CH664365A5 - METHOD FOR THE PRODUCTION OF COMPLETELY AROMATIC OXYBENZOYL HOMO OR COPOLYESTERS THAT CAN BE MELTED. - Google Patents

Description

The present invention relates to a process for the production of melt-processable, completely aromatic oxybenzoyl homo- or copolyesters with reproducible melting and crystallization temperatures, as defined in claim 1, to completely aromatic oxybenzoyl-homo- or produced by this process copolyester and the use thereof for the manufacture of articles by injection molding.

It is known that such polyester resins can be produced by various polymerization processes, including suspension polymerization and bulk polymerization. Of these processes, the bulk polymerization process is probably the most convenient in terms of economy. However, since the aromatic poly-20 esters 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 poor.

Another difficulty is to obtain uniform resin characteristics from lot to lot. It is obvious that fluctuations in the molding conditions are undesirable in technical operation 30 and can lead to poor operating efficiency and unacceptable differences in the molded articles.

For these reasons, efforts have therefore been vigorously made to develop a process by which the disadvantages mentioned above can be avoided and which enables the creation of a polyester molding material from which objects with a pleasing and uniform appearance and properties can be obtained.

According to the invention, a polymer with an extremely low degree of decolorization and excellent heat stability, which could not previously be achieved after conventional bulk polymerization, can be obtained in constant quality.

The object of the present invention is to provide a method for producing an aromatic polyester with an extremely low degree of decolorization and excellent heat stability.

Another object of the invention is to provide an improved method for the uniform and economical production of aromatic polyesters of acceptable quality.

Another object of the invention is to provide a polyester with reproducible melting and crystallization temperatures.

55 Further objects and applications of the present invention can be found in the following detailed description. However, it is apparent that the detailed description and specific examples, while representing preferred embodiments of the invention, are only intended to illustrate the invention, since various changes and modifications within the spirit of the invention will be apparent to those skilled in the art from this detailed description.

It has been found that a process which eliminates the problems encountered in carrying out the processes according to the prior art and creates polyester resins whose use is not hampered by the disadvantages mentioned is that an alkaline earth metal

3rd

664 365

tall salt or an alkali salt, preferably potassium sulfate, is present in the heat condensation of the monomers in an amount sufficient to render the melting and crystallization temperatures of the polymer substantially reproducible in relation to melt processing.

The aromatic polyesters are e.g. from combinations of recurring units of one or more of the following formulas:

(x)

oc

(X)

n II

- o

(x> n-

III

Oil

IV

^ ° cCC>

O

Ii where x is O, S, C-, NH or S02 and n is 0 or 1 and the total number of integers p + q + r + s + t + u in the available units is about 3 to about 800.

Combinations of the above units include combining the carbonyl flu 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 can be present in a single copolyester. The simplest type would be the homopolyesters of units I or IV. Other combinations include mixtures of units II and III, II and VI, III and V, V and VI, and I and IV.

The functional groups are preferably in the para (1,4) positions. However, they can also be in the meta (1,3) position to each other. In the naphthalene units, it is particularly advantageous if the functional groups are in 1,4; 1.5 and 2.6 are. Such groups can also be arranged in the meta position to each other.

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 available, the ratio of q / r, q / u, t / r, t / u, 2Ü, JÜ and —— of about r r + u r + u

Vary from 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, phenyl p-hydroxybenzoate, p-acetoxybenzoic acid and isobutyl p-acetoxybenzoate. The materials from which the units of Formula II can be derived include terephthalic acid, isophthalic acid, diphenyl terephthalate, di-ethyl 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'-bisphenyl; p, p'-oxybisphenol; 4,4'-dihydroxybenzophenone; Resorcinol and hydroquinone. A review shows which of these materials are also suitable for giving the units of the formulas VI-VIII.

25th

30th

35

40

60

65

V] u

Examples of monomers represented by Formula IV are 6-hydroxy-1-naphthoic acid; 5-acetoxy-l-naphthoic acid and phenyl 5-hydroxy-l-naphthoate. Monomers corresponding to formula V 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 corresponding 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 include those with recurring units of formula VII:

45

(VII)

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

A preferred class of oxybenzoyl polyesters are those of the formula VIIa

55

O II • C

OR

(Vlla)

wherein R1 is selected from the group consisting of benzoyl, lower alkanoyl, or preferably hydrogen; R2 represents hydrogen, benzyl, lower alkyl or preferably phenyl; and p is an integer from 3 to 600, preferably from 30 to 200. These values of p correspond to a molecular weight of about 1000 to 72,000, preferably 3500 to 25,000. The synthesis of these polyesters is described in detail in U.S. Pat. Patent application Serial No. 619 577 from 1.

March 1967 entitled "Polyesters Based on Hydroxybenzoic Acids", which has now been dropped. To this application, to which in US Pat. No. 3,668,300

664 365

Reference is made in connection with the present invention.

The oxybenzoyl polyesters according to the invention are also copolyesters with repeating units of the formulas VII, VIII and IX:

wherein X is -O- or -S02-; m represents 0 or 1 and n represents 0 or 1; q: r = 10:15 to 15:10; p: q = 1: 100 to 100: 1; p + q + r = 3 to 600, preferably 20 to 200. The carbonyl groups of the units of the formula I or III are bonded to the oxy groups of the units of the formula I or IV;

The synthesis of these polyesters is described in detail in US Pat. No. 3,637,595 relating to “P-oxybenzoyl copolyesters”, which is incorporated in the present description as a reference.

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

The polyesters which can be used in the present invention can also be chemically modified in various ways, 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, but they can be substituted by non-interfering substituents such as 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. However, an alkaline earth metal salt is preferably used. In particular, the following salts can 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 hydrogen sulfate.

Although the salt can be added at any stage in the process, it has been found to be particularly effective and has resulted in significantly better properties in the articles molded from the oxybenzoyl polyester resin when the salt is introduced with 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 if the addition is carried out at a low temperature. Generally, the salt was added in a range from about 25.0 ppm to about 500 ppm. The

- '' (IX)

r the oxy groups of the units of the formula I or IV are bonded to the carbonyl groups of the units of the formula I or III.

The preferred copolyesters are those with recurring units of formula X:

(X)

25th

Exact mechanism, which is why the processability of the polyester and the appearance and properties of the articles molded from the polyester are significantly improved by the addition of the salts mentioned, is not quite apparent. 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 if the salts mentioned are used in the production of the polyesters. 35 The aromatic oxybenzoyl polyester polymers are known to have an endothermic transition, which corresponds to a melting of the polyester. Upon cooling, an exothermic transition or crystallization takes place. Where a strong exothermic exotherm is observed, the transitions are described as reversible. Observations and the results reported in the following tables demonstrate that the addition of a salt such as potassium sulfate results in a significant improvement in the reversibility of the 45 peaks determined in a differential scanning calorimeter (DSC).

When determining the retention of the peak height, the endothermic heat tone for the first and the second heating cycle is recorded on the same scale. The distances from the baseline to the maxima are averaged and the height of the peak of the first cycle is divided by the height of the peak of the second cycle (x100). This value is referred to as “percentage retention”.

When measuring the endothermic exotherm on an aromatic polyester that does not contain salt, it has been found that the peaks of the second cycle are difficult to define at the start of the transition and make the width or width of the heating curve difficult To determine peak. Accordingly, the temperature change between the beginning of the transition and the occurrence 60 of the maximum temperature is graded and a warming curve is created which resembles a slightly sloped or rounded hill. Such a 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 Zy-65 cycle, which are obtained in cases in which a salt was added in the preparation of the aromatic polyesters in accordance with the present invention, are sharp and clear at well-defined temperature curves.

5

664 365

ven, whereby the temperatures at the beginning of the transition and at the peak maximum are easy to determine.

The invention is explained in more detail by the following examples, without restricting the invention, the aim of which is defined in the attached patent claims.

example 1

A reaction kettle was charged with 121.5 kg of 4,4'-dihydroxy-biphenyl, 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 heated to reflux with stirring, refluxing was continued for at least 3 hours. Distillation without reflux was then started. The mixture was distilled for about 5.5 hours, the temperature of the reaction mixture being raised to 315.degree. At this point 0.322 kg of distearylpentaerythritol 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% <0.5 mm). The yield of prepolymers after milling was 90%.

The prepolymer was further processed by turning under nitrogen in a rotary kiln. The prepolymer is heated from room temperature to 365 ° 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 and using the same materials and process steps, with the only exception that 57 g of potassium sulfate were added to the reaction kettle with the monomeric charge.

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

Table I

DSC Endothermic Peak Warming Cycle 1. 2.

DSC exothermic heat tone, beginning 1. 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, clearly cut peak.

Example 3

A reaction kettle was charged with 204.0 g (1.095 mol) of 4,4'-dihydroxybiphenyl, 301.1 g (2.18 mol) of p-hydroxyben-

Table III

zoic acid, 181.1 g (1.09 mol) of terephthalic acid and 526.6 g (5.158 mol) of acetic anhydride, charged with nitrogen and heated to reflux with stirring; refluxing was continued for at least 3 hours. Distillation without reflux was then started and distilled for about 5 1/2 hours, raising the temperature of the reaction mixture to 315 ° C. At this point 0.76 g of distearilpenta-erythritol diphosphite was added and after 10 minutes the thick melt (93.3% conversion based on distillate yield) was placed in a stainless steel beaker lined with aluminum foil which was kept at a temperature was kept at 300 ° C, poured. The prepolymer was kept under a nitrogen blanket at 15,300 ° C. for 20 hours, then removed, allowed to cool and ground (size <1.2 mm, 80% <0.5 mm). The yield of prepolymers after milling was 90%.

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

25 Example 4

The procedure of Example 1 was repeated exactly using the same materials and process steps, with the only exception that 0.067 g of 30 potassium sulfate was added to the reaction kettle along with the monomer feed.

The DSC (differential scanning calorimeter) endothermic peaks for the first and second heating cycles were determined and recorded below in Table II along with the percentage retention of the endothermic peak height 35.

Table II

40

Example 3 45 Example 4

Percentage retention of the endothermic peak height

34 107

DSC endothermic peak warming cycle

1.

422 416

2nd

417 * 429

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

Similar comparisons were made for various other polyester, the control being made in accordance with the procedure of Example 1 and the polyester containing potassium sulfate in accordance with the procedure of Example 2. The results are summarized in Table III below.

55

K2S04-

Percentage retention

DSC endothermic peak

Addition of endothermic

Warming cycle

ppm

Peak height

1.

2nd

Example 5

0

27th

414

412 *

Example 6

110

71

414

422

Example 7

0

40

418

417 *

Example 8

110

75

422

426

* The peak recorded here is broad and indistinct and not a sharp, clearly

intersected peak.

664 365

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

Table IV shows comparisons between control samples made in accordance with Example 1 and salt containing polyesters made in accordance with Example 2. The same control polyesters were used in Examples 10, 12, 16, 20 and 22, but they were given separately in order to allow a more direct comparison with the polyesters according to Examples 9, 11, 15, 19 and 21.

Table IV

Salts

PPM

Percental

Cation tuelle

Kick

tion

Example 9

Aluminum acetate

98

50

Example 10

control

0

22

Example 11

Calcium acetate

152

35

Example 12

control

0

22

Example 13

Copper acetate

84

84

Example 14

control

0

32

Example 15

Magnesium acetate

126

86

Example 16

control

0

22

Example 17

Potassium chloride

100

70

Example 18

control

0

18th

Example 19

Sodium acetate

73

38

Example 20

control

0

22

Example 21

Sodium sulfate

73

38

Example 22

control

0

22

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 in place of the salts specifically listed in Table III: calcium sulfate, magnesium terephthalate, potassium acetate, potassium phosphate and potassium hydrogen sulfate.

Example 23

A reaction kettle was charged with 156.2 kg of 4,4'-dihydroxy-biphenyl, 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, the reflux being continued for at least 3 hours. Distillation without reflux was then started and distilled for 5.5 hours, raising the temperature of the reaction mixture to 315 ° C. At this point 416.0 g of distearylpenta-erythritol diphosphite was added and after 10 minutes the thick melt (93.3% conversion based on the 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 further processed by turning under nitrogen in a rotary kiln. The prepolymer was heated from room temperature to 365 ° C and cooled immediately. The resulting polymer was obtained as a free flowing powder. The polymer is characterized by first and second endothermic peaks of 416 ° and 418 ° and by first and second exothermic points of 377 ° and 379 °.

Example 24

A series of 65 throughputs were made in which polyesters were made in accordance with the procedure of Example 33, using 93 ppm of potassium sulfate based on the final polymer. The mean average start of exothermic exotherm in the first cycle was found to be 377 8 °, the average mean start of exothermic exotherm in the second cycle was 378.4 °. The close proximity of these points is extremely important in terms of consistency and reproducibility in injection molding processes. The products obtained from the polyesters by injection molding were of high quality.

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

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

6

5

10th

15

20th

25th

30th

35

40

45

c

Claims (5)

664 365 2. The method according to claim 1, characterized in that the salt is added in an amount of 0.0025 to 0.05%, based on the weight of the polymer produced. 2nd PATENT CLAIMS 1. Process for the production of meltable, completely aromatic oxybenzoyl homo- or copolyesters with reproducible melting and crystallization temperatures, which have repeating units of the following formulas: -0-4 + • - £> VII p vili q where X is -O- or -S02-; m represents 0 or 1; n represents 0 or 1; q: r represents 10:15 to 15:10; p: q represents 1: 100 to 100: 1; p + q + r represents 3 to 600; the carbonyl groups of the units of the formula VII or VIII are bonded to the oxy groups of the units of the formula VII or IX; and the oxy groups of the units of the formula VII or IX are bonded to the carbonyl groups of the units of the formula VII or VIII; by bulk polymerization by means of heat condensation of completely aromatic polyester-forming monomers to a prepolymer and subsequent further treatment of the prepolymer to form a completely aromatic polymer with the required degree of polymerization, characterized in that the monomers in the presence of an alkali metal or alkaline earth metal salt in an amount sufficient in order to make the melting and crystallization temperatures of the polymer essentially reproducible in relation to processing in the melt, which subjects heat condensation. 3. The method according to claim 1 or 2, characterized in that a potassium or magnesium salt is used as the salt. 4. The method according to any one of claims 1 to 3, characterized in that a sulfate or chloride is used as the salt. 5. Process according to claims 3 and 4, characterized in that potassium sulfate is used as the salt. 6. The method according to any one of claims 1 to 5, characterized in that the monomers comprise an aromatic dicarboxylic acid, a p-hydroxybenzoic acid and an aromatic diol. 7. The method according to claim 6, characterized in that the monomers comprise terephthalic acid, p-hydroxybenzoic acid and dihydroxybiphenyl. 8. The method according to claim 6 or 7, characterized in that the molar ratios of the monomers approx. L: approx. 2: approx. 1. 9. The method according to any one of claims 1 to 8, characterized in that the condensation of the monomers is carried out by alkanoylation with an acid anhydride. 10. Fully aromatic oxybenzoyl homo- or copolyester. produced by the method according to one of claims 1 to 9. 11. Homo- or copolyester according to claim 10, characterized in that it has a melting temperature of at least 378 C. 12. Use of the completely aromatic oxybenzoyl homo- or copolyester according to claim 10 or 11 for the production of objects by injection molding. 5 DESCRIPTION