KR20000018763A - Method for producing polyester recycled fiber - Google Patents

Abstract

PURPOSE: A method for producing a polyester recycled fiber is provided to improve the natural viscosity, and to have the stable pyrolysis by using the 2,2'-vis oxazoline as an agent for extending a chain having the good reactivity with the end carboxyl of the polyester and having the excellent thermal characteristic. CONSTITUTION: A recycled fiber is produced by melting and mixing 0.1-10wt% of the 2,2'-vis oxazoline as an agent for extending a chain for the waste polyester or for the copolymer thereof. Thereby the terminal carboxyl operated as a catalyst about a pyrolysis of the polyester is blocked, and the more improved natural viscosity than the starting polyester is obtained by pair reacting between the terminal carboxyl of the starting waste polyester. Therefore, the pyrolysis is prevented though receiving a melted processing again.

Description

Method for producing polyester recycled fiber

The present invention relates to a method for producing polyester recycled fibers using waste polyethylene terephthalate (hereinafter referred to as waste polyester).

More specifically, waste polyester, which has low intrinsic viscosity and high terminal carboxy content, that is, melt spinning by adding 2, 2′-bisoxazoline to waste polyester produced when producing a product such as polyester fiber. It relates to a method for producing polyester recycled fiber.

Today, a large amount of polyester waste is disposed of in the form of films, bottles, fibers, etc., and much effort is being made to recycle it. However, the recycling range of polyester is mainly limited to materials such as injection or extrusion, because the material is not significantly affected by the intrinsic viscosity of the polyester and is used at a relatively low intrinsic viscosity. It is only some high viscosity waste polyester that is recycled into recycled fibers. Once the polyester undergoes a process such as spinning or extruding, it undergoes thermal history and pyrolysis occurs, resulting in a decrease in intrinsic viscosity and deterioration in mechanical properties. In addition, when recycled and processed waste polyester into a usable chip and manufactured it as regenerated products such as regenerated fibers, the secondary and tertiary heat history is continuously received and thermal decomposition occurs, so the intrinsic viscosity of polyester is further lowered. It will greatly reduce the mechanical properties of.

As such methods for improving the reduced intrinsic viscosity, there are a method of performing melt condensation polymerization by remelting, a method of performing postcondensation polymerization in a solid phase, and a method of causing a coupling reaction using a chain extender.

Among the above-mentioned methods, the melt condensation polymerization method not only causes addition reaction due to pyrolysis when re-melting waste polyester, but also it is not easy to implement due to its complicated method. It is difficult.

In addition, the post-condensation polymerization method in the solid phase has a low treatment temperature due to the low thermal decomposition, but the reaction rate is slow and has a disadvantage in that a separate treatment equipment must be provided to process a large amount of polyester.

In contrast, the use of a chain extender, a bifunctional compound in which the hydroxy group and the carboxyl group of the polyester easily react, not only increases the molecular weight by the intermolecular coupling reaction, but also the reaction time is very short, so that spinning, extrusion or injection molding is possible. Attention has been paid to the most preferred method for producing polyesters having improved intrinsic viscosity since they can act directly in the general melting process step.

A method for producing polyester by a coupling reaction using a chain extender has been shown in Japanese Patent Laid-Open No. 50-59525.

This method is a method of spinning by adding a phenylenebisoxazoline compound to polyester, and has been described as having an effect of reducing the carboxy terminal group of the polyester, improving viscosity and reducing thermal decomposition occurring in the spinning process.

However, the phenylene bisoxazoline has an effect of suppressing a decrease in intrinsic viscosity due to thermal decomposition when reacting with the polyester, but the reactivity between the phenylene bisoxazoline and the carboxy terminal group of the polyester is not sufficient, compared to the starting polyester The effect of improving the intrinsic viscosity of the final polyester is not so high.

In addition, the phenylene bisoxazoline is not heat-resistant (melting point 14 ℃) has a disadvantage in that it is easily decomposed to heat when melt processing by mixing.

The present invention uses polyester 2,2′-bisoxazoline, which has good reactivity with polyester terminal carboxyl group and excellent thermal properties (melting point of 214 ℃) as a chain extender, thereby producing polyester regenerated fiber which is highly intrinsic in viscosity and stable to thermal decomposition. The technical challenge is to provide a way to do this.

In the present invention, in the production of polyester regenerated fibers using waste polyester or its copolymer, 0.1 to 10% by weight of 2, 2′-bisoxazoline, which is a chain extender, is melt-mixed with respect to the waste polyester or its copolymer. It is characterized in that the manufacturing.

In addition, the present invention may be prepared by adding and mixing 0.1-5% by weight of a heat stabilizer with respect to the total weight of the waste polyester and 2,2'-bisoxazoline in order to further improve the heat resistance.

In the present invention, 2,2′-bisoxazoline serves to improve the intrinsic viscosity of the polyester by forming a coupling reaction with the carboxy terminal group of the polyester, if the amount of the amount is less than 0.1% by weight of the polyester terminal carboxyl group There is no coupling reaction effect, and if it exceeds 10% by weight, thermal decomposition of 2,2'-bisoxazoline causes a problem that the color of the regenerated polyester is changed and the viscosity is lowered.

In addition, when the heat stabilizer is added in excess of 5% by weight, the effect of the heat stabilizer is rather reduced, and the mechanical properties of the regenerated polyester are lowered, and when added at less than 0.1% by weight, there is no effect of addition.

As described above, the present invention is a method of preparing by adding 2,2′-bisoxazoline as a chain extender for the coupling reaction, so that the terminal carboxyl group catalyzing the thermal decomposition of the polyester is blocked and the starting waste poly The coupling reaction between the terminal carboxyl groups of the ester has an improved intrinsic viscosity than the starting polyester. Therefore, the recycled polyester not only suppresses thermal decomposition even when subjected to melt processing again, but also has an improved intrinsic viscosity compared to the starting waste polyester, and this effect is further enhanced when additional heat stabilizers are added.

The characteristic evaluation of the polyester which concerns on this invention was performed by the following method.

(1) intrinsic viscosity (IV)

The relative viscosity η _r of the solution in which 80 g of the sample was dissolved in 100 ml of orthochlorophenol was measured at 25 ° C. using an Ubelrod viscometer to calculate IV by the following approximation formula.

IV = 0.0242 η _r + 0.2634

t × d

Where η _r = ━━━━━━━

t ₀ × d ₀

t: dropping time of solution (seconds)

t ₀ : Falling time of orthochlorophenol (seconds)

d: density of solution (g / cc)

d ₀ : density of orthochlorophenol (g / cc)

(2) terminal carboxyl group content

The pulverized sample was dissolved in benzyl alcohol at 203 ° C, phenol red indicator was added, and neutralization titration of the terminal carboxyl group in the polymer with a caustic carbenzyl alcohol solution was carried out to calculate g equivalent / 1000 g of the terminal carboxyl group by the following formula.

The degree of pyrolysis is compared relative to the content of terminal carboxyl groups.

(A-B) × f

C = ━━━━━━━━ × 100

W

C: terminal carboxyl group content (equivalent / 1000 g)

A: 0.1 normal caustic carry benzyl alcohol appropriate amount (ml)

B: ball test 0.1 normal caustic benzyl alcohol appropriate amount (ml)

f: Factor of caustic benzyl alcohol

W: sample weight

◆ Preparation example of polyester melt mixture (compounding);

Regenerated polyester chips were prepared by adding a thermal stabilizer to the starting waste polyester and 2,2′-bisoxazoline or the two components and then masterbatching in a conventional manner.

Starting waste polyesters used in this method were those having an intrinsic viscosity of 0.4 to 1.1 dl / g and a content of terminal carboxyl groups of 20 to 100 meq / kg.

◆ Production example of recycled polyester fiber;

Using the recycled polyester chip prepared as described above or mixed with the composition ratio of Table 1 starter polyester and 2,2'-bisoxazoline or the heat stabilizer added to the two components directly into the fiber melt spinning machine It was supplied to and spun in a conventional polyester fiber manufacturing method for producing a polyester recycled fiber.

Examples 1-4

Using recycled polyester having an intrinsic viscosity of 0.58 dl / g and a terminal carboxyl group of 52 meq / kg, melt mixing at the composition ratios of Table 1 to make a regenerated polyester chip, and using the regenerated chip to regenerate as described above The fiber was stretched by stretching in the manufacturing method of the polyester fiber. The melt workability and spinning workability of the recycled polyester chip at this time was evaluated and the results are shown in Table 1 below.

Examples 5-8

Using waste polyester having an intrinsic viscosity of 0.76 dl / g and a terminal carboxyl group of 35 meq / kg, and melt-mixing according to the composition ratios of Table 1 to make a regenerated polyester chip, and producing the regenerated fiber using the regenerated chip. Spin-drawn by the method to form a fiber. The melt workability and spinning workability of the recycled polyester chip at this time was evaluated and the results are shown in Table 1 below.

Comparative Examples 1-2 (without chain extension)

Initially polymerized polyester, not waste polyester, polyester for general garments with an intrinsic viscosity of 0.64 dl / g and a terminal carboxyl group of 35 meq / kg, and a general high viscosity polyester with an intrinsic viscosity of 0.80 dl / g and a terminal carboxyl group of 28 meq / kg Each of the esters was spin-drawn in the above manner to form fibers. The workability at the time of spinning the polyester fiber at this time was evaluated and the results are shown in Table 1 below.

Comparative Examples 3 to 4

Phenylenebisoxazoline was added to each of the waste polyesters having an intrinsic viscosity of 0.58 dl / g and the terminal carboxyl group of 52 meq / kg, and the waste polyesters having the intrinsic viscosity of 0.76 dl / g and the terminal carboxyl group of 35 meq / kg. Melt blended together to make a regenerated polyester chip, which was spun and stretched by the above method to form a fiber. The workability of the recycled polyester chip at this time and the workability when spinning the fiber with it is evaluated and the results are shown in Table 1 below.

Comparative Examples 5-6

Using waste polyester having an intrinsic viscosity of 0.58 dl / g and a terminal carboxyl group of 52 meq / kg, melt blending according to the composition ratios in Table 1 to make regenerated polyester chips, and spin-stretching using the regenerated chips as described above. To form a fiber. The workability of the recycled polyester chip at this time and the workability when spinning the fiber with it is evaluated and the results are shown in Table 1 below.

Comparative Examples 7 to 8

Using waste polyester with an intrinsic viscosity of 0.76 dl / g and a terminal carboxyl group of 35 meq / kg, melt blending according to the composition ratios in Table 1 to make a regenerated polyester chip, and using this regenerated chip to spin-stretch it. To form a fiber. The workability of the recycled polyester chip at this time and the workability when spinning the fiber with it is evaluated and the results are shown in Table 1 below.

Physical property Composition ratio (% by weight) Viscosity (dl / g) Viscosity Enhancement Effect Terminal carboxyl groups (meq / kg) Pyrolysis Inhibition Effect Dragon blending workability Radiation workability (Waste) polyester 2,2'-bisoxazoline Heat stabilizer Waste polyester (Recycled) Polyester Chip Recycled fiber Waste polyester (Recycled) Polyester Chip Recycled fiber Example 1 99.9 0.1 0.0 0.58 0.60 0.60 Good 52 38 38 Good Great Good Example 2 95.0 5.0 0.0 0.58 0.64 0.65 Great 52 22 20 Great Great Great Example 3 94.0 1.0 5.0 0.58 0.62 0.63 Great 52 15 14 Great Great Great Example 4 99.1 0.8 0.1 0.58 0.67 0.68 Great 52 12 10 Great Great Great Example 5 99.9 0.1 0.0 0.76 0.78 0.78 Good 35 31 31 Good Great Great Example 6 95.0 5.0 0.0 0.76 0.80 0.81 Great 35 20 21 Great Great Great Example 7 94.0 1.0 5.0 0.76 0.81 0.82 Great 35 12 10 Great Great Great Example 8 99.1 0.8 0.1 0.76 0.82 0.84 Great 35 8 8 Great Great Great Comparative Example 1 100 0.0 0.0 - 0.64 0.62 Bad - 35 40 Bad - Great Comparative Example 2 100 0.0 0.0 - 0.80 0.78 Bad - 28 34 Bad - Great Comparative Example 3 95.0 5.0 0.0 0.58 0.58 0.57 Bad 52 41 42 Good Great Good Comparative Example 4 95.0 5.0 0.0 0.76 0.76 0.75 Bad 35 31 35 Good Great Great Comparative Example 5 100 0.0 0.0 0.58 0.53 0.51 Bad 52 68 79 Bad Bad Bad Comparative Example 6 99.5 0.05 0.0 0.58 0.57 0.57 Bad 52 48 45 usually usually Bad Comparative Example 7 100 0.0 0.0 0.76 0.73 0.71 Bad 35 42 58 Bad Great usually Comparative Example 8 99.5 0.05 0.0 0.76 0.75 0.74 Bad 35 32 35 usually Great Great

※ The comparative examples 3 and 4 of Table 1 are the thing which added waste-nilene bisoxazoline

※ Criteria for Viscosity Enhancement Effect: Evaluated by viscosity change when waste polyester is made into recycled polyester chip

-Excellent: Viscosity improves more than 0.03dl / g compared to the viscosity of initial polyester

-Good: Viscosity improves less than 0.03dl / g compared to the viscosity of initial polyester

-Poor: Reduced viscosity compared to the viscosity of initial polyester

※ Evaluation criteria for the effect of inhibiting pyrolysis: It is evaluated by the change of viscosity and the change of terminal carboxyl group when (waste) polyester is made into recycled polyester chip.

-Excellent: Viscosity improves more than 0.03dl / g compared to initial polyester

Reduced terminal carboxyl group by more than 15 meq / kg

Good: Viscosity improves less than 0.03 dl / g against the initial polyester viscosity

Terminal carboxyl groups are reduced by more than 4 and less than 15 meq / kg

-Normal: Viscosity of -0.02 or more and less than 0dl / g compared to the viscosity of initial polyester

Decrease in terminal carboxyl groups from 0 to less than 4 meq / kg

-Poor: Viscosity decreases below -0.02dl / g and terminal carboxyl group increases compared to viscosity of initial polyester

※ Evaluation criterion for spinning workability: Evaluation by trimming rate when spinning fiber with (regenerated) polyester chip

-Excellent: trimming rate is less than 0.5% during spinning

-Good: trimming rate is 0.5 ~ 1% during spinning

-Normal: Trimming rate is 1 ~ 2% during spinning

-Poor: more than 2% of trimming rate during spinning

The regenerated chip of the polyester or its copolymer obtained according to the present invention and the polyester regenerated fiber made from the regenerated chip have an improved viscosity and an inhibitory effect on thermal decomposition.

In addition, the present invention improves spinning workability because of good melt mixing.

The recycled polyester chip according to the present invention can be utilized not only as a fiber but also as a raw material for producing films or bottles.

Claims (2)

A method for producing a polyester regenerated fiber, characterized by melting and mixing 0.1 to 10% by weight of 2,2′-bisoxazoline to waste polyester or polymers thereof. The method for producing a polyester regenerated fiber according to claim 1, wherein the thermal stabilizer is added by 0.1 to 5% by weight based on the total weight and melt mixed.