JPS6052647A - Gel fiber and gel film stretching method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for high-speed stretching of gel fibers or gel films obtained by solution spinning or solution extrusion molding of high molecular weight polymers.

In this document #I, the case of gel fiber will be explained as a representative case, but this is not intended to exclude the case of gel film, and the present invention should be similarly carried out by means suitable for the film. Bye.

For example, when trying to manufacture fibers using a synthetic polymer with a large molecular weight as a raw material, the first consideration is to adopt the conventional general-purpose melt spinning method, but depending on the properties of the material, In the process of heating by conventional methods, thermal decomposition or thermal discoloration may occur before melting begins, making it impossible to achieve the intended purpose. For example, synthetic polymers such as polyvinyl alcohol and polyacrylonitrile cannot be melt-spun as substantially pure polymers, and ultra-high molecular weight materials such as polyethylene, polypropylene, polyester, and nylon cannot be melt-spun as substantially pure polymers. It is technically impossible to perform melt-spinning without physical decomposition.

In response to this situation outside the machine, a technique has been developed in which spinning is carried out without the above-mentioned decomposition with the help of an appropriate external solvent (Japanese Patent Application Laid-Open No. 107506/1983).

According to the invention, the ultrahigh molecular weight polymer can be dissolved in a solvent and processed in a liquid state, so that spinning operations can be performed at a temperature sufficiently lower than the decomposition temperature of the high molecular weight polymer. Became. According to the above disclosure, polyolefins (polyethylene, polypropylene, ethylene propylene copolymer, polyoxymethylene, polyethylene oxide, etc.), polyamides (various types of nylon), polyesters (polyethylene terephthalate, etc.), acrylic polymers (polyacrylonitrile, etc.) ), vinyl polymer (
Polyvinyl alcohol, polyvinylidene fluoride, etc.) are the targets of spinning, but if we take polyolefins as an example, nonane, decane, undecane,
Dodecane, tetralin, decalin, etc. may be employed as suitable solvents.

To explain further by giving a specific example, the molecular weight is, for example, 150
By spinning a decalin solution of ultra-high molecular weight polyethylene or polypropylene up to 3 million yen at 130 to 140°C and cooling it in air or liquid, it has a gel-like appearance and contains a large amount (e.g. 97 to 98%) of decalin. A filament is obtained, which, once wound, unrolled and hot stretched, creates molecular orientation and evaporates the decalin, producing a filament of extremely high strength. The above-mentioned filaments are generally called gel fibers, and because of their properties of high strength, high elastic modulus, and high toughness, there are great expectations in this field.

The gel fiber obtained by the above-mentioned melt spinning method is generally gelled by cooling during the spinning process, and then wound onto a bobbin as a raw yarn or stored in a tow can. Alternatively, as shown in the attached specifications of patents filed separately, the yarn is hot-stretched immediately after being discharged and then wound into a bobbin as raw yarn or stored in a tow can for medical purposes or transportation. Therefore, the solvent that makes up the filament is desorbed during storage and transportation, causing further gelation of the gel-like filament, and unless the speed of hot stretching is kept low, there will be frequent occurrences of yarn breakage during stretching. There was fear. Therefore, the drawing speed of the raw yarn was inevitably low, which became a bottleneck in improving productivity.

The present invention was made in view of this situation, and a novel hot-stretching method was developed with the aim of improving the hot-stretching speed.

The present invention was completed following these circumstances,
When subjecting a solvent-containing or solvent-free gel fiber or gel film produced by melt molding of a synthetic polymer to a stretching process, a solvent is added to the gel fiber or gel film to be subjected to the stretching process. The gist of the present invention lies in that stretching is performed while applying the film.

The gel fiber used in the present invention is prepared by adding
It is obtained by spinning a spinnable raw material liquid in which a synthetic polymer to be converted into fibers is dissolved.

When selecting a solvent, it is necessary to choose one that satisfies the following basic requirements. That is, the solvent is selected to be a single low molecular weight compound or a mixture of low molecular weight compounds to aid in the processing of the ultra high molecular weight polymer, and the compound is selected to cause the ultra high molecular weight polymer to be in solution only at elevated temperatures. Must be. However, this melting temperature must be lower than the decomposition temperature of the ultra-high molecular weight polymer. Therefore, at low temperatures, such as room temperature, the low molecular weight compound or mixture thereof must be a non-solvent for the ultrahigh molecular weight polymer.

Any solvent may be used as long as it satisfies these basic requirements and is not particularly limited.

When spinning gel fibers, the synthetic polymers that are converted into fibers in order to obtain the desired high-strength, high-modulus fibers include polyolefins, polyamides, polyesters,
Examples include, but are not limited to, polyacrylonitrile, poly(vinyritine fluoride), polyvinyl alcohol, and ultrahigh molecular weight polymers thereof.

Among the above-mentioned ultra-high molecular weight polymers, ultra-high molecular weight polyethylene having a weight average molecular weight of 1 x 10' or more, preferably 1 x 106 or more is used as a synthetic polymer for fiber conversion to carry out the present invention. The present inventors have found that extremely high strength and high modulus fibers can be obtained by this method.

Gel fibers obtained by solution spinning can be easily produced by melt spinning using a melt spinning apparatus equipped with a general screw extruder or by a known dry spinning method.

Gel fibers containing a solvent can be obtained by passing the gel fibers obtained by the above-mentioned spinning method, for example, through a water bath or by blowing a medium such as air to cool them and passing them through a spinning tube.

On the other hand, a gel fiber that does not contain a solvent [corresponding to the solid matrix of a wet gel, refers to a solid matrix in which the liquid in a wet gel is replaced with a gas (e.g., an inert gas such as nitrogen or air), and is called a "xerogel"). ] is a method in which the solvent is removed from the gel fiber by blowing high-temperature air onto the gel fiber obtained by the solution spinning method, or by replacing the solvent with a low boiling point solvent other than the solvent occluded by the gel fiber. It can be easily manufactured by a method of removing . In addition, when multi-stage hot drawing is performed, the drawn yarn in the latter half can be regarded as "gel fiber containing no or only a small amount of solvent."

The gist of the present invention is to apply any solvent, whether solvent-containing or non-solvent-containing, to the raw yarn (
(drawn yarn in the second and subsequent stages of multi-stage stretching)
The point is that the stretching is carried out while imparting. In the case of a solvent-containing type, it is recommended to apply the same or similar solvent to the solvent.

For example, in the case of hot plate stretching, the solvent is supplied to the entrance side of a guide slit provided in the hot plate from the surface of the core slit or from the bottom of the slit, and is introduced along the slit. A method in which a solvent is applied to the yarn, etc. (so-called guide oiling method), in which the yarn, etc. is introduced along the circumference of a solvent semi-immersed rotary coating roller that is installed on the inlet side of the hot plate and away from the hot plate. An example of this is a method in which a solvent is applied thereto (so-called roller oiling method).

However, the illustrated method is merely a representative example, and it goes without saying that other solvent application means may be employed. In addition, gas or liquid may be used as a heat medium in the hot drawing method in addition to the solid (hot plate) mentioned above, and the hot drawing method itself varies depending on the type of medium (for example, a method in which it is passed through a tubular passage, (oven method), it is desirable to select a solvent application technique that is easily compatible with each method. In addition, although hot stretching can be completed in one stage, it is recommended to perform it in multiple stages, thereby increasing the tensile strength and initial elastic modulus.

That is, according to separate research by the present inventors, by performing two or more stages of multi-stage stretching, for example, in the case of polyethylene gel fiber, it is possible to increase the tensile strength to about 40 g/d or more and the initial elastic modulus to about 1200 g/d or more. I know it will happen. Also, according to a separate study, the drawing zone inlet temperature is
The temperature is higher than the melting point diagram of the supplied fiber and lower than the melting point (B) of the supplied fiber, and the drawing zone exit temperature is higher than the melting point (B) of the supplied fiber and the melting point (D) of the fiber after drawing. By arranging a drawing zone with a very low temperature, it is possible to obtain a high-strength, high-modulus fiber by approaching a stretched chain structure, which is considered to be one of the ultimate structures for increasing strength, formed during the deformation process. It has been confirmed that it is possible to obtain If the fiber is stretched outside the above-mentioned range, "whitening" or sharp necks tend to occur, resulting in unstable phenomena, making it impossible to obtain fibers with high strength and high elastic modulus.

In other words, stable stretching can be achieved by stretching at a temperature between the melting point and the melting point of the gel fibers supplied for stretching, but sharp necks tend to form, and it is difficult to obtain a structure close to a stretched chain structure during the deformation process. Fibers with high strength and high elastic modulus cannot be obtained. In addition, when drawing is carried out below the melting point of the gel fiber, a "whitening phenomenon" occurs, and when drawing is carried out above the melting point of the supplied fiber throughout the stretching zone, fibers with high strength and high elasticity are broken due to yarn breakage. By stretching under such a temperature gradient, it becomes possible to stretch at an ultra-high stretching ratio of at least 40 times or more, and it becomes possible to obtain an even more extended chain structure. Therefore, if a multi-stage stretching method is employed and the temperature gradient conditions mentioned above are observed, it is possible to draw high-strength gel fibers at high speed.

FIG. 1 is a schematic diagram of a multi-stage stretching method suitable for carrying out the present invention, and in the case of (a), the supply fiber is supplied from the supply 4-ra 3). A suitable solvent is applied thereto, and the film is passed through a first stretching zone where the desired temperature gradient can be controlled so that the inlet temperature and exit temperature are higher than the temperature at the heating elements 6 and 7, and stretched in 91 stages by the stretching roller 4. Then, after uniformly applying a suitable solvent for producing gel fibers in the first stage 5 using the solvent applying device 8, a desired temperature gradient is created using the heating elements 6 and 7 so that the inlet temperature is higher than the exit temperature. A schematic diagram of a continuous multi-stage stretching method is shown in which the second stretching zone is controlled to pass through a second stretching zone, and the second stage of stretching is performed by the stretching roller 5. In the same way as in the case of eye drawing, the supplied fiber is supplied through the supply roller 3, an appropriate solvent for gel fiber production is applied using the solvent applying device 8, and the desired temperature is adjusted using the heating elements 6 and 7 so that the exit temperature is higher than the inlet temperature. The drawn yarn is passed through a stretching zone whose gradient can be controlled, and stretched by a stretching roller 4. After the drawn yarn is once wound up, the drawn yarn is fed back to the same stretching zone where a desired temperature gradient is applied. FIG. 2 is a schematic diagram of a discontinuous multi-stage stretching method in which stretching is performed by It should be noted that the heating elements 6 and 7 are not limited to two or more divided parts, but may be a single unit that can provide an arbitrary temperature gradient in the range from the entrance to the exit of the stretching zone.

Since the present invention is constructed as described above, it has become possible to increase the drawing speed and to greatly improve the productivity of gel fiber or gel film production.

The present invention will be described in detail below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Ultra-high molecular weight polyethylene having a weight average molecular weight of I x 10' was dissolved in decalin at 160°C to obtain a 3 wt % solution.

This solution was slowly cooled to 60°C, and then rapidly cooled from 60°C to room temperature to obtain a gel-like material. After removing the film-like and strong large-sized gel-like material from the gel-like material, the spherulite gel was isolated using a homomixer, and after the solvent and the spherulite gel were separated in a furnace, it was poured into decalin again. The mixture was uniformly dispersed using a homomixer, and the amount of polyethylene was adjusted to 3 wt % to obtain a uniform dispersion of spherulite gel. The homogeneous dispersion was supplied at room temperature to an extruder hopper of a melt spinning apparatus equipped with an ordinary screw type extruder for melt spinning. The spinning temperature is 156
The solution discharge rate was 20 g/sin at °C, and the spinneret used had a hole diameter of 0.8 mm, a hole length of 8n+n+, and a number of holes of 18. The discharged solution was cooled by passing through a stream of air maintained at room temperature to produce gel fibers containing the solvent.

The gel fibers obtained as described above and the stretched gel fibers were subjected to various stretching experiments from Nnl to 15 under the stretching conditions shown in Table 1, using the stretching method shown in Figure 1 (old). Table 1 shows the evaluation results of the physical properties and operability of each drawn yarn obtained.

Experimental section 1.2.5.6.9.10 shows an example of one-stage stretching in which gel fibers are directly stretched.

Actual #Nn3.4.7.8.11.12.13 shows an example of two-step drawing in which the fibers drawn in one step are drawn discontinuously. Experiments Nα14 and 15 show examples of three-stage stretching in which the fibers after the two-stage stretching in Experiment N[113 were drawn discontinuously. Experiments were conducted on the cases in which a solvent was applied in each stretching process and the cases in which the film was stretched without applying any solvent at all. In addition, in the case of Experiments 1m14 and 15, the decalin occluded in the fast gel fibers was not contained at all inside the fibers subjected to stretching. As a result, in the examples with solvent application, the stretching speed was able to be increased to 5 m to 6 m/min, but in the examples without solvent application, the stretching speed could only be increased to 4 m/min at most. , the difference cannot be ignored.

Experimental direction 1 that does not satisfy the above conditions regarding the stretching temperature gradient
．． Samples Nos. 5 and 9 showed inferior tensile strength and initial modulus of elasticity, as well as poor operability, compared to those that satisfied the above conditions. In addition, in the present invention, when the stretching zone is passed through in one stage, that is, compared to the experiment Nα2.6.10, it is discontinuously
Experiment N113.4.7.8.11.12 with stage stretching
．． In the case of No. 13, the tensile strength and initial elastic modulus tended to increase, and experiment N [Li2
In the case of , the operability is good, the tensile strength is so, xg/d, and the initial elastic modulus is 1750.4 g/d, which is the highest value in this example.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the stretching method according to the present invention. 1...supply fiber 2...Fiber after stretching 3... Supply roller 4.5...Stretching roller 6.7... Heating body 8...Solvent application device Applicant: Toyobo Co., Ltd. Figure 1 (4) Figure 1 (b)

Claims (2)

[Claims] (1) When subjecting a solvent-containing or solvent-free gel fiber or gel film produced by melt molding of a synthetic polymer to a stretching process, a solvent is not added to the gel fiber or gel film to be subjected to the stretching process. A gel fiber or gel film stretching method characterized by stretching the gel fiber or gel film while applying the gel fiber. (2) Stretching of the gel fiber or gel film according to claim 1, wherein the gel fiber or gel film is made of ultra-high molecular weight polyethylene having a weight average molecular layer of at least IXIO' or more. Method.