JPS6357645A - Production of ultra-high molecular weight polyolefin mixture - Google Patents

Abstract

PURPOSE:To produce the title mixture having excellent extrudability, storage stability and flow characteristics in powdery form, by mixing an ultra-high molecular weight polyolefin with a specified fluidity improver under specified conditions. CONSTITUTION:95-10wt% ultra-high molecular weight polyolefin powder (A) having an intrinsic viscosity of not lower than 5dl/g (in decalin at 135 deg.C) and a particle size of 1-300mum (e.g., PE) is mixed with 5-90wt% granule of a fluidity improver (B) which is solid at room temp. and has an m.p. lower than that of the component A (e.g., docosane) at a temp. within the range defined by the formula, wherein DELTAHa is the quantity of heat of fusion (cal/g) in the temp. range of the fusion-intiating temp. of the component B to the upper limit of the mixing temp.; and DELTAHf is the total quantity of heat of fusion (cal/g) in the range of the fusion-intiating temp. of the component B to the fusion- terminating temp.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an ultra-high molecular weight polyolefin mixture with excellent extrudability. More specifically, an ultra-high molecular weight polyolefin with excellent extrusion moldability, storage stability, and powder fluidity suitable for obtaining a drawn ultra-high molecular weight polyolefin product having a high modulus of elasticity and high tensile strength, and a flow improver for solids at room temperature. It relates to a method for producing a mixture consisting of.

[Conventional technology]

Molding ultra-high molecular weight polyolefin into fibers, tapes, etc.
It is already known that a molecularly oriented molded product having a high elastic modulus and high tensile strength can be obtained by stretching this material. It is described that the resulting filament is drawn.

However, since polyolefins with large molecular weights are extremely @M soluble in solvents, it is difficult to obtain a highly concentrated homogeneous solution, which is why the general description in the publication states that a solution of 1 to 50% by weight should be used. However, it is clear from the fact that the example only discloses a method using a solution with a low concentration of about 8% by weight at most, and 3% by weight for those with a molecular weight of 1 million or more. In practical application of this method, there are problems such as processing of a large amount of solvent and productivity, so there is a desire to develop a spinning technique from a highly concentrated solution of ultra-high molecular weight polyolefin.

As a method for producing a homogeneous solution of an ultra-high molecular weight polyolefin, a room temperature liquid solvent and an ultra-high molecular weight polyolefin are mixed and stirred at a temperature below the dissolution temperature of the ultra-high molecular weight polyolefin to form a suspension, and then the ultra-high molecular weight polyolefin is mixed and stirred. A method of supplying the material to an extruder maintained at a melting temperature to make it uniform (JP-A-61-73743, JP-A-61-89232)
No. 1 public axis) has been proposed.

However, in methods using a solvent that is liquid at room temperature, such as this method, if stirring is stopped when the solvent and ultra-high molecular weight polyolefin are mixed, the ultra-high molecular weight polyolefin will precipitate, resulting in a non-uniform suspension, so stirring is required at all times. There is a need,
It is difficult to store the suspension as a suspension in advance.Also, when trying to knead and extrude a suspension containing a solvent with a single screw extruder, the suspension and screw may rotate together, and the screw may rotate inside the extruder. There is a risk that the solvent and the ultra-high molecular weight polyolefin will partially separate and a homogeneous solution will not be obtained.In fact, JP-A-61-8
All of the examples described in Publication No. 9232 are examples using a two-wheel screw extruder, and it is stated in Comparative Example C that when a normal single-screw extruder is used, the filament is non-uniform and the drawability is poor. There is.

On the other hand, a method using a fluidity improver that is solid at room temperature such as paraffin wax as a fluidity improver for ultra-high molecular weight polyolefin (JP-A-59-130313, JP-A-6
0-197752, etc.) have been proposed. It has also been found that by employing this method, a molded article can be produced using a single-screw extruder commonly used for extrusion molding.

However, even if such a method is used, the ultra-high molecular weight polyolefin may not be sufficiently dispersed when using a single-screw extruder depending on the pretreatment conditions when mixing the ultra-high molecular weight polyolefin and the fluidity improver that is solid at room temperature. It has been found. In other words, simply mixing the ultra-high molecular weight polyolefin and the fluidity improver that is solid at room temperature in a solid state using a Henschel mixer or the like may not achieve a sufficiently uniform melt-mixing using a single-screw extruder; 1986
In the method described in Japanese Patent No. 197752, in which a powder mixture of an ultra-high molecular weight polyolefin and a fluidity improver is left at a temperature higher than the melting point of the ultra-high molecular weight polyolefin, the ultra-high molecular weight polyolefin melts and the mixture Since the viscosity of the mixture becomes extremely high, it is necessary to uniformly melt-knead it using a melt-kneader such as a Banbury mixer before feeding it to an extruder, as described in the publication. Furthermore, when a mixture that has been melt-kneaded is solidified, a slight phase separation occurs, and the solidified blend exhibits poor drawability even if it is melted again, probably due to the entanglement of the molecules of the ultra-high molecular weight polyolefin. Therefore, it is necessary to immediately supply the melt-kneaded mixture to an extruder or the like, and it is difficult to store it in advance as a premix.

[Problem that the invention seeks to solve]

In view of this situation, the present inventors developed a method for extrusion moldability, storage stability, and powder fluidity consisting of an ultra-high molecular weight polyolefin powder and a fluidity improver that is solid at room temperature and has a melting point lower than the melting point of the ultra-high molecular weight polyolefin. Get an excellent mixture (
As a result of various studies, we have arrived at the present invention.

[Means for solving problems]

That is, the present invention comprises a powder of an ultra-high molecular weight polyolefin (A) having an intrinsic viscosity [η] of 5 d1/g or more, and a fluidity improver (B) that is solid at room temperature and has a melting point lower than that of the ultra-high molecular weight polyolefin (A).
) granules and the following formula 0 formula % where ΔHa is the heat of fusion (cal/g) in the temperature range from the melting start temperature of the fluidity improver (B) to the upper limit of the mixing temperature
and Δllf is the total heat of fusion (cal/g) from the melting start temperature to the melting end temperature of the fluidity improver (B).

The present invention provides a method for producing an ultra-high molecular weight polyolefin mixture having excellent extrusion moldability, storage stability, powder fluidity, workability, etc., which is characterized by mixing at a temperature range that satisfies the following.

[For production]

The ultra-high molecular weight polyolefin (A) used in the present invention has an intrinsic viscosity [η] of 5 dl measured at 135°C in a decalin solvent.
/g or more, preferably 7 to 30 a/g.

If the intrinsic viscosity [η] is less than 5 dl/g, a homogeneous mixture can be easily prepared, but because the molecular chain is short, it tends to be difficult to achieve high elastic modulus and high strength properties. The upper limit of the intrinsic viscosity [η] is not particularly limited, but if it exceeds 30 a/g, the melt viscosity is too high even when the fluidity improver (B) is added, and extrusion moldability tends to be poor.

Examples of ultrahigh molecular weight polyolefins in the present invention include ethylene, propylene, 1-butene, 1-pentene, l-
hexene, 1-octene, 1-decene, 4-methyl-1
- Homopolymers or copolymers of α-olefins such as pentene. Among these, ethylene homopolymers or ethylene-based copolymers of ethylene and other α-olefins with high crystallinity are preferred since they can achieve high modulus of elasticity and high tensile strength.

The ultra-high molecular weight polyolefin (A) used in the present invention is a powder, and the particle size is usually 1 to 300 μm, preferably 5 to 2 μm.
It is in the range of 00 μm. If the particle size exceeds 300 μm, it may be too large to be attached to the surface of the granules of the fluidity improver (B) described below. On the other hand, if the diameter is less than 1 μm, the components (A) tend to aggregate violently, making uniform dispersion difficult.

The fluidity improver (B) used in the present invention is a low molecular weight compound that is solid at room temperature and has excellent dispersibility with ultra high molecular weight polyolefins whose melting point is lower than the melting point of ultra high molecular weight polyolefins, and is preferably an aliphatic compound. It is a hydrocarbon compound or its derivative. The aliphatic hydrocarbon compounds are mainly saturated aliphatic hydrocarbon compounds, specifically n-alkanes having 22 or more carbon atoms such as tocosan, tricosane, tetracosane, triacontane, etc., or n-alkanes containing these as main components. A mixture with lower n-alkanes, so-called paraffin wax separated and purified from petroleum, medium/low pressure polyethylene wax which is a low molecular weight polymer obtained by copolymerizing ethylene or ethylene with other α-olefins,
High-pressure polyethylene wax, ethylene copolymer wax, medium/low-pressure polyethylene, high-pressure polyethylene, and other waxes whose molecular weight has been lowered by thermal degradation, and oxidized waxes such as oxides of these waxes or maleic acid modified products. , maleic acid-modified wax, and the like.

Further, as the aliphatic hydrocarbon compound derivative, for example, one or more, preferably 1 to 2, at the end or inside of an aliphatic hydrocarbon group (alkyl group, alkenyl group),
Particularly preferred are compounds having one functional group such as carboxyl group, hydroxyl group, carbamoyl group, ester group, meltcapto group, carbonyl group, etc. with a carbon number of 10 or more, preferably a carbon number of 12 to 50, or a molecular weight of 150 to 2,000.
Preferably, 170 to 800 fatty acids, aliphatic alcohols, fatty acid amides, fatty acid esters, aliphatic mercaptans, aliphatic aldehydes, aliphatic ketones, etc. can be mentioned.

Specifically, the fatty acids include capric acid, lauric acid, myristic acid, balmitic acid, stearic acid, and oleic acid; the fatty alcohols include myristyl alcohol, cetyl alcohol, and stearyl alcohol; and the fatty acid amides include caprinamide, lauric amide, and palmitinamide. Examples of stearylamide and fatty acid esters include stearyl acetate and the like.

The fluidity improver (B) used in the present invention is preferably the aliphatic hydrocarbon compound or its derivative, and among them, it is not a single compound but a multi-component system such as paraffin wax, polyethylene wax, and industrial squarine containing balmitic acid. It is preferable because the compound has a wide melting temperature range and the temperature can be easily controlled when mixing the powder of the ultra-high molecular weight polyolefin (A) and the granules of the fluidity improver (B).

Incidentally, such aliphatic hydrocarbon compound or derivative thereof may be added with a low softening point hydrocarbon polymer having a softening point of 50 to 120°C, specifically, a tackifying resin usually used as a tackifying resin, within a range that does not impair the purpose of the present invention. It is used in the fields of tapes, paints, and hot melt adhesives, and depending on the monomer source to be polymerized, the following resins, such as C# fraction and C2 fraction obtained by decomposing petroleum, naphtha, etc. , a mixture of these or any fraction thereof, for example, a C9 fraction obtained by decomposing an aliphatic hydrocarbon resin, petroleum, naphtha, etc. whose main raw materials are isoprene and 1,3-pentadiene in the C1 fraction. An aromatic hydrocarbon resin whose main raw materials are styrene R11 and indenes, C4.
Aliphatic copolymerization of any C3 fraction and C9 fraction
Aromatic copolymerized hydrocarbon resin, alicyclic hydrocarbon resin obtained by hydrogenating aromatic hydrocarbon resin, synthetic terpene hydrocarbon resin with a structure containing aliphatic, alicyclic and aromatic groups, in turpentine oil terpene-based hydrocarbon resins made from α,β-pinene of It may also be a mixed fluidity improver added.

The fluidity improver (B) used in the present invention is a granule, and the particle size is usually 0.2 to 5III111, preferably 0.3 to 2r.
in the am range. Those exceeding 5III11 (A
) will be difficult to adhere uniformly, and there is a risk that the mixing ratio of components (A) and (B) will be uneven.

The mixing ratio of the powder of the ultra-high molecular weight polyolefin (^) and the granules of the fluidity improver (B) is usually 95 to 10% by weight of the powder of the ultra-high molecular weight polyolefin (A), preferably 90 to 30% by weight, In other words, the fluidity improver (B
) granules ranges from 5 to 90% by weight, preferably from 10 to 70% by weight. The amount of fluidity improver (B) is 5
If it is less than % by weight, the amount of (B) is too small relative to the amount of (A) deposited, so (A) tends to aggregate and the granulation effect tends to be small, and the melt viscosity of the mixture is also high, making it difficult to extrude. I am in the early stages of having difficulty with sex. - On the other hand, the fluidity improver (B) was 90%
If it exceeds % by weight, the fluidity improver (B) will strongly adhere to each other, resulting in a powder with an overall non-uniform composition, and the powder itself may be block-like and have poor fluidity.

In the method of the present invention, the powder of the ultra-high molecular weight polyolefin (A) and the granules of the fluidity improver (B) are mixed with the following formula 0 formula % (1
) Particularly preferably, the following formula 0.003≦ΔHa/Δllf≦0, 012 (
2) In the formula, △Ha is the heat of fusion (cal) in the temperature range from the melting start temperature of the fluidity improver (B) to the upper limit of the mixing temperature.
/g), and Δ)If is the total heat of fusion (cat/g) from the melting start temperature to the melting end temperature of the fluidity improver (B).
)' is.

This method involves mixing within a temperature range that satisfies the following.

When the mixing temperature ΔHa/Δ)If is less than 0.001, the powder of the ultra-high molecular weight polyolefin (A) does not adhere to the surface of the fluidity improver (B) granules, while when it exceeds 0.018, the powder of the ultra-high molecular weight polyolefin (A) does not adhere to the surface of the granules of the fluidity improver (B). The granules of the property improver (B) stick together and form blocks, resulting in poor powder fluidity.

The heat of fusion of the fluidity improver (B) was measured using a differential scanning calorimeter as follows. Differential scanning calorimeter is DSCn
A mold (manufactured by PerkinElmer) was used.

After enclosing approximately 5 smg of sample, cool to -30℃ and heat to -3
1) It was left at ℃ for 15 minutes. Thereafter, measurements were carried out from -30°C to 150°C at a temperature increase rate of 10°C/n+in. Calculations were made using a straight line obtained by directly extrapolating the specific heat curve of the obtained fluidity improver (B) in a completely molten state to the low temperature side as a baseline.

A Henschel mixer, a helical ribbon mixer, a rotary mixer, etc. may be used to mix the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B) granules.

When mixing the powder of ultra-high molecular weight polyolefin (^) and the granules of fluidity improver (B), additives that are usually added to polyolefin, such as heat stabilizers, weather stabilizers, pigments, dyes, and inorganic fillers, are added. It may be added within a range that does not impair the purpose of the invention.

[Effects of the Invention] The ultra-high molecular weight polyolefin mixture obtained by the method of the present invention has excellent extrusion moldability, storage stability, and powder fluidity, and moreover, the ultra-high molecular weight polyolefin has been adhered to the surface of the flowability modifier in advance. Since it is a mixture of solids dispersed at room temperature, it can be easily made into homogeneous filaments, sheets, films, etc. using a normal extruder, i.e. a single screw extruder.
Molded products such as pipes, rods, tapes, etc. can be melt-extruded. Although the mixture obtained by the method of the present invention can be molded into a sufficiently homogeneous molded product using a single-screw extruder, molding using other extrusion molding machines such as a multi-screw extruder is not excluded.

Melt extruded filaments, sheets, films,
Pipes, tapes, etc. have excellent stretchability because the fluidity improver (B) is homogeneously dispersed in the ultra-high molecular weight polyolefin (A), and can be stretched at a temperature below the melting point of the ultra-high molecular weight polyolefin (A). By molding and removing the fluidity improver from the molded product before, during or after stretching, it is possible to easily produce a stretched ultra-high molecular weight polyolefin product having a high modulus of elasticity and high tensile strength.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way unless the gist of the invention is exceeded.

Example 1 Ultra-high molecular weight polyethylene powder ((
η) = 7.5dl/g) 10kg and average particle size 2m
10 kg of paraffin-AX (molecular weight 500, manufactured by Nippon Kiiro Co., Ltd.) and a Henschel mixer (with a volume of 1201 mm)
(manufactured by Mitsui Miike Kakoki) without draining the jacket water.
Mixed at 700 rpm. After 1.5 minutes, stirring was stopped and the powder inside was taken out and the average particle size was 2.5m.
A granular powder with good fluidity was obtained. Powder temperature at that point is 35℃, △Ha/△1lf=0.0
It was 11. The obtained powder is passed through an extruder with a hopper (
40φ made by Nippon Steel Corporation), it was easily bitten and the die pressure = 80kg/cjG was stable at 8.8 without any device to prevent hopper bridging.
It was possible to extrude with a kg/H1 variation rate of ±1.9%.

However, the powder temperature rose to 50°C, and a block-like material with poor fluidity was obtained, and ΔHa/Δl1f=
It was 0.05.

When the powder was put into an extruder equipped with a mechanical agitation device to prevent hopper bridging, it was difficult to eat the powder from the start, and after 5 minutes, the die pressure was 5 kg /
It became below aa G and became inoperable.

Example 2 Ultra-high molecular weight polypropylene powder with an average particle size of 100 μm (
[η) = 9.2dl/g) 8kg and average particle size 3
+wm paraffin WAX (molecular weight = 500, manufactured by Nihon Danro Co., Ltd.) (15 kg) was mixed in the same device as in Example 1 to obtain a granular powder with an average particle size of 3.51 and good fluidity. At that point, the powder temperature was 38° C. (manufactured by Nippon Steel Corporation), and it was possible to extrude stably at 70 kg/H (variation rate ±1.6%).

Claims (1)

[Claims] (1) Powder of ultra-high molecular weight polyolefin (A) with intrinsic viscosity [η] of 5 dl/g or more and granules of fluidity improver (B) that is solid at room temperature and has a melting point lower than the melting point of ultra-high molecular weight polyolefin (A). and the following formula 0.001≦△Ha/△Hf≦0.018 where △Ha is the heat of fusion (cal/g) in the temperature range from the melting start temperature of the fluidity improver (B) to the upper limit of the mixing temperature. ), and ΔHf is the total heat of fusion (cal/g) from the melting start temperature to the melting end temperature of the fluidity improver (B). A method for producing an ultra-high molecular weight polyolefin mixture, characterized by mixing at a temperature range that satisfies the following.