KR830000886B1 - Process for preparing for polyester - Google Patents

Abstract

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Description

Process for producing linear polyester

The present invention relates to a method for producing a linear polyester with improved UV stability of the linear polyester. Linear polyesters have very low stability under the influence of UV irradiation.

Linear polyesters are well known thermoplastic polymers that have chains composed of alternating residues of glycols and dicarboxylic acids, and the residues are ester bonds. Numerous acids and glycols have been proposed for the preparation of linear polyesters, the acids being (a) terephthalic acid, (b) isophthalic acid, (c) naphthalene-2,6-dicarboxylic acid, and (d) bis (carboxy phenoxy Ethane, etc., and glycols include alkane diols having 2 to 10 carbon atoms (such as ethylene glycol and 1,4-butane-diol), 1,4-dimethyl cyclohexane, and the like. The most common polyester is poly (ethylene terephthalate). Other commercially available linear polyesters are (a) a mixture of terephthalic acid and isophthalic acid (the mixture contains 80-95 mole percent terephthalic acid) and ethylene glycol, (b) 1,4- Polymers of butanediol and terephthalic acid, and (C) homopolymers of terephthalic acid and 1,4-dimeolcyclohexane, and the like.

Since the linear polyester according to the present invention contains a residue of bis (hydroxy-alkoxy) xantho-9-one in the molecule, the amount of bis (hydroxy-alkoxy) xant-9-one described above is the total polymer. 0.05-10% by weight is preferably 0.05-5% by weight.

For example, such linear polyesters have an intrinsic viscosity (IV) of at least 0.50 and contain the following molecular moieties.

(1) dicarboxylic acid selected from terephthalic acid, isophthalic acid, naphthalene-2,6-dicarboxylic acid, bis (carboxyphenoxy) ethane and the like

(2) glycols having 2-10 carbon atoms in the molecule, such as ethylene glycol, 1,4-butanediol and 1,4-di-methylolcyclohexane, and

(3) bis (hydroxy alkoxy) xanth-9-one.

The amount of (3) is 0.05-10% by weight, preferably 0.05-5% by weight based on the amount of (1) + (2) + (3).

An important class of linear polyesters according to the invention has the following repeating units.

-OYO-CO-X-CO-

Food,

The compound of formula (1) mentioned above is indicated below.

The polyesters according to the invention also contain 2,4-dihydroxy benzoic acid residues in the molecule at 0.05-10% by weight, preferably 0.05-5% by weight. Preferably, the molar ratio of xanthone to benzoic acid residues is 1: 1-1: 0.7.

The linear polyester is obtained by a two step process, the precursor is obtained in the first step. This precursor is a low molecular weight ester of glycol and dicarboxylic acid. In the second step, the precursor is expanded and condensed to increase the molecular weight to obtain polyester.

There are two general ways to make precursors. In the transesterification method, glycol is reacted with dialkyl ester of dicarboxylic acid. Low molecular weight alcohols are removed by transesterification to form glycol esters. Ethylene glycol, for example, is reacted with dimethyl terephthalate to produce ethylene glycol terephthalate and methyl alcohol (removed by distillation). The reaction rate can be increased by mixing the transesterification catalyst in the reaction mixture. Suitable transesterification catalysts include zinc acetate, manganese acetate, calcium acetate, cobalt acetate and titanium tetraisopropoxide.

In the direct esterification process, glycol and acid are esterified to produce a glycol ester with the removal of water, for example ethylene glycol is esterified with terephthalic acid. This direct esterification reaction can proceed without a catalyst, but under acidic conditions, when the direct esterification proceeds, ethylene glycol tends to dimerize as in the following reaction.

2HOCH ₂ CH ₂ OH = HOCH ₂ OCH ₂ CH ₂ OH + H ₂ O Some of the diethylene glycol produced by this reaction is bound to the polymer chain, but does not cause any adverse effects except for the reduction of softening point by a small amount. Do not. Alkaline compounds such as sodium hydroxide can be included in the direct esterification reaction mixture to reduce the formation of diethylene glycol to maintain a softening point at a satisfactory level.

The second step is carried out by heating the precursor at a temperature above the melting point at low pressure, for example 5 millibars or less, with stirring. Glycol is removed during polycondensation (by distillation). As the reaction proceeds, the molecular weight and viscosity increase. The increase in viscosity can be used to confirm when the desired molecular weight has been achieved.

Polycondensation catalysts are usually mixed during polycondensation. Suitable polycondensation catalysts include antimony trioxide, germanium dioxide, mixtures thereof, titanium alkoxides, lead oxide and zinc and the like. Some catalysts, such as germanium dioxide, are preferably dissolved in alkali prior to addition to the reaction system. In this case, in order to dissolve the catalyst, it is particularly suitable to use the alkali present in the direct esterification step (even if the catalyst does not affect the direct esterification).

The metal present in step 1 remains in the polymer and when colorless products are needed it is necessary to avoid residues present in the form of colored derivatives. Phosphoric acid or esters thereof can be added to the polycondensation mixture. This compound reduces the color caused by the metal. Phosphorous compounds suitable for addition to the polycondensation reaction include phosphoric acid, triphenyl phosphate and lean acid.

The present invention includes three polyester production methods. This method is described in detail as follows.

[Method 1]

According to method 1, the linear polyester, in particular polyethylene terephthalate, is present at a temperature of 0.04-10% by weight, preferably 0.04-5% by weight, based on the total reactants of the divalent phenol thermally stable at 250 ° C. It is prepared by polycondensation.

It is well known that esters of phenols with carboxylic acids are difficult, and in this way phenols cannot be easily incorporated into the chains of the polyester. The inventors have discovered that when bivalent phenol is included in the polycondensation mixture, an unexpected reaction occurs. Each hydroxyl group of the phenol reacts with a glycol (bonded or unbound) present in the system to form an ether bond to convert the phenol into a hydroxy alkoxy derivative. This derivative forms an ester bond with an acid moiety in the precursor. The overall reaction can be expressed as follows.

Where HOOCACOOH is a dicarboxylic acid, HOGOH is a glycol and HOXOH represents a phenol).

… … ACO-OGOH + HOXOH + HOGO-OCA...

=… ACO-OG-O-X-O-GO-OCA…

The present inventors do not prove the reactor mechanism, but the above-described overall effects can be explained. because.

(a) Phenol cannot be extracted or detected in polyester.

(b) When the polyester is hydrolyzed with acid and glycol, hydroxy alkoxy derivatives of phenol are present in the hydrolyzate.

(C) The results of the spectroscopic analysis and the proposed product were consistent with the proposed structure.

The following is an example of a dihydric phenol suitable for use in the reaction. Phenolics are classified by the parent ring system.

[Method 2]

According to Method 2, linear polyesters containing xant-9-one residues (ie, polyesters as described above) are based on the total reactants of 2,2 ', 4,4'-tetra hydroxy benzophenones. It is prepared by polycondensation in the presence of 0.04-10% by weight, preferably 0.04-% by weight. It is well known that 2,2 ', 4,4'-tetrahydroxy benzophenone is easily dehydrated to 3,6-dihydroxyxanth-9-one. Dehydration takes place under conditions of polycondensation and the product is reacted as in method 1.

[Method 3]

According to Method 3, linear polyesters containing xant-9-one residues (i.e. polyesters as described above) are either precursors or bis (hydroxy alkoxy) xanthate in the component from which the precursors are prepared. Prepared by mixing 9-one, preferably 3,6 isomer. Preferred alkoxy groups are ethoxy.

Method 2 is particularly suitable for polyesters based on glycols other than ethylene glycol, such as polybutylene, terephthalate.

According to the present invention, polyesters can be converted into moldings having good stability against UV irradiation.

The above-mentioned moldings include fibers and films, for example, moldings in which one layer of the product or both sides of the product are polymers, such as a plated film and a coewtr-uded laminate. Plated films can be used as reflectors in solar collectors. Transparent films can be used as transparent covers for windows, greenhouses, clothing, solar cells.

Moldings can be made from the polyesters according to the invention or from mixtures of the polymers and conventional polyesters.

The production method of the polymer according to the present invention will be described in detail based on the following examples.

In the examples, 2,2 ', 4,4'-tetrahydroxybenzophenone will be abbreviated as THBP.

Example 1

This example describes a process for the preparation of linear polyesters according to the invention using a two step process consisting of (1) direct esterification followed by (2) polycondensation. To begin step 1, the reactants described below were fed to the autoclave (for ease of handling, both GeO ₂ and NaOH were dissolved in small amounts, ie about 50 g of ethylene glycol).

60.5 kg terephthalic acid

30l ethylene glycol

3.5 g germanium dioside

3.5 g sodium hydroxide

The autoclave was pressurized to about 3 atm and heated with stirring. The reaction was initiated and the water by esterification was removed with excess glycol. The temperature was kept at reflux. The total amount of water by esterification was raised to 248 ° C. and removed after about 2.5 hours. The pressure was reduced by at least about 5 minutes and a small amount (about 5 l) of glycol was removed. When direct esterification by this conventional method was completed, 119 g of triphenylphosphate (in methanol) was added. 77 kg of the precursor for the preparation of conventional polyethylene terephthalate was obtained and used for polycondensation.

After the precursor was transferred to the polycondensation vessel, 2100 g of THBP, 2.7% by weight of the precursor, and 21 g of antimony trioxide were added to prepare a second step.

Removal of the glycol was started by distillation with stirring at 230 ° C. under atmospheric pressure. When distillation started, the pressure was slowly reduced to 0.3 millibar and the temperature was maintained at 290 ° C. After leaving the pressure to atmospheric pressure, the polymer was removed from the polycondensation vessel and chopped. The total weight of the polymer was 61 kg.

It is emphasized that the preparation method described in Example 1 is a conventional method besides the addition of THBP. The polymer is a high quality poly (ethylene terephthalate) for film molding with a high viscosity (IV) and a 254 ° softening point of 0.6. It contains 3% by weight of 3,6 (bis-2-hydroxyethoxy) xanth-9-one moiety wherein n '= n' '= 2 in formula (1).

Example 2

The polymer of Example 1 is used to make films by the present invention. The pieces of Example 1 were mixed with conventional poly (ethylene terephthalate) in a 1: 3 weight ratio. The mixture is thus made of a 125 μm thick film oriented biaxially containing 0.75% costhon moiety. The properties of this film are listed in Table 1 below.

Example 3

The pieces of Example 1 were mixed with the same poly (ethylene terephthalate) as used in Example 2 in a 1: 2 weight ratio. The mixture containing 1% of cosanthone residues is made of a 125 μm thick film oriented biaxially. The properties of this film are listed in Table 1 below.

TABLE 1

As demonstrated by the results listed in Table 1, both films are of good quality with satisfactory mechanical properties. The stability of the film to UV radiation is better than conventional poly (ethylene terephthalate).

The fragment of Example 1 and the films of Examples 2 and 3 are analyzed as follows.

(a) THBP cannot be detected in the polymer or film.

After hydrolyzing the film of the polymer with terephthalic acid and glycol ethylene glycol, THBP cannot be detected in the hydrolyzate.

(c) The hydrolyzate contains 3,6-bis (2-hydroxy-ethoxy) xant-9-one (which is a new compound) but this compound cannot be extracted from the polymer or the film.

(d) The hydrolyzate also includes residues of 2,4-dihydroxy benzoic acid.

Example 4

This example describes a process for the preparation of linear polyesters according to the invention using a two-step process consisting of (1) direct esterification followed by (2) polycondensation. To begin step 1, the next reaction was fed to an autoclave.

60.5 kg terephthalic acid 3.5 g germanium dioxide

30l ethylene glycol 3.5g sodium hydroxide

0.7kg 3,6-dihydroxyxant-8-silver

For the convenience of handling small amounts, both GeO ₂ and NaOH were dissolved in small amounts, ie about 50 g of ethylene glycol.

The autoclave was pressurized to about 3 atmospheres and heated with stirring. The reaction started and water by esterification was raised with some of the excess glycol. The temperature was kept at reflux. The total amount of water by esterification was removed about two and a half hours after the temperature was raised to 248 ° C. The pressure was reduced for about 5 minutes and a small amount of glycol was removed (about 5 l). 119 g of triphenylphosphate (in methanol) were added when direct esterification was complete.

77 kg of the product, which is a conventional precursor for the production of polyethylene terephthalate, was obtained and used for polycondensation. The precursor was transferred to a polycondensation vessel, and then prepared by adding 21 g of antimony trioxide for two steps. The glycol was removed by distillation while stirring at 230 ° C. under atmospheric pressure. When distillation started the pressure was slowly reduced to 0.3 millibars and the temperature was maintained at 290 ° C. The pressure was brought back to atmospheric pressure and the polymer was removed from the polycondensation vessel and cut into pieces. The total weight of the polymer was 61 kg.

It is emphasized that the preparation method described in Example 4 is also the same as the conventional method except adding 3,6-dihydroxy xant-8-one. The polymer is a high quality poly (ethylene terephthalate) used to make films having an intrinsic viscosity of 0.6 and a softening point of 254 °.

It comprises about 1% by weight of 3,6-bis (2-hydroxy ethoxy) xanth-9-one having the residue (n '= n' '= 2) in formula (1). The film is made from a polymer having the same film forming properties as the polymer of Example 1, but the UV stability is much better than that of Example 1 (Note: 3,6-dihydroxy xant-9-one is a precursor. It does not melt well in the material, so it is convenient to add it as soon as the first stage of the reaction is started).

Analyzing the polymer of Example 4 and the film prepared therefrom is as follows.

(a) 3,6-dihydroxy xant-9-one cannot be detected.

(b) 3,6-dihydroxycosanth-9-one cannot be detected in the hydrolyzate after the polymer and film are hydrolyzed with terephthalic acid and ethylene glycol.

(c) The hydrolyzate contains 3,6-bis (2-hydroxy-ethoxy) cosant-9-one, which is a novel compound, but this compound cannot be extracted from the polymer or film.

(d) 2,4-dihydroxy benzoic acid cannot be detected in the hydrolyzate.

Example 5

In order to illustrate the general use, the method of Example 1 was repeated for various kinds of phenols.

The precursors were prepared as described in step 1 of Example 1 and divided into 100 g each. The mixture obtained by adding one of the divalent phenols specified in Table 2 to each equal portion was polycondensed as described in step 2 of Example 1.

TABLE 2

Polycondensation was carried out with each phenol specified in Table 2. In one case 2 g and in another case 10 g of phenol were added to 100 g of precursor before polycondensation.

In all cases high quality polyesters were obtained, demonstrating that phenols were ethoxylated and copolymerized by NMR and IR spectra.

Examples 6 and 7 illustrate the use of 3,6-bis (hydroxy ethoxy) xanth-9-one to prepare polyesters. 3,6-bis (hydroxy ethoxy) xant-9-one was prepared from the following components.

28.2 g 3,6-dihydroxyxanthone 33.0 g 2-bromoethanol

17.2g sodium hydroxide 150ml distilled water

Sodium hydroxide was dissolved in distilled water and xanthone was dissolved in this alkaline solution. This dark red solution was filtered into a 500 ml spherical pulasco equipped with a stirrer, heater, reflux cooler, thermocouple pocket and dropping funnel. Bromoethanol was injected into the alkaline solution and the temperature of the mixture was slowly raised. Precipitation began to form at 64 ° C. and the temperature was maintained at 60 ° C.-64 ° C. for 4 hours.

The contents are removed from the flask and the precipitate is separated by filtration. When dried, 6.2 g of a creamy white solid were obtained. NMR spectrum revealed that this solid was 3,6-bis (2-hydroxy ethoxy) xant-9-one of about 99.5% purity.

The solution was again reacted with chloroethanol. Another 16.7 g of 3,6-bis (2-hydroxy ethoxy) xanth-9-one were obtained in about 95% purity.

When the 3,6-dihydroxy xanthone used in the examples is a known compound or a preparation method thereof, a large amount of 2, 2 ', 4, 4'-tetrahydroxy benzophenone is added to an air oven at 180 ° C. When left overnight, ring closure occurs with 3,6-dihydroxy xanthone.

Example 6

Step 1 including transesterification between 1,4-butane diol and dimethyl terephthalate salt and step 2 polycondensing the precursor of step 1 in the presence of 3,6-bis (hydroxy ethoxy) xanth-9-one Residual groups of 3,6bis (hydroxy ethoxy) xanth-9-one were added to the poly (butylene terephthalate) using two steps.

To carry out step 1, the following ingredients were fed into an esterification vessel.

640g dimethyl terephthalate

593 g 1,4-butanediol

0.1 g titanium tetraisopropoxide

(The third ester transfer catalyst was added as a 1% solution of butanol.

The reaction mixture was initially heated at 156 ° C. and continued to heat until 267 ml of methanol was collected when the temperature of the reaction mixture was raised to 218 ° C. The reaction mixture is left to cool to 170 ° C. and the reaction mixture is poured into a tray that will solidify at room temperature. Cool down to white solid, a precursor for stage 2.

The following reactants were used to perform step 2 (condensation polymerization).

100 g precursor (from step 1)

2.0 g 3,6-bis (hydroxy ethoxy) xanth-9-one

0.6g Titanium Tetra Isopropoxide

The polycondensation mixture was heated at 0.4 mmHg, 245 ° C. until a proper jump was obtained.

The product was a poly (tetramethylene terephthalate) containing residues of 3,6-bis (hydroxy ethoxy) -xantho-9-one. It had good UV stability.

Example 7

700 g of 3,6-bis (hydroxy ethoxy) instead of 2100 g of THBP. Xant-9-one was added to the polycondensation mixture and the method of Example 1 was repeated.

The resulting polyester contained about 1% by weight of 3,6-bis (2-hydroxy ethoxy) xanth-9-one moiety and was substantially the same as in Example 1. It was very similar to the product of Example 4 in that it had very good UV stability and no residue of 2,4-dihydroxy benzoic acid in the polymer.

Example 8

The method of Example 1 was repeated using 2,6-naphthalene-dicarboxylic acid instead of terephthalic acid.

Example 9

The precursor was obtained by transesterification of the following components.

Dimethyl ester of 70 kg bis (carboxyphenoxy) ethane

35l ethylene glycol

30 g manganese acetate (catalyst)

1400 g of THBP and 35 g of antimony oxide were added to the precursor and the mixture was polycondensed as described in Example 1.

The polyesters of Examples 8 and 9 had excellent properties including good UV stability. It has been shown that THBP is converted to 3,6-bis (hydroxy-ethoxy) xanth-9-one bound to the polyester chain.

Claims (1)

After adding a divalent phenol thermally stable at 250 ° C. to the precursor or a component from which the precursor is prepared, (1) terephthalic acid, (2) isophthalic acid, (3) naphthalene-2,6-dicarboxylic acid, (4 A method for producing a linear polyester by polycondensing a precursor which is an ester of one or more dicarboxylic acids and glycols selected from bis (carboxy phenoxy) ethane.