CS243984B1 - Method of polypropylene's forming properties treatment - Google Patents

Abstract

The invention solves the adjustment of the processing properties of polypropylene for fiber production. The essence of the process of treating the processing properties of polypropylene by thermal degradation in the temperature range of 200 to 300 QC to a degree of melt index of up to 25 g / 10 min is that oxidized polypropylene or a blend of oxidized polypropylene with hydroperoxide-containing polypropylene is used for degradation from 0.5.10-3 to 5.10 "- ^ mol. kg-1 polypropylene.

Description

The present invention relates to a method for treating the processing properties of polypropylene by degradation.

The types of polypropylene produced for the production of fibers by their molecular characteristics do not meet the requirements of the processor. Depending on the product type, polypropylenes with melt index values up to 50 g / 10 minutes are required, with commercially produced types having melt index values up to 11 g / 10 minutes.

There are two possible ways to modify the molecular characteristics; during polymer synthesis by appropriately adjusting the polymerization system and reaction conditions, respectively. additional treatment in the process of processing the finished polymer using degradation activators. At the same time, this method makes it possible to significantly reduce the molecular weight distribution of the polymer being processed.

Currently, a second method is used to adjust the processing properties of polypropylene, using low molecular weight sulfur compounds, low molecular weight organic and inorganic peroxide compounds such as 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, nitrogen compounds and CC Initiators.

The disadvantages of the methods used to modify the processing properties of polypropylene by means of low-molecular-weight degradation activators are the demanding and inhomogeneous dosing of the additives ** 2 * «·

243 984 dy d · polypropylene, polluting polypropylene with a degradant, resp. its decomposition products, which can adversely color the polymer, release of irritating and toxic gases during processing, moreover, all commercially used degradants are expensive to exchange.

These drawbacks are eliminated by modifying the processing properties of the polypropylene by thermal degradation in the temperature range of 200 to 300 ° C to the degree of melt flow ondex up to 230 g / 10 minutes, which is based on oxidized polypropylene having a hydroperoxide group content of 0.5.10 ^. up to 5.10 mol.kg of polypropylene and / or a mixture of oxidized polypropylene with powdered polypropylene resulting in a concentration of hydroperoxide groups of from 0.5.10 ”to —3 11

5.0.10 mol.kg of polypropylene.

Example 1

Polypropylene having a hydroperoxide group content of 2.37 * 10 < -3 > mol / kg polypropylene was prepared by oxidizing the powdered polypropylene in ozone-encapsulated oxygen. The oxidation was carried out at room temperature in a vertical glass tube in a fluidized manner at a flow rate of 2100 mg / h of ozone. for 30 minutes. Mixtures of oxidized polypropylene with powdered polypropylene with a total concentration of hydroporoxides of 0.7 x 10 < 4 > and 1.4 x 10 < -1 > mol / kg of polypropylene were prepared by mechanically mixing the powders. The content of hydroperoxide groups in the prepared samples was determined by cold iodometric titration.

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The thus prepared oxidized polypropylene samples were processed in a laboratory single screw extruder under three thermal modes:

a) 200/240/250 ° C

b) 200/250/260 ° C

c) 200/260/270 ° C

The first number indicates the temperature in the zone below the hopper, the second in the zone after the extrusion head, and the third indicates the temperature on the screw head. The screw parameters are: D = 25 mm, L = 20 D, n = 35 rpm. The processed samples were extruded from the device in the form of a string, which was granulated and the melt flow index was measured from the granulate under standard conditions (ČSN 64 0861) on an extrusion plastomer VP-05. The results are shown in Table 1. For comparison, pre-treated non-oxidized polypropylene values having a melt index value prior to treatment of 3.42 g / 10 minutes are also shown.

TabuTka 1

concentration of polymeric hydroperoxides, mol / kg of polypropylene melt flow index, v 7 for thermal re g / 10 minutes žimv and b C Polypropylene powder 7.50 c, 86 10,05 0,7.10 ^-3 18.99 21.56 28.77 1,4.10 ^-3 41.96 53.76 66.44 2,37.10 ^-3 106.72 138.37 188.29

Example 2

Oxidized polypropylene containing hydroperoxide groups and a mixture of oxidized polypropylene with powdered polypropylene is prepared as in Example 1. Prior to treatment,

4,243,984 samples were impregnated with a solution of 2,6-di-tert-butyl-4-methylphenol in acetone such that the concentration of antioxidant in the samples was 0.2% by weight after evaporation of the solvent.

The thus prepared oxidized polypropylene samples with the addition of an antioxidant were processed under the same conditions as in Example 1. The measured melt flow index values after processing are shown in Table 2.

Table 2

concentration of polymeric lydroperoxides, mol / kg of polypropylene melt flow index, g / 10 minutes for thermal modes and b C Polypropylene powder 4.38 5.39 7.02 O, 7.1O ³ 8.49 9.91 11.92 1,4.10 ^-3 17.87 25.14 31.33 2,37.10 ^-J 53,30 72.60 94.50

Example 3

Samples of oxidized polypropylene and oxidized polypropylene with the addition of an antioxidant prepared as such in Examples 1 and 2 were thermally stressed under static conditions in the extruder plastomer chamber at 260 ° C and a residence time of 15 minutes. The powder sample was poured into the melting chamber of the plasticizing roller and sealed with a sand. The nozzle was clogged with a pulp. After 15 minutes, the samples were extruded in the form of a string, which was granulated and the melt index was measured from the granulate under standard conditions.

The test results are shown in Table 3 ·

- 5 TABLE 3

243 984

hydrope- concentration melt flow index, g / 10 minutes roxides, mol / kg of polypropylene without antioxidant antioxidant concentration 0.2% by weight. Polypropylene powder 38.15 9.06 0,7.10 ^-3 69.50 13.76 4.10 ^-3 136.64 40.87 2,37.10 ^-3 267.84 100.58

Comparative example

All of the tests described in Examples 1 to 3 were conducted under the same conditions for polypropylene containing the comparative low molecular weight peroxide 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, commercially used to modify the processing properties of the polypropylene. In all tests, the efficiency of the low-molecular-weight peroxide was 5 to 65% lower than the efficacy of polymeric hydroperoxides under the same processing conditions in view of the melt index values achieved.

Polypropylene treated in this way can be used for the needs of the plastics and fiber industries.

Claims (1)

SUBJECT VYNALEZU 243 984 The method of treating the processing properties of polypropylene by thermal degradation in a temperature range of 200 to 300 ° C djs values of the melt flow index of 250 < oxidized polypropylene having a hydroperoxide group content of from 0.5.10 to 5.0.10 mol per kg of polypropylene and / or a mixture of oxidized polypropylene with powdered polypropylene having a total hydroperexidonic group content in a mixture of -3-3 to 1 of 0.5.10 ^J to 5 is used, 0.10 ^J mol.kg of polypropylene. Printed by Moravian printing works, center. 11 100, the class of People's Militia 3, Olomouc Price: 2,40 Kčs