NL8403066A - PROCESS FOR PREPARING AROMATIC POLYESTERS. - Google Patents

Description

* "NL 32150-Pf / ed - 1 - <-," Process for the preparation of aromatic polyesters.

The present invention relates to an improved process for the preparation of copolyesters. More particularly, the invention relates to a process for the preparation of oxybenzoyl polyesters of aromatic dicarboxylic acids, dihydroxyphenols and p-hydroxybenzoic acid compounds as the starting materials.

It is known that such polyester resins can be prepared by a variety of polymerization processes, including suspension polymerization and mass polymerization. Of these, the mass polymerization process is perhaps the most desirable process in terms of cost. However, since the aromatic polyester has a high melting point compared to aliphatic polyesters, such as polyethylene terephthalate, a higher temperature is required to keep the aromatic polyesters in their molten state. As a result, the polymers are often colored and exhibit poorer behavior.

Furthermore, difficulties were encountered in obtaining consistent molding properties of the resin from batch to batch. Of course, variations in molding conditions are undesirable in commercial work and can lead to machining inefficiencies and unacceptable differences in the molded articles.

Therefore, a considerable effort has been made to develop a method which avoids the above-discussed drawbacks and provides a polyester material from which articles with a pleasant and uniform appearance and favorable uniform properties can be formed.

According to the invention, a polymer can be prepared in a consistent manner, which has an extremely low degree of 30 has discoloration and has excellent heat stability, if it has not been available up to now with the usual mass polymerization.

It is an object of the present invention to provide a process for the preparation of aromatic polyesters with an extremely low degree of decolorization and excellent heat stability.

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Another object of the invention is to provide an improved process for the consistent, economical preparation of aromatic polyesters of acceptable quality.

It is further an object of the invention to provide polyesters with reproducible melting and crystallization temperatures.

Other objects and the further scope of applicability of the present invention will become apparent from the following detailed description.

It has been found that a process which overcomes the problems encountered in practice of the known processes and yields polyester resins, the use of which does not involve the drawbacks mentioned, is characterized in that a salt is included in the reaction procedure prior to the completion of the polymerization. More in particular, an alkaline earth metal salt or an alkali metal salt, preferably potassium sulfate, is added during the preparation of the resin, in particular to the prepolymer melt prior to the further reaction of the final product to the desired degree of polymerization.

The wholly aromatic polyesters to which the present invention is directed consist of combinations of repeated units with one or more of formulas 1-6 of the formula sheet, wherein x represents O, S, O

II

25 - c -, NH or S02 and n stands for 0 or 1 and the sum of the integers p + q + r + s + t '+ uin the units present is between 3 and 800.

Combinations of the above units include the coupling of the carbonyl group of formulas 1, 2, 4 and 5 with the oxy group of formulas 1, 3, 4 and 6. In the most general combination, all units of the above formulas may be present in a single copolymer. The simplest forms would be units 1 or 4 homopolymers. Other combinations include mixtures of units 2 and 3, 2 and 35 6, 3 and 5, 5 and 6 and 1 and 4.

The placement of the functional groups is preferably in the para (1,4) position. They can also be in meta- (1,3) position relative to each other. Regarding 8403066-3 - the naphthalene moiety, the most desirable positions of the functional groups are: 1,4, 1,5 and 2,6. These groups may also be in the meta position relative to each other.

The symbols p, q, r, s, t and u are integers 5 and indicate the number of units present in the polymer.

The sum (p + q + r + s + t + u) can range from 3 to 800 and, if present, can be the ratio of q / r, q / u, t / r, t / u, q + t , q + t, and t. vary from about 10/11 to about 11/10 with r r + u r + u 10 as the most desired ratio of 10/10.

Examples of materials from which the units of formula I can be obtained are p-hydroxybenzoic acid, phenyl-p-hydroxybenzoate, p-acetoxybenzoic acid and isobutyl-p-acetoxybenzoate. The formula 2 unit is available, inter alia, from terephthalic acid, isophthalic acid, diphenyl terephthalate, diethyl isophthalate, methyl ethyl terephthalate and the isobutyl hemiester of terephthalic acid. Among the compounds from which the unit of formula III originates, mention may be made of p, pf-bisphenol, p, proxybisphenol, 4,4'-dihydroxyben2ophenone, resorcinol and hydroquinone. It can be determined which of these materials are also suitable for supplying the units of formulas 7, 8 and 11.

Examples of monomers associated with formula 4 are 6-hydroxy-1-naphthoic acid, 5-acetoxy-1-naphthoic acid and phenyl-5-hydroxy-1-naphthoate. Monomers of formula 5 include 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid. The diphenyl esters or dicarbonyl chlorides of these acids can also be used. Examples of monomers associated with formula 6. are 1,4-di-hydroxynaphthalene, 2,6-diacetoxynaphthalene and 1,5-dihydroxynaphthalene.

Particularly preferred for use in the practice of the present invention are plastics materials based on oxybenzoyl polyesters.

The oxybenzoyl polyesters useful in the present invention generally comprise repeating units of formula ii of the formula sheet wherein p is an integer from 3 to 600.

8403066 - 4 - [', 5 * * ί

A preferred group of oxybenzoyl polyesters are those of formula 7 of the formula sheet wherein R is selected from the group of benzoyl, lower alkanoyl or preferably hydrogen, R2 is hydrogen, benzyl, lower alkyl or preferably phenyl and 5 p is an integer of 3 to 600, preferably from 30 to 200. These values for p correspond to a molecular weight of from about 1000 to 72000 and preferably from 3500 to 25000. The synthesis of these polyesters is described in detail in U.S. Patent Application Serial No. 619,577 filed March 1, 1967 and entitled " Polyesters based on hydro-xybenzoic acids ". This patent application is referred to in U.S. Pat. No. 3,668,300.

Another preferred group of oxybenzoyl polyesters is formed of repeat unit copolyesters of formulas 8 and 9 of the formula sheet, wherein X represents -O or -S0a-, m represents 0 or 1, n represents 0 or 1, q: r 10 s 15 to 15; 10, p; q = 1: 100 to 100: 1r p + q + r = 3 to 600 and preferably 20 to 200. The carbonyl groups of the units of formula 1.or 4 are linked to the oxy groups of a 20 unit with formula 1 or 4, the oxy groups of the unit of formula 1 or 4 are linked to the carbonyl groups of the unit of formula 1 or 3.

Preferred copolyesters have repeated units of formula 10 of the formula sheet.

The synthesis of these polyesters is described in detail in US Patent 3,637,595 entitled "p-Oxybenzoyl copolyesters".

The mass condensation of aromatic polyesters is described in the patent literature and broadly involves an alkanoylation step, whereby an appropriate dicarboxylic acid, hydroxybenzoic acid and diol are reacted with an acid anhydride, a prepolymerization step, wherein the first stage reaction product is polycondensed is prepolymer and then the prepolymer is heated to form a polycondensate of the desired degree of polymerization.

The polyesters useful in the present invention may also be chemically modified in various ways, such as by incorporation in the polyester of monofunctional reagents such as benzoic acid or tri and multifunctional reagents such as 1,3,5-benzene tricarboxylic acid or cyanuric chloride. The benzene rings in these polyesters are preferably unsubstituted, but may be substituted with non-interfering substituents, eg halogen such as chlorine or bromine, low alkylox such as methoxy and low alkyl such as methyl.

The salt can be an organic or an inorganic salt. However, the use of an alkaline earth metal is preferred. More specifically, can the following salts be used? aluminum acetate, calcium acetate, calcium sulfate, copper acetate, magnesium acetate, magnesium terephthalate, potassium acetate, potassium chloride, potassium phosphate, sodium acetate, sodium sulfate and potassium bisulfate.

Although the addition of the salt is conceivable at any stage of the procedure, it has been found to be particularly effective and give remarkably better properties in the articles formed from the oxy-benzo polyester resin when the salt is added to the monomer charge.

The salt can be added as a solid or as a solution at a temperature above the melting point of the salt. It is also possible to add the salt in a solution when this is done at a lower temperature.

In a broad sense, the salt is added in amounts in a range from about 25.0 ppm to about 500 ppm. The exact mechanisms by which the processability of the polyester and the appearance and properties of the articles formed from the polyester are markedly improved by the addition of the indicated salts are not yet fully understood. However, it has been observed that the maintenance of peak heights in repeated endothermic transitions and the achievement of self-equalizing exothermic transitions are significantly and substantially improved when the said salts are used in the formation of the polyesters. | The aromatic oxybenzoyl polyester polymers are known to exhibit an endothermic transition similar to the melting of the polyester. Exothermic transition or crystallization occurs during cooling. When a strong 8403066 * - 6 - 7 th exotherm is observed, the transitions are described as reversible. Observations and results included in the following tables show that the addition of a salt, such as potassium sulfate, has greatly increased the reversibility of the 5 peaks observed with the differential scanning Calorimeter 'or DSC »

To determine peak height maintenance, the endotherms for the first and second heating cycles are measured on the same scale. The distances from the baseline to the 10 maxima are determined and the height of the peak of the first cycle is divided by the height of the peak of the second cycle (x 100). The value thus obtained is indicated by "percentage retention" !.

When the endotherms are measured for aromatic oxybenzoyl polyesters that do not contain salt, it appears that in the peaks of the second cycle the onset of transition is difficult to determine and the width of the heating curve makes it difficult to determine the peak. In that case, the temperature change between the beginning of the transition and the moment of 20 is the maximum temperature of a gradual nature, thereby obtaining a heating curve resembling a moderately steep or rounded hill. Such a peak is referred to in the present specification, and in particular in its examples, as a broad or diffuse peak.

The peaks of the second cycle, in those cases where a salt was included in the preparation of the aromatic polyesters in accordance with the present invention, are sharp and clear with well-determinable temperature curves, with temperatures from the beginning of the 30 transition and of the peak maximum are easily determined.

The invention is further illustrated by the following examples, which should not serve to limit the scope of protection.

35 Example 1

A reaction vessel was charged with 122 kg of 4,4'-dihydroxy-biphenyl, 180 kg of p-hydroxybenzoic acid, 108 kg of terephthalic acid and 313 kg of acetic anhydride. The mixture was covered with nitrogen 3403066 / fabric and refluxed with stirring for a minimum of 3 h. Distillation without recirculation was then carried out for about 5.5 hours, the temperature of the reaction mixture being raised to 315 ° C. At this point, 0/32 5 kg of distearyl pentaerythritol diphosphite was added and after 10 min the thick melt (93.3% conversion based on the yield of distillate) was poured into an insulated stainless steel dish and left under cooling with nitrogen, The mass was then removed and ground (size <10 1.2 mm, 80% <0.5 mm). The yield of prepolymer after milling was 90%.

The prepolymer was further processed by circulating it under nitrogen in a rotary oven. The prepolymer was heated from ambient temperature to 365 ° C at a rate of 23 ° C / h and immediately cooled. The resulting polymer was obtained in the form of a free-flowing powder.

Example II

The procedure of Example 1 was repeated exactly using the same materials and procedures with the only exception that 57 g of potassium sulfate was charged to the reaction vessel with the monomer batch.

The endothermic and exothermic peaks measured with DSC (Differential Scanning Calorimeter) for the first and second heating cycles were determined and are listed in Table A below.

TABLE A

Endothermic peak (DSC) Start of exothermic 30 heating cycle (DSC) cooling cycle le_2e_ le 2e

Example I 410 weak ^ 366 355

EXAMPLE 2 421 419 381 381 The peak observed in this case is of a broad and diffuse character and cannot be considered a sharp, pronounced peak.

Example III

A reaction vessel was charged with 204.0 g (1.095 mol) 4.41-dihydroxybiphenyl, 301.1 g (2.18 mol) p-hydroxybenzoic acid, 8403066-181.1 g (1.09 mol) terephthalic acid, and 526 6 g (5.158 mol) acetic anhydride, the mixture was covered with nitrogen and refluxed with stirring for at least 3 h. Distillation without recycle was then carried out for about 5.5 h, while the temperature of the reaction mixture was raised to 315 ° C. At this point, 0.76 g of distearyl pentaerythritol diphosphite was added and after 10 min the thick melt (93.3% conversion based on the yield of distillate) was poured into a stainless steel aluminum foil-lined beaker and kept at 300 ° C . The prepolymer was held under a nitrogen cover for 20 h at 300 ° C, removed thereon, left to cool and milled (size 1.2 m, 80% 0.5 mm). The yield of prepolymer after grinding was 90%.

The prepolymer was further processed by pouring it under nitrogen into an aluminum drum which was rotated in an oven. The prepolymer was heated from 204 ° to 354 ° C and held at the higher temperature for 1 h.

After cooling, the (resulting polymer was obtained in the form of a free-flowing powder.

Example IV

The procedure of Example III was repeated exactly using the same materials and procedures with the only exception that 0.067 g of potassium sulfate with the monomer charge was charged to the reaction vessel.

The endothermic peaks measured by DSC (Differential Scanning Calorie Meter) for the first and second heating cycles were determined and listed below in Table B 30 along with the percent retention of the height of the endothermic peak.

TABLE B

Percentage retention Endothermic peak (DSC) of the heating cycle height the endothermic peak le_2e_ 35 Example III 34 422 417 *

Example IV 107 416 429 if The peak observed in this case is of a broad and diffuse character and cannot be considered a sharp pronounced peak.

Similar comparative tests were performed for a number of other polyesters, the control being prepared according to the procedure of Example I and the potassium sulfate-containing polyester prepared according to the procedure of Example II. The results are shown in Table C below.

TABLE · C

K2SO ^ add Percentage Endothermic peak 10 ppm added retention of (DSC) heating the height cycle of the final 2nd _ theme peak _

Example V 0 27 414 412 * 15 Example VI 110 71 414 422

Example VII 0 40 418 417 *

Example VIII 110 75 422 426

The peak observed in this case is of a broad and diffuse nature and cannot be considered a sharp pronounced peak.

As can be seen, the salt-containing polyester showed a significantly improved percentage retention of the height of the endothermic peak.

Comparisons are presented in Table D between controls prepared according to Example I and salt-containing polyesters prepared according to Example II.

The same control was used in examples Χ ,! XII, XVI, XX and XXII, but each is disclosed separately to allow a more direct comparison with the polyesters of Examples IX, XI, χν, XIX, and XXI.

TABLE D

- retention percentage salt cation ppm

Example IX aluminum acetate 98 50

Example X control 0 22

Example XI calcium acetate 152 35

Example XII control .0 22 j

Example XIII copper acetate 84 84;

Example XIV control 0 32

Example XV Inagnesium acetate 126 86 8403066 - * - - 10 -

Example XVI control 0 22

Example XVII potassium chloride 100 70

Example XVIII control 0 18

Example XIX sodium acetate 73 38 5 Example XX control 0 22

Example XXI sodium sulfate 73 38

Example XXII control 0 22

Similar significant improvements in percent retention compared to controls showing broad or diffuse peaks for the two cycle were obtained when the following salts were used in place of the salts specifically listed in Table C: calcium sulfate, magnesium terephthalate , potassium acetate, potassium phosphate and potassium bisulfate.

Example XXIII

A reaction vessel was charged with 156.5 kg of 4,4'-dihydroxybiphenyl, 233 kg of p-hydroxybenzoic acid, 140 kg of terephthalic acid, 407 kg of acetic anhydride and 57.0 g of potassium sulfate. The mixture was covered with nitrogen and heated to reflux with stirring for at least 3 h. Distillation without recirculation was then carried out for about 5.5 hours, while the temperature of the reaction mixture was raised to 315 ° C. At this point, 416.0 g of distearyl pentaerythritol diphosphite was added and after 10 min the thick melt (93.3% conversion based on the yield of distillate) was poured into an insulated stainless steel dish, covered with nitrogen and left to cool. The mass was then removed and ground (size 1.2 mm, 80% <1 0.5 mm).

The prepolymer was further processed by circulating it under nitrogen in a rotary oven. The prepolymer was heated from ambient temperature to 365 ° C and cooled immediately thereafter. The resulting polymer was obtained in the form of a free-flowing powder. The polymer is characterized by first and second endothermic peaks of 416 ° 35 and 418 ° C, respectively, and by first and second exothermic starting points of 377 ° and 379 ° C, respectively.

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Example XXIV

A series of 65 runs were conducted, preparing polyesters according to the procedure of Example XXIII using 93 ppm of potassium sulfate based on the final polymer. The mean start of the exotherm in the first cycle was determined to be 377.8 ° C and the mean start of the exotherm in the second cycle was determined to be 378.4 ° C. The proximity of these points is particularly significant with respect to consistency and reproducibility for injection molding operations. The products obtained by injection molding the polyesters were of very good quality.

In the above tables, the amount of salt is based on parts per million in the finished polymer.

In the above examples and in the still following claims, the term "further processing" refers to the solid state polymerization.

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Claims (8)

A process for the preparation of an aromatic polyester, wherein the starting materials are condensed by heat to form a prepolymer and then the prepolymer is further processed to form a polymer of the desired degree of polymerization, characterized in that a salt is incorporated in the reaction procedure prior to the completion of the polymerization. A method according to claim 1, characterized in that the polyester contains recurring units of one or more of formulas 1-6 of the formula sheet, 0. II where x stands for O, S, -C-, NH or SC ^ and n stands for 0 or 1 and the sum of the integers p + q + r + s + t + u in the units present is between 3 and 800. Method according to claim 1 or 2, characterized in that the salt is added in an amount of 25-500 ppm. Method according to claims 1-3, characterized in that the salt is an organic salt. 5. Process according to claims 1-3, characterized in that the salt is an inorganic salt. 6. Process according to claims 1-5, characterized in that the salt is an alkali metal salt. Process according to claims 1 to 5, characterized in that the salt is an alkaline earth metal. 8. Process according to claim 6, characterized in that the salt is potassium sulphate. Process according to claims 1-8, characterized in that the addition of the salt takes place in the monomer charge. The method according to claim 1, characterized in that the salt is selected from a group of aluminum acetate, calcium acetate, calcium sulfate, copper acetate, magnesium acetate, magnesium terephthalate, potassium acetate, potassium chloride, potassium phosphate, sodium acetate, sodium sulfate and potassium bisulfate. 8403066 j NL 32150 Pf / ed Belongs to patent application Attn. Dart Industries Ine. ..... '' ...... 'FORMULA SHEET 1 L Jp 2 —OC— (X) n— ^ Vco Jq 3 —o— (X) n — o 4 • ["" "CO-00- · L Js 5 ~ [oc- € 0 ~ co "L ^ v -H 6 —o - [- | i 4 —o-- 840 3 0 5 6 L Ju NL 32150 Pf / ed Belongs to patent application t" n " v. Dart Industries Ine._ FORMULA SHEET 2 ......................... - - "11 Γ o Ί 7 R1 — o ^ ryl — or2 L Jp Γ O - O 'η 8 L Jq .I? _0_i_o-Q4.o-0-0-o-- 10 o 11 - L Jp 84 0 3 0 S 6