DE2407155A1 - MANUFACTURE OF POLYESTERS - Google Patents

Description

Manufacture of polyesters

The invention relates to an improved direct esterification process for the production of high molecular weight, linear polyesters from terephthalic acid and 1,4-butanediol with almost complete Suppression of the side reactions which lead to a loss of the diol reaction component.

High molecular weight, linear polyester resins of the poly (!, ^ - butylene terephthalate) family are known as unsurpassed outstanding ingredients in thermoplastic molding compounds because of their excellent physical properties and surface appearance after molding. Compared to the lower homologues Polyesters such as poly (ethylene terephthalate) and poly (1,3 ~ propylene terephthalate), the poly (1,4-butylene terephthalate) resins crystallize out of the melt very quickly. and they can therefore be formulated into compositions or masses which in customary devices or compositions are formulated in customary devices with customary temperatures and processing times can be shaped without the need to use nucleating agents.

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2A07155

Process for the preparation of poly (alkylene terephthalates) by direct esterification of terephthalic acid (TPA) with the corresponding alkylene glycols are well known.

The known methods use high temperatures and superatmospheric pressures, around the solution and the reaction of the difficult to handle Speed up TPA.

When these known conditions are used for the production of poly (1,4-butylene terephthalate) (PBT) resins, excess amounts of 1,4-butanediol are required because of dehydration of some of the butanediol to form tetrahydrofuran . This side reaction makes the known direct esterification processes economically unattractive for the production of PBT. For example, in a recently published process (Dutch Patent 7,105,777 (1971)) the butanediol is used in an amount of more than 376 % of the theoretically required amount.

It has now been found that this side reaction is the cause for the use of such excess amounts of 1,4-butanediol, it can be almost completely suppressed, though Reaction conditions are selected which accelerate the rapid removal of the by-product water (formed by the esterification reaction) from the reaction zone and in which the Time is minimized in which the 1,4-butanediol is in contact with unreacted TPA is.

The following essential parameters must be observed:

A. To speed up the removal of the water formed:

1. A reaction temperature in the range of about 175 to about 275 ° C.

2. Atmospheric or sub-atmospheric pressure immediately after the start of the reaction.

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3. Presence of a high-boiling solvent, e.g. tetralin, decalin, etc., or preferably excess 1,4-butanediol, to entrain and drive water away.

4. Gradual addition of the TPA to the hot 1,4-butanediol, whereby the rapid removal of the water formed is facilitated.

B. To reduce the contact between 1,4-butanediol and TPA:

1. Use of an effective catalyst such as an antimony compound and the like, but preferably a titanium compound or a tin compound in order to shorten the reaction time.

2. Gradual addition of the TPA and a high reaction temperature, as mentioned under A.

The poly (1,4-butylene terephthalate) resins can be made by the present improved processes can be obtained in a very economical manner. In addition, the products can do the same are easily mixed together, and they ultimately result in molded articles having essentially the same superior properties Properties like those made from the best known polyesters have been manufactured.

According to the present invention there is a method for manufacturing of high molecular weight, linear poly (1,4-butylene terephthalate) created, which includes:

(a) heating 1,4-butanediol to a temperature in the range from about 175 to about 275 C;

(b) gradual addition of the terephthalic acid to the hot 1,4-butanediol; and

(c) Removal of the by-product water from the reaction mixture as the water is formed.

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-H-

Geraäss another embodiment is a method for Production of a high molecular weight, linear poly (1,4-butylene terephthalate) created, which includes:

(a) heating a mixture of terephthalic acid and at least 1.25 moles of 1,4-butanediol per mole of acid at a temperature im Range from about 175 to about 275 ° C 'at atmospheric or Uhteratmosphärendruek;

Cb) Distillation of the excess l ^ -butanediol from the Reaction mixture and

(c) Removal of the by-product water by entrainment with the excess removed from the mixture by distillation 1,4-butanediol.

A preferred feature of the present invention comprises carrying out the reaction at atmospheric pressure or subatmospheric pressure, which can be achieved here, for example, by suction pumps or other pumps. According to a preferred one The feature of the present invention is 1,4-butanediol a molar ratio of at least 1.25, preferably 2: 1, based on the acid. Larger surpluses can also can be used, although no substantial benefit is obtained if the ratio exceeds about 100: 1.

Another preferred feature of the present invention is in carrying out the process with a high boiling liquid medium such as decalin, tetralin or the like, wherein however, it is preferred to use excess 1,4-butanediol, to help drive off the by-product water.

Other preferred features include the use of polyesterification catalysts in the reaction mixture to reduce the contact time between unreacted 1,4-butanediol and terephthalic acid abbreviate. Any conventional catalyst, for example an inorganic or organic titanium, tin or Antimony compound, can be used in usual amounts. For example, 0.001 to 1.0 mol of tetrabutyl titanate,

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Tetraoctyl titanate or triethanolamine titanate, antimony oxide, dibutyltin maleate, dilaurate and the like can be added. Preferably the polyesterification catalyst is an organotitanium or an organotitanium Organotin compound.

The high molecular weight, linear poly (1, ^ - butylene terephthalate) resins, made by the improved process of the present invention can be small amounts, e.g., up to about 15 mol- #, of groups that are derived from other glycols, such as ethylene glycol, 1,3-propanediol, 1,4-dimethylolcyclohexane and the like, and other diacids such as isophthalic acid, succinic acid, naphthalenedicarboxylic acid and the like.

The molecular weight in the final product is sufficiently high to have an intrinsic viscosity of about 0.7 to about 2.0 dl / g when measured, for example, as a solution in a 60:40 mixture of phenol and tetrachloroethane 30 ⁰ C to yield.

These high molecular weights can only be achieved after about 4 hours under the conditions according to the invention.

As for the process steps and reagents, according to one procedure, three moles of commercially available lj ^ -Butanediol in a reactor of suitable size, which with a short fractionation column is provided, for example by means of an external oil bath at 250 ° C.

The 1,4-butanediol is stirred and flushed with a stream of nitrogen, until it boils vigorously and then 1 mole becomes commercially available Terephthalic acid added gradually, i.e. over half an hour. Preferably about 0.1 mole is tetrabutyl titanate present in the hot reaction mixture. After the addition of acid is complete, the temperature is increased, e.g. to about 260 ° C, and the pressure is gradually reduced, e.g. to about 0.5 mmHg during e.g.

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2 to 3 hours. The distillates are collected and contain 1,4-butanediol and water. The resinous product is made from the Reaction vessel removed using conventional methods.

According to another procedure, the terephthalic acid is with about 5 mole /? 1,4-butanediol per mole of terephthalic acid in one Reaction vessel of suitable size given. To do this, preferably 0.1 mol # tetrabutyl titanate or a similar catalyst (based on the acid) was added. The reaction mixture is heated j for example to 185 to 205 C until it is clear becomes, which is the case, for example, after 1.5 to 3 hours. Then a weak vacuum, for example of 7 00 mm (28 ") Hg, sufficient time applied to remove the excess 1,4-butanediol and entrained water, which is usually done in about 0.5 to 1.5 hours. Finally, the prepolymer is placed under a high vacuum, e.g. 0.1 to 1.0 mmHg, heated to, for example, 225 to 255 ° C., until the desired degree of polymerization after, for example, about 1 hour has been achieved. The resinous product is then removed from the reaction vessel using conventional methods.

The following examples explain the preparation of the polyester resins according to the new process according to the invention. For comparison purposes, several procedures are listed to show the improvements, which are obtained by the procedure described to demonstrate. The examples are intended to enhance the invention do not restrict in any way.

Example 1 .

135 g (1.50 mol) of 1,4-butanediol and 0.15 g (0.44 × 10 ^-3 mol) of tetrabutyl titanate were placed in a 300 ml reaction vessel equipped with a short fractionating column and in an oil bath immersed at 250 C. The mixture was stirred mechanically and a nitrogen flow of 25 ecm per minute was directed. Then during half an hour

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83.3 g (0.50 mol) of terephthalic acid gradually to the hot Given reaction mixture. After the mixture became clear, the temperature was increased to 257 ° C. and the pressure was increased was gradually reduced to 0.5 mmHg over the next two hours and 20 minutes. The distillates were collected and analyzed and 0.821 moles of 1,4-butanediol were obtained. In order to the amount of 1,4-butanediol used is calculated as follows:

= 1.358 moles of diol per mole of TPA. This corresponded to one

excess of 35.8 % over the theoretically calculated amount. The polymer obtained had an intrinsic viscosity of 1.74 dl / g (b.
chloroethane) »

!, 7 ¹ * dl / g (at 30 ° C in a mixture of 60:40 phenol-tetra-

Comparison procedure A

As in Example 1, there were 135 g of 1,4-butanediol and 83.3 g of terephthalic acid and 0.15 g of tetrabutyl titanate reacted. However, the terephthalic acid was already present at the beginning of the reaction and was not gradually admitted. The distillates contained 0.687 mol of 1,4-butanediol, so that the amount of diol used is:

^{= 1} » ⁶ 3 moles of diol per mole of TPA calculated.

This corresponded to a 63% excess over the theoretically required Lot. The polymer obtained was gray-white and had an intrinsic viscosity of 1.50 dl / g.

Example 2

15 kg (33.2 lbs) (0.2 lb.mol) terephthalic acid, 38.5 kg (85 lbs) (0.944 lb.mol) 1,4-butanediol and 28 g (0.18l χ ΙΟ " ³ lb. mol) of tetrabutyl titanate were placed in a 90 1 stainless steel reactor. The mixture was heated for 2 hours and 20 minutes at I85 to 202 ⁰ C until it became clear and was then 2/3 h. under a weak vacuum ( 700 mmHg) the excess diol and the entrained water are removed.

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polymer was placed in a polymerization reactor and for one hour under a pressure of 0.38 mmHg and a temperature Treated from 225 to 255 ° C. The distillates were analyzed and a total of 0.725 Ib.mol butanediol was found.

The diol consumption in this reaction was calculated as follows:

- 1 * 095 moles diol / mole TPA or only 9.5 % above

the theoretically required amount. The polymer obtained had an intrinsic viscosity of 1.13 dl / g.

Settlement procedure B

After recently in the Dutch. U.S. Patent 7,105,777 (1971) which is based on U.S. Patent Application Ser.No. 32 75 ¹ J (1970) based published method were 125 g (0.75 mol) terephthalic acid, 375 g (4.167 mol) 1,4-butanediol and 0.225 g (0.66 10 ^-3 mol) tetrabutyl titanate in an autoclave stainless steel for 3 hours at a pressure of 3.5 ~ 4.9 kg / cm (50-70 psig) and a temperature of 235 ° C. The prepolymer was then further polymerized in a glass reaction vessel for 2 1/2 hours at 250 ° C. and an ultimate vacuum of 0.3 mmHg. The collected distillates were analyzed and they contained a total of 0.596 moles of 1,4-butanediol. With this method, the butanediol consumption was calculated as follows:

= 4.76 moles of diol per mole of TPA or 376 % above the theoretically required amount. The polymer was recovered and had an intrinsic viscosity of 1.02 dL / g.

Example 3

In a tubular reaction vessel of 100 ecm, which with a spiral stirrer and a side arm for the removal of the volatile products was 16.6 g Terephthalic acid (0.10 mol), 13.5 g 1,4-butanediol (0.15 mol)

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-5 and 0.02 g of triethanolamine titanate (3.5 x 10 moles) were added. After this Flushing with nitrogen, the tube was immersed in an oil bath heated to 2 ^ 0 C for 105 minutes until the reaction mixture was clear became. The temperature was then increased to 255 ° C and the Pressure gradually decreased to 0.15 mmHg over the next 2 hours. The product obtained had an intrinsic viscosity of 1.05 dl / g. Analysis of the distillates indicated that a total of 0.019 moles of the butanediol had been recovered; consequently the butanediol consumption was:

= 1.31 mol of diol per mol of TPA, which corresponded to an excess of 31 % over the theoretically required amount.

In this example the excess of butanediol originally used was only 50 % \ the use of an effective catalyst and the effective removal of water by the excess butanediol in the absence of a fractionating column, however, made it possible to produce a product of high molecular weight and a relatively low butanediol loss.

example H

The procedure of Example 3 above was repeated with the exception that: the catalyst was comprised of 0.1 g of dibutyltin dilaurate (1.6 10 mol) existed and the entire reaction time 195 minutes. The polymer obtained had an intrinsic viscosity of 0.99 dl / g, the amount of that in the distillates butanediol found was 0.0129 mol and the actual butanediol consumption was thus calculated as:

^{= 1} » ^{371 Mo1 diol} / ^M ° i ^{TPA or} 37, i

more than the theoretically required amount.

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Example 5

The procedure of the preceding examples was repeated with the exception that the catalyst was composed of 0.1 g of dibutyltin rnaleate (3.2 10 mol) and only 11.7 g of butanediol (0.13 Mol) were added to the reactor. After a reaction time of 2 1/2 hours, a polymeric product with an intrinsic molar Obtained viscosity number of 0.73 dl / g. The diol consumption that In order to correct the 0.0036 mol amount of butanediol found in the distillates, the following was calculated:

^Mo1 butanediol per mole of TPA, what

thus a 26.4 £ excess over the theoretically required Amount corresponded.

The above examples show that high molecular weight poly (1,4-butylene terephthalate) with very greatly reduced or practically completely suppressed losses of 1,4-butanediol due to from side reactions, for example the dehydrogenation of part of the 1,4-butanediol to tetrahydrofuran, can be obtained.

Further modifications of Examples 1 to 5 yield processes which are also within the scope of the present invention.

For example, a 98/2 mixture can be used instead of terephthalic acid of terephthalic acid and isophthalic acid, a 99/1 mixture of terephthalic acid and adipic acid or instead of 1,4-butanediol a 98/2 mixture of 1,4-butanediol and glycerin is used will.

The dibutyl tin maleate can be replaced by tin (II) oxalate.

Because of their excellent physical, mechanical, chemical, The polyesters produced by the process according to the invention have electrical and thermal properties many and different uses. You can

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Used alone as a press powder or mixed with other polymers and they can be fillers, both reinforcing, such as glass thread, and non-reinforcing, such as wood flour, Fabric fibers, clays and the like, as well as flame retardants, pigments, dyes, stabilizers, plasticizers, etc. contain.

Obviously, other modifications and variations of the foregoing invention are possible within the scope of the teachings given. Modifications in individual examples of the invention described are therefore intended to be encompassed by the scope of the invention as defined by the appended claims.

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Claims (1)

Claims 1. A method for producing a high molecular weight linear poly (1,4-butylene terephthalate) resin, thereby characterized in that it includes: a) Heating 1,4-butanediol to a temperature in the range from about 175 to about 275 ° C; b) gradual addition _r of terephthalic acid to the hot 1,4-butanediol; and c) Removal of the by-product water from the reaction mixture as soon as the water is formed. _2.y Process for the preparation of a high molecular weight, linear ^ poly (1,4-butylene terephthalate), characterized in that it comprises: a) heating a mixture of terephthalic acid and at least 1.25 moles of 1,4-butanediol per mole of acid to a temperature in the range of about 175 to about 275 ° C; b) distilling off the excess 1,4-butanediol from the Reaction mixture and c) Removal of the by-product water by entrainment with the excess 1,4-butanediol distilled off from the mixture. 3. The method according to claim 1 or 2, characterized in that the reaction mixture further comprises a poly esterification catalyst. 4. The method according to claim 3, characterized in that the polyesterification catalyst is an organo-titanium or an organo-tin compound. 409835/0950 5. The method according to claim ¹ J, characterized in that the catalyst is tetrabutyl titanate. 6. The method according to claim 2, characterized that the mixture contains from about 2 to about 100 moles of 1,4-butanediol per mole of terephthalic acid. 409835/0950