CA1140309A - Filaments with porous surface - Google Patents
Filaments with porous surfaceInfo
- Publication number
- CA1140309A CA1140309A CA000332832A CA332832A CA1140309A CA 1140309 A CA1140309 A CA 1140309A CA 000332832 A CA000332832 A CA 000332832A CA 332832 A CA332832 A CA 332832A CA 1140309 A CA1140309 A CA 1140309A
- Authority
- CA
- Canada
- Prior art keywords
- threads
- bath
- homogeneous mixture
- temperature
- polymer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007788 liquid Substances 0.000 claims abstract description 45
- 238000000034 method Methods 0.000 claims abstract description 33
- 229920000642 polymer Polymers 0.000 claims abstract description 31
- 239000000203 mixture Substances 0.000 claims abstract description 22
- 239000008240 homogeneous mixture Substances 0.000 claims abstract description 19
- 229910002056 binary alloy Inorganic materials 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 238000009987 spinning Methods 0.000 claims description 24
- -1 polypropylene Polymers 0.000 claims description 11
- 239000011148 porous material Substances 0.000 claims description 11
- 238000001125 extrusion Methods 0.000 claims description 10
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 claims description 6
- 239000004743 Polypropylene Substances 0.000 claims description 5
- 229920001155 polypropylene Polymers 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 4
- 239000000758 substrate Substances 0.000 claims description 4
- 238000011144 upstream manufacturing Methods 0.000 claims description 3
- 239000011810 insulating material Substances 0.000 claims description 2
- 238000007711 solidification Methods 0.000 claims description 2
- 230000008023 solidification Effects 0.000 claims description 2
- 229920001059 synthetic polymer Polymers 0.000 claims description 2
- 206010016256 fatigue Diseases 0.000 claims 1
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 208000012886 Vertigo Diseases 0.000 description 22
- 239000000126 substance Substances 0.000 description 9
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 6
- 239000012071 phase Substances 0.000 description 6
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 239000004480 active ingredient Substances 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 239000004745 nonwoven fabric Substances 0.000 description 3
- 238000010587 phase diagram Methods 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- JHIVVAPYMSGYDF-UHFFFAOYSA-N cyclohexanone Chemical compound O=C1CCCCC1 JHIVVAPYMSGYDF-UHFFFAOYSA-N 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 238000006068 polycondensation reaction Methods 0.000 description 2
- 239000004753 textile Substances 0.000 description 2
- 101100165177 Caenorhabditis elegans bath-15 gene Proteins 0.000 description 1
- 229920002292 Nylon 6 Polymers 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000004721 Polyphenylene oxide Substances 0.000 description 1
- 229920002396 Polyurea Polymers 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 239000002216 antistatic agent Substances 0.000 description 1
- 239000002666 chemical blowing agent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000000835 fiber Substances 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000012442 inert solvent Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000000314 lubricant Substances 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 229920000058 polyacrylate Polymers 0.000 description 1
- 229920002647 polyamide Polymers 0.000 description 1
- 229920001707 polybutylene terephthalate Polymers 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 229920000139 polyethylene terephthalate Polymers 0.000 description 1
- 239000005020 polyethylene terephthalate Substances 0.000 description 1
- 229920002959 polymer blend Polymers 0.000 description 1
- 229920006380 polyphenylene oxide Polymers 0.000 description 1
- 229920002635 polyurethane Polymers 0.000 description 1
- 239000004814 polyurethane Substances 0.000 description 1
- 229920000915 polyvinyl chloride Polymers 0.000 description 1
- 239000004800 polyvinyl chloride Substances 0.000 description 1
- 230000002028 premature Effects 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 239000002759 woven fabric Substances 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0023—Organic membrane manufacture by inducing porosity into non porous precursor membranes
- B01D67/003—Organic membrane manufacture by inducing porosity into non porous precursor membranes by selective elimination of components, e.g. by leaching
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/02—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor characterised by their properties
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/24—Formation of filaments, threads, or the like with a hollow structure; Spinnerette packs therefor
- D01D5/247—Discontinuous hollow structure or microporous structure
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Manufacturing & Machinery (AREA)
- Mechanical Engineering (AREA)
- Textile Engineering (AREA)
- Spinning Methods And Devices For Manufacturing Artificial Fibers (AREA)
- Artificial Filaments (AREA)
- Manufacture Of Porous Articles, And Recovery And Treatment Of Waste Products (AREA)
Abstract
ABSTRACT
Porous threads and a method for their production from a homogeneous mixture. The mixture comprises at least two components of which one is a fusible polymer and the other is a liquid which is inert towards the polymer.
These two components are such as to form a binary system having in the liquid state, a region in which they are totally miscible and a region in which there is a discontinuity in mixing. The mixture is extruded at above the critical temperature of the binary system into a bath of the inert liquid component having a temperature below the critical temperature and the thread structure formed is solidified.
Porous threads and a method for their production from a homogeneous mixture. The mixture comprises at least two components of which one is a fusible polymer and the other is a liquid which is inert towards the polymer.
These two components are such as to form a binary system having in the liquid state, a region in which they are totally miscible and a region in which there is a discontinuity in mixing. The mixture is extruded at above the critical temperature of the binary system into a bath of the inert liquid component having a temperature below the critical temperature and the thread structure formed is solidified.
Description
~2-The present invention relates to porous threads, a method of producing them and their use, in particular, as a support substance for active ingredients.
It has already been known for a long time to produce porous threads. In many cases, these threads are designated as foam threads.
A large number of methods for obtaining threads having a porous structure is already known. Thus, East German Patent No. 103 375 describes a method in which a pol~vmer melt consisting of one or more components, preferably components which are incompatible with each other, is extruded with the additon of physical and/or chemical blowing agents through one or more rows of holes in spinnerets with round, round and hollow or profiled and hollow spinneret holes. These threads can be de-posited so as to form non-woven fabrics by suitable processing.
The threads with cavities known hitherto have various disadvantages, ~d several methods thus lead to threads which only have cavities in the interior and which have a completely closed surface or possible a surface having slight permeability. Other threads whose surfaces exhibit opening are, however, produced with a surface which lS rough, thus rendering them unsuitable for many uses.
There is thus a need for improved methods of "'`~ ~
productio~ l partioular to provide methods by which the spiIming composition to be extruded can be produced simply and which operate without complicated spinning baths. There is also a need for improved threads which are porous, having openings on their surface but neverthe-less have a smooth surface structure, An object of the invention is therefore to provide a method by which polymers can be shaped in a simple manner in an extrudable spinning composition and which simultaneously allows extrusion and allows the extruded material to be solidified without complicated spinning techniques and spinning baths having to be used.
Another object of the invention is to provide a method which ailows threads having adjustable porosity to be obtained merely by varying the operating parameters.
An object of the invention is also to provide porous threads which have a desirable open surface relative to the known foam threads. A further object of the invention is to provide threads which can be used in the textile field as well as in industrial and other spheres and which are particularly suitable as a support substrate for certain active ingredients.
According to the presen-t invention there is provided a method of producing porous threads in which a homogeneous mixture is extruded, the homogeneous mixture comprisiIlg at least two oomponents, of which one oompon-ent is a fusible polymer and the other component is a liquid which is inert towards the polymer as ~erein-after defined), the two components forming a binary system, which llas, in the liquid sta-te, a region in which the components are completely miscible and a rsgion in which there is a discontinuity in, the homogeneous mixture being extruded at a temperature above the critical temperature of the binary system in to a bath containing said other inert liquid component of the homogeneous mixture and which is at a temperature below said critical temperature, and the thread structure so formed is solidified.
The fibre structure formed can be washed out using a solvent after solidification, acetone being particularly useful for this purpose.
It is advantageous if an air gap is included between the outlet surface of the extrusion tool and the surface of the bath. This air gap can be heated.
It is also possible to extrude the homogeneous mixture directly into the bath.
A bath having a staggered temperature is used in $ a particular embodiment of the me-thod according to the invention. In that embodimen~ the bath can comprise one or more parts which have a temperature gradient in such a way tha-t the temperature increases continuously _5 from the begining of the spinning bath to th~ outlet end. `
It is also possible to use two or more separate baths which each have a different temperature.
It has proved advantageous if the bath is at a temperature which i8 at least 100C lower than the critical temperature of the binary composition used.
Homogeneous mixtures of from 10 to 90/0 by weight of poly-mer and from 90 to 10 ~ by weight of inert liquid can be extruded according to the invention.
The homogeneous mixture can also initially be extruded into a spinning tube connected upstream of the bath and filledwith the bath liquid.
Polypropylene is preferably used as polymer and NN-bis-(2-hydro~yethyl)-hexadecylamine is preferably used as inert liquid.
The two components, namely the molten polymer and the inert liquid, are preferably mixed continuously prior to extrusion, in which process it is advantageous for mixing only to ta~e place immediately prior to e~trusion.
The mixture can still be homogenised prior to extrusion.
A pin mixer is particularly suitable for mixing purposes.
- ~ According to another aspect of the present invention there is provided porous threads comprisi~g a s~thetic polymer having from 10 to 90~0 by volume of pores which COmmUniGate with each other and a smooth surface structure haviIlg open pores, wherein the proporSion of openings in the surfnce thereof amounts to from 10 to 90%, Preferably the apparent density of the threads lies between about 10 to 90~ of the actual density of the polymer used.
The threads can be used as a support substrate, io e.
the threads can be impregnated with specific substances which are given off at a subsequent moment. They can also be used as insulating material.
It is possible to use, in particular, fibre-forming macromolecular substances which are known per se, particularly synthetic polymers which are obtained, for example, by polymerisation, polyaddition or polyconden-sation, for carrying out the method according to theinvention and for the production of threads according to the invention. The polymer must be fusible, i.e., it must be able to pass into the liquid state without decomposing and form a binary system with a liquid which is inert towards it, which system having a range of com-plete miscibility in the liquid state and also a range in the liquid state with mixing gaps.
Systems of this type have a phase diagram for the liquid state of, for example, the type shown for the aniline/hexane system on page 724 of the Text Book of physical Chemis-try by S. Glasstone, Macmillian and Co Ltd, St, ~artins~ Street, London, 1953. Thisdiagram indicates complete miscibility for the two components above -the arched curve. Two liquid phases are in equilibriu~ with each other beneath the curve~
It is not absolutely essential for carrying out the invention for each of the two components in thetwo-phase range still to exhibit considerably solubility relative to the other components, as is the case in the -above-mentioned graph. In many cases, it is sufficient to have marginal solubility in the liquid two-phase domain. It is however important for the two components in the liquid state to form two liquid phases next to each other. In this respect, the systems which can be used according to the invention differ from those systems in which the dissolved polymer is precipitated directly as a solid when the temperature is lower without firstly passing through the liquid state during the cooling treatment.
Conventional fusible polymers can be used within the scope of the invention, such as, for example the polymers obtained by polymerisation, such as, polyethylene, i polypropylene, polyvinylchloride, polyacrylates, poly caprolactam as well as corresponding copoly~ers among others; polycondensation polymers, such as, polyethylene terephthalate, polybutylene terephthalate, polyamide ~),6 polyphenylene oxide, and poly addi-tion polymers, such as, polyurethanes and polyureas.
All tho6e liquids which form a binary system of the above-mentioned type with the polymer in the liquid state are basically suitable as inert liquid within the scope of the invention. By the phrase "inert towards the polymer" as used herein, is meant that the liquid does not cause considerable decomposition of the polymer within a short period or does not react with the polymer itself.
Although the above-mentioned phase diagram of the state of the aniline/hexane sysb~mshows the ratios for a binary mixture which consists of two uniform substances which are themselves essentially pure, the term binary system should not be appled strictly, in the context of the invention, to mixtures of only two pure uniform substances. The average skilled man knows that a polymer substance is composed of a plurality of molecules of differing molecular weight, and these polymers with a corresponding molecular weight distribution are there-fore to be considered within the scope of the invention as one component, and the same applies to mixed poly-- ~ mers. Under certain circumstances, polymer mixtures can even behave as a uniform component and form a single phase mixture with an inert solvent and separate only into two liquid phases below a critical -temperature. It is preferable, however, to use only one polymer~ The liquid need not necessarily be completely pure and represent a completely uniform substance~ In many cases, it does not matter if relatively small quantities of impurities and possibly also proportions of homo-geneous c~mpounds of the type which are necessitated by industrial production are added.
In order to carry out the method in practice, a homo~
geneous mixture is produced from the two components at the required temperatures~ This can be effected by - mixing the inert liquids with the comminuted polymer heating it to suitable temperatures, ensuring that mixing is sufficiently thorough.
Another suitable method involves bringing the two components to the required temperature separately and mixing the two components together continuously in the desired proportion just before extrusion. This mixing can be carried out in a pin mixer which is advantageously arranged between themetering pumps for the individual components and the spinning pump. Subsequent homogen-isation may be advisable.
- ~ In many cases, it is advisable to aerate the homogeneous mixture by applying a suitable vacuum before extrusion.
The ratio of the polymer to inert liquid in the spinlling compositioIl can be varied within wide limits.
The interllal pore volume and also the surface texture as well as the number of open pores on the surl'aces of the hollow threads obtained, can be controlled to a large èxtent by adjusting the ratio of polymer to inert liquid.
Porous threads which are suitable for a very wide range of applications can thus be obtained.
It is generally sufficient for the temperature of the homogeneous mixture prior to extrusion to lie only a few degrees above the critical temperature or above the disintegration temperature, depending on the respective composition.
Interesting effects with regard to the texture of the threads obtained can however also be achieved by increasing the difference between the temperature of the homogeneous mixture to be e~truded and the critical temperature.
The homogeneous spinning composition is then extruded into a bath containing the inert liquid of the extruded component mixture and having a temperature below the critical temperature. The bath preferably consists completely or mainly oY the inert liquid which is also - $ present in the extruded mixture. The temperature of the bath lies below the critical temperature of the mixture used, i.e. below the temperature above which the two components can be mixed together completely homo-V3~)9 genevusly. The teloperature of the bath preferably liesat least 100C below the critical temperature O:e -the mixture used.
The temperature can also be sufficiently low to progress in the range in which a solid phase occurs according to the phase diagram relatingto the binary system.
Once the temperature of the bath is sufficiently high that it continues progressing in the liquid two phase region, then it is necessary to solidify the thread structure formed as soon as possible, which can be ef-fected by reducing the temperature accordingly after a certain interval inside the bath.
It is imp~rtant for the extruded mixture still to be single-phase before it enters the bath, i.e. for substantially no further disintegration into two phases~
to take place.
It has proven advantageous to arrange in front, upstream end of the bath in certain cases a spinning tube which is also filled with the bath liquid and the end of which is submerged in the spinning bath. The spin-ning tube can have a conventional spinning funnel at its inlet opening, and the tube can be curved at its lower end ~n order to make it easier to take off the thread through the bath.
V;~f~9 _12--The spinning tube can be filled by means of a level container surrounding the spinning tube as a result of overflow into the spimIing tube. In order to lill the spinning tube completely and to maintain the level in 5 it, it is necessary to supply more bath liquid to this level container from a main reservoir than flows out through the spinning tube. The excess bath liquid can be recirculated via a secondoverflow on the level cont-ainer into the main reservoir. The main reservoir and 10 level container can be controlled thermostatically.
Once it has passed from the spinning bath, the thread can be washed out with a suitable extraction agent.
A number of solvents such as, for example, acetone, cyclo--hexanone and ethanol as well as mixtures of these liquids, 15 are suitable for extraction~
In some cases, it is not necessary to wash out the thread, particularly when the actual inert liquid s used is to impart to the thread extra properties which are designed for its subsequent application or is even to 20 perform a function. Thus, for example, it is possible to use liquids which exert an anti-static effect on the thread or which act as lubricants. It has proven advant-ageous for a number of applications to maintain an air gap between the outlet surface of the extrustion tool, 25 i.e. the outlet surface, for example, of a corresponding ~ f~
-thread noz~le and the surface of thc bath. By varyiIlg the air gap, it is possible to influence the structure of the thread o'btained, and in particular, it surface.
It has been f~lnd that the numberof open pores can be reduced by extending the air gap and can be increased by shortening it. The diameter o~ the pores also decreases as the air gap increases, The air gap can be heated, preferably to a temperature above the critical temperatureof the extruded mixture.
The air gap is generally at least 1 mm wide and can assume a length of up to about 10 cm depending on the operating conditions. It is important to prevent any disintegration or at least any noticeable disintegration into two liquid phases in the air gap before entry into the bath . As stated, this can be c~ntrolled by the shortness of the interval or by heating, but it is however also possible to counteract premature disintegration by increasing outlet speed at the nozzle.
In a particular embodiment of the method according to the invention, however, the homogeneous mixture is extruded directly into the bath, open pores having a maximum diameter being formed at the surface.
;Owing to their particular surface structure and the structure inside the threads, they are also eminently 3(~9 suitable as a substrate for certain substances. Thus, tlle threads can be impregnated with anti-static agents which are already in use as an iner-t liquid during the spinning process or the agent can be introduced in-to the thread strueture only subsequently by treating it9 for example, by impregnation, after production of the thread.
In this way, it is possible to obtain compositions having a long term effect, which slowly give off the absorbed active ingredient again. Conversely, the threads can also be used for the adsorption of substances.
The threads can also be used in a wide variety of textile applications, for example,~they can be processed into sheets, such as, woven or non-woven fabrics~
Another field of applieation is insulation, such as, for example, thermal insulation and sound-proofing.
The pores in the threads aceording to the invention can be of various shapes. Thus, they can be rounded or elongated and can be interconneeted, in some cases by small conneeting passages and in other cases due to them passing directly into eaeh other. Even in threads which have been obtained from mixtures having a polymer content of about 30%~ the poly~er can be the matrix, in whieh the individual pores are distrubted and form fairly discrete, but intereonneeted eavities. Conversely, it is also possible to produce structures in which the cavities ~ 15-form the ~atrix as wi-th non-woven fabrics and the poly-mer substance is arranged in a almost fibrillar con-figuration. The transitions between these two structures are not strongly defined and are thus partly mixed. The 5 structural forms can also be influenced by other oper-ating parameters such as, for example, take-off speed, cooling speed, draft below the nazzle.
An apparatus which is suitable forthe production of the threads according to the invention is illustrated in more detail in the accompanying drawing.
The numeral 1 refers to a container which can be thermostatically controlled, from which inert liquid is metered by means of a double piston pump 3 and another heater 4 into the mixer 8. The heater 2 provides preliminary heating. Polypropylene passes from the chip container 5 via an ex~ruder 6 and a gear pump 7 into the mixer 8, from which a nozzle 10 is supplied via a gear p~p 9. The issuing mass passes via an air gap into a spinning tube 12 which is provided with a spinning funnel 11 and is provided with inert liquid via a level container 13 from the main reservoir 14. The spinning tube has a curve at its lower end and the threads are - ~ conveyed to a winder 16 af-ter leaving a bath 15.
;The invention is illustrated in more detail by the following Example:
ll~V~309 Polypropylene chips are melted in an~extruder and metered into a pin mixer using a gear plmlp Liquid NN-bis-(2-hydroxyethyl)-hexadcylamine at a temperature of 40~ is simultaneously pumped from a storage container which can be heated, via a double piston pump into an electrically heated heater and is conveyed from there into the mixer at a temperature o-f about 150C. A pin ~xer is used a mixer.
After homogenisation of the two components, the melt is pressed through a spinneret by a metering pump and extruded into a spinning bath which consists of pure NN-bis-(2-hydroxyethyl)-hexadecylamine and has a temp-erature of 50C.
Once the thread has passed through the spinning bath, having a length of 50 cm, the thread obtained is extracted over ethanol and dried. A porous thread having excellent properties and a particularly good surface structure is obtained.
.~
It has already been known for a long time to produce porous threads. In many cases, these threads are designated as foam threads.
A large number of methods for obtaining threads having a porous structure is already known. Thus, East German Patent No. 103 375 describes a method in which a pol~vmer melt consisting of one or more components, preferably components which are incompatible with each other, is extruded with the additon of physical and/or chemical blowing agents through one or more rows of holes in spinnerets with round, round and hollow or profiled and hollow spinneret holes. These threads can be de-posited so as to form non-woven fabrics by suitable processing.
The threads with cavities known hitherto have various disadvantages, ~d several methods thus lead to threads which only have cavities in the interior and which have a completely closed surface or possible a surface having slight permeability. Other threads whose surfaces exhibit opening are, however, produced with a surface which lS rough, thus rendering them unsuitable for many uses.
There is thus a need for improved methods of "'`~ ~
productio~ l partioular to provide methods by which the spiIming composition to be extruded can be produced simply and which operate without complicated spinning baths. There is also a need for improved threads which are porous, having openings on their surface but neverthe-less have a smooth surface structure, An object of the invention is therefore to provide a method by which polymers can be shaped in a simple manner in an extrudable spinning composition and which simultaneously allows extrusion and allows the extruded material to be solidified without complicated spinning techniques and spinning baths having to be used.
Another object of the invention is to provide a method which ailows threads having adjustable porosity to be obtained merely by varying the operating parameters.
An object of the invention is also to provide porous threads which have a desirable open surface relative to the known foam threads. A further object of the invention is to provide threads which can be used in the textile field as well as in industrial and other spheres and which are particularly suitable as a support substrate for certain active ingredients.
According to the presen-t invention there is provided a method of producing porous threads in which a homogeneous mixture is extruded, the homogeneous mixture comprisiIlg at least two oomponents, of which one oompon-ent is a fusible polymer and the other component is a liquid which is inert towards the polymer as ~erein-after defined), the two components forming a binary system, which llas, in the liquid sta-te, a region in which the components are completely miscible and a rsgion in which there is a discontinuity in, the homogeneous mixture being extruded at a temperature above the critical temperature of the binary system in to a bath containing said other inert liquid component of the homogeneous mixture and which is at a temperature below said critical temperature, and the thread structure so formed is solidified.
The fibre structure formed can be washed out using a solvent after solidification, acetone being particularly useful for this purpose.
It is advantageous if an air gap is included between the outlet surface of the extrusion tool and the surface of the bath. This air gap can be heated.
It is also possible to extrude the homogeneous mixture directly into the bath.
A bath having a staggered temperature is used in $ a particular embodiment of the me-thod according to the invention. In that embodimen~ the bath can comprise one or more parts which have a temperature gradient in such a way tha-t the temperature increases continuously _5 from the begining of the spinning bath to th~ outlet end. `
It is also possible to use two or more separate baths which each have a different temperature.
It has proved advantageous if the bath is at a temperature which i8 at least 100C lower than the critical temperature of the binary composition used.
Homogeneous mixtures of from 10 to 90/0 by weight of poly-mer and from 90 to 10 ~ by weight of inert liquid can be extruded according to the invention.
The homogeneous mixture can also initially be extruded into a spinning tube connected upstream of the bath and filledwith the bath liquid.
Polypropylene is preferably used as polymer and NN-bis-(2-hydro~yethyl)-hexadecylamine is preferably used as inert liquid.
The two components, namely the molten polymer and the inert liquid, are preferably mixed continuously prior to extrusion, in which process it is advantageous for mixing only to ta~e place immediately prior to e~trusion.
The mixture can still be homogenised prior to extrusion.
A pin mixer is particularly suitable for mixing purposes.
- ~ According to another aspect of the present invention there is provided porous threads comprisi~g a s~thetic polymer having from 10 to 90~0 by volume of pores which COmmUniGate with each other and a smooth surface structure haviIlg open pores, wherein the proporSion of openings in the surfnce thereof amounts to from 10 to 90%, Preferably the apparent density of the threads lies between about 10 to 90~ of the actual density of the polymer used.
The threads can be used as a support substrate, io e.
the threads can be impregnated with specific substances which are given off at a subsequent moment. They can also be used as insulating material.
It is possible to use, in particular, fibre-forming macromolecular substances which are known per se, particularly synthetic polymers which are obtained, for example, by polymerisation, polyaddition or polyconden-sation, for carrying out the method according to theinvention and for the production of threads according to the invention. The polymer must be fusible, i.e., it must be able to pass into the liquid state without decomposing and form a binary system with a liquid which is inert towards it, which system having a range of com-plete miscibility in the liquid state and also a range in the liquid state with mixing gaps.
Systems of this type have a phase diagram for the liquid state of, for example, the type shown for the aniline/hexane system on page 724 of the Text Book of physical Chemis-try by S. Glasstone, Macmillian and Co Ltd, St, ~artins~ Street, London, 1953. Thisdiagram indicates complete miscibility for the two components above -the arched curve. Two liquid phases are in equilibriu~ with each other beneath the curve~
It is not absolutely essential for carrying out the invention for each of the two components in thetwo-phase range still to exhibit considerably solubility relative to the other components, as is the case in the -above-mentioned graph. In many cases, it is sufficient to have marginal solubility in the liquid two-phase domain. It is however important for the two components in the liquid state to form two liquid phases next to each other. In this respect, the systems which can be used according to the invention differ from those systems in which the dissolved polymer is precipitated directly as a solid when the temperature is lower without firstly passing through the liquid state during the cooling treatment.
Conventional fusible polymers can be used within the scope of the invention, such as, for example the polymers obtained by polymerisation, such as, polyethylene, i polypropylene, polyvinylchloride, polyacrylates, poly caprolactam as well as corresponding copoly~ers among others; polycondensation polymers, such as, polyethylene terephthalate, polybutylene terephthalate, polyamide ~),6 polyphenylene oxide, and poly addi-tion polymers, such as, polyurethanes and polyureas.
All tho6e liquids which form a binary system of the above-mentioned type with the polymer in the liquid state are basically suitable as inert liquid within the scope of the invention. By the phrase "inert towards the polymer" as used herein, is meant that the liquid does not cause considerable decomposition of the polymer within a short period or does not react with the polymer itself.
Although the above-mentioned phase diagram of the state of the aniline/hexane sysb~mshows the ratios for a binary mixture which consists of two uniform substances which are themselves essentially pure, the term binary system should not be appled strictly, in the context of the invention, to mixtures of only two pure uniform substances. The average skilled man knows that a polymer substance is composed of a plurality of molecules of differing molecular weight, and these polymers with a corresponding molecular weight distribution are there-fore to be considered within the scope of the invention as one component, and the same applies to mixed poly-- ~ mers. Under certain circumstances, polymer mixtures can even behave as a uniform component and form a single phase mixture with an inert solvent and separate only into two liquid phases below a critical -temperature. It is preferable, however, to use only one polymer~ The liquid need not necessarily be completely pure and represent a completely uniform substance~ In many cases, it does not matter if relatively small quantities of impurities and possibly also proportions of homo-geneous c~mpounds of the type which are necessitated by industrial production are added.
In order to carry out the method in practice, a homo~
geneous mixture is produced from the two components at the required temperatures~ This can be effected by - mixing the inert liquids with the comminuted polymer heating it to suitable temperatures, ensuring that mixing is sufficiently thorough.
Another suitable method involves bringing the two components to the required temperature separately and mixing the two components together continuously in the desired proportion just before extrusion. This mixing can be carried out in a pin mixer which is advantageously arranged between themetering pumps for the individual components and the spinning pump. Subsequent homogen-isation may be advisable.
- ~ In many cases, it is advisable to aerate the homogeneous mixture by applying a suitable vacuum before extrusion.
The ratio of the polymer to inert liquid in the spinlling compositioIl can be varied within wide limits.
The interllal pore volume and also the surface texture as well as the number of open pores on the surl'aces of the hollow threads obtained, can be controlled to a large èxtent by adjusting the ratio of polymer to inert liquid.
Porous threads which are suitable for a very wide range of applications can thus be obtained.
It is generally sufficient for the temperature of the homogeneous mixture prior to extrusion to lie only a few degrees above the critical temperature or above the disintegration temperature, depending on the respective composition.
Interesting effects with regard to the texture of the threads obtained can however also be achieved by increasing the difference between the temperature of the homogeneous mixture to be e~truded and the critical temperature.
The homogeneous spinning composition is then extruded into a bath containing the inert liquid of the extruded component mixture and having a temperature below the critical temperature. The bath preferably consists completely or mainly oY the inert liquid which is also - $ present in the extruded mixture. The temperature of the bath lies below the critical temperature of the mixture used, i.e. below the temperature above which the two components can be mixed together completely homo-V3~)9 genevusly. The teloperature of the bath preferably liesat least 100C below the critical temperature O:e -the mixture used.
The temperature can also be sufficiently low to progress in the range in which a solid phase occurs according to the phase diagram relatingto the binary system.
Once the temperature of the bath is sufficiently high that it continues progressing in the liquid two phase region, then it is necessary to solidify the thread structure formed as soon as possible, which can be ef-fected by reducing the temperature accordingly after a certain interval inside the bath.
It is imp~rtant for the extruded mixture still to be single-phase before it enters the bath, i.e. for substantially no further disintegration into two phases~
to take place.
It has proven advantageous to arrange in front, upstream end of the bath in certain cases a spinning tube which is also filled with the bath liquid and the end of which is submerged in the spinning bath. The spin-ning tube can have a conventional spinning funnel at its inlet opening, and the tube can be curved at its lower end ~n order to make it easier to take off the thread through the bath.
V;~f~9 _12--The spinning tube can be filled by means of a level container surrounding the spinning tube as a result of overflow into the spimIing tube. In order to lill the spinning tube completely and to maintain the level in 5 it, it is necessary to supply more bath liquid to this level container from a main reservoir than flows out through the spinning tube. The excess bath liquid can be recirculated via a secondoverflow on the level cont-ainer into the main reservoir. The main reservoir and 10 level container can be controlled thermostatically.
Once it has passed from the spinning bath, the thread can be washed out with a suitable extraction agent.
A number of solvents such as, for example, acetone, cyclo--hexanone and ethanol as well as mixtures of these liquids, 15 are suitable for extraction~
In some cases, it is not necessary to wash out the thread, particularly when the actual inert liquid s used is to impart to the thread extra properties which are designed for its subsequent application or is even to 20 perform a function. Thus, for example, it is possible to use liquids which exert an anti-static effect on the thread or which act as lubricants. It has proven advant-ageous for a number of applications to maintain an air gap between the outlet surface of the extrustion tool, 25 i.e. the outlet surface, for example, of a corresponding ~ f~
-thread noz~le and the surface of thc bath. By varyiIlg the air gap, it is possible to influence the structure of the thread o'btained, and in particular, it surface.
It has been f~lnd that the numberof open pores can be reduced by extending the air gap and can be increased by shortening it. The diameter o~ the pores also decreases as the air gap increases, The air gap can be heated, preferably to a temperature above the critical temperatureof the extruded mixture.
The air gap is generally at least 1 mm wide and can assume a length of up to about 10 cm depending on the operating conditions. It is important to prevent any disintegration or at least any noticeable disintegration into two liquid phases in the air gap before entry into the bath . As stated, this can be c~ntrolled by the shortness of the interval or by heating, but it is however also possible to counteract premature disintegration by increasing outlet speed at the nozzle.
In a particular embodiment of the method according to the invention, however, the homogeneous mixture is extruded directly into the bath, open pores having a maximum diameter being formed at the surface.
;Owing to their particular surface structure and the structure inside the threads, they are also eminently 3(~9 suitable as a substrate for certain substances. Thus, tlle threads can be impregnated with anti-static agents which are already in use as an iner-t liquid during the spinning process or the agent can be introduced in-to the thread strueture only subsequently by treating it9 for example, by impregnation, after production of the thread.
In this way, it is possible to obtain compositions having a long term effect, which slowly give off the absorbed active ingredient again. Conversely, the threads can also be used for the adsorption of substances.
The threads can also be used in a wide variety of textile applications, for example,~they can be processed into sheets, such as, woven or non-woven fabrics~
Another field of applieation is insulation, such as, for example, thermal insulation and sound-proofing.
The pores in the threads aceording to the invention can be of various shapes. Thus, they can be rounded or elongated and can be interconneeted, in some cases by small conneeting passages and in other cases due to them passing directly into eaeh other. Even in threads which have been obtained from mixtures having a polymer content of about 30%~ the poly~er can be the matrix, in whieh the individual pores are distrubted and form fairly discrete, but intereonneeted eavities. Conversely, it is also possible to produce structures in which the cavities ~ 15-form the ~atrix as wi-th non-woven fabrics and the poly-mer substance is arranged in a almost fibrillar con-figuration. The transitions between these two structures are not strongly defined and are thus partly mixed. The 5 structural forms can also be influenced by other oper-ating parameters such as, for example, take-off speed, cooling speed, draft below the nazzle.
An apparatus which is suitable forthe production of the threads according to the invention is illustrated in more detail in the accompanying drawing.
The numeral 1 refers to a container which can be thermostatically controlled, from which inert liquid is metered by means of a double piston pump 3 and another heater 4 into the mixer 8. The heater 2 provides preliminary heating. Polypropylene passes from the chip container 5 via an ex~ruder 6 and a gear pump 7 into the mixer 8, from which a nozzle 10 is supplied via a gear p~p 9. The issuing mass passes via an air gap into a spinning tube 12 which is provided with a spinning funnel 11 and is provided with inert liquid via a level container 13 from the main reservoir 14. The spinning tube has a curve at its lower end and the threads are - ~ conveyed to a winder 16 af-ter leaving a bath 15.
;The invention is illustrated in more detail by the following Example:
ll~V~309 Polypropylene chips are melted in an~extruder and metered into a pin mixer using a gear plmlp Liquid NN-bis-(2-hydroxyethyl)-hexadcylamine at a temperature of 40~ is simultaneously pumped from a storage container which can be heated, via a double piston pump into an electrically heated heater and is conveyed from there into the mixer at a temperature o-f about 150C. A pin ~xer is used a mixer.
After homogenisation of the two components, the melt is pressed through a spinneret by a metering pump and extruded into a spinning bath which consists of pure NN-bis-(2-hydroxyethyl)-hexadecylamine and has a temp-erature of 50C.
Once the thread has passed through the spinning bath, having a length of 50 cm, the thread obtained is extracted over ethanol and dried. A porous thread having excellent properties and a particularly good surface structure is obtained.
.~
Claims (21)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of producing porous threads, in which a homogeneous mixture is extruded, the homogeneous mixture comprising at least two components, of which one component is a fusible polymer and the other component is a liquid which is inert towards said fusible polymer, the two components forming a binary system which has in the liquid state a region in which the components are completely miscible and a region in which there is a discontinuity in mixing, said homogeneous mixture being extruded at a temperature above the critical temperature of the binary system into a bath containing said other, inert liquid component of the homogeneous mixture and which is at a temperature below said critical temperature, and the thread structure so formed is solidified.
2. A method according to Claim 1, wherein the thread structure formed is washed-out with a solvent after solidification.
3. A method according to Claim 2, wherein said solvent comprises acetone.
4. A method according to Claim 1, wherein the mixture is extruded by means of an extrusion tool, an air gap existing between the outlet surface of the extrusion tool and the surface of the bath.
5. A method according to Claim 4, wherein the air gap is heated.
6. A method according to Claim 1, wherein the homogeneous mixture is extruded directly into the bath.
7. A method according to Claim 1, wherein the temperature of the bath lies at least 100°C below the critical temperature of the binary system.
8. A method according to Claim 1, 4 or 6 wherein the homogeneous mixture is initially extruded into a spinning tube arranged upstream of the bath and filled with the inert liquid in the bath.
9. A method according to Claim 1, wherein said fusible polymer comprises polypropylene.
10. A method according to Claim 1, wherein the inert liquid comprises NN-bis-(2-hydroxyethyl)-hexadecylamine.
11. A method according to Claim 1 or 7, wherein the temperature in the bath is staggered.
12. A method according to Claim 1, 9 or 10 wherein the homogeneous mixture consists of 10 to 90% by weight of polymer and 90 to 10%
by weight inert liquid.
by weight inert liquid.
13. A method according to Claim 1, wherein the two components are mixed continuously before extrusion.
14. A method according to Claim 13, wherein a pin mixer is used for mixing purposes.
15. Porous non-foamed threads comprising a synthetic polymer having from 10 to 90% by volume of pores which communicate with each other and a smooth surface structure having open pores, wherein the proportion of openings in the surface thereof amounts to from 10 to 90%.
16. Porous non-foamed threads according to Claim 15, having an apparent density of from 10 to 90% of the actual density of the polymer.
17. A support substrate comprising porous non-foamed threads according to Claim 15 or 16.
18. An insulating material comprising porous non-foamed threads according to Claim 15 or 16.
19. Porous threads as defined in Claim 15 or 16 whenever produced by a method in accordance with Claim 1.
20. Porous threads as defined in Claim 15 or 16 whenever produced by a method in accordance with Claim 9.
21. Porous threads as defined in Claim 15 or 16 whenever produced by a method in accordance with Claim 10.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE2833568A DE2833568C2 (en) | 1978-07-31 | 1978-07-31 | Porous threads |
| DEP2833568.4-26 | 1978-07-31 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1140309A true CA1140309A (en) | 1983-02-01 |
Family
ID=6045861
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000332832A Expired CA1140309A (en) | 1978-07-31 | 1979-07-30 | Filaments with porous surface |
Country Status (11)
| Country | Link |
|---|---|
| JP (1) | JPS5522097A (en) |
| AT (1) | AT372411B (en) |
| BE (1) | BE877930A (en) |
| BR (1) | BR7904887A (en) |
| CA (1) | CA1140309A (en) |
| CH (1) | CH637795B (en) |
| DE (1) | DE2833568C2 (en) |
| ES (1) | ES482966A1 (en) |
| FR (1) | FR2432564A1 (en) |
| GB (1) | GB2026935B (en) |
| IT (1) | IT1118170B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58159739A (en) * | 1982-03-19 | 1983-09-22 | オリンパス光学工業株式会社 | Laser operation apparatus |
| JPS6052613A (en) * | 1983-08-30 | 1985-03-25 | Toyobo Co Ltd | High-tensile and high-modulus polyethylene fiber |
| JP2543360B2 (en) * | 1987-04-06 | 1996-10-16 | トヨタ自動車株式会社 | Porous polypropylene fiber |
| JPH0636809Y2 (en) * | 1988-10-11 | 1994-09-28 | 株式会社モリタ製作所 | Dental laser switching device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL128691C (en) * | 1961-02-10 | |||
| US3513110A (en) * | 1965-07-26 | 1970-05-19 | Celanese Corp | Open-celled low density filamentary material |
| DE2550080B2 (en) * | 1975-11-07 | 1978-03-09 | Akzo Gmbh, 5600 Wuppertal | Process for the production of filaments with discontinuous voids |
| DE2554124C3 (en) * | 1975-12-02 | 1986-07-10 | Bayer Ag, 5090 Leverkusen | Process for the production of hydrophilic fibers and threads from acrylonitrile polymers |
-
1978
- 1978-07-31 DE DE2833568A patent/DE2833568C2/en not_active Expired
-
1979
- 1979-07-18 CH CH662879A patent/CH637795B/en unknown
- 1979-07-19 IT IT49806/79A patent/IT1118170B/en active
- 1979-07-23 AT AT0506279A patent/AT372411B/en not_active IP Right Cessation
- 1979-07-27 BE BE0/196482A patent/BE877930A/en not_active IP Right Cessation
- 1979-07-30 BR BR7904887A patent/BR7904887A/en unknown
- 1979-07-30 ES ES482966A patent/ES482966A1/en not_active Expired
- 1979-07-30 CA CA000332832A patent/CA1140309A/en not_active Expired
- 1979-07-30 FR FR7919614A patent/FR2432564A1/en active Granted
- 1979-07-31 GB GB7926710A patent/GB2026935B/en not_active Expired
- 1979-07-31 JP JP9690479A patent/JPS5522097A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| DE2833568A1 (en) | 1980-02-21 |
| JPS5522097A (en) | 1980-02-16 |
| DE2833568C2 (en) | 1987-02-12 |
| CH637795GA3 (en) | 1983-08-31 |
| AT372411B (en) | 1983-10-10 |
| FR2432564B1 (en) | 1982-12-10 |
| ATA506279A (en) | 1983-02-15 |
| ES482966A1 (en) | 1980-05-16 |
| IT1118170B (en) | 1986-02-24 |
| CH637795B (en) | |
| BR7904887A (en) | 1980-04-22 |
| BE877930A (en) | 1979-11-16 |
| IT7949806A0 (en) | 1979-07-19 |
| GB2026935A (en) | 1980-02-13 |
| FR2432564A1 (en) | 1980-02-29 |
| GB2026935B (en) | 1982-09-08 |
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