JP2018150397A - Method of producing recycled polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing recycled polyester, the method using recycled polyester mainly containing ethylene terephthalate unit and nonetheless materializing production of recycled polyester which, when formed into a polyester fiber, exhibits suitable heat adhesiveness, excellent color tone, and stable and good quality.SOLUTION: The method of producing recycled polyester is provided which comprises supplying recycled polyester mainly containing ethylene terephthalate unit to an esterification process together with isophthalic acid and glycol to obtain an oligomer, then polycondensing the oligomer by a polycondensation process to generate recycled polyester, and in which a bisphenol group-containing compound having a specific chemical structure of 2.0 to 9.0 mass% based on total mass of the recycled polyester is added to the oligomer between completion of the esterification process and initiation of the polycondensation process.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing recycled polyester.

  Conventionally, polyethylene terephthalate (PET), which is one of polyesters, is prepared by first sending terephthalic acid (TPA) and ethylene glycol (EG) to an esterification reaction apparatus to carry out an esterification reaction. Subsequently, it is sent to a polycondensation reaction apparatus and produced by a polycondensation reaction. Since such PET has excellent mechanical properties, heat resistance, weather resistance, electrical insulation and chemical resistance, it is used in the textile field for clothing, industrial use, etc., and molded products and packaging films such as sheets and engineering plastics. It is widely used in various fields such as a film field such as a magnetic tape film.

  Further, in recent years, in non-woven fabrics for pasting base materials used for daily use, particularly for poultices and plasters, the proportion of polyester fibers used as constituent fibers has increased, Thermally-bonded fibers comprising a polyester-based polymer having favorable and favorable thermal adhesiveness as a heat-bonding component have been desired.

  Examples of the polyester constituting the heat-bonding fiber composed of a polyester-based polymer used for non-woven fabrics having such adhesive properties include, for example, polyester mainly composed of ethylene terephthalate units, isophthalic acid and bis (4-hydroxy) as copolymerization components. An amorphous copolyester obtained by copolymerizing an alkylene oxide adduct of phenyl) sulfone within a specific range is used (see Patent Document 1).

  On the other hand, since recycled polyester (polyester waste) generated in the manufacturing process of these polyester products is disposed of after use, effective use of polyester waste is extremely important industrially in terms of cost and the like.

  As a method for producing recycled polyester using polyester waste, the polyester waste generated in the production process of the polyester product was mixed with ethylene glycol for depolymerization to obtain a low polymer mainly composed of an ester monomer. Supplying a low polymer obtained by polycondensation of a low polymer to a regenerated polyester (see Patent Document 2) and a low polymer obtained by depolymerizing polyester waste together with isophthalic acid and a bisphenol group-containing compound A technique for producing a regenerated polyester by polycondensation of a low polymer obtained in this manner is disclosed (see Patent Document 3).

JP 2005-29644 A JP-A-48-61447 Japanese Patent Application Laid-Open No. 2015-140412

  However, in the above manufacturing technique, a recycled polyester (polyester waste) is applied to obtain a recycled polyester having thermal adhesive properties. However, when a recycled polyester is produced by applying a bisphenol group-containing compound, a bisphenol group-containing compound is obtained. It is necessary to shorten the esterification reaction and / or polycondensation reaction time because the color tone of the polyester deteriorates (yellowing) due to the thermal decomposition of the polyester. The technology capable of obtaining recycled polyester has not yet been established.

  Therefore, the object of the present invention is to use a recycled polyester having a polyethylene terephthalate unit as a main component, but has good thermal adhesion when used as a polyester fiber, excellent color tone, and stable and good quality. It is in providing the manufacturing method of recycled polyester.

The inventors of the present invention have arrived at the present invention as a result of studies to solve the above problems. That is, the present invention is intended to solve the above-described problem,
The method for producing a regenerated polyester of the present invention is such that a recycled polyester mainly composed of an ethylene terephthalate unit is supplied to an esterification step together with isophthalic acid and glycol to obtain an oligomer, and then the oligomer is polycondensed by a polycondensation step. In the production method of the regenerated polyester produced in this manner, the polycondensation process is started from the end of the esterification step with 2 to 9% by mass of the bisphenol group-containing compound represented by the following general formula (1) based on the total mass of the regenerated polyester. It is the manufacturing method of the regenerated polyester characterized by adding between.

[In the above formula, R ¹ and R ² represent a hydrocarbon residue. X represents a sulfonyl group or a dimethylmethylene group. ]

  According to a preferred embodiment of the method for producing a regenerated polyester of the present invention, 4 to 16% by mass of the isophthalic acid is supplied to the depolymerization step based on the total mass of the regenerated polyester.

  According to a preferred embodiment of the method for producing a regenerated polyester of the present invention, the bisphenol group-containing compound is 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane or 2,2-bis [4- ( 2-hydroxyethoxy) phenyl] sulfone, which is added in a molten state between the end of the esterification step and the start of the polycondensation step.

  According to the present invention, while using a recycled polyester mainly composed of an ethylene terephthalate unit, it is possible to improve the productivity of polyester having excellent thermal adhesiveness when made into a polyester fiber, and to produce a stable and good quality recycled polyester. Can be obtained. The polyester obtained by the method for producing a regenerated polyester of the present invention is suitable as a polyester for obtaining fibers, woven or knitted fabrics, and nonwoven fabrics, and is particularly suitable for heat-welded and heat-bonded fibers for nonwoven fabric applications.

  Next, the form for implementing the manufacturing method of the reproduction | regeneration polyester of this invention is demonstrated.

  The method for producing a regenerated polyester of the present invention is such that a recycled polyester mainly composed of an ethylene terephthalate unit is supplied to an esterification step together with isophthalic acid and glycol to obtain an oligomer, and then the oligomer is polycondensed by a polycondensation step. In the production method of the regenerated polyester produced in this manner, the polycondensation process is started from the end of the esterification step with 2 to 9% by mass of the bisphenol group-containing compound represented by the following general formula (1) based on the total mass of the regenerated polyester It is the manufacturing method of the regenerated polyester characterized by adding between.

[In the above formula, R ¹ and R ² represent a hydrocarbon residue. X represents a sulfonyl group or a dimethylmethylene group. ]

  The recycled polyester referred to in the present invention is a polyester having ethylene terephthalate units as a main component, and preferably a polyester polymer containing 70% by mole or more of ethylene terephthalate with respect to the recycled polyester. Polyester produced using terephthalic acid or a lower alkyl ester thereof as the dicarboxylic acid component and ethylene glycol (EG) as the glycol component. Some of the terephthalic acid components are aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, diphenoxyethanedicarboxylic acid, and aliphatic carboxylic acids such as dodecanedioic acid, adipic acid, sebacic acid, azelaic acid, and decanedicarboxylic acid. Furthermore, it may be replaced with an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid, a hydroxycarboxylic acid such as hydroxybenzoic acid, glycolic acid, or hydroxyethoxybenzoic acid. In addition, some of the glycol components are aliphatic, alicyclic, and aromatic diol compounds such as polytetramethylene glycol, propylene glycol, diethylene glycol, hexamethylene glycol, p-xylene glycol, 1,4-cyclohexadimethanol, and bisphenol. It may be replaced with. In addition, the polyester may contain additives such as pigments, heat-resistant materials, and fluorescent brightening agents.

  The recycled polyester (polyester waste) used in the present invention is polyester waste generated in the production process of polyester products such as fibers, films and resins. The form of the polyester waste may be not only polyester chip waste, film waste, and yarn waste, but also any of those used as products.

  In the present invention, it is particularly important to copolymerize an oligomer obtained by depolymerizing recycled polyester with isophthalic acid.

  The copolymerization ratio of isophthalic acid is preferably 4 to 16% by mass, more preferably 5 to 10% by mass, based on the total mass of the regenerated polyester, based on the total mass of the regenerated polyester. When the copolymerization ratio of isophthalic acid is too large, the melting temperature is too low and the adhesiveness is lowered. Moreover, in order to obtain sufficient thermal adhesiveness when the fiber is used, the copolymerization ratio of isophthalic acid is preferably 4% by mass or more.

  The degree of polymerization of the oligomer is preferably 10 to 20, and the reaction rate is preferably 90 to 97%. The degree of polymerization is more preferably 18 to 20, and the reaction rate is more preferably 95 to 97%.

  In the method for producing a regenerated polyester of the present invention, recycled polyester, isophthalic acid and glycol are added to a first batch reactor in which a polyester oligomer is present in advance, and all dicarboxylic acids composed of dicarboxylic acid components and isophthalic acid which usually constitute recycled polyester are used. Glycol is supplied in a molar ratio of 1.0 to 2.0 with respect to 1 mol of the acid component. The esterification reaction carried out in the first batch reactor is usually performed at a temperature of 230 to 270 ° C. under a pressurized condition (pressure is preferably 0.18 to 0.20 MPa).

  The esterification step is substantially completed at the first batch reaction charge, and the resulting polyester oligomer is transferred to the second batch reactor of the next step. In the second batch reactor, the bisphenol group-containing compound is added, and the temperature is 250 to 300 ° C., particularly 270 to 300 ° C., and the pressure is 0.05 to 30 KPa in the presence of the polymerization catalyst. As the temperature and vacuum are increased, a polyester polymer with the target viscosity is synthesized.

  The regenerated polyester of the present invention may be added with inorganic particles, organic particles, and other various additives such as a complementary colorant, an antioxidant, and an antistatic agent, as long as the effects of the present invention are not impaired. it can.

  In the above production method, a polyester polymerization method having a two-tank configuration is shown as a batch reactor, but the reaction vessel is not limited to this.

  The bisphenol group-containing compound used in the present invention has the following general formula (1):

[In the above formula, R ¹ and R ² represent a hydrocarbon residue. X represents a sulfonyl group or a dimethylmethylene group. And an alkylene oxide adduct of bis (4-hydroxyphenyl) propane and an alkylene oxide adduct of bis (4-hydroxyphenyl) sulfone.

  In the present invention, 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane (BHPP) and 2,2-bis [4- (2-hydroxyethoxy) phenyl] sulfone (BHPS) are particularly preferable. As a form, it is preferable to heat-process beforehand at the temperature more than melting | fusing point from a handling property and a reactive point, and to add in a molten state.

  The copolymerization ratio of the bisphenol group-containing compound needs to be 2 to 9% by mass based on the total mass of the regenerated polyester. When the copolymerization ratio is less than 2% by mass, the resulting composite fiber has insufficient shrinkage characteristics. On the other hand, when the copolymerization ratio exceeds 9% by mass, the heat resistance is inferior. The addition amount of the bisphenol group-containing compound is preferably 3 to 8% by mass, more preferably 4 to 7% by mass.

  Examples of the polycondensation catalyst used in the present invention include manganese compounds, antimony compounds, and germanium compounds. Among them, antimony trioxide is preferably used. However, while antimony trioxide has excellent catalytic activity, metal antimony is precipitated during polycondensation, and foreign matter caused by metal antimony is generated. Therefore, in the present invention, the addition amount is based on the total mass of the polyester composition. 0.04% by mass or less is preferable.

  The polyester-based heat-bonded fibers thus obtained are made from recycled raw materials, are excellent in cost and adhesiveness, and are suitable for the production of nonwoven fabrics. In addition, the heat-bonding fiber may be made into a non-woven fabric by itself as a short fiber, and other fibers may be blended as a main fiber to make a non-woven fabric. However, from the viewpoint of heat resistance and recyclability, PET fiber is mainly used. preferable.

  Next, the method for producing the polyester of the present invention will be described more specifically with reference to examples. The measuring method of the characteristic value is as follows.

(1) Color tone (b value)
The color coordinate b value of Hunter's color difference formula in the Lab color system was measured for the polyester chip by a reflection method using a color meter (ColorCute i) manufactured by Suga Test Instruments. The b value represents a yellow-blue hue (+ is yellowish,-is blueish).

(2) Intrinsic viscosity (hereinafter abbreviated as IV)
Weigh 2.0 g of polyester, dissolve in orthochlorophenol at a concentration of 0.012 g / ml, cool to a temperature of 25 ° C., place 15 ml in an Ostwald viscometer, measure the falling seconds of the molten polymer, Intrinsic viscosity was calculated from the equation.
・ KI = KB × t
(Where KI is relative viscosity, KB is Ostwald viscometer count, and t is the number of seconds the sample solution flows at a temperature of 25 ° C.)
・ Before correction IV = 0.0242 × KI + 0.2634
-Intrinsic viscosity (IV) = IV x f before correction
(Here, f represents the standard chip reference value / standard chip measurement value number.)

(3) Diethylene glycol (DEG) content rate 2.5 ml of monoethanolamine was added to 1.0 g of the polyester, heated at a temperature of 250 ° C. for 40 minutes, and then the internal standard solution was added. Furthermore, a sample for measurement is prepared by adding terephthalic acid and ethanol. The DEG content rate was measured for this measurement sample using a gas chromatography GC-9A (Shimazu C-R3A) manufactured by Shimadzu Corporation.

(4) Softening point (SP)
The polyester chip was set in a softening point measuring machine, the temperature was raised, and the temperature at the time when the tip of the indenter fell into the chip was measured and indicated by SP (° C.).

Example 1
The first batch reactor comprises 2200 parts by weight of recycled polyester mainly composed of ethylene terephthalate units, 150 parts by weight of isophthalic acid (6% by weight based on the total weight of the obtained recycled polyester), and 950 parts by weight of ethylene glycol. The temperature rise was started simultaneously with the raw material charge, and the esterification reaction was started at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. Thereafter, the esterification reaction was completed after 3 hours and 30 minutes from the start of the reaction.

  The polyester oligomer as the reaction product at this time is transferred to the second batch reactor, and 178 parts by mass of BHPP (7% by mass based on the total mass of the obtained regenerated polyester) is added, and the temperature is 290 ° C. The polycondensation reaction was performed under reduced pressure (0.133 KPa or less). After 2 hours and 48 minutes, a polyester having an intrinsic viscosity of 0.665 was obtained. The results are shown in Table 1.

(Example 2)
The first batch reactor comprises 2200 parts by weight of recycled polyester mainly composed of ethylene terephthalate units, 150 parts by weight of isophthalic acid (6% by weight based on the total weight of the obtained recycled polyester), and 950 parts by weight of ethylene glycol. The temperature rise was started simultaneously with the raw material charge, and the esterification reaction was started at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. Thereafter, the esterification reaction was completed 3 hours and 33 minutes after the start of the reaction.

  The polyester oligomer as the reaction product at this time was transferred to the second batch reactor, and 183 parts by mass of BHPS (7% by mass based on the total mass of the obtained regenerated polyester) was added, and the temperature was 290 ° C. The polycondensation reaction was performed under reduced pressure (0.133 KPa or less). After 2 hours and 58 minutes, a polyester having an intrinsic viscosity of 0.669 was obtained. The results are shown in Table 1.

(Example 3)
The first batch reactor comprises 2200 parts by weight of recycled polyester mainly composed of ethylene terephthalate units, 150 parts by weight of isophthalic acid (6% by weight based on the total weight of the obtained recycled polyester), and 950 parts by weight of ethylene glycol. The temperature rise was started simultaneously with the raw material charge, and the esterification reaction was started at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. Thereafter, the esterification reaction was completed 3 hours and 32 minutes after the start of the reaction.

  The polyester oligomer as the reaction product at this time is transferred to the second batch reactor, and 97 parts by mass of BHPP (4% by mass based on the total mass of the obtained recycled polyester) is added, and the temperature is 290 ° C. The polycondensation reaction was performed under reduced pressure (0.133 KPa or less). After 2 hours and 42 minutes, a polyester having an intrinsic viscosity of 0.666 was obtained. The results are shown in Table 1.

(Example 4)
The first batch reactor comprises 2200 parts by weight of recycled polyester mainly composed of ethylene terephthalate units, 205 parts by weight of isophthalic acid (8% by weight based on the total weight of the obtained recycled polyester), and 950 parts by weight of ethylene glycol. The temperature rise was started simultaneously with the raw material charge, and the esterification reaction was started at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. Thereafter, the esterification reaction was completed 3 hours and 40 minutes after the start of the reaction.

  The polyester oligomer as the reaction product at this time is transferred to the second batch reactor, and 178 parts by mass of BHPP (7% by mass based on the total mass of the obtained regenerated polyester) is added, and the temperature is 290 ° C. The polycondensation reaction was performed under reduced pressure (0.133 KPa or less). After 2 hours and 50 minutes, a polyester having an intrinsic viscosity of 0.667 was obtained. The results are shown in Table 1.

(Comparative Example 1)
2200 parts by weight of recycled polyester mainly composed of ethylene terephthalate unit, 150 parts by weight of isophthalic acid (6% by weight based on the total weight of the obtained recycled polyester), 950 parts by weight of ethylene glycol, 178 parts by weight of BHPP (obtained recycled polyester) 7 mass% on the basis of the total mass of the first batch reactor, and the temperature rise is started at the same time as the raw materials are charged, and the esterification is performed at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. The reaction was started. Thereafter, the esterification reaction was completed after 3 hours and 15 minutes from the start of the reaction.

  The polyester oligomer which is the reaction product at this time was transferred to a second batch reactor, and a polycondensation reaction was performed under reduced pressure (0.133 KPa or less) at a temperature of 290 ° C. After 3 hours and 7 minutes, a polyester having an intrinsic viscosity of 0.668 was obtained. The results are shown in Table 1.

(Comparative Example 2)
The first batch reactor comprises 2140 parts by weight of recycled polyester mainly composed of ethylene terephthalate units, 150 parts by weight of isophthalic acid (6% by weight based on the total weight of the obtained recycled polyester), and 950 parts by weight of ethylene glycol. The temperature rise was started simultaneously with the raw material charge, and the esterification reaction was started at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. Thereafter, the esterification reaction was completed 3 hours and 32 minutes after the start of the reaction.

  The polyester oligomer as the reaction product at this time was transferred to the second batch reactor, and 262 parts by mass of BHPP (10% by mass based on the total mass of the obtained regenerated polyester) was reduced under reduced pressure at a temperature of 290 ° C. The polycondensation reaction was carried out at (0.133 KPa or less). After 2 hours and 58 minutes, a polyester having an intrinsic viscosity of 0.664 was obtained. The results are shown in Table 1.

(Comparative Example 3)
2140 parts by mass of recycled polyester mainly composed of ethylene terephthalate units, 150 parts by mass of isophthalic acid (6% by mass based on the total mass of the obtained recycled polyester), 950 parts by mass of ethylene glycol, and 255 parts by mass of BHPP (obtained recycled polyester) Is charged into the first batch reactor, and the temperature rise is started at the same time as the raw materials are charged. Esterification is performed at a temperature of 245 ° C. and a pressure of 0.18 to 0.20 MPa. The reaction was started. Thereafter, the esterification reaction was completed 3 hours and 10 minutes after the start of the reaction.

  The polyester oligomer which is the reaction product at this time was transferred to a second batch reactor, and a polycondensation reaction was performed under reduced pressure (0.133 KPa or less) at a temperature of 290 ° C. After 3 hours and 20 minutes, a polyester having an intrinsic viscosity of 0.669 was obtained. The results are shown in Table 1.

  From Table 1 above, in Examples 1 to 4 of the present invention, by defining the isophthalic acid copolymerization ratio, the bisphenol group-containing compound copolymerization ratio, and the addition timing, the color tone is compared with Comparative Examples 1 to 3. Good improvement and DEG content.

  The recycled polyester produced in the present invention can be used in the textile field such as for clothing such as fibers, woven and knitted fabrics and nonwoven fabrics, and for industrial use.

Claims (3)

In a method for producing a regenerated polyester, a recycled polyester mainly composed of an ethylene terephthalate unit is supplied to an esterification step together with isophthalic acid and glycol to obtain an oligomer, and then is produced by polycondensation of the oligomer in a polycondensation step. A bisphenol group-containing compound represented by the following general formula (1) is added in an amount of 2.0 to 9.0% by mass based on the total mass of the regenerated polyester, from the end of the esterification step to the start of the polycondensation step. A method for producing recycled polyester, characterized in that:
[In the above formula, R ¹ and R ² represent a hydrocarbon residue. X represents a sulfonyl group or a dimethylmethylene group. ]   The method for producing a regenerated polyester according to claim 1, wherein the isophthalic acid is supplied to the depolymerization step in an amount of 4.0 to 16.0% by mass based on the total mass of the regenerated polyester.   The bisphenol group-containing compound is 2,2-bis [4- (2-hydroxyethoxy) phenyl] propane or 2,2-bis [4- (2-hydroxyethoxy) phenyl] sulfone, and in the molten state, the ester The method for producing a regenerated polyester according to claim 1, wherein the regenerated polyester is added between the end of the conversion step and the start of the polycondensation step.