FR2555592A1 - PROCESS FOR PRODUCING AROMATIC POLYESTERS - Google Patents

Abstract

THE PRESENT INVENTION RELATES TO THE PREPARATION OF OXYBENZOYL POLYESTERS, ENABLING IN PARTICULAR THE OBTAINING FROM THESE POLYESTERS MOLDED ARTICLES OF AN IMPROVED APPEARANCE AND SHOWING EXCELLENT PROPERTIES. FOLLOWING THE INVENTION, THE PREPARATION OF THESE POLYESTERS IS FACILITATED BY THE INCORPORATION OF A SALT, IN PARTICULAR AN ALKALINO-EARTH METAL SALT, AND PREFERABLY OF POTASSIUM SULPHATE.

Description

"Process for producing aromatic polyesters" The present invention

  relates to an improved copolyester production process. More particularly, it relates to a process for the production of oxybenzoyl polyesters of dicarboxylic acids.

  aromatic xylics, dihydroxyphenols and

  hydroxybenzoic used as starting materials.

  It is known that such polyester resins can

  can be obtained by different polymerization processes.

  comprising suspension polymerization and bulk polymerization. Among these processes, the bulk polymerization process is perhaps the most economically interesting process. However, since the aromatic polyesters have a high melting point compared to the aliphatic polyesters, such as polyethylene terephthalate, a higher temperature

  is required to maintain the aromatic polyesters.

  in the molten state. Therefore, polymers are

  often colored and have characteristics of

ge amoindries.

  In addition, it has been difficult to obtain uniformity from one batch to another in the molding characteristics of the resin. Obviously,

  variations in the molding conditions are inde-

  in industrial operations and may

  to inefficient returns and differences

  unacceptable in molded articles.

  Intensive research has therefore been carried out to develop a process which eliminates the above-mentioned drawbacks and which provides

  re a polyester molding material from the-

  which one can obtain articles presenting

  pleasant and uniform properties and appearance.

  According to the present invention, a polymer having a degree of

  extremely low discoloration and excellent sta-

  thermal stability, which could have been obtained up to

  present by ordinary mass polymerization.

  An object of the present invention is to provide

  a process for the production of aromatic polyesters

  both an extremely low degree of discoloration and a

excellent thermal stability.

  Another object of the invention is to provide an improved method of producing economic and constant

  of aromatic polyesters of acceptable quality.

  Yet another object of the present invention is to provide polyesters having

  reproducible fusion and crystallization.

  Other details and particularities of the invention

  will emerge from the description given below. We notice-

  ra, however, that the present invention is in no way limited to the preferred embodiments described hereinafter and that many modifications may

  to be made without departing from the scope of this patent.

  It was found that one could foresee a

  given to overcome the problems encountered

  in carrying out the processes of the prior art

  re and giving polyester resins whose use

  The above-mentioned disadvantages do not result from the addition of a salt, in particular an alkaline earth metal salt or an alkaline salt, and preferably potassium sulphate, during the course of the process. preparing the resin and, in particular, the prepolymer melt before the final product reaches the

desired degree of polymerization.

  The wholly aromatic polyesters to which the production process of the present invention applies

  consist of combinations of repetitive fragments

  selected from the group consisting of one or more of the following formulas: ## STR1 ## wherein: ## STR2 ##

L 0

  where VI is 0, S, -A-, NH or SO2, n is 0 or 1 and the total of the integers p + q + r + s + t + u in the fragments present is about 3 to

about 800.

  The combinations of the aforementioned fragments include

  bind the carbonyl group of formulas 1, II,

  IV and V with the oxy group of formulas I, III, IV and VI.

  In the most general combination, all fragments of the above formulas may be present in a single copolymer. The most important embodiment

  simple would consist of homopolymers of fragments

  I or IV. Other combinations consist of mixtures of fragments II and III, II and VI, III and V, V

and VI, and I and IV.

  The location of the functional groups is

  kills preferably in para position (1,4). They can also be arranged in meta position (1,3) relative to each other. With respect to the naphthalene fragment, the most interesting locations of

  functional groups are in positions 1,4, 1,5 and 2,6.

  These groups can also be in meta position

one against another.

  The symbols p, q. r, s, t and u are integers and indicate the number of fragments present in the polymer. The sum total of (p + q + r + s + t + u) can

  vary from 3 to 800 and, where present, the reports

  ports q / r, q / u, t / r, t / u, q + t, q + t and t may r r + u r + u vary from about 10/11 to about 11/10, the ratio

more interesting being 10/10.

  Examples of materials from which the fragments of formula I can be obtained are p-hydroxybenzoic acid, phenyl p-hydroxybenzoate,

  p-acetoxybenzoic acid and iso-p-acetoxybenzoate

  butyl. Materials from which the moiety of formula II can be obtained are terephthalic acid,

  isophthalic acid, diphenyl terephthalate, di-

  ethyl isophthalate, methylethyl terephthalate and hemi

  isobutyl ester of terephthalic acid. Among the

  posed to obtain the fragment of formula III, mention will be made of p, p'-bisphenol, p, p'-oxybisphenol,

  4,4'-dihydroxybenzophenone, resorcinol and hydroquinone

  none.It will be deduced which of these materials also

  suitable for obtaining the fragments of formulas IV-

VI.

  Examples of monomers corresponding to the formula

  IV are 6-hydroxy-1-naphthoic acid, 5-acetic acid,

  toxy-1-naphthalic acid and phenyl 5-hydroxy-1-naphthoate.

  Monomers of formula V are 1,4-acid

  naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid

  boxylic acid and 2,6-naphthalenedicarboxylic acid. We

  may also use diphenyl or chlorinated

  dicarbonyl compounds of these acids. Examples of particular monomers of formula VI are 1,4-dihydroxynaphthalene, 2,6-diacetoxynaphthalene and

1,5-dihydroxynaphthalene.

  Have been particularly interesting in

  the scope of the present invention the plastic materials

  based on oxybenzoyl polyesters.

  The oxybenzoyl polyesters of interest in

  the scope of the present invention are, in a general way,

  neral, repetitive fragments corresponding to the formula

VII:

(V! I)

  wherein p is an integer of about 3 to about

600.

  A preferred class of polyesters oxybenzo

  Zoylics are those of formula VIII:

(VIZX)

R1 O

I_ 2

Ri 0 / C OR P i

  wherein R represents a benzoyl or alkanoyl group

  the lower, or preferably hydrogen, R represents

  hydrogen, benzyl or lower alkyl,

  or preferably the phenyl group, and p is a number

  from 3 to 600, and preferably from 30 to 200. These ranges

  their of p correspond to a molecular weight of about

  1000 to 72000, and preferably 3500 to 25000. The synthesis of these polyesters is described in detail in United States Patent Application No. 619,577,

  deposited on 1 March 1967, and now abandoned,

  "Polyesters Based on Hydroxybenzoic Acids",

  in the context of the present invention to

  reference. This patent application is concerned

  in United States Patent No. 3,668,300.

  Another preferred class of polyesters

  oxybenzoyl are the copolyesters of repetitive fragments

Titrates of formulas IX and X:

(IX)

C C

O o -q S5592 (x)

The

  where x is -0 or -SO2-, m is 0 or 1, n is 0 or 1, q / r is 10/15 to 15/10, p / q = 1 / 100 to 100/1, and p + q + r = 3 to 600 and

preferably 20 to 200.

  The preferred copolyesters comprise fragments

  Repetitive Formula XI: (XI) t C-o

  The synthesis of these polyesters is described in detail.

  tail in the patent of the United States of America

  No. 3,637,595, entitled "p-Oxybenzoyl Copolyesters",

  in the context of the present invention as a

reference.

  Condensation in bulk of aromatic polyesters

  is described in the literature desbrevets and she

  comprises, in a general way, an alkanoyla-

  in which a dicarboxylic acid is reacted

  as appropriate, hydroxybanzoic acid and a diol

  with an acid anhydride, as well as a prepoly-

  wherein the reaction product of the first step is polycondensed to obtain a prepolymer, the prepolymer then being heated to give a polycondensate of the desired degree of polymerization. Polyesters used in the context of

  The present invention can also be modified

  by different means, such as by incorporating

  in the polyester of monofunctional reagents, com-

  benzoic acid, or trifunctional or higher functional reagents, such as

  trimesic or cyanuric chloride. Benzene rings

  in these polyesters are preferably not

  but may be substituted by substitutions

  not interfering, examples of such substitutes

  ants being, among others, halogen atoms, such as chlorine or bromine, lower alkoxy groups,

  such as the methoxy group and the lower alkyl groups.

  such as the methyl group.

  The salt may be an organic or inorganic salt

  than. However, the use of an alkaline metal salt

  earthy is better. More particularly, the following salts may be used: aluminum acetate, calcium acetate, calcium sulfate, copper acetate, magnesium acetate, magnesium terephthalate, potassium acetate, potassium chloride, sodium phosphate

  potassium, sodium acetate, sodium sulphate and bisul-

potassium fate.

  Although we can add salt at a stage

  of the process, it has been found that in order to be

  particularly effective, and to impart substantially superior properties to articles molded from the oxybenzoyl polyester resin,

  add the salt to the monomer charge.

  The salt can be added in the form of a solid

  of, or solution at a temperature above the melting point of the salt. It is also possible to add the

  salt in the form of a solution when the

  This is done at a lower temperature.

  In general, the salt is added over a range of about 25.0 parts per million to about 500

parts per million.

  The exact mechanism according to which

  polyester treatment and the appearance and benefits of

  The properties of the molded articles are substantially improved by the addition of the defined salts not fully understood. However, it has been found that the retention of

  peak heights in repeated thermal transitions

  and the obtaining of repeated exothermic transitions

  Titrates are substantially and materially improved when the salts defined in the treatment are used

polyesters.

  It is known that oxybenzoyl polyesters

  aromatic compounds are polymers which have a

  which corresponds to a fusion of the poly-

  ester. During cooling, a transition or crys-

  Exothermic metallization occurs. When observing

  an important exotherm, transitions are consid-

  as reversible. Observations and results

  The data given in the tables below demonstrate that the addition of a salt, such as potassium sulphate, has substantially improved the reversibility of the detected peaks.

  in the differential scanning calorimeter or CBD.

  To determine the retention of peak heights, endotherms are recorded at the same scale for the first and second heating cycles. The distances from the baseline to the maximums are determined and the height of the first cycle peak is divided by the height of the second cycle peak (x 100). This value represents the

"retention in%".

  When measuring the endotherms on the

  In the second cycle peaks, it was found that in the second cycle peaks it was difficult to define the beginning of the transition and that the width of the heating curve made it difficult to determine the peak. This is how the temperature change between the beginning

  of the transition and the appearance of the maximum temperature

  is progressive, giving rise to a heating curve.

  fage that looks like a gentle slope or a rounded declivity. Such a peak is considered as part of the

  present invention as a broad or diffuse peak.

  The second cycle peaks obtained in the cases oh

  a salt has been incorporated in the treatment of polyes-

  The aromatic flavors of the present invention are sharp and accentuated with well-defined temperature curves, the onset temperatures of the transition and

  maximum peaks being easily determined.

  The invention is illustrated by the following examples:

  which in no way constitute a limitation to it.

Example 1

  A reaction vessel is charged with 121.5kg

  of 4,4'-dihydroxybiphenyl, 179.6 kg of p-hydroxy

  benzene, 108kg of terephthalic acid and 313kg of anhydrous

  of acetic. It is protected with nitrogen and heated with stirring to the reflux temperature,

  heating that is continued for a minimum of 3 hours

  res. Unreacted distillation is then started and continued for about 5.5 hours while raising the temperature of the reaction mixture to 315 C. At this time, 0.32 kg of distearyl pentaerythritol diphosphite is added and after minutes, the thick melt (93.3% conversion relative to distillate production) was poured into an insulated stainless steel pan and allowed to cool under a nitrogen-protective atmosphere. It is then separated and crushed (size <1.2 mm, 80% <0.5 m4).

  in prepolymer after grinding is 90%.

  The prepolymer is advanced by oscillations under a nitrogen atmosphere in a rotary kiln.

  warms the prepolymer from room temperature to

  than 365 C at a rate of 23 C / hour and is cooled im-

  mediately. The resulting polymer is obtained under

me of a dripping powder.

Example 2

  The procedure of Example 1 is repeated using

  the same materials and processes, with the exception

  57 g of potassium sulphate are added to the

  reaction vessel with the monomer charge.

  Endothermic and exothermic peaks are determined

  to the CBD (Differential Scanning Calorimeter) for the first and second heating cycles, these peaks being given below in Table I.

TABLE I

  Peak endothermi- Beginning of the exothermic CBD as CBD Cooling cycle

Heating cycle

  FIG. 1, 410, 366 355 Example 2 421 419 381 381 The peak recorded in this case is of a broad and diffuse nature and does not represent the appearance of a sharp, accentuated peak.

Example 3

  A reaction vessel is charged with 204 g (1.095 mole) of 4,4'-dihydroxybiphenyl, 301.1 g (2.18 mole) of p-hydroxybenzoic acid, 181.1 g (1.09 mole).

  terephthalic acid and 526.6 g (5.158 moles) of anhy-

  acetic acid, it is maintained under a

  nitrogen and heated with stirring until

  at reflux, reflux heating which is continued

  for a minimum period of 3 hours. We then start a distillation without return and we continue for

  about 5.5 hours while raising the temperature of the

  reaction mixture up to 315 ° C. At this time, 0.76 g of distearyl pentaerythritol diphosphite is added and after 10 minutes the thick melt is poured (93.3% conversion relative to the distillate production). )

  in a stainless steel beaker covered with a

  aluminum and maintained at 300 C.

  polymer under a nitrogen protective atmosphere at 300 ° C. for 20 hours, then it is separated, allowed to cool and ground (size <1.2 mm, 80% <0.5 mm).

  prepolymer yield after milling is 90%.

  The prepolymer is advanced by oscillations under a nitrogen atmosphere in an aluminum drum, which is rotated in an oven. We heat the

  prepolymer from 204 to 354 C and maintained at the temperature

  higher temperature for 1 hour. After cooling

  The resultant polymer is obtained in the form

a dripping powder.

Example 4

  The procedure of Example 1 is exactly repeated, using the same materials and processes, to the only

  exception that 0.067 g of potassium sulphate is added

  sium to the reaction vessel with the monomer charge.

  The endothermic CBD (differential scanning calorimeter) peaks of the first and second heating cycles are determined and reported below in Table II, as is the percentage retention of

the height of the endothermic peaks.

TABLE II

  Height of endothermic PicS endothermic peaks Endothermic CBD Heating cycle% retention 1st 2nd Example 3 34 422 417t Example 4 107 416 429 The peak recorded in this case is broad and diffuse in nature and does not represent the appearance of a net peak, accentuated. Similar comparisons are made for

  several other polyesters, the control being prepared

  the process of Example 1 and the polyester

  potassium sulphate being prepared according to the method of Example 2. The results are given in

Table III below.

TABLE III

* K2S04 add- Peak Height Peaks endothermi-

  endothermic ppm CBD% retention Heating cycle 1 2nd Example 5 Example 6 110 414 422 Example 7 0 40 418 417 * Example 8 110 75 422 426 The peak recorded in this case is of a broad nature and

  diffuse and does not represent the appearance of a sharp peak, accentuated.

  As can be seen, the salt-containing polyester shows a percent retention of height of

  substantially improved endothermic peak.

  Comparisons are made in Table IV between controls prepared according to Example 1 and polyesters containing a salt prepared according to Example 2. The same control is used in Examples 12, 16, 20 and 22 but it is indicated separately so as to obtain a more immediate comparison with

  the polyesters of Examples 9, 11, 15, 19 and 21.

255559'92

TABLE IV

Cation,% of

Ppm retention salt

  Ex. 9 Aluminum acetate 98 50 Ex. 10 Control 0 22 Ex. 11 Calcium acetate 152 35 Ex. 12 Control 0 22 Ex. 13 Acetate of copper 84 84 Ex. 14 Control O 32 Ex. 15 Magnesium acetate 126 86 Ex. 16 Indicator 0 22 Ex. 17 Potassium chloride 100 70 Ex. 18 Indicator 0 18 Ex. 19 Sodium acetate 73 38 Ex. 20 Indicator 0 22 Ex. 21 Sodium sulphate 73 38 Ex. 22 Indicator O 22

  Significant improvements are achieved if

  percent of retention compared to controls with broad or diffuse second cyclic peaks when the following salts are used in place of the salts specifically mentioned in the table.

  IV, namely: calcium sulphate, magnesium terephthalate

  sium, potassium acetate, potassium phosphate and

potassium bisulfate.

Example 23

  We load a reaction container with 156kg

  of 4,4'-dihydroxybiphenyl, 233kg of p-hydroxy-acid

  benzene, 140kg of terephthalic acid, 406.5kg of anhy-

  acetic acid and 57.0 g of potassium sulfate. It is maintained under a protective nitrogen atmosphere and

  the heating with stirring up to the temperature of

  flow, reflux heating which is continued for a minimum period of 3 hours. We start then

  distillation without return, which is continued during

  5.5 hours while raising the temperature of the reaction mixture to 315 ° C. At this time, 416.0 g of distearyl pentaerythritol diphosphite are added.

  minutes, the thick melt is poured (conver-

  93.3% relative to the production of distillate) in an insulated stainless steel tank, it is kept under a nitrogen-protective atmosphere and left

  cool. It is then separated and crushed

the 11.2 mm; 80% <0.5 mm).

  The prepolymer is advanced by oscillating

  tior under a nitrogen atmosphere in a rotary kiln.

  The prepolymer is heated to room temperature

  up to 365 C and cooled immediately. We ob-

  holds the resulting polymer in the form of a trickle powder. The polymer is characterized by first and second endothermic peaks of 416 and 418 C and first and second exothermic peaks

377 and 379 C.

Example 24

  A series of 65 tests are carried out during

  which polyesters are prepared according to the method of

  Example 33, using 93 parts per million of sulphate

  potassium fate relative to the final polymer. The

  their average start of exotherm during the first cycle

  is determined to be 377.8 C and the average value

  The exotherm of the second cycle is determined to be 378, 4 C. The proximity of these values is

  extremely significant in the area of

  accuracy and reproducibility of injection molding operations. Products obtained by

  injection molding of polyesters are of high quality

ity.

  In the Tables given above, the quantity

  used salt is given in parts per million

in the finished polymer.

  In the above examples and in the claims

  cations below, the term "progression" refers to

  a polymerization in the solid state.

Claims (10)

  1. Process for the preparation of an aromatic polyester   by pre-polymerizing the precursors to form a prepolymer and then advancing the prepolymer to form a polymer of the required degree of polymerization, which method is characterized by incorporating a salt into the process   before completion of the polymerization.   2. Process according to claim 1, characterized   in that the polyester contains repeated fragments   selected from the group consisting of one or more of the following formulas: 0 C p q. II n -O Co S   In which x represents 0, S, -C, NH or SO 2, n is 0 or 1, and the total of the integers p + q + r + s + t + u in the fragments. present is from about 3 to about 800.   3. Process according to claim 2, characterized   in that salt is added at a rate of 25 to 500 parts per million.   4. Process according to claim 2, characterized   in that the salt is an organic salt.   5. Process according to claim 2, characterized   in that the salt is an inorganic salt.   6. Process according to claim 2, characterized   in that the salt is an alkali metal salt.   7. Process according to claim 2, characterized   in that the salt is an alkaline earth metal salt   generous. 8. Process according to claim 3, characterized   in that the salt is potassium sulphate.   9. A process according to claim 3, characterized   risé in that the addition of salt is done with the load of monomers.   10. Process according to claim 1, characterized   in that the salt is a member of the group consisting of aluminum acetate, calcium acetate, calcium sulfate, copper acetate, magnesium acetate, magnesium terephthalate, acetate of potassium, the   potassium chloride, potassium phosphate, acetic acid,   sodium tate, sodium sulfate and potassium bisulfate.