JPH0785907B2 - Ultra-high molecular weight polyolefin biaxially stretched film and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched ultra high molecular weight polyolefin film and a method for producing the same, and more specifically, it is obtained from a mixture of an ultra high molecular weight polyolefin and a specific hydrocarbon plasticizer. A biaxially stretched film (hereinafter sometimes simply referred to as "ultra high molecular weight polyolefin biaxially stretched film") and a method for producing the same, particularly, a stretching ratio in the longitudinal direction after solidification is 3 times or more and in the transverse direction. Of 3 or more (provided that the longitudinal draw ratio is 5 or more and the transverse draw ratio is 5 or more, the initial elastic modulus is 7300 kg / cm ² or more, and the breaking strength is 910 kg / a cm but ^two or more), ultrahigh molecular weight polyolefin biaxially stretched film breaking strength is 720 kg / cm ^2, and, producing side of the biaxially oriented film On.

[0002]

2. Description of the Related Art Ultra-high molecular weight polyethylene, which is a typical example of ultra-high molecular weight polyolefin, is superior to general-purpose polyethylene in impact resistance, abrasion resistance, chemical resistance, tensile strength, etc. and is used as an engineering plastic. Is spreading. However, compared with general-purpose polyethylene, it has a very high melt viscosity and poor fluidity, so it is very difficult to mold it by conventional extrusion molding, most of it is molded by compression molding, and some rods are extremely The current situation is that extrusion is performed at a low speed.

As a method for producing an ultra high molecular weight polyolefin, after sintering ultra high molecular weight polyethylene powder, it is heated to a temperature not lower than the melting point of polyethylene and heated, pressed and cooled between two belts. A method for producing a film (Japanese Patent Publication No. 48-11576) or a method for orienting a sintered ultra-high molecular weight polyethylene sheet with a pressure roll in a temperature range from the second-order transition point to below the melting point (JP-A-53-45376). However, it takes a long time to mold because the powder of ultrahigh molecular weight polyethylene is sintered and made into a sheet, and in the latter method, ultrahigh molecular weight polyethylene has a high melt viscosity and fluidity. Since it has poor properties, it was almost impossible to obtain a thin film even if it was oriented with a pressure roll at a temperature below the melting point.

On the other hand, it is well known that a film such as a biaxially oriented polypropylene film (OPP film) is biaxially oriented to produce a high-strength thin film, but unlike ordinary polypropylene, an ultrahigh molecular weight polyolefin. It is almost impossible to obtain a biaxially stretched film because the viscosity is extremely high in a stretchable temperature range that leads to high strength.

[0005]

In view of such circumstances, the inventors of the present invention have earnestly studied a method for obtaining a biaxially stretched film of an ultrahigh molecular weight polyolefin, and as a result, have found that a hydrocarbon-based plasticizer specific to the ultrahigh molecular weight polyolefin is used. It was found that a biaxially stretched film can be obtained by mixing
The present invention has been reached.

[0006]

Means for Solving the Problems That is, according to the present invention, an ultrahigh molecular weight polyolefin A having an intrinsic viscosity [η] of at least 5 dl / g and a stretching ratio in the machine direction of 3 times or more and a transverse direction after once solidified. The draw ratio in the machine direction is 3 times or more (however, the draw ratio in the machine direction is 5 times or more, and the draw ratio in the transverse direction is 5 times or more, and the initial elastic modulus is 7300 kg / c.
m ² or more and a breaking strength of 910 kg / cm ² or more) and a breaking strength of 720 kg / cm ² or more, and an ultrahigh molecular weight polyolefin biaxially stretched film, and at least an intrinsic viscosity [ η] is 5.0
It contains an ultrahigh molecular weight polyolefin A of dl / g or more and a hydrocarbon-based plasticizer B having a boiling point higher than the melting point of the ultrahigh molecular weight polyolefin, and has a melt flow rate of 0.
A mixture of 005 to 50 g / 10 min is extruded, and once solidified, at a stretching temperature below the melting point of the ultra-high molecular weight polyolefin, the stretching ratio in the longitudinal direction is 3 times or more and the stretching ratio in the transverse direction is 3 times or more (however, stretch ratio in the longitudinal direction 5 times or more, and stretching ratio in the transverse direction is not more 5 times or more, the initial elastic modulus excluding and breaking strength 7300kg / cm ² or 910 kg / cm ² or higher) twin A method for producing a biaxially stretched ultra high molecular weight polyolefin film having a breaking strength of 720 kg / cm ² or more, which is characterized by stretching.

The ultrahigh molecular weight polyolefin A used in the present invention has an intrinsic viscosity [η] at 135 ° C. of a decalin solvent of 5 dl / g or more, preferably 7 to 30 dl / g. If [η] is less than 5 dl / g, a high-strength film, which has a low molecular weight and is characteristic of an ultra-high molecular weight polyolefin, may not be obtained. On the other hand, the upper limit of [η] is not particularly limited, but 30 dl / g If the amount exceeds the above range, the melt viscosity will be high and the extrusion moldability will be poor even if the hydrocarbon plasticizer B described later is added. Such ultra high molecular weight polyolefin A
Is ethylene, propylene, 1-butene, 4-methyl-
Among polyolefins obtained by polymerizing 1-pentene, 1-hexene and the like by so-called Ziegler polymerization, those having a much higher molecular weight are included. Among them, ultra-high molecular weight polyethylene mainly composed of ethylene is preferable because it is excellent in cold resistance, impact resistance and self-lubricating property.

Hydrocarbon plasticizer B used in the method of the present invention
Has a boiling point higher than the melting point (A) of the ultrahigh molecular weight polyolefin A, and preferably has a boiling point of the melting point (A) +
A melting point (B) of 10 ° C. or higher and a melting point (B) of 350 ° C. or lower, and more preferably a melting point (A) of + 50 ° C. or higher.
Is a hydrocarbon-based plasticizer having a temperature of 40 to 120 ° C. and a molecular weight of 2000 or less.

Those having a boiling point not higher than the melting point (A) of the ultrahigh molecular weight polyolefin A are those mentioned above.
Since a raw sheet which is mixed with and melt-extruded is foamed, a good biaxially stretched film may not be obtained. In addition, if the amount of liquid at room temperature is small, it does not hinder extrusion moldability,
When a large amount is used, for example, when using a screw extruder or the like, the screw and the mixture may co-rotate and a steady extrusion molding may not be possible. Therefore, the melting point (B) is 40 ° C.
The above hydrocarbon plasticizers are most preferable.

The molecular weight of the hydrocarbon type plasticizer B is such that the MFR of the mixture is 0.005 to 50 g / 10 min, preferably 0.
01 to 50 g / 10 min, more preferably 0.
It is not particularly limited as long as it is in the range of 1 to 10 g / 10 min, but if the molecular weight exceeds 2000, a large amount will be added to bring the MFR into the above range, and further, the film. When it is set, there is a possibility that the excellent characteristics which are the original characteristics of the ultra high molecular weight polyolefin may not be exhibited. The MFR in the present invention is ASTM
According to D1238, polypropylene was condition L, poly-4-methyl-1-pentene was condition T, and other polyolefins including polyethylene were condition E.

The above-mentioned hydrocarbon type plasticizer B used in the present invention,
Then, specifically, n-decane, n-dodecane, doco
N-alkanes such as sun, tricosane, tetracosane, etc.
Dynamic paraffin, kerosene, paraffin wax, low molecular weight
Polyethylene or low molecular weight polypropylene, low molecular weight
Aliphatic carbon such as α-olefin oligomer such as polybutene
Hydrogenated compounds, naphthalene, tetralin, diethyl ester
Aromatic carbon such as benzene, decalin and low molecular weight polystyrene
Hydrogenated compounds or hydrogenated derivatives thereof, C _Five System oil
Resins, their halides, capric acid, LA
Uric acid, palmitic acid, stearic acid, behenic acid,
Higher fatty acids such as oleic acid and erucic acid, capryl alco
Alcohol, lauryl alcohol, palmityl alcohol, su
Higher aliphatic alcohols such as thearyl alcohol, palmi
Tin acid amide, stearic acid amide, oleic acid amide
Higher fatty acid amides such as calcium stearate, lau
Metal soaps such as calcium phosphate, zinc stearate, etc.
Tearic acid monoglyceride, oleic acid monoglyceride
And higher fatty acid esters such as stearic acid diglyceride
Etc. As the ultra high molecular weight polyolefin A
If ultra high molecular weight polyethylene is selected as
As a hydrogenated plasticizer B, it is a paraffin-based compound from the viewpoint of compatibility.
Waxes are preferred.

The paraffin wax is mainly composed of a saturated aliphatic hydrocarbon compound, specifically, n-alkane having 22 or more carbon atoms such as docosane, tricosane, tetracosane, triacontane or the like. , A so-called paraffin wax separated and purified from petroleum, a low-molecular weight polyethylene wax which is a low molecular weight polymer obtained by copolymerizing ethylene or ethylene with another α-olefin. , High-pressure polyethylene wax, ethylene copolymer wax or medium / low-pressure polyethylene, high-pressure polyethylene and other waxes whose molecular weight has been reduced by thermal degradation, and oxidation of those waxes or maleic acid-modified products Wax, maleic acid modified wax, etc. .

The melting point in the present invention is ASTM D34.
17 is a value measured by a differential scanning calorimeter (DSC). The molecular weight is the weight average molecular weight (Mw) obtained by the GPC method (gel permeation chromatography) under the following conditions. Apparatus: Waters 150C type column: Toyo Soda Kogyo Co., Ltd. TSK GMH-6 (6 mm φ × 600 mm) Solvent: o-dichlorobenzene (ODCB) Temperature: 135 ° C. Flow rate: 1.0 ml / min Injection temperature: 30 mg / 20 ml ODCB (injection amount 400 μl) The column elution volume was calibrated by the universal method using standard polyethylene manufactured by Toyo Soda Kogyo Co., Ltd. and Pretzshire Chemical Co.

In the method of the present invention, the hydrocarbon-based plasticizer B is added to and mixed with the ultrahigh molecular weight polyolefin A to obtain MF.
A mixture having R in the range of 0.005 to 50 g / 10 min, preferably 0.01 to 50 g / 10 min, more preferably 0.1 to 10 g / 10 min is melt-kneaded, extruded from a die, and once solidified, the above-mentioned ultrahigh It is a method of producing the above-mentioned high-strength ultrahigh molecular weight polyolefin biaxially stretched film by biaxially stretching at a temperature lower than the melting point of the molecular weight polyolefin A.

In the method of the present invention, if the MFR of the mixture of the ultrahigh molecular weight polyolefin A and the hydrocarbon plasticizer B is within the above range, the amount of the ultrahigh molecular weight polyolefin A is not particularly limited, but it is usually. Ultra high molecular weight polyolefin A
Is in the range of 15 to 80% by weight, preferably 30 to 70% by weight (the mixture is 100% by weight). If the amount of the ultrahigh molecular weight polyolefin A is less than 15% by weight, the amount of the hydrocarbon plasticizer B may be too large, and the extensibility of the extruded raw sheet may be impaired. On the other hand, when the amount of the ultrahigh molecular weight polyolefin A exceeds 80% by weight, the MFR is 0.005 even if the hydrocarbon plasticizer B is added.
In addition, the melt-extrusion is difficult, the extruded raw film has a rough surface, a large amount of stress is required during biaxial stretching, and the stretchability is poor.

The melt-kneading of the ultrahigh molecular weight polyolefin A and the hydrocarbon plasticizer B can be carried out, for example, by a Henschel mixer,
After mixing with a V-blender, a ribbon blender, a tumbler blender, etc., a screw extruder such as a single-screw extruder or a twin-screw extruder, a kneader, a Banbury mixer, etc.
It can be carried out at a temperature above the melting point to 350 ° C, preferably above the melting point + 50 ° C to 300 ° C. Melt kneading may be performed separately prior to extrusion molding of the film, or may be performed by a continuous method in which the film is extruded from a die while melt kneading with a screw extruder or the like.

The extrusion temperature is usually 150 to 350 ° C.,
It may preferably be carried out at a temperature of 190 to 300 ° C. If the extrusion temperature is lower than 150 ° C., the melt viscosity is high and the extrudability is poor, while if it exceeds 350 ° C., the ultrahigh molecular weight polyolefin may be deteriorated by heat and its molecular weight may be lowered. The film extruded by the above method is biaxially stretched at a temperature below the melting point (A) of the ultrahigh molecular weight polyolefin A, preferably below the melting point (A) and above 60 ° C.
If the stretching temperature is equal to or higher than the melting point (A), the orientation by stretching is insufficient and mechanical strength cannot be exhibited. When the stretching temperature is 60 ° C. or lower, a large amount of stress is required for stretching, which is not preferable.

The extruded raw film is biaxially stretched by a simultaneous biaxial stretching method by an inflation film method, a simultaneous biaxial stretching method by a tenter method, or a longitudinal direction by a roll or the like and then a transverse direction by a tenter. Examples include a sequential biaxial stretching method of stretching in a direction. Biaxial stretching is possible by any method as long as the stretching temperature during biaxial stretching is a temperature below the melting point (A) and at a temperature above the temperature at which the yield stress in the tensile test of ultrahigh molecular weight polyolefin A disappears. However, when the film is stretched at a temperature lower than the temperature at which the stress at the yield point disappears, the simultaneous biaxial stretching method is preferably used because the sequential stretching method causes longitudinal cracks in the film during transverse stretching.

When the extruded film is biaxially stretched, the molten film extruded from the die is cooled and once solidified, the film is heated again within the above temperature range. This method is preferable because the control of the temperature range is easy. Therefore, the stretching ratio during biaxial stretching in the present invention means the stretching ratio after the film extruded in the molten state is cooled and once solidified, and is usually 3 times or more in the longitudinal direction, preferably 5 times. Through 20
Double, and the horizontal direction is 3 times or more, preferably about 5 to 20 times. If the stretching ratio is less than 3 times, mechanical strength cannot be expressed by stretching.

When the stretching ratio exceeds 20 times, the thickness of the ultrahigh molecular weight polyolefin biaxially stretched film formed by stretching becomes 1/400 or less of that of the original film, and thus the stretching operation is difficult. There is. The ultrahigh molecular weight polyolefin A used in the present invention includes, in addition to the hydrocarbon plasticizer B, a heat resistance stabilizer, a weather resistance stabilizer, a lubricant, an antiblocking agent, a slip agent, a pigment, a dye, an inorganic filler, etc. Various additives to be added to the above may be blended within a range not impairing the object of the present invention.

The thickness of the biaxially stretched ultra high molecular weight polyolefin film of the present invention can be appropriately selected depending on the application, but is usually in the range of 50 to 0.5 μ, preferably 20 to 2 μ. The film may be used alone or may be subjected to corona discharge treatment or the like on one side or both sides, and may be subjected to anchor treatment if necessary, and other resin or paper,
It may be used by laminating it with cellophane or aluminum foil.

[0022]

The biaxially stretched ultra-high molecular weight polyolefin film of the present invention has high tensile strength, high impact strength and high elasticity which cannot be obtained by conventional ordinary polyolefin films, and is therefore a polyolefin film for packaging materials and the like. In addition to fields, it can be used in the fields of high elasticity and high strength films, and can also be used as a reinforcing material by compounding with various materials.
Furthermore, it can be used for capacitor films and insulating paper because it can be made ultra thin by high stretching. The biaxially stretched ultra-high molecular weight polyolefin film of the present invention, in which the hydrocarbon plasticizer B is evenly dispersed, is a fine secondary product produced by extraction with, for example, n-hexane or n-heptane. It is also highly suitable for functional materials such as selective membranes and electret films that utilize holes.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to examples.

Example 1 A 50:50 (weight ratio) blend of ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460) (MFR: 0.037g / 10mi
n) was subjected to biaxially stretched film molding under the following conditions. The blended product was melted with a screw extruder of 30 mmφ and L / D = 25, and then a coat hanger type T- with a die width of 30 cm was used.
The sheet was cooled with an extrusion roll from a die (set temperature: 280 ° C.) to obtain a 200 μm-thick uniform sheet. Then, a 90 mm × 90 mm sample is cut out from the sheet, and a biaxial stretching machine (manufactured by Toyo Seiki Seisakusho) is used to stretch at a stretching temperature of 120
The film was biaxially stretched under various conditions at a temperature of ° C to obtain a biaxially stretched film having a uniform thickness. The stretched film was evaluated by the following methods.

The stretchability 4: No cutting, uniform stretching 3: uneven stretching, almost no 2: stretching unevenness, there somewhat 1: room temperature with stretching unevenness large tensile test Shimadzu IS-500 type tensile tester (23 ° C. ). The shape of the sample piece is JIS No. I damper, the distance between clamps is 80 mm, and the pulling speed is 20 mm.
/ Min. The initial elastic modulus was obtained from the initial gradient of the stress-strain curve obtained by the tensile test. Alternatively, the breaking strength was similarly obtained from the breaking stress of the stress-strain curve. The cross-sectional area of the test piece necessary for calculating the initial elastic modulus and the breaking strength was obtained by calculating the thickness of the test piece from the weight and the specific gravity. The specific gravity of the test piece was determined by the density gradient method. Impact strength film Impact tester (made by Toyo Seiki Seisakusho) 1
The measurement was performed using an impact head with a 2 "φ spherical surface. The results are shown in Table 1.

[0026]

Comparative Example 1 The blended product used in Example 1 was biaxially stretched film molded under the same conditions as in Example 1 except for the draw ratio to obtain a biaxially stretched film having a uniform thickness. It was The obtained results are shown in Table 2.

[0028]

Example 2 A 40:60 (weight ratio) blend (MFR :) of ultrahigh molecular weight polyethylene ([η] = 19.6 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460). 0.006g / 10mi
Example 1 was repeated except that n) was used. The results are shown in Table 3.

[0030]

Example 3 A 70:30 (weight ratio) blend (MFR :) of ultra-high molecular weight polypropylene ([η] = 8.02 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460). 0.19g / 10min)
Was formed into a film under the following conditions. The blend was melt-kneaded with a screw extruder (set temperature 220 ° C.) of 20 mmφ and L / D = 20, and then granulated. 90 mm x 90 mm x 300 by compression molding using the obtained pellets
A sheet of μ was obtained. Then, the sheet was biaxially stretched in the same manner as in Example 1 with a length of 5 times and a width of 5 times. The operating temperature at this time was 150 ° C., and a film having a uniform thickness could be obtained by simultaneous biaxial stretching. Table 4 shows the evaluation results of the stretched film.

[0032]

Comparative Example 2 Using a 50:50 (weight ratio) blend of ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460). In the same manner as in Example 1, 21
A 0 μ sheet was obtained. After this, the operating temperature is 120 ° C and the length is 4
A film having a uniform thickness was obtained by sequentially biaxially stretching the film twice and laterally four times. Table 5 shows the evaluation results of the biaxially stretched film.

[0034]

<Embodiment 4> Ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460) were used in the same manner as in Example 1.
Uniform sheets of 500μ were obtained using the 0:50 (weight ratio) blend. Then, the sheet is simultaneously biaxially stretched at a stretching temperature of 120 ° C. in the lengthwise and widthwise directions of 4, 5, 6, 7 and 7, respectively, and a sample is cut out from the stretched film and again subjected to a double stretching at the same temperature. Thus, a uniform biaxially stretched film having a high stretch ratio was obtained. Table 6 shows the evaluation results of the obtained biaxially stretched film.

[0036]

Comparative Example 3 A 50:50 blend of ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460) was used under the same conditions as in Example 1. Sheet molding was performed below.
Then, when a sample was cut out from the sheet and biaxial stretching was tried at room temperature, uneven stretching and breakage occurred, and uniform stretching could not be performed.

Comparative Example 4 Ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) was compression molded to 100 μm.
Got a sheet of. The operating condition at this time is 200 ° C. Then, biaxial stretching was tried using the sheet. Stretching was attempted at stretching temperatures of 60, 80, 100, and 120 ° C., but in each case, the tensile stress was large and uniform stretching of 2 times or more was impossible due to stretching unevenness and breakage.

Comparative Example 5 A 10:90 (weight ratio) blend of ultrahigh molecular weight polyethylene ([η] = 8.20 dl / g) and paraffin wax (melting point = 69 ° C., molecular weight = 460) (MFR: Attempts were made to form a sheet by the method described in Example 1 using 83 g / 10 min), but a sheet having a uniform thickness could not be formed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-89326 (JP, A) JP-A-57-177037 (JP, A) JP-A-57-177035 (JP, A) JP-A-56- 133134 (JP, A) JP-A-52-74682 (JP, A) JP-A-58-217322 (JP, A) JP-A-59-192534 (JP, A)

Claims (5)

[Claims] 1. At least an intrinsic viscosity [η] of 5.0 dl
/ G or more of ultra-high molecular weight polyolefin A, and the stretching ratio in the longitudinal direction after solidification is 3 times or more and the stretching ratio in the transverse direction is 3 times or more, and the breaking strength is 720 kg / c.
m ² or more (however, the stretching ratio in the longitudinal direction is 5 times or more, and the stretching ratio in the transverse direction is 5 times or more, and the initial elastic modulus is 7 or more.
300 kg / cm ² or more and breaking strength of 910 kg /
(excluding cm ² or more), a biaxially stretched ultra high molecular weight polyolefin film. 2. The ultrahigh molecular weight polyolefin A contains a hydrocarbon-based plasticizer B having a boiling point higher than the melting point of the ultrahigh molecular weight polyolefin, and has a melt flow rate of 0.005 to 50 g / 10 min. The biaxially stretched film described. 3. The ultrahigh molecular weight polyolefin is ultrahigh molecular weight polyethylene.
The biaxially stretched film according to item. 4. At least an intrinsic viscosity [η] of 5.0 dl
/ G or more of ultrahigh molecular weight polyolefin A and a hydrocarbon-based plasticizer B having a boiling point exceeding the melting point of the ultrahigh molecular weight polyolefin, and having a melt flow rate of 0.00
After extruding a mixture of 5 to 50 g / 10 min and once solidifying, the stretching ratio in the longitudinal direction is 3 times or more and the stretching ratio in the transverse direction is 3 times or more at a stretching temperature lower than the melting point of the ultra high molecular weight polyolefin. The stretching ratio in the machine direction is 5 times or more, and the stretching ratio in the transverse direction is 5 times or more,
Initial elastic modulus 7300kg / cm ² or more and breaking strength, characterized in that biaxially oriented excluding 910 kg / cm ² or more), ultrahigh molecular weight polyolefin biaxially stretched breaking strength is 720 kg / cm ² or more Film manufacturing method. 5. The method for producing a biaxially stretched film according to claim 4, wherein the ultra high molecular weight polyolefin is ultra high molecular weight polyethylene.