CA1040372A - Method of manufacturing polyoxymethylene filaments - Google Patents
Method of manufacturing polyoxymethylene filamentsInfo
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- CA1040372A CA1040372A CA206,887A CA206887A CA1040372A CA 1040372 A CA1040372 A CA 1040372A CA 206887 A CA206887 A CA 206887A CA 1040372 A CA1040372 A CA 1040372A
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Abstract
ABSTRACT OF THE DISCLOSURE
A method of manufacturing polymethylene filaments, wherein polyoxymethylene having the molecular weight from 30,000 to 100,000 and containing stabilizing additives in a quantity from 0.1 to 3.0 per cent of the weight of the poly-oxymethylene is subjected to thermal treatment at a temperature from 100°C to 150°C and pressure from 1 to 100 mm mercury to attain constant weight. The thermally treated polyoxymethylene is melted at a temperature from 170°C to 230°C, whereafter the melt is forced through the orifices of an extrusion nozzle. The jets of the melt, leaving the orifices of the extrusion nozzle, are cooled to a temperature from 70°C to 169°C. After the cooling the obtained filaments are drawn at a temperature from 120°C to 165°C to a length exceeding from 7 to 14 times the initial length. The disclosed method offers a simple technology of producing filaments as strong as 100 grams per tex. To produce low-shrinkage fibre (i.e. with a shrinkage rate from 0 to 5 per cent at 150°C) the drawn filaments are thermally treated at a temperature exceeding that of the drawing by 2°C to 50°C, the filaments being maintained under tension. Alternatively, the drawn filaments may be first tensioned and then thermally treated.
A method of manufacturing polymethylene filaments, wherein polyoxymethylene having the molecular weight from 30,000 to 100,000 and containing stabilizing additives in a quantity from 0.1 to 3.0 per cent of the weight of the poly-oxymethylene is subjected to thermal treatment at a temperature from 100°C to 150°C and pressure from 1 to 100 mm mercury to attain constant weight. The thermally treated polyoxymethylene is melted at a temperature from 170°C to 230°C, whereafter the melt is forced through the orifices of an extrusion nozzle. The jets of the melt, leaving the orifices of the extrusion nozzle, are cooled to a temperature from 70°C to 169°C. After the cooling the obtained filaments are drawn at a temperature from 120°C to 165°C to a length exceeding from 7 to 14 times the initial length. The disclosed method offers a simple technology of producing filaments as strong as 100 grams per tex. To produce low-shrinkage fibre (i.e. with a shrinkage rate from 0 to 5 per cent at 150°C) the drawn filaments are thermally treated at a temperature exceeding that of the drawing by 2°C to 50°C, the filaments being maintained under tension. Alternatively, the drawn filaments may be first tensioned and then thermally treated.
Description
~04037Z
The present invention relates to the methods of manufacturing polyoxymethylene filaments, and, more particular-ly, of high-strength low-shrinkage polyoxymethylene filaments.
These filaments can be widely used in the production of fishing nets and tawls, of filtering cloth, of enyineering rubber articles, cord, etc., since they offer a whole series of valuable properties. Thus, among their properties is the one of being hydrophobic or water-repellent, which means that their strength is unaffected by moisture, they are proof to the action of alkali, as well as of numerous organic solvents at a temperature up to 100C, they are likewise proof to the action of sea water and are biologically stable. Polyoxymethyl-ene filaments also offer high tensile strength, resistance to rubbing, fatigue strength and elasticity. .
Furthermore, polyoxymethylene filaments and yarn can be widely used in the production of numerous textile articles, , e.g. in the form of texturized or bulk yarn.
; There already exists a number of methods of manufact~-,:~
ing polyoxymethylene filaments from melted polyoxymethylene by moulding a ~ilament with .~ubsequent drawing.
The high viscosity of the melt and the high crystalliza-tion rate of polyoxymethylene are reflected in the specific features of its processing into filaments. The relatively low temperature viscosity factor of the melt and the relatively low thermal stability of the melt of polyoxymethylene would not permit to considerably reduce the viscosity of the melt by in-creasing the temperature of the melt. Particular difficulties i are encountered at processing of polyoxymethylene with a high molecular weight, which is the one generally used for manufactur-ing polyoxymethylene filaments with high physical and mechanical properties, such as elasticity, fatigue strength, etc. It is this high viscosity of the melt of polyoxymethylene, particularly, ~,~ .
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of polyoxymethylene with a high molecular weight, which dooms the rate of extrusion of the filaments to be substantially lower than that of extrusion of filaments of other materials, usually attained in the art of making man-made fibre.
There is known a method of manufacturing polyoxy-methylene filaments, wherein, in order to step up the extruding speed (and, consequent'y, the winding speed) there is effected "cooling" of the jets of the melt, leaving the orifices of the extrusion nozzle, at a temperature from 170C to 240C (see ,~ 10 Japanese Patent No. 3486, issued March 1, 1966, inventors Hajanamy Hirosy, Inoue Takie~y, et al, Cl. 42D22). From the described examples of this method it can be seen that raising the temperature of the air in the vicinity of the extrusion nozzle from normal to 190C enables one to step up the extruding speed from 160 m/min to 670 m/min. However, the ratio of sub-sequent drawing of the filament thus obtained at a temperature ~ of 150C does not exceed 7:1, and, consequently, the strength q of this filament is but 67.5 grams per tex with elongation at rupture about 20 per cent There is known another method of manufacturing poly-oxymethylene filaments from melted stabilized homo- and co-polymers of formaldehyde or else of its cyclic trimer - trioxane -with cyclic esters, e g. ethylene oxide, 1,3 dioxolane, etc.
~see British Patent No. 995,848, Cl. D 01 f, D 06 m, C 08 g).
~ Stabilizing additives are included in a quantity, for example, ;; of 0.1 to 3.0 per cent of the weight of the polymer. To reduce ,.!
the viscosity of the melt there is sometimes added into the stabilized polymer a certain quantity of a plastifier. To mould polyoxymethylene filaments, the said homo- or co-polymers are subjected to melting at a temperature from 170C to 230~C and at the same temperature the melted poly~er is forced through the orifices of an extrusion nozzle. The jets of the melt, ~ ,''
The present invention relates to the methods of manufacturing polyoxymethylene filaments, and, more particular-ly, of high-strength low-shrinkage polyoxymethylene filaments.
These filaments can be widely used in the production of fishing nets and tawls, of filtering cloth, of enyineering rubber articles, cord, etc., since they offer a whole series of valuable properties. Thus, among their properties is the one of being hydrophobic or water-repellent, which means that their strength is unaffected by moisture, they are proof to the action of alkali, as well as of numerous organic solvents at a temperature up to 100C, they are likewise proof to the action of sea water and are biologically stable. Polyoxymethyl-ene filaments also offer high tensile strength, resistance to rubbing, fatigue strength and elasticity. .
Furthermore, polyoxymethylene filaments and yarn can be widely used in the production of numerous textile articles, , e.g. in the form of texturized or bulk yarn.
; There already exists a number of methods of manufact~-,:~
ing polyoxymethylene filaments from melted polyoxymethylene by moulding a ~ilament with .~ubsequent drawing.
The high viscosity of the melt and the high crystalliza-tion rate of polyoxymethylene are reflected in the specific features of its processing into filaments. The relatively low temperature viscosity factor of the melt and the relatively low thermal stability of the melt of polyoxymethylene would not permit to considerably reduce the viscosity of the melt by in-creasing the temperature of the melt. Particular difficulties i are encountered at processing of polyoxymethylene with a high molecular weight, which is the one generally used for manufactur-ing polyoxymethylene filaments with high physical and mechanical properties, such as elasticity, fatigue strength, etc. It is this high viscosity of the melt of polyoxymethylene, particularly, ~,~ .
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... ..
. . . . . - .
... . . . . . .... . .. .
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of polyoxymethylene with a high molecular weight, which dooms the rate of extrusion of the filaments to be substantially lower than that of extrusion of filaments of other materials, usually attained in the art of making man-made fibre.
There is known a method of manufacturing polyoxy-methylene filaments, wherein, in order to step up the extruding speed (and, consequent'y, the winding speed) there is effected "cooling" of the jets of the melt, leaving the orifices of the extrusion nozzle, at a temperature from 170C to 240C (see ,~ 10 Japanese Patent No. 3486, issued March 1, 1966, inventors Hajanamy Hirosy, Inoue Takie~y, et al, Cl. 42D22). From the described examples of this method it can be seen that raising the temperature of the air in the vicinity of the extrusion nozzle from normal to 190C enables one to step up the extruding speed from 160 m/min to 670 m/min. However, the ratio of sub-sequent drawing of the filament thus obtained at a temperature ~ of 150C does not exceed 7:1, and, consequently, the strength q of this filament is but 67.5 grams per tex with elongation at rupture about 20 per cent There is known another method of manufacturing poly-oxymethylene filaments from melted stabilized homo- and co-polymers of formaldehyde or else of its cyclic trimer - trioxane -with cyclic esters, e g. ethylene oxide, 1,3 dioxolane, etc.
~see British Patent No. 995,848, Cl. D 01 f, D 06 m, C 08 g).
~ Stabilizing additives are included in a quantity, for example, ;; of 0.1 to 3.0 per cent of the weight of the polymer. To reduce ,.!
the viscosity of the melt there is sometimes added into the stabilized polymer a certain quantity of a plastifier. To mould polyoxymethylene filaments, the said homo- or co-polymers are subjected to melting at a temperature from 170C to 230~C and at the same temperature the melted poly~er is forced through the orifices of an extrusion nozzle. The jets of the melt, ~ ,''
- 2 -104(~372 leaving the orifice, are cooled in the ambient air. After the cooling, the moulded filament is subjected to drawing. sy drawing the moulded filament at a rate of 10.2 m/min and temperature from 120~C to 150C, e.g. 134C, the dra~t, for example, being 9.05 : 1, there is obtained a filament with the strength not in excess of 54.9 grams per tex. In order to step up the strength of the filament, it is subjected to a repeated drawing at a rate of 10.5 m/min at a temperature from 150C to 160C, the draft being from 1.05 : 1 to 2 : 1. As a result, the strength is increased to 89.1 grams per tex.
The use of plastifiers in certain cases involves the necessity of resorting to additional labour-consuming operations in removing the plastifier. On the other hand, the presen~e of the plastifier in a final filamen~ considerably affects its physical and mechanical properties.
To obtain filaments of a sufficiently high strength by the last-described method, the moulded filament is d~awrl not in a single stag~, but in two stages, which also complicates thc technology. Besides, this drawing is effected at a relatively low 5peed, which lowers the productivity of the equipment.
Furthermore, the cooling of the jets leaving the nozzle in the ambient air would not permit to mould the filaments at high speeds, which becomes particularly apparent when polyoxy-methylene of a high molecular weight is processed.
It is an object of the present invention to develop a method of manufacturing polyoxymethylene filaments, which should provide for obtaining polyoxymethylene filaments with high physical and mechanical properties.
It is another object of the present invention to simplify the technology of the manufacturing process.
With these and other objects in vie~, the present in-vention resides in a method of manufacturing polyoxymethylene
The use of plastifiers in certain cases involves the necessity of resorting to additional labour-consuming operations in removing the plastifier. On the other hand, the presen~e of the plastifier in a final filamen~ considerably affects its physical and mechanical properties.
To obtain filaments of a sufficiently high strength by the last-described method, the moulded filament is d~awrl not in a single stag~, but in two stages, which also complicates thc technology. Besides, this drawing is effected at a relatively low 5peed, which lowers the productivity of the equipment.
Furthermore, the cooling of the jets leaving the nozzle in the ambient air would not permit to mould the filaments at high speeds, which becomes particularly apparent when polyoxy-methylene of a high molecular weight is processed.
It is an object of the present invention to develop a method of manufacturing polyoxymethylene filaments, which should provide for obtaining polyoxymethylene filaments with high physical and mechanical properties.
It is another object of the present invention to simplify the technology of the manufacturing process.
With these and other objects in vie~, the present in-vention resides in a method of manufacturing polyoxymethylene
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10~372 filaments, wherein polyoxymethylene having a molecular weight within a range from 30,000 to 100,000 and including stabilizing additives in a quantity from 0.1 to 3.0 per cent of the weight of said polyoxymethylene is thermall~ treated at a temperature within a range from 100C to 150C and pressure from 1 to 100 mmHg to a constant weight; said thermally treated polyoxymethylen~?
is subjected to meltin~ at a temperature within a range from 170C
to 230C, the thus obtained melt is forced through the orifices of an extrusion nozzle; the jets of said melt, leaving the orifices of the extrusion nozzle are cooled to a temperature within a range from 70C to 169~C; after said cooling the moulded filaments obtained are subjected to drawing at a tempera-ture within a range from 120C to 165C to a length exceeding the : initial length from seven to fourteen times.
For the filament-forming polyoxymethylene there are used either homo- or co-polymers of formaldehyde or else of its cyclic trimer - trioxane - with cyclic esters of a yeneral formula, for example CH2 - O
CH2 - ( OCH2 ) n where "n" is an integer within a range from 0 to 2. The weight content of the second co-monomer in the co-polymer may vary within a range from 0.5 to 10 per cent, depe-~ding on the destina-tion of the'filaments to be manufactured.
The molecular weight (Mw) of the polyoxymethylene used may vary from 30,000 to 100,000 and is calculated from the formula: [~] = K.MW where [~] is the characteristic viscosity of solution of polyoxymethylene in dimethylformamide, measured at 150~C - 0.5C on Ostwald-Pinkevich viscosimeter, K equals 4.4
: ~ ', - . , :, .
10~372 filaments, wherein polyoxymethylene having a molecular weight within a range from 30,000 to 100,000 and including stabilizing additives in a quantity from 0.1 to 3.0 per cent of the weight of said polyoxymethylene is thermall~ treated at a temperature within a range from 100C to 150C and pressure from 1 to 100 mmHg to a constant weight; said thermally treated polyoxymethylen~?
is subjected to meltin~ at a temperature within a range from 170C
to 230C, the thus obtained melt is forced through the orifices of an extrusion nozzle; the jets of said melt, leaving the orifices of the extrusion nozzle are cooled to a temperature within a range from 70C to 169~C; after said cooling the moulded filaments obtained are subjected to drawing at a tempera-ture within a range from 120C to 165C to a length exceeding the : initial length from seven to fourteen times.
For the filament-forming polyoxymethylene there are used either homo- or co-polymers of formaldehyde or else of its cyclic trimer - trioxane - with cyclic esters of a yeneral formula, for example CH2 - O
CH2 - ( OCH2 ) n where "n" is an integer within a range from 0 to 2. The weight content of the second co-monomer in the co-polymer may vary within a range from 0.5 to 10 per cent, depe-~ding on the destina-tion of the'filaments to be manufactured.
The molecular weight (Mw) of the polyoxymethylene used may vary from 30,000 to 100,000 and is calculated from the formula: [~] = K.MW where [~] is the characteristic viscosity of solution of polyoxymethylene in dimethylformamide, measured at 150~C - 0.5C on Ostwald-Pinkevich viscosimeter, K equals 4.4
4.4 10 4 and ~ equals 0.66.
It is not advisable to use polyoxymethylene with a molecular weight below 30,000, since the strength of filaments produced from such a polymer is insufficient. On the other hand, ~ - 4 -.. ~ ', , .: ' , . , .
1041)372 when polyoxymethylene with a molecular weight in excess of 100,000 is used, there are encountered certain techn~logical , ~ .
difficulties on account of the high viscosity of the melt.
An increased content of the second co-monomer in the co-polymer leads to a lower melting point of the co-polymer, and, consequently, to a reduced thermal strength of the filament.
To step up the thermal stability of polyoxymethylene, , there are introduced thereinto stabilizing additives in a , quantity from 0.1 to 3.0 per cent of the weight of the mass of polyoxymethylene. For the stabilizers can be used, for instance, a system of two components including an antioxidant and an acceptor of formaldehyde. Among the antioxidants are such substances as bis-phenols, e.g. 2,2'-methylene bis-(4-methyl-6-tertiary butyl-phenol), 4,4'-butylidene bis-(6-tertiary-butyl-4-methyl-phenol), while among the acceptors are polyamides, polyurethanes, compositions containing tertiary amînes and i final amide groups, for example, dicyanamide ~cyanguanidine).
~ The properties of the filament are to a great extent ; dependent on the initial raw materials and the techno~ogical conditions of their manufacture.
Stabilized polyoxymethylene may contain up to 0.2 per cent by weight of equilibrium moisture (water). m e presence of the moisture (water) in the polymer adversely affects the moulding and drawing operations and the quality of the filaments.
An increased content of water leads to formation of hubhles of steam in the jets of the melt, leaving the orifices of the extrusion nozzle, which might result in breakage of the jets in the moulding operation, or else in breakage of the filament during subsequent drawing.
Under the herein disclosed conditions of thermal treatment of the initial mass of polyoxymethylene to a constant weight, i.e. at a temperature from 100C to 150C and pressure
It is not advisable to use polyoxymethylene with a molecular weight below 30,000, since the strength of filaments produced from such a polymer is insufficient. On the other hand, ~ - 4 -.. ~ ', , .: ' , . , .
1041)372 when polyoxymethylene with a molecular weight in excess of 100,000 is used, there are encountered certain techn~logical , ~ .
difficulties on account of the high viscosity of the melt.
An increased content of the second co-monomer in the co-polymer leads to a lower melting point of the co-polymer, and, consequently, to a reduced thermal strength of the filament.
To step up the thermal stability of polyoxymethylene, , there are introduced thereinto stabilizing additives in a , quantity from 0.1 to 3.0 per cent of the weight of the mass of polyoxymethylene. For the stabilizers can be used, for instance, a system of two components including an antioxidant and an acceptor of formaldehyde. Among the antioxidants are such substances as bis-phenols, e.g. 2,2'-methylene bis-(4-methyl-6-tertiary butyl-phenol), 4,4'-butylidene bis-(6-tertiary-butyl-4-methyl-phenol), while among the acceptors are polyamides, polyurethanes, compositions containing tertiary amînes and i final amide groups, for example, dicyanamide ~cyanguanidine).
~ The properties of the filament are to a great extent ; dependent on the initial raw materials and the techno~ogical conditions of their manufacture.
Stabilized polyoxymethylene may contain up to 0.2 per cent by weight of equilibrium moisture (water). m e presence of the moisture (water) in the polymer adversely affects the moulding and drawing operations and the quality of the filaments.
An increased content of water leads to formation of hubhles of steam in the jets of the melt, leaving the orifices of the extrusion nozzle, which might result in breakage of the jets in the moulding operation, or else in breakage of the filament during subsequent drawing.
Under the herein disclosed conditions of thermal treatment of the initial mass of polyoxymethylene to a constant weight, i.e. at a temperature from 100C to 150C and pressure
- 5 -'~
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;~!, ' ' ' ' ' ' ' . . ' ` ` , , from 1 to 100 mm mercury, it has been quite unexpectedly found that the loss of weight by the pol~,ler substantially exceeds the content therein of the equilibrium water. It has also been found that the strength of the filament produced from the poly-mer subjected to this thermal treatment is enhanced. In the process of thermal treatment water and other volatile compounds are removed from the polymer. Volatile components may comprise on th~ one hand, formaldehyde which remains in the mass (block) ~ ~o~o~
of polymer granules after gr~nul~ting lt at a polymer manufactur-ing plant, and, on the other hand, formaldehyde which breaksaway (separates) from the unstable portion of the macromolecules of polyoxymethylene while heating the latter. Besides, it is not altogether improbable that under the above conditions there ~; are partially removed the stabilizing additives which had been introduced earlier.
The presence of volatile components in the mass of polyoxymethylene likewise adversely affects the processing properties of the polymer, as it is the case with water. The presence of volatile components in the mass of polyoxy.nethylene, on the one hand, influences the permissible range of melting temperatures. With a high content of volatile substances there might appear in the melt an amount of bubbles which is greater, the higher this melting temperature. Consequently, with a reduced content of volatile substances in the mass of polyoxy-methylene, which is attained by the above described preliminary thermal treatment, it is fairly permissible to raise the melting temperature. The smaller the content of volatile substances in the melt of polyoxymethylene, the smaller is the degree of their evolution from the jets of the melt, leaving the orifices of the extrusion nozzle, and, consequently, the smaller is the probability of jet breakage. -The Table hereinbelow contains data on the amount of -
. ,." ~ .. . . . . . .
;~!, ' ' ' ' ' ' ' . . ' ` ` , , from 1 to 100 mm mercury, it has been quite unexpectedly found that the loss of weight by the pol~,ler substantially exceeds the content therein of the equilibrium water. It has also been found that the strength of the filament produced from the poly-mer subjected to this thermal treatment is enhanced. In the process of thermal treatment water and other volatile compounds are removed from the polymer. Volatile components may comprise on th~ one hand, formaldehyde which remains in the mass (block) ~ ~o~o~
of polymer granules after gr~nul~ting lt at a polymer manufactur-ing plant, and, on the other hand, formaldehyde which breaksaway (separates) from the unstable portion of the macromolecules of polyoxymethylene while heating the latter. Besides, it is not altogether improbable that under the above conditions there ~; are partially removed the stabilizing additives which had been introduced earlier.
The presence of volatile components in the mass of polyoxymethylene likewise adversely affects the processing properties of the polymer, as it is the case with water. The presence of volatile components in the mass of polyoxy.nethylene, on the one hand, influences the permissible range of melting temperatures. With a high content of volatile substances there might appear in the melt an amount of bubbles which is greater, the higher this melting temperature. Consequently, with a reduced content of volatile substances in the mass of polyoxy-methylene, which is attained by the above described preliminary thermal treatment, it is fairly permissible to raise the melting temperature. The smaller the content of volatile substances in the melt of polyoxymethylene, the smaller is the degree of their evolution from the jets of the melt, leaving the orifices of the extrusion nozzle, and, consequently, the smaller is the probability of jet breakage. -The Table hereinbelow contains data on the amount of -
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104()37Z
volatile substar,ces removed from the st~bilized co-polymer of trioxane and 1,3 dioxolane (the latter contained in a quantity of 4 per cent by weight), as well as on the amount of water left in the co-polymer, depending on the therlllal treatment conditions.
Residual Amount Residual Amount of Content of Vola- Content Volatile Tem of Water tile Sub- of Water Substances P in Speci- stances in Speci- removed C men, % by removed men, % by from weight from weight Specimen, Specimen, % by weight _ _ % bY weiqht _ __ _ Thermal treatment in Thermal treatment ln Vacuum, Air under Normal with Pressure from 1 to 5 mm Pressure mercurv 0.12 - 0.12 100 0.04 0.16 traces 0.26 140 0.02 0.42 d.t.o. 0.62 20155 traces0.55 d.t.o. 0.70 . . _ . _ _ _ It can be seen from the above data that th~ amourlt of removed volatile substances grows with the increase of the temperature of the treatment and with the reduction of the pressure, whereas the water content is practically unaffected by these conditions. The water content was determined by a method based on reduction of iodine in tlle presence of water by sulphur dioxide, known as the Fischer method (see "Control over production of chemical fibre", "Khimiya" Publishers, Moscow, 1967, p. 293). The amount of the removed volatile sub-stances was determined as the difference between the weight ofthe specimen prior to and after the thermal treatment.
Moulding of the filaments is effected by melting the stabilized polyoxymethylene which had been subjected to the thermal treatment, forcing the melt through the orifices of an extrusion nozzle and cooling down the jets of the melt,
104()37Z
volatile substar,ces removed from the st~bilized co-polymer of trioxane and 1,3 dioxolane (the latter contained in a quantity of 4 per cent by weight), as well as on the amount of water left in the co-polymer, depending on the therlllal treatment conditions.
Residual Amount Residual Amount of Content of Vola- Content Volatile Tem of Water tile Sub- of Water Substances P in Speci- stances in Speci- removed C men, % by removed men, % by from weight from weight Specimen, Specimen, % by weight _ _ % bY weiqht _ __ _ Thermal treatment in Thermal treatment ln Vacuum, Air under Normal with Pressure from 1 to 5 mm Pressure mercurv 0.12 - 0.12 100 0.04 0.16 traces 0.26 140 0.02 0.42 d.t.o. 0.62 20155 traces0.55 d.t.o. 0.70 . . _ . _ _ _ It can be seen from the above data that th~ amourlt of removed volatile substances grows with the increase of the temperature of the treatment and with the reduction of the pressure, whereas the water content is practically unaffected by these conditions. The water content was determined by a method based on reduction of iodine in tlle presence of water by sulphur dioxide, known as the Fischer method (see "Control over production of chemical fibre", "Khimiya" Publishers, Moscow, 1967, p. 293). The amount of the removed volatile sub-stances was determined as the difference between the weight ofthe specimen prior to and after the thermal treatment.
Moulding of the filaments is effected by melting the stabilized polyoxymethylene which had been subjected to the thermal treatment, forcing the melt through the orifices of an extrusion nozzle and cooling down the jets of the melt,
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~ 104037Z
leaving the orifices of the nozzle. The meltin~ temperature c~n be in the ranye from 170~C to 230~C depending on the nature of the polyoxymethylene being processed, on its molecular weight and the time of its existence in the melted state, determined by the capacity of the equipment used. The cooling ~ down of the jets of the melt in the vicinity of the nozzle is ; effected at a temperature from ~G~C to 169C. Under the herein disclosed "mild" cooling conditions, the general molecular orientatios~ of the composition is effected and, consequently, the drawing ab;lity of the moulded filaments is stepped up (the draft can be increased), as compared with the drawing ability of filaments moulded at a lower cooling temperature, e.g. at 20C. The phenomenon of reduction of general molecular orientation at processing of polyoxymethylene of d high mole-cular weight, as high as 50,000 to 100,000, is particularly pronounced. Filaments moulded at higher cooling temperatures and subjected to greater draft offer better physical and mechanical properties.
The cooling media can be air, an inert gas, e.g.
nitrogen, steam.
After the cooling the moulded filament is drawn at a temperature from 120C to 165C to a length exceeding the initial length 7 to 14 times. At temperatures below 120C it is not possible to draw polyoxymethylene to a degree providing for production of filaments with adequately high strength. This fact is related to the high degree of crystallinity of polyoxy-methylene, as well as to the large size of the above-molecular structure. To break up this structure for drawing purposes, it is essential that the filament should be heated up to a tempera-ture not below 120C. As the temperature is raised above 145C -150C, there takes place maximally complete breaking up of the initial above-molecular structure, which simplifies the task of its-re-arrangement and re-orientation, and, consequently, the ~ - 8 -.. ~ . . . . .
.,:,.- : . ~.,.. ::: :, , , . -~04~)372 attainable value of draft is sharply increased. Un~er these conditions it becomes possible to draw the moulded filament to a length exceeding the initial length from 9 to 14 times even by single-stage drawing, which provides for high physical and mechanical properties of the filament.
As the drawn polyoxymethylene filaments are worked into various articles and during operation of these articles under the action of elevated temperatures, there might be developed within these filaments considerable internal stresses, as high as 10 kg/mm . Thus, if the filament during its thermal treatment is not tensioned, these internal stresses might lead to shrinkage of the filament, and at the same time there might take place reduction of the tensile strength and an increase of ,~ the value of elongation at rupture.
In order to reduce shrinkage of the produced filaments at subsequent thermal treatment, as well as to maintain the strength of the filaments after such subsequent thermal treat-ment, it is advisable that the drawn polyoxymethylene filaments be subjected to a thermal treatment at a temperature 2~C to 50C
above the temperature at which the filaments were drawn, with the filaments being in a tensioned state. It is possible first to , ~ tension the drawn filaments and then to subject them to the said ; thermal treatment.
As it has been already stated hereinabove, in the , process of thermal treatment of a filament manufactured from thermally pre-treated stabilized polyoxymethylene under the above-specified conditions no reduction of the original strength of the filament is encountered. However, in the process of similar thermal treatment of a filament manufactured from the same stabilized polyoxymethylene pre-treated under different conditions, e.g. in open air at a temperature of 140C, the filament has been found to lose its strength after the above-~A; g 1046)372 ~ ~
specified thermal treatment thereof.
The herein disclosed method is simple technologically.
; It does not require any specific equipment. The method provides for processing into filaments of polyoxymethylene of a high molecular weight without the use of plastifiers (i.e. substances reducing the viscosity of the melt of polyoxymethylene) the addition of which brings about the necessity of carrying out an additional operation connected with removal of these plastifiers from the filament. Furthermore, a filament produced from ther-mally pre-treated polyoxymethylene and moulded under the said cooling conditions is characterized by low general molecular orientation and a minimal content of gas-like impurities. There-fore, it can be drawn under a given temperature duty even in a single stage, with high draft and high drawing speeds (as high as 100 mm/min) which further simplifies the technology and increases the productivity of the equipment.
The herein disclosed method provides for manufacturing polyoxymethylene filaments having high physical and mechanical properties. The tensile strength of the filaments is within a range from 70 to 100 grams per tex, with elongation at rupture from 9 to 12 per cent, the initial modulus being from 1200 to 1800 kilograms per square millimeter. The filaments offer an increased thermal stability and stability to the action of acids, high fatigue stren~th and rubbing resistance. Moreover, the herein disclosed method provides for reducing considerably the degree of shrinkage of a drawn filament, due to the fila-ment having been subjected to tensioning and thermal treatment.
The method of manufacturing polyoxymethylene filaments is carried out as follows.
An initial mass of polyoxymethylene, e.g. in the form of granules, containing stabilizing additives, is thermally pre-treated on a standard equipment, e.g. in vacuum drum-type dryers at a temperature from lOO~C to 150C and pressure from 1 to 100 mm mercury to constant weight. The said thermal treatment may be effected in an inert gas atmosphere, e.g. in a nitrogen atmosphere. In this case the temperature of thermal pre-treatment of polyoxymethylene may be stepped up to 160C to 165C and the operation may be carried out under atmospheric pressure.
Thereafter the thermally pre-treated polyoxymethylene is melted, preferably in an extrusion machine. The melting is performed at a temperature from 170C to 230C, depending on the chemical nature and molecular weight of the polyoxymethylene used. The melting operation may be carried out either in air or in an inert gas atmosphere, e.g. in a nitrogen atmosphere.
The temperature of melting depends on the nature of the poly-oxymethylene used, on the atmosphere in which the melting is performed, on the design of the equipment and may vary from 0.1 to 60 minutes.
The thus obtained polyoxymethylene melt is fed by a metering pump to an extrusion nozzle having either one or several orifices. Prior to being supplied to the nozzle, wherever necessary, the melt may be filtered through metal filtering screens, quartz sand or any other suitable filtering means.
The jets of the melt, leaving the orifices of the extrusion nozzle, are cooled, e.g. in an atmosphere of air heated to 70C - 169C. This may be performed in a closed heated shaft, or else by directing a stream of heated gas, as it is being generally done at the manufacturing of a majority of known synthetic filaments produced by moulding from a polymer melt.
The filament leaving the cooling zone has applied thereon a lubricant, water or any other substance, depending on the destination of the filament.
Then the filament is either wound into a package or ~A 11 : . . .
., : :, ;: .. ~ .. - : :, ::: ., - .- : ~: . -104~37Z
else this stage is by-passed, and the filament is fed directly into a drawing machine. In other words, the herein disclosed method may be performed both in an intermittent and continuous mode.
Drawing or drafting of the filament is effected in a single stage at a temperature from 120C to 165C to a 7:1 to 14:1 draft. The drawing operation is performed by a commonly -~
known system including a feed roller and a drafting one, the circumferential speed of the drafting roller being higher than that of the feeding one. Heating of the filament is effected intermediate of the rollers. The filament can be heated by contact heaters of the "iron" type, or else by passing through a heated tube (with either hot air or radiation heating), alternatively, the filament may pass through a heat0d liquid.
The drawn filament, depending on its destination, may be eithqr twisted or not twisted. The twisting may be performed by any suitable known twisting mechanism, e.g. of the ring twisting kind. It is also possible to cut the drawn filament into staple fibre of a required length.
To obtain low-shrinkage polyoxymethylene filament, the drawn filament is tensioned and thermally treated at a temperature 2C to 50C above the drawing temperature. The thermal treatment may be performed in a continuous "drawing-cum-thermal treatment" process. In this case thermal treatment of the filament may be effected by various existing systems providing for tensioning the filament and heating it to required parameters, e.g. a system including a pair of rollers inter-mediate of which there is ensured a required tension and a heater is provided. In a case of an intermittent process any suitable technique may be used, e.g. thermal treatment of the filament wound at a required tension on a rigid bobbin. The thermal treatment of the filament may be performed in various : .. . - ` . ' ... : . . . . . .
;,, . . ` ,. ~ . . .. .
~040372 atmospheres (gaseous or liquid) wherein no chemical dcstruct-ion of polyoxymethylene takes place, or else in air. The time and parameters of the thermal treatment of the filament are defined by the requirements as to the value of permissible shrinkage of final filaments.
For the present invention to be better understood, there are described hereinbelow several examples.
Exam~le 1.
Granulated co-polymer of trioxane and 1,3-dioxolane (the weight content of the latter being 4 per cent) with additives: 2,2'-methylene bis-(4-methyl-6-terbutyl phenol) in a quantity of 0.5 per cent by weight as the antioxidant and formaldehyde-dicyanamide in a quantity of 0.5 per cent by weight as the acceptor, with characteristic viscosity in dimethylformamide equalling 0.56 is thermally treated at 100C
and pressure of 5 mm mercury, melted in an extrusion machine in an air atmosphere at 190C, and the melt is forced by a metering pump through an extrusion nozzle with a single orifice 1.2 mm in diameter. The rate of feed of the melt is 5 gr/min. The jet of the melt is cooled in a 0.5 m long tube. The temperature of the air cooling the jet of the melt is 90C. The filament mou~ding rate is 250 m/min.
The moulded filament is drawn to a 10:1 draft at a speed of 125 m/min over a 250 mm long "iron" at 150C. The !, obtained filament has 72 grams per tex tensile strength and elongation at rupture equalling 11.5%. The shrinkage of the filament is 18~/o~ with 80% of the initial strength remaining after the shrinkage.
After the drawing operation the filament is thermally treated in air under a tension of 2 kilograms per square milli-meter at 155C. for 30 minutes. After this treatment the shrinkage value is 4%, with 95% of the initial strength rer"aining ,.~- . ... - :- - - . .: .
., . - , .
~41)37Z
after the shrinkage.
Example 2.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 1, with a difference that the initial mass of polyoxymethylene is thermally treated at 130C and pressure of 10 mm mercury, the co-polymer is melted at 200C, and the jet of the melt is cooled in air at a temperature of 70C.
The filament obtained features 75 gr/tex tensile strength and 11.1% elongation at rupture. The shrinkage rate of this filament is 17%, with 82% of the initial strength remain-ing after the shrinkage. After the drawing operation the fila-ment is thermally treated in a nitrogen atmosphere at 161~C under 6 kg/mm2 tension for 20 minutes. After this treatment the shrinkage rate of the filament is 1%, with 96% of the initial ~trength remaining after the shrinkage.
ExamPle 3.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 1, with a difference that a co-polymer of formaldehyde and 1,3-dioxolane is used, haviny characteristic viscosity in dimethylformamide equalling 0.65, the co-polymer is thermally treated at 150~C and 1 mm mercury pressure, the co-polymer is melted at 185C, and the jet of the melt is cooled in air at 140C in a 0.4 m long tube. The moulded filament is drawn to a 12:1 draft a speed of 75 m/min over a 400 mm long "iron".
The filament obtained has 86 gr/tex tensile strenyth and 10% elongation at rupture. The shrinkage rate of this filament is 15%, with 87% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated at 170C in a nitrogen atmosphere under 10 kg/mm2 tension for 5 '. ~
: . ' : . `- ' ` ~ ` ' , ~040372 minutes. Following this treatment the shrinkage is 0.5~0, with 95% of the initial strength remaining after the shrin]c-age.
Example 4.
A polyoxymethylene filament is moulded as described above in Example 3, a difference being in that the co-polymer is thermally treated at 140C and pressure of 95 mm mercury;
the co-polymer is melted at 180C; the jet of the melt is cooled in air at 120~C.
The moulded filament is drawn to a 13.6:1 draft at a speed of 25 m/min over a 1000 mm long "iron" at 158"C.
The filament obtained is characterized by 98 gr/tex tensile strength and 9% elongation at rupture. The shrinkage rate of the filament is 11%, with 90% of the initial strength remaining after the shrinkage.
, After the drawing the filament is thermally treated at 150C under 0.2 kg/mm2 tension for 150 minutes. F'ollowing the treatment, the shrinkage of the filament is 3%, with 9~'~O of the initial strength remaining.
Example 5.
A polyoxymethylene filament is moulded and drawn, as described abo~e in Example 1, with a difference that there is used a copolymer of trioxane and a cyclic ester, i.e, ethylene oxide (the weight content of the latter being 3 per cent), having characteristic viscosity in dimethylformamide equalling 0.50;
the copolymer is thermally treated at 130C and pressure equalling 50 mm mercury, the copolymer is melted at 170~C, and the melt is forced through an extrusion nozzle having 24 orifices 0.40 mm in diameter. The rate of feed of the mel-c is 20 grams per minute. The jets of the melt are cooled in a 0.7 m long tube with air at 100C. The filament moulding rate is 450 m/min.
; ........... ~.
:,` .
1~)4~)372 The filament obtained is characterized by 76 yr/tex tensile strength and 14% elongation at rupture. The shrinkage of this filament is 20%, with 75% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated in a nitrogen atmosphere at 152C under 4 kg/mm2 tension for 240 minutes.
Following this treatment the shrinkage is 5%, with 92% of the initial strength remaining.
ExamPle 6.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 5, with a difference that the temperature of the air cooling the jets of the melt is 70C.
The moulded filament is drawn to a 7:1 draft at a 10 m/min speed over a 700 mrn long "iron" at 120C.
The filament obtained has 62 gr/tex tensile strength, with 16% elongation at rupture. The shrinkage rate of this filament is 25%, with 67% of the initial strength rernairling after the shrinkage.
After the drawing the filament is thermally treated in a nitrogen atmosphere at 150C under 8 kg/mm2 tension.
Following this treatment the shrinkage rate at 150~C
is 10%, with 85% of the initial strength remaining.
Exam~le 7.
A co-polymer of formaldehyde and 1,3-dioxolane (the weight content of the latter being 5%) in a powder form is mixed with stabilizing additives, viz. 2,2'-methylene bis-(4-mcthyl-6-terbutyl phenol) in a quantity of 2.5% by weight as the anti-oxidant and formaldehyde-dicyanamide in a quantity of 0.5% by weight as the acceptor: the co-polymer is thermally treated, as described above in Example 5 and melted at 170C. The co-polymer used has characteristic viscosity of 0.42.
~A
:: . ,,., : .: ~
The filament is moulded, as described hereinabove in Example 6, and drawn to a 8:1 draft in a contactless 800 mm long heater in an atmosphere of air heated to 130C at a speed of S0 m/min.
The filament obtained is characterized by 59 gr/tex tensile strength and 20% elongation at rupture.
Example 8.
A granulated homo-polymer of formaldehyde, containing 0.5% by weight co-polymer based on hexamethylene diamine, adipinic acid and caprolactam and 0.5% by weight dicyanamide, having characteristic viscosity in dimethylformamide equalling 0.86, is thermally treated at 110C and 0.5 mm mercury pressure.
Then the polymer is melted in a nitrogen atmosphere at 210C, and the melt thus obtained is forced through an extrusion nozzle with 12 orifices 0.8 mm in diameter, the rate of feed of the melt being 20 grams a minute. The jets of the melt are cooled with nitrogen heated to 165C. The filament moulding spee~ iq 500 m/min.
The moulded filament is drawn to a 8:1 draft at a rate of 15 m/min over a 700 mm long "iron" at 161C.
The filament obtained has 71 gr/tex tensile strength and elongation at rupture equalling 12%.
,: ExamPle 9.
A polyoxymethylene filament is moulded, as described above in Example 1, with a difference that the polyoxymethylene is melted in a nitrogen atmosphere at 225C, and the melt thus obtained is forced through an extrusion nozzle having 80 orifices ' 0.5 mm in diameter, the rate of feed of the melt being 150 gr/min. The temperature of the air cooling the jets of the ; 30 melt is 80C. The filament moulding speed is 300 m/min.
The moulded filament is drawn to a 9:1 draft over a 500 mm long "iron" at 150C.
1~4~)37Z
The filament obtained is characterized by 75 gr/tex tensile strength and 13% elongation at rupture. The shrinkage of this filament is 17%, with 82% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated in air at 157C under 8 kg/mm2 tension for 40 minutes.
Following this treatment the shrinkage rate of the filament is 4%, with 92% of the initial strength remaining.
In the above examples the tensile strength was determined on a pendulum-type rupturing machine, with filament elongation rate being 500 mm/min. and clamping length being 250 mm.
The shrinkage rate of the filament is determined from the ratio:
shrinkage rate equals Il 2 .100%, where Il is the initial length of the specimen, equalling 250 mm;
I2 is the length of the specimen after the filament has been heated slack to 150C in air for O.S hours.
The conservation of strength (rate of strength preserved) after shrinkage of the filament is determined by the ratio:
p2 .100%, where Pl is the strength of the initial filament (before the heat treatment of the filament), in grams per tex, and P2 is the preserved strength of the filament after its shrinkage, in grams per tex.
' ' ~ - 18 - ~
. .. , ~
.. ; . .. . .
" ;.. '.,~ ` ~ -i . ~ . ,~
~ 104037Z
leaving the orifices of the nozzle. The meltin~ temperature c~n be in the ranye from 170~C to 230~C depending on the nature of the polyoxymethylene being processed, on its molecular weight and the time of its existence in the melted state, determined by the capacity of the equipment used. The cooling ~ down of the jets of the melt in the vicinity of the nozzle is ; effected at a temperature from ~G~C to 169C. Under the herein disclosed "mild" cooling conditions, the general molecular orientatios~ of the composition is effected and, consequently, the drawing ab;lity of the moulded filaments is stepped up (the draft can be increased), as compared with the drawing ability of filaments moulded at a lower cooling temperature, e.g. at 20C. The phenomenon of reduction of general molecular orientation at processing of polyoxymethylene of d high mole-cular weight, as high as 50,000 to 100,000, is particularly pronounced. Filaments moulded at higher cooling temperatures and subjected to greater draft offer better physical and mechanical properties.
The cooling media can be air, an inert gas, e.g.
nitrogen, steam.
After the cooling the moulded filament is drawn at a temperature from 120C to 165C to a length exceeding the initial length 7 to 14 times. At temperatures below 120C it is not possible to draw polyoxymethylene to a degree providing for production of filaments with adequately high strength. This fact is related to the high degree of crystallinity of polyoxy-methylene, as well as to the large size of the above-molecular structure. To break up this structure for drawing purposes, it is essential that the filament should be heated up to a tempera-ture not below 120C. As the temperature is raised above 145C -150C, there takes place maximally complete breaking up of the initial above-molecular structure, which simplifies the task of its-re-arrangement and re-orientation, and, consequently, the ~ - 8 -.. ~ . . . . .
.,:,.- : . ~.,.. ::: :, , , . -~04~)372 attainable value of draft is sharply increased. Un~er these conditions it becomes possible to draw the moulded filament to a length exceeding the initial length from 9 to 14 times even by single-stage drawing, which provides for high physical and mechanical properties of the filament.
As the drawn polyoxymethylene filaments are worked into various articles and during operation of these articles under the action of elevated temperatures, there might be developed within these filaments considerable internal stresses, as high as 10 kg/mm . Thus, if the filament during its thermal treatment is not tensioned, these internal stresses might lead to shrinkage of the filament, and at the same time there might take place reduction of the tensile strength and an increase of ,~ the value of elongation at rupture.
In order to reduce shrinkage of the produced filaments at subsequent thermal treatment, as well as to maintain the strength of the filaments after such subsequent thermal treat-ment, it is advisable that the drawn polyoxymethylene filaments be subjected to a thermal treatment at a temperature 2~C to 50C
above the temperature at which the filaments were drawn, with the filaments being in a tensioned state. It is possible first to , ~ tension the drawn filaments and then to subject them to the said ; thermal treatment.
As it has been already stated hereinabove, in the , process of thermal treatment of a filament manufactured from thermally pre-treated stabilized polyoxymethylene under the above-specified conditions no reduction of the original strength of the filament is encountered. However, in the process of similar thermal treatment of a filament manufactured from the same stabilized polyoxymethylene pre-treated under different conditions, e.g. in open air at a temperature of 140C, the filament has been found to lose its strength after the above-~A; g 1046)372 ~ ~
specified thermal treatment thereof.
The herein disclosed method is simple technologically.
; It does not require any specific equipment. The method provides for processing into filaments of polyoxymethylene of a high molecular weight without the use of plastifiers (i.e. substances reducing the viscosity of the melt of polyoxymethylene) the addition of which brings about the necessity of carrying out an additional operation connected with removal of these plastifiers from the filament. Furthermore, a filament produced from ther-mally pre-treated polyoxymethylene and moulded under the said cooling conditions is characterized by low general molecular orientation and a minimal content of gas-like impurities. There-fore, it can be drawn under a given temperature duty even in a single stage, with high draft and high drawing speeds (as high as 100 mm/min) which further simplifies the technology and increases the productivity of the equipment.
The herein disclosed method provides for manufacturing polyoxymethylene filaments having high physical and mechanical properties. The tensile strength of the filaments is within a range from 70 to 100 grams per tex, with elongation at rupture from 9 to 12 per cent, the initial modulus being from 1200 to 1800 kilograms per square millimeter. The filaments offer an increased thermal stability and stability to the action of acids, high fatigue stren~th and rubbing resistance. Moreover, the herein disclosed method provides for reducing considerably the degree of shrinkage of a drawn filament, due to the fila-ment having been subjected to tensioning and thermal treatment.
The method of manufacturing polyoxymethylene filaments is carried out as follows.
An initial mass of polyoxymethylene, e.g. in the form of granules, containing stabilizing additives, is thermally pre-treated on a standard equipment, e.g. in vacuum drum-type dryers at a temperature from lOO~C to 150C and pressure from 1 to 100 mm mercury to constant weight. The said thermal treatment may be effected in an inert gas atmosphere, e.g. in a nitrogen atmosphere. In this case the temperature of thermal pre-treatment of polyoxymethylene may be stepped up to 160C to 165C and the operation may be carried out under atmospheric pressure.
Thereafter the thermally pre-treated polyoxymethylene is melted, preferably in an extrusion machine. The melting is performed at a temperature from 170C to 230C, depending on the chemical nature and molecular weight of the polyoxymethylene used. The melting operation may be carried out either in air or in an inert gas atmosphere, e.g. in a nitrogen atmosphere.
The temperature of melting depends on the nature of the poly-oxymethylene used, on the atmosphere in which the melting is performed, on the design of the equipment and may vary from 0.1 to 60 minutes.
The thus obtained polyoxymethylene melt is fed by a metering pump to an extrusion nozzle having either one or several orifices. Prior to being supplied to the nozzle, wherever necessary, the melt may be filtered through metal filtering screens, quartz sand or any other suitable filtering means.
The jets of the melt, leaving the orifices of the extrusion nozzle, are cooled, e.g. in an atmosphere of air heated to 70C - 169C. This may be performed in a closed heated shaft, or else by directing a stream of heated gas, as it is being generally done at the manufacturing of a majority of known synthetic filaments produced by moulding from a polymer melt.
The filament leaving the cooling zone has applied thereon a lubricant, water or any other substance, depending on the destination of the filament.
Then the filament is either wound into a package or ~A 11 : . . .
., : :, ;: .. ~ .. - : :, ::: ., - .- : ~: . -104~37Z
else this stage is by-passed, and the filament is fed directly into a drawing machine. In other words, the herein disclosed method may be performed both in an intermittent and continuous mode.
Drawing or drafting of the filament is effected in a single stage at a temperature from 120C to 165C to a 7:1 to 14:1 draft. The drawing operation is performed by a commonly -~
known system including a feed roller and a drafting one, the circumferential speed of the drafting roller being higher than that of the feeding one. Heating of the filament is effected intermediate of the rollers. The filament can be heated by contact heaters of the "iron" type, or else by passing through a heated tube (with either hot air or radiation heating), alternatively, the filament may pass through a heat0d liquid.
The drawn filament, depending on its destination, may be eithqr twisted or not twisted. The twisting may be performed by any suitable known twisting mechanism, e.g. of the ring twisting kind. It is also possible to cut the drawn filament into staple fibre of a required length.
To obtain low-shrinkage polyoxymethylene filament, the drawn filament is tensioned and thermally treated at a temperature 2C to 50C above the drawing temperature. The thermal treatment may be performed in a continuous "drawing-cum-thermal treatment" process. In this case thermal treatment of the filament may be effected by various existing systems providing for tensioning the filament and heating it to required parameters, e.g. a system including a pair of rollers inter-mediate of which there is ensured a required tension and a heater is provided. In a case of an intermittent process any suitable technique may be used, e.g. thermal treatment of the filament wound at a required tension on a rigid bobbin. The thermal treatment of the filament may be performed in various : .. . - ` . ' ... : . . . . . .
;,, . . ` ,. ~ . . .. .
~040372 atmospheres (gaseous or liquid) wherein no chemical dcstruct-ion of polyoxymethylene takes place, or else in air. The time and parameters of the thermal treatment of the filament are defined by the requirements as to the value of permissible shrinkage of final filaments.
For the present invention to be better understood, there are described hereinbelow several examples.
Exam~le 1.
Granulated co-polymer of trioxane and 1,3-dioxolane (the weight content of the latter being 4 per cent) with additives: 2,2'-methylene bis-(4-methyl-6-terbutyl phenol) in a quantity of 0.5 per cent by weight as the antioxidant and formaldehyde-dicyanamide in a quantity of 0.5 per cent by weight as the acceptor, with characteristic viscosity in dimethylformamide equalling 0.56 is thermally treated at 100C
and pressure of 5 mm mercury, melted in an extrusion machine in an air atmosphere at 190C, and the melt is forced by a metering pump through an extrusion nozzle with a single orifice 1.2 mm in diameter. The rate of feed of the melt is 5 gr/min. The jet of the melt is cooled in a 0.5 m long tube. The temperature of the air cooling the jet of the melt is 90C. The filament mou~ding rate is 250 m/min.
The moulded filament is drawn to a 10:1 draft at a speed of 125 m/min over a 250 mm long "iron" at 150C. The !, obtained filament has 72 grams per tex tensile strength and elongation at rupture equalling 11.5%. The shrinkage of the filament is 18~/o~ with 80% of the initial strength remaining after the shrinkage.
After the drawing operation the filament is thermally treated in air under a tension of 2 kilograms per square milli-meter at 155C. for 30 minutes. After this treatment the shrinkage value is 4%, with 95% of the initial strength rer"aining ,.~- . ... - :- - - . .: .
., . - , .
~41)37Z
after the shrinkage.
Example 2.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 1, with a difference that the initial mass of polyoxymethylene is thermally treated at 130C and pressure of 10 mm mercury, the co-polymer is melted at 200C, and the jet of the melt is cooled in air at a temperature of 70C.
The filament obtained features 75 gr/tex tensile strength and 11.1% elongation at rupture. The shrinkage rate of this filament is 17%, with 82% of the initial strength remain-ing after the shrinkage. After the drawing operation the fila-ment is thermally treated in a nitrogen atmosphere at 161~C under 6 kg/mm2 tension for 20 minutes. After this treatment the shrinkage rate of the filament is 1%, with 96% of the initial ~trength remaining after the shrinkage.
ExamPle 3.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 1, with a difference that a co-polymer of formaldehyde and 1,3-dioxolane is used, haviny characteristic viscosity in dimethylformamide equalling 0.65, the co-polymer is thermally treated at 150~C and 1 mm mercury pressure, the co-polymer is melted at 185C, and the jet of the melt is cooled in air at 140C in a 0.4 m long tube. The moulded filament is drawn to a 12:1 draft a speed of 75 m/min over a 400 mm long "iron".
The filament obtained has 86 gr/tex tensile strenyth and 10% elongation at rupture. The shrinkage rate of this filament is 15%, with 87% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated at 170C in a nitrogen atmosphere under 10 kg/mm2 tension for 5 '. ~
: . ' : . `- ' ` ~ ` ' , ~040372 minutes. Following this treatment the shrinkage is 0.5~0, with 95% of the initial strength remaining after the shrin]c-age.
Example 4.
A polyoxymethylene filament is moulded as described above in Example 3, a difference being in that the co-polymer is thermally treated at 140C and pressure of 95 mm mercury;
the co-polymer is melted at 180C; the jet of the melt is cooled in air at 120~C.
The moulded filament is drawn to a 13.6:1 draft at a speed of 25 m/min over a 1000 mm long "iron" at 158"C.
The filament obtained is characterized by 98 gr/tex tensile strength and 9% elongation at rupture. The shrinkage rate of the filament is 11%, with 90% of the initial strength remaining after the shrinkage.
, After the drawing the filament is thermally treated at 150C under 0.2 kg/mm2 tension for 150 minutes. F'ollowing the treatment, the shrinkage of the filament is 3%, with 9~'~O of the initial strength remaining.
Example 5.
A polyoxymethylene filament is moulded and drawn, as described abo~e in Example 1, with a difference that there is used a copolymer of trioxane and a cyclic ester, i.e, ethylene oxide (the weight content of the latter being 3 per cent), having characteristic viscosity in dimethylformamide equalling 0.50;
the copolymer is thermally treated at 130C and pressure equalling 50 mm mercury, the copolymer is melted at 170~C, and the melt is forced through an extrusion nozzle having 24 orifices 0.40 mm in diameter. The rate of feed of the mel-c is 20 grams per minute. The jets of the melt are cooled in a 0.7 m long tube with air at 100C. The filament moulding rate is 450 m/min.
; ........... ~.
:,` .
1~)4~)372 The filament obtained is characterized by 76 yr/tex tensile strength and 14% elongation at rupture. The shrinkage of this filament is 20%, with 75% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated in a nitrogen atmosphere at 152C under 4 kg/mm2 tension for 240 minutes.
Following this treatment the shrinkage is 5%, with 92% of the initial strength remaining.
ExamPle 6.
Polyoxymethylene filaments are moulded and drawn, as described above in Example 5, with a difference that the temperature of the air cooling the jets of the melt is 70C.
The moulded filament is drawn to a 7:1 draft at a 10 m/min speed over a 700 mrn long "iron" at 120C.
The filament obtained has 62 gr/tex tensile strength, with 16% elongation at rupture. The shrinkage rate of this filament is 25%, with 67% of the initial strength rernairling after the shrinkage.
After the drawing the filament is thermally treated in a nitrogen atmosphere at 150C under 8 kg/mm2 tension.
Following this treatment the shrinkage rate at 150~C
is 10%, with 85% of the initial strength remaining.
Exam~le 7.
A co-polymer of formaldehyde and 1,3-dioxolane (the weight content of the latter being 5%) in a powder form is mixed with stabilizing additives, viz. 2,2'-methylene bis-(4-mcthyl-6-terbutyl phenol) in a quantity of 2.5% by weight as the anti-oxidant and formaldehyde-dicyanamide in a quantity of 0.5% by weight as the acceptor: the co-polymer is thermally treated, as described above in Example 5 and melted at 170C. The co-polymer used has characteristic viscosity of 0.42.
~A
:: . ,,., : .: ~
The filament is moulded, as described hereinabove in Example 6, and drawn to a 8:1 draft in a contactless 800 mm long heater in an atmosphere of air heated to 130C at a speed of S0 m/min.
The filament obtained is characterized by 59 gr/tex tensile strength and 20% elongation at rupture.
Example 8.
A granulated homo-polymer of formaldehyde, containing 0.5% by weight co-polymer based on hexamethylene diamine, adipinic acid and caprolactam and 0.5% by weight dicyanamide, having characteristic viscosity in dimethylformamide equalling 0.86, is thermally treated at 110C and 0.5 mm mercury pressure.
Then the polymer is melted in a nitrogen atmosphere at 210C, and the melt thus obtained is forced through an extrusion nozzle with 12 orifices 0.8 mm in diameter, the rate of feed of the melt being 20 grams a minute. The jets of the melt are cooled with nitrogen heated to 165C. The filament moulding spee~ iq 500 m/min.
The moulded filament is drawn to a 8:1 draft at a rate of 15 m/min over a 700 mm long "iron" at 161C.
The filament obtained has 71 gr/tex tensile strength and elongation at rupture equalling 12%.
,: ExamPle 9.
A polyoxymethylene filament is moulded, as described above in Example 1, with a difference that the polyoxymethylene is melted in a nitrogen atmosphere at 225C, and the melt thus obtained is forced through an extrusion nozzle having 80 orifices ' 0.5 mm in diameter, the rate of feed of the melt being 150 gr/min. The temperature of the air cooling the jets of the ; 30 melt is 80C. The filament moulding speed is 300 m/min.
The moulded filament is drawn to a 9:1 draft over a 500 mm long "iron" at 150C.
1~4~)37Z
The filament obtained is characterized by 75 gr/tex tensile strength and 13% elongation at rupture. The shrinkage of this filament is 17%, with 82% of the initial strength remaining after the shrinkage.
After the drawing the filament is thermally treated in air at 157C under 8 kg/mm2 tension for 40 minutes.
Following this treatment the shrinkage rate of the filament is 4%, with 92% of the initial strength remaining.
In the above examples the tensile strength was determined on a pendulum-type rupturing machine, with filament elongation rate being 500 mm/min. and clamping length being 250 mm.
The shrinkage rate of the filament is determined from the ratio:
shrinkage rate equals Il 2 .100%, where Il is the initial length of the specimen, equalling 250 mm;
I2 is the length of the specimen after the filament has been heated slack to 150C in air for O.S hours.
The conservation of strength (rate of strength preserved) after shrinkage of the filament is determined by the ratio:
p2 .100%, where Pl is the strength of the initial filament (before the heat treatment of the filament), in grams per tex, and P2 is the preserved strength of the filament after its shrinkage, in grams per tex.
' ' ~ - 18 - ~
Claims (2)
1. A method of manufacturing polyoxymethylene filaments, wherein polyoxymethylene having a molecular weight within a range from 30,000 to 100,000 and including stabilizing additives in a quantity from 0.1 to 3.0 per cent of the weight of said polyoxymethylene is thermally treated at a temperature within a range from 100°C to 150°C and pressure from 1 to 100 mmHg to a constant weight; said thermally treated polyoxymethylene is subjected to melting at a temperature within a range from 170°C
to 230°C; the thus obtained melt is forced through the orifices of an extrusion nozzle; the jets of said melt, leaving the orifices of the extrusion nozzle are cooled to a temperature within a range from 70°C to 169°C; after said cooling the moulded filaments obtained are subjected to drawing at a temperature within a range from 120°C to 165°C to a length exceeding the initial length from seven to fourteen times.
to 230°C; the thus obtained melt is forced through the orifices of an extrusion nozzle; the jets of said melt, leaving the orifices of the extrusion nozzle are cooled to a temperature within a range from 70°C to 169°C; after said cooling the moulded filaments obtained are subjected to drawing at a temperature within a range from 120°C to 165°C to a length exceeding the initial length from seven to fourteen times.
2. A method as claimed in claim 1, wherein after said drawing the filaments are thermally treated at a temperature by 2°C to 50°C above said temperature of said drawing, under a tension.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,887A CA1040372A (en) | 1974-08-13 | 1974-08-13 | Method of manufacturing polyoxymethylene filaments |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA206,887A CA1040372A (en) | 1974-08-13 | 1974-08-13 | Method of manufacturing polyoxymethylene filaments |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1040372A true CA1040372A (en) | 1978-10-17 |
Family
ID=4100885
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA206,887A Expired CA1040372A (en) | 1974-08-13 | 1974-08-13 | Method of manufacturing polyoxymethylene filaments |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1040372A (en) |
-
1974
- 1974-08-13 CA CA206,887A patent/CA1040372A/en not_active Expired
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