CS223416B1 - A method for preparing polypropylene staple fibers using their hard wastes with improved properties - Google Patents

Abstract

Method for producing polypropylene staple fibers using their hard waste, which can be from compact to stringy. The said waste is crushed in a crusher with a capacity of 600 and above 600 kg/hour and with an energy consumption of 45 and below 45 kW and the thus prepared pulp with a melt index of 5 to 65 g/10 min., preferably 6 to 15 g/10 min. is added in an amount of up to 20%, preferably up to 3% on a polymer basis and mixed either with the original granulated polypropylene, or with a concentrator, pigment, or part of the above-mentioned amounts of pulp is mixed with a polymer and another part with a pigment concentrate and the resulting mixture is spun at temperatures of 235 to 310 °C.

Description

Method of producing polypropylene staple fibers using their hard waste, which can range from compact to stringy.

The above-mentioned wastes are crushed in a crusher with a capacity of 600 and above 600 kg/hour and with an energy consumption of 45 and below 45 kW and the thus prepared pulp with a melt index of 5 to 65 g/10 min., preferably 6 to 15 g/10 min. is added in an amount of up to 20%, preferably up to 3% on a polymer basis and mixed either with the original granulated polypropylene, or with a concentrator, pigment, or part of the above-mentioned amounts of pulp is mixed with a polymer and another part with a pigment concentrate and the resulting mixture is spun at temperatures of 235 to 310 °C.

The subject of the invention is a method of preparing polypropylene staple fibers using their hard waste, which can be from compact to stringy. The presented method allows for the improvement of the processing, thermal, light and long-term stability, dispersion properties of the waste and the fibers prepared from it by adding small amounts of the mixture, or individual stabilizers. This allows for the most effective use of the above-mentioned waste.

The occurrence of hard waste during spinning results directly from the technological process used to produce polypropylene staple, as well as from the necessary control. This type of waste has not yet been used with improved properties in polypropylene fibers.

Hard waste obtained during spinning has the following disadvantages: when regenerating polymer from waste by melting method without using stabilizers, polypropylene is obtained for further processing with an unsuitably high melt index, with deteriorated processing, thermal, light and long-term stability, pigment dispersion and some physical and mechanical properties. Therefore, this low-quality polymer can hardly be used as a raw material for fiber processing.

The shortcomings of the previous methods of using polypropylene fiber waste are eliminated by the process according to the invention, which opens the possibility of using hard staple waste with improved properties into staple fibers.

This method consists of the following:

Hard, compact waste with dimensions below 50 x 50 x 10 cm, preferably below 25 x 25 x 1 cm or string-like waste is crushed in a derivator, preferably with unused knives. The crushed waste has a melting index of 5 to 65 g/10 min. The added stabilizers can be in the form of 3-30% stabilizers in the polymer premix or regranulate, in addition to the usual state. The crushed hard waste with added stabilizer is used as a raw material in this state or is further melted in a melting device at 170 to 300 °C and filtered through a filter with 200 to 1600, or with a higher number of holes per 1 cm ² . The thus prepared pulp or regranulate can be used either separately as a 100% raw material without the use of pigment for fiber preparation or in a mixture with each other, with common raw materials, with agglomerate and with finely chopped fiber waste. In the case of using unstabilized pulp or regranulate, it is possible to add a stabilizer even during its spinning. As another option, the crushed hard waste in an amount of up to 10%, preferably up to 3% on a polymer basis is mixed either in a conical mixer with the original granulated polypropylene at a mixing duration of 8 to 40 min., preferably 20 to 30 min., or with a pigment concentrate in a conical mixer at the aforementioned mixing duration, or in another suitable device, or part of the above-mentioned amount of pulp is mixed with the polymer and another part with the pigment concentrate. The content of added polypropylene as well as pigment in a given batch is reduced proportionally to the added polymer and pigment in the form of crushed hard waste.

The homogenized, preferably mono-oxygenated raw material is melted either in the base of the melting screw at temperatures of 190 to 400 °C, or in the side one — at 200 to 390 °C, or simultaneously in both screws at the above temperatures. It is spun at temperatures of 235 to 310 °C. The melt index of the polymer determined at the spinning nozzle is 14 to 68 g/10 min. The residence time of the unstretched fiber is 1 to 60 hours, preferably 1 to 3 hours. Then the fiber is stretched at a speed of 70 to 1600 m/min. and a sizing ratio of 1:2 to 1:5.5, preferably 1:3 to 1:4. The obtained fiber has a strength of 1.6 to 5.3 cN/dtex, an elongation of 50 to 300%, a unit titer of 1 to 100 dtex, and a minimum dye fastness: dry rubbing grade 4, shampooing grade 4, and water grade 4. The crystalline fractions of the unspun fiber were determined by the flotation method.

The economic advantage of the proposed process lies in the fact that in the production of polypropylene fibers, hard waste with improved properties is used separately as a polymer raw material, dyed to the final color shade or in small quantities. This saves polypropylene and expensive pigments. The stabilizer mixtures used in this invention do not color the polymer, have low volatility, Furthermore, the substances 1 to 4 used in this invention, the proportions D ^x in a mixture with either 1 to 3 proportions B ^x or with 1 proportion C ^x or with 1 proportion E ^x are much cheaper than stabilizer A. Another advantage of this process is the lower temperatures of 5 to 110 ° C in the melting screws compared to conventional production.

The present invention can be used in the production of polypropylene staple fibers using their hard as well as soft stringy, unspun and partially spun wastes, which can be unspun and unwashed or spun, washed and dried in the form of pulp, agglomerate or regranulate. The polypropylene fiber thus prepared can be classified into quality classes.

Example 1

Waste from staple fiber production was used to evaluate the efficiency. These fibers are produced by spinning polypropylene with the trademark Tatren TF 411. The produced polypropylene staple contained 1.06 ^X A, B, C, D, E — are abbreviated designations of the relevant substances listed in Tables 1 and 2.

h. p. pigments with the trade mark Cromophtal Gelb GR (0.924 h. p.), Cromophtal Rot BR (0.112 h. p.) and Nylofilschwarz BLN (0.024 vh. p.j.

Hard compact waste combined with certain amounts of stringy waste was crushed in a crusher with a crushing capacity of 600 kg/hour with an energy consumption of 45 kW. The crushed waste was homogenized in a cone mixer for 20 min. Mechanical mixing with stabilizers was carried out in a food mixer for 10 min. The crushing was melted in an extruder with a screw diameter of 90 mm and spun. The melting and spinning conditions were: melting zone temperature 200 °C, spinning temperature 240 °C, pressure before the pump 7 MPa, pressure after the pump 9 MPa, melting time 13 ± 1 min. dosage of one spinning point 300 g/min., spinning speed 435 m/min., number of holes with a round cross-section in the die 100, diameter of the cross-section of the die opening 1 mm, length of the die capillary 4 mm. Ordinary melt indices and melt indices for degradation curves were determined on a Gottfert plastometer according to the standard. The degree of dispersion and maximum agglomeration were evaluated microscopically, similar to that stated in the Catalogue of analytical and physical methods published by the Research Institute of Chemical Fibers in Svita in 1977, pp. 79 to 82. The unstretched fiber after standing for 40 hours. stretched in the ratio 1: : 3.154 and at an average roll speed of 260 to 280 m/min. The temperature of the lower ball of the straightening machine was 101 °C and the upper ball 112 °C. The effectiveness of small amounts of stabilizers alone and their combinations in the waste was monitored. The values obtained were compared with the values of the waste alone (O). It can be seen from Table 1 that when adding small amounts of the mixture and individual stabilizers, increased values of the residual strength of the straightened fiber are obtained after 120, 240 and especially after 280 hours. stand in Xenotest 450, which indicates increased light stability and improves dispersion, or maximum agglomeration of the pigment compared to sample O. At the same time, samples with a content of substances 0.2% D, 0.1% C + 0.2% D and 0.2% D + 0.1 θ/ ₀ E have a lower strength of the unirradiated fiber in Xenotest compared to sample O. When adding small amounts of a mixture of stabilizers in the combination of 0.1% O + 0.1% D, 0.2% D + 0.1% E, the residual strength of the samples after 280 hours. stand in Xenotest 450 is 2 times higher, i.e. the light fastness is significantly higher compared to sample O, which does not contain added stabilizers.

Pigment dispersion Guided fiber Unit in unguided fibers Strength in Xenotest 450 titer

Degree Maximum determined in cN/dtex calculated as residual in dtex dispersion agglomeration after time in hours in % after time in hours

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Example 2

Similar procedure as in Example 1. The only difference is that the effectiveness of the stabilizers was monitored when melting the sample in an extruder with a screw diameter of 16 mm. The melting and spinning conditions were: temperature of the melting zones and spinning head ²⁷⁰ °C, pressure behind the pump 8 MPa, dosage 10 gAmm., spinning speed 130 m/min., number of holes in the die 20, diameter of the die hole 0.3 mm, length of the die capillary 6 mm. From Table 2 it can be seen that when adding small amounts of stabilizers, the melting indices for the degradation curves decrease. Improvement of these melting indices after a long melting time of 15 min. when degrading the sample in a plastometer + + 4 min. for determining the melt index of the degraded sample in a plastometer indicates increased processing, thermal and long-term stability of the polymer raw material from hard waste. The melt index values for the degradation curves indicate that the thermal and long-term stabilizing effect of the mixture of substances 0.2% A + 0.1% B towards the waste is higher than the sum of the stabilizing effects of the individual substances Δ and B. This is the result of the synergistic effect of the two substances between themselves, with the polymer, and possibly with other components of the polymer system.

The increased thermal stability of the polymer system allows to avoid color changes. The above-mentioned small amounts of the mixture of reagents act in a wide temperature range - from ordinary temperatures at which dispersion and maximum agglomeration are determined to temperatures of determination of the melt index for degradation curves of 270 ° C and above. At the same time, an improvement in dispersion, maximum agglomeration, light (Table 1), processing, dichroic and thermal (Table 2) stability is observed in the sample containing 0.2% A in contrast to sample O. From Tables 1 and 2 it is seen that when adding small amounts of the above stabilizers, an improvement in the set of necessary properties of the polymer raw material from the waste and a new higher stabilizing effect are obtained simultaneously. To improve the light stability of the waste, either instead of the above-mentioned stabilizers or in their presence, either 0.03 to 0.3 pr.oc. 2-hydroxy-4-n-octyloxybenzophenone, or 0.03 to 0.3% 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole.

Table 2

Melting indices for the degradation curves of grit at temperatures in °C

230 250 270

39.64 40.52 74.06

0.2% tetrakis-(2,4-di-tert-butylphenyl)-4,4'-hyphenylenediphosphonite (A) ^x

33.90 36.50 67.92

0.1% 2,6-di-tert.-butyl-4-methylphenol (B) ^x

34.00 37.71 71.10

0.2% A + 0.1% B

32.13 58.23 ^x A, B are abbreviated designations of the respective substances.

Example 3

Similar procedure as in example 1. The only difference is that the produced polypropylene staple from which the waste was created contained 0.6% of the pigment with the trademark Emeraude Lutetia J1104 and 1800 kg of granulated Tatren TF 411 and 27 kg of crushed hard waste were mixed on one side in a conical mixer within 20 min. and on the other hand 15 kg of hard waste with 26.6 kg of 20% pigment concentrate into polypropylene powder, which was stabilized with 0.2% 2,6-di-tert.-butyl-4-methylphenol, with 5% stabilizer concentrate called tetrakis-(2,4-di-tert.-butylene)-4,4'-biphenylene diphosphonite into polypropylene powder and with 69.9 kg of polypropylene of the Tatren TF 411 brand into a food mixer within 10 minutes. Next, the above mixture from the conical mixer was melted at temperatures of 393 °C in a melting screw with a screw diameter of 125 mm and the mixture from the food mixer was melted at temperatures of 263 °C in a melting screw with a screw diameter of 45 mm. Fiberization was carried out at 280 °C. The melt index at the spinneret was 24.70 g/10 min. Unstretched fiber, low crystalline content 58.1% and optical birefringence 4.8 x 10“ ³ . The drawing speed was 100 m/ /min. and the drawing ratio 1 : 3.39. The temperature of the heating elements was 130 ± 3 ^C C. Fixation was at a temperature of 130 ± 5 °C. The obtained fiber indicators were the following: strength 2.00 cN/ /dtex, strength unevenness maximum 13.28%, elongation 10.3%, titer 21.81 dtex, titer deviation maximum 0.86%. The dyeing fastness was minimal: in dry rubbing 5th degree, in shampooing 5th degree, in water 5th degree. Deviations in color shade were not observed. The achieved indicators under the above conditions allow the fiber to be classified as first quality.

The above-mentioned method of the invention has application significance for optimizing properties in the preparation of processing polymer systems such as polypropylene fibers and plastic products from their hard as well as soft string-like undirected and partially directed wastes.

Claims (3)

SUBJECT 1. A method for preparing polypropylene staple fibers using their hard waste with improved properties, characterized in that to the crushed waste with a melt index of 5 to 65 g/10 min. with a yield of 6 to 25 g/10 min. individual and especially mixtures of stabilizers are added, in which one component is either 1 to 2 parts of tetrakis-(2,4-di-tert.-butylphenyl)-4,4'-biphenylenediphosphonite with the chemical structure or parts of tris-(2,4-di-tert.-butylphenyl)phosphite with the chemical structure 2. The method of claim 1, characterized in that the crushed hard waste is added in an amount of up to 10%, preferably up to 3% based on the polymer and mixed either with the original granulated polypropylene or with a pigment concentrate, or part ¹ is mixed with the polymer and another part with the pigment concentrate with the addition of a mixture of stabilizers. 2,6-di-tert-butyl-4-alkylphenol with the chemical structure //^ where R is az ^~ ^c ^ ₀ ^q· t-bu or 1 part of the calcium salt of the monoethyl ester of (3,5-di-tert-butyl-4-hydroxybenzyl) phosphonic acid with the chemical structure or 1 part of the pentaerythritol ester of β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid with the chemical structure £-bu f- ? Θ t-bu u HO-á y-CH^CH^C00-CH _z ~ -C -CH _ž -P-0 - 1 tube 4 in trbU 0C _t H _s all the above-mentioned stabilizer mixtures are added in an amount of 0.04 to 0.5%, preferably 0.1 to 0.4% and the mixed, crushed waste, with the stabilizer is used in this state or is further melted in a melting device at 170 to 300 °C, preferably 170 to 230 °C, filtered through a filter with 700 to 1600, or with a higher number of holes per 1 cm ² and the thus prepared pulp or regranulate can be used either separately or in a mixture with each other, with common raw materials, with agglomerate and with finely chopped fiber waste, spun at temperatures of 235 to 310 °C, preferably 235 to 280 °C, spun at a speed of 70 to 1600 m/min., with a spinning ratio of 1:2 to 1:5.5, preferably 1:3 to 1:4. 3. The method according to point 1 or point 2, characterized in that either 0.1 to 0.3% of the stabilizer 1,1-bis(2-methyl-5-tert-butyl-4-di-tridecylphosphonitephenylol) butane with the chemical structure ^H 21 ^C 15 °\ can be added P~ ^W 27 ^C /3~° op or its mixture in a 1: 1 ratio with zinc caprylate with the chemical structure (C7Hi5COO)2:Zn, or the other component of the mixture is 0.05 to 0.2% phenolic substance from those listed in point 1.