CS270314B1 - Method of polypropylene stabilization - Google Patents

Abstract

Reducing yellowness and increasing the stabilizing efficiency of polypropylene and its copolymers containing up to 10% by weight of ethylene stabilized with 0.02 to 1% by weight of 2,6-dimethyl-4-olgopropenylphenol and 0.02 to 1% by weight of 2,6-ditertiary-butyl-4-methyl-4-ol is achieved by adding 0.01 to 1% by weight of low molecular weight epoxy resins containing 0.1 to 10% by weight of epoxy oxygen.

Description

The invention relates to polypropylene and its copolymers with ethylene stabilized against thermal degradation by phenolic stabilizers.

AND

2,6 - dimethyl - 4 - oligopropenylphenol is the most obvious phenolic stabilizer. Its price-performance ratio is more advantageous for polypropylene than the use of spherically hindered phenols based on 3,5 - dtert.butylphenylpropynic acid (irganox lolo and Io76). The combination of 0.1% by weight of 2,6 - dimethyl - 4 - oligopropenylphenol, 0.1% by weight of 2,6 - dtert.butyl - 4 - methylphenol and 0.75% by weight of calcium stearate sufficiently stabilizes polypropylene for less demanding applications, for example for the production of oriented tapes.

The disadvantage of 2,6-dimethyl-4-ol-propenylphenol (hereinafter referred to as AO 49), which does not have tert-butyl substituents in the ortho-positions of the OH groups, is the fact that it can react more easily with residues of Ziegler-Natta polymerization catalysts than sterically well-protected phenols and therefore more easily cause discoloration of the plastic. Discoloration is a feared aesthetic defect of natural polypropylene granules, especially homopolymers, but also propylene-ethylene copolymers, which reduces their commercial value.

It has now been found that this deficiency can be eliminated by combining AO 49 with epoxy resins.

The subject of the invention is polypropylene and its copolymers with ethylene stabilized with phenolic and epoxy stabilizers, optionally containing lubricants, pigments and other processing additives, which contains o.o2 to 1% by weight of 2,6-dimethyl-4-propenylphenol, o.o2 to 1% by weight of 2,6-dtert.butyl-4-methylphenol and o.ol to 1% by weight of low molecular weight epoxy resins containing o.l to lo% by weight of epoxy oxygen.

The polypropylene of the present invention may contain up to 10% by weight of copolymerized ethylene. The low molecular weight epoxy resins used in combination with two thermosetting stabilizers are produced by condensation of styrenes with epoxychlorohydrin and are characterized by their epoxy oxygen content. Epoxy resins containing 1.1 to 10% by weight of epoxy oxygen react with metals and thereby reduce the amount of metals entering the reaction with the thermosetting stabilizers. They also reduce the likelihood of undesirable discoloration of the polymer.

Adding from 0.1 to 1% by weight of epoxy compounds to polypropylene stabilized with AO 49 and 2,6-tert.butyl-4-methylenol (hereinafter referred to as AO 4K) and containing calcium ether as a lubricant also increases the long-term thermo-oxidative stability, which is higher than the sum of the effectiveness of the individual components, so that the stabilization formula exhibits a synergistic effect.

The invention will be illustrated by the following examples, % in the examples are by weight unless otherwise stated.

Example 1

To the basic formula used for the stabilization of an isotactic homopolymer of polypropylene (0.1% AO 49, 0.1% AO 4K, 0.05% calcium stearate - based on polypropylene) with a melt flow index of 4 g/l min (230 °C, 21 N) was added 0.035% of an epoxy resin containing 8% epoxy oxygen, manufactured under the name Eplkote 82? by Shell Chemicals. The mixture was granulated in a conventional manner on a Japan Shell type plant. The results were compared with data on material processed using the basic formula alone.

i . '

CS 27o314 Bl dimension basic recipe modified epoxy recipe.

23o °C, 21 N Melt Flow Index g/l min 3.3 3.3 density g cm o,9o9 o,9o9 yellowness see*kně (but standards) D B % yellowness 9 to 12 7.5 induction temperature 0°C 194 194 pressure test MPa 35.1 35 MPa ‘ 17.7 16.5 * 7.6 6.7 % ’ 17o 19o Notch toughness Charpy, 4 23 °C, 2.9 3.3

induction period of thermooxidation at 13o °C, ip 13o

The induction period was measured in open tubes heated to 100°C.

of the block (average of 6 samples). Its value is expressed by the number of days of exposure required for the sample to become brittle and surface cracks to appear.

Example 2 K

To the basic recipe (0.1% AO 49, 0.1% AO 4K, 0.75% calcium stearate) for the stabilization of isotactic polypropylene homopolymer and melt flow index 4 g/10 min (23o °C, 21N) was added 0.1% epoxy resin containing 0.5% epoxy oxygen, produced by the Chemical and Metallurgical Production Association in Ústí nad Labem under the name Epoxy 15. The mixture was granulated on a Brabender laboratory extruder at 24o °C. The material was compared with a standard without epoxy. Mechanical properties were unchanged, % yellowness decreased by 5%. The addition of epoxy increased the effectiveness of phenolic stabilizers.

Substance lp ¹³ ° (day)

o.l % AO 49 + o.o75 calcium stearate4 o.l % AO 4K 4 o.o75 calcium stearate3 o.l % Epoxy 15 4- o.o75 calcium stearate 1 example 2 '12

Example 3

To a propylene-ethylene copolymer containing 2.6% polyethylene, melt index 3 g/10 min (23o °C, 21N) was added 0.1% AO 49, 0.1% AO 4K, 0.75% calcium stearate

CS 27o314 131 and o.o5% Epoxy 15.

After granulation (see example 2), the percentage of yellowness decreased by 4% compared to the same experiment without Epoxy, the aynergle showed a similar effect as in the case of example 2 (lp 130 - 11 dm*).

' P ň Ε O M 6 T OF THE INVENTION

Claims (1)

Polypropylene and its copolymers and ethylene stabilized (enol and epoxy softeners, containing optional lubricants, pigments and other processing additives, marked lim, 1« contains u.o2 to 1% by weight of 2,6-dimethyl-4-olgopropenylphenol, o.o2 to 1% by weight of 2,6-dltert,butyl-4-methyl-phenol and o.ol to 1% by weight of low molecular weight epoxy resins containing o.l to lo% by weight of epoxy oxygen.