RU2671120C1 - Method for preparing precursors for orientational pull-up of the tape yarn from uhmwpe - Google Patents

Abstract

FIELD: natural and chemical threads and fibers.

SUBSTANCE: method of manufacturing precursors for orientational stretching of film threads from ultrahigh molecular weight polyethylene – UHMWPE refers to the initial stage of manufacturing high-strength high-modulus film filaments from the specified polymer by carrying out orientational stretching of the inventive precursors. Method of manufacturing precursors for orientational stretching of film filaments from ultrahigh molecular weight polyethylene includes: selection of UHMWPE reactor powder by morphological properties; compaction of UHMWPE reactor powder at room temperature with a degree of compression deformation – ratio of sample thicknesses before and after completion of compaction Θ = S_starts/S_ends = 2.0–2.2; monolitization of compacted UHMWPE reactor powders at temperature of 130–135 °C.

EFFECT: inventive method is characterized by high processability and does not require technologically complex and energy-consuming devices for its implementation.

1 cl, 20 dwg

Description

A method of manufacturing precursors for orientational drawing of film filaments from high molecular weight polyethylene - UHMWPE refers to the initial stage of manufacturing high-strength high-modulus film filaments from the specified polymer by orientational drawing of the inventive precursors.

UHMWPE products have high chemical resistance, impact resistance, frost resistance, wear resistance, high abrasion resistance, low density, good antifriction, strength and ballistic properties, which causes an increased growth in their demand. These properties lead to wide areas of application of high-strength film threads from UHMWPE, including: the manufacture of floating ropes, cables and networks, often used in the Arctic. Fabrics made from such threads act as a reinforcing base for composite materials providing ballistic protection.

The inventive method relates to the initial stage of manufacture of such products.

Difficulties in the processing of UHMWPE reactor powders into high-strength high-modulus film filaments from UHMWPE are associated with the fact that upon heating, UHMWPE passes not into a viscous, but into a highly elastic state due to the high molecular weight of the polymer, which results in a high value of the viscosity coefficient and the elastic modulus of the melt. When UHMWPE is processed on an industrial scale by sintering, hot pressing and plunger extrusion, an intensive occurrence of thermomechanical destruction processes is observed. This requires the use of technologies and plants that maximally preserve the unique properties of the starting polymer for the manufacture of products from UHMWPE reactor powders.

The aim of the present invention is the manufacture of precursors for orientational drawing of film filaments from UHMWPE while observing the minimum values of thermomechanical destruction.

The inventive method relates to the initial stage of obtaining high-strength high-modulus film filaments from reactor powders of UHMWPE in a solvent-free way. This method is of great interest due to its high environmental friendliness, technological and fire safety, compared with the method of "gel technology". Using the method of "gel technology" has already been achieved on an industrial scale for the final fibers of high values of the modulus of elasticity and strength, amounting to about 10% of the theoretical limit. However, the method of "gel technology" involves the use of large volumes of harmful organic solvents, requires high costs for the regeneration of the solvent and the creation of a closed process.

The solvent-free method for producing high-strength high-modulus film filaments from UHMWPE reactor powders involves the sequential carrying out of the following stages:

- selection of UHMWPE reactor powder with experimentally identified morphology, which allows to successfully carry out the subsequent stages of the process;

- compacting reactor powder;

- monolithization of a compacted reactor powder;

- orientational drawing of monolithic films.

The stages of compactification and monolithization of the reactor powder, which are decisive in creating the morphology necessary to achieve high mechanical properties of the film fibers from UHMWPE after carrying out orientational drawing, were reflected in the inventive method.

The technical result of the claimed invention is the development of a method for producing orientation precursors of film filaments from UHMWPE with the aim of obtaining high-strength high-modulus film filaments and fibers.

, проведения монолитизации компактизированных реакторных порошков СВМПЭ при температуре 130-135°С.The technical result is achieved due to: selection of UHMWPE reactor powders by morphological properties, compacting UHMWPE reactor powder at room temperature with a degree of compression deformation - the ratio of sample thicknesses before and after compaction

monolithization of compacted UHMWPE reactor powders at a temperature of 130-135 ° С.

It is known that due to the variety of catalytic systems and synthesis regimes for UHMWPE reactor powders, it is possible to obtain them with significantly different morphology:

So, when synthesizing UHMWPE reactor powders using a TiCl ₄ catalyst without a carrier, globules with a thin lamellar structure are formed;

The use of this catalyst supported on xerogel of silicic acid Al ₂ O ₃ ⋅ SiO ₂ leads to the appearance of a network structure, the nodes of which are small globules connected by a large number of extended fibrils oriented along the radius to the node;

The use of TiCl ₃ ⋅ 0.3 AlCl ₃ / MgCl ₂ as a carrier of magnesium chloride leads to the formation of mainly spiral structure of crystallites on folded chains.

In addition, when the synthesis temperature is increased from 20 to 90 ° C using active supported Ziegler-Natta catalysts, a significant increase in the number and linear sizes of fibrils binding globules is achieved.

The characteristic morphology of the particles of the UHMWPE reactor powder is an aggregate of smaller spheroid subunits connected by fibrillar cords containing lamellar residues. FIG. 1a and 1b.

The invention is illustrated in FIG. 1-7.

FIG. 1. Microphotographs of the UHMWPE reactor powder manufactured by Tomskneftekhim M _η = 3.69 × 10 ⁶ g / mol obtained by scanning electron microscopy with different image resolutions.

FIG. 2. Micrographs of individual particles of UHMWPE powders with different average particle diameters of the reactor powder grains: a - 12 μm, b - 20 μm, c - 3 μm.

FIG. 3. Compression strain curves of reactor powders with various average viscosity molecular weights: 1 - M _η = 1.7 × 10 ⁶ g / mol; 2 - M _η = 4.6 × 10 ⁶ g / mol; 3 - M _η = 5.0 × 10 ⁶ g / mol.

FIG. 4. Compression strain curves of compacted reactor powders with different relaxation times: 1 - 1 min, 2 - 4.4 × 10 ⁴ min, 3 - 1.0 × 10 ⁶ min, 4 - 1.3 × 10 ⁶ min.

, 6 - окончание компактизации

, в - давление выше давления компактизации

.FIG. 5. Microphotographs of the surface of tablets of UHMWPE reactor powders at various degrees of compression deformation (at various applied pressures): a - the beginning of compaction

, 6 - end of compaction

, in - pressure above compaction pressure

.

FIG. 6. Micrographs of the surface of tablets of UHMWPE reactor powders having different spinning properties subjected to compression deformation at various applied pressures: a, c, e — polymer with low spinning properties, b, d, e — polymer with high spinning properties; a, b - the beginning of compaction P = 54 MPa; c, d — completion of compaction P = 135 MPa; d, e - pressure above the pressure of compaction P = 680 MPa.

FIG. 7. Microphotographs of the surface of monolitized films of UHMWPE reactor powders with different average viscosity and obtained at different temperatures: A and B - powders with high spinning properties, C and D - powders with low spinning properties; A and C - 75 ° C, B and D - 135 ° C.

An experimentally established relationship between the morphology of reactor powders and the properties of the dope. Samples of UHMWPE reactor powders of OAO Tomskneftekhim with a viscosity average molecular weight M _η = 1.26-6.31 × 10 ⁶ g / mol were investigated. Promising reactor powders for producing precursors are recognized as powders with high spinning properties, having the following morphology: average particle diameter of the reactor powder 50-80 μm, average sub-particle size 8-14 μm, strands with a small amount of lamellar residues FIG. 2a. Reactor powders with a particle diameter not falling in the above range of values, as well as consisting of larger ones. FIG. 2b or smaller subunits FIG. 2c, they showed poor molding quality and were distinguished by a large number of fairly large lamellar residues in strands.

The second stage of the proposed method for the manufacture of orientational pulling precursors of film filaments from UHMWPE is compacting UHMWPE reactor powders. Carrying out the process of compacting UHMWPE reactor powders while observing the minimum values of thermomechanical destruction requires a process to minimize the distance between the particles of UHMWPE reactor powder while maintaining their internal structure, which is facilitated by a denser packing of subparticles in UHMWPE reactor powders with high spinning qualities.

, а увеличение продолжительности выдержки под давлением более 15 минут не приводила к существенному изменению степени деформации при значительном увеличении энергозатрат. Полученные экспериментальным путем зависимости, характеризующие процесс компактизации реакторных порошков с различной средневязкостной молекулярной массой М_η, представлены на Фиг. 3.The compaction of UHMWPE reactor powders with different average viscosity molecular mass M _η = 1.26-6.31 × 10 ⁶ g / mol was carried out for 15 minutes in a circular mold with a diameter of 13 mm with an applied pressure in the range P = 30-700 MPa. When the exposure time under pressure less than 15 minutes, the claimed degree of deformation was not achieved

, and an increase in the duration of exposure under pressure for more than 15 minutes did not lead to a significant change in the degree of deformation with a significant increase in energy consumption. The dependences obtained experimentally characterizing the process of compaction of reactor powders with different average viscosity molecular mass M _η are presented in FIG. 3.

достигается в узком диапазоне приложенного давления 120-150 МПа, что соответствует завершению процесса компактизации и достижению степени деформации сжатия

. На необратимость структурных изменений при компактизации реакторных порошков СВМПЭ указывает симбатность зависимостей толщины таблетки от давления при временах релаксации от 1 до 10⁶ минут Фиг. 4.It was found that the dependences, despite the difference in the average viscosity molecular mass M _η , are similar and the maximum degree of compression deformation

achieved in a narrow range of applied pressure of 120-150 MPa, which corresponds to the completion of the compactization process and the achievement of the degree of compression deformation

. The irreversibility of structural changes during the compaction of UHMWPE reactor powders is indicated by the symbatic dependence of the tablet thickness on pressure at relaxation times from 1 to 10 ⁶ minutes. FIG. four.

, а Фиг. 5 демонстрирует изменения, происходящие в таблетке при давлении выше 90 МПа.When analyzing the dependencies of FIG. 3, an unexpected fact is revealed: the thickness of the tablet with an increase in the applied pressure initially decreases to pressures of 120-150 MPa, then, surprisingly, despite an increase in the applied pressure to 400-500 MPa, it grows, and finally it begins to decrease. The presence of a change in the structure of UHMWPE reactor powders with a change in the applied pressure in the range 54–680 MPa is confirmed by electron microscopy data. FIG. 5. characterizing the process of compaction. So FIG. 5a characterizes the initial stage of the process, FIG. 56 indicates the end of the compaction process when the degree of compression deformation is reached

, and FIG. 5 shows the changes occurring in a tablet at a pressure above 90 MPa.

In the initial portion of the curves, a decrease in tablet thickness occurs due to a decrease in the free volume of the reactor powders. FIG. 5a up to the closure of the pores of FIG. 5b, a further increase in the applied pressure causes elastic reversible deformation with a simultaneous competing process of cold monolithization. A limited amount of free space in the polymer after the completion of the compaction process limits the growth of elastic reversible deformation with an increase in the applied pressure, which, along with the increase in the process of “cold” monolithization, interrupts the growth of the tablet thickness due to the increase in elastic forces and subsequently leads to a decrease in tablet thickness. In this case, the removal of the load from the sample leads to destruction processes in the polymer due to the partial rupture of the interstructural bonds formed during the cold monolithization process. FIG. 5c.

The process of compacting reactor powders having different morphologies, and therefore different spinning qualities, is shown in FIG. 6. A slight mechanical degradation of the polymer having the claimed morphology is observed. FIG. 6b, 6d, 6e, respectively, corresponding to the beginning of compaction, the end of compaction and the post-compaction process, and significant for UHMWPE reactor powder with a different morphology than the claimed FIG. 6a, 6c, 6d, respectively, corresponding to the beginning of compaction, the end of compaction, and the post-compaction process.

UHMWPE reactor powders of the claimed morphology, dense packing of subparticles, along with a loose bulk structure, form stable dense tablets due to significant interactions between powder particles during compaction, which form strong bonds between UHMWPE reactor powder particles.

The inventive method of compacting reactor powders of UHMWPE allows to minimize the mechanical degradation of the polymer.

становится сравнимой с максимальной степенью деформации сжатия достигаемой в процессе компактизации

, что указывает на почти полное подавление упругой обратимой деформации. Этот факт открывает возможности для проведения процесса «холодной» монолитизации при дальнейшем увеличении приложенного давления за счет повышения температуры на границах частиц реакторного порошка, вплоть до температуры плавления, при их смещении друг относительно друга под влиянием приложенного давления.In addition, in the analysis of FIG. 3, we observe that for a reactor powder with the maximum degree of deformation tested and having the maximum average viscosity molecular weight FIG. 3, sample 3 degree of deformation at a pressure of 750 MPa

becomes comparable with the maximum degree of compression deformation achieved during compaction

, which indicates an almost complete suppression of elastic reversible deformation. This fact opens up possibilities for the process of “cold” monolithization with a further increase in the applied pressure due to an increase in temperature at the boundaries of the particles of the reactor powder, up to the melting temperature, when they are displaced relative to each other under the influence of the applied pressure.

The third stage of the proposed method for the manufacture of precursors of orientational drawing of film filaments from UHMWPE is the process of monolithization of compacted UHMWPE reactor powders. To achieve the objectives of the claimed invention, the process is carried out at a slight pressure and the lowest possible temperature sufficient to obtain a uniform transparent monolithic UHMWPE film.

It was experimentally established that the monolithization of compacted UHMWPE reactor powders to obtain a uniform transparent monolithic film occurs at a temperature of 130-135 ° C. This is confirmed by scanning electron microscopy micrographs of FIG. 7. So, on microphotographs of the surface of UHMWPE reactor powders monolitized at a temperature of 135 ° C according to the proposed method, the formation of a uniform transparent monolithic UHMWPE film is shown. FIG. 7B and 7G for samples, respectively, with an average viscosity molecular weight M _η of 4.32 × 10 ⁶ g / mol and 3.69 × 10 ⁶ g / mol. When the temperature drops below the claimed temperature range, the resulting film is matte and inhomogeneities are observed on it. FIG. 7A and 7B for samples, respectively, with an average viscosity molecular weight M _η of 4.32 × 10 ⁶ g / mol and 3.69 × 10 ⁶ g / mol. An increase in temperature above 135 ° C leads to significant thermal degradation of the polymer, which does not meet the objectives of the claimed invention.

The method is as follows:

с получением устойчивых плотных образцов. Далее проводится их монолитизация при температуре 130-135°С с получением однородной прозрачной монолитной пленки.According to the declared morphological properties, UHMWPE reactor powder is selected - reactor powder manufactured by OAO Tomskneftekhim with a medium viscosity molecular weight M _η = 3.69 × 10 ⁶ g / mol with a particle diameter of reactor powder of 55 μm, a subparticle size of 12 μm and strands with a small amount of lamellar residues. Then it is compacted at room temperature with a degree of compression deformation - the ratio of the thickness of the reactor powder before and after completion of compaction

with obtaining stable dense samples. Next, they are monolitized at a temperature of 130-135 ° C to obtain a homogeneous transparent monolithic film.

, например, вертикальный пресс; обогреваемой камеры обеспечивающей нагревание компактизованных образцов СВМПЭ до температуры 130-135°С; необогреваемых вальцов для осуществления приемки, калибровки и направленной ориентации однородной прозрачной монолитной пленки; транспортеров для перемещения образцов между устройствами.The inventive method is highly technological and does not require for its implementation such technologically complex and energy-intensive devices, such as heated rollers and heated molds. To implement the inventive method for producing precursors for orientational drawing of film filaments from UHMWPE, it is enough to include in the process chain in series: devices for pressing UHMWPE reactor powders at room temperature with a exposure time of 15 minutes under pressure to achieve the degree of compression deformation

for example, a vertical press; a heated chamber providing heating of compacted UHMWPE samples to a temperature of 130-135 ° С; unheated rollers for acceptance, calibration and directional orientation of a uniform transparent monolithic film; conveyors for moving samples between devices.

Claims (1)

A method of manufacturing precursors for orientational drawing of film filaments from ultra-high molecular weight polyethylene, including: selection of UHMWPE reactor powder by morphological properties; compacting the UHMWPE reactor powder at room temperature with the degree of compression deformation - the ratio of the thicknesses of the sample before and after the completion of compaction θ = s _beg / s _con = 2.0-2.2; monolithization of compacted UHMWPE reactor powders at a temperature of 130-135 ° С.

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