CS270157B1 - A process for producing polypropylene breast fibers by controlled degradation - Google Patents

Abstract

economically and technologically advantageous process for the production of polypropylene for fibers by controlled degradation initiated by organic peroxides in the presence of a stabilization system consisting of 0.02 to 0.3 wt. % phosphite antioxidant based on penteerythritol and 0.02 to 0.3 wt. % phenolic isocyanurate-based polyol antioxidant, in which a solid and liquid initiator of degradation is added to the powdered polypropylene by melting in a mass ratio of solid and liquid components of 1:1 to 5:1 and in a total amount of 0.01 to 0.5 wt. %, as well as 0.1 to 0.5 wt. % light stabilizers. The liquid initiator is 2,5-dimethyl-2,5-ditert-butylperoxyhexone and the solid is bis/tert-butylperoxyisopropyl/benzene.

Description

The present invention relates to an improved process for producing polypropylene for fibers by controlled degradation initiated by organic peroxides in the presence of a stabilizing system comprising a phosphitic antioxidant, a phenolic isocyanurate antioxidant with a sterically unprotected phenolic group, light stabilizers and processing aids.

Polypropylene for fibers is prepared by controlled chemical degradation, for example according to CS AO-229 766. It uses one type of alkylalkyl peroxide initiator and a stabilization system based on sterically hindered and non-hindered phenols. The addition of the peroxide initiator in the liquid state is advantageous from the point of view of the accuracy of its dosing, but the disadvantage is the high production cost. The use of a solid initiator alone is technologically disadvantageous, since this is added to the mixture of other powdered additives in the production of polypropylene; which is added to the main stream of polypropylene powder through a single common inlet. The control of the degree of polymer withdrawal is imperfect, as together with the change in the concentration of the solid initiator aa changes the concentration of the solid additives added to the polymer, the result is a considerable non-uniformity of the property. The additive system according to CS AO 229 766 combined with a light stabilizer ensures sufficient thermo-oxidative and light stability of the polymer and fibers. The presence of the phenolic antioxidants themselves in the process of producing polypropylene by euepense technology of polymerization in liquid hexane with subsequent washing of catalytic residues of NaOH causes undesired coloration of the granulate by transformation products of low molecular weight, sterically hindered phenol. By evaluating the yellowness of the granulate produced in this way according to ČSN 64 30 50 a and they reach the values of Standard 0 to E, which is a disadvantage for the production of white fibers in particular.

The proposed solution according to the subject of the invention eliminates said drawback by adding polypropylene to the stabilized system containing a phosphitic antioxidant during controlled degradation; phenolic isocyanurate antioxidant and light stabilizers. A combination of solid and liquid dialkyl peroxide initiator is used to initiate degradation; each of which is added by a separate stream. Said initiation procedure by two initiators of different states guarantees on the one hand the required accuracy of dosing of the liquid component and on the other hand a better economy of the process. The weight ratio between solid and liquid initiator is 1: 1 to 5: 1. The solid initiator aa is added as a component of the mixture of powder additives, which ee is dosed in a constant amount to a given amount of powdered polypropylene entering the proceau. The liquid initiator is metered separately into the unitabilized polypropylene powder before it is mixed with the other additives, including the solid initiator. For dosing, a gear pump connected to a spray nozzle is suitable. Bis (tert-butylperoxisisopropyl) benzene is used as a solid initiator, which adds additives to the powder composition in an amount of 0.01 to 0.15% by weight. to the total amount of wicking polypropylene. 2,5-Dimethyl-2,5-tert-butyl peroxihexane is used as the liquid initiator, which is added to the polypropylene powder in an amount of 0.005 to 0.15% by weight. to the total amount of wicking polypropylene. Prior to degradation, an stabilization system is added to the polypropylene powder, which contains a phosphite antloxident with a pentaeritritol bleaching effect in an amount of 0.025 to 0.3% by weight. to the total amount of polypropylene, for example bis / 2,4-di-tert-butylsilyl / pentaeryltrltolphosphite or distearyl pentaeryltritolylphosphite, a high molecular weight isocyanurate-type phenolic antioxidant in an amount of 0.025 to 0.3% to the total amount of polypropylene, for example 1,3,5-trls / 3, 5-di-tert-butyl-4-hydroxybenzyl / isocyanurate (trade name Goodrite 3114). The polymer further contains benzophenone, benztrlazole or HALS type light stabilizers in an amount of 0.1 to 0.5% by weight. and process such ingredients. The phosphite antioxidant guarantees sufficient protection of the material against uncontrollable degradation and the epolith with phenolic isocyanurate antioxidant sufficient processing stability. In addition to the antioxidant and thermostabilizing effect, a selective effect is also manifested. The isocyanurate-type phenolic antioxidant does not interact with peroxide molecules in the degradation process and retains its full activity to stabilize the polymer during stripping. The chemical structure of antioxidants is ak2 CS 270 157 Bl tnana even when stabilized! against the effect of light. The combination of both types of antioxidants guarantees sufficient protection of the polymer in the event of degradation, ensures the level of processing stability during spinning and, in conjunction with light stabilizers, also the light stability of polypropylene fibers. When stabilized! the said system of antioxidants does not produce colored rye products and the resulting polypropylene reaches a yellowness value of the level of Standards A to B / CSN 64-30-50 /. The examples given further illustrate the advantage! the process according to the invention as opposed to the process according to AO 229 766; expressed during the process; properties! polymer and fibers.

Example 1 ¹ .

A stream of polypropylene powder having a flow index value of 2.0 g / 10 min; The liquid peroxide initiator 2,5-dimethyl-2,5-ditert-butylperoxihexane is metered in with a gear pump in an amount of 0.0125% by weight. In a screw mixer, a concentrated composition containing powdered additives and powdered polypropylene is prepared so that the concentration of the individual additives reaches the following values for the total amount of polypropylene: • bis / 2,4-tert-butylphenyl / pentaerythritol diphosphite ........... .. 0.05 wt.

- Goodrite 3114 * which is 1,3,5-tris / 3,6 »ditert-butyl-4-hydroxybenzyl / isocyanurate. ··. *. ·« .. ···· .... ··. ** .. ····· * ········ ... ·····. ····. ·. ·········. ··· 0 * 075% wt.

a light stabilizer from the group of sterically pressed amines based on polymeric piperidine, commercial chimassorb 944 0.13% by weight.

- calcium stearate 0,1% w / w

- solid degradation initiator of bis / terebutyl peroxiisopropyl / benzene ........... 0; 125% wt.

The concentrated composition is mixed in a screw feeder with polypropylene powder to which a liquid initiator has been added. After mixing, the mixture is intensively kneaded at a temperature of 200 ° C in a continuous kneader and extruded through a zitch to the granulation head. In front of the granulation head, a filter aid is placed, on which ea anima loss of pressure. The pressure in front of the sieve is evaluated as a coefficient of variation; which indicates the uniformity of the degradation process. The result of the process is a polypropylene granulate with a flow index value of 9.8 g / l. min., whose eu properties are given in the attached epol table and the coefficient of variation of pressure.

Example 2.

Granular polypropylene was prepared according to the procedure described in Example 1; after use of the individual substances in the following concentrations:

- liquid initiator 2, 5 dimethyl-2,5 ditert-butylperoxihexene ............... 0.025% wt.

- solid initiator bis / tert-butylperoxiisopropyl / benzene ..................... 0.050 wt.

- bis (2,4-ditert-butylphenyl) pentaerythritol diphosphite ......................... 0.05% by weight.

- Goodrite 3114 ........ ....................................... ........ o, 12% wt.

- light stabilizer Chimassorb 944 .................................... 0.15% wt.

- calcium stearate ............................................... ......... 0.1% wt.

The result is a polypropylene granulate with a flow index value of 34.8 g / 10 min., The properties of which together with the coefficient of variation of the pressure in front of the filter screen eu are given in the attached table.

Example 3

By the procedure described in Example 1, granular polypropylene was prepared from polypropylene powder with a flow index value of 0.48 g / 10 min, using the individual substances in the following concentrations:

- liquid initiator 2,5-dimethyl-2,5-ditert-butyl peroxihexene .............. 0.02% wt.

- solid initiator bis / tert-butylperoxiisopropyl / benzene .................. 0,1% wt.

CS 270 157 Bl

- diatearylpentaerythritol diphosphite ............................ 0.2 wt.

- Goodrite 3114 .............. 0.25% wt.

- light stabilizer Tlnuvin 327; which is of the benztriazole type .... 0.15% wt.

- Stsarén Vápenatý ........ ·. ···. ·. ··· .... · 0.07% wt.

The result is a polypropylene granulate with a flow index value of 21.3 g / 10 min, the properties of which together with the coefficient of variation of the pressure in front of the filter screen are given in the attached table.

Example 4

Following the procedure described in Example 1e, a granular polypropylene was prepared from a polymer powder having a flow index of 1.9 g / 10 min according to AO 229 766; using the following components of the additive system:

- 2,6 ditert-butyl-4-methylphenol ... ··. ·. ·· .. ······. ··. ··. · .. · ... ·. ·. ·. ·. · 0.15% wt.

- 2,6-dimethyl-4-dodaca (propen) -yl] phenol 0.15% by weight.

- Goodrite 3114 ........................ 0.05% wt.

- distearyl thiodipropionate ......... 0,05% w / w

- calcium stearate ............................................... ...... 0.1 wt.

- light stabilizer Chimeeeorb 944 0, ’15% wt.

The liquid peroxide initiator ea is added by a gear pump in an amount of 0.072% by weight. The result is a polypropylene granulate with a flow index value of 36.2 g / 10 min, the properties of which together with the variation coefficient of pressure in front of the filter screen are given in the table.

Grenulátov polypropylene prepared according to the Examples e and polypropylene fibers available poetupu stage described in CS AO 229 766. The thus prepared fibers were determined strength in cN / dtex, and the half-period fiber strength decrease to 1/2 of their original VALUES irradiated xenon Pjy ₂ · They show the aa values obtained after 900 hours of irradiation.

Table No. 1: Coefficients of variation of polymer melt thicknesses before the filter screen during granulation; properties of polypropylene granules prepared according to Examples Nos. 1 to 4 and fibers prepared therefrom

Example no. Flow index g / 10 min. Degredebility index Index pseud · 2 / yellow Standard The strength draws cN / dtex £ 1/2 3 / VK pressure 1 9.8 1.59 1, '43 B 3.3 13 1.9 2 34.8 1.45 1, '32 AND 3; 1 23 1.3 3 21.3 1; 47 1; 37 B 3.0 29 1.5 4 36; 2 1/65 1.33 E 3; 1 15 4.7

Explanations: 1 / degradability index ID .. ratio of IT polymer degraded at 280 ° C and pDeform polymer; see ČSN 64 30 50.

2 / peeudoplaeticity index IP .. measure of the width of the molecular weight distribution, see ČSN 64 30 50

3 / Decrease of fiber strength to 1/2 flood value - expressed by% loss after 900 hours irradiation with xenon lamp

Claims (1)

OBJECT OF THE INVENTION Process for the production of polypropylene for fibers by controlled degradation initiated by organic peroxides in the presence of a stabilizing system containing a phosphitic antioxidant, a high molecular weight isocyanurate antioxidant; light stabilizers and processing additives; characterized in that into polypropylene powder with a flow index value of 0.1 to 10 g / 10 min. before melting, liquid 2,5-dimethyl-2,5-ditert-butyl peroxihexane and solid bis (tert-butylpsroxiisopropyl) benzene are added in separate streams in a weight ratio of solid to liquid component of 1: 1 to 5: 1 and in a total amount of 0.01 to 0.15% wt. by weight of polypropylene.