DE1271986B - Process for the production of molded articles - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

German class:

Number:
File number:
Registration date:
Display day:

C 08g

39c-10

39 b-22/04

P 12 71 986.7-44 (B 72231)

June 10, 1963

4th July 1968

It is already known to produce moldings by polymerizing caprolactam, this being the case contains glass fibers as filler and wherein an acyl compound in addition to the alkaline activator Catalyst is used.

The invention relates to a process for the production of moldings by polymerizing a mixture of glass fibers and caprolactam, the an alkali catalyst and optionally a Contains activator, in a heated form, which is characterized in that mixtures are polymerized, which contain glass fibers with a maximum length of 1.5 mm and at least 88% of this Glass fibers have a length of no more than 0.5 mm.

According to the process of the invention, caprolactam, which is an alkali catalyst such as sodium and optionally also contains an activator such as N-acetylcaprolactam, in a heated form poured so that the polymerization of the caprolactam is initiated in the mold.

It is extraordinary for certain applications where the highest precision is required it is desirable that the polyamides produced by casting are as dimensionally stable as possible. Until now there was a tendency for such objects to expand beyond the permissible limits, if they have been exposed to heat and / or moisture. These disadvantages of the known method are remedied by the method according to the invention, in which an improvement in dimensional stability is achieved by cast bodies.

In the method according to the invention, glass fibers with a maximum length of 1.5 mm are used, at least 88% of these glass fibers having a length of no more than 0.5 mm. The diameter of the fibers does not seem to be critical and can be used in the usual way 2 to 30 microns.

The amount of glass fibers used according to the invention can vary within wide limits; one has z. B. improved dimensional stability achieved with the addition of 10 to 60 percent by weight of glass fibers, calculated on the weight of the caprolactam.

The glass fiber to be used according to the invention can be produced by grinding the commercially available staple glass fibers in a ball mill for a suitable time, e.g. B. from 4 to 6 hours will. The grinding is preferably carried out in the presence of water, so that the product obtained in the form of an aqueous slurry. Before being incorporated into the caprolactam, the water

Process for the production of moldings

Applicant:

British Celanese Limited, London

Representative:

Dr. O. Dittmann, patent attorney,

8000 Munich 9, Bereiteranger 15

Named as inventor:

John Downing, Spondon, Derby;

Robert John Tracey,

Sunnyhill, Derby (Great Britain)

Claimed priority:

Great Britain June 13, 1962 (22 657)

removed, e.g. B. by removing the main amount by decanting or filtering and then that

The fibrous filler dries.

The glass fiber used as a filler should be added to the caprolactam shortly before the start of the casting process be added, the addition preferably taking place before an activator such as N-acetylcaprolactam is added to the caprolactam.

It is an advantage of the method of the invention that the glass fibers do not become entangled in the slurry noticeably settle out during the polymerization of the caprolactam so that the fibers are essentially lent are evenly distributed in the cast body. It is desirable that the formulation of the caprolactam casting mix is selected so that the shortest possible polymerization induction period z. B. results up to a minute.

Serving as a filler glass fiber can be pretreated with known substances to the To improve the adhesion of glass to the polyamide. For this purpose z. B. polyacrylic resins be used.

When using activated casting mixes, N-acetylcaprolactam is the preferred activator, however, other substances can also be used, e.g. B. those described in British patent specification 872,328 have been described. In addition to sodium, other alkaline catalysts can also be used as alkali catalysts Substances such as potassium or alkali hydroxides can be used.

809 568/571

The invention is illustrated by the following example, the quantitative data in parts by weight and weight percent are given.

Example "

Chemically cleaned staple glass fibers with an average length of about 3 inches were made ground under water in a ball mill for 5 hours, leaving an aqueous slurry of fibers obtained in which 88% of the fibers were less than 0.5 mm in length. You left the porridge Stand for 1 hour and then decant the water. The residue was then dried.

A mixture was prepared by dissolving 0.25 parts of sodium in caprolactam, the the glass fibers were added so that 54 parts of glass fibers were dispersed in 100 parts of caprolactam was. Then 1.75 parts of N-acetylcaprolactam were added stirred in, and the mixture was poured into a mold, heated to 160 ° C. and allowed to harden.

An essentially homogeneous cast body was obtained which had a coefficient of expansion of 50 x 10-6 per Vio ° C.

Claims (2)

Patent claims: 1. Process for the production of moldings by polymerizing a mixture of glass fibers and caprolactam, which contains an alkali catalyst and optionally an activator, in a heated form, characterized in that that one polymerizes mixtures containing glass fibers with a maximum length of 1.5 mm and at least 88% of this Glass fibers have a length of no more than 0.5 mm. 2. The method according to claim 1, characterized in that the caprolactam 10 to Adds 60 percent by weight of glass fibers. Considered publications:
German Auslegeschrift No. 1 071 947, 809 568/571 6.68 © Bundesdiuckerei Berlin