JP2000281768A - Preparation of modified polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excellently productive method for manufacturing a modified polyester while suppressing the occurrence of diethylene glycol as a by-product which causes deterioration of characteristics of a polyester in manufacturing a modified polyester useful for a fiber dyeable with a basic dye. SOLUTION: A modified polyester containing at least 80 mole % of ethylene terephthalate constituting unit and 0.5-8 mole % of ethylene isophthalate constituting unit having a sulfonate salt group is manufactured. In this case, a dialkyl isophthalate ester having a sulfonate salt group, a 5 wt.% aqueous solution of which has a pH of at least 4.0, is added to a polyester oligomer composed mainly of an ethylene terephthalate unit, and the resultant mixture is kept at 240 deg.C or below for at least 10 min and subsequently subjected to polycondensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing a polyester having a sulfonate group dyeable on a basic dye.

[0002]

2. Description of the Related Art Polyester, particularly polyethylene terephthalate (hereinafter abbreviated as PET) is used for fibers for clothing, industrial use, etc., as well as for magnetic tapes and capacitors, because of its excellent mechanical and chemical properties. Is widely used for molded products such as films or bottles.
However, polyester cannot be said to have good dyeing properties as clothing fibers, and dyeing with a disperse dye is common.

[0003] Conventionally, as a method of compensating for such a drawback,
A polyester dyeable to a basic dye by copolymerizing a polyester with isophthalic acid having a sulfonic acid group (hereinafter, referred to as
Method for producing modified polyester
No. 34-10497) is known.

However, terephthalic acid (hereinafter referred to as TP), which is generally used as an industrially advantageous method today,
A) and ethylene glycol (hereinafter abbreviated as EG) as starting materials, when the above method is applied to a direct esterification method, diethylene glycol (hereinafter abbreviated as DEG) during the esterification reaction and the polycondensation reaction. ) By-produced in a large amount and copolymerized, thereby causing a problem that the mechanical properties, heat resistance, ultraviolet light resistance, hydrolysis resistance and the like of the modified polyester are remarkably reduced.

As a method of improving this, it is known to add an alkali metal acetate or carbonate to the reaction system. However, when a large amount of the alkali metal salt is added, insoluble components in the modified polyester are removed. It is easy to produce, and when spinning the resulting modified polyester, there remains a problem that the pressure of the spin pack is increased quickly and yarn breakage occurs frequently.

Therefore, as a method of suppressing the by-product of DEG, for example, Japanese Patent Publication No. 57-57054 discloses TPA and EG.
And the degree of polymerization of bis- (β-hydroxyethyl) terephthalate and / or a low polymer thereof (hereinafter abbreviated as PET oligomer) obtained by direct esterification method from
A method has been proposed in which bis (β-hydroxyethyl) ester of isophthalic acid (hereinafter abbreviated as SIPG) having a sulfonate group having a transesterification rate of 40 to 65% is added.

However, since SIPG is usually produced by once producing a dialkyl ester of isophthalic acid having a sulfonate group and reacting it with EG, there is a problem that the raw material cost is increased. In addition, when the transesterification rate of SIPG fluctuates, SI
The molecular weight of PG fluctuates, causing a variation in the copolymerization amount of the isophthalic acid component having a sulfonate group in the modified polyester, and when the resulting modified polyester is fiberized, the uniformity of dyeing is impaired. There is.

Japanese Patent Publication No. 59-1735 proposes a method of adding a dialkyl ester of isophthalic acid having a sulfonate group to a PET oligomer having a specific conversion. However, since the dialkyl ester of isophthalic acid having a sulfonate group has low solubility in the PET oligomer, the dialkyl ester of isophthalic acid having a sulfonate group precipitates during the polycondensation reaction, and the rate of the polycondensation reaction is reduced, and the reaction time is reduced. And the color tone of the resulting modified polyester deteriorates.

[0009]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and reduces the by-product of DEG, which causes deterioration of physical properties, and provides a basic dye having excellent productivity. It is an object of the present invention to provide a method for producing a modified polyester.

[0010]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, in the present invention, when producing a modified polyester in which at least 80 mol% of the constituent units are ethylene terephthalate units and 0.5 to 8 mol% are ethylene isophthalate units having a sulfonic acid salt group, the ethylene terephthalate unit is mainly used. A dialkyl ester of isophthalic acid having a sulfonate group having a pH of 4.0 or more in a 5% by weight aqueous solution is added to the polyester oligomer to be subjected to polycondensation at a temperature of 240 ° C or less for 10 minutes or more. The gist of the invention is a method for producing a characteristic modified polyester.

[0011]

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

In the modified polyester of the present invention, it is necessary that at least 80 mol%, preferably 90 mol% or more of the constituent components are ethylene terephthalate units.
If the ethylene terephthalate unit is less than 80 mol%,
It is not preferable because good physical properties of the polyester may be impaired.

Further, in order to make the polyester dyeable to a basic dye, it is necessary that the ethylene isophthalate unit having a sulfonate group is 0.5 to 8 mol%, preferably 1 to 6 mol%. When the proportion of the ethylene isophthalate unit having a sulfonate group is less than 0.5 mol%, sufficient dyeability cannot be obtained. On the other hand, when it exceeds 8 mol%, the melt viscosity of the obtained modified polyester becomes high. It is difficult to sufficiently increase the degree of polymerization, and as a result, a sufficient yarn strength cannot be obtained. In addition, as long as the essential effects of the present invention are not impaired,
In addition to the above, a small amount of a copolymer component may be contained.

Examples of such a copolymer component include aromatic dicarboxylic acid components such as isophthalic acid, phthalic anhydride, and naphthalenedicarboxylic acid; aliphatic dicarboxylic acid components such as adipic acid and sebacic acid; propylene glycol; Examples include glycol components such as 4-cyclohexanedimethanol and 1,4-butanediol, and hydroxycarboxylic acid components such as 4-hydroxybenzoic acid and ε-caprolactone.

The present invention is directed to a direct esterification method using TPA and EG as starting materials, a lower alkyl ester of TPA and E
Although it is possible to use a PET oligomer produced by either of the transesterification methods using G as a starting material, it is preferable to use a PET oligomer produced by a direct esterification method from the viewpoint of cost merit and the like. .

In general, PE of the direct esterification method is used.
The T oligomer has a higher average degree of polymerization than the PET oligomer obtained by the transesterification method and may have a melting point higher than 240 ° C. Therefore, the PET oligomer solidifies when the dialkyl ester of isophthalic acid having a sulfonic acid group is added. Therefore, it is preferable to depolymerize the PET oligomer with EG in advance and sufficiently lower the melting point.

Next, the dialkyl ester of isophthalic acid having a sulfonate group used in the present invention is:
The pH of the 5% by weight aqueous solution needs to be 4.0 or more. If this value is less than 4.0, the amount of by-product DEG increases, and the physical properties of the resulting modified polyester deteriorate.

Usually, in the process of producing a dialkyl ester of isophthalic acid having a sulfonate group, DEG
Although various substances that promote the by-products of by-products are mixed as by-products, it is industrially difficult to identify and eliminate all of these substances. Therefore, conventionally, alkali metal acetates, carbonates, and the like are added to the reaction system to eliminate the influence of these substances, or by using SIPG or the like.
Although a method has been adopted in which the reaction proceeds under conditions in which G is unlikely to be produced as a by-product, it has the problems described above.

However, according to the study of the present inventors, when a 5% by weight aqueous solution having a pH of 4.0 or more is used, the influence of these substances is substantially eliminated, and the by-product of DEG can be suppressed. It becomes. Specific examples of the dialkyl ester of isophthalic acid having a sulfonic acid group as described above include dimethyl 5-sodium sulfoisophthalate (hereinafter abbreviated as SIPM-Na) and dimethyl 5-potassium sulfoisophthalate (hereinafter, SIPM-Na). K), dimethyl 5-lithium sulfoisophthalate (hereinafter abbreviated as SIPM-Li) and the like. These are 30-40% by weight EG
It is suitably used as a slurry, and in order to maintain fluidity over a long period of time, it is preferable to maintain the temperature of the slurry at 50 to 80 ° C.

Next, in the present invention, after adding a dialkyl ester of isophthalic acid having a sulfonate group to the PET oligomer, the temperature is 240 ° C. or lower, preferably 220 ° C. or lower.
It is necessary to hold at a temperature of 240 ° C. for 10 minutes or more, preferably 15 minutes to 60 minutes. This step is necessary for promoting the transesterification reaction of the dialkyl ester of isophthalic acid having a sulfonate group and increasing the solubility in the PET oligomer. If the temperature at this time exceeds 240 ° C., it is not preferable because the amount of by-product DEG increases and the physical properties of the resulting modified polyester deteriorate. On the other hand, if the time at this time is less than 10 minutes, the transesterification of the dialkyl ester of isophthalic acid having a sulfonic acid group becomes insufficient, and the dialkyl ester of isophthalic acid having a sulfonic acid group precipitates during the polycondensation. As a result, the polycondensation reaction rate becomes slow, the reaction time becomes long, and the color tone of the resulting modified polyester deteriorates.

The lower limit of the holding temperature and the upper limit of the holding time are not particularly limited. However, if the holding temperature is lower than 220 ° C., the PET oligomer tends to solidify,
If the holding time exceeds 60 minutes, the effect tends to be saturated, which is not preferable.

The method for producing the modified polyester of the present invention can be carried out, for example, as follows. First, the temperature
Under a nitrogen gas control at 230 to 250 ° C., the EG / TPA molar ratio of 1.1 was added to the esterification reactor in which the PET oligomer was present.
~ 2.0 slurries and a residence time of 7-8 hours, P
The ET oligomer is obtained continuously. Next, the PET oligomer is transferred to a polymerization reactor, and if necessary, 5 to 15% by weight of EG is added to perform depolymerization, and 30 to 40% by weight of a dialkyl ester of isophthalic acid having a sulfonate group is added. Add a predetermined amount of EG slurry, and add
Hold for 30 minutes with stirring. Then, the temperature of the polymerization reactor is raised to 270 to 280 ° C., and a polycondensation reaction is performed under reduced pressure of 0.01 to 13.3 hPa until a modified polyester having a predetermined intrinsic viscosity is obtained.

The polycondensation reaction is usually carried out in the presence of a catalyst. As the catalyst, conventionally used metal compounds such as antimony, germanium, tin, titanium, zinc, aluminum, magnesium, calcium, manganese, cobalt, etc. Is preferably used. The addition amount of such a catalyst is 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol, preferably 5 × 10 ^{−5 to} 5 ×, per 1 mol of the acid component constituting the polyester.
It is in the range of 10 ^-3 mole, optimally 1 x 10 ^{-4 to} 3 x 10 ^-3 mole.

In the present invention, additives such as a hindered phenol compound, a stabilizer such as a phosphorus compound, a cobalt compound, a fluorescent agent, a color tone improver such as a dye, and a pigment such as titanium dioxide are contained. Is also good.

In the present invention, when an alkali metal compound is added at the same time as or before the addition of the dialkyl ester of isophthalic acid having a sulfonic acid salt group, it is possible to further suppress the by-product of DEG, thereby achieving high quality. Is preferred because a modified polyester of the formula (1) is obtained.

As the alkali metal compound used at this time, hydroxide, organic carboxylate, alcoholate, inorganic weak acid salt and the like are suitable. Specifically, sodium, potassium, lithium hydroxide, formate, aliphatic carboxylate such as acetate, methylate, ethylate, butyrate,
Carbonates, bicarbonates, borates and the like.
The amount of the alkali metal compound to be added is preferably 5 × 10 ⁻³ mol or less per 1 mol of the acid component constituting the polyester in order to prevent insoluble components from being produced in the polyester.

[0027]

According to the present invention, the present inventors presume as follows that a modified polyester which can be dyed to a basic dye with a small decrease in physical properties due to by-product DEG can be obtained with high productivity. I have. In the present invention, a dialkyl ester of isophthalic acid having a sulfonate group having a pH of 4.0 or more in a 5% by weight aqueous solution is used as a raw material for making a basic dye dyeable. Conventionally, attention has been paid to reducing the amount of impurities contained in such raw materials, but not all of the impurities contribute to the by-product of DEG; Is not preferable because the production cost increases. On the other hand, it is industrially extremely difficult to identify and eliminate only the substance that promotes the by-product of DEG. According to the study of the present inventors,
PH of aqueous solution of dialkyl ester of isophthalic acid having sulfonate group and D in the resulting modified polyester
It has been found that the EG content is closely related. From this fact, the use of a dialkyl ester of isophthalic acid having a sulfonate group in which the pH of a 5% by weight aqueous solution is 4.0 or more is contained without special purification or addition of an additive or the like to the reaction system. The effect of the substance that promotes the by-product of DEG is substantially eliminated, and the DEG content in the resulting modified polyester can be reduced to a practically acceptable level.

In the present invention, the isophthalic acid-containing isophthalic acid-containing diphthalic acid ester is added to the PET oligomer and then maintained under the conditions described in the claims. The transesterification reaction of the acid dialkyl ester can proceed, and it is possible to prevent the dialkyl ester of isophthalic acid having a sulfonic acid salt group from being precipitated during the polycondensation reaction, thereby preventing the polycondensation reaction rate from decreasing.

[0029]

Next, the present invention will be described in detail with reference to examples. In addition, the measurement of the characteristic value in an example was performed as follows. (a) pH of an aqueous solution Dissolve 5 g of a dialkyl ester of isophthalic acid having a sulfonate group in 95 g of water at 50 ° C. and leave it in a constant temperature water bath at 30 ° C. to adjust the pH when the liquid temperature reaches 30 ° C. It was determined using a pH meter L-7LC manufactured by KK. (b) Intrinsic viscosity [η] Using an equal weight mixed solvent of phenol and ethane tetrachloride,
It was measured at a temperature of 20 ° C. (c) DEG content (D%) After the polyester was alkali-hydrolyzed, it was determined using a gas chromatograph GC-9A manufactured by Shimadzu Corporation. This value
If it is at most 3.0 mol%, the effect on the physical properties of the polyester will be at a level at which there is no practical problem. (d) Color tone (b value) It was measured using an ND- # 80 type color difference meter manufactured by Nippon Denshoku Industries Co., Ltd. The b value is a yellow-blue hue (+ side is yellowish,-side is bluish)
, And the smaller the better, unless it is extremely small.

Example 1 A slurry of EG and TPA having a molar ratio of 1 / 1.6 was continuously supplied to an esterification reactor in which a PET oligomer was present at a temperature of 250 ° C., a pressure of 0.1 MPaG, and a residence time of 8 hours. The esterification reaction was performed to continuously obtain a PET oligomer having a conversion of 95%.

48.0 kg of this PET oligomer was transferred to a polycondensation reactor, and the temperature was adjusted to 230 ° C.
Antimony trioxide was added in an amount of 2.0 × 10 ^-4 mol per mol of the acid component to an amount of 0.4% by weight and triethyl phosphate.
1.0 × 10 ^-4 mol was added. And the pH of 5% by weight aqueous solution
Of a 35 wt% EG slurry of SIPM-Na having a
-Na is added in an amount of 5.0 mol% with respect to the acid component.
Hold at 30 ° C. with stirring for 30 minutes.

Next, the temperature inside the polycondensation reaction vessel was raised for 30 minutes.
While raising the temperature to 275 ° C, the pressure was gradually reduced and after 1 hour 1.
2 hPa or less. Under these conditions, a polycondensation reaction was carried out for 2 hours while stirring, and the resulting modified polyester was discharged and pelletized by a conventional method.

Example 2 48.0 kg of a PET oligomer obtained in the same manner as in Example 1 was transferred to a polycondensation reactor, 5.5 kg of EG was added, and depolymerization was carried out for 1 hour while gradually lowering the temperature. Next, 220 ℃
Titanium dioxide to the depolymerized PET oligomer of
Antimony trioxide was added in an amount of 2.0 × 10 ^-4 mol per mol of the acid component to an amount of 0.4% by weight and triethyl phosphate.
1.0 × 10 ^-4 mol was added. And the pH of 5% by weight aqueous solution
Of a 35 wt% EG slurry of SIPM-Na having a
-Na is added in an amount of 7.0 mol% with respect to the acid component.
Hold at 45 ° C. with stirring for 45 minutes.

Next, the temperature inside the polycondensation reaction vessel was raised for 30 minutes.
While raising the temperature to 275 ° C, the pressure was gradually reduced and after 1 hour 1.
2 hPa or less. Under these conditions, a polycondensation reaction was carried out for 2 hours while stirring, and the resulting modified polyester was discharged and pelletized by a conventional method.

Example 3 Example 1 was repeated except that 30 × 10 ^-4 mol of sodium acetate was added in advance to 1 mol of the acid component before adding SIPM-Na.
The same was done.

Examples 4-6, Comparative Examples 1-4 Types of dialkyl ester of isophthalic acid having sulfonic acid group, pH of 5% by weight aqueous solution, amount added, and after addition of dialkyl ester of isophthalic acid having sulfonic acid group The procedure was performed in the same manner as in Example 1 except that the holding conditions (temperature, time) were variously changed as shown in Table 1. Examples 1 to 6
Table 1 also shows the characteristic values of the modified polyesters obtained in Comparative Examples 1 to 4.

[0037]

[Table 1]

As apparent from Table 1, in Examples 1 to 6, modified polyesters having a low content of DEG and having an intrinsic viscosity and color tone suitable for forming fibers were obtained.

On the other hand, in Comparative Example 1, the pH of the used 5% by weight aqueous solution of SIPM-Na was too low, and in Comparative Example 2, the holding temperature after the introduction of SIPM-Na was too high. The polyester had a high DEG content. In Comparative Example 3, since the retention time after the introduction of SIPM-Na was too short, the transesterification reaction of SIPM-Na became insufficient, and the polycondensation reaction time was extended by one hour because the polycondensation reaction rate was low. A modified polyester having an intrinsic viscosity sufficient to form a fiber could not be obtained, and the color tone was poor. Furthermore, in Comparative Example 4, the melt viscosity was increased due to the excessive amount of SIPM-Na added, and a modified polyester having an intrinsic viscosity sufficient for forming a fiber could not be obtained.

[0040]

According to the present invention, it is possible to produce a modified polyester which can be dyed with a basic dye having a small content of DEG, which causes a decrease in physical properties, at low cost and with high productivity.

Claims (1)

[Claims] When producing a modified polyester in which at least 80 mol% of the structural units are ethylene terephthalate units and 0.5 to 8 mol% are ethylene isophthalate units having a sulfonic acid salt group, ethylene terephthalate units are mainly used. A dialkyl ester of isophthalic acid having a sulfonate group having a pH of 4.0 or more in a 5% by weight aqueous solution is added to the polyester oligomer to be prepared.
A method for producing a modified polyester, comprising holding the mixture at the following temperature for 10 minutes or more, followed by polycondensation.