JP2002030137A - Process for producing modified polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give a process for producing with excellent productivity a modified polyester useful for forming fibers dyeable with a basic dye wherein the by- product diethylene glycol causing the deterioration of physical properties of a polyester is minimized. SOLUTION: A modified polyester is produced of which at least 80 mol% of the constituent units comprise ethylene terephthalate units and 0.5-8 mol% of the constituent units comprise ethylene isophthalate units having sulfonate groups. In the process for producing the polyester, a dialkyl ester of isophthalic acid having a sulfonate group, together with water in an amount of 1.0-6.0 mass% based on the dialkyl ester, is added to a polyester oligomer consisting mainly of ethylene terephthalate units to effect 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 dyeable sulfonate group in a basic dye.

[0002]

2. Description of the Related Art Polyester, especially polyethylene terephthalate (hereinafter abbreviated as PET), has excellent mechanical and chemical properties, and therefore is used not only for clothing and industrial fibers, but also for magnetic tapes and capacitors. Is widely used for molded products such as films or bottles.
However, dyeing properties are not good for textiles for clothing, and dyeing with disperse dyes is common.
It has disadvantages such as inferior clarity of dyed products.

Heretofore, in order to make up for such a drawback, isophthalic acid having a sulfonate group is copolymerized with a polyester to produce a dye which can be dyed with a basic dye (hereinafter abbreviated as a modified polyester). Method (Japanese Patent Publication No. 34-1)
No. 0497) is publicly known. However, today, a direct esterification method using terephthalic acid (hereinafter abbreviated as TPA) and ethylene glycol (hereinafter abbreviated as EG) as starting materials is generally performed as an industrially advantageous method. When the above method is applied to diethylene glycol (hereinafter referred to as DEGE) during the esterification reaction and the polycondensation reaction,
Abbreviated. ) By-produced in large quantities and copolymerized, resulting in 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 for remedying this drawback, it is known to add an alkali metal acetate or carbonate to the reaction system. However, when a large amount of an alkali metal salt is added, the alkali metal salt or carbonate is insoluble in the modified polyester. Ingredients are easily formed, and when spinning the resulting modified polyester, there have been problems in 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.
The degree of polymerization of bis- (β-hydroxyethyl) terephthalate and / or a low polymer thereof (hereinafter abbreviated as PET oligomer) obtained by a direct esterification method from is specified, and the transesterification reaction rate is 40 to 65%. A bis (β-hydroxyethyl) ester of isophthalic acid having a sulfonate group (hereinafter abbreviated as SIPG) has been proposed.

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
When the molecular weight of PG fluctuates and the copolymerization amount of the isophthalic acid component having a sulfonic acid group in the modified polyester is varied, and the obtained modified polyester is fiberized,
There is a problem that the uniformity of dyeing is impaired.

Further, 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 PET oligomers, the dialkyl ester of isophthalic acid having a sulfonate group precipitates during the polycondensation reaction, and the rate of the polycondensation reaction is reduced. There is a problem that the time becomes longer and the color tone of the obtained modified polyester deteriorates. In order to sufficiently dissolve the dialkyl ester of isophthalic acid having a sulfonic acid group into the PET oligomer, the transesterification reaction is performed by adding the dialkyl ester of isophthalic acid having a sulfonic acid group to the PET oligomer and then holding the melt for a certain period of time. It is effective to proceed, but at this time, there is a problem that DEG is by-produced at the same time, and if this is copolymerized in the modified polyester, it causes a decrease in physical properties as described above. No method has been found that sufficiently satisfies both of them.

[0008]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and provides a method for producing a modified polyester which has little by-product of DEG which causes deterioration of physical properties and is excellent in productivity. Is a technical issue.

[0009]

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. Is characterized in that a dialkyl ester of isophthalic acid having a sulfonic acid group is added together with 1.0 to 6.0% by mass of water to the dialkyl ester of isophthalic acid having a sulfonic acid group, and polycondensation is performed. The gist is a method for producing a modified polyester.

[0010]

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 polyethylene terephthalate units. When the content of the polyethylene terephthalate unit is less than 80 mol%, good physical properties of the polyester may be impaired.

Further, in order to make the polyester dyeable with the 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 yarn having sufficient strength cannot be obtained.

Further, as long as the effects of the present invention are not impaired, a polyester containing a small amount of a copolymer component other than the above may be used. Examples of such copolymerization components 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; and 1,4-cyclohexane. Glycol components such as dimethanol and 1,4-butanediol, 4-hydroxybenzoic acid, ε-
Examples include hydroxycarboxylic acid components such as caprolactone.

In the present invention, a PET oligomer produced by either a direct esterification method using TPA and EG as starting materials or a transesterification method using lower alkyl esters of TPA and EG as starting materials may be used. However, 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, the direct esterification PE
Since the T oligomer has a higher average degree of polymerization than the PET oligomer obtained by the transesterification method, the melting point of the PET oligomer may be higher.
Since T oligomers may solidify, P
It is preferable to depolymerize the ET oligomer and sufficiently lower the melting point.

Next, in the present invention, the solubility of the dialkyl ester of isophthalic acid having a sulfonate group in the PET oligomer is increased to increase the polycondensation reactivity and suppress the by-product of DEG. Dialkyl esters of isophthalic acid with base
When adding to the T oligomer, it is necessary to simultaneously add 1.0 to 6.0% by weight of water to the dialkyl ester of isophthalic acid having a sulfonate group. When the water content is less than 1.0% by mass, the solubility of the dialkyl ester of isophthalic acid having a sulfonate group in the PET oligomer becomes low, and the dialkyl ester of isophthalic acid having a sulfonate group precipitates during the polycondensation, and the polycondensation reaction proceeds. The speed becomes slow and the reaction time becomes long, and the color tone of the resulting modified polyester deteriorates. On the other hand, when the moisture is 6.0
When the content is more than 10% by mass, hydrolysis of a dialkyl ester of isophthalic acid having a sulfonate group or a PET oligomer tends to proceed, and a polycondensation reaction rate is reduced due to the influence of a carboxyl terminal group generated by the hydrolysis,
Increase the amount of by-products.

The water is contained in the dialkyl ester of isophthalic acid having a sulfonic acid group in advance by absorbing the dialkyl ester of isophthalic acid having a sulfonic acid group, or when the water is added to the PET oligomer. Water may be mixed and contained. More specifically, the dialkyl ester of isophthalic acid having a sulfonate group is suitably used as an EG slurry of 30 to 40% by mass, and the dialkyl ester of isophthalic acid having a sulfonate group is contained in such a slurry. It is preferable to add and mix 1.0 to 6.0% by mass of water in advance and then add the slurry to the PET oligomer. In addition, such a slurry is preferably kept at a temperature of 50 to 80 ° C. in order to maintain fluidity for a long time.

Specific examples of the dialkyl ester of isophthalic acid having a sulfonic acid group as described above include dimethyl 5-sodium sulfoisophthalate (hereinafter referred to as SIPM-Na).
Abbreviated. ), Dimethyl 5-potassium sulfoisophthalate (hereinafter abbreviated as SIPM-K), dimethyl 5-lithium sulfoisophthalate (hereinafter abbreviated as SIPM-Li) and the like.

The method for producing the modified polyester of the present invention can be carried out, for example, as follows. First, a slurry having a molar ratio of EG / TPA of 1.1 to 2.0 is added to an esterification reaction tank containing PET oligomer at a temperature of 230 to 250 ° C. under nitrogen gas control, and the PET oligomer is continuously maintained for a residence time of 7 to 8 hours. I get it. Next, this PE
The T oligomer is transferred to a polymerization reactor, and if necessary,
Depolymerization is performed by adding 15% by mass of EG, and 30 to 40% by mass of an EG slurry of a dialkyl ester of isophthalic acid having a sulfonate group is 1.0 to 6.0% by mass based on a dialkyl ester of isophthalic acid having a sulfonate group. % Water is added and a predetermined amount is added. After the addition of the dialkyl ester of isophthalic acid having a sulfonate group, if the melting and holding are performed for an excessively long time, the by-product amount of DEG may increase. Is heated to 270 to 280 ° C. and finally subjected to a polycondensation reaction under a 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.
The range is generally from 10 ^-3 mol, optimally from 1 x 10 ^{-4 to} 3 x 10 ^-3 mol. In the present invention, additives such as stabilizers such as hindered phenol compounds and phosphorus compounds, cobalt compounds, fluorescent agents, color tone improvers such as dyes, and pigments such as titanium dioxide may be contained.

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 sulfonate group, it is possible to further suppress the by-product of DEG. This is preferred because a modified polyester of high quality can be obtained.

As the alkali metal compound used at this time, a hydroxide, an organic carboxylate, an alcoholate, an 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 these additives is preferably 5 × 10 ⁻³ mol or less per 1 mol of the acid component constituting the polyester in order not to generate insoluble components in the polyester.

[0022]

According to the present invention, the present inventors believe that a modified polyester which can be dyed to a basic dye with little decrease in physical properties due to by-product DEG can be obtained with good productivity as follows. . Generally, a dialkyl ester of isophthalic acid having a sulfonate group has a low solubility in a PET oligomer, and therefore, if a polycondensation reaction is performed simply by adding it to a PET oligomer, a dialkyl ester of isophthalic acid having a sulfonate group is precipitated. The rate of the polycondensation reaction decreases. Then, in order to sufficiently dissolve the dialkyl ester of isophthalic acid having a sulfonic acid group in the PET oligomer, after adding the dialkyl ester of isophthalic acid having a sulfonic acid group to the PET oligomer,
The transesterification reaction may be advanced by holding the resin for a certain period of time, but at this time, DEG is simultaneously produced as a by-product, and if this is copolymerized in the modified polyester, it causes a decrease in physical properties.

In the present invention, when a dialkyl ester of isophthalic acid having a sulfonate group is added to a PET oligomer, a specific amount of water is added at the same time,
It becomes possible to enhance the solubility of the dialkyl ester of isophthalic acid having a sulfonic acid group in the PET oligomer. For this reason, the polycondensation reactivity is not impaired without performing the melting and holding for promoting the transesterification reaction as described above, and the by-product of DEG is suppressed, and the deterioration of the physical properties of the modified polyester is prevented. It becomes possible.

In general, when water is mixed into the reaction system during the polycondensation, a dialkyl ester of isophthalic acid or PE
Although there is a concern about the occurrence of hydrolysis of the T oligomer and its adverse effects, if the amount of water added is within the range of the present invention, a reduction in the rate of the polycondensation reaction due to the influence of the carboxyl terminal group generated by the hydrolysis and a decrease in the amount of DEG Adverse effects such as an increase in production can be substantially eliminated.

[0025]

Next, the present invention will be described in detail with reference to examples. In addition, the measuring method of the characteristic value in an Example was performed as follows. (a) Moisture content in dialkyl ester of isophthalic acid having sulfonic acid salt group It was determined according to the Karl Fischer method described in JIS-K0068. (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 polyester was alkali-hydrolyzed, the content was determined using a gas chromatograph GC-9A manufactured by Shimadzu Corporation. When this value is 3.0 mol% or less, the effect on the physical properties of the polyester is at a level where 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 TPA was added to an esterification reactor in which a PET oligomer was present.
And a slurry having a molar ratio of 1 / 1.6 with EG is continuously supplied,
The esterification reaction was carried out under the conditions of a temperature of 250 ° C., a pressure of 0.1 MPaG, and a residence time of 8 hours 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 titanium dioxide was added in an amount of 0.4% by mass, antimony trioxide was added in an amount of 2.5 × 10 ^-4 mol per mol of acid component, and triethyl phosphate was added in an amount of 1.2 × 10 ^-4 mol. × 10 ^-4 mol was added.
Then, 35 mass% EG of SIPM-Na with a moisture content of 0.3 mass%
1% by weight of water based on SIPM-Na was added to the slurry, and the slurry was added in such an amount that SIPM-Na was 5.0 mol% based on the acid component.

Next, the temperature inside the polycondensation reaction vessel is 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 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. Next, titanium dioxide was added to the depolymerized PET oligomer in an amount of 0.4 mass%, antimony trioxide was added in an amount of 2.5 × 10 ^-4 mol, and triethyl phosphate 1.2 × 10 ^-4 mol per 1 mol of the acid component. added. And
A 35% by mass EG slurry of SIPM-Na with a moisture content of 4.5% by mass was absorbed in a thermostatic chamber at a temperature of 25 ° C. and a humidity of 90% RH. A certain amount was added.

Next, the temperature inside the polycondensation reaction vessel is 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 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 to 1 mol of the acid component before adding SIPM-Na.
The same was done.

Examples 4 to 6 and Comparative Examples 1 to 3 The types and amounts of the dialkyl esters of isophthalic acid having a sulfonic acid group and the amounts of water added to the EG slurry of the dialkyl esters of isophthalic acid having a sulfonic acid group are shown in Table 1. Example 1 was carried out in the same manner as in Example 1 except for various changes as shown in FIG.

COMPARATIVE EXAMPLE 4 Except that water was not added to the EG slurry of SIPM-Na, and this slurry was added to the PET oligomer, kept at 250 ° C. with stirring for 15 minutes, and then subjected to a polycondensation reaction. Was performed in the same manner as in Example 1.

[0034]

[Table 1]

As is evident from Table 1, in Examples 1 to 6, modified polyesters having a low DEG content and having intrinsic viscosity and color tone suitable for fiberization were obtained.

On the other hand, in Comparative Example 1, the water content of the SIPM-Na in the EG slurry was too low, so that the solubility of the SIPM-Na in the PET oligomer was poor, the polycondensation reaction speed was slowed, and the polycondensation reaction time was shortened. When extended for one hour, the color tone of the resulting modified polyester became poor. Comparative Example 2
Since the water content in the EG slurry of SIPM-Na is too high, the DE of the modified polyester obtained by the influence of the hydrolysis is too high.
G content increased. In Comparative Example 3, the added amount of SIPM-Na was too large, so that the melt viscosity was increased, and a modified polyester having an intrinsic viscosity sufficient to form a fiber could not be obtained.
In Comparative Example 4, the amount of water in the EG slurry of SIPM-Na was the same as in Comparative Example 1. However, since the melt retention time was provided after the addition of SIPM-Na and the transesterification reaction was advanced, the polymerization reaction speed was problematic. There was no one. However, DEG was by-produced during the melting and holding, and the resulting modified polyester had a high DEG content.

[0037]

According to the present invention, a modified polyester having a low content of DEG, which causes deterioration in physical properties, can be produced at low cost.
It is possible to manufacture with high productivity.

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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 with 1.0 to 6.0% by weight of water relative to the dialkyl ester of isophthalic acid having a sulfonate group to the polyester oligomer to be subjected to polycondensation. For producing high quality polyester.