JPH05230732A - Multistage stretching method and stretching apparatus for high molecular weight polyolefin - Google Patents

Abstract

(57) [Summary] [Purpose] When multi-stage drawing of high molecular weight polyolefin
Disclosed is a stretching method and a stretching device for eliminating stretching unevenness caused by a rotating roll, having less trouble such as stretching breakage, and obtaining a stable stretched product with a small installation area. [Structure] In a method in which a high-molecular-weight polyolefin is melt-kneaded, melt-molded, and then multi-stage stretched, the stretching is performed by arranging a plurality of stretching tanks in series between a payout roll and a winding roll, and A multistage stretching method for a high molecular weight polyolefin, which is characterized in that it is carried out by passing it through a stretching zone in which the temperature is successively raised by 2 ° C. or higher. As the heat source of the drawing tank, at least one selected from the group consisting of a heat medium, a heating plate, an oven, far infrared rays, and microwaves is used. A stretching device for a high molecular weight polyolefin having a stretching zone in which a plurality of stretching tanks are arranged in series between a feeding roll and a winding roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multistage stretching method for a high molecular weight polyolefin and a stretching apparatus. More specifically, it relates to a high molecular weight polyolefin having excellent stretching stability and easy setting of a stretching ratio. The present invention relates to a multi-stage stretching method and a stretching device therefor.

[0002]

2. Description of the Related Art Stretched products of high molecular weight polyolefins have particularly excellent mechanical strength and various physical properties. Utilizing these characteristics, they can be used as materials for threads, reinforcing fibers, strings, ropes, nets, nets, etc. It has been used conventionally. in this way,
As a method for producing a stretched product of a high-molecular-weight polyolefin having various properties, for example, JP-A-55-107506, JP-A-56-15408 or JP-A-5-58506.
As disclosed in JP-A-8-5228, there has been proposed a method of obtaining a high-strength fiber by making a high-molecular-weight polyolefin into a dilute solution having a concentration of about 2 to 10% by weight, and spinning and stretching. Further, JP-A-59-130313 and JP-A-60-1
98220, JP-A-60-240432,
As disclosed in Japanese Patent Application Laid-Open No. 61-8323,
Various methods have been proposed in which a material that is solid at room temperature and can form a homogeneous system with a high-molecular-weight polyolefin at high temperature is melt-extruded and then stretched. Further, as a method of using both a solvent and a substance capable of forming a homogeneous system with a high molecular weight polyolefin at a high temperature such as a solid at room temperature as described above, a method of melt extrusion and stretching is disclosed in JP-A-56-50516. The gazette is also known. Further, JP-A-63-41512 is known as a method of solid-phase extruding a high-molecular-weight polyolefin powder below the melting point and then stretching.

These high-strength oriented materials of high-molecular-weight polyolefin have a strength of about 3 to 5 times at the industrialized level as compared with conventional polyethylene monofilaments, and are known as conventional uses for general-purpose industrial fiber materials. In addition, it is expected to be applied under severe conditions / environments that could not be provided by conventional polyethylene monofilaments. The high-strength oriented material of this high-molecular-weight polyolefin is, for example, glass fiber or carbon fiber, boron fiber, aromatic polyamide fiber, because it is possible to reduce the weight than a molded article using high-performance fibers such as aromatic polyimide fiber,
Materials such as various tensile strength materials, moving ropes, fishing nets for trawls,
It is extremely useful as a molding material for UD laminates, SMC, BMC, etc., and is expected as a material that can be used for lightweight and high-strength composite materials such as automobile parts, boat and yacht structures, and electronic circuit boards. It

[0004]

As described above, when a high molecular weight polyolefin is stretched, the stretching is also carried out by a single-stage stretching method, but in order to obtain a stretched product having more excellent physical properties, it is usually a multi-stage having two or more stages. A stretching method is often adopted. By the way, when multi-stage stretching of a high-molecular-weight polyolefin is attempted, as the number of stretching rolls increases, uneven rotation occurs on each roll, and accurate stretching cannot be achieved. Moreover, in the case of multi-stage stretching, it is necessary to determine the stretching ratio for each stretching roll, which requires complicated process control in terms of operation.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for stably producing a stretched product having a desired draw ratio with simple equipment and operation, by eliminating uneven rotation due to a stretching roll.

[0006]

The present invention has been proposed in order to achieve the above object, and is a roll used for stretching when a stretched product of a high molecular weight polyolefin is stretched in multiple stages. Has an important technical feature in that only two rolls, a pay-out roll and a take-up roll, are used to perform the other stretching by using a stretching tank having a specific structure set to a specific temperature condition.

That is, according to the present invention, in a method in which a high molecular weight polyolefin is melt-kneaded, melt-molded and then multi-stage stretched, the stretching is performed by arranging a plurality of stretching tanks in series between a feeding roll and a winding roll. And a multistage stretching method for a high molecular weight polyolefin, which is characterized in that the temperature of each stretching tank is sequentially raised by 2 ° C. or more to pass through a stretching zone.

According to the present invention, the heat source of the drawing tank is at least one selected from the group consisting of a heat medium, a heating plate, an oven, far infrared rays, and microwaves, that is, each drawing tank. The heat source is not only one kind of heat source, but a multi-stage stretching method is provided which is configured by appropriately combining these.

[0009]

DETAILED DESCRIPTION OF THE INVENTION A preferred example of the stretching method and stretching apparatus of the present invention is shown in a process chart. In FIG. 1, 1 is a pay-out roll, 2 is a take-up roll, and a plurality of stretching tanks 3 are provided therebetween. (a), 3 (b), 3 (c) ... Are arranged. A heat source is set in each drawing tank, and in this example, the heat medium 6 is placed in the drawing tank. Further, a plurality of turn rolls 4 are provided in each drawing tank so as to guide the drawn material to pass through the inside of the drawing tank. The surface of the turn roll can be ceramic coated, mirror-finished, or satin finished, and each of them may be arranged in a free state or may be arranged as a fixed drive roll.

The material 5 to be stretched, which has been guided to the first stretching tank through the pay-out roll 1, advances in the stretching tank while being guided by the turn rolls, and at the same time ends the first stretching step, and then undergoes the second stretching through the nip roll 7. Guided to the tank. At this time, the temperature of the heat medium in the second drawing tank is 2 ° C. higher than the temperature of the heat medium in the first drawing tank.
It is important to set the temperature higher than the above, and further, the temperature of the heat medium in the third drawing tank, which is the next step, is 2 ° C. or more higher than the temperature of the heat medium in the second drawing tank. Will be set. When the number of drawing tanks is three or more, it goes without saying that the temperature in the latter drawing tank is similarly higher than that in the former drawing tank by 2 ° C. or higher.

In the example of the drawing method shown in FIG. 1, each drawing tank is provided with a heat exchanger 8 for recycling a heating medium. One or two or more heat exchangers are optionally provided in each tank to prevent the temperature of the heat medium in the drawing tank from lowering and to perform drawing at an accurate draw ratio.

In FIG. 2, which shows another example of the preferred embodiment of the stretching method of the present invention in a process chart, the delivery roll, the winding roll, the arrangement of the stretching tank, and the configuration of the turn roll are the same as those shown in FIG. However, the characteristic feature of this example is that the heating medium is supplied from below the end of the latter drawing tank and discharged from below the starting end of the same drawing tank. It is in. The heat medium discharged from the drawing tank at the latter stage is supplied from below the terminal end of the adjacent drawing tank at the preceding stage, and further discharged from below the starting end of the drawing tank at the same stage, and is similarly supplied to the drawing tank at the adjacent preceding stage.・ Repeat repeatedly.

According to this method, the heat medium once comes into contact with the temperature of the outside air via the conduit portion 9 connecting between the drawing tanks, so that the temperature of the heat medium in the drawing tank at the preceding stage is naturally. The temperature is lower than the temperature of the heat medium in the drawing tank at the latter stage, and the difference is 2
It is easy to configure above ℃, if the temperature difference is 2
If the temperature is not higher than 0 ° C, the temperature of each drawing tank can be set to the specific temperature condition by cooling the conduit portion 9 between the drawing tanks or adjusting the length. Become.

Incidentally, an example of the conventional stretching process is shown in FIG. In this example, the stretching bath and the stretching roll are alternately set between the payout roll and the winding roll. The stretching roll is formed by at least 5 rolls in one stage, and even in the case of the two-stage stretching, stretching is performed by at least 10 rolls. Therefore,
The greater the number of rolls, the greater the uneven rotation of the material to be stretched due to the rolls, the frequent breakage of stretching, and the difficulty in producing a stretched product at a stable stretch ratio.

In the present invention, before the multistage drawing,
A stretching method known per se can be applied, and the melt-formed product can be stretched to a predetermined ratio before being subjected to multi-stage stretching.

The high molecular weight polyolefin according to the present invention is
The intrinsic viscosity [η] measured in a decalin solvent at 135 ° C is
At least 5 dl / g, preferably 7 to 30 dl /
g of a polymer.

As the high molecular weight polyolefin, not only high molecular weight polyethylene and high molecular weight polypropylene but also ethylene having the above-mentioned intrinsic viscosity and an α-olefin having 3 or more carbon atoms, preferably 4 to 10 carbon atoms, for example, propylene, Examples thereof include butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1, decene-1, and copolymers with two or more species. Ethylene and butene
The copolymer with one or more α-olefins selected from the group consisting of 1,4-methylpentene-1, hexene-1, octene-1 and decene-1 has high strength. In addition, it has excellent wear resistance and creep resistance. Further, when the high molecular weight polyolefin is a copolymer of ethylene and α-olefin, α-
Olefin comonomer averages 0.1 per 1000 carbons
It is desirable to contain 20 to 20, preferably 0.5 to 10 on average.

The high molecular weight polyolefin of the present invention includes ethylene, propylene, or these olefins and the above α.
An olefin comonomer, the periodic table IVb, Vb,
VIb and VIII group transition metal compounds and I to
It can be obtained by slurry polymerization in the presence of a group III metal hydride or an organic metal catalyst, for example, in an organic solvent.

The high molecular weight polyolefin thus obtained can be blended with, for example, a diluent for enabling melt kneading, melt molding or stretching, or can be mixed with paraffin wax which is solid at room temperature.

As the diluent, a solvent for high molecular weight polyolefin or various waxes having dispersibility for high molecular weight polyolefin are used.

The solvent is preferably a solvent having a boiling point not lower than the melting point of the polymer, more preferably not lower than the melting point + 20 ° C.

Specific examples of such a solvent include n-nonane, n-decane, n-undecane, n-dodecane and n-
Aliphatic hydrocarbon solvents such as tetradecane, n-octadecane or liquid paraffin, kerosene, xylene, naphthalene, tetralin, butylbenzene, p-cymene, cyclohexylbenzene, diethylbenzene, benzylbenzene, dodecylbenzene, bicyclohexyl, decalin, methyl Aromatic hydrocarbon solvents such as naphthalene and ethylnaphthalene or hydrogenated derivatives thereof, 1,1,2,2-tetrachloroethane, pentachloroethane, hexachloroethane, 1,2,3-trichloropropane, dichlorobenzene, 1,2 Examples thereof include halogenated hydrocarbon solvents such as 1,4-trichlorobenzene and bromobenzene, and mineral oils such as paraffin-based process oil, naphthene-based process oil and aromatic-based process oil.

As the wax, an aliphatic hydrocarbon compound or its derivative is used.

The aliphatic hydrocarbon compound is mainly a saturated aliphatic hydrocarbon compound and usually has a molecular weight of 20.
It is a paraffinic wax of 00 or less, preferably 1000 or less, more preferably 800 or less. Specific examples of these aliphatic hydrocarbon compounds include n-alkanes having 22 or more carbon atoms such as docosane, tricosane, tetracosane, and triacontane, or mixtures with lower n-alkanes containing them as the main component, and separation and purification from petroleum. So-called paraffin wax, low molecular weight polymer obtained by copolymerizing ethylene or ethylene or other α-olefin, polyethylene wax for medium / low pressure method, polyethylene wax for high pressure method, ethylene copolymer wax or medium / low pressure method Examples thereof include waxes obtained by reducing the molecular weight of polyethylene such as polyethylene and high-pressure polyethylene by thermal degradation, oxides of these waxes, oxidized waxes such as maleic acid-modified waxes, and maleic acid-modified waxes.

The aliphatic hydrocarbon compound derivative may be, for example, one or more, preferably 1 or 2, and particularly preferably 1 at the terminal or inside of the aliphatic hydrocarbon group (alkyl group, alkenyl group). A compound having a functional group such as a carboxyl group, a hydroxyl group, a carbamoyl group, an ester group, a mercapto group and a carbonyl group, having 8 or more carbon atoms, preferably 12 to 50 carbon atoms, or a molecular weight of 130 to 2000, preferably 200 to 8
00 fatty acid, fatty alcohol, fatty acid amide, fatty acid ester, aliphatic mercaptan, aliphatic aldehyde,
Examples thereof include aliphatic ketones. Specifically, capric acid as a fatty acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, lauryl alcohol as a fatty alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, caprinamide as a fatty acid amide, laurinamide, Examples of the palmitic amide, stearyl amide, and stearyl acetic acid ester as the fatty acid ester can be given.

The ratio of the high molecular weight polyolefin to the diluent varies depending on their kind, but is generally 3:97 to 80:20, and particularly 15:85 to 6.
It is preferred to use it in a weight ratio of 0:40. When the amount of the diluent is lower than the above range, the melt viscosity becomes too high, which makes melt-kneading and melt-molding difficult, and the surface of the molded article is significantly rough. On the other hand, if the amount of diluent is larger than the above range,
After all, melt-kneading becomes difficult, and the stretchability of the molded product becomes poor.

Melt kneading is generally 150 to 300.
It is desirable to carry out at a temperature of ℃, especially 170 to 270 ℃, below the above range, the melt viscosity is too high, it becomes difficult to melt-mold in the next step, and if it is higher than the above range, Degradation lowers the molecular weight of the high molecular weight polyolefin, making it difficult to obtain a molded product having a high elastic modulus and high strength. The composition is Henschel mixer,
It may be performed by dry blending using a V-type blender or the like, or may be performed by melt mixing using a single-screw or multi-screw extruder.

The melt molding is generally carried out by melt extrusion molding. For example, a filament for stretching can be obtained by melt extrusion through a spinneret, and a tape for stretching can be obtained by extrusion through a flat die or a ring die. At this time, a draft, that is, stretching in a molten state, can be added to the melt extruded from the spinneret. Extrusion speed V _O of the molten resin in the die / orifice and winding speed V of the unstretched material that has been cooled and solidified
The ratio with and can be defined as the draft ratio by the following formula. Draft ratio = V / V _O Such a draft ratio varies depending on the temperature of the mixture, the molecular weight of the high molecular weight ethylene polymer, and the like, but is usually 3 or more, preferably 6 or more.

The unstretched molded product of high molecular weight polyolefin thus obtained is stretched. In the present invention, the stretching operation is performed in two or more stages. Draw ratio is 2
It is possible to carry out the stretching operation so that the stretching ratio is from 10 to 10 times, particularly from 3 to 8 times. According to the method of the present invention, once the total draw ratio of the stretched object is determined, the draw ratio in each draw tank is determined by the temperature of the heat source such as the heat medium, so the draw ratio is set finely in each draw tank. No need. Regarding the temperature of the drawing tank, it is desirable that the temperature of the first drawing tank is usually 105 to 140 ° C., and the temperature of the adjacent drawing tanks in the subsequent stages is sequentially set to 2 ° C. or higher, preferably 3 to 10 ° C. ..

As described above, the stretching operation is carried out by using a heat medium such as a heating medium, an oven, a heating plate, far infrared rays, or irradiation of microwaves. In particular, a heating medium is used. Is preferable and recommended in that temperature control can be performed accurately. Examples of the heat medium include n-decane, triethylene glycol, paraffin-based process oil, and silicone oil.

The stretched product of the high molecular weight polyolefin thus obtained can be heat-treated under restraint conditions, if desired. This heat treatment is generally 140-180 ° C,
It can be carried out at a temperature of in particular 150 to 175 ° C. for 1 to 20 minutes, in particular 3 to 10 minutes. The heat treatment further promotes the crystallization of the oriented crystal part, which brings about the shift of the crystal melting temperature to the high temperature side, the improvement of the strength and the elastic modulus, and the improvement of the creep resistance at high temperature.

The process of molecular orientation in the molded body can be known by X-ray diffraction method, birefringence method, fluorescence polarization method and the like. In the case of the stretched filament of the high molecular weight ethylene polymer of the present invention, for example, Yukichi Kure, Kouichiro Kubo: Industrial Chemistry Magazine No. 3
Vol. 9, p. 992 (1939), the degree of orientation according to the full width at half maximum, that is, the formula In the formula, H ° is the half value width (°) of the intensity distribution curve along the Debye ring of the strongest paratropic plane on the equator line. It is desirable in terms of mechanical properties that the molecular orientation is such that the degree of orientation (F) defined by is 0.90 or more, particularly 0.95 or more.

[0033]

EFFECTS OF THE INVENTION According to the present invention, a stretched product of a high molecular weight polyolefin can be stably produced without stretching unevenness with a simple device, and this device can determine the total stretch ratio of the stretched object. For example, since the draw ratio in each draw tank can be adjusted by the temperature of the draw tank, it has an operational advantage that it is not necessary to set the draw ratio in each draw tank.

[0034]

EXAMPLES The present invention will be described below with reference to examples, but it goes without saying that the present invention is not limited to these examples. Example 1 <Spinning-Drawing Step> After melting, paraffin wax kept at 90 ° C. (trade name: Lubax, manufactured by Nippon Seiro Co., Ltd., melting point = 69)
℃) 210 parts by weight of high molecular weight polyethylene ([η]
= 8.72 dl / g, average particle size = 150 μm) powder 90
After adding 1 part by weight, the mixture was stirred and mixed for 15 minutes to prepare a dispersion having a high molecular weight polyethylene concentration of 30% by weight. Then, the dispersion was rotated in the same direction with a twin-screw extruder (Plastics Engineering Laboratory: screw diameter = 39 mm, L /
D = 42) was used, and the melt temperature was set to 90 ° C. in the feeding part and 180 ° C. in the other parts, the screw rotation speed was 100 rpm, and the residence time was 5 minutes. Subsequently, the obtained mixed melt was extruded from a die having an orifice of 2.0 mm and 100 holes and spun. The spun fiber was cooled and solidified with air at room temperature in an air gap of 150 cm to obtain a 620 denier high molecular weight polyethylene spun yarn. The spun raw yarn thus obtained
100 fibers were drawn under the following conditions without winding up to obtain drawn fibers.

That is, two-stage drawing was performed using four godet rolls in a drawing tank using n-decane as a heating medium.
The temperature of the first drawing tank was 110 ° C and the temperature of the second drawing tank was 120 ° C. The draw ratio at this time was 7.0 in the first draw tank and 1.14 in the second draw tank, and the effective length of the tank was 4 m in both the first draw tank and the second draw tank. .. At the time of drawing, the rotation speed of the first godet roll was set to 10 m / min, and the rotation speeds of the second and third godet rolls were appropriately changed to obtain a drawn fiber having a desired draw ratio. In addition, a drying zone having a temperature of 110 ° C. and an effective length of 50 m was provided between the third godet roll and the fourth godet roll, and the amount of n-decane in the fiber was adjusted to 1% by weight based on the high-molecular-weight polyethylene fiber before winding. It was

<Redrawing Step> The drawn fiber wound as described above was subjected to two-step drawing in a drawing tank using two godet rolls and using triethylene glycol as a heating medium. At this time, the yarn feeding speed is 40 m / min, and the third
The temperature of the drawing tank is 146 ° C, and the temperature of the fourth drawing tank is 1
It was 48.5 ° C and the total draw ratio was 3.0 times. The effective length of the tank is 10 for both the third drawing tank and the fourth drawing tank.
It was m. As a result of the stretching, it was possible to stably stretch under the above stretching conditions. The tensile strength, tensile elastic modulus and elongation at break of the obtained drawn fiber were measured at room temperature (23 ° C.) using an Intesco universal tester 2005 type (manufactured by Intesco). The sample length between the clamps was 254 mm and the pulling speed was 254 mm / min. However, the tensile modulus is the initial modulus. The fiber cross-sectional area required for the calculation was obtained by measuring the weight and length of the fiber with the density of polyethylene being 0.96 g / cm ³ . Physical properties of the stretched high molecular weight polyethylene fiber thus obtained are shown in Table 1.

[0037]

Comparative Example 1 <Spinning-Drawing Step> In the same manner as in Example 1, high-molecular-weight polyethylene fiber was spun and drawn. <Re-stretching Step> The wound stretched fiber was subjected to two-stage stretching using three godet rolls in a stretching tank using triethylene glycol as a heat medium. Under the same temperature conditions as in Example 1, the rotation speed ratio between the godet rolls was changed so that the total draw ratio was 3.0 times. However, yarn breakage occurred frequently and drawing could only be done up to 2.5 times. Table 2 shows the physical properties of the obtained yarn.

[0039]

[Brief description of drawings]

FIG. 1 is a process drawing showing an example of a stretching method of the present invention.

FIG. 2 is a process drawing showing another example of the stretching method of the present invention.

FIG. 3 is a process drawing showing an example of a conventional stretching method.

[Explanation of symbols]

 1 feeding roll 2 winding roll 3 drawing tank 4 turn roll 5 object to be drawn 6 heat medium 7 nip roll 8 heat exchanger 9 conduit 10 drawing bath 11 drawing roll

Claims (6)

[Claims] 1. A high-molecular-weight polyolefin is melt-kneaded,
In the method of performing multi-stage drawing after melt molding, the drawing is performed by arranging a plurality of drawing tanks in series between a pay-out roll and a winding roll, and increasing the temperature of each drawing tank sequentially by 2 ° C. or more. A multi-stage stretching method for a high molecular weight polyolefin, which is characterized by being carried out by passing through a zone. 2. The multi-stage stretching method according to claim 1, wherein the heat source of the stretching tank is at least one selected from the group consisting of a heat medium, a heating plate, an oven, far infrared rays, and microwaves. 3. A multi-stage stretching device comprising a feeding roll and a plurality of stretching tanks arranged in series between the winding rolls. 4. The multi-stage stretching apparatus according to claim 3, wherein the stretching tank is provided with at least one heat exchanger for recycling a heat medium. 5. The multi-stage stretching device according to claim 3, wherein a plurality of turn rolls are provided in the stretching tank. 6. The multi-stage stretching device according to claim 3, wherein a nip roll is provided on the outlet side of the stretching tank.