JPS60239509A - Production of high-strength and high-modulus polyolefin based fiber - Google Patents

Abstract

PURPOSE:To suppress effectively the gluing between fibers and obtain the titled fibers for ropes, etc., by passing a solution of a polyolefin having a specific weight-average molecular weight through an inert gas atmosphere, extruding the resultant solution into a coagulation bath, removing a solvent from the spun filaments, and hot-drawing the resultant filaments under specific conditions. CONSTITUTION:A solution containing 0.5-15wt% polyolefin based polymer, e.g. high-density polyethylene, having >=5X10<5> weight-average molecular weight is passed through an inert gas atmosphere layer and extruded into a coagulation bath to give coagulated filaments, and a solvent is then extracted and removed therefrom to give filaments. The resultant filaments are then hot-drawn at a temperature of the melting point of the polyolefin based polymer -70 deg.C lower than the melting point at >=10 times draw ratio to afford the aimed fibers. Decalin, etc. is preferred for the solvent to be used for preparing the spinning solution.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for producing polyolefin fibers having high strength and high modulus characteristics,
In detail, a solution of an ultra-high molecular weight polyolefin polymer is extruded into a coagulation bath through a gas atmosphere layer, and after forming a coagulated thread, the solvent is removed, and then hot stretching is performed.Thus, high strength is obtained. It has the characteristics of large size and high modulus.

Furthermore, the present invention relates to a method for producing a polyolefin multifilament without sticking between single filaments.

(Prior art) In recent years, semi-dilute solutions of ultra-high molecular weight polyolefin polymers have been spun, cooled to gel, and then desolventized.
A method for producing fibers with extremely high strength and modulus by super-stretching (Japanese Patent Application Laid-Open No. 56-15408
Issue: ■Journal of Materials
5science, Vol, +5.

pp s o s ~ 514 (1980), ■ Japanese Patent Application Publication No. 1983
-5228, etc.), and the polyolefin fibers obtained in this way are used as industrial fibers that require high strength and high modulus due to their characteristics.
For example, it is expected to be useful in ropes, slings, various rubber reinforcing materials, various resin reinforcing materials, and concrete reinforcing materials.

However, the high-strength, high-modulus polyolefin fibers produced by methods (e) of (1), (2), and (3) above have a problem in that sticking occurs between the single yarns during the manufacturing process. That is, in the above methods ① and ②, the solution is spun,
When the gel yarn obtained by cooling is subjected to hot stretching after drying the solvent or while drying, significant adhesion between the single yarns occurs; By first extracting the solvent from the gel threads obtained and then drying them, this agglutination between single threads can be suppressed to some extent, but this is still not sufficient. The sticking between single yarns that occurs in this way leads to problems such as a lack of fiber flexibility, a decrease in the overall strength of the fiber, and a decrease in the strength utilization rate during heating. Despite the expected usefulness of high-strength, high-modulus polyolefin fibers as described above, there are many inconveniences in making full use of their properties, and it is difficult to mass-produce them on an industrial scale. The reality is that it has become extremely difficult.

Regarding the causes of agglutination between single yarns, see ff.
Although this is not clear, the individual filaments spun from a solution and gelled by cooling are in a swollen state containing a large amount of solvent, and are nestled closely together.
It is thought that significant agglutination will occur if only a single drying and desolvation process is performed. In fact, especially in the non-crystallized portion of the gelled single filaments, the solution is simply supercooled, and there are virtually no boundaries between the single filaments.

Moreover, instead of removing the solvent by single-layer drying, if a method is used in which the solvent is first extracted with an extractant and then drying is performed, the agglutination between the single filaments is somewhat alleviated, but it is still insufficient.

(Problems to be Solved by the Present Invention) The present inventors aimed to effectively suppress the above-mentioned sticking between single filaments and to produce a polyolefin multifilament with high strength and high modulus. As a result of intensive investigation, we found that the cause of sticking was that the cooled gel threads were dried or extracted in bundles to remove the solvent. The surface of the yarn is coagulated with a coagulant, then the residual solvent is extracted and removed, and the surface of the single yarn is roughly rubbed.

It is possible to effectively prevent single filament sticking during drying, and the dried yarn obtained in this way does not stick even during the subsequent hot drawing process, and the dried yarn is further heated to a temperature higher than the melting point. It has been discovered that fibers with high strength (20 g/d or more) and high modulus (400 g/a or more) can be obtained by hot drawing 10 times or more at a temperature 70°C lower,
We have arrived at the present invention.

(Means for solving the problem) That is, the present invention extrudes a solution containing 5 to 15% by weight of a polyolefin polymer having a weight average molecular weight of 5xiO" or more through an inert gas atmosphere layer into a coagulation bath, After coagulating into a yarn, the solvent is further extracted and removed, and the resulting fiber is then hot-stretched by 10 times or more between the melting point of the polyolefin polymer and a temperature 70°C lower than the melting point. The present invention provides a method for producing high-strength, high-modulus polyolefin fibers that do not cause stickiness between single yarns.

The polyolefin polymer used in the present invention is a polymer typified by polyethylene, polypropylene, polybutene-1, poly(4-methylpentene-1), etc., but a mixture of these or a composition of two or more of these monomers may also be used. It may also be a copolymer consisting of units. Alternatively, it may be a copolymer obtained by copolymerizing a cholera monomer as a main component with a small amount of other non-olefinic monomer units, or a chemically treated polyolefin.

The molecular weight of the polyolefin polymer used in the present invention is 5 x 10s or more in terms of weight average molecular weight.

It is preferable that the weight average molecular weight is less than 5 x 10'', since the strength and modulus of the obtained fibers will be low and the fibers will lack usefulness.

In addition, the solvent used to form the solution of the polyolefin polymer includes, but is not limited to, aliphatic hydrocarbons, alicyclic hydrogen acidification, aromatic hydrocarbons, and mixtures thereof. isn't it. Polyolefin polymers usually have these solvents and the temperature is 60℃.
Since it will not dissolve at temperatures below 100° C., it is often heated to 100° C. or higher, and for this reason, low boiling point solvents are not preferred. Suitable solvents include decalin, xylene, tetralin, cyclohexane, nonane, decane and paraffin oil.

Moreover, those that are solid at room temperature such as paraffin wax and naphthalene can also be used.

The polymer sickleness of the polyolefin polymer solution is selected to be lower as the molecular weight of the polyolefin polymer is larger, and moreover, the uniformity during dissolution is selected.

The concentration is selected so as to provide an appropriate solution viscosity in terms of ejection stability during spinning, spinnability, and refinability during drawing. However, if the polymer transfer is less than 0.5% by weight, it is not preferable because not only is the productivity poor, but the coagulated yarn is soft and the yarn runnability becomes unstable, making it susceptible to external disturbances and lacking in uniformity. In addition, the higher the polymer concentration, the higher the productivity, but if it exceeds 15% by weight, the viscosity of the solution increases due to the increase in entanglement of polymer molecular chains in the solution. However, if the concentration range is too high, not only will the threadability and yarn properties deteriorate during spinning, but
This is not preferred because the stretching ratio cannot be increased sufficiently during stretching after solvent removal, and only poor physical properties can be obtained. Therefore, the polymer concentration of the polyolefin polymer solution is 0.5 to 15% by weight.
, particularly preferably 1 to 8% by weight.

The polymer dissolution temperature at the time of solution preparation and the solution temperature at the time of spinning are approximately the same, but vary depending on the solvent and polymer molecular weight, and an appropriate temperature is generally set in the range of 120 to 250°C.

In carrying out the method of the present invention, the polyolefin polymer solution is first heated and extruded into a coagulation bath through an inert gas atmosphere through a nozzle having a plurality of holes. The inert gas atmosphere referred to here is one in which the fibrous solution extruded from the nozzle does not coagulate or undergo chemical reactions. Use air or roof.

There is no particular limit to the distance through which this gas atmosphere passes, but it is between 3 and 50! The range of Il+ is appropriate; if it greatly exceeds 5-OM, it becomes difficult for the fibrous solution extruded from the nozzle to run stably, and problems such as slight yarn wobbling can cause sticking between single yarns in this gas atmosphere. This is not preferable because it is more likely to occur.

In addition, the solvent may evaporate and escape from the extruded fibrous solution in this gas atmosphere, but
Most of the solvent is extracted away in the next coagulation bath and subsequent extraction bath.

In the present invention, the coagulant used in the coagulation bath and extraction bath is a hydrocarbon or a hydrocarbon containing chlorinated fluorine, such as hexane, hep-1'7. Examples include methylene chloride, hypochlorite tetrachloride, ethane trichloride and trifluoride, ketones such as acetone, and alcohols such as methanol and ethanol. Does the temperature of the coagulation bath and extraction bath depend on the coagulation ability and boiling point of the coagulant used? Although the temperature varies from this point onwards, a range of 0 to 40°C is usually appropriate.

The yarn coagulated in the coagulation bath is then sent to an extraction bath, where the remaining solvent is extracted and removed, and then sent to a drying process while still containing the coagulant (i.e., extractant). Drying is carried out by bringing the yarn into contact with heated rolls or by exposing it to a stream of heated air. Also, at this time, the extractant may be replaced with a second extractant and then dried. For example, replacing the flammable first extractant with a second, less flammable extractant.

The yarn thus dried is then subjected to a drawing process. Various means can be used for stretching, including a hot plate, a heated roll, and a dry heat tube, but the method is not particularly limited. Stretching is carried out at a temperature between the melting point of the polymer and 70° C. below the melting point. In order to make the stretching ratio as high as possible and increase the strength, it is more preferable to use a temperature between the melting point of the polymer and a temperature 40° C. lower than the melting point.

If the stretching is carried out at a temperature 70°C or more lower than the melting point of the polymer, the stretching ratio will not be sufficiently increased and only threads with poor physical properties will be obtained. Furthermore, if the stretching temperature exceeds the melting point, the yarn will melt, which is not preferable. However, when drawing with a dry heat tube, the yarn is heated with gas, so it may be possible to draw at a temperature that is apparently higher than the melting point of the polyolefin polymer in terms of heat transfer efficiency, but the melting point as used in the present invention is In this case, substantially t includes the temperature at which the threads melt.

It is necessary to set the stretching ratio to 10 or more.

If the stretching ratio is less than 10, sufficiently high strength and modulus cannot be achieved, resulting in a lack of usefulness. Since the yarn spun according to the present invention has particularly little entanglement of polymer molecular chains, it can be drawn at a high stretching ratio, preferably at a stretching ratio of 15 or more.

Next, the present invention will be specifically explained using Examples and Comparative Examples.

The yarn physical properties shown below were measured under the following conditions.

Yarn sample: Single yarn (threads that cannot be defibrated are made into multifilament as they are) Paper length: 1250 tensile speed: 300 min/min Atmosphere: 120°C, 65% relative humidity Example 1 Straight chain fiber with weight average molecular weight of 3.0 x 10' Density polyethylene was dissolved in decalin at a temperature of 160°C to make a 40% by weight solution, and the solution was extruded into an air bath through a nozzle with a hole size of 1 and a number of holes of 20, and after passing through the air bath a distance of 81111. , coagulated in a coagulation bath consisting of acetone at 10°C. The total discharge rate from the nozzle was 16 CC/min, and the coagulated yarn was 7.5 mm. I picked it up in 7 minutes.

The yarn was then passed through an extraction bath consisting of acetone at 10°C to extract the remaining decalin in the yarn, and then heated at 60°C.
The film was dried and rolled up by heating the film (μm)vP. This dried yarn was drawn using a hot plate with a surface temperature of 135°C and a length of 12 oa* at various magnifications shown in the first axis. The mechanical properties of the obtained drawn yarn are also shown in the first axis. . Note that the yarn feeding speed during drawing was 20α/min.

As is clear from the results in Table 1, there is no difference between the single yarns in both the yarns that have been dried after solvent removal and the yarns that have been hot-stretched. In addition, the strength of the drawn yarn becomes 20 g/d or more only when the drawing ratio is 10 times or more, and the modulus is also 6.
The value exceeds 00g/d.

Table 1 Relationship between drawing ratio and yarn physical properties Comparative Example 1 The same spinning stock solution as in Example 1 was extruded into 15°C water through an 8ia air bath through a nozzle with a hole diameter of 1 mm and a number of holes of 20, and cooled. From step 1, a comb-shaped gel thread was obtained. The total discharge amount from the nozzle and the spinning take-off speed were the same as in Example 1, and after leaving the water cooling bath, it was brought into contact with a heating roll whose surface temperature was 85° C. to remove the solvent, decalin, by drying. The dried yarn obtained by this method had significant adhesion between single yarns, and was completely impossible to separate into single yarns. In addition, the gel threads that had exited the water cooling bath were subsequently passed through an extraction bath of acetone at 15°C to extract the solvent, and then similarly dried using heated rolls, but the stickiness between the single threads was somewhat high. Although I was able to get some relief, it was still not enough. This state of adhesion between the single yarns was not improved even after the first hot drawing, and compared to Example 1, the single yarns of the gel yarn were removed by drying or extraction in a close contact state after the desolvation. It is thought that this hinders the separability (fibrillation property) of single filaments.

Since the yarns obtained by the above two methods have poor fibrillation properties and cannot be separated into single filaments, Table 2 lists the yarn physical property values measured as multifilaments.

Table 2 Silk spinning method and fibrillation properties Example 2 Linear high-density polyethylene with a weight average molecular weight of 9.0 x 10' is dissolved in decalin at a temperature of 160°C to make an aO weight % solution, and the solution is mixed with a pore size of 1. The mixture was extruded into an air bath through a nozzle with 20 holes, passed through the air bath by a distance of 10 squares, and then coagulated in a coagulation bath consisting of acetone at 12°C.

The total discharge rate from the nozzle was 16 cc/min, and the coagulated thread was drawn at 7.5 m/min. Continuing the thread 1
Decalin remaining in the system was extracted through an extraction bath consisting of acetone at 2°C, dried on one heated roll at 60°C, and then wound up.

The dry yarn was drawn under the same conditions as in Example 1, except for the stretching ratio. As a result, the physical properties of the drawn yarn were as shown in Table 3. From the results in Table 3, it is clear that according to the method of the present invention, yarns with high strength and high modulus can be obtained without sticking between single yarns.

Table 3 Comparative Example 2 Linear high-density polyethylene with a weight average molecular weight tsx+o' was dissolved in decalin e at a temperature of 150°C to make a 15% by weight solution, and this solution was applied to a nozzle with a hole diameter of 1 head and a number of holes of 20. After passing through the air bath at a distance of 10 wR, the sample was coagulated in a coagulation bath consisting of acetone at 12°C.

The total discharge rate from the nozzle was 12 CC/min, and the coagulated yarn was taken off at 75 m/min. Continue this yarn by 1
After extracting decalin through an extraction bath consisting of acetone at 2°C, it was dried and rolled up using a heated roll at 60°C. This dried yarn was stretched with a hot plate having a surface temperature of 130° C. and a length of 20 mm, and the results were as shown in Table 4. As a result, no stickiness between single yarns was observed, but the strength level of the obtained fibers was as low as about 15 g/σ, which was disappointing. It is clear that if the molecular weight of the polymer is lower than the range of the present invention, the physical properties cannot be obtained.

Table 4 Example 3 Same as Example 1? Table 5 also shows the results of examining the influence of the temperature conditions on the physical properties of the drawn yarn by changing the stretching temperature conditions of the thus obtained solvent-free and dried yarns as shown in Table 5. Note that the drawing ratio was set to the highest value at each drawing temperature, and the highest yarn physical property values at each drawing temperature are listed in Table 5.

As is clear from the results in Table 5, when the stretching temperature is lowered to 60°C, the stretchability is extremely reduced.

The strength of the drawn yarn obtained is also low, being less than 20 g/(l). When the drawing temperature is + so'ct, it melts and breaks on the hot plate, leaving the cut end of the yarn in a melted state.

Furthermore, when the melting points of the polymer powder and the dried yarn are measured using a DSG (differential thermal analyzer), they are 135°C and 137°C, respectively, and furthermore, the melting point of the yarn under stretching tension is substantially 1.
The temperature is about 140 to 145°C, and if the stretching temperature reaches 150°C, it will melt and flow.

Further, when the stretching temperature is 60°C, the actual melting point is 140°C and a temperature 70°C lower than this, which is outside the scope of the present invention, and a high stretching ratio cannot be achieved.

Table 5 (Effects of the present invention) As explained above, according to the method of the present invention, polyolefin fibers with extremely high strength, soba modulus, and no glue between single filaments can be obtained, and the resulting fibers are In addition to the above, it is flexible and does not reduce the strength utilization rate during heating or reduce the cut fI strength when knotting, making it extremely useful for each of the four industrial applications, especially for various reinforcing material applications.

Patent applicant Higashi Shikikai Co., Ltd.

Claims (1)

[Claims] A solution containing 05 to 15% by weight of a polyolefin polymer having a weight average molecular weight of 5X'IO' or more is extruded into a coagulation bath through an inert gas atmosphere layer to form a coagulated thread, and then further The solvent is extracted and removed, and the resulting fiber is heated at 70°C below the melting point of the polyolefin polymer.
A method for producing a high-strength, high-modulus polyolefin fiber, which comprises hot-stretching the fiber by 10 times or more at a low temperature.