CS246153B1 - High-elastic isotactic polypropylene fiber with improved elastic properties and manufacturing method - Google Patents

Abstract

The solution concerns a highly elastic fiber made of isotactic polypropylene with improved elastic deformability during deformations to rupture, reduced dependence of elastic recovery on the number of deformation cycles and high uniformity of elastic recovery values. The method of fiber production consists in using a polymer with a narrow molecular weight distribution and finding technological parameters of spinning and heat treatment using parameters of the supramolecular structure, especially its non-crystalline regions.

Description

The present invention relates to an isotactic polypropylene fiber having improved deformability under break-strain as evaluated by the EZ elastic recovery parameter, an improved EZ dependence on the number of strain-relief cycles, and a method for producing the same.

Over the past twenty years, considerable efforts have been made to prepare fibers from different synthetic semi-crystalline polymers that exhibit elastic properties similar to elastomeric fibers - high elastic deformability, maintaining a high percentage of elastic recovery after stress relief, and maintaining the original elastic recovery after repeated deformations. At the same time, basic mechanical properties - strength and modulus of elasticity - at the level of textile fibers are required. Such fibers have been prepared with good results from a series of synthetic fiber-forming polymers having a high crystallization rate. E.g. Belgian patent 650,890 describes the preparation and properties of elastic polyoximethylene fibers. U.S. Patent 3,299,171 fibers of polypivalolactone, U.S. Patent 3,081,519 elastic fibers of polyethylene. British Patent 962 231 elastic fibers from Celcon acetal copolymers, etc. Elastic fibers from other polymers are known, such as poly-3-methylbutene, polyethylene sulfide, and polyethylene terephthalate.

Polypropylene is an important representative of polymers capable of forming elastic fibers. The elastic characteristics of the isotactic polypropylene fibers prepared by the stress-melt oriented crystallization mechanism are similar to those of Spandex elastomeric polyurethane fibers. Elastic polypropylene fibers prepared by various processes find use in both the textile industry and technical applications - eg manufacturing garments with the desired higher degree of elastic deformability such as underwear, sportswear, elastic stockings, socks, products requiring variable porosity as parachute silk , carpets with improved recovery properties, elastic nets, hair nets, elastic threads, products for medical purposes, etc.

The patent literature discloses elastic fibers from isotactic polypropylene and a number of processes for their preparation by melt spinning. U.S. Pat. No. 3,256,258 discloses a process for preparing an elastic polypropylene fiber by spinning a polymer having an IT flow index of 0.1 to 200 g / 10 min, at a temperature of 289 ° C, a draw speed of 45 m / s and subsequent heat treatment of the fiber at 105 to 160 ° C in an oven. At a deformation of 25 4, the fiber exhibits an elastic recovery greater than 82%, the deformation

8-2 to a break from 100 to 700% and a strength of at least 0.8. 10 N.m. From a structural point of view, a fiber with high elastic deformability is qualitatively characterized by high crystallinity and a highly ordered lamellar structure, quantitatively the orientation of the crystalline regions in the angles of 10 to 30 ° and so-called gamma intensity greater than one. radiation from the crystalline planes (022, 122) and the plane (110) on the meridian of the widescreen rontgenogram.

U.S. Pat. No. 3,323,190 discloses an elastic polypropylene fiber having an elastic recovery at 50% ^Ez deformation of greater than 90% and a process for its preparation by stretching the starting fiber in cycles of 10 to 50% but not more than 150% overall and subsequent heat treatment at 135 to 150 ° C for 3 to 30 min and further drawing to 40 to 80%.

Other patents disclose processes for preparing high elastic polypropylene fibers aimed at obtaining products with different mechanical properties - strength and modulus of elasticity. Processes for preparing elastic polypropylene fibers for further processing into special fibers for technical purposes, such as fibers with increased strength or porous fibers, are known in order to obtain the highest elasticity characterized by elastic recovery at deformations of 50-100%. U.S. Pat. No. 4,055,696 describes the preparation of a high-resilient polypropylene fiber to be further processed by spinning a polymer having a viscosity of? = 1.40 at a temperature of 230 ° C and a draw off speed of 610 m / min. at 140 ° C for 30 minutes in an oven.

Japanese patent 23,722 discloses the preparation of elastic, hollow polypropylene fibers intended for further processing into porous fibers by melt spinning at take-off speeds of 4,000 to 6,000 m / min; Japanese patent 137,026 discloses spinning polypropylene with IT = 1.0 at temperature German Patent 3,003,400 discloses the manufacture of a hollow elastic fiber of isotactic polypropylene for further processing, with an IT index of less than one, at a spinning temperature above 230 ° C.

A common feature of known processes for obtaining elastic fibers with an EZjq of greater than 90% is the use of special polymers of very high molecular weights, characterized by low IT and spinning at low spinning temperatures from 200 to 260 ° C.

Although the stated IT usability range is in the range of 0.1 to 200 g / 10 min with a preferred range of 0.5 to 30 g / 10 min, polymers with IT less than 1 g / 10 min are exclusively used, exceptionally higher in IT = 15-20 g / 10 min. The limited use of higher ITs is related to the need for the extremely higher draw-off speeds required to induce high melt stresses. High spinning stress is necessary to form nucleation centers from the upright chains of macromolecules, which are a precondition for initiating subsequent epitaxial crystallization of the polymer into high-order, large-sized lamellae oriented perpendicular to the fiber axis. The low IT corresponds to the relatively low draw-off speed v = 40 to 600 m / min, ensuring a high elongation below the nozzle p = 10,000 to 60,000% and good spinning certainty. The use of low IT at low spinning temperatures and corresponding draw rates entails the disadvantage of low fiber production with the desired starting structure. Further increasing the take-off speeds increases the unevenness of the fiber, deteriorates the spinning certainty and ultimately affects its elastic and other mechanical properties.

In order to improve the lamellar structure of the fiber and thereby improve its elastic properties, it is necessary to heat treat the starting fiber in air or in an inert environment. A temperature range of 100 to 160 ° C in free or stretched state, preferably 130 to 140 ° C in ft non-shrinkage state, is given. Said method of heat treatment results in uneven profixing of the inner layers of the winding and consequently a gradual deterioration of the elastic and other mechanical properties towards the inside of the spool. Depending on the thickness of the coil, the cooking time increases to 1.5 to 2 hours. At higher fiber coil thicknesses, the inner layers still show somewhat lower EZ values after this heat treatment period.

SUMMARY OF THE INVENTION The present invention is based on a high-elastic isotactic polypropylene fiber with improved elastic properties, various finenesses, and a process for producing it by high speed spinning, finding spinning technological parameters by determining the structural parameters of the starting fiber and increasing heat treatment efficiency.

These fibers have a strength of up to 2.5. 2θΝ.πι ² , elongation up to 300 i, crystallinity (3 _r ^ _g greater than 0,65, content of α'-orientated crystallites greater than 10%, orientation factor of crystalline regions f _c greater than 0,9, orientation factor of non-crystalline area f less than 0.1, relative proportion of straightened chains in non-crystalline regions n / N less than 0.1, low-angle scattering Δμρ / ΜΡ less than 0.2, volume fraction of interfibrillary linkers in non-crystalline regions greater than 0.02, a density difference between the crystalline and non-crystalline areas in the direction of the axis of more than 150 kg / m ³ ,

These structural parameters of the elastomeric fibers that ensures its elastic recovery EZ._ greater than 98% and EZ. "" Greater than 80 and such that the difference between EZ__ and EZ. "" 5 nepře2 25 MAX MAX ^r the considerable increase of 20%. The improved elastic properties of these fibers prepared under the above conditions are both high EZ to break and very little dependence of elastic recovery on the number of deformation cycles. A slight decrease in ΕΖ ^ θ values, not more than 5%, is after the first five cycles, after a further fifteen cycles it decreases by another 1 to 3% and changes only slightly as the number of cycles increases. The value of EZ ^ qq as a function of the number of deformation cycles - stress relief shall not exceed a steady state value of not more than 20%. The high uniformity of EZ throughout the fiber winding is characterized by a coefficient of variation of less than 1%. The observed temperature dependence of EZ is very low up to the melting point of the polymer - about 160 ° C.

The present invention further provides a process for producing high elastic fibers from isotactic polypropylene, providing the structural parameters and elastic properties mentioned above. The initial undrawn, highly pre-oriented fiber with a well developed lamellar structure is produced by melt spinning of a polymer with a narrow molecular weight distribution, characterized by a Q parameter ranging from 1 to 4, at a spinning temperature of 200-310 ° C, a blow rate of 0.1-2 m / with an air temperature of 20 ° C and an exhaust speed of 500 to 7000 m / min. The parameter Q is defined by the ratio ^M w / ^M n, where M _w is the weight molecular weight and M _n is the number molecular weight. The high elastic fiber with improved elasticity and high uniformity of EZ values is made from the initial non-drawn fiber under thermofixation conditions with improved efficiency, using saturated water vapor at elevated pressure, or continualising the thin-air heat treatment process to ensure uniform fiber heating. obtaining regular lamellar regions with high ordering as well as optimal structure of non-crystalline regions.

The determination of the technological parameters of the preparation of the starting fiber necessary for obtaining the best elastic characteristics consists in the determination of the polymer dosage, the spinning temperature, the fiber cooling rate under the die and the drawing speed. Control of these parameters can be ensured by monitoring the appropriate parameters of the madmolecular structure of the fiber. In order to determine the technological parameters of the production of high-elastic polypropylene fibers by the above-mentioned spinning process, the previously proposed methods of structure evaluation are insufficient and need to be extended by data characterizing mainly the arrangement of macromolecular chains in non-crystalline regions. To this end, it has proved necessary to supplement the methods for assessing the structure by establishing:

- content of α'-axis-oriented crystallites X _& apos ;, from wide-angle X-ray diffraction. radiation

- the orientation factor of the non-crystalline areas f _and m, by the combination of sound velocity measurement and wide angle x-ray. diffraction

- low-angle MP / MP size distribution, from low-angle X-ray scattering. radiation

- the relative proportion of straightened link chains in the non-crystalline regions n / N, from the measurement of the speed of sound

- volume fraction of linking chains of macromolecules in interfibrillar regions of Pp, from measurement of dynamic viscoelastic properties

- the density difference between the crystalline and non-crystalline regions producing periodicity Δ _? , from low angle x-ray. diffraction

- the porosity of the fiber during elastic deformation v, from a small angle X-ray scattering. radiation

Appropriate mechanical properties - strength, ductility and high elasticity of the starting fiber to achieve ΕΖ ^ θθ greater than 95% of the thermally fixed fiber, are conditional on achieving the following structural parameters before thermofixation:

- fiber crystallinity measured by wide-angle X-ray diffraction. radiation (2 _X-ray greater than 50%

- content. α'-axis-oriented crystallites X, greater than 10%

an orientation factor of crystalline regions of f _c greater than 0,9

- maximum on the curve of the orientation factor of non-crystalline areas on the elongation f =

3ΠΧ

- a size distribution of the low angle period ΔμΡ / ΜΡ of less than 0,3

- a relative proportion of straightened linkers in the non-crystalline regions of n / N greater than 0.05

- maximum on the curve of the relative proportion of straightened link chains in non-crystalline regions on the elongation

- the volume fraction of interfibrillary linkers in non-crystalline areas pp greater than 0,01

- density difference between crystalline and non-crystalline areas in the fiber axis direction Δ ^> greater than 120 kg / m ²

a porosity of the elastically deformed fiber by 50% v ≥ greater than 0.08

- the orientation factor of non-crystalline areas f · less than 0.4

The use of any type of polymer with a narrower molecular weight distribution, e.g., chemically or thermally degraded, positively affects the perfection of the crystalline structure of the lamellas, the uniformity of their thickness along the fiber axis and the uniformity of the periodicity of the density. Improved lamella arrangement is also reflected in a slight increase in α'-axis-oriented crystallite content, as compared to conventional polymer fibers, as a result of the increased orientation effect of the lamella surface. Size of crystalline regions before heat treatment, evaluated by wide-angle X-ray diffraction. The radiation is about 10 nm, compared to 6-8 nm for fibers prepared from a conventional polymer. The dispersion size of the low angle period ρμρ / ΜΡ shows values of 0.25 to 0.27 compared to 0.3 to 0.35 for fibers of conventional polymer.

The improved heat treatment efficiency over patented dryer fixation is based on the use of saturated water vapor at a pressure of 0.2 to 0.5 MPa, corresponding to temperatures of about 120 to 150 ° C, respectively, using a continuous thin heat treatment process This ensures a high uniformity of structure and hence elastic characteristics and other mechanical parameters. The cooking with saturated steam under these conditions to achieve the maximum ^EZ IOO Y ^{CH uniformly} throughout ^the thickness of the bobbin build-up is 10 to 30 minutes. the continuous treatment time is 3 to 20 minutes.

Example 1

Crystalline isotactic polypropylene, thermally degraded to Q-2.24, was spun at 280 ° C. The spinneret was 16 holes with a hole diameter of 0.5 mm and a ratio L / D = 4. The polymer dosing was 40 g / min, a draw rate of 3000 m / min, corresponding to a p = 16,000% elongation. Cooling of the fiber was ensured by blowing air at 20 ° C with a warm speed of 0.3 m / s. The initial pre-oriented fiber obtained under these spinning conditions had a crystallinity of λ _x = 0.56, an MP size of 12.5 nm, an α-axis content of 12.5%, f oriented crystallites X _and 0.92, f = 0, 36, relative proportion of straight chain in non-crystalline regions n / N = 0.05, volume fraction of interfibrillary porosity at deformation EZ _1Art = 65%,

0.02, Δμρ / ΜΡ = 0.27, Δρ = 155 kg / m ³ connecting chains by 50% v = 0.085. The elastic recovery of the fiber was EZ _OC = 78%, EZ _CA = 71%, p ' ¹ 25 50 100 after five deformation cycles, the value of ΕΖ ^ θ decreased to 54%, after 20 cycles to 51%.

The fiber was heat treated in an autoclave at a temperature of 140 Ca and a pressure of 0.4 MPa, wound on metal coils without the possibility of shrinkage. The cooking time was 15 minutes. The monitored structural parameters changed to the following values:

/ 3rtg ⁼ ° ' ⁶⁵ ' ^{MP =} 18Xa ' ^{= 10.5} = 0.02, Δμρ / μρ = o, i9, Δ ^>'%, f = 0.96, f = 0, n / N = 0.046, c am '''

170 kg / m, v = 0.09.

The elastic recovery of the high-elastic fiber was EZ ₂₅ = 98%, ΕΖ ^ θ = 96%, ΕΖ ₁₀ θ = 95.5%, ΕΖ ^ _5Αχ = 84%. After five cycles of deformation, the elastic recovery ΕΖ ^ θ fell to 92%, after twenty cycles to 89% and did not change depending on the number of cycles. Depending on the thickness of the winding, the elastic recovery did not show a decrease in values.

Example 2

Crystalline isotactic polypropylene chemically degraded to Q = 1.8 was spun under the same conditions as in Example 1. The polymer dosing was 30 g / min, the draw rate of 3500 m / min corresponding to a p = 25,700% elongation. The fiber was air cooled at 20 ° C at a rate of 0.3 m / s. The starting fiber had parameters of supramolecular structure:

/ 2. = 0.7, MI = 13.5 nm, X - = 12%, f = 0.94, f _m = 0.32, n / N = 0.06 = 0.025, and PRTG - c am «p

/Μρ / μρ = 0.26, θ = 220 kg / m. The elastic recovery of the starting fiber was EZ ^^ = 80%,

ΕΖ, -θ = 73%, ΕΖ ^ θθ = 68%, after five deformation cycles, the value of ΕΖ ^ θ fell to 64%, after twenty cycles to 60%.

246153 6

The heat treatment in a saturated water vapor autoclave was carried out under the same conditions as in Example 1. The parameters of the supermolecular structure were changed to the following values: / 3_ * ~ = 0.75, MP - 19.1 nm, X - = 10.2% f = 0.96, f = 0.05, n / N = 0.042, lips. a ~ c am jjp = 0.025, ΔΜΡ / ΜΡ = 0.19, Δ ^> = 270 kg / m, v _p = 0.11. Elastic recovery was EZ ₂₅ = = 98.5%, = 96%, ΕΖ ^ οο = 95.2%, ΕΖ ^ χ = 88%. After five deformation cycles, the elastic recovery ΕΖ ^ θ fell to 92.5%, after twenty cycles to 90.8% and remained virtually unchanged. The inner layers of the winding did not show reduced values of elastic recovery compared to the outer layer.

Example 3

Crystalline isotactic polypropylene thermally degraded during spinning was spun at 260 ° C. The nozzle was twenty-hole with a hole diameter of 0.5 mm. The polymer feed rate was 15 g / min, the used draw speed was 1600 m / min, which corresponded to a p = 30,500% elongation. The fiber was air cooled at 20 ° C with a warm speed of 0.1 m / s.

The Q value of the polymer was 3.4. The pre-oriented fiber had the following supermolecular structure parameters: Λ = 0.72, MP = 13 nm, λ = 21%, f = 0.94, f = 0.38,

1. tCf »3 - C 3 n / N = 0.064, pp = 0.03. ΔΜΡ / ΜΡ = 0.25, Ap = 190 kg / m ^J. The fiber porosity at 50% deformation was Vp = 0.15. The elastic recovery of the pre-oriented fiber was EZ ^ = 85%,

ΕΖ ₅ θ = 78%, ΕΖ ^ θθ = 72%, after five deformation cycles, the value of ΕΖ ₅ θ fell to 62%, after twenty cycles to 59%. The fiber wound on a metal coil heat treated in an autoclave at 120 ° C and a saturated water vapor pressure of 0.2 MPa for 30 min exhibited the following values of the observed structural parameters: _[ mu] _g ~ 0.78, MP = 19.5 nm, X - = 16.6%, F = 0.97 _0, f _m = 0.02, n / N = 0.044, p = 0.031 _p, Δμρ / ΜΡ = 0.18, y = 240 kg / ^m3.

The porosity of the elastically deformed fiber by 50% was = 0.18. The elastic recovery of the heat treated fiber was EZ ₂ ^ = 99.5%, EZ ^ q = 98.5%, ΕΖ ^ θθ = 96%, ΕΖ ^ χ = 90.5%, after five strain cycles ΕΖ ^ θ dropped to 95%, after 20 cycles to 93%.

The inner layers of the package did not exhibit reduced values of elastic recovery compared to the outer layer. The uniformity ΕΖ ^ θθ expressed by the coefficient of variation was v = - 0.8%.

Example 4

Crystalline isotactic polypropylene thermally degraded during spinning, with a Q value of 3.65, was spun at 240 ° C. The nozzle was ten-hole with a hole diameter of 1 mm, the polymer dosing was 12 g / min, the pulling speed used was 500 m / min, which corresponded to an elongation p = 23,800%. The fiber was air cooled at 20 ° C with a warm speed of 0.2 m / s. The pre-oriented fiber had the following non-molecular structure parameters:

/ _RTG 3 "0.70, MP = 12.5 nm, _and X - = 17%, _Q f = 0.93 f = 0.31 _ftm, n / N = 0.059, _p = 0.026 fi, Δμρ / ΜΡ = 0.29, Ay = 200 kg / m ³ . The fiber porosity at elastic deformation by 50% was at _p = 0.21. The elastic recovery of the pre-oriented undrawn fiber was EZ ₂₅ = 82%,

EZ, jq = 77%, ΕΖ ^ θθ = 71%, after five deformation cycles the value of ΕΖ ^ θ fell to 61%, after twenty cycles to 56%. The fiber wound on a metal coil heat treated in an autoclave at a temperature of 150 ° C and a pressure of 0.5 MPa for 10 min showed the following values of the observed structural parameters: $ rtg ~ ° ' ⁷⁵ ' ⁼ 19 nm, ^x a ⁼ 14.6% , f _o = 0.95, ^f and ^{m =} ° ' ⁰¹ ' ^{n / N =} ° ' ⁰⁷ ' Hp ⁼ ° ' ⁰³⁵ ' AmP / MP = 0.16, Δ _? = 205 kg / m ³ . The fiber porosity at its deformation by 50% was at _p = 0.26. Elastic recovery was ΕΖ ₂ ^ = 99%, ΕΖ ^ θ = = 97%, ΕΖ ^ θθ = 97%, ΕΖ ^ χ = 92%. After five strain cycles, the elastic recovery of the EZ _5Q dropped to 94%, after twenty cycles to 91% and remained virtually unchanged. The inner layers of the winding did not show reduced EZ values compared to the outer layer. The uniformity of ΕΖ ^ θθ values expressed by the coefficient of variation was v = - 0.9%.

Example5

A pre-oriented isotactic polypropylene fiber prepared according to the procedure of Example 3 and exhibiting both structural parameters and elastic properties as in Example 3, was thermally stabilized by a continuous process on metal temperature-heated galets.

130 [deg.] C.

The fiber was deposited on the galets in a thin layer by means of a storage roller, the thread next to the thread, so that the total residence time of the fiber in the fixing zone was 20 minutes. After passing through the fixing zone, the filament was wound onto coils. The high-elastic fiber after heat treatment showed the following values of monitored parameters: / 3 _r tg ”θ / ^ 5, MP ~ 20 nm,

X. = 17 µ, f = 0.96, f = 0.02, n / N = 0.05, = 0.03, ΔμΡ / ΜΡ = 0.15, θ = 260 kg / m ³ .

ac and IP ^{2 3}

The porosity of the elastically deformed fiber by 50% was σ = 0.24. The elastic recovery of the continuously thermofixed fiber was EZ ₂ ^ = 99.5%, ΖΖ ^ θ = 99%, ΖΖ ^ θθ = 98%, EZ ^ ^ = 92%.

After five deformation cycles, ΕΖ ^ θ fell to 96%, after twenty cycles to 94%. The inner layers of the package did not exhibit reduced values of elastic recovery. The uniformity of the ^EZ 100 elastic recovery values, expressed as the coefficient of variation, was v = ΐ 0.5%.

Claims (2)

Highly elastic isotactic polypropylene fiber with improved elastic properties, various finenesses, strength up to 2.5 cN / dtex, elongation up to 300%, characterized in that it has a high crystalline structure with a crystallinity / 3 _X-ray greater than 0.65, a content of and "-Axially oriented crystallites greater than 10%, orientation factor of crystalline regions f greater than 0.9, orientation factor of non-crystalline regions f less than 0.1, relative proportion of stranded chains in non-crystalline regions n / N less than 0.1, size variance small angle periods Δμρ / ΜΡ less than 0,2, volume fraction of interfibrillary linkers in non-crystalline areas at greater than 0,02, density difference 3 between crystalline areas in the fiber axis direction Δ0 greater than 150 kg / m and further having elastic deformability in the case of breakage deformations characterized by the EZ ₂₅ elastic recovery parameter greater than 98%, greater než 80%, dependence of EZ on the number of deformation cycles expressed by a decrease of Ε ^ θθ by not more than 20%, uniformity of EZ values throughout the fiber winding characterized by a coefficient of variation of up to -1%, ΕΖ ^ θθ not dependent on deformation temperature up to the melting point of the polymer. 2. A method for producing a high-elastic fiber from isotactic polypropylene according to claim 1, wherein the starting, non-drawn, highly pre-oriented fiber with a well-arranged lamellar structure, melt spun from a polymer characterized by molecular weight distribution in the Q range of 1 to 4 with crystallinity _rt větší greater than 50%, content of α'-axis-oriented crystallites X '- greater than 10%, orientation factor of crystalline regions f greater than 0.9, small-angle AMP / MP dispersion size less than 0.3, orientation factor of non-crystalline regions f less than 0.4, a relative fraction of straight strands in non-crystalline regions of n / N greater than 0.05 and a volume fraction of interfibrillary chains in non-crystalline regions of greater than 0.02 are heat treated wound on a non-deformable coil with saturated water vapor at 120 to 150 ° C, pressure 0.2 to 0.5 MPa after d both for 10 to 30 minutes or by continuous casting at 120 to 150 ° C for 1 to 20 minutes.