JP2003105633A - Method for producing thermoplastic synthetic fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a thermoplastic synthetic fiber by which mechanical characteristics, especially strengths are improved with a slight load on the environment. SOLUTION: This method for producing the thermoplastic synthetic fiber comprises adding 0.3-6 wt.% of carbon dioxide and/or nitrogen to a crystalline thermoplastic resin having >=5,000 poises melt viscosity at 290 deg.C and 20 sec<-1> , performing melt mixing and then carrying out core-sheath conjugated spinning of the resultant resin mixture as a core component and a thermoplastic resin having >=3,500 poises melt viscosity at 290 deg.C and 20 sec<-1> as a sheath component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thermoplastic synthetic fiber, and more particularly to a method for producing a thermoplastic synthetic fiber having improved mechanical properties, particularly strength, which has a low environmental load.

[0002]

Polyester terephthalate and other polyester fibers have well-balanced characteristics in strength, elastic modulus and dimensional stability and can be manufactured at a relatively low cost, so that they can be used not only for clothing but also for industrial applications. Widely used.

When polyester fibers are used for industrial applications, the most important characteristic is generally mechanical properties, for example, high strength, and further improvement of mechanical properties for expanding the industrial application of polyester fibers. The demand for is increasing.

A typical method for producing high-strength polyester fibers is "Handbook of Fibers" p.107 (edited by The Textile Society of Japan, Maruzen (1994)).
The method of obtaining a low orientation raw yarn with high [η] polyethylene terephthalate and subjecting it to high-strength drawing and high-temperature setting has been adopted for a long time, and an increase in [η], that is, a molecular weight is effective for increasing strength. Is generally known.

However, in melt spinning which is industrially adopted in polyester, a high molecular weight polymer has a high melt viscosity, requires a large apparatus, and has poor spinnability, resulting in spun yarn breakage, resulting in stable spinning. However, there is a problem in that yarn breakage occurs when the draw ratio is further increased.

As a method for solving this problem, a technique is known in which a plasticizer is added to high molecular weight polyester to reduce the melt viscosity (Japanese Patent Laid-Open No. 5-247436, etc.). For example, in Japanese Patent No. 3161546, by adding at least one compound selected from a biphenyl compound, a naphthalene compound, a phenyl ether compound or a mixture thereof, (1) reduction of melt viscosity-improvement of processability (2) Adoption of low spinning temperature-suppression of thermal decomposition during melting is described as an advantage. It seems that this technology can achieve high strength, but when additives are used, depending on the type, environmental pollution in the spinning process due to volatilization, equipment contamination due to bleed-out, and a large amount of components remaining in the fiber may occur. For example, there is concern about the impact on users, and also about the environmental destruction at the time of disposal. Furthermore, since the additive is basically different from polyester, it causes deterioration of the spinnability and process stability due to the precipitation of the additive during long-term operation, and the quality of the obtained product may be poor. Is also expected to have an adverse effect.

On the other hand, it has been attracting attention in recent years that a plasticizing effect is exhibited by adding carbon dioxide or the like to a polymer melt. For example T. Hobbs, AJLesser, polymer, 41,
Polyethylene terephthalate fiber is used in 6223 (2000).
C., a technique for obtaining 1.1 GPa high-strength fiber by stretching in liquid carbon dioxide and then again under dry heat of 200 ° C. is disclosed. Improvements are mentioned. However, this technique uses carbon dioxide at the time of drawing and requires pressurizing conditions, so continuous treatment of yarns is not suitable for industrialization because the equipment becomes bulky.

On the other hand, many techniques for adding carbon dioxide or the like to a molten polymer like an ordinary plasticizer are found in the field of foam molding of polyolefins, but the addition of polyester or polyamide in melt spinning is slightly special. It can only be found in Kaihei 11-172528. However, the publication does not mention the foaming behavior after discharge, which is the most problematic when adding carbon dioxide, but if the control of the foaming behavior is insufficient, the die stain becomes severe and the yarn breakage frequently occurs. There are challenges. Further, regarding the amount of addition, it is only described that "absorption and / or adsorption amount is sufficient if the amount is 0.2% by weight or more." No technical suggestions are given. Furthermore, the technique described in this publication has only the effect of reducing the viscosity and the effect of improving the elongation in high-speed spinning, and does not give any suggestion to the effect of improving the mechanical properties of the obtained fiber.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned problems of the prior art and to provide a process for producing a thermoplastic synthetic fiber having improved mechanical properties, particularly strength, which has a low environmental load. Especially.

[0010]

Means for Solving the Problems The inventors of the present invention have made extensive studies on the addition / mixing technology and the foaming control technology in the melt spinning of carbon dioxide and nitrogen, and the improvement of the mechanical properties of the obtained fiber. Among them, it was found that the drawbacks of the prior art can be solved by performing core-sheath type composite spinning and further satisfying certain conditions such as melt viscosity of each resin of core component and sheath component and addition amount of carbon dioxide and nitrogen. The present invention has been reached.

That is, according to the present invention, a thermoplastic resin obtained by adding 0.3 to 6% by weight of carbon dioxide and / or nitrogen to a crystalline thermoplastic resin having a melt viscosity of 5,000 poise or more at 290 ° C. and 20 sec ⁻¹ and melt-mixing the thermoplastic resin. Mixture as core component, 290 ℃, 2
It is intended to provide a method for producing a thermoplastic synthetic fiber, which comprises performing a core-sheath composite spinning using a thermoplastic resin having a melt viscosity at 0 sec ⁻¹ of 3500 poise or more as a sheath component.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The requirement of the present invention is to add 0.3 to 6% by weight of carbon dioxide and / or nitrogen to a crystalline thermoplastic resin having a melt viscosity of 5,000 poise or more at 290 ° C. and 20 sec ⁻¹ ,
Using the melt-mixed thermoplastic resin mixture as the core component,
The core-sheath type composite spinning is performed by using a thermoplastic resin having a melt viscosity of 3500 poise or more at 20 ° C. and 20 sec ⁻¹ as a sheath component.

By carrying out melt spinning under such conditions, it is possible to produce a thermoplastic synthetic fiber having improved mechanical properties, particularly strength, with a small load on the environment. The reason for this is not fully clear, but will be described in detail below.

What is necessary to obtain a high strength fiber is to sufficiently stretch the molecular chain after spinning a high molecular weight crystalline thermoplastic resin, and it is effective to add a plasticizer to enhance the stretchability. Is a technique. Furthermore, the use of gases existing in the atmosphere, such as nitrogen and carbon dioxide, is very important in terms of reducing the load on the environment. However, it has been found that when a substance that is a gas at normal temperature and pressure, such as nitrogen and carbon dioxide, is added and mixed into the melt, there is a problem of foaming immediately after spinning, which makes it impossible to produce a yarn.

Therefore, the inventors of the present invention have conducted an analysis on the foaming behavior and found that the yarn-forming property is significantly reduced when the foaming diameter itself is larger than when the number of bubbles generated by foaming is large. Therefore, as a result of studying a technique for reducing the foam diameter, it was found that the foam diameter can be reduced by increasing the melt viscosity of the resin to which nitrogen or carbon dioxide is added.

However, since bubbles still exist on the surface, the spinnability cannot be said to be good, and the mechanical properties of the obtained fiber were not satisfactory. For this reason, when further studying the technology that does not generate bubbles on the surface and the technology that minimizes the foam diameter, core-sheath composite spinning was performed, and the melt viscosity of the sheath component at 290 ° C, 20 sec ^-1 was 35
We have found that the problem mentioned above can be solved when the value is 00 poise or more.

As described above, no bubbles were present on the surface, and further, the expandability of the fiber obtained by making the foaming diameter as small as possible was greatly improved, and the improvement range of the mechanical properties was also large. The reason for this is not clear, but it is presumed that the dispersibility of nitrogen and carbon dioxide in the melt is improved and the plasticizing effect is enhanced.

Thus, a core-sheath type composite spinning using a resin mixture in which nitrogen or carbon dioxide is added and mixed with a crystalline thermoplastic resin having a sufficiently large melt viscosity as a core component and a thermoplastic resin having a melt viscosity satisfying a specific condition as a sheath component. By carrying out, it is possible to obtain a fiber whose foaming is suppressed and whose mechanical properties are improved.

The crystalline thermoplastic resin used as the core component in the present invention is not particularly limited, but it is preferable to use polyester or polyamide from the viewpoints of physical properties of fibers and production cost, and more preferably polyethylene terephthalate and polypropylene terephthalate. , Polybutylene terephthalate, polyethylene naphthalate, polyhexamethylene adipamide or polycapramide, most preferably polyethylene terephthalate. Further, the crystalline thermoplastic resin in the present invention may be copolymerized with other components within a range not impairing the gist of the invention, and further contains a small amount of additives such as matting agents, flame retardants, and lubricants. Is also good.

The thermoplastic resin used for the sheath component is not particularly limited as long as the melt viscosity satisfies specific conditions, but the core component and resin composition are basically used to prevent problems such as peeling at the interface of the core-sheath composite. Are preferably the same. The phrase "the resin composition is basically the same" as used herein means that the structural formulas of the main repeating units of the thermoplastic resins are the same. However, additions to the extent not exceeding 10% by weight and differences in the copolymerization component, molecular weight, melt viscosity, etc. are optional.

The molecular weight of the crystalline thermoplastic resin as the core component used in the present invention is not particularly limited, but it is desirable that the molecular weight is sufficiently large in order to enhance the mechanical properties of the obtained fiber and to suppress foaming. Use a resin with a melt viscosity of 5,000 poise or higher at 20 sec ^{-1 at} 290 ° C. It is preferable that the molecular weight, that is, the melt viscosity is high, but if it is excessively high, spinning and drawability will be poor, and therefore it is preferably 200,000 poise or less.

The thermoplastic resin of the sheath component has a melt viscosity of 3500 poise or more at 290 ° C. and 20 sec ⁻¹ , and it is preferably 200,000 poise or less from the viewpoint of spinnability and drawability like the core component. Further, in the present invention, the sheath component preferably increases the extensional viscosity in order to suppress foaming of the core component, and is preferably a branched polymer containing a compound having three or more functional groups in the main chain. When the sheath component is polyester, examples of such a compound include trimellitic acid, trimesic acid, pyromellitic acid, triethylene glycol, tetraethylene glycol and esterified products thereof, and epoxies. It is difficult to accurately measure the extensional viscosity of the molten resin at this stage, so the extensional viscosity cannot be specified as a numerical value.
Is a preferred condition for suppressing foaming that the ratio η _L / η _H melt viscosity eta _H in melt viscosity eta _L and 2000 sec ^-1 at 20sec ^-1 is 2 or more at 290 ° C. with respect to the melt viscosity .

The magnitude relationship between the melt viscosities of the core component and the sheath component is not particularly specified, but the viscosity of the core component is reduced due to the viscosity-reducing effect of adding carbon dioxide and / or nitrogen, and It is preferable that the core component has a higher melt viscosity at 290 ° C. and 20 sec ⁻¹ than the sheath component, because the composite abnormality and the core-sheath may be reversed when spinning is performed.

In the present invention, the substance added to the crystalline thermoplastic resin as the core component is selected from nitrogen and carbon dioxide because it does not react with the resin serving as the substrate and has a low environmental load. It is possible to use any of these or two at the same time, but it is preferable to use carbon dioxide from the viewpoint of the effect.

The method of adding nitrogen or carbon dioxide to the resin is not particularly limited, and for example, nitrogen and / or carbon dioxide gas is introduced under pressure into the bunker of the polymer chip before melting, or melting is performed. Known methods such as injecting nitrogen and / or carbon dioxide (regardless of gas or liquid) into the resin are adopted. However, the method of injecting nitrogen and / or carbon dioxide into the resin melted by the extruder is preferable from the viewpoint that the apparatus is not modified so much.

The amount of nitrogen or carbon dioxide added is 0.3 to 6
% By weight. If the amount added is smaller than this, the effect is not seen, and if the amount added is larger, foaming becomes more severe and the spinnability deteriorates.
The preferred addition amount is 1 to 4% by weight for carbon dioxide and 0.5 to 1% by weight for nitrogen. The addition amount in the present invention is a value obtained by the method described in the examples.

The core-sheath type composite spinning in the present invention is not particularly limited in the composite form as long as the core component is not exposed on the surface, and any form such as a multiple core-sheath type or a sea-island type is possible. A concentric type having one core and one sheath is preferable for simplifying the device.

The ratio of the core and sheath components is also optional, but in order to efficiently utilize the plasticizing effect of nitrogen and carbon dioxide in the core component, the core component is 75% by weight of the total discharge amount.
The above is preferable.

The means for making the discharged resin into fibers is not particularly limited, and the atmosphere control in the vicinity of the mouthpiece by a heating tube or a heat retention tube, cooling with a fluid such as rectified air, application of a finishing agent, etc. It is optional. However, from the viewpoint of suppressing foaming, it is desirable that the resin after discharge be cooled promptly. Since the cooling rate in the melt spinning process changes depending on the yarn speed on the spinning line,
The cooling rate is not particularly limited, but a cooling rate at which solidification is completed within 2 seconds after discharging is preferable.

Regarding the take-back method, it can be taken by any method such as a roller or an air aspirator.
The spinning speed is also not particularly limited, but the spinning speed is preferably 3000 m / min or less in order to enhance the mechanical properties of the fiber.

The drawing may be carried out by a two-step method or may be carried out by direct spinning. However, in order to reduce the production cost and prevent the spun fiber from changing with time, it is taken up and then wound up once. It is preferable to continuously perform stretching and heat treatment without performing the heat treatment.

The thermoplastic synthetic fibers obtained by the production method of the present invention can be used in various forms such as short fibers, long fibers and nonwoven fabrics. Further, from the viewpoint of improving mechanical properties, it can be suitably used for applications such as rubber reinforcing materials, construction civil engineering, medical hygiene, and environmental safety.

[0033]

EXAMPLES The present invention will be described specifically and in more detail with reference to the following examples. However, the present invention is not limited to the following examples. The physical property values in the examples were measured by the following methods.

A. 290 ° C., was measured at a shear rate range near 20sec ^-1 and 2000 sec ^-1 using a melt viscosity Toyo Seiki Capillograph type 1 at 20sec ^-1 and 2000sec ^-1, 20sec ^-1 and 2000 sec ^-1 by approximation The melt viscosity of was determined.

B. Amount of Nitrogen or Carbon Dioxide The amount of nitrogen or carbon dioxide discharged was measured using a Coriolis flowmeter Micro Motion Elite type manufactured by Fisher-Rosemount. The amount of resin discharged is obtained by discharging the resin added with nitrogen or carbon dioxide, receiving it in a water tank, quenching it, and air-drying it for 24 hours in the atmosphere. From the above, the amount added to the resin was calculated using the following formula.

[0036]

[Equation 1] C. Strength / Elongation Using a Tensilon tensile tester manufactured by Orientec, the initial sample length was 200 mm and the tensile speed was 200 mm / min.

Examples 1 to 4 and Comparative Example 1 290 ℃, 20sec^-1Polyethylene with a melt viscosity of 10,000 poise at
Melt ethylene terephthalate in a twin-screw extruder
Then, add carbon dioxide from the inlet provided in the middle of the cylinder.
The added component is the core component, and the epoxy compound (Nagase
0.5% by weight of "Denacol EX-203" manufactured by Kasei Kogyo Co., Ltd.
Then, by adjusting the degree of polymerization, 290 ℃, 20sec ^-1Melting in
Viscosity 7200poise, 2000sec^-1Melt viscosity at 2300 poise
And the polyethylene terephthalate composition as a sheath component
Spinning temperature 295 ℃, total resin discharge 57.1g / min (core: sheath ratio
Ratio = 80:20) and the core-sheath composite spinning is performed using a spinneret with 48 holes.
It was. The amount of carbon dioxide added is 0 (ratio
Comparative Example 1), 0.5 (Example 1), 2 (Example 2), 4 (Example)
3) and 6 (Example 4) were set to weight%. This is a roller at room temperature
, And take it at a speed of 1000 m / min for 90 consecutive
Two-stage drawing and stretching using a heating roller at ℃, 140 ℃, 220 ℃
And heat treatment was performed. The total draw ratio is the elongation of the fiber after drawing
Adjusted to be about 12%. The pressure release rate under each condition
Table 1 shows the total draw ratio of Rabi. Increased carbon dioxide addition
With the addition, the total draw ratio is improved and the drawability is improved.
I understand.

The physical properties of the fibers thus obtained are also shown in Table 1. As can be seen from Table 1, the addition amount is 0% by weight (Comparative Example 1).
It can be seen that the addition of carbon dioxide increases the total draw ratio, and the strength increases accordingly.
However, in the case of the addition amount of 6% by weight, single yarn winding around the roller was observed once during the yarn making. Therefore, if the addition amount is larger than this, the spinnability may be deteriorated.

[0039]

[Table 1] Example 5 Polyethylene terephthalate having a melt viscosity of 24000 poise at 290 ° C. and 20 sec ⁻¹ was melted in a twin-screw extruder, and carbon dioxide was supplied from an injection port provided in the middle of the cylinder to remove carbon dioxide.
What was added so as to be the weight% is the core component, 290 ° C, 20 seconds
Melt viscosity at ^-1 12000Poise, as polyethylene terephthalate sheath component melt viscosity of 6000poise at 2000 sec ^-1, a spinning temperature of 295 ° C., the resin total discharge rate 43.8 g / min
Core-sheath composite spinning was performed using a spinneret with 48 holes at a (core: sheath ratio = 85: 15). 500m / min using a roller at room temperature
Was taken out at a speed of 10 ° C., and this was subjected to two-stage drawing and heat treatment at a drawing speed of 200 m / min using a heating roller of 90 ° C., 140 ° C. and 220 ° C. The total draw ratio is about 12% elongation of the drawn fiber
When adjusted to be 5.10 times, the strength is 10.1 cN / d
High strength fibers of tex were obtained (Table 2).

Example 6 Polyethylene terephthalate having a melt viscosity of 5100 poise at 290 ° C. and 20 sec ⁻¹ was melted in a twin-screw extruder, and nitrogen was added so that the concentration of nitrogen became 0.4% by weight from an injection port provided in the middle of the cylinder. Is a core component, and 0.3 wt% of an esterified product of trimellitic acid is added at the time of polymerization to adjust the degree of polymerization to obtain a melt viscosity of 3600 pois at 290 ° C and 20 sec ^-1.
e, a polyethylene terephthalate composition having a melt viscosity of 1200 poise at 2000 sec ^-1 as a sheath component, and a spinning temperature of 29
Core-sheath composite spinning was performed using a spinneret having 48 holes at 5 ° C. and a total resin discharge rate of 89.0 g / min (core: sheath ratio = 75: 25). This was taken out at a speed of 3000 m / min using a roller at room temperature, and continuously subjected to two-stage drawing and heat treatment using heating rollers at 90 ° C, 140 ° C and 230 ° C. The total draw ratio was 2.75 times when the elongation of the drawn fiber was adjusted to about 12%.
Fibers with strength of 8.0cN / dtex with improved mechanical properties were obtained.
(Table 2).

[0041]

[Table 2]

[0042]

INDUSTRIAL APPLICABILITY The thermoplastic synthetic fiber obtained by the production method of the present invention has improved mechanical properties as compared with the fiber obtained by the conventional method and can be suitably used for various purposes. Furthermore, by improving the mechanical properties, stable manufacturing is possible with few process abnormalities such as single yarn breakage during yarn manufacturing. In addition, since nitrogen or carbon dioxide is used, the environmental load of substances discharged in the manufacturing process is reduced.

Continued front page    F-term (reference) 4L041 AA08 AA10 AA15 AA20 BA02                       BA05 BA21 BC20 CA06 CA61                       DD01 DD04 DD21

Claims (6)

[Claims] 1. Melt viscosity at 290 ° C. and 20 sec ⁻¹ is 5000 poise.
Carbon dioxide and / or nitrogen is added to the above crystalline thermoplastic resin in an amount of 0.3 to 6% by weight, and the thermoplastic resin mixture melt-mixed is used as a core component, and the melt viscosity at 290 ° C, 20 sec ^-1 is 3500 poise or more. A method for producing a thermoplastic synthetic fiber, which comprises performing core-sheath type composite spinning using a thermoplastic resin as a sheath component. 2. The method for producing a thermoplastic synthetic fiber according to claim 1, wherein the core component accounts for 75% by weight or more of the total discharge amount. 3. The method for producing a thermoplastic synthetic fiber according to claim 1, wherein the crystalline thermoplastic resin of the core component is polyester. 4. The thermoplastic synthetic fiber according to claim 1, wherein the thermoplastic resin of the sheath component is a branched polymer containing a compound having three or more functional groups in its main chain. Manufacturing method. 5. The method for producing a thermoplastic synthetic fiber according to claim 1, wherein the discharged resin is collected at a speed of 3000 m / min or less. 6. The method for producing a thermoplastic synthetic fiber according to claim 5, wherein after being taken up, the thermoplastic synthetic fiber is continuously stretched and heat-treated without once being taken up.