DE3443219A1 - METHOD FOR PRODUCING AROMATIC POLYESTERS - Google Patents

Description

dr. V. SCHMIED-KOWARZIK · dr. P. WEINHOLD · dr. P. BARZ · Munich dipping. G. DANNENBERG · dr. D. GUDEL- dipl-ing. S. SCHUBERT · Frankfurt

APPROVED REPRESENTATIVES AT THE EUROPEAN PATENT OFFICE

3-

SIEGFRIEDSTRASSE 8 βΟΟΟ MUNCHEN 4O

TELEPHONE: (089) 335024 + 335025 TELEGRAMS: WIRPATENTS TELEX: 5215679

Case: RC-1570-M026

DART -

Sanders Road
Northbrook, Illinois 60062
United States

METHOD FOR MANUFACTURING
AROMATIC POLYESTERS

Background of the invention · * k · '

The present invention relates to an improved method for "making copolyesters. In particular The invention relates to a process for the production of oxybenzoyl polyesters from arcmüschen dicarboxylic acids, Dihydroxyphenols and p-hydroxybenzoic acid compounds as starting materials.

₁ q It is known that such polyester resins can be prepared by various polymerization processes, including suspension polymerization and bulk polymerization. Of these methods, the bulk polymerization method is probably that in terms of economy

2g most expedient. However, since the aromatic polyester one have 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 polyesters are often discolored and defective.

A further difficulty consists in obtaining uniform shape characteristics of the resin from batch to batch obtain. Obviously, variations in molding conditions are undesirable in industrial operation and poor operational efficiency and unacceptable Differences in the shaped objects can result.

For these reasons, it has therefore been vigorously sought to develop a method by which the above-mentioned Disadvantages could be avoided and which enables the creation of a polyester molding material from which articles with pleasing and uniform appearance and properties can be obtained.

The invention * & ♦

According to the invention, a polymer with an extremely low degree of discoloration and a marked Thermal stability that could not previously be achieved by conventional bulk polymerization is obtained will.

The present invention is to provide a process for producing _n an aromatic polyester having

an extremely low degree of discoloration and excellent heat stability.

Another object of the invention is to provide an improved method of smooth and economical Production of aromatic polyesters of acceptable quality.

Another object of the invention is to provide a polyester mi
temperatures,

Polyester with reproducible melting and crystallization

Other subjects and uses of the present Invention can be found in the following detailed description. It is obvious, however, that the detailed Description and specific examples, while representing preferred embodiments of the invention, are only serve to explain the invention, as various changes and modifications within the inventive concept for the Are apparent from this detailed description.

It has been found that a method which is identical to those used in carrying out the methods of the prior art eliminates occurring problems and creates polyester resins,

_o _ their use is not hindered by the disadvantages mentioned whether

is that a salt, especially an alkaline earth metal salt or an alkali salt and preferably potassium sulfate during the preparation of the resin and in particular for

Pre-polymer melt is added prior to further processing to the end product with the desired degree of polymerization.

The aromatic polyesters which can be produced in the course of the process according to the invention exist from combinations of recurring units of one or more of the following formulas:

- ο

(X)

11th

- OC

(X)

η Il

co -

III

ο -

co

IV

--OC

co

Vt

"1

where χ is 0, S, -C-, NH or SO ₂ and n is 0 or 1 and the total number of integers p + q + r + s + t + u in the units present is from about 3 to about 800.

Combinations of the above units include the union of the carbonyl group of formulas I, II, IV and V with the oxy group of formulas I, III, IV and VI. In most common combinations, all units of the above formulas be present in a single copolymer. The simplest type would be the homopolymers of units I or be IV. Other combinations include mixtures of Units II and IH, II and VI, III and V, V and VI, and I. and IV.

The functional groups are preferably in the para- (I, Ή positions. However, they can also lie in the meta- (1,3) position to one another. In the case of the naphthalene units, it is particularly advantageous if the functional groups to one another in 1,4; 1.5 and 2.6 lie. Such groups can also be in the meta position to one another be arranged.

The symbols p, q, r, s, t and u are integers and denote the number of units present in the polymer. The total number (p + q + r + s + t + u) can vary between 3 and 800 and, if any, the ratio of q / r, q / u, t / r, t / u, q + t , q + t and t of about

r r + u r + u

10/11 to about 11/10 with the most preferred ratio being 10/10.

Examples of materials from which the

Units of the formula I can be obtained are p-hydroxybenzoic acid, pheny1-p-hydroxybenzoate, p-acetoxybenzoic acid and isobutyl p-acetoxybenzoate. the Materials from which the units of 'Formula II are derived

include terephthalic acid, isophthalic acid, diphenyl terephthalate, diethyl isophthalate, methyl ethyl terephthalate and the isobutyl half ester of terephthalic acid. Examples of compounds from which the units of the formula III result are p, p * -bisphenol; ρ, ρ ¹ -oxybisphenol; 4,4'-dihydroxybenzophenone; Resorcinol and hydroquinone. A review shows which of these materials are also suitable for producing the units of the formulas VI - VIII.

Examples of represented by Formula IV

Monomers are 6-hydroxy-1-naphthoic acid; 5-acetoxy-1-naphthoeoU

acid and phenyl 5-hydroxy-l-naphthoate. Monomers accordingly of Formula V include 1,4-naphthalenedicarboxylic acid; 1,5-naphthalene dicarboxylic acid and 2,6-naphthalenedicarboxylic acid. The diphenyl esters or dicarbonyl chlorides of these acids can also be used. Examples of monomers according to Formula VI are 1,4-dihydroxynaphthalene; 2,6-diacetoxynaphthalene and 1,5-dihydroxynaphthalene.

Plastics based on oxybenzoyl polyesters are particularly suitable for carrying out the present invention.

The oxybenzoyl polyesters useful in the present invention are generally those having repetitions Units of the formula VI:

10

(VI)

where ρ is an integer from about 3 to about 600.

A preferred class of oxybenzoyl polyesters are those of Formula VII

20th

(VII)

OR ² ,

2g in which R is selected from the group comprising benzoyl, lower-alkanoyl or, preferably, hydrogen is selected; R represents hydrogen, benzyl, lower-alkyl or, preferably, phenyl; and ρ is an integer from 3 to 600, preferably from 30 to 200. These values of ρ correspond to a molecular weight from about 1,000 to 72,000, preferably from 3,500 to 25,000. The synthesis of these polyesters is detailed in US Pat U.S. Patent Application Serial No. 619,577 filed March 1, 1967 entitled "Polyesters Based on Hydroxybenzenes Acids" which has now been dropped. On this registration, referred to in U.S. Patent 3,668,300 is referred to in connection with the present invention. Another preferred class of oxybenzoyl polyesters are copolyesters with repeating units

Formula VII, VIII and IX

(VIII)

(IX)

wherein X is -0 or -SO.-; m represents 0 or 1 and η represents 0 or; q: r = 10:15 to 15:10; p: q = 1: 100 to 100: 1; ρ + q + r = 3 to 600, preferably 20 to 200. The carbonyl groups of the units of the formula I or III are attached to the Oxy groups of the units of the formula I or IV are bonded; are the oxy groups of the units of formula I or IV bonded to the carbonyl groups of the units of the formula I or III.

The preferred copolyesters are those with repeating units of the formula X:

(X)

The synthesis of these polyesters is detailed in US Pat. No. 3,637,595 relating to "P-oxybenzoyl copolyesters", which is included in the present description as a reference.

The bulk condensation of aromatic polyesters is described in the patent literature and encompasses broadly an alkanoylation stage in which a suitable dicarboxylic acid, hydroxybenzoic acid and a diol with a Acid anhydride are reacted, and a prepolymerization stage in which the reaction product of the first stage a prepolymer is polycondensed, after which the prepolymer is heated to form a polycondensate with the desired To form degree of polymerization.

The polyesters useful in the present invention can also be chemically in various ways 'be modified, for example by inclusion in the polyester of monofunctional reaction components, such as benzoic acid or tri- or higher functional reaction components such as trimesic acid or cyanuric chloride. the Benzene rings in these polyesters are preferably unsubstituted, however, they can be substituted by non-interfering substituents, such as, for example, halogen, such as chlorine or Bromine, lower alkoxy such as methoxy, and lower alkyl such as Methyl.

The salt can be an organic or an inorganic salt be. However, an alkaline earth metal salt is preferably used. In particular, the following salts can be used be: aluminum acetate, calcium acetate, calcium sulfate, Copper acetate, magnesium acetate, magnesium terephthalate, potassium acetate, potassium chloride, potassium phosphate, sodium acetate, Sodium sulfate and potassium hydrogen sulfate.

Although the salt can be added at any stage of the process, it has been found to be particularly effective and resulted in significantly better properties in the articles molded from the oxybenzoyl polyester resin, when the salt is introduced with the monomer charge.

■ Μ-

The salt can be added as a solid or as a solution at a temperature above the melting point of the salt will. It is also possible to add the salt in a solution if the addition is at a low temperature is carried out. Generally, the salt was added in a range from about 25.0 ppm to about 500 ppm. The exact one Mechanism, which is why the processability of the polyester and the appearance and properties of the polyester Shaped objects are significantly improved by the addition of the salts mentioned, is not entirely discernible.

However, it has been observed that the retention of peak heights with repeated endothermic transitions and the achievement of consistent exothermic transitions are significantly and materially improved when making the polyester the salts mentioned are used.

The aromatic oxybenzoyl polyester polymers are known to have an endothermic transition, which corresponds to a melting of the polyester. An exothermic occurs on cooling Transition or crystallization. Where a strong exothermic heat is observed, the transitions are called described reversibly. Observations and the results given in the following tables prove that the addition of a salt, such as potassium sulfate, significantly improves the reversibility of the in one Differential scanning calorimeter (DSC) detected peaks result.

In determining the retention of the peak height, the endothermic heat tone is used for the first and the second Warming cycle recorded on the same scale. the Distances from the baseline to the maxima are determined and the height of the peak of the first cycle becomes divided by the height of the peak of the second cycle (x100). This value is called the "percentage retention" designated.

When measuring the end $ othermen calorific value on an aromatic Polyester containing no salt has been shown to be the beginning of the transition at the peaks of the second cycle difficult to define and the width or breadth of the heating curve makes it difficult to determine the peak. Accordingly, the temperature change is graded between the beginning of the transition and the occurrence of the maximum temperature and creates a warming curve that resembles a slightly sloping or rounded hill. One such peak is referred to in the present description and in particular in the examples as a broad or fuzzy peak. The peaks of the second cycle obtained in those cases in which the aromatic polyester in In accordance with the present invention a salt was added are sharp and clear when well-defined Temperature curves, whereby the temperatures at the beginning of the transition and at the peak maximum are easy to determine.

The invention is illustrated by the following examples, without restricting the invention, the aim of which is in the accompanying one Claims is defined, explained in more detail.

Example 1: A reaction kettle was charged with 121.5 kg of 4,4'-dihydroxybiphenyl, 179.6 kg of p-hydroxybenzoic acid, 107.9 kg of terephthalic acid and 312.9 kg of acetic anhydride. It was blanketed with nitrogen and refluxed with stirring, refluxing continued for at least 3 hours. Distillation was then started without reflux. It was distilled for about 5.5 hours, during which the temperature of the reaction mixture was increased to 315 ° C. At this point 0.322 kg of distearyl pentaerythritol diphosphite was added and after 10 minutes the thick melt (93.3% conversion based on distillate yield) was poured into an insulated stainless steel trough and allowed to cool under a nitrogen blanket. The mass was then removed and ground (size <1.2 mm, 80% x <0.5 mm). The prepolymer yield after milling was 90%.

f5

f5

The prepolymer was processed further by turning it under nitrogen in a rotary kiln. The prepolymer is then heated from room temperature to 365 ⁰ C at a rate of 23 ° C / h and cooled immediately. The resulting polymer is obtained as a free flowing powder.

Example 2: The procedure of Example 1 was repeated in exactly the same manner, using the same materials and procedures, with the only exception that 57 grams of potassium sulfate was added to the reaction kettle with the monomeric charge.

The DSC (differential scanning calorimeter) endotherms and exothermic peaks for the first and second heating cycles were determined and are shown in Table I below refer to.

TABLE I.

DSC Endothermic Peak DSC Exothermic Heat-Warming Cycle Tint, Beginning

L? _: L 2.

Example 1 410 weak * 366 355

Example 2 421 419 381 381

* The peak recorded here is a broad and indistinct peak and not a sharp, well-cut peak. 25th

Example 3: A reaction kettle was charged with 204.0 g (1.095 mol) 4,4'-dihydroxybiphenyl, 301.1 g (2.18 mol) p-hydroxybenzoic acid, 181.1 g (1.09 mol) terephthalic acid and 526, 6 g (5.158 moles) of acetic anhydride charged with nitrogen

OQ covered and heated to reflux with stirring; The heating reflux was continued for at least 3 hours. The distillation was then carried out without refluxing started and distilled for about 5 1/2 hours, the temperature of the reaction mixture increased to 3T5 ° C

_g5 became. At this point, 0.76 grams of distearil pentaerythritol diphosphite was added and after 10 minutes the thick melt (93.3% conversion based on distillate yield) in a stainless steel beaker was lined with

-K-

Aluminum foil, which was kept at a temperature of 300 ° C., poured in. The prepolymer was kept for 20 hours under a nitrogen blanket at 300 ⁰ C, then removed, allowed to cool and ground (size <.1, 2mm, 80% <0.5 mm). The prepolymer yield after milling was

The prepolymer was treated by flipping under nitrogen in an aluminum drum rotated in an oven. The prepolymer was heated from 204 to 354 ⁰ C and maintained for an hour at the higher temperature. After cooling, the polymer was obtained as a free flowing powder.

Example 4; The procedure of Example 1 was repeated using exactly the same materials and procedures, with the sole exception that 0.067 grams of potassium sulfate was added to the reaction kettle along with the monomer charge.

The DSC (differential scanning calorimeter) endothermic peaks for the first and second heating cycles were determined and in Table II below along with the percent retention of endothermic peak height recorded

Table II

Percentage retention DSC endothermic peak of the endothermic peak heating cycle height 1_. 2_.

Example 3 34 422 417 *

Example 4 107 416 429

* The peak recorded here was broad and indistinct and not a sharp, clearly cut peak 35

Similar comparisons were made for various other polyesters with the control in accordance with FIG Procedure according to Example 1 and containing potassium sulfate

414 412 * 414 422 418 417 * 422 426

Polyester was prepared in accordance with the procedure of Example 2. The results are in the following Table III summarized.

TABLE III

K2SO4- Percentage retention DSC endothermic peak Addition of the endothermic peak heating cycle ppm height 1_. 2 ^ _

Example 5 0 27

Example 6 110 71

¹⁰ Example 7 0 40

Example 8 110 75

The peak recorded here is broad and indistinct and

no sharp, clearly clipped peak.
15th

As demonstrated above, the salt-containing polyesters showed significant improvement in
percent retention of endothermic peak height.

In Table IV, comparisons between control samples,

made in accordance with Example 1, and salt-containing polyesters made in accordance with
Example 2 given. The same control polyesters were used in Examples 10, 12, 16, 20 and 22, but they are separately listed for more direct comparison
with the polyesters according to Examples 9, 11, 15, 19 and 21 to allow.

TABLE IV

9 Salts PPM Percentual 10 Aluminum acetate cation Retention example 11th control 98 50 30 example 12th Calcium acetate 0 22nd example 13th control 152 35 example 14th Copper acetate 0 22nd example 15th control 84 84 example 16 Magnesium acetate 0 32 example 17th control 126 86 example 18th Potassium chloride 0 22nd example 19th control 100 70 ^d ° example 20th Sodium acetate 0 18th example 21 control 73 38 example 22nd Sodium sulfate 0 22nd example control 73 38 example 0 22nd

/ έ.

Similar significant improvements in percent retention compared to the control products with broad or indistinct peaks in the second cycle were obtained when the following salts were used the salts specifically specified in Table III were used: calcium sulfate, magnesium therephthalate, potassium acetate, Potassium phosphate and potassium hydrogen sulfate.

Example 23; A reaction kettle was charged with 156.2 kg of 4,4'-dihydroxybiphenyl, 233.1 kg of p-hydroxybenzoic acid, 140.1 kg of terephthalic acid, 406.4 kg of acetic anhydride, and 57.0 g of potassium sulfate. The kettle was blanketed with nitrogen and heated to reflux with stirring, with reflux continued for at least 3 hours. Was then started with the distillation without reflux and distilled for 5.5 hours, the temperature of the reaction mixture was raised to 315 ⁰ C. At this point 416.0 grams of distearyl pentaerythritol diphosphite was added and after 10 minutes the thick melt (93.3% conversion based on distillate yield) was poured into an insulated stainless steel trough, blanketed with nitrogen and allowed to cool. The material was then removed and ground (size ^ - 1.2 mm, 80% < 0.5 mm).

The prepolymer was treated further by flipping it under nitrogen in a rotary kiln. The prepolymer was heated from room temperature to 365 ⁰ C and cooled immediately. The resulting polymer was obtained as a free flowing powder. The polymer is characterized by a first and a second endothermic peak of 416 ° and 418 ° and by a first and second exothermic point of 377 ° and 379 °.

V fa. Example 24; A series of 65 throughputs were run making polyesters in accordance with the procedure of Example 33 using 93 ppm potassium sulfate based on the final polymer. The mean average onset of the exothermic warmth in the first cycle was determined to be 377.8 °, the average average onset of the exothermic warmth in the second cycle was 378.4 °. The close proximity of these points is of the utmost importance for consistency and reproducibility in injection molding processes. The products obtained from the polyesters by injection molding were of high quality.

In the tables above, the amount of salt used is based on parts per million (ppm) of the finished polymer.

In the above examples and in the following claims the term continuation or further treatment means the Solid state polymerization.

Claims (10)

Patent claims: 1. Process for producing an aromatic polyester by heat condensation of the precursors to form a prepolymer and subsequent further treatment of the prepolymer with formation of a polymer with the required degree of polymerization, characterized in that the reaction process before the A salt is added to the end of the polymerization. 2. The method according to claim 1, characterized in that the polyester comprises recurring units of the group one or more of the formulas: II ic-QQ-co III IV VI . ο includes wherein χ ^represents O, S, ~ X ~ ^{'NH or S0} 2 / ⁿ or is 1, and the sum total of the integers p + q + r + t s + + uin the available units from about 3 to about 800th 3. The method according to claim 2, characterized in that the salt is added in an amount of 25 to 500 ppm. 4. The method according to claim 2, characterized in that an organic salt is used as the salt. 5. The method according to claim 2, characterized in that an inorganic salt is used as the salt. 6. The method according to claim 2, characterized in that an alkali metal salt is used as the salt. 7. The method according to claim 2, characterized in that an alkaline earth metal salt is used as the salt. 8. The method according to claim 3, characterized in that potassium sulfate is used as the salt. 9. The method according to claim 3, characterized in that the addition of the salt takes place together with the monomer charge. 10. The method according to claim 1, characterized in that the salt is selected from the group comprising aluminum acetate, calcium acetate, calcium sulfate, copper acetate, magnesium acetate, magnesium therephthalate, potassium acetate, potassium chloride, potassium phosphate, sodium acetate, sodium sulfate and potassium hydrogen sulfate.