JPS59227420A - Biaxially stretched film made of ultra-high molecular weight polyolefine and preparation thereof - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented film, by extruding a mixture consisting of ultra-HIGH M.W. polyolefine and a specific hydrocarbonaceous plasticizer while biaxially stretching the extrudate at an stretching temp. lower than the m.p. of ultra-high M.W. polyolefine. CONSTITUTION:A mixture with melt flow of 0.005-50g/10min consisting of ultra-high M.W. polyolefine A having crytical viscosity eta of 5dl/g or more and a hydrocarbonaceous plasticizer B having a b.p. exceeding the m.p. of the ultra- high M.W. polyolefine A is extruded while the extrudate is biaxilly stretched to form a film. As the hydrocarbonaceous plasticizer B, one having a b.p. exceeding the m.p. A of the aforementioned ultra-high M.W. polyolefine A, pref., a hydrocarbonaceous one having a b.p. of the m.p. A+50 deg.C or more, the m.p. B of 40-120 deg.C and a M.W. of 2,000 or less is used. Stretching magnification in biaxial stretching is usually 3 times in a longitudinal direction, pref., 5-20 times and 3 times in a traverse direction, pref., about 5-20 times. When the stretching magnification is below 3 times, mechanical strength can not be developed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ultra-high molecular weight polyolefin biaxially oriented film and a method for producing the same.

Ultra-high molecular weight polyethylene, which is a typical example of ultra-high molecular weight polyolefin, has superior impact resistance, abrasion resistance, chemical resistance, tensile strength, etc. compared to general-purpose polyethylene, and its use as an engineering plastic is expanding. However, compared to general-purpose polyethylene, the melt viscosity is extremely high and the fluidity is poor, so it is extremely difficult to mold using conventional extrusion molding, and most of it is molded by compression molding, and some rods etc. Currently, it is extrusion molded.

In addition, as a method for producing ultra-high molecular weight polyolefin,
A method of producing a film by sintering ultra-high molecular weight polyethylene powder, heating it to a temperature higher than the melting point of polyethylene, heating it between two belts, pressing it, and cooling it (Japanese Patent Publication No. 11576/1983). Alternatively, a method of orienting a sintered ultra-high molecular weight polyethylene sheet with a pressure roll at a temperature range from above the secondary transition point to below the melting point (Japanese Patent Application Laid-open No. 53
-45376), but all of them involve sintering ultra-high molecular weight polyethylene powder to make a sheet, which takes a long time to form, and in the latter method, ultra-high molecular weight polyethylene has a low melt viscosity. Due to the high fluidity and poor fluidity, it was almost impossible to obtain thin films even when oriented with pressure rolls at temperatures below the melting point.

On the other hand, it is well known that high-strength, thin-walled films can be produced by biaxially stretching films, such as biaxially oriented polypropylene films (OPP films), but unlike ordinary polypropylene, ultra-high molecular weight polyolefins have high strength. It has been almost impossible to obtain a biaxially stretched film because the viscosity is extremely high in the temperature range where stretching is possible.

In view of this situation, the present inventors have conducted intensive studies on a method for obtaining a biaxially stretched film of ultra-high molecular weight polyolefin, and have found that by mixing a specific hydrocarbon plasticizer with ultra-high molecular weight polyolefin, biaxially stretched film can be obtained. It has now been found that a film can be obtained, leading to the present invention.

That is, in the present invention, the intrinsic viscosity [η] is at least 5 dl.
/g or more ultra-high molecular weight polyolefin (A) and a hydrocarbon plasticizer (B) having a boiling point exceeding the melting point of the ultra-high molecular weight polyolefin (A), the Mel I flow rate is 0.005 to 50. A method for producing a biaxially stretched film of an ultra-high molecular weight polyolefin, characterized in that a mixture of g/10 m1n is extruded and biaxially stretched at a stretching temperature lower than the melting point of the ultra-high molecular weight polyolefin (A), and the ultra-high molecular weight polyolefin (A) is The present invention provides a biaxially stretched film consisting of A) having a stretching ratio in the longitudinal direction of 3 times or more and a stretching ratio in the lateral direction of 3 times or more.

Ultra-high molecular weight polyolefin (A) used in the method of the present invention
The intrinsic viscosity [η] of the decalin solvent at 135°C is 5
d17g or more, preferably in the range of F to 30a/g. If [η] is less than 5/g, there is a risk that a high strength film, which is a characteristic of ultra-high molecular weight polyolefins, may not be obtained due to the low molecular weight.On the other hand, the upper limit of [η] is not particularly limited, but is 30 dl /g, the melt viscosity is high and the extrusion moldability is poor even if a hydrocarbon plasticizer (B) described below is added. Such ultra-high molecular weight polyolefins (
A) is a polyolefin with a much higher molecular weight among polyolefins obtained by polymerizing ethylene, propylene, l-butene, 4-methyl-1-pentene, 1-hexene, etc. by iW Ziegler polymerization. It is. Among them, ultra-high molecular weight polyethylene mainly composed of ethylene is preferred because it has excellent cold resistance, impact resistance, self-lubricating properties, and the like.

The hydrocarbon plasticizer (B) used in the method of the present invention has a boiling point that exceeds the melting point (A) of the ultra-high molecular weight polyolefin (A), and preferably has a boiling point that is higher than the melting point (A) +10°C.
It is a hydrocarbon plasticizer having a melting point (B) of 350° C. or less, more preferably a boiling point of 40 to 120° C., a melting point (B) of 40 to 120° C., and a molecular weight of 2,000 or less.

If the boiling point is lower than the melting point (A) of the ultra-high molecular weight polyolefin (A), the raw sheet mixed with the ultra-high molecular weight polyolefin (A) and melt-extruded will foam, so a good biaxially stretched film cannot be obtained. There is a possibility that there will be no. Also, if a small amount of liquid at room temperature is used, it will not impede extrusion moldability, but if a large amount is used, for example, when using a screw extruder, the screw and the mixture will rotate together, making steady extrusion molding impossible. Therefore, the melting point (B) is 40°C
The above hydrocarbon plasticizers are most preferred.

In addition, the molecular weight of the hydrocarbon plasticizer (B) is determined by mixing it with the ultra-high molecular weight polyolefin (A) so that the MFR of the mixture is 0.
．． 0.005 to 50 g/10 m1n, preferably 0.005 to 50 g/10 m1n.
There is no particular limitation as long as it is within the range of 0.01 to 50 g/min, more preferably 0.1 to log/min, but those with a molecular weight exceeding 2000,
In order to keep the VFR within the above range, a large amount must be added, and as a result, when formed into a film, there is a risk that the excellent properties inherent to ultra-high molecular weight polyolefins may not be exhibited. The VFR in the present invention is based on ASTM D
123B, but polypropylene was treated under Condition L, poly-4-methyl-1-pentene was treated under Condition T, and other polyolefins including polyethylene were treated under Condition E.

The hydrocarbon plasticizer (B) used in the present invention includes:
Specifically, n-alkanes such as n-decane, n-dodecane, docozan, tricosane, and tetracosane, liquid paraffin, kerosene, paraffin wax, α-olefin oligomers such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutene, etc. aliphatic hydrocarbon compounds, naphthalene, tetralin, diethylbenzene,
Decalin, aromatic hydrocarbon compounds such as low molecular weight polystyrene or their hydrogenated derivatives, C5 petroleum resins or their halides, capric acid, lauric acid, valmitic acid, stearic acid, behenic acid, oleic acid, erucic acid higher fatty acids such as caprylic alcohol, lauryl alcohol, palmityl alcohol, stearyl alcohol, higher fatty acid amides such as palmitic acid amide, stearic acid amide, oleic acid amide, calcium stearate, calcium laurate, zinc stearate and higher fatty acid esters such as stearic acid monoglyceride, oleic acid monoglyceride, and stearic acid diglyceride.

When ultra-high molecular weight polyethylene is selected as the ultra-high molecular weight polyolefin (A), paraffin wax is preferable as the hydrocarbon plasticizer (B) from the viewpoint of compatibility.

The paraffin waxes are mainly composed of saturated aliphatic hydrocarbon compounds, specifically those having 2 carbon atoms such as docosa/, tricosane, tetracosane, and triacontane.
Mixtures of two or more n-alkanes or lower n-alkanes based on them, so-called paraffin wax separated and refined from petroleum, low molecular weight obtained by copolymerizing ethylene or ethylene and other α-olefins. Waxes whose molecular weight has been lowered by thermal degradation of polyethylene such as medium/low pressure polyethylene wax, high pressure polyethylene wax, ethylene copolymer wax, medium/low pressure polyethylene, high pressure polyethylene, etc., which are polymers, and their waxes. Examples include oxidized waxes such as oxides or maleic acid-modified waxes, and maleic acid-modified waxes.

The melting point in the present invention is a value measured using a differential scanning calorimeter (D SC) according to ASTM D 3417. The molecular weight is a weight average molecule of 9J (Flw) measured by GPC method (gel permeation chromatography) under the following conditions.

Equipment: Waters Co., Ltd. 150c type column: Toyo Soda Kogyo@ TSK GMH-6 (6
mmφX600 mm> Solvent 20-dichlorobenzene (ODCB) Temperature: 13
5°C Flow rate: 1. Oml/min Injection concentration: 30 mg/20ml OD CB (
Injection volume: 400 μβ) The column elution volume was calibrated by the universal method using standard polystyrene manufactured by Toyo Soda Kogyo and Pressure Chemical.

The method of the present invention comprises the ultra-high molecular weight polyolefin (A)
The hydrocarbon plasticizer (B) is added and mixed to give an MFR of 0.005 to 50 g/10 m1n, preferably 0.
．． 01 to 50g/10mln, more preferably 0
．． 1 to Log/10 m1n is extruded from a die after melt-kneading, and biaxially stretched at a temperature below the melting point of the ultra-high molecular weight polyolefin (A).
This is a method for producing an ultra-high molecular weight polyolefin biaxially stretched film.

In the method of the present invention, the amount of the ultra-high molecular weight polyolefin (A) is not particularly limited as long as the MFR of the mixture of the ultra-high molecular weight polyolefin (A) and the hydrocarbon plasticizer (B) is within the above range. The amount of ultra-high molecular weight polyolefin (A) is usually 15 to 80% by weight, preferably 30 to 70% by weight (representing 100% by weight of the mixture). The amount of ultra-high molecular weight polyolefin (A) is 15% by weight
If the amount is less than that, the amount of the hydrocarbon plasticizer (B) is too large, and the extensibility of the extruded raw sheet may be impaired. On the other hand, if the amount of the ultra-high molecular weight polyolefin (A) exceeds 80% by weight, the MFR will not exceed 0.005 even if the hydrocarbon plasticizer (B) is added, making melt extrusion difficult. However, the surface of the extruded original film is severely roughened, and a large amount of stress is required during biaxial stretching, resulting in poor stretchability.

Ultra-high molecular weight polyolefin (A) and hydrocarbon plasticizer (
B) can be melt-kneaded using, for example, a Henschel mixer, ■-
After mixing in a blender, ribbon blender, tumbler blender, etc., the mixture is mixed in a screw extruder such as a -screw extruder or twin-screw extruder, a kneader, a Banbury mixer, etc., usually from above the melting point to 350°C, preferably from above the melting point +50°C to above. It can be carried out at a temperature of 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 gouey while being melt-kneaded using a screw extruder or the like.

The extrusion temperature is usually 150 to 350°C, preferably 19°C.
It can be carried out at temperatures from 0 to 300°C. Extrusion temperature is 150
Below 350°C, the melt viscosity is high and extrudability is poor;
If it exceeds this amount, there is a risk that the molecular weight of the ultra-high molecular weight polyolefin will decrease due to thermal deterioration.

The film extruded by the above method is biaxially stretched at a temperature below the melting point (A) of the ultra-high molecular weight polyolefin (A), preferably at a temperature from below the melting point (A) to 60° C. or above. When the stretching temperature is higher than the melting point (A), the orientation by stretching is insufficient and mechanical strength cannot be exhibited. Moreover, if the stretching temperature is 60° C. or lower, a large amount of stress is required for stretching, which is not preferable.

The method for biaxially stretching the extruded raw film is the simultaneous biaxial stretching method using the blown film method, the simultaneous biaxial stretching method using the tenter method, or stretching in the longitudinal direction with a roll etc. and then stretching in the transverse direction with a tenter. A sequential biaxial stretching method may be mentioned. The stretching temperature during biaxial stretching is lower than the melting point (A) and ultra-high molecular weight polyolefin (
Biaxial stretching is possible using any method as long as the temperature range is above the temperature at which the yield point stress disappears in the tensile test of A), but when stretching is carried out at a temperature below the temperature at which the yield point stress disappears, sequential stretching is possible. Since the stretching method causes longitudinal cracks in the film during transverse stretching, it is preferable to employ a simultaneous biaxial stretching method.

When biaxially stretching the extruded film, the molten film extruded from the goose is cooled to within the above temperature range, or the film is once solidified and then heated again to within the above temperature range. However, the latter method is preferred because the temperature range can be easily controlled. In addition, the stretching ratio during two-wheel stretching is usually 3 times or more in the longitudinal direction, preferably 5 times or more.
The magnification is from 20 times to 3 times, preferably 3 times or more in the lateral direction, preferably about 5 to 20 times. If the stretching ratio is less than 3 times, mechanical strength cannot be developed by stretching. If the stretching ratio exceeds 20 times, the stretching operation may be difficult because the thickness of the biaxially stretched ultra-high molecular weight polyolefin film formed by stretching will be 1/400th or less of the original film.

Further, if the stretching temperature is higher than the temperature at which the yield point stress disappears, it is possible to stretch at a low magnification, but if the stretching temperature is lower than that temperature, the stretching is limited to 3 times or more. In addition to the hydrocarbon plasticizer (B), the ultra-high molecular weight polyolefin (A) used in the present invention contains heat stabilizers, weather stabilizers, lubricants, anti-blocking agents, slip agents, pigments, dyes, and inorganic fillers. Various additives that are normally added to polyolefins, such as additives, may be blended within the range that does not impair the purpose of the present invention.

The thickness of the ultra-high molecular weight polyolefin biaxially stretched film of the present invention can be appropriately selected depending on the application, but is usually in the range of 50 to 0.5μ, preferably 20 to 2μ.

In addition, the film may be used alone, or it may be used by subjecting one or both sides to corona discharge treatment, anchoring treatment as necessary, and laminating it with other resins, paper, cellophane, or aluminum foil. Good too.

The ultra-high molecular weight polyolefin biaxially stretched film of the present invention has high tensile strength, high impact strength, and high elasticity that cannot be obtained with conventional ordinary polyolefin films, so it can be used in the field of polyolefin films such as packaging materials. It can be used in the field of high elasticity and high strength films, and can also be used as a reinforcing material by combining with various materials. Furthermore, since it is possible to make ultra-thin films through high stretching, capacitor films,
Can also be used for insulating paper.

In addition, since the ultra-high molecular weight polyolefin film of the present invention has the hydrocarbon plasticizer (B) uniformly dispersed, it can be produced as a by-product by extraction with n-hegyusan, n-hebutane, etc. It is also highly suitable for functional materials such as selective membranes and electret films that utilize micropores.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) and paraffin wax (melting point = 69°C, molecular weight = 4
A 50:50' (weight ratio) blend (MFR: 0.037 g/10 n+in) with 60) was subjected to biaxially stretched film forming under the following conditions. The blend was melted in a screw extruder with a diameter of 30 mm and L/D = 25, and then the sheet was extruded from a coat hanger type T-gui (set temperature: 280°C) with a width of 30 cm and cooled with an extrusion roll to form a uniform sheet with a thickness of 200 μ. I got it. Next, a 90 mm x 90 mm sample was cut out from the sheet and stretched at a stretching temperature of 120 mm using a biaxial stretching machine (newly manufactured by Toyo Seiki Seisakusho).
Biaxially stretched films with uniform thickness were obtained by biaxially stretching at various magnifications at ℃. The stretched film was evaluated by the following method.

Stretchability 4: No cutting, uniform stretching 3: Stretching unevenness, almost none 2: Stretching unevenness, slightly present 1: Stretching unevenness Large tensile test At room temperature (
23°C). The sample piece shape was a JIS No. 1 dumbbell, the distance between the clamps was 80 mm, and the tensile speed was 20 m+n/
It was set to min.

1 with impact strength film impact tester (Toyo Seiki Seisakusho M)
The measurement was performed using a spherical impact head of /2"φ.

Example 2 Ultra-high molecular weight polyethylene ([η) -19,6 dl/g
) and paraffin wax (melting point = 69°C, molecular weight -46
0) in a 40:60 (weight ratio) blend (M F R
Example 3 Ultra-high molecular weight polypropylene ((η) = 8.02 dl/
g) and paraffin wax (melting point = 69°C, molecular weight = 4
60) and a 70:30 (weight ratio) blend (M F
R: 0.19g/10m1n) was formed into a film under the following conditions. The blend has a diameter of 20 mm,
L/D=20 screw extruder (set temperature 220°C)
After melt-kneading, granulation was performed. Compression molding is performed using the obtained pellets to form 90mm x 90mm x 300mm.
A sheet of μ was obtained. The sheet was then biaxially stretched 5 times in length and 5 times in width in the same manner as in Example 1. The operating temperature at this time was 150°C, and simultaneous biaxial stretching made it possible to obtain a film with uniform thickness.

Example 4 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) and paraffin wax (melting point -69℃, molecular weight -46
A 210μ sheet was obtained in the same manner as in Example 1 using a 50:50 (weight ratio) blend of 0) and 0). Thereafter, successive biaxial stretching was carried out at an operating temperature of 120° C. by 4 times in length and 4 times in width to obtain a film with a uniform thickness. The evaluation results of the biaxially stretched film are shown in Table 4. Example 5 Ultra-high molecular weight polyethylene ([η) =
8.20d1/g) and paraffin wax (melting point =
A uniform sheet of 500μ was obtained using a 50:50 (weight ratio) blend of 69°C, molecular weight = 460). Next, the sheet is simultaneously biaxially stretched 4.5 and 6.7 times in length and width at a stretching temperature of 120°C, and a sample is cut out from the stretched film and simultaneously biaxially stretched twice at the same temperature. As a result, a uniform biaxially stretched film with a high stretching ratio was obtained.

The evaluation results of the obtained biaxially stretched film are shown in Table 5. Comparative Example 1 Ultra-high molecular weight polyethylene ([l) = 8.20〃/g)
and paraffin wax (melting point = 69°C, molecular weight = 460
) was formed into a sheet under the same conditions as in Example 1. Next, after cutting a sample from the sheet, biaxial stretching was attempted at room temperature, but uneven stretching and breakage occurred, and uniform stretching could not be performed.

Comparative example 2 Ultra high molecular weight polyethylene ([η) -8,20 dl/g
) was compression molded to obtain a 100μ sheet.

The operating conditions at this time were 200°C. Next, biaxial stretching was attempted using the sheet. Stretching temperature 60.80°10
Stretching was attempted at 0 and 120°C, but in both cases, the tensile stress was large, resulting in uneven stretching and breakage. Comparative Example 3 Ultra-high molecular weight polyethylene ([η) = 8.20 dl/g
) Paraffin wax (melting point = 69°C, molecular weight = 460
) and a 10:90 (weight ratio) blend (MF Rr
Although an attempt was made to form a sheet using the method described in Example 1 using 83g/10mfn, it was not possible to form a sheet with a uniform thickness.

Applicant: Mitsui Petrochemical Industries, Ltd. Agent Kazu Yamaguchi

Claims (5)

[Claims] (1) Ultra-high molecular weight polyolefin (A) having an intrinsic viscosity [η] of at least 5 dl/g or more, and characterized by having a stretching ratio in the longitudinal direction of 3 times or more and a stretching ratio in the lateral direction of 3 times or more. Ultra-high molecular weight polyolefin biaxially stretched film. (2) The ultra-high molecular weight polyolefin (A) contains a hydrocarbon plasticizer (B) having a boiling point exceeding the melting point of the ultra-high molecular weight polyolefin (A), and has a melt flow rate of 0.005 to 50 g/10 m1n. Claim (biaxially stretched film according to claim 11). (3) Claims (1) or 2, wherein the ultra-high molecular weight polyolefin (A) is ultra-high molecular weight polyethylene.
) The biaxially stretched film described in item 2. (4) At least the intrinsic viscosity [η] is 5 dl/
A mixture having a melt flow rate of 0.005 to 50 g/10 m1n, consisting of an ultra-high molecular weight polyolefin (A) having a weight of 100 g or more and a hydrocarbon plasticizer (B) having a boiling point exceeding the melting point of the ultra-high molecular weight polyolefin (A). A method for producing an ultra-high molecular weight polyolefin biaxially oriented film, which comprises extruding and biaxially stretching at a stretching temperature below the melting point of the ultra-high molecular weight polyolefin (A'). (5) The manufacturing method according to claim (4), wherein the ultra-high molecular weight polyolefin is ultra-high molecular weight polyethylene.