DE2710034B2 - Process for the production of hydrolysis-stable molded structures from polyesters - Google Patents

Description

The invention relates to a process for the production of hydrolysis-stable molded structures from polyesters as well as the resulting structures.

Polyesters can be prepared by heating dicarboxylic acids or their derivatives with diols esterbildenden to temperatures up to 300 ⁰ C m in a known manner. Preferred dicarboxylic acids are terephthalic acid, optionally in a mixture with other aromatic and / or aliphatic dicarboxylic acids. As diols, aliphatic diols of the general formula r>

HO- (CH ₂ J _n -OH,

where η is an integer from 2-10, and substituted aliphatic diols, such as. B. 2,2-dimethylpropanediol-1,3, and / or cycloaliphatic diols, such as _{4 ()} M-bishydroxymethylcyclohexene, or polyethylene oxides can be used. This gives high molecular weight linear polyester or copolyester, which various additives such. B. matting agents, can be added, and their molecular chain primarily as ₄ -. End groups have COOH and OH groups.

These polyesters, which are generally in the form of granules, are usually used to shape them Melted in an extruder and fed into a spinning or injection unit ™ by means of a screw promoted, from where they pass through a nozzle plate into threads, tire cords or wires or in an injection mold or another molding tool to be processed into shaped structures.

The polyester is partly thermally and, ··, hydrolytically degraded, the extent of this degradation mainly depending on the temperature and the residence time in the extruder. These degradation reactions cause the one hand a reduction in molecular weight and hence the viscosity of the polyester and _w> on the other hand increasing the concentration of carboxyl end groups in the macromolecule.

Are moldings of polyesters or the products produced therefrom, in their practical use of a higher stress, particularly exposed to higher b ^r> temperatures or prolonged exposure to moisture, alcohols, acids or amines, thus find further degradation reactions, such as hydrolysis, alcoholysis or aminolysis, instead of , which further lower the molecular weight of the polyester and in this way reduce its strength. The extent of these degradation reactions, in particular that of hydrolysis, is primarily dependent on the concentration of carboxyl end groups. The higher the content of carboxyl end groups, the greater the degradation.

There are already processes for the production of polyesters with reduced COOH end group content known. One uses z. B. suitable compounds, which with the carboxyl end " groups of the polyester can react. The application of the previously known procedures is but associated with disadvantages, as can be seen from the following statements Glycidäthem is an aftertreatment for the schnitzel elevated temperatures required (CH-PS 5 34 710). Diepoxides interfere when used for fibers, threads and Wires even process the material by crosslinking the polyester (GB-PS 11 39 379). Carbodiimides (US-PS 3193 522 and 3 J 93 523) are unsuitable because of discoloration of the polyester ketenes and Diketenes (BE-PS 5 53 273) are more complicated because of the formation of undesired anhydride groups Handling, i.a. poorly suited because of its ability to react to humidity

It has now been found that when using N-glycidylimides cyclic dicarboxylic acids these There are no disadvantages. These connections can be handled easily and in simple form, e.g. B. by powdering the polyester granules or by adding in molten form, the polyester melt be admitted. In addition, they lead to better results than e.g. B. glycidyl ethers, such as i.a. Example 5 and Comparative Example E show.

The invention is embodied in the claims.

The polyester material to be treated can be in the form of granules or in molten form.

Polyethylene terephthalate, polybutylene terephthalate or polyethylene naphthalate are primarily used as polyesters in question, with polyethylene terephthalate and butylene terephthalate being preferred.

The term “deformation” is intended to include melt spinning in particular. Thus it concerns with the "Formed structures" z. B. wires, fibers, threads, tire cords or injection molded parts.

As N-glycidylimides there are reaction products of Imides of cyclic dicarboxylic acids (or their alkali salts, such as the potassium salt) with an epihalohydrin, especially epichlorohydrin. They are preferably imides of cyclohexane-l ^ -dicarboxylic acid, Cyclohexene-dicarboxylic acids (where the two COOH groups are adjacent), phthalic acid, naphthalene-1,2 and -2,3-dicarboxylic acid.

Mixtures of N-glycidyl imides can of course also be used. Primarily The N-glycidyl compound of phthalic acid imide comes into question, with phthalic acid in its core may be substituted, e.g. B. with alkyl groups, in particular with 1-4 carbon atoms, halogen, such as chlorine or aryl, like phenyl, but preferably has no further substituents.

The N-glycidylimides react with the free carboxyl end groups during processing a, whereby the number of carboxyl end groups is reduced. A particular advantage of the invention In the case of using chips, the process consists of no pre- or post-treatment

of the polyester material at elevated temperature and other drastic conditions, such as elevated pressure, is required, but moisture should be excluded. Of course, the active ingredient can also be applied to the chips at a higher temperature if it appears necessary for purely practical reasons. For example, in a manufacturing plant, the chips are dried at an elevated temperature, for example in a tumble dryer. In order to save time, you shouldn't wait until the schnitzel has cooled down to room temperature. In this case, you can apply easily to the active substance on the chips at about 180 ⁰ C.

The addition of the N-glycidyl imides used according to the invention to the polyester material allows the associated reduction in carboxyl end groups, the hydrolysis resistance of the off Shaped structures made of this material by extrusion, such as fibers, threads, tire cords, wires or injection molded parts, compared to polyesters without these active ingredients. In addition, is The method according to the invention is significantly simpler compared to previously known methods. Calculated on the Polyester is the amount of N-glycidylimide added preferably between 0.2 and 1.5% by weight.

But you can also use molten N-glycidylimide Continuously metering the state into the molten polyester.

The molten N-glycidylimide is advantageous here or mixtures thereof are in the polyester melt by means of a for this type of Reactions introduced conventional apparatus, for example, the active ingredient melt through a Line flow into the polyester stream and then directs the whole thing into a mixer. Suitable as a mixing device are, for example, extruders, which can advantageously be provided with a mixing zone, or static ones Mixer.

The following examples are intended to explain the essence of the invention in more detail. The specified analysis values have been determined as follows:

The relative viscosity (ij _re /) was determined using a 0.5% strength by weight solution of the polyester in a mixture of phenol and 1,1,2,2-tetrachloroethane (1: 1,% by weight) at 20 ⁰ C measured. To determine the concentration of free carboxyl groups (hereinafter abbreviated to: [COOH]), a weighed amount of polyester was dissolved in a mixture of phenol and chloroform and titrated with benzyl alcoholic potassium hydroxide solution against tetrabromophenol blue as an indicator.

The decrease in viscosity was used as a measure of the stability to hydrolytic degradation of the polyester used after 6 hours of treatment with water at 130 ° C (measured in Lini-Test device from Quarzlampen GmbH, Hanau.). The decrease in viscosity was in% "Broken bonds" (% BB) according to the equation

% 13B =

\ Pn _n Pn ₁ . J

η _η , = 1.391 and [COOH] = 24 mVal / kg is powdered with 1.0% by weight of N-glycidylphthalimide (N-GP) in a drum under a dry inert gas atmosphere. These granules were melted using an extruder and conveyed into a spinning unit , from which it was spun into a wire (monofilament) at a rate of 30 g / min through a 1-hole nozzle. The values for [COOH] and hydrolytic degradation (% BB) ίο determined on the wire produced in this way are given in Table 1.

Comparative example A.

The polyethylene terephthalate granules described in Example 1 are used spun under the same conditions as in Example 1, but without addition. The on the wires produced in this way are values for [COOHj and hydrolytic degradation (% BB) found also given in Table 1.

Example 1 according to the invention thus shows a great improvement in the hydrolytic stability and a strong reduction in the [COOHj values compared to the material without additive (comparative example A).

Table 1

Pn ,.

calculated, where PN _V and Pn _n stand for the degree of polymerisation before and after the hydrolysis degradation.

example 1

Dried micromatted, d. H. with 0.04% T1O2 added polyethylene terephthalate granules with

example Addition ICOOH] More hydrolytic
Abba j (mVal / kg) (% IiB) 1 1.0% by weight 10
N-GP 0.028 Comparison ¹
example A 34 0.102 Example 2

Dried, non-matted polyethylene terephthalate granules with T ^ w = 1.390 and [COOH] = 23 mVal / kg, is powdered as in Example 1 with 0.73% by weight of N-GP and made into a wire processed. The values for [COOH] and hydrolytic values determined on the wire produced in this way Degradation (% BB) are shown in Table 2.

Comparative example B

The polyethylene terephthalate granules described in Example 2 are used spun under the same conditions as in Example 2, but without addition. The so The wires produced show the values given in Table 2 for [COOH] and hydrolytic degradation (% BB). Here, too, there is a notable improvement in the hydrolytic stability and a decrease in the [COOH] values of Example 2 compared to the material without addition in Comparative Example B achieved.

Table 2 additive [COOII]
(mVal / kg) More hydrolytic
Dismantling
<% bB) example 0.73 wt%
N-GP 13th
34 0.051
0.102 2
Comparative
example B

Example 3

Dried non-matted polybutylene terephthalic granules with η _Γ α = U95 and [COOH] = 38 mVal / kg are powdered in the same way as in Example 1 with 1.5% by weight of N-GP. These granules are melted using an extruder and in promoted a spinning unit, from which it is spun into threads through a 30-hole nozzle with a delivery rate of 80 g / min. The values for [COOH] and hydrolytic degradation (% BB) determined on the threads are listed in Table 3

Comparative Example C

The polybutylene terephthalate granules described in Example 3 are used under sliding conditions as in Example 3, but without the addition of N-GP, spun. The values found on these threads for [COOH] and hydrolytic degradation are also given in Table 3.

Table 3

Example!

additive

[COOH)

More hydrolytic
Dismantling

(mVal / kg) (% BB)

Table 4 additive [COOH]
(mVal / kg) More hydrolytic
Dismantling
(% BB) example 1.1 wt%
N-GCl 9
34 0.026
0.102 4th
Comparison
example D

3 1.5% by weight 21 0.061

N-GP

Comparative - 47 0.110

example C Example 4

The polyethylene terephthalate described in Example 1 is used under the same conditions as in Example 1 with 1.1% by weight of N-glycidyl-i ^ -cyclohexanedicarboximide (N-GCI) powdered. This granulate is melted by means of an extruder and in a Spinning unit is promoted, from which it is fed at a rate of 50 g / min through a 1-hole nozzle a wire (monofilament) is spun. The values for [COOH] determined on the monofilament produced in this way and hydrolytic degradation (% BB) are shown in Table 4.

Comparative Example D.

The polyethylene terephthalate granules used in Example 4 is spun under the same conditions as in Example 4, but without addition. The on The values for [COOH] and hydrolytic degradation (% BB) found for the monofilament produced in this way are also given in Table 4.

Example! 5

Dried, micromatted polyethylene terephthalate granules with 0.04% TiO ₂ and j ^ = 1.391 and [COOH] = 24 mVal / kg are placed in a drum under a dry inert gas atmosphere with 1.25% by weight of N-glycidyl phthalate (N- GP) powdered. This granulate is melted by means of an extruder and conveyed into a spinning unit, from which it is spun into a wire (monofilament) at a rate of 30 g / min through a 1-hole nozzle. The values for [COOH] and hydrolytic degradation (% BB) determined on the wire produced in this way are given in Table 5.

Comparative example E.

The polyethylene terephthalate granules described in Example 5 are used spun under the same conditions as in Example 5, but without addition. The on the wires produced in this way are values for [COOH] and hydrolytic degradation (% BB) found also given in Table 5.

Example 5 according to the invention thus shows a great improvement in the hydrolytic stability and a strong reduction in the [COOH] values compared to the material without addition in comparative example E.

Table 5 example

additive

[COOH]
(mVal / kg) (% BB)

More hydrolytic
Dismantling

1.25% by weight
N-GP

Comparative example E.
(= A)

0.006
0.102

Example 6

Dried, with 0.4 wt .-% T1O2 matted polyethylene terephthalate granulate with 7? _re ./= i, 412 and [COOH] = 21 mVal / kg, is melted in an extruder equipped with a mixing zone. N-glycidylphthalimide (N-GP), which has previously been melted in a melting vessel, is continuously metered into the melt stream by means of a suitable metering pump in an amount of 0.95% by weight, based on the polyester, just before the mixing zone. The polyester melt, which is intimately mixed with the additive in the mixing zone, is then conveyed into a spinning unit and spun therefrom at a rate of 30 g / min through a 1-hole nozzle to form a monofilament. The values for [COOH] and hydrolytic degradation (% BB) determined on the monofilament produced in this way are given in Table 6.

Comparative example F

It is the polyethylene terephthalate described in Example 6 under the same conditions as in Example 6, but without addition, spun. The values for [COOH] determined on the monofilament produced in this way and hydrolytic degradation (% BB) are also shown in Table 6.

Table 6

Example Addition [COOII] Hydrolytic

Dismantling

(mVal / kg) (% BB)

6 0.95 wt% 7 0.015

N-GP

Comparative - 28 0.082

example F Example 7

15th

Table 7

Oligomeric polyethylene terephthalate, which is produced by the continuous esterification of terephthalic acid with ethylene glycol is continuously fed into a polycondensation system. By increasing

the temperature to 285 ° C and lowering the

Pressure to 0.3-0.5 Torr is a polyethylene tere- 20 example phthalate with *) "/ = 1.55 and [COOH] = 25 mVal / kg manufactured. The polymer melt is removed from the final reactor by means of a discharge extruder. In the The sealing zone of the discharge extruder is poured into the polyester melt by means of a suitable metering pump molten N-glycidylphthalimide (N-GP) in an amount of 1.3 wt .-%, based on the amount of polyethylene terephthalate, metered in continuously. The polymer melt provided with the additive is conveyed into a spinning unit from which it is spun into threads through a 200-hole nozzle at a rate of 240 g / min. The one at that The values for [COOH] and the hydrolytic degradation (% BB) obtained are shown in Table 7 specified.

Comparative example G

It is prepared as in Example 7 polyethylene terephthalate and under the same conditions as in Example 7, but without addition, spun into threads. The values for [COOH] and hydrolytic degradation (% BB) are also listed in Table 7.

additive

iCOOIII

More hydrolytic
Dismantling

(mVal / kg) (% BB)

l, 3% by weight 5

N-GP

Comparative - 30

example G

0.014
0.113

Claims (3)

Patent claims: 1. A process for the production of hydrolysis-stable molded structures made of polyesters by Heating of dicarboxylic acids or their esterbil- -; denden derivatives have been prepared with diols are, by deformation of the polyester material in the presence of compounds that reduce the carboxyl end group content reduce these polyesters, characterized in that compounds which reduce the carboxyl end group content are used an N-glycidyl imide of a cyclic dicarboxylic acid in an amount of 0.05 to 6% by weight, based on the amount of polyester used, used 2. The method according to claim 1, characterized that N-glycidylphthalimide is used as the N-glycidyl compound 3. Shaped structures, characterized in that they according to the method according to claims 1 and 2 have been made.