JPS6360708A - Manufacture of mixture of ultra-high-molecular-weight polyolefin - Google Patents

Abstract

PURPOSE:To obtain a mixture superior in extrucsion molding properties, storage stability and powder fluidity, by a method wherein powder of ultra-high-molecular-weight polyolefin whose intrinsic viscosity is a fixed value or higher and that of a fluid modifier which is a solid at the normal temperature and is lower than the fusion point of the ultra-high- molecular-weight polyolefin are mixed up with each other at a specific temperature range. CONSTITUTION:Powder of ultra-high-molecular-weight polyolefin whose intrinsic viscosity is 5dl/g or higher and that of a fluid modifier which is a solid at the normal temperature and is lower than the fusion point of the ultra-high-molecular-weight polyolefin are mixed up with each other at a specific temperature range satisfying an expression of 0.002<=DELTAHa/DELTAHf<=0.030. Provided that the DELTAHa is a melting quantity of heat falling within a temperature range extending from the starting temperature of melting of the fluidity modifier to the upper limit of a mixing temperature and the DELTAHf is the whole melting quantity of heat extending from the starting temperature of the melting of the fluidity modifier to a completion temperature of the melting. Then a mixture of the ultra-high-molecular-weight polyolefin superior in extrusion molding properties, storage stability, powder fluidity and workability is obtained. When the intrinsic viscosity of the ultra-high-molecular-weight polyolefin is less than 5dl/g, it is hard to attain the high modulus of elasticity and high- strength properties as a molecular chain is short and when the same exceeds 30dl/g, it is inferior in extrusion molding properties as melt viscosity is too high.

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 having 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, polyolefins with large molecular weights are extremely poorly soluble in solvents, making it difficult to obtain a highly concentrated homogeneous solution.
Although the general description in the publication states that a solution with a concentration of 1 to 50% by weight is used, in the examples, it is at most about 8% by weight, and for those with a molecular weight of 1 million or more, it is as high as 3%. (This is clear from the fact that only a method using a low-concentration solution is disclosed. This is because there are problems such as processing of a large amount of solvent and productivity in the practical application of this method. It is desired to develop a spinning technology from a highly concentrated solution of 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 (Japanese Patent Application Laid-Open No. 61-73743, Publication No. 61-89232)
No. 2) 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 it as a suspension in advance. Furthermore, when a suspension containing a solvent is kneaded and extruded using a single-screw extruder, the suspension and the screw rotate together, and the solvent and ultra-high molecular weight polyolefin are partially separated in the extruder, resulting in a non-uniform solution. There is a risk. In fact, Japanese Patent Application Publication No. 61-8
All of the examples described in Publication No. 9232 are examples using a twin-screw extruder, and it is noted in Comparative Example C that if a normal single-screw extruder is used, the filaments are non-uniform and the drawability is poor. ing.

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. That is, if the ultra-high molecular weight polyolefin and the fluidity improver, which are solid at room temperature, are simply mixed in a solid state with hot water in a Henschel mixer or the like, there is a risk that they will not be melted and mixed sufficiently uniformly in a single-screw extruder; Tokukai 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. As a result of various studies in order to obtain a mixture with excellent properties, the present invention was achieved.

[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 dI/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).
) powder 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 ΔIff is the total heat of fusion (cat/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 flowability, workability, etc., which is characterized by mixing in 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 is 30d! /g
If the melt viscosity exceeds 100%, the melt viscosity is too high even when the fluidity improver (B) is added, and extrusion moldability tends to be poor.

The ultra-high molecular weight polyolefin in the present invention includes, for example, ethylene, propylene, 1-butene, 1-pentene, 1-
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 because they exhibit high elastic modulus 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 pm, preferably 5 to 2 pm.
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 powder 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 aliphatic carbonized. It is a hydrogen 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. Mixtures 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 process Polyethylene wax, ethylene copolymer wax, medium- and low-pressure polyethylene, high-pressure polyethylene, and other waxes whose molecular weight has been lowered by heat degradation, oxides of these waxes, oxidized waxes such as maleic acid-modified products, and maleic waxes. Examples include acid-modified wax.

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, palmitic 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 it is easy to control the temperature when mixing the powder of the ultra-high molecular weight polyolefin (A) and the powder 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 C4 fraction, C6 fraction, obtained by decomposing petroleum, naphtha, etc. A mixture of these or any fraction thereof, such as an aliphatic hydrocarbon resin whose main raw materials are isoprene and 1,3-pentadiene in the C6 fraction, a C1 fraction obtained by cracking petroleum, naphtha, etc. Aromatic hydrocarbon resin whose main raw materials are styrene derivatives and indenes, C4/C
Aliphatic/aromatic copolymerized hydrocarbon resin obtained by copolymerizing any fraction of the 3 fractions with C1 fraction, alicyclic hydrocarbon resin obtained by hydrogenating aromatic hydrocarbon resin, aliphatic, alicyclic Synthetic terpene-based hydrocarbon resin with a structure containing groups and aromatics,
Terpene hydrocarbon resins made from α,β-pinene in turpentine oil, chromanindene hydrocarbon resins made from indene and styrene in coal tar naphtha, low molecular weight styrene resins, and rosin hydrocarbons. A mixed fluidity improver containing a resin or the like may also be used.

The fluidity improver (B) used in the present invention is a powder, and the particle size is usually 1 to less than 200 μm, preferably 5 to 100 μm.
within the range of If it is less than 1 μm, the powder itself becomes difficult to handle and becomes a bottleneck in operation, making it impossible to use it on an industrial scale.

The mixing ratio of the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B) powder is usually 95 to 10% by weight, preferably 90 to 30% by weight, In other words, the fluidity improver (B
) powder 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 granulation effect is small (there is a risk that it will not lead to improvement in the particle size of the ultra-high molecular weight polyolefin, and the melt viscosity of the mixture is also high, making extrusion moldability difficult.On the other hand, the fluidity improver If (B) exceeds 90% by weight, the adhesion of the fluidity improvers (B) to each other becomes severe, resulting in a powder with an overall non-uniform composition, and the powder itself becomes block-like and has poor fluidity. There is a risk.

In the method of the present invention, the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B) powder are mixed with the following formula 0 formula % (1
) Particularly preferably, the following formula 0, 003≦△Ha/△Iff≦0.025 +2
In formula 1, ΔHa is the heat of fusion (cat/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).

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

1) When the mixing temperature is lower than 1) a/△Hf is less than 0.002, the powder of ultra-high molecular weight polyolefin (8) and the powder of fluidity improver (B) do not stick to each other.
On the other hand, if the particle size exceeds 0.030, the particles stick together too much and become block-like, 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 osc
An n-type (manufactured by PerkinElmer) was used.

After sealing approximately 5 mmg of the sample, it was cooled to -30°C and heated to -3
It was left at 0°C for 15 minutes. Thereafter, measurements were carried out from -30°C to 150°C at a temperature increase rate of 10°C/min. 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. can be used to mix the powder of the ultra-high molecular weight polyolefin (8) and the powder of the fluidity improver (B).

When mixing the ultra-high molecular weight polyolefin (A) powder and the fluidity improver (B) powder, additives that are usually added to polyolefins such as heat stabilizers, weather stabilizers, pigments, dyes, and inorganic fillers are added. They may be added within a range that does not affect 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 flowability, and furthermore, the ultra-high molecular weight polyolefin mixture obtained by the method of the present invention has excellent extrusion moldability, storage stability, and powder flowability. It is a room-temperature solid mixture in which ultra-high molecular weight polyolefin is dispersed in associated granules, so it can be easily processed into homogeneous filaments, sheets, films, pipes, rods,
Molded products such as tapes 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, this does not exclude molding methods using other extrusion molding machines such as a multi-screw extruder.

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 (^). By 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 high elastic modulus 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 ((
77) = 7.5dl/g) 10kg and average particle size 6
10 kg of 0 μm paraffin-AX (molecule 1500, manufactured by Nippon Tanro Co., Ltd.) was placed in a Henschel mixer (manufactured by Mitsui Miike Kakoki) with a capacity of 1201, and mixed at 700 rpm without flowing jacket water. After 1.2 minutes, stirring was stopped and the powder inside was taken out and the average particle size was 5.
A granular powder of 8 mm with good fluidity was obtained. The powder temperature at that point was 36℃, △Ha/△Hf = 0
．． It was 012. When the obtained powder was passed through an extruder with a hopper (40φ Nippon Steel Corporation), it was easily engulfed without any device to prevent hopper bridging, and the die pressure was 70 kg/crA.
It was possible to extrude stably at 8.2 kg/H1 fluctuation rate of ±2% at G.

Comparative Example 1 When mixing was further continued in Example 1 and opened after 4.5 minutes, the powder temperature had risen to 48°C, and a block-like material with poor fluidity was obtained, and △Ha/△IIf= 0
．． It was 034.

When the powder was put into an extruder with a mechanical agitation device installed to prevent hopper bridging, it was difficult to eat the powder from the start, and after 3 minutes the die pressure was 5 kg/cf.
It became below flG and became inoperable.

Example 2 Ultra-high molecular weight polypropylene powder with an average particle size of 250 μm (
[η) = 9.2 dl/g) and 15 kg of paraffin wax (molecule 1 = 500, manufactured by Nippon Danro Co., Ltd.) with an average particle size of 60 μ were mixed in the same equipment as in Example 1, and the average particle size was 7. A granular powder with a diameter of .5 mm and good fluidity was obtained. The powder temperature at that point was 34℃, △1)a
/ΔHf=0.009.

Same as in Example 1, it was applied to an extrusion molding machine with a hopper (40φ manufactured by Nippon Steel Corporation) at 7.3 kg/H (1.7% above the fluctuation rate).
It was possible to extrude stably.

Claims (1)

[Claims] (1) A powder of an ultra-high molecular weight polyolefin (A) with an intrinsic viscosity [η] of 5 dl/g or more and a powder of a fluidity improver (B) that is solid at room temperature and has a melting point lower than the melting point of the ultra-high molecular weight polyolefin (A). and the following formula: 0.002≦ΔHa/ΔHf≦0.030 In the formula, 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. , 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 in a temperature range that satisfies the following.