JPS5922728B2 - Manufacturing method for polyester with good transparency - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyethylene terephthalate having good color tone and transparency, or a polyester mainly composed of polyethylene terephthalate.

Polyethylene terephthalate is widely used as fibers, swimming pools, etc., and is used industrially as polyethylene terephthalate.

It is produced by a method in which bis(β-adroxyethyl) terephthalate (including its low polymers) is obtained by an I-exchange reaction, and this is polycondensed at high temperature and under high vacuum to form a high polymer. At this time, as a catalyst for the polycondensation reaction,
Antimony compounds, especially antimony trioxide, are the most widely used.
1. However, it has the disadvantage that it has a dark gray tone.

This phenomenon becomes a fatal defect when polyester is used as a transparent film, and when used as a fiber, it causes deterioration in the quality of the product, such as decreased whiteness and lack of sharpness during dyeing. In particular, when the amount of the antimony compound catalyst is increased, this darkening phenomenon is significant, and even though increasing the amount of catalyst increases the reaction rate and increases productivity, the amount of catalyst must be kept low. By the way, the cause of this dark gray tone is the precipitation of metallic antimony due to the reduction of the antimony compound, or the reaction of the antimony compound with chemical species in the reaction system such as raw materials, other catalysts, and thermal stabilizers. It is thought that insoluble fine particles may be generated.

These insoluble fine particles not only deteriorate the color tone and transparency of the polymer, but also cause problems such as adhering to the can wall during polymerization, gradually accumulating, peeling off, and mixing into the polymer, impairing quality.

Particularly when continuous operation is performed for a long period of time, this adhesion and peeling from the can wall becomes an important problem. In addition, during spinning, this detached material accumulates on the sand layer used as a filter in the spinning head, increasing the spinning head pressure, causing various troubles during spinning, and deteriorating quality. Since the spinning head must be replaced every now and then, the product price will increase. Conventionally, as a method to improve this dull color tone while using an antimony compound as a catalyst, there has been a method in which it is combined with other metal compounds (for example, used in conjunction with a certain type of organic tin compound; Japanese Patent Publication No. 47-44037, etc.)
, or in combination with an organic substance (for example, adding an aliphatic α-oxycarboxylic acid or a derivative thereof;
Special Publication No. 48-42232).

However, when combined with other metal compounds, problems arise such as a decrease in the thermal stability of the polymer and an increase in the DEG content.

The method of adding an organic substance can be said to be an excellent method since it will hardly have any adverse effect on the physical properties of the resulting polymer if the added amount is a small amount, such as a catalytic amount or less, and the compound has a significant effect.

The present inventors extensively studied various organic additives as a method to eliminate the dark color tone of polyethylene terephthalate that occurs when antimony compounds are used as polycondensation catalysts. It has been found that the addition of this compound is extremely effective.

That is, in the present invention, when producing polyester by polycondensing bis(β-hydroxyethyl) terephthalate or a composition mainly composed of bis(β-hydroxyethyl) terephthalate using an antimony compound as a catalyst, the compound represented by the following formula is added in the following amount. This is a method for producing polyester with good transparency, which is characterized by the addition of polyester.

R: H or an alkyl group having 1 to 5 carbon atoms
N or halogen compound: 0.02 to 2 mol X is NO
ρ compound: 0.02 to 0.25 mol The antimony compound in the present invention is a conventionally known compound such as antimony Ξ oxide, antimony trichloride, antimony acetate, or antimony glycolate, and the addition time is before the start of the polycondensation reaction. Any time is fine.

Further, the substituted benzoic acid compound can be added at any time from before the start of the polycondensation reaction to during the polycondensation reaction.

Although it may be added directly into the reaction system as a solid, it is convenient to add it to the reaction system in a state dissolved in ethylene glycol together with the antimony compound of the catalyst before the polycondensation reaction. The amount of the substituted benzoic acid compound added is 0.0 in the case of a cyano or halogen substituted compound, based on the number of moles of antimony atoms in the antimony compound added.
2 to 2 mol, 0.02 to 0.2 in the case of nitro-substituted product
It is 5 moles. If the amount is less than this range, it will not be possible to prevent the dark tone caused by antimony compounds.
Moreover, if the amount exceeds this range, the effect of improving transparency remains the same, but yellow coloring of the polymer starts to become noticeable in compounds such as nitro- and cyano-substituted benzoic acids, which have particularly remarkable effects, which is not suitable. The method of the present invention can be applied not only to batch polymerization but also to continuous polymerization, and during polycondensation, catalysts used in the synthesis of bis(βL hydroxyethyl) terephthalate, stabilizers such as phosphorus compounds, titanium dioxide, etc. There is no problem even if additives such as pigments such as In addition, a method of adding nitrobenzoic acid for the purpose of improving the dyeability of polyester is proposed in Japanese Patent Publication No. 37-111445. It is necessary to add a much larger amount than in the invention, and the yellow coloring of the polymer is significant, so that the purpose of the invention cannot be achieved with this method.

Next, the method of the present invention will be described with reference to Examples, but the present invention is not limited thereto.

In the examples, the ultimate degree [η] of the polymer is a value measured at a temperature of 20° C. using a phenol (50):tetrachloroethane (50) mixture as a solvent. Observe the color tone and transparency of the obtained polyethylene terephthalate in the molten state, then mold it into granules and crystallize at 150°C ± 2°C for 1 hour, then measure the L value, a value, and b value using a color difference meter. I asked for it. The L value is lightness (the larger the value, the brighter it is). The a value is a red-green hue (+ means reddish-greenish), and the b value is a yellow-blue hue (+
represents a yellowish tinge, - represents a bluish tinge). Regarding the color tone of the polymer, the larger the L value, the closer the a value to o, and the smaller the b value, the better. Further, the transparency of the polymer was evaluated as follows.

Phthalic anhydride/maleic anhydride (mole ratio 1/1) and ethylene glycol/propylene glycol (mole ratio 1/1)
) and 51% by weight of styrene monomer.
Titanium dioxide fine powder is added to a mixture of 0, 3, 5,
10 ppm of benzoyl peroxide is dispersed, 1% by weight of benzoyl peroxide is added to the mixture, and the mixture is reacted and solidified at 40 to 60'C for about 4 hours to obtain a standard polymer composition.

(A standard polymer composition with a titanium dioxide content of 0 ppm has very good transparency.) The transparency of this standard polymer composition and the molten polymer of the sample were visually compared, and the standard polymer composition with the closest transparency was compared. Samples with titanium dioxide content.

Transparency was evaluated using the following ranking. -, Transparency (Titanium dioxide content Ppm) Transparency rank o Good 3 Slightly poor Transparency (Titanium dioxide content Ppm) Transparency rank 5 Poor 10 Very poor Example 1 Dimethyl terephthalate 1 mol, ethylene glycol 2
4 x IOH moles of calcium acetate were added into a glass flask equipped with a fractionating tube, and the mixture was heated from 180°C to 230°C under normal pressure.
The temperature was gradually raised to °C until the distillation of methanol was completed.

Subsequently, the temperature was raised to distill excess ethylene glycol out of the system. The above transesterified product was transferred to an autoclave, and a solution of 4 x 10-4 mol of trimethyl phosphate and 2 x 10-4 mol of antimony trioxide in ethylene glycol plus the substituted benzoic acid compound shown in the table below was gradually added. The pressure is finally reduced to 0. IW! LHg, 27
Polycondensation was carried out at 5°C for 2 hours. The properties of the obtained polymer are shown in the table below. In the table Haruka 1, 2, 5, 6, 11, 12,
17 is a comparative example.

Examples (A3-4, 7-10,
13-16, 18-23), the polymer has good transparency and color tone, but Comparative Examples (A1, 2, 6, 12) C, in which the amount of substituted benzoic acid compound added is o or small, have poor transparency or Comparative examples (Haruka 5, 11, 17) in which the amount of addition was too large showed good transparency, but
The polymer has a yellowish tinge and the b value increases.

Example 2 The amount of antimony trioxide was 5 x 10-4 mol, the polycondensation time was 1.5 hours, and the amount of m-nitrobenzoic acid was 0.1 x 10
A polyester was produced in the same manner as in Example 1 by adding -4 mol.

The obtained polyester had good transparency and [η] 0.7
6. Softening point 2630℃, L value 71.0a value -1.2, b
The value was -1.9. On the other hand, when m-nitrobenzoic acid was not added, the resulting polyester had extremely poor transparency, [η] 0.75, and a softening point of 263.1.
℃, L value 63.3, a value -1.0) b value -1.5. Example 3 A slurry of terephthalic acid and ethylene glycol (ethylene glycol/terephthalic acid molar ratio 1.8) was continuously fed in the presence of bis(β-hydroxyethyl) terephthalate and its oligomers at 260°C.
The esterification reaction was carried out under normal pressure for a residence time of 6 hours to continuously obtain an esterified product with a reaction rate of 96 CfA.

For each mole of the acid component of this esterification product, 2 x 10-4 mol of antimony trioxide dissolved in ethylene glycol, 4 x 10-4 mol of trimethyl phosphate and 1.0 x 10 mol of p-cyanobenzoic acid. -4 mol was added and the pressure was gradually reduced to 0.5 mmHg and 2800C.
A time polycondensation reaction was carried out. The obtained polymer had good transparency when melted, had no dark color tone, and had a [η] of 0.
70, softening point 262.00C,. With an I value of 72.5, an a value of -1.1, and a b value of -2.3, no dark tone was observed even after chip molding, and the color tone was extremely good.

On the other hand, the polymer obtained without adding p-cyanobenzoic acid had a slightly dark color tone and poor transparency when melted, and even after chip molding, the polymer had a dark color tone [η] 0.7L
The softening point was 261.8°C, the L value was 67.5, the a value was -0.9, and the b value was -2.7.

Example 4 A transesterification reaction was carried out under the same conditions as in Example 1 using 0.88 mol of dimethyl terephthalate and 0.12 mol of methyl p-oxyethoxybenzoate as acid components, and then the product was transferred to an autoclave. Trimethyl phosphate 4 x 10-4 mol, cobalt acetate 1 x 10-
4 mol, Ξ antimony oxide 2 x 10-4 mol and m-
Polycondensation was carried out under the same conditions as in Example 1 by adding 0.5×10 −4 mol of nitrobenzoic acid.

The obtained polymer had no dark tone at all, had good transparency, [η] 0.63, softening point 234.1°C, and L value 72.
．． 0,. The a value was -0.2 and the b value was -5.1, and there was no dark tone at all even after chip molding, and the color tone was good.
On the other hand, the polymer obtained without adding m-nitrobenzoic acid had a dark color tone and poor transparency when melted, and had [η
] 0.63, softening point 233.7℃, L value 67.5a value -
1.0, b value -2.5, and even after chip molding, the L value was low and the color tone was dark.

Reference Example The polymer obtained in Example 3 was discharged at a discharge rate of 2009/YYIin.
Continuous spinning was carried out for 10 days.

The polymer obtained by adding p-cyanobenzoic acid had a small increase in spinning head pressure and was in a state where spinning could be continued, but the polymer obtained without adding p-cyanobenzoic acid showed a small increase in spinning head pressure, but the polymer obtained without adding p-cyanobenzoic acid had a problem due to filtration layer blockage. Due to the increase in spinning head pressure, spinning could no longer be continued.

The spinning head was removed, the sand layer with the polymer attached was sampled, then incinerated, dissolved in acid, and antimony metal was quantified by atomic absorption spectrometry. Antimony metal was converted to Sb2O3 per mole of acid component in the incinerated polymer. The amount was 5 x 10-4 mol when p-cyanobenzoic acid was added, and 37 x 10-4 mol when it was not added.

Claims (1)

[Claims] 1. When producing polyester by polycondensing bis(β-hydroxyethyl) terephthalate or a composition mainly composed of bis(β-hydroxyethyl) terephthalate using an antimony compound as a catalyst, a compound represented by the following formula is added in the following amount. A method for producing polyester characterized by adding. Formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (R: H or alkyl group with 1 to 5 carbon atoms is C
N or halogen compound: 0.02 to 2 mol X is NO
Compound _2: 0.02 to 0.25 mol