DE1595638A1 - Process for the production of hollow bodies from polyamides - Google Patents

Description

New complete application documents intended for the printing of the published patent application: 9 H-. / IO L>

FARBENFABRIKEN BAYER AG

ρ 15 95 638.4-44 LEVERKUSEN-B «yeiwerk October 20, 1969

Petitioner-AbteUuni Re U / Hf

Process for the production of hollow bodies from polyamides

The invention relates to a process for the production of hollow bodies from polyamides, in which the lactams in one rotating mold are polymerized.

It is known that hollow bodies (for example liquid containers) can be produced from thermoplastic compositions in such a way that these thermoplastics are in powder form introduces into a hollow form, the hollow form a rotating Movement over two mutually perpendicular planes subjects with simultaneous heating to temperatures above the softening range of the thermoplastic in question. The powder first sticks to the wall wall, melts in layers and the hollow body can be removed after it has completely melted after a certain cooling time.

In this procedure, however, it has been found that only such powders made of thermoplastics can be processed favorably that have a very broad thermoplastic range. The polyamides are just plastics that

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only a minimal thermoplastic processing area have, making the production of hollow bodies by the rotational molding process is quite difficult.

It has now been found a process for the production of hollow bodies of polyamides when introducing an anionically activated lactam, or a mixture of lactams in a rotating in two mutually perpendicular planes hollow mold and the polymerization in this mold at temperatures between 80 ° to 210 ⁰ C. performs. In this process, the lactam melt polymerizes and the moldings can be removed from the mold without a long cooling time.

It is true that satisfactory hollow bodies made of gelling or curable materials, such as suitable polyvinyl chloride pastes, have already been produced or to produce epoxy resins by the known rotation process, but the media mentioned stick due to their thick consistency on the walls and the hardening takes place without major difficulties. In contrast, the lactam melts used according to the invention are so fluid that their viscosity increases the processing temperatures used are partially less viscous than water. It is surprising and it was under no circumstances can we foresee that these low-viscosity lactam melts with the help of the rotational molding process to form hollow bodies with a smooth and flawless surface and process with a homogeneous structure.

In contrast to the well-known single-axis rotational molding, wherein the melt is pressed against the mold wall by the centrifugal force, it is not surprising as the rotomolding process, a process that is carried out at the ⁴ contend with overall rotational speeds. The melt is therefore not caused by centrifugal force

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pressed against the mold wall, but washes around or flooded the inner walls of the mold.

The method according to the invention makes it possible to produce very large hollow bodies made of polyamides in a simple and special way economical way to produce. It is true that using the usual blowing technique results in very high viscosity • Polyamide granules can produce hollow bodies up to a volume of 50 - 60 liters, but this only happened with a relatively high mechanical effort, e.g. using suitable memory heads with appropriate Printing and ejecting devices. However, even with a large technical on v / an d, it should be extraordinary It can be difficult to economically produce hollow bodies of a volume above 100 liters made of polyamides to manufacture portable «ice. In contrast, the inventive Procedure has the following advantages:

1. Since the RotationsgUi3 is pressure-free, they are not expensive and heavy "tools required, but simple .forms, which z. B. can be made from simple sheet steel.

2. The processing temperatures are generally around 100 ^° C. lower than in the known blow molding process.

3. There is no waste, whereas after the blow molding process there is a significant percentage of waste that is in the reprocessing as a result of material changes and moisture absorption would lead to considerable difficulties.

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4. Through optimal polymerization and rotation conditions hollow bodies can be produced by the process according to the invention, which even with an unfavorable shape in Corners and edges have a uniform wall thickness, whereas with the blow molding process it is known to be very difficult Forming difficult molded parts with a uniform wall thickness.

5. In contrast to the known blow molding process, in the production of hollow bodies according to the method according to the invention on cooling within the production cycle can be completely or largely waived.

Lactams which can be subjected to activated anionic polymerization can be used, for example £ -Caprolactam, Pyrrolidone, Capryllactam, Oenanthlactam, Laurolactam and mixtures of the lactams mentioned. But it can also be substituted lactams - optionally in Mixture with the named pure lactams - are used, for example, N-methylcaprolactam. Furthermore, the add commonly used additives such as glass fibers, pigments, dyes, stabilizers and fillers.

It is preferable to work with speeds of rotation of 2-50 rpm. The processing temperatures are in the range of 80 ° to 210 ⁰ O, UD ° preferably up to 200 ⁰ C.

The alkaline catalysts usually used for the ionic polymerization of lactams are used Substances under consideration (alkali metals such as sodium or potassium, alkali or alkaline earth compounds such as sodium carbonate and potassium carbonate, alcoholates, calcium carbonate or magnesium carbonate, alkali salts of lactams). Acylating compounds are used as activators, for example Isocyanates, cyanamides or carbodiimides

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(see German Patent 1,067,591). According to the method according to the invention, large-volume hollow bodies such as petrol tanks, canisters, transport and storage containers for heating oils and other liquids are manufactured.

Example 1;

2 moles of £ -CaprοIactarn = 226 g with 2 to 3 ml of a n-methanolic sodium methylate solution (catalyst) was added and briefly melted under vacuum. After releasing the vacuum with nitrogen, 2 ml of 1,6-hexamethylene diisocyanate are added to the melt and the melt is quickly poured into a 1 liter round bottom flask heated to 180 ° C., which is located in the heated rotating device. The speeds of rotation around both axes of rotation are approximately 20 rpm. At a reaction temperature of approx. 180 ^° C., the polymerization is complete in three minutes and the molded part can be removed.

Example 2:

Place a larger one in two separate containers, each with an alkaline catalyst and an activator Stock of reactive melt. Unless the two Approaches are not yet combined, they are storage-stable for a long time.

To produce a cylindrical hollow body with a capacity of approx. 50 1, 1.75 1 of the catalyst content is mixed igen oaprolactam melt with 1.75 1 of the activator-containing Melt caprolactam and fill the mixture in

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to achieve a two-part form of ordinary sheet iron, which is internally very well polished to a very smooth surface of the hollow body. The rotating device is allowed to rotate in the two levels at 5 revolutions per minute each. As the reaction temperature to choose a range of about 170-180 ⁰ C. After about 3 1/2 minutes, the polymerization is complete and the molded article can be removed. The seamless cylindrical hollow body has a wall thickness of approx. 5 mm.

Example 3:

There are 2 mol of a mixture of caprolactam-laurolactam in a ratio of 90:10 mol ', i corresponding to 203.2 g of caprolactam and 39.6 g of laurolactam with 2 ml of a 3N methanolic sodium methylate as a catalyst and according to the manner described in Example 1 in treated with a suitable apparatus. The melting temperature is 110-120 ⁰ C. After completion of the pre-treatment, 2 ml hexamethylene diisocyanate-1, is added 6 and the melt is heated rapidly in a 170 ⁰ C cylindrical 1. 1 - filled Piaschenform, which is located in the heated rotating device . The speed of rotation around the small axis is 20 rpm, around 14 rpm around the large axis. After about 4 to 5 minutes, the polymerization and crystallization are complete and the molded body can be removed. The polyamide bottle obtained is extremely impact-resistant and practically unbreakable even in the dry, unconditioned state.

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Claims (3)

Claims 1. A process for the production of hollow bodies from polyamides by ionic polymerization of lactams in the presence of an alkaline catalyst and an activator in rotational molding, characterized in that the active. vat or an acylating compound from the group of organic isocyanates, carbodiimides and cyanamides is used. 2. The method according to claim 1, characterized in that ζ- caprolactam is used as the lactam. 3. The method according to claim 1, characterized in that a mixture of £ ~ caprolactam and laurolactam is used. Neue Unterlaoen i * t 7 ■ «ι ** 2» *., Sau 3 «. a «« ™ «» ^ v. 4. a. ^ i Le A 10 091 - 7 - 009818/1797