JPH1121341A - Preparation of modified polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a modified polyester having a low content of foreign matter, a high yarn producibility and a good dyeability to cation dyes. SOLUTION: To prepare the modified polyester in which ethylene terephthalate units account for >=80 mol.% of the structure units and metal- sulfonate-group-containing ethylene isophthalate units account for from 1 to 5 mol.% of the structural units, through direct esterification, an oligomer principally comprising ethylene terephthalate units, with the average degree of polymerization of <=5, is maintained at the melt state at 230 deg.C or lower. Subsequently, an ethylene glycol solution of the metal-sulfonate-group-containing isophthalic acid component, with its pH adjusted to from 6.8 to 8.0, is added to this oligomer. Then, the reaction mixture is allowed to undergo polycondensation at 275 deg.C or lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a modified polyester having a low foreign matter content, a good yarn-making property and an excellent dyeability of a cationic dye.

[0002]

2. Description of the Related Art Polyethylene terephthalate (PET)
Are excellent in mechanical properties and chemical properties, are used in a wide range of fields, and have a very wide use especially as synthetic fibers.

[0003] However, the PET fiber has a problem that the dyeability is not good, and it can be dyed only with a disperse dye, and the dyed product lacks sharpness. Conventionally, in order to solve this drawback, it has been widely practiced to copolymerize PET with an isophthalic acid component having a metal sulfonate group (hereinafter abbreviated as SIP component) to obtain a modified polyester dyeable with a cationic dye. . It is also known that copolymerization of an isophthalic acid component or an adipic acid component with PET together with a SIP component results in a readily dyeable modified polyester (Japanese Patent Publication No. 55-20505, Japanese Patent Application Laid-Open No. 61-239015). No.).

However, when PET is produced by copolymerizing such SIP components by the direct esterification method which is currently the mainstream of polyester production, there is a problem that foreign matters insoluble in the polymer are apt to be generated. When such foreign matter is present in the polymer, the melt-spinning causes a rapid increase in filtration pressure and frequent occurrence of yarn breakage, deteriorating the spinnability. In particular, when a polyester fiber that can be dyed with a cationic dye under normal pressure is manufactured, this tendency is remarkable because it is necessary to increase the copolymerization ratio of the SIP component.

As a method for solving this problem, Japanese Patent Publication No.
No. 57054 discloses that when a modified polyester is produced by a direct esterification method, a P having an average degree of polymerization of 2 to 9 is used.
A method has been proposed in which a specific SIP component is added to an ET oligomer to perform polycondensation. According to this method, the formation of foreign matter in the polymer can be considerably suppressed, but the effect is not sufficient.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a modified polyester having a low foreign matter content, a good yarn-making property and an excellent dyeability of a cationic dye. .

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the invention is that 80% by mole or more of the constituent units are ethylene terephthalate units, and 1 to 5% by mole of metal sulfonate. When the modified polyester, which is an ethylene isophthalate unit having a group, is produced by a direct esterification method, an oligomer mainly composed of an ethylene terephthalate unit is adjusted to an average degree of polymerization of 5 or less, and a temperature of 2
Production of a modified polyester characterized by maintaining a molten state of 30 ° C or lower, adding an ethylene glycol solution of a SIP component adjusted to pH 6.8 to 8.0 to the mixture, and performing polycondensation at a temperature of 275 ° C or lower. In the way.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The method of the present invention relates to a direct esterification method, that is, a method of adding a SIP component to an oligomer obtained by an esterification reaction of terephthalic acid and ethylene glycol and subjecting the oligomer to polycondensation to produce a modified polyester. Things.

The modified polyester of the present invention comprises at least 80 mol%, preferably 87 to 93 mol% of the constituent units.
Is an ethylene terephthalate unit, 1 to 5 mol%,
Preferably, 1.5 to 3.5 mol% is an ethylene isophthalate unit having a metal sulfonate group.

When the amount of the SIP component is less than 1 mol%, the dyeability with the cationic dye is insufficient. On the other hand, when the amount of the SIP component exceeds 5 mol%, the melt viscosity of the polyester becomes high, so that the degree of polymerization is sufficiently increased. Therefore, it is difficult to obtain a fiber having a strength that can be practically used.

In order to obtain a polyester fiber which can be dyed with a cationic dye at normal pressure, an isophthalic acid component or an aliphatic dicarboxylic acid component (second copolymerization component) is required together with a SIP component.
Is preferably copolymerized in an amount of 1 to 15 mol% based on the total acid component.

When the second copolymerization component is copolymerized, if the amount is less than 1 mol%, the effect of dyeing under normal pressure is not sufficiently exhibited, while if the amount exceeds 15 mol%, the fiber may be damaged. When the fabric is subjected to thermal transfer printing or the like, the fabric shrinks and the texture becomes hard.

Examples of the SIP component used in the present invention include a dialkyl ester of isophthalic acid having a metal sulfonate group (hereinafter abbreviated as SIPM) and a diethylene glycol ester of isophthalic acid having a metal sulfonate group (hereinafter abbreviated as SIPG). Can be

Each of these can be used alone. However, when a mixture of SIPM and SIPG at a molar ratio of 58/42 to 26/74 is used, the SIP component easily and uniformly dissolves in the reaction system, and It is preferable because reactivity is good.

The mixture of SIPM and SIPG is SIP
M and SIPG can be obtained as a mixture.
It can also be obtained by adjusting the reaction rate of transesterification by transesterification between M and ethylene glycol.

As isophthalic acid having a metal sulfonate group forming SIPM and SIPG, 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid and 5-lithium sulfoisophthalic acid are preferably used.

The SIP component is suitably added to the reaction system as an ethylene glycol solution having a concentration of 30 to 40% by weight.

As the second copolymerization component, an aliphatic dicarboxylic acid such as isophthalic acid or adipic acid, sebacic acid, azelaic acid or dimer acid is used.

In order to carry out the method of the present invention, first, terephthalic acid and ethylene glycol are directly esterified by a conventional method to obtain bis- (β-hydroxyethyl) terephthalate and its low polymer (BHET oligomer). .

When copolymerizing the second copolymerization component, isophthalic acid or aliphatic dicarboxylic acid is simultaneously reacted to form a copolymerized oligomer, or isophthalic acid or aliphatic dicarboxylic acid and ethylene glycol are added to a BHET oligomer. To make a copolymerized oligomer. (BH
The ET oligomer may be separately mixed with an oligomer obtained by esterifying isophthalic acid or an aliphatic dicarboxylic acid with ethylene glycol. )

In the present invention, a modified polyester is obtained by adding a SIP component to the above-mentioned oligomer and subjecting it to polycondensation. When the SIP component is added, the average degree of polymerization of the oligomer is 5 or less, preferably 4 or less. Below and the temperature is 230 ℃
Hereinafter, it is necessary to set the temperature to preferably 200 to 220 ° C.

Industrially, a BHET oligomer having a relatively high degree of polymerization having an average degree of polymerization of about 7 to 10 is produced by a direct esterification reaction, and this is depolymerized with ethylene glycol to lower the average degree of polymerization. A method is preferably employed. When the second copolymer component is copolymerized, BHET
It is preferred that isophthalic acid or aliphatic dicarboxylic acid and ethylene glycol be added to the oligomer to cause a reaction, and the esterification reaction and the depolymerization reaction be performed simultaneously.

There is a relationship between the polymerization degree and temperature of the oligomer when the SIP component is added and the amount of foreign matters derived from the SIP component, and the average polymerization degree of the oligomer exceeds 5 or the temperature exceeds 230 ° C. If so, the amount of foreign matter generated increases. In addition, unless the average degree of polymerization of the oligomer is 5 or less, the temperature at the time of adding the SIP component cannot be sufficiently lowered.

Further, by forming the SIP component into an ethylene glycol solution and adjusting the pH to 6.8 to 8.0, preferably 7.0 to 7.6, and then adding it to the oligomer, the generation of foreign substances can be suppressed. If this pH is less than 6.8, S
The effect of suppressing the generation of foreign matter due to the IP component is insufficient, while if the pH exceeds 8.0, the alkali metal compound for adjusting the pH becomes difficult to be compatible with the polymer, and thus the alkali metal compound causes Undesirably, foreign matter is generated.

P of ethylene glycol solution of SIP component
For the H adjustment, it is appropriate to use an alkali metal hydroxide, an organic carboxylate, an alcoholate, an inorganic weak acid salt or the like, and specifically, sodium, potassium, lithium hydroxide, formate, acetate. , Methylates, ethylates, butyrates, carbonates, bicarbonates, borates, etc., among which lithium acetate having good solubility in polymers is preferably used.

The polycondensation reaction needs to be performed at a temperature of 275 ° C. or less. When the temperature of the polycondensation reaction is higher than this, the color tone of the polyester is significantly deteriorated. In addition,
If the temperature of the polycondensation reaction is too low, the rate of the polycondensation reaction is low, which is impractical.

The polycondensation reaction is carried out in the presence of a catalyst, and examples of the catalyst include antimony, germanium, tin, titanium, zinc, aluminum, magnesium, calcium, manganese, cobalt, etc., which are generally used in the production of polyester. In addition to metal compounds, sulfosalicylic acid, o
-Organic sulfonic acid compounds such as sulfobenzoic anhydride are preferably used.

The amount of the catalyst to be added is 1 × 10 ^-5 to 1 × 10 ^-2 mol, preferably 5 × 10 ^{-5 to} 5 × 10 ^-3 mol, optimally for 1 mol of the acid component constituting the polyester. Is 1 × 10 ^{-4 to} 3 ×
10 ^-3 mol.

In the present invention, additives such as stabilizers such as hindered phenol compounds, color improvers such as fluorescent agents and dyes, matting agents such as titanium dioxide and pigments may be added. Absent.

The modified polyester obtained by the method of the present invention can be converted into a fiber dyeable with a cationic dye by spinning in a conventional manner.

In order to efficiently produce fibers, it is desirable to employ a direct spinning drawing method or a high-speed spinning method, and to carry out high-speed spinning at a winding speed of 3000 m / min or more.

For example, when the modified polyester is
Melt spinning at a spinning temperature of preferably 295-305 ° C,
After cooling and solidifying, apply a spinning oil and take up at a speed of about 1200 m / min and continuously stretch and wind it, or take up a partially oriented yarn (POY) at a speed of 3000 m / min or more and wind it as it is Or it is stretched continuously and then wound up. When winding the POY, it is stretched in a separate step or stretched false twisting,
Used as a woven or knitted fabric.

If the yarn is formed using a modified polyester obtained by copolymerizing the second copolymer component with the SIP component, a polyester fiber which can be dyed with a cationic dye at normal pressure is obtained.

The polyester fiber thus obtained can be dyed with a cationic dye, and can be a clear dyed product. In addition, a dye which can be dyed under normal pressure can be dyed under normal pressure, so that the dyeing cost can be reduced and wool or the like is not damaged at the time of dyeing even when mixed with wool or the like.

[0036]

In the present invention, since the SIP component is added to the oligomer having a low degree of polymerization and a low temperature, it is recognized that the modification of the SIP component is suppressed and the generation of foreign substances is suppressed. In addition, when an acidic SIP component is added to the oligomer, it is considered that local gelation occurs temporarily and foreign matter is generated. However, in the present invention, since the acidity of the SIP component is neutralized and added to the oligomer, the SIP component is added. It is considered that the generation of foreign matter due to the acidity of the component can be prevented. Furthermore, when an acidic SIP component is added, a diethylene glycol bond is easily produced as a by-product. However, in the present invention, since the SIP component is neutralized and added, the by-product of the diethylene glycol bond is suppressed. Since the modified polyester obtained by the method of the present invention has a small amount of foreign matter, the rise of the pack pressure during spinning is suppressed, the yarn breakage is small, and the yarn forming property is good. Therefore, the spinning properties of spinning fine yarn and high-speed spinning, which have been a problem in the production of cationic dye dyeable polyester fibers, are greatly improved.

[0037]

Next, the present invention will be described specifically with reference to examples. The methods for measuring and evaluating characteristic values and the like in the examples are as follows. (a) Average degree of polymerization of oligomer (Pn) The saponification value (SN) and acid value (AV) of the oligomer were measured and calculated by the following equation. Pn = (0.0173 × SN) / (32.21−0.05508 × SN + 0.02531)
× AV) SN was determined by adding an excess alcoholic alkali solution to the oligomer, performing saponification, and back titrating the excess alkali with an acid to obtain the number of mg of potassium hydroxide consumed per 1 g of the oligomer. AV dissolves the oligomer in pyridine,
Titration was performed with an alkali solution, and the titer was determined as the number of mg of potassium hydroxide consumed per gram of the oligomer. (b) Intrinsic viscosity The intrinsic viscosity was measured at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (c) Content of ether bond in polymer (D%) After alkali hydrolysis of polymer, ethylene glycol and diethylene glycol were quantified by gas chromatography, and determined as mol% of diethylene glycol based on the total of ethylene glycol and diethylene glycol. . (d) Number of foreign substances in the polymer 400 mg of the polymer was melted on a slide glass, and the number of aggregates having a size of 4 μm or more was counted by microscopic observation. (e) Spinnability The following three grades were used to evaluate the number of times of thread cutting when spinning with 16 weights for 12 hours. ： １: 1 time or less, Δ: 2 to 4 times, ×: 5 times or more (f) Strong elongation Measured using Orientic Tensilon UTM-4-100 at a sample length of 50 cm and a tensile speed of 50 cm / min. . (g) Exhaustion rate Dye: Astrazon Blue FRR (Bayer Cationic Dye) 1.5% owf Auxiliary: Acetic acid 0.6 ml / l, Sodium acetate 0.6 g / l Bath ratio: 1/100 Under the above conditions, the dyeing residue after dyeing under normal pressure boiling for 30 minutes is spectrophotometer manufactured by Hitachi, Ltd.
Using a BPS-3T type, the absorbance U was measured at a wavelength λ = 590 μm, and the exhaust rate was determined from U and the absorbance U0 of the undiluted solution by the following equation. Exhaust rate (%) = [(U0-U) / U0] x 100 (h) Texture Weaving and scouring plain weave with a density of 75 pieces / 2.54cm
The fabric after heat setting at 190 ° C. was evaluated in the following three stages by a sensory test. ◎: extremely good, ○: good, ×: bad

Example 1 A slurry of terephthalic acid and ethylene glycol in a molar ratio of 1 / 1.6 was continuously supplied to an esterification reactor in which bis (β-hydroxyethyl) terephthalate and its oligomer were present, and the slurry was stirred at normal pressure for 250 minutes. The esterification reaction was carried out at a temperature of 5 ° C. with a residence time of 6 hours, and the average
Of BHET oligomers were continuously obtained. This BHET oligomer (1580 kg) was charged into a polycondensation reactor, and adipic acid (62 kg) and ethylene glycol (411 kg) were added thereto to carry out an esterification reaction and a depolymerization reaction. To 210 ° C. to obtain a copolymerized oligomer having an average degree of polymerization of 4.3. 2.5 × 10 ^-4 mol of antimony trioxide is added to 1 mol of the acid component to this copolymerized oligomer, and then 3,5-di (carbo-β
-Hydroxyethoxy) sodium benzenesulfonate and dimethyl 5-sodium sulfoisophthalate in 6 /
A solution adjusted to pH 7.6 by adding lithium acetate to an ethylene glycol solution having a concentration of 35% by weight and containing a molar ratio of 4 was added so that the SIP component became 2.5 mol% of the total acid component, and the solution was placed in a polycondensation reactor. And finally 0.5 Torr,
The polycondensation was performed at a temperature of 270 ° C. for 6 hours. The resulting modified polyester has a good color tone, an intrinsic viscosity of 0.58, and a D% of 2.0.
The mole% and the number of foreign substances were 12. This modified polyester is melt-spun at a spinning temperature of 302 ° C. and a discharge rate of 17.4 g / min. After cooling and solidifying, a spinning oil is applied and taken up with a godet roller at a speed of 1200 m / min. Was stretched 2.7 times between a roller having a temperature of 140 ° C. and a roller having a temperature of 140 ° C., and was heat-treated and wound at a speed of 3240 m / min to obtain a filament yarn of 50 d / 36 f. There was no thread breakage in spinning for 16 hours and about 12 hours, and the spinning property was good. Table 1 shows the properties and the like of the obtained yarn.

Examples 2 to 8 and Comparative Examples 1 to 5 Polyester was produced and produced by a method similar to that of Example 1 except for the conditions shown in Table 1. Table 1 shows the results.

[0040]

[Table 1]

In each of the examples, the yarn formability was good. On the other hand, in Comparative Example 1, the degree of polymerization of the oligomer when the SIP component was added was high, and in Comparative Example 2, the temperature of the oligomer when the SIP component was added was high. As a result, foreign matter caused by the SIP component was generated, and as a result, the rate of increase of the pack pressure during melt spinning was high, and the number of yarn breaks increased, resulting in very poor spinnability. In Comparative Example 3, the amount of lithium acetate added to neutralize the SIP component was large, and lithium acetate was precipitated without being compatible with the polymer, resulting in poor spinnability.
In Comparative Example 4, since the solution of the SIP component was acidic,
Foreign matters were generated due to the components, D% was large, and in Comparative Example 5, the color tone of the polyester was extremely poor due to the high temperature of the polycondensation reaction.

[0042]

According to the present invention, the content of foreign matter is small,
It is possible to produce a modified polyester having a good spinning property and excellent dyeability of a cationic dye.

Claims (2)

[Claims] 1. A modified polyester in which at least 80 mol% of constituent units are ethylene terephthalate units and 1 to 5 mol% of ethylene isophthalate units having a metal sulfonate group are produced by direct esterification. An oligomer mainly composed of terephthalate units having an average degree of polymerization of 5 or less, kept in a molten state at a temperature of 230 ° C. or less, and adjusted to a pH of 6.8 to 8.0 with an ethylene glycol solution of an isophthalic acid component having a metal sulfonate group. A method for producing a modified polyester, the method comprising adding and polycondensing at a temperature of 275 ° C. or less. 2. An oligomer having an ethylene terephthalate unit as a main component, based on all the acid components of the polyester,
Isophthalic acid component or aliphatic dicarboxylic acid component from 1 to 15
The method for producing a modified polyester according to claim 1, wherein the modified polyester is used.