DE3236429A1 - Polyolefin moulding compositions which crystallise easily - Google Patents

Abstract

The invention relates to polyolefin moulding compositions which crystallise easily, comprising (1) a crystallisable polyolefin, (2) a nucleating agent and (3), if desired, other conventional assistants and additives, characterised in that the compositions contain, as nucleating agents (2), cyclic oligomers of epsilon -caprolactam. Compositions are obtained which give mouldings having improved properties.

Description

Easily crystallizing polyolefin molding compounds

The present invention relates to readily crystallizing polyolefin molding compositions from (1) a crystallizable polyolefin, (2) 0.05 to 0.8 percent by weight (based on on the polyolefin) a nucleating agent, and (3) - optionally - customary other auxiliaries or additives in the usual quantities.

Molding compounds of this type are known, including in the given context as representative, reference is made to those disclosed in U.S. Patent 3,773,741 or 3,595,735 can be.

In the easily crystallizing polyolefin molding compounds of the talk standing type, the nucleating agent has the task of the nucleation work at Crystallize to decrease, which in turn gives rise to the formation of an increased Seed density is and thus ultimately to an increased speed of the crystallization process leads. Such is desirable because it works in thermoplastic processing of the molding compositions molded parts are obtained in which the polyolefin is relatively largely is in crystalline form; - a form that is known to be opposite comparable, but less crystalline, with better mechanical and optical properties Characteristics.

In the technical-economic area, the nucleating agents made considerable demands.

In general, they should be as long as possible and with to the affected polyolefin should be as compatible as possible (e.g. not diffuse out of it). Furthermore, the nucleating agents should for their part be those which are already present and desired As far as possible, do not adversely affect the properties of the polyolefins, which is often the case the demand for physiological harmlessness belongs. After all, they should Nucleating agents be economical, i.e.

Easily accessible, easy to handle and, if possible, in small amounts Quantities effective.

The known nucleating agents are capable of one or the other Way of not meeting the demands placed on them to a desirable extent, in particular, often not because, in addition to positive properties, they have one or bring some other negative quality with it.

The object of the present invention was therefore to find nucleating agents to show the nucleating agents known there in polyolefin molding compounds are superior, especially with regard to their physiological harmlessness.

It has been found that cyclic oligomers of t-caprolactam of these Meet requirement.

Accordingly, objects of the present invention are easy crystallizing polyolefin molding compounds made from (1) a crystallizable polyolefin, (2) 0.05 to 0.8, preferably 0.08 to 0. Lot percent by weight (based on the polyolefin) a nucleating agent, as well as (3) - where appropriate - usual other help or

Additives in usual amounts.

The molding compositions according to the invention are characterized in that they contain cyclic oligomers of & -caprolactam as nucleating agents (2).

Regarding the material side of the new molding compounds, the following is detailed to say: As crystallizable polyolefins (1) those in plastics technology are suitable relevant usual. They are so well known from literature and practice that There is no need for more detailed explanations at this point. It should be noted, however, that the nucleating agents to be used according to the invention show their positive properties Particularly pronounced develop in molding compounds which, as a polyolefin, are crystallizable Contain homo- or copolymer of ethylene or propylene; - being homopolymers of propylene - i.e. polypropylene - should be emphasized, especially those the melt indexes MFI 230 / 2.16 (according to DIN 53 735 -E-) have from 0.3 to 20 g / 10 min as well as a so-called "heptane-soluble proportion of less than 10 percent by weight, i.e. of those (with a weight ratio of polypropylene: n-keptane of 5:95) less than 10 percent by weight in (under normal conditions) boiling and then n-heptane cooled back to room temperature are soluble.

According to the invention, cyclic oligomers serve as nucleating agents (2) des -Caprolactams, especially those which are at least 45% by weight from the dimer and otherwise consist of the tri-, tetra- and pentamer.

The dimer has been shown to work best; it draws with its high melting point of 3480C the end. Representative for the cyclic oligomers of ε-caprolactam there are also those with corresponding high melting points Hexamethylenediamine adipic acid oligomers into consideration.

The oligomers to be used according to the invention are known and easy accessible, e.g. from the extraction residues used in the production of poly- -caprolactam or polyhexamethylene adipamide are incurred; but the oligomers can can also be manufactured as such (cf. for example Zahn and Gleitsmann, Angew. Chemie, 75, pp. 779-80 (1963)).

The molding compositions according to the invention can - if desired - additionally to the characterizing nucleating agents (2), nor (3) other usual auxiliary or Contains additives in usual amounts, e.g. other nucleating agents, stabilizers, Lubricants, clearing agents, coloring substances, flame retardant substances as well as powder or fibrous fillers or reinforcing materials.

However, such substances are not indicative of this Invention.

The adjustment of the inventive polyolefin molding compositions from the Components can be done in a simple manner, just as you would usually add additives incorporated into the polyolefins in question - as homogeneously as possible, e.g. 3. by rolling or extrusion.

The processing of the molding compositions into molded parts can also be carried out without further ado with the devices and procedures customary for the polyolefins concerned take place.

Example starting material: A polypropylene molding compound made from (1) a Polypropylene, which has a melt index MFI 230/2, 16 of 11 g / 10 min and has a heptane-soluble content of 3 percent by weight and (2) 0.3 percent by weight - based on the polypropylene -cyclic oligomers of -Caprolactam, which lead to 55 % By weight consist of the dimer and the rest of the tri-, tetra- and pentamer.

Working device: A common device for making injection molded parts (Screw injection molding machine with 400 g maximum injection weight, 300 g Megapond clamping force and 1600 p / cm2 maximum theoretical injection pressure in front of the screw injection).

Working method: On the screw injection molding machine, rectangular, open containers (width 60 mm. length 120 mm, height 40 mm).

Working conditions: temperature of the plastic melt: 2500C cycle time: 60 sec.

Temperature of the cooling medium (water): 300C temperature during demolding so that no deformation of the molded part occurs.

This creates molded parts with a high level of crystallinity as well good other properties.

Claims (1)

Claim Easily crystallizing polyolefin molding compounds (1) a crystallizable polyolefin, (2) 0.05 to 0.8 percent by weight (based on on the polyolefin) a nucleating agent, and (3) - optionally - customary other help or Additives in customary amounts, characterized in that they contain cyclic oligomers of ## - caprolactam as nucleating agents (2).