JP2005220465A - Recycled polyester fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively obtain a recycled polyester fiber with high whiteness even if using a recycled polyester, slight in the variations of physical properties, seldom causing color unevenness even after dyed in the form of a fabric, and suitably usable to clothing applications. <P>SOLUTION: The recycled polyester fiber is obtained by adding a copolymerizable component to a low-molecular weight product that is obtained by depolymerizing a recycled polyester followed by carrying out a polymerization again. The recycled polyester fiber is characterized by being ≥30 mass% in recycled polyester content. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a recycled polyester fiber excellent in dyeability, comprising a polyester obtained by depolymerizing and repolymerizing polyester recovered after use (hereinafter referred to as recycled polyester), and having improved dyeability by a copolymer component. Is.

  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 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.
JP 2000-328369 A JP 2002-060369 A JP 2002-060543 JP

  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 a technical problem to provide a regenerated polyester fiber that is less likely to cause stained spots and can be suitably used for clothing.

  As a result of intensive studies to solve the above problems, the present inventors have depolymerized recycled polyester to form a low molecular weight material, and contain a copolymer component that can be deeply dyed when this low molecular weight material is repolymerized. As a result, it has been found that coloring of recycled polyester and variation in performance can be reduced and dyeability can be improved, and the present invention has been achieved.

That is, the gist of the present invention is as follows.
(1) A fiber made of regenerated polyester containing a polyester obtained by repolymerization by adding a copolymerization component to a low molecular weight material obtained by depolymerizing recycled polyester, and the content of recycled polyester is 30 mass of the whole fiber. % Recycled polyester fiber characterized by being at least%.
(2) The regenerated polyester fiber according to (1), wherein at least one of 5-alkali metal isophthalic acid, adipic acid, sebacic acid, and a polyalkylene glycol having a molecular weight of 300 to 10,000 is used as a copolymerization component.
(3) The regenerated polyester fiber according to (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.

  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, it has excellent whiteness, little variation in physical property values, a fabric, and dyeing. Even when performed, dyeing spots are less likely to occur and can be suitably used for clothing.

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.

  And the fiber of this invention is a fiber which consists of regenerated polyester containing polyester which repolymerizes using the low molecular weight body which depolymerized recycled polyester. In other words, it is a fiber made of recycled polyester containing polyester that is depolymerized to reduce the molecular weight, but does not depolymerize until it becomes a monomer, and subsequently repolymerizes the lower molecular weight. is there. 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 body is continuously recovered in a low molecular weight state without being temporarily recovered as a monomer. And repolymerize. 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, since the recycled polyester is once decomposed into low molecular weight substances by depolymerization, and the polyester obtained by polymerizing the low molecular weight substances again is used, the recycled polyester is only melted and reused as before. 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.

  The depolymerized low molecular weight material in the present invention preferably has a molecular weight (number average molecular weight) of about 1000 to 4000. If the molecular weight exceeds 4000, 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. The low molecular weight body having the molecular weight as described above can be obtained by adjusting the addition amount of the glycol component to the recycled polyester, the temperature and pressure during the polymerization reaction, and the like.

  The recycled polyester fiber of the present invention has a recycled polyester content of 30% by mass or more of the entire fiber. 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. Therefore, the content of recycled polyester is 30% by mass or more, especially 40% by mass, and even 60% by mass. % Or more is preferable. On the other hand, the content of recycled polyester is preferably 90% by 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.

  Repolymerization using only a low molecular weight material obtained by depolymerization of recycled polyester can yield 100% recycled polyester (hereinafter referred to as polyester M). To make the content of recycled polyester 30-90% by mass, once depolymerized and repolymerized only recycled polyester, 100% recycled polyester (polyester M) was obtained as a polyester blended with virgin polyester. Also good. Further, after depolymerizing the recycled polyester, an oligomer of virgin polyester is added at the time of repolymerization, and a low molecular weight material obtained by depolymerizing the recycled polyester and a monomer of the virgin polyester (hereinafter referred to as polyester N). Yes). 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. .
(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, recycled polyester is used as a raw material, so the content of recycled polyester in the fiber is the amount of recycled polyester used as a raw material contained in the entire fiber. That's what it says.

  In the recycled polyester fiber of the present invention, the recycled polyester content is 30% by mass or more as described above in any of the recycled polyester embodiments (a) to (d).

  The regenerated polyester fiber of the present invention is obtained by depolymerizing recycled polyester to obtain a low molecular weight material as described above, and then repolymerizing it by adding a copolymer component during repolymerization. As the copolymer component, a component capable of deep dyeing is preferable, and at least one of 5-alkali metal isophthalic acid, adipic acid, sebacic acid, and polyalkylene glycol having a molecular weight of 300 to 10,000 is preferably used.

  When 5-alkali metal isophthalic acid is used, it is preferable to copolymerize 0.5 to 3.0 mol%. When the copolymerization amount is less than 0.5 mol%, the improvement in dyeing performance is small, it is difficult to obtain good dyeing performance, and color spots are likely to occur. On the other hand, when it exceeds 3.0 mol%, not only the strength of the obtained recycled polyester fiber is lowered, but also the color tone tends to be remarkably deteriorated. Among the compounds used as the 5-alkali metal isophthalic acid component, particularly preferred examples include 5-sodium sulfoisophthalic acid, sodium 3,5-di [carbomethoxy] benzenesulfonate (or potassium or lithium), Examples include sodium 3,5-di (β-hydroxyethoxycarbonyl) benzenesulfonate (or potassium or lithium).

  When using adipic acid or sebacic acid, it is preferable to copolymerize 1.0 to 5.0 mol%. When the copolymerization amount is less than 1.0 mol%, the improvement in the dyeing performance is small, it is difficult to obtain good dyeing performance, and color spots are likely to occur. On the other hand, if it exceeds 5 mol%, the melting point of the polymer is lowered, and blocking in which the polymers are fused is likely to occur.

  When a polyalkylene glycol having a molecular weight of 300 to 10,000 is used, it is preferably copolymerized in an amount of 0.5 to 4.0% by mass. When the molecular weight of the polyalkylene glycol is less than 300 or the copolymerization amount of the polyalkylene glycol is less than 0.5% by mass, the effect of improving the dyeing performance is small. On the other hand, when the molecular weight of the polyalkylene glycol exceeds 10,000, the heat resistance and weather resistance of the polyalkylene glycol itself are lowered, and when the copolymerization amount exceeds 4.0% by mass, the weather resistance of the resulting polyester is lowered, It is not preferable.

  Examples of the polyalkylene glycol used in this method include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  In the present invention, at least one of 5-alkali metal isophthalic acid, adipic acid, sebacic acid, and polyalkylene glycol having a molecular weight of 300 to 10,000 is copolymerized. It may be copolymerized.

  In the recycled polyester fiber of the present invention, as copolymerization components other than those described above, aromatic dicarboxylic acids such as 3,3′-diphenyldicarboxylic acid, aliphatic dicarboxylic acids such as succinic acid, diethylene glycol, 1,4-butanediol Aliphatic such as 1,4-cyclohexanediol, alicyclic diol, P-hydroxybenzoic acid and the like may be copolymerized.

  In the present invention, when the above-described polyester M is used, repolymerization is performed by adding a copolymerization component when repolymerizing a polyester obtained by depolymerizing a recycled polyester. In addition, when the polyester N is used, a copolymer component is added simultaneously with the virgin polyester oligomer when the recycled polyester is depolymerized into a low molecular weight product. You may use what added the copolymerization component.

  As described above, in the recycled polyester fiber of the present invention, by adding a copolymer component when re-polymerizing a low molecular weight material obtained by depolymerization of the recycled polyester, the recycled polyester and copolymer component are simply added by the conventional method. When the contained virgin polyester is melt-kneaded, melt-kneading becomes insufficient, and the problem that the strength of the resulting fiber is reduced can be solved, and it has sufficient strength that can be used for practical applications It can be a fiber.

  In addition, as an index that the regenerated polyester fiber of the present invention is excellent in color tone, the L value indicating the color tone of the fiber is preferably 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 3.8. The following is preferable.

  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, the color becomes blackish. 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 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.

  Furthermore, in the regenerated polyester fiber of the present invention, an antioxidant such as a hindered phenol compound, other pigments, additives and the like may be blended as long as the effects of the present invention are not impaired. Among these, it is preferable to contain 1.5 to 10% by mass of titanium oxide.

  By containing titanium oxide, it is possible to improve the concealability, that is, the whiteness when it is made into a fabric. When the content of titanium oxide is less than 1.5% by mass, the effect of improving whiteness becomes insufficient. When the content of titanium oxide exceeds 10% by mass, problems such as filter pressurization during spinning and wear of the guide occur, and the operability tends to deteriorate.

  Next, the method for producing the recycled polyester fiber of the present invention will be described using an example. When the polyester derived from the PET bottle is used as the recycled polyester, 5 to 30% by mass of ethylene glycol is added to the recycled polyester, and a depolymerization reaction is performed at 240 to 260 ° C. under a slight pressure to reduce the molecular weight. 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. Subsequently, as a virgin polyester, terephthalic acid and EG are esterified by a conventional method to obtain an oligomer of virgin polyester.

  The obtained oligomer and copolymer component are 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. Moreover, in order to make the quantity of the recycled polyester in polyester into a desired quantity, the addition amount of the oligomer of virgin polyester is adjusted.

  The obtained polyester is melt-spun 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.

  When the POY method as described above is employed, it is preferable that the obtained recycled polyester fiber (semi-undrawn yarn) has a strength of 1.6 cN / dtex or more and an elongation of 150% or less. When the strength is less than 1.6 cN / dtex or the elongation exceeds 150%, fluff and untwisting tend to occur when falsely twisting the recycled polyester fiber. When the POY method is adopted, the birefringence Δn of the regenerated polyester fiber is preferably 0.03 to 0.06 suitable for ordinary drawing false twisting.

  Further, when the drawing is performed after the high speed spinning or the low speed spinning, the breaking strength of the recycled polyester fiber (drawn yarn) of the present invention is preferably 4.0 cN / dtex or more. When the breaking strength is less than 4.0 cN / dtex, fluff is likely to occur when the fabric is used, and the quality is liable to be significantly reduced.

  The shape of the regenerated polyester fiber of the present invention is not particularly limited, and may be not only a round cross-sectional shape, but also a polygonal shape or a multileaf shape, or may have a hollow shape.

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) Strength (breaking strength), elongation Value according to JIS L-1013, using a tensile tester AG-100G manufactured by Shimadzu Corporation, with a gripping interval of 500 mm, a tensile speed of 500 mm / min, and a value when the yarn is cut Was measured.
(3) Birefringence
Using a POE polarizing microscope, the measurement was performed by the Belek Compensator method.
(4) Color tone of fiber It measured by the said method.
(5) Dyeing spots The cylindrical knitted fabric obtained in the measurement of (4) was dyed, the dyeing spots were judged visually, and evaluated in three stages.
○: Good △: Slightly uneven ×: Spots are large The dyeing conditions are Terasil Nevy Blue SGL (Bayer's dye for raw yarn) with a 2.0% omf bath ratio of 1:50 at 99 ° C. Stained by conventional methods for 60 minutes.

Example 1
Using PET bottle waste (resin flakes collected for the purpose of remolding without returning to low molecules) as recycled polyester, 20% by mass of ethylene glycol (EG) is added to the recycled polyester, and the temperature is 250 ° C. The depolymerization reaction was performed for a period of time 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, a molar ratio of terephthalic acid and EG was 1: 1.6, and an esterification reaction was performed at a temperature of 250 ° C. by a conventional method to obtain a PET oligomer.
Then, the obtained oligomer was added to recycled polyester whose molecular weight was reduced by depolymerization, and melt polymerization (repolymerization) was performed. At this time, recycled polyester having reduced molecular weight and PET oligomer were introduced into a polycondensation reaction kettle at a mass ratio of 60:40, 5-sodium sulfoisophthalic acid was added as an ethylene glycol slurry, and antimony trioxide was added. As a polycondensation catalyst, a polycondensation reaction was performed at 285 ° C. by a conventional method.
The obtained polyester had a recycled polyester content of 60% by mass and was a copolymer of 1.5 mol% of 5-sodium sulfoisophthalic acid.
This polyester resin was dried by a conventional method, supplied to an extruder at 295 ° C., supplied to a spinning device, and melt spinning was performed. As the spinneret, one having 48 spinning holes having a hole diameter of 0.25 mm was used. The spun yarn bundle is cooled by an air flow, passed through an oiling device, an oil agent is applied so that the amount of adhesion is 0.5% by mass, converged by a converging guide, entangled and then spun at a spinning speed of 3500 m / min. It was taken up with a roller and wound 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 fiber was drawn at a speed of 700 m / min and a magnification of 1.53 times at a temperature of 180 ° C. using a normal drawing apparatus to obtain a recycled polyester fiber of 167 dtex / 48f.

Examples 2-4
The same procedure as in Example 1 was conducted except that the mixing ratio of the low molecular weight recycled polyester and virgin polyester oligomer during repolymerization and the copolymerization amount of 5-sodium sulfoisophthalic acid were changed as shown in Table 1, and 167 dtex / A 48f recycled polyester fiber was obtained.

Examples 5-12
The same procedure as in Example 1 was conducted except that the mixing ratio of the low-molecular weight recycled polyester and virgin polyester oligomer at the time of repolymerization, the type of copolymerization component and the copolymerization amount were changed as shown in Table 1, and 167 dtex / 48f Regenerated polyester fiber was obtained.

Comparative Example 1
Recycled PET bottle waste polyester used in Example 1 and PET copolymerized with 4 mol% of 5-sodium sulfoisophthalic acid as virgin polyester were mixed at the chip stage (mixed so that the recycled polyester was 60% by mass). Then, spinning and drawing were carried out in the same manner as in Example 1 except that spinning was performed from a single-hole spinneret to obtain a 167 dtex / 48f recycled polyester fiber.

Comparative Example 2
The recycled PET bottle waste polyester used in Example 1 and PET that does not contain a copolymer component as virgin polyester are mixed at the chip stage (mixed so that the recycled polyester is 60% by mass), melt-kneaded, Spinning and drawing were performed in the same manner as in Example 1 except that spinning was performed from a single-hole spinneret to obtain 167 dtex / 48f recycled polyester fiber.

  Table 1 shows the strength, elongation, birefringence index, color tone, measured values of the stained spots, and evaluation results of the fibers obtained in Examples 1 to 12 and Comparative Examples 1 and 2.

表１から明らかなように、実施例１〜１２で得られた再生ポリエステル繊維は、強度、伸度、色調に優れ、染色性も良好であった。

As is clear from Table 1, the regenerated polyester fibers obtained in Examples 1 to 12 were excellent in strength, elongation, color tone, and dyeability.

  On the other hand, since the fibers of Comparative Examples 1 and 2 were fibers obtained by simply melting and mixing recycled polyester and virgin polyester, the color tone was poor, dyeing spots were generated, and the operability was also poor.

Claims (3)

A fiber made of recycled polyester containing polyester obtained by depolymerizing recycled polyester and adding a copolymerization component to repolymerize, and the content of recycled polyester is 30% by mass or more of the total fiber. Recycled polyester fiber characterized by being. 2. The regenerated polyester fiber according to claim 1, wherein at least one of 5-alkali metal isophthalic acid, adipic acid, sebacic acid, and polyalkylene glycol having a molecular weight of 300 to 10,000 is used as a copolymerization component. The regenerated 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.