FR2557599A1 - PROCESS FOR SPINNING SYNTHETIC FIBERS BY EXTRUSION OF THERMOPLASTIC POLYMERS AND FIBERS OBTAINED - Google Patents

Abstract

THE PRESENT INVENTION CONCERNS A PROCESS FOR SPINNING SYNTHETIC FIBERS BY EXTRUSION OF THERMOPLASTIC POLYMERS IN WHICH THE MIXTURE WITH THE SAID POLYMERS IS PROVIDED BEFORE THE STEARATE-BASED ADDITIVE EXTRUSION STEP; THE FIBERS OBTAINED BY THIS PROCESS CONTAIN AN ADDITIVE BASED ON STEARATE ACCORDING TO CONCENTRATIONS VARIING IN THE RANGE OF 0.03 TO 0.3 BY WEIGHT

Description

The present invention relates to a spinning method

  synthetic fibers by extrusion of thermopolymers

plastics and the fibers obtained.

  It is known that the extrusion of thermoplastic polymeric materials (by thermoplastic polymeric materials means, for example, polymers with an amide or ester structure) involves the use of dies comprising a worm screw arranged to rotate in a heated drum to melt the thermoplastic and extract it

  simultaneously through the dies or in molds.

  The thermoplastic polymer material is usual-

  fed in the form of granules or flakes and feeding it involves energy both in the form of thermal fusion energy and mechanical energy

extraction.

  The molten polymer sometimes has an abnormal behavior in the extrusion process and it can be, for example, non-constant flow rates while the rotation of the die is unchanged or variable rates which are not a function of the rotation of the sector. The reasons for which the molten polymer behaves abnormally in the die are numerous: there are favored intermolecular cohesion forces which cause irregular mass ratios for a given flow rate, molten metal-polymer adhesion forces (which form throughout the device) _which can cause irregular flow behavior as the speed

of the screw varies.

  Although the use of additives to assist in uniformity of flow of the molten thermoplastic polymer

  through the extruder and to improve the characteristics

  that the product has been known for a long time, the application

  such additives to textile fibers involve difficulties

  considerable amounts taking into account the moderate quantities which must be introduced and which must not adversely affect the properties of the yarns as well as the problem of homogenization of the additive with the granules

of thermoplastic material.

  The object of the present invention is to provide an additive which can impart improved extrusion characteristics to a thermoplastic material for textile fibers. The present invention also provides an additive helping to improve the mechanical characteristics of the

  extruded material while improving its drawing power.

  In fact, a remarkable characteristic of a fiber obtained by means of a melt spinning process is the drawing which regulates the quantity of material which can

be processed on a chain.

  In fact, during subsequent stretching processes, it becomes possible for a given final count to have an initial count, as obtained during spinning, which is

  higher the greater the drawing power of the product.

  Thus, spinning machines can, for a given capture speed, produce higher counts

  and therefore a greater product flow per unit of time.

  The behavior of the thermoplastic polymer during the extrusion process is studied, in this specific case, on small extruders of the type of those

  used with rheometers, capable of regulating the temperature

  erasing of the polymer at various points on the extruder screw

  as well as the amount of energy absorbed by the electric motor driving the screw and the flow of material as the rotation per minute changes. The ideal behavior of a polymer during extrusion processes requires low energy inputs and flow rates which increase linearly with the screw of the extruder determining the

overall flow rate.

  It has also been observed that the polymer material is also irregular when there is an irregular behavior in the rheometer-die with large dies such as those used in spinning by

melted track.

  A uniform flow rate ensures a suitable treatment by extrusion and avoids that part of the material remains too long in the die with the risk of local overheating and thermal degradation of the macromolecular chains of the polymer and a consequent loss of the quality of the product. In addition, a uniform flow of the molten product through the die allows the electric motor to operate effortlessly, which reduces the

  electrical energy consumption.

  The present invention provides a method which overcomes the drawbacks of the prior art by providing a method of spinning synthetic fibers by extrusion of thermoplastic polymers in which said polymers are mixed before extrusion with an additive based on

stearate.

  It has now unexpectedly been found that a particular class of additives can provide a smooth flow of molten material through the dies, with considerable advantages for application to spinning systems where the dies are used for transport.

en masse.

  In addition, a polymeric material containing the additives

  in question shows particular structural characteristics

  special with regard to the drawing of the product in the form of a wire, which allows among other things to have a yield

increased extrusion apparatus.

  The class of the compounds is that of stearates having an ester or amide chemical structure; particularly preferred are stearates which contain one or more stearoyl and / or stearyl groups: X-NH-Y, X-OY, XOR-OX, X-NH-R-NHX, Y-NH-R-NH-Y, YOROY , o R is the stearoyl group CH3 (CH2) 16-CO, Y is the stearyl group CH3 (CH2) 17-;

  R - an alkyl, aryl, alkylaryl group. -

  In particular, the present invention contemplates the use of stearyl stearate as an additive, as indicated in the examples below which have been carried out on an experimental apparatus as mentioned. The amounts to be used vary from 0.005% to 1%, preferably from 0.03% to 0.3 X, depending on the polymer used. Textile fibers are very sensitive to the presence of additives which can affect their characteristics

  as their ability to be tinted, the stability of the

  their, etc. For this reason, it is extremely important

  additives are introduced in very small quantities.

  O10 The major problem is therefore to ensure an intimate homogenization of the small quantity of additive across the mass of the polymeric material in order to obtain uniform characteristics for the products and consequently to avoid

  very significant local undesirable accumulations.

  The present invention allows the addition of a quan-

  number of additives belonging to the above classes and according to

  the quantities required and indicated at a mass of-

  thermoplastic polymer before spinning and in particular

  either before or after the drying operation.

  A drying step is planned for the polymer

  thermoplastic useful in the production of synthetic fibers

  which is carried out at a temperature in the range of about 110 ° C to 130 ° C in rotary driers which mix large amounts of granules of polymeric material for a period of a few hours. The addition of an additive chosen from the aforementioned class at this stage brings certain advantages, the melting point of the additives in question being lower than that at which

  drying is carried out. During the drying stage, the addi-

  tif is present in a fluid state and can flow over the polymer granules to distribute over them in a uniform manner forming a film. The good distribution of the additive is helped by the mixture to which the granules are subjected which exert a destructive effect on the possible

additive agglomerates.

  At the outlet of the dryer, the granules of material - polymer have their surface in the form of a uniform film.

very fine.

  During the extrusion operations, the additive melts around the screw with the polymer granules and it is distributed homogeneously over all of the molten product, which of course facilitates the extrusion of the material. Other advantages associated with the use of the substances described above are regular operation of the die and there is also the possibility of lowering the temperatures of the heating zones of the die to obtain a molten polymer of suitable viscosity for

the subsequent spinning operation.

  The possibility of working at low temperature is advantageous with polymers which tend to degrade

at processing temperatures.

  Another advantage that results from the presence of

  additives based on stearate concerns the mechanical properties

  ques improved extruded material.

  Various advantages and features of this

  invention will emerge from the detailed description below

  made with reference to the appended drawings in which: - Figure 1 is a graph showing the effect of adding the additive according to the invention; in this figure, the flow velocities of the polymer are plotted on the abscissa

  in n.g. (min -1) and on the ordinate rotation / min. 1 name-

  mée Q. - Figure 2 is a graph showing the effect of adding the additive according to the invention; in this figure, the flow velocities of the polymer are plotted on the abscissa in n.g. (min. -1) and the energy of the screw in ordinate

Nm according to rotation per minute.

  - Figure 3 is a graph similar to that of

  Figure 1 in which the added product is different.

  - Figure 4 is a graph similar to that of

  Figure 2 in which the added product is different.

  The invention will be better understood from the examples

non-limiting below.

Example 1

  5 kg of polyethylene terephthalate are dried under vacuum

  lene containing 0.04% stearyl stearate to a residual water value of 0.006%. The polymer is added under a stream of anhydrous nitrogen into the hopper of a Brabender rheometer using a single screw extruder having

a diameter of 20 mm.

  The graph in FIG. 1 o are plotted respectively on the abscissa and on the ordinate the polymer flow speeds and the rotation per minute of the corresponding die, illustrates a rectilinear relationship Q / n.g .. This graph compares the behavior of terephthalate

  polyethylene as is with that of poly terephthalate

  ethylene containing 0.04 Z of stearyl stearate. We cons-

  tate that there is an irregular behavior in the range of

at 60 rpm.

  This example therefore demonstrates the importance

  of the additive to have the linear relationship Q / n.g ..

  The graph in Figure 2 shows the energy input in Newtons per meter (Nm), as a function of the rotation in

rpm. of the Brabender screw.

  The presence of the stearate-based additive ensures linear behavior which would otherwise be irregular

  with much higher energies.

Example 2

  5 kg of Nylon 6 containing 0.1% N, N'ethylene ethyl bisdearearamide are vacuum-packed to a water value

  0.08 Z residual. The polymer is fed under a

  rant of anhydrous nitrogen in the hopper of a Brabender rheometer.

  The graphs in Figures 3 and 4 illustrate respec-

  the behaviors of Q / n.g. and N.m / n.g in the presence

and in the absence of the additive.

  In this example, it is also confirmed that the molten polyamide 6 undergoes regular mass transport at

  through the die while varying the rotation by-

  minute when the stearate additive is added to

the quantities indicated.

  Two samples of the polymer extruded at a rate of

  rpm which contain and which do not contain respec-

  The distearamide additive shows a crystallinity of 41% and 36% as determined on a Mettler instrument for the different thermal analysis.

  which indicates an improved crystallinity accompanied by

  with improved mechanical properties of the extrudate.

  Another series of analyzes and tests has been conducted to demonstrate how the use of stearyl stearate as an additive for textile fibers leads to a

  unexpected improvement in the drawing power of the product.

  The tests are carried out, for comparison, on a sample of common wire (ST) and on a sample containing stearyl stearate in the percentages

indicated.

  The mentioned improved characteristics of poly-

  mother treated with the additive of the present invention are described in the series of analyzes and tests below carried out compared with a sample of yarn containing

  the additive and on a sample of yarn of ordinary composition

nary (ST).

  It should be noted that due to the addition of the additive, an improved drawing power is obtained without any prejudice to any of the properties and characteristics of the wire. The production rate expressed in percent increases for the material treated with regard to extrusion per unit of time by a value of 6 to 7% while at the same time there is an increased

of the mentioned stretching power.

Example 3

  The tests are carried out at two different capture speeds, namely 4000 and 5000 m / minute. The results obtained for this latter speed are indicated

  in brackets in Table 1 below.

  In table 1, the additive used is stearate

  commercially available stearyl.

  Reference Additive Filament count (dtex / number 27.2 / 7 (27/7) 29.3 / 7 (28.7 / 7) 0 tenacity (cN / Tex) 45.6 (42.7) 42.7 (41 , 8) Elongation (Z) 72 (78) 77 (79) initial module 136 (120) 117 (116) (cN / Tex) Filament counting (dtex / N 21.9 / 7 (21.8 / 7) 22, 2/7 (22/7) tenacity (cN / Tex 42.2 (43, 5) 43.6 (43.8) Elongation (x) 28.2 (28.9) 27 (28) Initial module 189 (190 ) 202 (198) Embossing stiffness (Z) 50 (55.5) 51 (51.2) Embossing shrinkage (%) 62.5 (64.5) 62 (64) w Embossing module (X) 45, 4 (45.9) 43 (45.6)! Embossing stability () 79 (74.8) 74 (73.8) Drawing K 1.24 (1.24) 1.32 (1.30) Table I : Comparison between the characteristics of Nylon 6 fibers which contain 0.3% stearyl stearate and Nylon 6 fibers which do not contain such an additive The data in brackets relates to extruded yarns at a

speed of 4,500 m / s.

  (1) according to the Heberlein method (2) according to the Texturmat method

Claims (11)

  1. Process for spinning synthetic fibers by extrusion of thermoplastic polymers, characterized in that the polymers are mixed before their extrusion with a stearate-based additive. 2. Method according to claim 1, characterized in that said additive is chosen from-stearates having   an ester or amide chemical structure.   3. Method according to claim 2, characterized in that said additive contains at least one or more stearoyl or stearyl groups.   4. Method according to claim 3, characterized in that the stearoyl and / or stearyl groups are present in compounds having a general formula chosen from   X-NH-Y, X-O-Y, X-O-R-OX, X-NH-R-NHX, Y-NH-R-NH-Y, Y-O-R-O-Y,   o R is an alkyl, aryl or alkylaryl group and X is the stearoyl group CH3 (CH2) 16-CO-, and Y is the stearyl group CH3 (CH2) 17-.   5. Method according to claim 1 comprising a drying operation of the thermoplastic polymer upstream of the extrusion operation, characterized in that the mixture is used concurrently with said drying operation. 6. Method according to claim 5, characterized in that the additive is added at a concentration included in the range of 0.1 to 0.3%.   7. Method according to claim 6, characterized-   in that the additive is stearyl stearate.   8. Method according to claim 6, characterized   in that the additive is ethylenebisdistearamide.   9. Method according to claim ô, characterized in that the thermoplastic polymer ast of terephthalate polyethylene.   10. Method according to claim 1, characterized   in that the thermoplastic polymer is polyamide 6.   11. Fiber obtained by the process according to any urea   as claims 1 to 10, characterized in that it O10 contains said additive.   12. Fiber according to claim 11, characterized   in that said additive is introduced according to concentra-   tions varying between 0.03% and 0.3% by weight.   513. Fiber according to claim 11, characterized in that the concentration of the additive extends in the range from 0.1% to 0.3% by weight.