable to stretch at a stretching ratio of 4 to 20 times in the machine direction and 4 to 20 times in the transverse direction.

In the present invention, the above-described stretching of the blown film or skive sheet 1 is carried out at a temperature ranging from io'c lower than the melting point of the ultra-high molecular weight polyethylene constituting the film or skive sheet 1 to a temperature 15° C. higher than the melting point. This is done by heating the blown film or skive sea 1 within a range. By heating the blown film or skive sheet to the above temperature range, it can be heated to
It becomes possible to perform stretching more than twice as much. In particular, in the present invention, the heating temperature of the blown film or skive sheet is varied from 10°C lower than the melting point to 15°C lower than the melting point.
It is preferable to use a higher temperature.

Specifically, the melting point of ultra-high molecular weight polyethylene is usually 1
Since the temperature is within the range of 25 to 145°C, in the method for producing a biaxially oriented polyethylene film according to the present invention, the blown film or skive sheet is usually heated within the range of 115 to 160°C, preferably 120 to 150°C. Biaxial stretching is performed by heating to a temperature of .

Furthermore, the stretching under the above temperature conditions is 30
It is carried out at a rate of less than 1 TllII/min. If the stretching speed is higher than 30 mm/min, there is a risk that the film will break during stretching. In particular, in the present invention, the stretching speed is
It is preferable to set the speed in the range of 30 mm/min.

Various methods can be used to biaxially stretch the blown film or skive sheet as described above. Specifically, after stretching in the longitudinal direction, further stretching in the transverse direction; A method of simultaneously stretching in the axial and transverse directions, a method of biaxially stretching and then sequential stretching in either direction, a method of biaxially stretching and then further stretching in both directions, a blown film or a skive. Examples include a so-called vacuum forming method in which stretching is performed by reducing the pressure in a space formed by a sheet and a mold.

Biaxial stretching as described above can be performed using a known device.

In the present invention, the blown film or the skive film may contain a plasticizer such as a hydrocarbon plasticizer within a range that does not change the properties of the biaxially stretched film obtained. The content of hydrogen-based plasticizers etc. should be below 15% by weight.

The biaxially stretched film according to the present invention thus obtained has an impact strength of 5000 kg-an/am or more, preferably 500 to 4000 kg-cm/am, and a dynamic friction coefficient of 0.2 or less, preferably 0.05~0.
2, and the tensile strength at break is 700 kg/d or more,
Preferably 700-5000 kg/af! and the moisture permeability coefficient is less than 0.45 g-mm/rrf・24 hours, preferably 0.05 to 0.45 g-mm/M・24
It's time.

As described above, the biaxially stretched film according to the present invention has excellent mechanical strength, a low friction coefficient, and a low moisture permeability coefficient.

That is, the biaxially stretched film according to the present invention has excellent properties not found in conventional polyethylene films, and has lower moisture permeability than ultra-high molecular weight polyethylene films obtained by conventional methods.

Utilizing these characteristics, the biaxially stretched film according to the present invention can be used not only for conventional uses of polyethylene films such as packaging materials, but also for applications that require high strength, low moisture permeability, thin film formation, and high lubricity. fields, such as capacitor film,
It can be used as an insulating film, etc.

The biaxially stretched film according to the present invention can be used alone, or if necessary, the surface can be subjected to corona discharge treatment or anchor treatment, and it can be laminated with other resins, paper, metal foil, etc. You can also do that.

Effects of the Invention The biaxially stretched film made of ultra-high molecular weight polyethylene of the present invention has an impact strength of 5000 kg/CIII/C1n or more, a dynamic friction coefficient of 0.2 or less, and a tensile strength at break of 700 kg/cIlY or more. , moisture permeability coefficient is 0.
45g-rnm/rr?・It lasts less than 24 hours, has a thickness of 0.5 to 500 μm, and has excellent properties such as mechanical strength and lubricity, as well as low moisture permeability.

A biaxially stretched ultrahigh molecular weight polyethylene film having such excellent properties can be produced by stretching a blown film or skive sheet made of ultrahigh molecular weight polyethylene under specific stretching conditions.

[Examples] Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples as long as the gist thereof is not exceeded.

A blown film made of ultra-high molecular weight polyethylene was manufactured using a blown film manufacturing apparatus shown in FIG.

The conditions for manufacturing the blown film are as follows.

That is, screw outer diameter 30 mm, screw effective length (L/D) 34, flat pitch 20 +++ m (constant), screw compression ratio 1.8, adapter length 200 I.
T1m, tube tie length 550 mm, tube tie effective length (L/D) 25, die exit outer tie inner diameter 2
2mm, mandrel outer diameter 13mm, S1/52=1.4
0, S2/53-157, and tube tie length (L
/D) 25, tie outlet outer die inner diameter 22mm, tie outlet mandrel outer diameter 18ITIII1. S1/52-1
．． 40, S 2 /s 3 = 1.57, and a blown film manufacturing apparatus having a gas introduction tube with a diameter of 6 mm provided inside the screw and inside the tube tie mandrel was used. This manufacturing equipment further includes:
A cooling ring with an internal diameter of 66+nm, a stabilizer, a pinch roll and a film winder are provided.

Ultra-high molecular weight polyethylene [Intrinsic viscosity [η] measured at 135°C in Tecarin solvent -16.5 dJ/g, MFR: O
, less than 1 g/10 min, melting point: 136°C and bulk density:
0,45 g10A] of powdered resin (trade name HIZEX MILLION 240M, manufactured by Mitsui Petrochemical Industries, Ltd.) was used, the temperature of the press was 280°C, and the temperature of the adapter was 270°C.
℃, set the temperature of the die base to 180℃5 and the temperature of the tie end to 150'C, and set the screw rotation speed to 15rl.
) III, and while pulling at a speed of 1.2 m/min with pinch rolls, cool the tube by blowing compressed air from the 6-diameter gas introduction pipe provided inside the screw and the mandrel of the tube tie. Link inner diameter 6
An ultra-high molecular weight polyethylene inflation tile having a folding width of 104 ITlan and a thickness of 200 μm was produced by inflating it to a size that touched 6 tubes (swell ratio -3).

Table 1 shows the thickness, tensile strength at break (TS), impact strength, moisture permeability coefficient, and friction coefficient of this blown film (Sample 1). In addition, the intrinsic viscosity and MFR of the ultra-high molecular weight polyethylene used are also described.

A sample of 90 x 90 mm was cut out from the blown film obtained as above, and placed in an axial stretching machine (
(manufactured by Toyo Seiki Seisakusho ■), the blown film was heated to 140°C, the longitudinal stretching ratio was set to 4 times, the transverse direction stretching ratio was set to 4 times, and biaxial stretching was performed at a stretching speed of 20 nm/min. The thickness, TS, impact strength, moisture permeability coefficient and friction coefficient of the obtained ultra-high molecular weight polyethylene biaxially stretched film are shown in Table 1.

In the present invention, TS, impact strength, moisture permeability coefficient, and friction coefficient are values measured by the method described below.

Tensile point at break Crab test piece shape JIS 6781 Between chucks: 86 mm Tensile speed: 200 mm/min Temperature = 23° A tensile test was conducted under these conditions, and from this value the tensile strength at break (TS: kg/-) was calculated. I asked for it.

Impact strength: Film impact tester manufactured by Toyo Seiki ■ Capacity: 30 kg-■ Impact type spherical surface: 1 inch φ The breaking strength (kg-(7)/cI11) was determined.

Tear strength: Tear strength (k+r/an) was determined using an Elmendorf tear tester manufactured by Toyo Seiki ■.

Moisture permeability coefficient: Based on JIS Z 0208, temperature 40
Moisture permeability (g/rrt'・under conditions of ℃ and 90% humidity)
The moisture permeability coefficient (t-mm/rrl' 24 hours) was determined by dividing by 1/thickness ('m).

1. The ultra-high molecular weight polyethylene used in Example 1 and paraffin wax (melting point -69°C, molecular weight 460°C) were mixed at a weight ratio of 50:50.

The MFR of this mixture was 0.037 g/10 minutes.

A biaxially stretched film was produced using this mixture under the following conditions.

The above mixture was melted using a screw extruder with a diameter of 30 m + n and L/D = 25, then extruded into a sheet using a coat bunker type T-tie (set temperature: 280 ° C.) with a die width of 30 >, and cooled with an extrusion roll. A sheet with a thickness of 200 μm was obtained.

Next, a 90 mm x 90 mm sample was cut out from this sheet and biaxially stretched using a biaxial stretching device (manufactured by Toyo Seiki Seisakusho ■) at a stretching temperature of 120'C to produce a biaxially stretched film. .

Table 1 shows the thickness, TS, impact strength, moisture permeability coefficient, and friction coefficient of the obtained ultra-high molecular weight polyethylene biaxially stretched film.

In addition, this biaxially stretched film contains 50% by weight-n″1
' It contained paraffin hooks.

夛（-12L

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view schematically showing an example of a forming apparatus capable of producing a blown film used in producing the biaxially stretched film of the present invention. 1... Extruder 2... Tube tie 3... Grooved cylinder 4... Screw 5... Mandrel 6... Outer tie 7... Gas introduction tube

Claims (1)

[Claims] 1) Intrinsic viscosity [η] measured at 135°C in decalin solvent
It is made of ultra-high molecular weight polyethylene with a polyethylene of 5 dl/g or more, has a stretching ratio of 4 times or more in both the longitudinal and lateral directions, has a thickness of 0.5 to 500 μm, and has an impact strength of 5000 kg cm/cm. above, the tensile strength at break is 700 kg/cm^2 or more, and the coefficient of dynamic friction is 0.
2 or less, and the moisture permeability coefficient is 0.45g・mm/m^2・
An ultra-high molecular weight polyethylene biaxially stretched film characterized in that it lasts for less than 24 hours. 2) Intrinsic viscosity [η] measured at 135°C in decalin solvent
Stretching a skive sheet or blown film made of ultra-high molecular weight polyethylene having a polyethylene of 5 dl/g or more at a rate of 30 mm/min or less in a temperature range from 10° C. lower than the melting point of the ultra-high molecular weight polyethylene to 15° C. higher than the melting point. Characterized by stretching at a speed of 4 times or more in the longitudinal and transverse directions to a thickness of 0.5 to 500 μm, and having an impact strength of 5000 kg cm/cm or more and a tensile strength at break of 700 kg/cm. ^2 or more,
Dynamic friction coefficient is 0.2 or less, moisture permeability coefficient is 0.45g
- A method for producing an ultra-high molecular weight polyethylene biaxially stretched film having a stretching time of less than mm/m^2/24 hours.