JP2006070419A - Flame-retardant recycled polyester fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant recycled polyester fiber having excellent whiteness with slight dispersion of values of physical properties even when a recycled polyester is used, hardly causing a dyeing speck even when formed into a fabric and dyed, having excellent flame retardance and suitably usable for various applications. <P>SOLUTION: The flame-retardant recycled polyester fiber comprises the recycled polyester containing a polyester prepared by repolymerizing an oligomer obtained by depolymerizing the recycled polyester as at least one component. A phosphorus compound is contained in the fiber and the content of the phosphorus atom is 2,000-30,000 ppm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is a fiber comprising at least one recycled polyester containing a polyester obtained by depolymerizing and re-polymerizing a polyester recovered after use (hereinafter referred to as recycled polyester), and containing a phosphorus compound. The present invention relates to a flame retardant recycled polyester fiber that is excellent in flame retardancy.

  Polyesters such as polyethylene terephthalate (PET) have a high melting point, chemical resistance, and low cost. Therefore, they are widely used not only for fibers but also for film molded products.

  These polyester products are disposed of after use, but when they are burned, there is a problem that high heat is generated, the incinerator is severely damaged, and the life of the incinerator is shortened. In addition, when not incinerated, it does not decompose and remains semipermanently, which is also an environmental problem.

  Recycling has been attempted in various fields and materials from the viewpoint of resource reuse and environmental issues. Even for polyesters that are used in large quantities and are expected to increase significantly in the future, recovering and reusing polyester once used in PET bottles for liquid drinks is a resource reuse. It contributes and is important as part of corporate activities that are friendly to the global environment. As one of products using such recycled polyester, there are polyester filaments, and these filaments are used for clothing or industrial materials.

  Since recycled polyester is processed into various products and collected after being used, recycled polyester fiber obtained from recycled polyester is likely to be colored or discolored. In addition, recycled polyester has large variations in physical properties such as melt viscosity, molecular weight, crystallinity, etc., and physical properties between lots are not very stable. When the filament and the fabric obtained from the filament are dyed, there is a problem that a color spot is generated in the product or a color difference is generated between packing units.

  Therefore, it has been proposed to use not only recycled polyester but also unused polyester (hereinafter referred to as virgin polyester) obtained by a usual polymerization method and recycled polyester.

  One of them is a filament obtained by mixing both polyesters. For example, mixed filaments obtained by mixing virgin polyester and recycled polyester at the chip stage before melting and melt spinning, or kneading virgin polyester and recycled polyester separately melt extruded in a nozzle pack (Multifilament) has been proposed.

  However, in this mixed filament, since the characteristics of the recycled polyester are not changed, the problems that the quality of the recycled polyester portion fluctuates and color spots such as stained spots are not fully solved. Therefore, the core-sheath structure as described in Patent Document 1 is used, and it is attempted to solve the problem of coloring and color spots by preventing the recycled polyester from being exposed to the fiber surface. Since polyester cannot be used on the fiber surface, the form of the fiber is limited, and the proportion of recycled polyester cannot be increased.

  Also, as described in Patent Documents 2 and 3, after recycling the recycled polyester, it is recovered as raw materials terephthalic acid and bis-β-hydroxyethyl terephthalate by chemical recycling that performs various treatments and reactions. A method has been proposed. According to this method, a high-purity raw material can be obtained. Therefore, a polyester obtained by performing a normal polymerization method using this raw material also has excellent quality and physical properties. However, there is a problem that it is very expensive.

  On the other hand, with the diversification of consumer needs, not only low environmental impact but also products with functionality are desired from many perspectives, and fiber products with functionality added to recycled polyester fibers. Offering meets the needs of consumers.

  Above all, interest in flame retardancy is increasing year by year due to improvement of consumers' awareness of disaster prevention or strengthening of laws and regulations, especially curtains and transportation used in public facilities such as hospitals, inns, welfare facilities, theaters etc. For textile products such as chair upholstery used in institutions, it has become essential to use flame retardant fibers as a disaster prevention measure.

  Therefore, a method in which recycled polyester and flame-retardant polyester are mixed at the tip stage before melting, a method in which raw materials that have been melt-kneaded and then chipped are used, or melt extrusion is performed separately during melt spinning, A filament by a kneading method has been proposed (see, for example, Patent Document 4).

However, the mixed filaments spun by this method exhibit flame retardancy, but the characteristics of the recycled polyester remain the same as described above, so the quality of the recycled polyester varies, and color spots such as stained spots change. The problem that occurred was not able to be solved sufficiently.
JP 2000-328369 A JP 2002-060369 A JP 2002-060543 JP JP 2002-54026 A

  The present invention solves the above-mentioned problems, can be obtained by inexpensive means, has excellent whiteness even when recycled polyester is used, has little variation in physical property values, and is used as a fabric for dyeing. In particular, it is an object of the present invention to provide a flame-retarded recycled polyester fiber that is less likely to cause dyeing spots and is excellent in flame retardancy and can be suitably used for various applications.

  As a result of intensive studies to solve the above problems, the present inventors have depolymerized the recycled polyester to obtain a low molecular weight material, and repolymerized it, so that there is a variation in coloring and performance of the recycled polyester. The present inventors have found that flame retardancy can be imparted to the regenerated polyester by adding a phosphorus compound when this low molecular weight substance is repolymerized.

  That is, the present invention is a fiber comprising at least one recycled polyester containing a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester, and the fiber contains a phosphorus compound. Further, the present invention provides a flame retardant recycled polyester fiber characterized in that the phosphorus atom content is 2000 to 30000 ppm.

  Since the flame-retarded recycled polyester fiber of the present invention uses a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester, it has excellent whiteness, little variation in physical properties, and a fabric. When dyeing is performed, dyeing spots hardly occur and the flame retardancy is excellent, and it can be suitably used for various uses including clothing.

  Furthermore, the flame retardant recycled polyester fiber of the present invention containing an organic fluorescent whitening agent in the fiber has excellent stain resistance and light resistance in addition to the above effects, and is suitable for interior use and the like. Can be used.

Hereinafter, the present invention will be described in detail.
The recycled polyester fiber of the present invention uses recycled polyester as a raw material, and the recycled polyester is formed into a shape other than pellets such as PET bottles, films and fibers for liquid food and drink, and then returned to a low molecular weight. This refers to the resin recovered for re-molding. Of these, those obtained by collecting PET bottles are preferred because of their relatively good quality.

  The fiber of the present invention is a fiber comprising at least one recycled polyester containing a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester. That is, the recycled polyester is depolymerized to lower the molecular weight, but it is preferable to contain a polyester obtained by subsequent repolymerization of the low molecular weight polymer without depolymerizing it until it becomes a monomer. Such polyester constituting the present invention will be described.

  First, at the time of depolymerization, the polymer is made to have a low molecular weight by adding a glycol component to the recycled polyester, and the resulting low molecular weight substance is subsequently repolymerized in the low molecular weight state. Examples of the repolymerization include melt polymerization and solid-phase polymerization as in the usual polymerization method, and a polymer (polyester) is obtained by repolymerizing a depolymerized low molecular weight polymer.

  In this way, recycled polyester is once decomposed into low molecular weight substances by depolymerization, and polyester obtained by repolymerizing this low molecular weight substance is used. Therefore, as in the past, recycled polyester was only melted and reused. Unlike polyester fibers, physical properties such as melt viscosity, molecular weight and crystallinity are made uniform and stabilized, and the color tone is improved.

  In addition, unlike chemical recycling, the low molecular weight product obtained by depolymerization is not further purified and recovered as a monomer, which is advantageous in terms of cost.

In the present invention, the low molecular weight product depolymerized to lower the molecular weight preferably has a molecular weight (number average molecular weight) of about 1000 to 4000. If the molecular weight exceeds 4,000, depolymerization is not sufficient, and the above-described effects of uniforming and stabilizing the physical property values and improving the color tone are insufficient. On the other hand, making the molecular weight less than 1000 is disadvantageous in terms of cost.
In order to obtain a low molecular weight body having a molecular weight as described above, it is possible to adjust the amount of the glycol component added to the recycled polyester, the reaction temperature, the pressure, and the like.

  And it is preferable that the content of the component derived from recycle polyester is 30 mass% or more of the recycled polyester fiber of this invention of the whole fiber. That is, in the present invention, a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester is used, but the amount of recycled polyester used in this way is 30% by mass or more of the total fiber. It is preferable that

  In the recycled polyester fiber of the present invention, from the viewpoint of contributing to global environmental conservation, it is preferable to contain as much recycled polyester as possible, so the content of components derived from recycled polyester is 30% by mass or more, especially 40% by mass, It is preferable to be 60% by mass or more. In addition, it is preferable that content of the component derived from recycled polyester shall be 90 mass% or less. If it exceeds 90% by mass, the uniformity and color tone of the physical properties of the resulting fiber tend to decrease.

  When repolymerization is performed using only the low molecular weight material obtained by depolymerization of the recycled polyester, a 100% component polyester (hereinafter referred to as polyester M) derived from the recycled polyester can be obtained. In order to make the content of the component derived from the recycled polyester 30 to 90% by mass, the polyester (polyester M) of 100% of the component derived from the recycled polyester obtained by depolymerizing and repolymerizing only the recycled polyester (polyester M) was obtained. Polyester blended with polyester may be used, but after depolymerizing recycled polyester, virgin polyester oligomer is added at the time of repolymerization, and the low molecular weight depolymerized recycled polyester and virgin polyester monomer are repolymerized. Polyester (hereinafter referred to as polyester N) may be used. In order to make the various physical property values of the polyester more uniform and stable, it is preferable to use a polyester (polyester N) obtained by addition and repolymerization during the latter repolymerization.

That is, the recycled polyester constituting the fiber of the present invention contains a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester, and examples thereof include the following embodiments. . Moreover, you may blend and use multiple types of the reproduction | regeneration polyester of (a)-(d).
(A) Regenerated polyester consisting only of polyester M.
(B) Regenerated polyester obtained by blending polyester M with virgin polyester.
(C) Regenerated polyester consisting only of polyester N.
(D) Regenerated polyester obtained by blending polyester N and virgin polyester.

  In the recycled polyester fiber of the present invention, it is possible to use various polyesters for both recycled polyester and virgin polyester, but it is preferable that both are of the same type, and the recycled polyester is derived from a PET bottle as described above. Therefore, virgin polyester is also preferably PET.

  The regenerated polyester of the present invention may contain a copolymer component as long as the effects of the present invention are not impaired. Examples of copolymer components include aromatic dicarboxylic acids such as 3,3′-diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, aliphatics such as diethylene glycol, 1,4-butanediol, and 1,4-cyclohexanediol. Examples thereof include alicyclic diols and P-hydroxybenzoic acid. These may be contained in either recycled polyester or virgin polyester, and may be added at the time of repolymerization.

  And the regenerated polyester fiber of this invention is a fiber which uses the regenerated polyester of the above aspects (a)-(d) as at least one component. That is, it may be either a fiber (single type) made only of regenerated polyester or a composite fiber (composite type) made of a regenerated polyester and a thermoplastic resin other than regenerated polyester or virgin polyester.

  In the case of a composite type fiber, examples of the composite shape include a core-sheath type, a side-by-side type bonded type, and a sea-island type. Further, as the other thermoplastic resin, any of polyamide, polyolefin and the like may be used. These composite forms and other thermoplastic resins may be appropriately selected according to the use and purpose.

  Furthermore, the regenerated polyester fiber of the present invention contains a phosphorus compound in the fiber, and the content of phosphorus atoms in the fiber is 2000 to 30000 ppm. By containing a phosphorus compound in the fiber, the fiber can be made excellent in flame retardancy.

  If the phosphorus atom content is less than 2000 ppm, the flame retardancy is reduced. On the other hand, if it exceeds 30000 ppm, it is necessary to increase the amount of the compound containing a phosphorus atom. As a result, the melting point of the polymer is remarkably lowered, and not only spinning but also fiber strength is unfavorable.

  Examples of phosphorus compounds include phosphate esters and derivatives thereof, phosphonic acids and derivatives thereof, phosphinic acids and derivatives thereof, and these can be used alone or in combination of two or more. Specific examples of phosphate esters and derivatives thereof include trimethyl phosphate, triethyl phosphate, and tripropyl phosphate. Specific examples of phosphonic acid and derivatives thereof include phenylphosphonic acid, dimethylphosphonic acid, diethylphosphonic acid, and diethylphosphonic acid. Specific examples of phosphinic acid and derivatives thereof include phosphorane, a maleic acid adduct of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, an itaconic acid adduct, and the like. . There are also compounds obtained by adding ethylene carbonate to a reaction product of diphenylphosphine oxide and p-benzoquinone.

  Such a phosphorus compound is contained in the regenerated polyester when the regenerated polyester fiber of the present invention is a single type, and when the regenerated polyester fiber of the present invention is a composite type, the regenerated polyester, regenerated Although it may be contained in any component other than polyester, it is preferably contained in regenerated polyester.

  In the present invention, the recycled polyester is depolymerized to form a low molecular weight substance, which is repolymerized and used. Therefore, by adding a phosphorus compound when repolymerizing the low molecular weight substance, the phosphorus compound is added. It can be polymerized, and flame retardancy can be imparted to the recycled polyester. On the other hand, with recycled polyester that only melts PET bottle scraps and the like, even if a phosphorus compound is added at the time of melting, the molecular weight of the recycled polyester is significantly reduced and cannot be uniformly added. It cannot be polymerized and flame retardancy cannot be imparted to the recycled polyester.

  Therefore, as a method for incorporating the phosphorus compound into the regenerated polyester, it is preferable to repolymerize by adding the phosphorus compound as described above when repolymerizing the low molecular weight material obtained by depolymerizing the recycled polyester.

  Further, as the flame retardancy performance of the recycled polyester fiber of the present invention, it is preferable that the limiting oxygen index (LOI) measured in accordance with JIS K 7201-2 in a state where the fiber is knitted is 27 or more, It is preferable that it is 28 or more.

  Furthermore, the regenerated polyester fiber of the present invention preferably contains 0.02 to 1.0% by mass of an organic fluorescent whitening agent in order to impart stain resistance and to reduce coloring by a phosphorus compound. Examples of organic fluorescent brighteners include pyrene, oxazole, coumarin, thiazole, imidazole, imidazolone, pyrazole, diaminocarbazole, naphthal, and diaminostilbene disulfonic acid fluorescent whitening pigments and organic fluorescent brighteners. White dyes are preferred. Of these, oxazole fluorescent whitening pigments having excellent heat resistance are preferred.

  The content of the organic fluorescent brightener is preferably 0.02 to 1.0% by mass with respect to the fiber mass, and more preferably 0.05 to 0.3% by mass. When the content in the fiber is less than 0.02% by mass, the effect of imparting stain resistance is poor. On the other hand, when the content exceeds 1.0% by mass, the color tone of the fiber (yellowing or reddish) by the organic fluorescent whitening agent is reduced. Etc. may occur, which is not preferable.

  And since many organic fluorescent whitening agents as described above are inferior in light resistance, it is preferable to use an organic fluorescent whitening agent and a white inorganic pigment in combination. Thereby, it becomes possible to maintain the efficacy of the organic fluorescent whitening agent having poor light resistance for a long time.

  As specific examples of the white inorganic pigment, ceramics of oxides such as titanium oxide, zinc oxide, aluminum oxide, silicon oxide, and zirconium oxide are preferable, and titanium oxide is particularly preferable. Further, the content of the white inorganic pigment is preferably 0.3 to 10.0% by mass with respect to the fiber mass, and the average primary particle diameter is 0.4 μm or less, preferably 0.2 to 0.05 μm.

  If the average primary particle size of the white inorganic pigment exceeds 0.4 μm or the content exceeds 10.0% by mass, problems related to yarn production (early increase in filtration pressure, increase in the number of yarn breaks, etc.) occur. . On the other hand, when the content is less than 0.3% by mass or the average primary particle diameter is less than 0.05 μm, the barrier effect against ultraviolet rays becomes poor, and the above-described organic fluorescent whitening agent does not have the effect of improving the light resistance. It tends to be sufficient, and further, secondary agglomeration of the pigments occurs, and there is a tendency for the operability to deteriorate due to the problem of filter pressurization during spinning.

  The organic fluorescent whitening agent and white inorganic pigment as described above are contained in the regenerated polyester of the above-described embodiments (a) to (d) when the regenerated polyester fiber of the present invention is a single type or a composite type. It is preferable to make it. And the method of containing it in the regenerated polyester is not particularly limited, but it is added when repolymerizing the low molecular weight material obtained by depolymerizing the recycled polyester, or added when melt spinning after repolymerization. It is preferable to contain.

  In the present invention, the recycled polyester is once depolymerized into a low molecular weight product, and this is repolymerized. Therefore, although the recycled polyester is used, physical properties such as melt viscosity and molecular weight are large. Since there is no variation, even if an organic fluorescent whitening agent, a white inorganic pigment or the like is contained in the recycled polyester, it can be mixed uniformly, and the spinning operability does not deteriorate.

  In addition, in the regenerated polyester fiber of the present invention, in addition to the above phosphorus compounds and additives, as long as the effects of the present invention are not impaired, antioxidants such as hindered phenol compounds, other pigments, Additives and the like may be blended.

  Furthermore, since the recycled polyester fiber of the present invention uses a polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester, the color tone of the fiber is also excellent. As an index excellent in color tone, it is preferable that the L value indicating the color tone of the fiber is 85 or more and the b value is 5.0 or less, among which the L value is 90 or more and the b value is 4.5 or less. Furthermore, when the fluorescent whitening agent is contained, the color tone can be improved, so that the L value is preferably 92 or more and the b value is 4.3 or less.

  The L value is an index indicating the whiteness of the color, the b value is an index indicating the yellowness of the color, and when the L value is less than 85, a blackish color is obtained. When it exceeds 5.0, the yellowish color becomes too strong. Accordingly, when the L value is less than 85 or the b value exceeds 5.0, the appearance color tone is poor and the quality is poor both when the filament yarn is used as a raw yarn or as a fabric.

  In addition, L value and b value in the present invention are those obtained by measuring the L value and b value with a color difference meter CR-300 manufactured by MINOLTA by overlapping the obtained fibers (not dyed). It is.

  In addition, the shape of the regenerated polyester fiber of the present invention is not particularly limited to both a single type and a composite type, and may be a polygonal shape or a multileaf shape as well as a round cross-sectional shape, It may have a hollow.

  Furthermore, the regenerated polyester fiber of the present invention may be a multifilament or a monofilament, and may be either a long fiber or a short fiber.

  Next, the manufacturing method of the recycled polyester fiber (multifilament, single type) of this invention is demonstrated using an example. When recycled polyester derived from PET bottle is used, 5-30 parts by mass of ethylene glycol is added to 100 parts by mass of recycled polyester, and a depolymerization reaction is performed at 240-260 ° C. under slight pressure to lower the molecular weight. Let And it is preferable to remove a foreign material with a filter after depolymerization. This not only improves the operability during spinning, but also stabilizes the quality. On the other hand, as virgin polyester, terephthalic acid and EG are esterified by a conventional method to obtain an oligomer of virgin polyester. The obtained oligomer is added to a recycled polyester having a reduced molecular weight, and melt polymerization (repolymerization) is performed. At this time, it is preferable to add a polycondensation catalyst such as an antimony compound and carry out the polycondensation reaction by a conventional method. And in order to make the quantity of the component derived from the recycled polyester in polyester into a desired quantity, the addition amount of the oligomer of virgin polyester is adjusted. Then, a phosphorus compound and a white inorganic pigment are added during repolymerization to obtain a polyester polymer having a phosphorus atom content of 2000 to 30000 ppm.

  Then, the obtained polyester is chipped, and an additive such as an organic fluorescent brightening agent is added thereto and mixed, and melt spinning is performed using a normal melt spinning apparatus. At this time, the yarn is wound once by the POY method of winding as a semi-undrawn yarn by high-speed spinning of 2000 m / min or once, or melt spinning by high-speed spinning of 2000 m / min or more or low-speed spinning of less than 2000 m / min. Any one of a method of drawing and heat-treating in a separate step, and a spinning drawing method in which drawing is performed continuously without spinning may be employed.

Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, various values were measured and evaluated as follows.
(1) Intrinsic viscosity A mixture of phenol and ethane tetrachloride in a mass ratio of 1/1 was used as a solvent and measured at 20 ° C.
(2) Flame Retardancy Evaluation The obtained fiber was knitted in a tube, and the limiting oxygen index (LOI) was measured in accordance with JIS K 7201-2, and 27 or more were regarded as acceptable.
(3) Dyeing spots The cylindrical knitted fabric obtained in the measurement of (2) was dyed, the dyeing spots were judged visually, and evaluated in three stages.
○: Good △: Slightly mottled ×: Large occurrence of spots Dyeing conditions were 99 ° C using a dyeing solution of 2.0% omf of Terasil Nevy Blue SGL (Bayer dye yarn) and a bath ratio of 1:50 For 60 minutes.
(4) Strength and Elongation According to JIS L-1013, the tensile tester AG-100G manufactured by Shimadzu Corporation was used, the gripping interval was 500 mm, the tensile speed was 500 mm / min, and the value when the yarn was cut was measured.
(5) Fiber color tone Measured by the method described above.
(6) Stain resistance Similar to the measurement of (5), the obtained fiber was knitted into a tube, and this was 0.3 g of sodium tripolyphosphate, 0.3 g of sodium laurylbenzenesulfonate, 0.5 g of used engine oil and 0.5 g of viscosity. Was put in a contaminated solution dissolved in 1 liter of distilled water and subjected to a contamination treatment while stirring at 50 ° C. for 60 minutes. The knitted fabric was rinsed with running water, air-dried, and then washed for 10 minutes at 40 ° C. with a washing solution to which a monogen made by Daiichi Kogyo Seiyaku Co., Ltd. was added to 3 g / liter using an automatic washing machine for home use. After washing and rinsing, the knitted fabric was air-dried, and the stain resistance was visually evaluated in the following three stages.
○: Good △: Slightly dirty ×: Large amount of stain (7) Light resistance In the same manner as in the measurement of (5), the obtained fiber was knitted in a tube, and the tube knitted fabric was stored in a cool and dark place for 100 days. The gray scale difference of samples exposed to the sun for 100 days in an exposure container covered with a glass plate with a UV transmittance of 98% is determined according to the criteria for color fading according to JIS L-0801. Were evaluated as ○ (good) and those exceeding 1.5 were determined as x (bad).
(8) Operability
Evaluation was made based on the number of cut yarns when spinning with 16 spindles for 24 hours, and ○ and Δ were accepted criteria.
0 times: ○, 1-2 times: △, 3 times or more: ×

Example 1
Using recycled PET bottle waste (resin flakes collected for remolding without returning to low molecular weight), adding 20 parts by weight of ethylene glycol (EG) to 100 parts by weight of recycled polyester, temperature 240 ° C The depolymerization reaction was performed for 2 hours under slight pressure. After depolymerization, foreign matters were removed with a filter having an opening of 20 μm. A low molecular weight product having a molecular weight (number average molecular weight) of about 2000 was obtained by depolymerization.
Separately, as a virgin polyester, an esterification reaction was carried out at a temperature of 250 ° C. by an ordinary method with a molar ratio of terephthalic acid and EG of 1: 1.6 to obtain an oligomer.
And the obtained oligomer (oligomer of virgin polyester) and the recycled polyester reduced in molecular weight by the above depolymerization were mixed, and melt polymerization (repolymerization) was performed. At this time, low molecular weight recycled polyester and virgin polyester oligomer were introduced into a polycondensation reaction kettle at a mass ratio of 60:40, and phosphorus compounds (9,10-dihydro-9-oxa-10) were added as flame retardant components. After adding 4.3 mol% of an ethylene glycol dispersion of -phosphaphenanthrene-10-oxide (itaconic acid adduct), a polycondensation reaction was carried out at 275 ° C. in a conventional manner using antimony trioxide as a polycondensation catalyst. A polyester polymer having an intrinsic viscosity of 0.62 and a phosphorus atom content of 6000 ppm was obtained.
The obtained regenerated polyester had a ratio of the component derived from the recycle polyester of 60% by mass, and this regenerated polyester was dried by a conventional method into a chip.
This chip (intrinsic viscosity 0.62) was supplied to an extruder at 290 ° C. and then supplied to a spinning device to perform melt spinning. As the spinneret, one having 48 spinning holes having a hole diameter of 0.25 mm was used. The spun yarn is cooled by an air flow, passed through an oiling device, oil is applied so that the amount is 0.5% by mass, converged by a converging guide, entangled, and then a roller with a spinning speed of 3500 m / min. Was taken up with a take-up machine.
The obtained fiber (semi-undrawn yarn) was 255 dtex / 48f, and there were no defects due to fluff and single yarn breakage. Next, this was stretched at a speed of 700 m / min at a magnification of 1.53 times and at a temperature of 180 ° C. using a normal stretching apparatus to obtain 167 dtex / 48f recycled polyester fiber.

Examples 2-3 and Comparative Examples 1-2
A regenerated polyester fiber of 167 dtex / 48f was obtained in the same manner as in Example 1 except that the addition amount of the phosphorus compound added during repolymerization was changed so that the phosphorus atom content shown in Table 1 was obtained.

Example 4
The same procedure as in Example 1 was carried out except that the mixing ratio of the low molecular weight recycled polyester and the virgin polyester oligomer during repolymerization was changed, and the content of the component derived from the recycled polyester in the recycled polyester was 80% by mass. A recycled polyester fiber of 167 dtex / 48f was obtained.

Comparative Example 3
PET bottle waste recycled polyester used in Example 1 and a virgin polyester containing a phosphorus compound and a PET having an intrinsic viscosity of 0.64 with a phosphorus atom content of 15000 ppm are mixed at the chip stage (recycled polyester). The mixture was melt kneaded to remove the foreign matter with a filter and then spun and drawn in the same manner as in Example 1 except that spinning was performed, and 167 dtex / 48f recycled polyester fiber was obtained. Obtained.

Comparative Example 4
The recycled polyester of PET bottle waste used in Example 1 was once melted and pelletized, then supplied to the extruder A and melted, and foreign matters were removed with a filter. PET with an intrinsic viscosity of 0.64 with an atomic content of 15000 ppm is supplied to the extruder B and melted, and both are kneaded in the nozzle pack (adjusted so that the recycled polyester is 60% by mass) and spun. Spinning and drawing were carried out in the same manner as in Example 1 except that 167 dtex / 48f recycled polyester fiber was obtained.

  Table 1 shows the measured values and evaluation results of the strength, elongation, color tone, flame retardancy, dyeing spots, and operability of the fibers obtained in Examples 1 to 4 and Comparative Examples 1 to 4.

  As is clear from Table 1, the recycled polyester fibers obtained in Examples 1 to 4 were excellent in strength, elongation, and flame retardancy, and had good color tone, dyeability, and operability.

  On the other hand, the fiber of Comparative Example 1 was inferior in flame retardancy because the content of phosphorus atoms in the fiber was too small. The fiber of Comparative Example 2 was poor in operability because the content of phosphorus atoms in the fiber was too large. Since the fibers of Comparative Examples 3 and 4 were not polyesters obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester (the recycled polyester from waste PET bottles was only melted), However, dyeing spots were produced and the operability was also poor.

Example 5
In Example 1, a virgin polyester oligomer and a recycled polyester reduced in molecular weight by depolymerization were mixed, and when performing melt polymerization (repolymerization), titanium oxide (average particle size of 0.25 μm) was used as a white inorganic pigment. It was added so that the content was 0.4% by mass. The obtained recycled polyester (having a recycled polyester-derived component ratio of 60% by mass) was dried by a conventional method to form a chip, and then a benzoxazole fluorescent whitening pigment (yeast as an organic fluorescent whitening agent). Using yeast bright OB-1) manufactured by Mankodak Co., Ltd., it was added so that the content was 0.1% by mass. The chip added with the organic fluorescent brightening agent was melt-spun and stretched in the same manner as in Example 1 to obtain 167 dtex / 48f recycled polyester fiber.

Examples 6-7, Comparative Examples 5-6
A regenerated polyester fiber of 167 dtex / 48f was obtained in the same manner as in Example 5 except that the amount of the phosphorus compound added during repolymerization was changed so that the phosphorus atom content shown in Table 2 was obtained.

Example 8
The same procedure as in Example 1 was carried out except that the mixing ratio of the low molecular weight recycled polyester and the virgin polyester oligomer during repolymerization was changed, and the content of the component derived from the recycled polyester in the recycled polyester was 80% by mass. A recycled polyester fiber of 167 dtex / 48f was obtained.

Comparative Example 7
The PET bottle waste recycled polyester used in Example 1 was once melted and pelletized, and as the virgin polyester, a PET having an intrinsic viscosity of 0.64 containing a phosphorus compound and a phosphorus atom content of 15000 ppm was used. . Both are mixed at the chip stage (mixed so that the recycled polyester is 60% by mass), and the same benzoxazole fluorescent whitening pigment as in Example 5 is added so that the content becomes 0.1% by mass, and melt-kneaded. Then, after removing foreign matter with a filter, spinning and drawing were carried out in the same manner as in Example 5 except that spinning was performed to obtain 167 dtex / 48f recycled polyester fiber.

Comparative Example 8
The recycled polyester of PET bottle waste used in Example 1 was once melted and pelletized, then supplied to the extruder A and melted, and foreign matters were removed with a filter. PET having an intrinsic viscosity of 0.64 having an atomic content of 15000 ppm and a benzoxazole-based fluorescent whitening pigment content of 0.25% by mass as in Example 5 is supplied to the extruder B and melted, and both are contained in the nozzle pack. Spinning and stretching were carried out in the same manner as in Example 5 except that spinning was carried out in the same manner as in Example 5 except that spinning was carried out (adjustment of the supply amount so that the recycled polyester was 60% by mass) to obtain 167 dtex / 48f recycled polyester fiber.

  Table 2 shows measured values and evaluation results of the strength, elongation, color tone, flame retardancy, dyeing spots, stain resistance, light resistance, and operability of the fibers obtained in Examples 5 to 8 and Comparative Examples 5 to 8. Show.

  As is clear from Table 2, the recycled polyester fibers obtained in Examples 5 to 8 are excellent in strength, elongation, and flame retardancy, and have good color tone, dyeability, stain resistance, light resistance, and operability. there were.

  On the other hand, the fiber of Comparative Example 5 was inferior in flame retardancy because the content of phosphorus atoms in the fiber was too small. Since the fiber of Comparative Example 6 contained too much phosphorus atom in the fiber, the dyeability and operability were poor. Since the fibers of Comparative Examples 7 and 8 were not polyesters obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester (the recycled polyester from PET bottle waste was only melted), Spots were produced and operability was poor.

Examples 9-15
Except for changing the addition amount so that the content of the benzoxazole fluorescent whitening pigment becomes the value shown in Table 2, melt spinning and stretching were carried out in the same manner as in Example 5 to obtain a recycled polyester fiber of 167 dtex / 48f. Obtained.

  Table 2 shows the measured values and evaluation results of the strength, elongation, color tone, flame retardancy, dyeing spots, stain resistance, light resistance and operability of the fibers obtained in Examples 9 to 15.

  As is clear from Table 2, the recycled polyester fibers obtained in Examples 9 to 15 were excellent in strength, elongation, and flame retardancy, and had good color tone, dyeability, stain resistance, and light resistance. Among them, the regenerated polyester fibers of Examples 9 to 12, in which the content of the fluorescent whitening pigment was appropriate, were particularly excellent in stain resistance and light resistance and also in good operability.

Claims (5)

Recycled polyester containing at least one recycled polyester containing polyester obtained by repolymerization using a low molecular weight material obtained by depolymerizing recycled polyester, the fiber contains a phosphorus compound, and the content of phosphorus atoms A flame-retarded recycled polyester fiber characterized by having a 2,000 to 30,000 ppm. The flame retardant recycled polyester fiber according to claim 1, wherein the recycled polyester contains a phosphorus compound. The flame-retardant recycled polyester fiber according to claim 1 or 2, wherein the L value indicating the color tone of the fiber is 85 or more and the b value is 5.0 or less. The flame-retarded recycled polyester fiber according to any one of claims 1 to 3, wherein the fiber contains 0.02-1.0% by mass of an organic fluorescent brightening agent. The flame-retardant recycled polyester fiber according to any one of claims 1 to 4, wherein a content of a component derived from recycled polyester is 30% by mass or more of the entire fiber.