DD228290A1 - PROCESS FOR PREPARING HIGHLY VISCOSIVE POLYAMIDE - Google Patents

Abstract

The production of polyamide-6 elevated viscosity of a low viscosity polyamide is carried out in the melt by adding 0.05 to 5% of a copolymer of maleic anhydride and an alpha-olefin, wherein the copolymer is added as a solution. Such solvents, such as primary alcohols and / or water, are preferred which react with the copolymer under half ester or dicarboxylic acid formation, from which the anhydride is formed back under the conditions of the polyamide 6 melt.

Description

VEB Leuna-Werke Leuna,

"Walter Ulbricht"

LP 8407-

Title of the invention. .

Process for the preparation of highly viscous polyamide.

Field of application of the invention

The products produced according to the invention are used in the plastics processing industry for further processing into fibers, films, injection-molded parts, hollow bodies and semi-finished products.

Characteristic of the known technical solutions

High molecular weights are required for the production of polyamides, semi-finished products and hollow bodies as well as for special high quality polyamide 6 injection molded parts » _y Measured by the relative solution viscosity (according to OXJL

Ij wi! ljw ^! t

20055), this means that values above 3.6, advantageously over 4.0, must be achieved · The large-scale production of such polyamides is carried out by Hachpolymerisation of suitable low molecular weight polyamide-6 just below the melting point in vacuo or in an inert gas atmosphere (DE-AS 1115017, DE-PS 1079834, DE-AS 1179370, DD-PS 91566)

The method further described for the preparation of high molecular weight polyamide-6 by incorporation of crosslinkers, such as ^ Kohlensäureestern of phenols, epoxy compounds or diisocyanates have because of various disadvantages, such as ,, for example, z-toxicity of the raw materials and by-products of no importance acquired ·

Furthermore, it has been proposed to use polyamide-6 with an alternating copolymer of maleic anhydride and an alpha-olefin in the melt. The copolymer is applied as a fine powder to the polyamide in a mixer and then mixed in the melt via an extruder.

Despite the use of twin-screw extruders, the quality of the resulting high molecular weight polyamide-6 is not sufficient for certain applications. · This mainly includes the production of blown film. · These films have increased turbidity and tend to crack in the longitudinal direction under internal pressure. «

Object of the invention

The aim of the invention is the preparation of a highly viscous polyamide-6 by crosslinking in the melt with an alternating maleic anhydride / olefin copolymer while avoiding the abovementioned disadvantages.

- 3 Presentation of the essence of the invention

It was therefore the task of polyamide-6 of the relative solution viscosity of 2.0 to 3.5 after its preparation in the usual polymerization facilities of hydrolytic polymerization to produce a polyamide-6 with higher relative solution viscosity · According to the invention, the production of high-viscosity polyamide-6 by cross-linking of polyamide 6 of a relative solution viscosity less than 3.6 in the melt by the addition of 0.05 to 5 SS, preferably 0.3 to 1%, of an alternating copolymers of maleic acid or itaconic anhydride and an alpha-olefin of the general formula ~ n ./E-, in which R and R "aliphatic

" ² ^

see hydrocarbon radicals having one to ten carbon atoms and / or hydrogen or R _{1 is} a hydrogen atom and R _{2 is} an ester or ether group, characterized in that the copolymer is incorporated in dissolved form in the polyamide-6 melt, preferably such solvents , such as primary alcohols having one to ten carbon atoms and / or water, which dissolve the copolymers under half ester or "dicarboxylic acid formation and which can rebuild the anhydride under the conditions of the polyamide melt.

As solvents for the copolymers it is possible to use ketones, preferably acetone and methyl ethyl ketone.

The primary alcohols which dissolve the copolymers with half ester formation are preferably methanol, ethanol, n-propanol and n- and isobutanol. The regression of the anhydrides is z. B ". Methylhalbester when the copolymers of maleic anhydride and propylene already at a little over 100 ⁰ C a · In n-butanol the maximum of the elimination over 200 ° C ·

The process according to the invention is expediently carried out on a twin-screw extruder. It is also possible, however, to use appropriately equipped bale neck extruders.

The solution is fed, expediently with the aid of a pump, to the extruder at a point at which the polyamide is essentially melted. The supply can be effected under pressure or else without pressure by dropwise addition of the solution directly to the melt and immediately distilling off the solvent In the former case, the solvent must be withdrawn through a downstream degassing zone. However, in the second case, the pressureless addition, downstream vacuum degassing is also expedient.

The solutions contain 10 to 30 % copolymer; high-percent solutions are difficult to dose because of their high viscosity, low concentrations are uneconomical ·

The crosslinking takes place at temperatures of 220 to 300 ° C., preferably at 255 to 285 ^° C.

The crosslinked polyamide is generally extruded as a strand and comminuted into granules after cooling. It is also possible, however, to couple the crosslinking process directly with the semifinished product production and thus produce, for example, round rods of large diameter.

Embodiments Example 1

In a Leistritz twin-screw extruder, 12 kg / h of polyamide-6 with a relative solution viscosity of 2.67 were metered. * The following temperature setpoints were set on the cylinder starting from the intake:

230; 260; 250; 255; 26O; 260; 260; 260; 250 ° C. With the aid of a piston metering pump, solutions of alternating maleic anhydride / propylene copolymer were metered into or onto the polyamide-6 melt, so that 0.4 % copolymer was incorporated into the nylon-6. The dosing point is given in the table as a percentage of the screw length, starting at the feeder.

Entgasungsstutzen was at 85 % of the screw length · The polyamide was extruded into strands, which were cooled in a water bath and then granulated · The solvent was removed via the vacuum degassing or distilled off directly in the pressureless dosing · The strands are free of bubbles · The with the individual Solvents achieved relative solution viscosity values compared to a product in which the copolymer was powdered onto the polyamide are shown in the table.

Experiment Solution Copolymer Dosing agent sat Conc

tration pressure +

depressurized -

A vacuum eta sprayed with + rel place in without - % of worm kenlänge 33 + 3.73 33 + 3.71 33. + ' 3.94 85 3.79 33 + 3.78 3.82

1 2 Methanol nol ethanol 10 20 3 water 20 4 water 20 5 acetone 20 Comparison -

As can be seen from the table, the products hardly differ in viscosity, the existing small differences are likely due to düngenau dosing

On the other hand, in the case of the films produced from these products, there are great differences between the products of Experiments 1 to 5 and the comparative experiment. The clearest polygons were obtained when working in accordance with Experiment 4.

Embodiment 2

In a twin-screw E2-12s extruder from VEB Trusioma, Karl-Marx-Stadt, with vacuum degassing at 75 % of the screw length, 250 kg / h of polyamide-6 having a relative solution viscosity of 2.62 were metered. Starting with the intake opening, the following setpoint temperatures were set: 200; 180; 150; 150; 150; 220 ⁰ O *

At 33 % of the screw length is a nozzle · In this nozzle various solutions of alternating maleic anhydride / propylene copolymer were dropped directly on the melt · the amount of the copolymer was 0.4 % of the polyamide .; The vaporizing solvent was passed through a vapor tube into a refrigerator and recovered. The products were made into granules. The values obtained are shown in the table in comparison with a tambourinized sample.

Attempt Solvent Concentration ^ ^{ei; a} rel

,1 methanol 25 3.85 CVJ ethanol 20. 3.88 3 water 20 3.75 comparison _ .. _ - 3.78

Again, the viscosities obtained are essentially the same.

For the films made from these products, those from the product of the comparative experiment have the highest haze and worst weldability. The product of Experiments 1 and 3 gave the best physical values of the films.

Claims (1)

" _mm rt ^ _m invention claim Process for the preparation of high-viscosity polyamide-6. Cross-linking of polyamide-6 having a relative solution viscosity below 3.6 in the melt by adding 0.05 to 5 %, preferably 0.3 to 1%, of an alternating goPolymerisats from maleic or Itakonsäureanhydrid and an alpha-Olefiü the general formula = C _n ^ ', in which R 1 and R _{2 are} aliphatic hydrocarbons Substance residues having one to ten carbon atoms and / or hydrogen or RJ represents a hydrogen atom and R "represents an ester or ethene group, characterized in that the copolymer is incorporated in dissolved form into the polyamide-6 melt, preferably such solvents as primary alcohols having from one to ten carbon atoms and / or water, which dissolve the copolymers under formation of half esters or dicarboxylic acids and which rebuild the anhydride under the conditions of the polyamide melt.