JP2003129342A - Method for producing foamed fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a foamed fiber improved in mechanical characteristics, excellent in fiber-forming properties and giving little load to the environment. SOLUTION: This method for producing the foamed fiber is to carry out a bi-component fiber spinning by using a thermoplastic resin mixture (A) prepared by adding 0.5-6 wt.% carbon dioxide and/or nitrogen to the thermoplastic resin and melting and mixing the same and a thermoplastic resin mixture (B) prepared by adding <0.5 wt.% carbon dioxide and/or nitrogen to the thermoplastic resin and meeting and mixing the same.

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 expanded fibers, and more particularly to a method for producing expanded fibers having improved mechanical properties, which is excellent in yarn formability and has a low environmental load.

[0002]

2. Description of the Related Art Expanded fibers, that is, filaments or staple fibers containing discontinuous porosity, are lightweight because of their low density, and have excellent heat retention due to their porosity, so they are suitable for carpets and cotton wool. It is preferably used not only for linings for winter clothes and winter clothing but also for clothing.

As a foaming technique for synthetic fibers typified by polyester, for example, sodium carbonate, citric acid, and polycarbonate are added as disclosed in JP-A-4-214407. However, according to this method, although foaming is certainly performed, the mechanical properties of the obtained fiber are insufficient, and the stain in the vicinity of the die hole is severe, and the spinnability is not satisfactory. In addition, since sodium carbonate, citric acid, and polycarbonate used in the technique are basically different from the thermoplastic resin that forms the synthetic fiber, there is a problem that environmental impact is concerned because the recyclability is impaired. there were.

On the other hand, in the field of foam molding, many techniques for adding carbon dioxide or the like to a molten polymer are known. However, the addition of polyester or polyamide in the melt spinning is only slightly seen in JP-A No. 11-172528, and the publication only mentions the elongation improving effect by the addition of carbon dioxide, It does not give any suggestion as to the technology for producing foamed fibers.

[0005]

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 method for producing a foamed fiber having improved mechanical properties, which is excellent in the spinnability and has a low environmental load. To do.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies on the addition / mixing technology and the foaming technology in the melt spinning of carbon dioxide and nitrogen, and the improvement of the mechanical properties of the obtained fiber. Among them, the inventors have found that the drawbacks of the prior art can be solved by carrying out composite spinning using a component satisfying a certain fixed amount of carbon dioxide or nitrogen, and arrived at the present invention.

That is, the present invention adds 0.5 to 6% by weight of carbon dioxide and / or nitrogen to a thermoplastic resin and melt-mixes the thermoplastic resin mixture (A) and the thermoplastic resin with carbon dioxide and / or nitrogen. Add less than 0.5% by weight,
The present invention provides a method for producing a foamed fiber, which comprises performing a composite spinning using two resin mixtures of a melt-mixed thermoplastic resin mixture (B).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The requirement of the present invention is to add 0.5 to 6% by weight of carbon dioxide and / or nitrogen and melt-mix the thermoplastic resin mixture (A) with less than 0.5% by weight of carbon dioxide and / or nitrogen. It is to perform composite spinning using two resin mixtures of the thermoplastic resin mixture (B) added and melt-mixed. By performing melt spinning under such conditions, it is possible to produce expanded fibers having improved mechanical properties with a low load on the environment. The reason will be described below.

The technique of adding carbon dioxide or nitrogen to a molten resin and mixing it with each other to foam is known, and the present inventors have also examined the application to melt spinning. However, in melt spinning, problems such as poor spinnability due to contamination of the spinneret and deterioration of spinnability and deterioration of mechanical properties of the obtained fiber have been found. Therefore, the present inventors have conducted an analysis on the behavior in the spinning line, and have found that foaming in the vicinity of the spinneret discharge hole is a factor of deteriorating the spinnability. However, when the foaming itself is suppressed, the contradictory problem that the target foamed fiber cannot be obtained has arrived.

Therefore, the present inventors have found that the above-mentioned problems can be solved by carrying out the composite spinning using the component (B) which is responsible for the spinnability and mechanical properties and the component (A) which mainly causes foaming. It was.

The "foamed fiber" referred to in the present invention is a fiber containing discontinuous pores, and specifically, a plurality of fibers in the cross section of the fiber,
A fiber having 10 or more pores is preferable. The number of pores and the pore diameter are not particularly limited because they depend on the viscosity of the resin and the spinning conditions, but the specific gravity, which is a measure of the total amount of pores, was obtained under the same spinning conditions without adding nitrogen and / or carbon dioxide. It is preferably smaller than the fiber by 3% or more.

The thermoplastic resin used as the components (A) and (B) 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. , 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 resins of the components (A) and (B) may be different, but the compositions (excluding the molecular weight, additives, copolymerization components, etc.) are preferably the same in order to simplify the resin used and the manufacturing process. .

Although the degree of polymerization of the resin is arbitrary, the melt viscosity of the resin, which is a measure of the degree of polymerization, is 290 ° C. for 20 seconds in order to sufficiently expand the foam while suppressing yarn breakage due to foam breaking.
^-1 is preferably 1000 to 5000 poise.

Furthermore, in order to reduce the foaming diameter of the resins of the components (A) and (B), 0.5% of a foaming nucleating agent such as polystyrene is used.
About 2% may be added. However, in order to make the resin composition uniform, it is preferable to increase the extensional viscosity of the resin, and it is preferable to use a branched polymer containing a compound having three or more functional groups in its main chain. When the resin is a polyester, examples of such a compound include trimellitic acid, trimesic acid, pyromellitic acid, triethylene glycol, tetraethylene glycol and esterified products thereof, and epoxies.

The substance to be added to the thermoplastic resin in the present invention 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 and / or carbon dioxide to the resin is not particularly limited. For example, nitrogen and / or carbon dioxide gas is introduced into the bunker of the polymer chip before melting under pressure. Alternatively, nitrogen and / or carbon dioxide (gas,
A known method of injecting a liquid (regardless of liquid) is 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 and / or carbon dioxide added is 0.5 to 6% by weight for the component (A) which mainly causes foaming. 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 for nitrogen.
It is 0.5 to 1% by weight. The addition amount in the present invention is a value obtained by the method described in the examples.

A component (B) which is responsible for spinnability and mechanical properties
The amount of nitrogen and / or carbon dioxide added is 0.5% by weight
Is less than. If the amount added is larger than this, the spinnability and the mechanical properties of the resulting fiber deteriorate due to foaming.

The form of the composite spinning carried out in the present invention depends on the components
There is no particular limitation as long as both (A) and (B) are continuously present in the longitudinal direction of the fiber, and any form can be adopted according to the purpose. For example, the component (A) may be a sheath, a component ( When the core-sheath composite spinning with B) as the core is carried out, fibers having pores on the surface and excellent in moisture absorption / release are obtained, and when the side-by-side composite spinning of the component (A) and the component (B) is carried out, only one side is obtained. A fiber having pores in the fiber is obtained. In order to improve the spinnability, it is preferable that the surface does not foam, and the component (A) is the core and the component (B) is the core.
Is preferably used as the sheath.

The ratio of the component (A) to the component (B) is also optional, but in order to improve the mechanical properties of the obtained fiber, the component (B)
Is preferably 40% by weight or more of the total discharge amount.

The means for making the discharged resin into fibers is not particularly limited, and atmosphere control around the mouthpiece by a heating cylinder or a heat insulation cylinder, cooling with a fluid such as rectified air, application of a finishing agent, etc. It is optional. However, from the viewpoint of suppressing foaming in the vicinity of the spinneret hole, it is desirable that the resin after discharge is rapidly cooled, and the melt spinning conditions are such that the discharge linear velocity in each hole is 10 cm / sec or more, and
The cooling rate is preferably such that the solidification is completed within seconds.

Regarding the take-back method, it can be taken by any method such as a roller or an air aspirator.
Although the spinning speed is not particularly limited, high-speed spinning in which the deformation is completed on the spinning line to maintain the shape of the pores is a preferred embodiment. When the resin is polyester, the spinning speed is preferably 5000 m / min or more, although it depends on the molecular weight.

[0023]

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, the melt viscosity of 20sec ^-1 and 2000 sec ^-1 by approximation I asked. B. Amount of Nitrogen or Carbon Dioxide The amount of nitrogen and / or carbon dioxide discharged was measured using a Coriolis flowmeter Micro Motion Elite type manufactured by Fisher-Rosemount. The discharge amount of the resin is obtained by discharging the resin added with nitrogen and / or carbon dioxide, receiving it in a water tank, quenching it, and air-drying it in the atmosphere for 24 hours. The amount added to the resin was calculated from the carbon discharge amount using the following formula.

[0024]

[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. D. Specific gravity It was measured using an electronic hydrometer SD-120L manufactured by Mirage Trading Co., Ltd. Examples 1 to 4 and Comparative Example 1 Polyethylene terephthalate having a melt viscosity of 2600 poise at 290 ° C. and 20 sec ⁻¹ was melted with a twin-screw extruder, and carbon dioxide was added from an injection port provided in the middle of the cylinder as a component. (A), a polyethylene terephthalate composition having a melt viscosity of 2000 poise at 290 ° C. and 20 sec ⁻¹ of 2000 poise by adding 0.2% by weight of an esterified product of trimellitic acid during the polymerization (B) As the core-sheath composite spinning, the component (A) was used as the core and the component (B) was used as the sheath. The spinning temperature is 295 ℃, and the total resin discharge rate is 47.3g / min.
(Core: sheath ratio = 5: 5), a die having 36 holes was used, and it was collected at a speed of 3000 m / min using a roller at room temperature.
The amount of carbon dioxide added was 0 (Comparative Example 1), 0.5 (Example 1), 2 (Example 2), 4 (Example 3), 6 with respect to the amount of component (A) discharged.
(Example 4) Weight% was used. This was stretched at a speed of 600 m / min using a heating roller at 90 ° C and 140 ° C. The draw ratio was adjusted so that the elongation of the drawn fiber would be about 35%. The spinnability was generally good under each condition, but when the addition amount was 6%
In Example 4, dirt is attached to the spinneret surface after the completion of spinning, and if the amount of addition is larger than this, there is a concern that the spinnability will deteriorate.

Table 1 shows the yarn making conditions and the drawn yarn physical properties.
In addition, the specific gravity of the drawn yarn decreases with an increase in the addition amount, so that Example 1 is compared with Comparative Example 1 in which carbon dioxide is not added.
Is 3.06%, Example 2 is 8.5%, Example 3 is 17.5%, and Example 4 is 26.2%, indicating that foamed fibers are obtained.

[0026]

[Table 1] Comparative Example 2 Spinning and drawing were performed in the same manner as in Example 2 except that 2% of carbon dioxide was added to the component (B) on the sheath side. However, the spinnability was poor, and only a small amount of drawn yarn was obtained.
Table 2 also shows the yarn making conditions and the drawn yarn physical properties. component
Compared with Example 2 in which carbon dioxide was not added to (B), the specific gravity was reduced, but at the same draw ratio the strength
It can be seen that the elongation has dropped significantly.

Example 5 Polyethylene terephthalate having a melt viscosity of 2200 poise at 290 ° C. and 20 sec ^-1 was mixed with 1% of polystyrene (Stylon 685 manufactured by Asahi Kasei Corporation), which was melted by a twin-screw extruder and provided in the middle of the cylinder. Carbon dioxide added from the injection port to 2% by weight was added as component (A), 290
Polyethylene terephthalate having a melt viscosity of 2000 poise at 20 ° C. and 20 sec ⁻¹ is used as the component (B), the component (A) is the sheath, and the component is
Core-sheath composite spinning with (B) as the core was performed. The spinning temperature is
290 ℃, total resin discharge rate is 48.8g / min (core: sheath ratio = 6: 4)
And using a die with 36 holes and a roller at room temperature
It was collected at a speed of 6500 m / min. The spinnability is generally good, and the physical properties of the obtained fiber (Table 2) also have sufficient specific gravity and mechanical properties.

Example 6 Polyethylene terephthalate having a melt viscosity of 3300 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. Component (A), an epoxy compound (“Denacol EX-203” manufactured by Nagase Kasei Co., Ltd.) during polymerization
By adding 0.3% by weight and adjusting the degree of polymerization, 290 ℃, 20
A polyethylene terephthalate composition having a melt viscosity at sec ^-1 of 2700 poise was melted by a twin-screw extruder, and nitrogen was added so as to be 0.2% by weight from an injection port provided in the middle of the cylinder as a component (B) as a side by side. The mold was subjected to composite spinning. The spinning temperature was 295 ° C, the total resin discharge rate was 28.5 g / min (A: B ratio = 5: 5), and the number of holes was 3
After using the die of No. 6 and taking it off at a speed of 1000 m / min using a roller at room temperature, drawing and heat treatment were continuously performed using a heating roller at 80 ° C and 150 ° C. The spinnability is generally good, and the physical properties of the obtained fiber (Table 2) also have sufficient specific gravity and mechanical properties.

[0029]

[Table 2]

[0030]

The foamed fiber obtained by the production method of the present invention has improved mechanical properties and can be suitably used for various purposes.
Further, by performing composite spinning, the spinnability is improved and stable yarn production is possible. In addition, since nitrogen and / or carbon dioxide are used, the environmental load of the foaming agent is reduced.

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Claims (4)

[Claims] 1. A thermoplastic resin mixture (A) obtained by adding 0.5 to 6% by weight of carbon dioxide and / or nitrogen to a thermoplastic resin and melt-mixing it, and 0.5% by weight of carbon dioxide and / or nitrogen to the thermoplastic resin. A method for producing a foamed fiber in which composite spinning is performed using two resin mixtures of a thermoplastic resin mixture (B) added by less than the above and melt-mixed. 2. The method for producing a foamed fiber according to claim 1, wherein the thermoplastic resin is polyester. 3. The method for producing a foamed fiber according to claim 1, wherein the spinning speed is 5000 m / min or more. 4. The method for producing a foamed fiber according to claim 1, wherein the thermoplastic resin is a branched polymer having a main chain of a compound having three or more functional groups. .