CN115323527A - Preparation method of polytetrafluoroethylene fiber with high surface roughness - Google Patents
Preparation method of polytetrafluoroethylene fiber with high surface roughness Download PDFInfo
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- CN115323527A CN115323527A CN202210999685.XA CN202210999685A CN115323527A CN 115323527 A CN115323527 A CN 115323527A CN 202210999685 A CN202210999685 A CN 202210999685A CN 115323527 A CN115323527 A CN 115323527A
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- 229920001343 polytetrafluoroethylene Polymers 0.000 title claims abstract description 187
- 239000004810 polytetrafluoroethylene Substances 0.000 title claims abstract description 186
- -1 polytetrafluoroethylene Polymers 0.000 title claims abstract description 185
- 239000000835 fiber Substances 0.000 title claims abstract description 100
- 230000003746 surface roughness Effects 0.000 title claims abstract description 38
- 238000002360 preparation method Methods 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 39
- 238000002156 mixing Methods 0.000 claims abstract description 28
- 238000009998 heat setting Methods 0.000 claims abstract description 27
- 239000000203 mixture Substances 0.000 claims abstract description 17
- 239000010687 lubricating oil Substances 0.000 claims abstract description 8
- 238000005096 rolling process Methods 0.000 claims abstract description 7
- 230000002040 relaxant effect Effects 0.000 claims abstract 2
- 239000000463 material Substances 0.000 claims description 30
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- 238000004804 winding Methods 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 239000002904 solvent Substances 0.000 claims description 3
- 239000002245 particle Substances 0.000 description 17
- 238000003490 calendering Methods 0.000 description 16
- 230000000052 comparative effect Effects 0.000 description 15
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- 239000000654 additive Substances 0.000 description 7
- 238000012360 testing method Methods 0.000 description 7
- 208000027418 Wounds and injury Diseases 0.000 description 6
- 238000001035 drying Methods 0.000 description 4
- 238000010008 shearing Methods 0.000 description 4
- 208000002064 Dental Plaque Diseases 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 230000006378 damage Effects 0.000 description 3
- 230000036541 health Effects 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000000725 suspension Substances 0.000 description 3
- 241001391944 Commicarpus scandens Species 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
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- BFKJFAAPBSQJPD-UHFFFAOYSA-N tetrafluoroethene Chemical group FC(F)=C(F)F BFKJFAAPBSQJPD-UHFFFAOYSA-N 0.000 description 2
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- 230000003247 decreasing effect Effects 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 239000002270 dispersing agent Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 208000007565 gingivitis Diseases 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
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Classifications
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F8/00—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof
- D01F8/04—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers
- D01F8/10—Conjugated, i.e. bi- or multicomponent, artificial filaments or the like; Manufacture thereof from synthetic polymers with at least one other macromolecular compound obtained by reactions only involving carbon-to-carbon unsaturated bonds as constituent
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F1/00—General methods for the manufacture of artificial filaments or the like
- D01F1/02—Addition of substances to the spinning solution or to the melt
- D01F1/10—Other agents for modifying properties
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/44—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds
- D01F6/48—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from mixtures of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds as major constituent with other polymers or low-molecular-weight compounds of polymers of halogenated hydrocarbons
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
- Y02P70/62—Manufacturing or production processes characterised by the final manufactured product related technologies for production or treatment of textile or flexible materials or products thereof, including footwear
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Textile Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Artificial Filaments (AREA)
Abstract
The invention belongs to the technical field of polytetrafluoroethylene fibers, and particularly relates to a preparation method of a polytetrafluoroethylene fiber with high surface roughness. The preparation method comprises the following steps: (1) Mixing the dispersed polytetrafluoroethylene with lubricating oil, and curing; (2) After curing, adding suspended polytetrafluoroethylene and mixing to obtain a mixture; (3) And performing, extruding, rolling, deoiling, stretching, slitting and relaxing heat setting on the mixture to prepare the polytetrafluoroethylene fiber with high surface roughness. The preparation method fundamentally solves the problem of low bonding degree existing in the prior method for improving the surface roughness of the polytetrafluoroethylene fiber.
Description
Technical Field
The invention belongs to the technical field of polytetrafluoroethylene fibers, and particularly relates to a preparation method of a polytetrafluoroethylene fiber with high surface roughness.
Background
Generally, it is difficult to clean each tooth surface only by using a toothbrush, so in addition to regular tooth brushing, the interdental space should be cleaned daily to prevent food and soft calculus from forming bacterial plaque after being embedded in the interdental space. The bacteria leading to gingivitis and periodontitis generally come from dental plaque in the tooth gaps, and the use of dental floss is the best method for removing adjacent dental plaque. The dental floss is usually made of nylon thread, silk thread, polyester thread or waxed cotton thread, and the threads of the above types all have the defect of high friction coefficient (generally > 0.3), so that the lubricity is poor, and the gum is easy to damage. In addition, the yarn has the defects of no wear resistance, yarn breakage and fuzz. It is seen that there is a great need to find materials more suitable for use in the manufacture of dental floss.
The polytetrafluoroethylene fiber has extremely low friction coefficient (less than or equal to 0.04) and good biocompatibility, and is an ideal material for preparing dental floss. Although a dental floss made of polytetrafluoroethylene fibers has high lubricity, and can be easily and rapidly slid into gaps between teeth and freely slid between teeth, the surface is too smooth to facilitate cleaning of teeth, because plaque attached to the surfaces of teeth and between teeth is not easily removed if the roughness of the dental floss is insufficient. Meanwhile, when the surface of the dental floss is too smooth, the dental floss is easy to slip from the hand when a user cleans teeth, and the operation of the user is not facilitated. Therefore, the polytetrafluoroethylene fiber with high lubricity can be better applied to the dental floss field by properly improving the surface roughness of the fiber.
In order to increase the surface roughness of polytetrafluoroethylene fibers, patents US5033488 and US5209251 are improved by coating the surface of the polytetrafluoroethylene fibers with microcrystalline wax. However, this method has the disadvantage that the coating layer may be partially or completely peeled off from the surface of the polytetrafluoroethylene fiber due to insufficient surface bonding force during the use process, and remain in the user's hand, teeth or mouth, which brings about a hidden danger to human health; secondly, the process of coating the surface of the polytetrafluoroethylene fibers tends to increase the production cycle time and the corresponding production cost.
In the prior art, as mentioned in "research and development of polytetrafluoroethylene inorganic nanocomposite" a manner of adding some inorganic particles to polytetrafluoroethylene fibers is adopted to improve the surface roughness of the polytetrafluoroethylene fibers, for example, adding additives such as titanium dioxide, graphite, etc. However, the problems of poor compatibility and mismatched thermal expansion coefficient exist between the inorganic particles and the polytetrafluoroethylene, and further the polytetrafluoroethylene fibers and the additives are not firmly combined due to insufficient binding force, so that part of the exposed particle additives are easy to fall off during use, and the human health is not facilitated.
In summary, the prior art methods for increasing the surface roughness of polytetrafluoroethylene fibers generally include adding filler/particle additives to the polytetrafluoroethylene fibers or coating the surfaces of the polytetrafluoroethylene fibers with a particle coating. These methods all have the problem of not firm combination, so that the coating or the particle additive is easy to fall off in the using process, if the dental floss made of the polytetrafluoroethylene fiber is used, the experience feeling of a user is very poor, the dental floss is not beneficial to the health of the human body, and unnecessary injury can be caused to the human body. In addition, the addition or coating needs to be additionally provided with additional treatment steps, the process flow is complex, the production period is prolonged, and the production cost is increased.
Disclosure of Invention
The invention aims to provide a novel preparation method of polytetrafluoroethylene fibers with high surface roughness, aiming at the problems that the existing method for improving the surface roughness of the polytetrafluoroethylene fibers has low bonding degree, needs to add a new procedure on the basis of the original polytetrafluoroethylene fiber preparation process, is time-consuming and needs to increase the investment cost due to the addition of the new procedure.
The preparation method fundamentally solves the problem of low bonding degree existing in the prior method for improving the surface roughness of the polytetrafluoroethylene fiber. Meanwhile, the preparation method is based on the existing polytetrafluoroethylene fiber preparation process flow, and the surface roughness of the polytetrafluoroethylene fiber can be obviously improved without adding coating and other working procedures, so that the preparation method is more economical and simple, and the input cost is low. The polytetrafluoroethylene fiber obtained by the preparation method has high surface roughness, does not have any problem of compatibility, and is safe and firm to use.
The specific technical scheme is as follows:
a preparation method of polytetrafluoroethylene fibers with high surface roughness comprises the following steps:
(1) Mixing the dispersed polytetrafluoroethylene with lubricating oil, and curing; so as to obtain the cooked material, and then,
(2) Adding suspended polytetrafluoroethylene into the cured material obtained in the step (1) and mixing to obtain a mixture;
(3) And performing, extruding, rolling, deoiling, stretching, slitting and relaxation heat setting on the mixture to prepare the polytetrafluoroethylene fiber with high surface roughness.
Polytetrafluoroethylene generally falls into two categories: one is suspended polytetrafluoroethylene and one is dispersed polytetrafluoroethylene.
The suspended polytetrafluoroethylene is non-hydrophilic powder obtained by suspension polymerization of tetrafluoroethylene monomer, and has a density of 2.14-2.20 g/cm 3 The plastic has the highest density, the crystal is hexagonal (above 19 ℃) or triclinic (below 19 ℃), and the melting temperature is 327 ℃. It is a transparent gel above the melting point, but has almost no fluidity, and has a melt viscosity of about 1011 poise at 380 ℃. The suspended polytetrafluoroethylene has extremely high melt viscosity (107-108 kPa · s), keeps the original form and does not flow when being melted, is very sensitive to shearing and is easy to generate melt fracture. Therefore, suspended ptfe can only be formed by powder metallurgy-like processes, which consist of 3 major steps, namely preforming, sintering and cooling. Common preforming methods include compression molding, hydroforming, automated compression molding, plunger extrusion, and the like. The products of the suspended polytetrafluoroethylene are plates, rods and pipes generally, and are applied to the fields of conveying pipelines, valves, electric wires and cables, bearings and the like.
The dispersed polytetrafluoroethylene is prepared through dispersing polymerization of tetrafluoroethylene in water with dispersant to produce primary particle of 0.1-0.4 micron and coagulating to form fine particle of several hundred microns. The fine particles consist of fiber clusters which are drawn into very fine filaments by mechanical forces, a process known as fiberization. The dispersed polytetrafluoroethylene has good fiber forming property, molecules are electrically neutral, the cohesive force among particles is low, molecular chains are arranged along the long sleeve direction of the particles under the action of small shearing force, and linear crystals are formed. Due to such fibrilization, a web structure having a considerable strength can be formed between the dispersed resin particles under the shearing force. The processing method used for dispersing the resin is to ensure that a certain shearing force is formed into a fiber structure and the fiber structure cannot be damaged. Articles of dispersed polytetrafluoroethylene are generally either green tape and microporous tape or thin-walled threads.
The crystallinity of the dispersed polytetrafluoroethylene is higher than that of the suspended polytetrafluoroethylene. The bending fatigue life of the dispersed polytetrafluoroethylene is 2300 times that of the suspended polytetrafluoroethylene. Therefore, the polytetrafluoroethylene used for manufacturing the stretched film is dispersed polytetrafluoroethylene powder, the crystallinity is more than or equal to 98 percent, and the molecular weight is 200-1000 ten thousand.
Therefore, the dispersed polytetrafluoroethylene and the suspended polytetrafluoroethylene have great difference from physicochemical properties, forming modes and application, and the two polytetrafluoroethylene cannot be mixed for use in the conventional cognition of the technical personnel in the field.
Because of the high inertness of polytetrafluoroethylene itself, compatibility with other polymers is poor, and surface treatment is required before modification or some specific components are added during modification to improve compatibility. However, even then, there is only a relative improvement in compatibility, and the modified polytetrafluoroethylene still has compatibility problems of varying degrees. The inventor of the present application, through intensive research, unexpectedly found that mixing and molding dispersed polytetrafluoroethylene and suspended polytetrafluoroethylene according to the process flow not only can dope two polytetrafluoroethylene materials with great differences to prepare fibers on the basis of the existing polytetrafluoroethylene fiber preparation process flow, but also more importantly, the prepared polytetrafluoroethylene fiber does not have any problem of compatibility while the surface roughness of the polytetrafluoroethylene fiber is greatly improved. Although the dispersed polytetrafluoroethylene and the suspended polytetrafluoroethylene are different from each other, the materials themselves are the same.
Furthermore, the adding amount of the lubricating oil in the preparation method is 26-28% of the weight of the dispersed polytetrafluoroethylene; in the total weight of the dispersed polytetrafluoroethylene and the suspended polytetrafluoroethylene, the weight ratio of the suspended polytetrafluoroethylene is 5-20%.
The inventor researches and discovers that if the doping amount of the suspended polytetrafluoroethylene is less than 5%, the surface average roughness of the prepared polytetrafluoroethylene fiber is less than 2 microns, the roughness can not be improved, and the effect is poor when the fiber is actually used as a dental floss; if the suspended polytetrafluoroethylene is doped above 20%, it is difficult or even completely impossible to stretch.
Further, in the preparation method, the SSG of the dispersed polytetrafluoroethylene is 2.130-2.180, and the extrusion pressure is 30-50 MPa under the condition that the compression ratio is 400; the SSG of the suspended polytetrafluoroethylene is 2.150-2.170, and the average grain diameter is 25-35 mu m.
Standard relative density (SSG) is a standard concept of ASTM, indirectly characterizing PTFE molecular weight. The larger the SSG value, the smaller the molecular weight; the smaller the SSG value, the larger the molecular weight. The relative density of a polytetrafluoroethylene specimen subjected to sampling, molding and heat treatment under the conditions specified in ASTM D1457 is referred to as "standard relative density".
The inventor researches and discovers that if the average grain diameter of the mixed suspended polytetrafluoroethylene is less than 25 mu m, the roughness of the surface of the prepared polytetrafluoroethylene fiber is not obvious, and Ra and Ry are both greatly reduced; if the average grain diameter of the mixed suspended polytetrafluoroethylene exceeds 35 mu m, burrs and cracks are easy to appear on the fiber in the stretching process of preparing the polytetrafluoroethylene fiber, and the strength and the toughness are sharply reduced.
Furthermore, in the preparation method of the polytetrafluoroethylene fiber with high surface roughness, the lubricating oil is isoparaffin solvent oil. Isopar M can be used as the isoparaffin solvent oil.
Isopar M is almost odorless, has narrow distillation range and has good surface compatibility. The distillation range of Isopar M is 225-254 ℃, flash point of 94 ℃ and density of 0.788g/cm 3 (15 ℃) and the viscosity is 3.57mm 2 At 25 ℃ C, the aromatic content is 0.01% and the surface tension is 27mN/m (25 ℃ C.).
Further, in the preparation method of the polytetrafluoroethylene fiber with high surface roughness, the curing temperature in the step (1) is 25-30 ℃, and the curing time is 15-20 h.
Furthermore, the compression ratio of the extrusion in the step (3) is 50-300, and the extrusion temperature is 55-65 ℃.
Furthermore, the temperature of the rolling in the step (3) is 40-80 ℃, and the speed of the rolling is 5-40 m/min.
Further, the deoiling temperature in the step (3) is 100-250 ℃.
Furthermore, the stretching temperature in the step (3) is 150-300 ℃, and the stretching magnification is 5-30 times.
Further, the slitting in the step (3) specifically comprises the following operations:
1) Cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 0.5-5 mm;
2) And carrying out secondary longitudinal stretching on the flat filament, wherein the temperature of the secondary longitudinal stretching is 200-350 ℃, and the multiple of the secondary longitudinal stretching is 5-30 times.
Further, the specific operation of relaxation heat setting in step (3) of the preparation method of the polytetrafluoroethylene fiber with high surface roughness is as follows: carrying out hot air heat setting on the secondary stretched flat filament;
wherein the heat setting temperature is 320-380 ℃ and the time is 0.5-3 min;
the feeding and winding rates are controlled, and the relaxation rate is kept between 2 and 20 percent.
Relaxation heat setting, namely, the feeding speed and the winding speed are controlled to ensure that the feeding speed is matched with the discharging speed, the relaxation rate is controlled, the fiber retracts to one part during heat setting, and the toughness of the fiber is improved. The fiber prepared from the doped mixture containing two different kinds of polytetrafluoroethylene, namely suspended polytetrafluoroethylene and dispersed polytetrafluoroethylene, is poor in toughness and easy to break, and the loose heat setting process is adopted in the heat setting process, so that the toughness of the fiber is effectively improved, and the elongation at break of the fiber can be improved by about 10%.
The polytetrafluoroethylene fiber prepared by the preparation method has average surface roughness Ra of more than 2 μm and/or maximum peak-valley height Ry of more than 15 μm.
Where Ra represents the average surface roughness, the average roughness or deviation from all points of the plane fitted to the surface of the test portion. Ry represents the maximum peak-to-valley height in the sample length determination, i.e., the absolute value between the highest peak and the lowest peak.
Furthermore, the strength of the polytetrafluoroethylene fiber is more than 3.3cN/dtex; elongation at break is greater than 10%; the linear density is 300 to 1000dtex.
In general, the polytetrafluoroethylene has low strength and poor wear resistance, but the polytetrafluoroethylene fiber disclosed by the invention not only has high surface roughness, but also has high strength and toughness, is wear-resistant and is not easy to break or fluff, and becomes an ideal material for manufacturing dental floss.
A dental floss is prepared from polytetrafluoroethylene fiber prepared by the above preparation method. The dental floss has surface roughness which is completely satisfactory for removing dental plaque attached to the surfaces of teeth and between teeth gaps, and is convenient for a user to operate. Meanwhile, the dental floss is wear-resistant and has no fluffy phenomenon.
The preparation method of the dental floss comprises the following steps: twisting 1-20 polytetrafluoroethylene fiber monofilaments by a twisting machine to form the polytetrafluoroethylene fiber monofilaments, wherein the twisting direction is S twist, the twist degree is 200-1000 twist/m, the feeding speed is 30-50 m/min, and finally, the twisted filaments are wound.
The invention has the beneficial effects that:
1. the preparation method is based on the existing polytetrafluoroethylene fiber preparation process flow, under the process conditions, the roughness of the polytetrafluoroethylene surface is obviously improved through the compounding cooperation between the dispersed polytetrafluoroethylene and the suspended polytetrafluoroethylene, a filler/particle additive with compatibility problem does not need to be added into the polytetrafluoroethylene fiber, or a particle coating is coated on the surface of the polytetrafluoroethylene fiber, so that the preparation method is more economical and simple.
2. Because the dispersion polytetrafluoroethylene and the suspension polytetrafluoroethylene are both polytetrafluoroethylene, the problem of compatibility does not exist between the dispersion polytetrafluoroethylene and the suspension polytetrafluoroethylene, and the natural bonding strength is far greater than that of the polytetrafluoroethylene and the inorganic/organic additive, so that the separation or falling-off phenomenon can not occur under the normal condition in the use process. Therefore, the invention fundamentally solves the problem of low combination degree caused by compatibility existing in the prior art of improving the surface roughness of the polytetrafluoroethylene fiber, and avoids additional damage of the additive to human body.
3. The addition of the suspended polytetrafluoroethylene also improves the overall toughness of the polytetrafluoroethylene fiber to a certain extent on the premise of ensuring the increase of the roughness.
Detailed Description
The technical solution of the present invention is explained in detail below.
Example 1
The preparation method of the polytetrafluoroethylene fiber with high surface roughness comprises the following specific steps:
(1) Mixing materials:
a. mixing dispersed polytetrafluoroethylene (SSG is 2.151, extrusion pressure is 42.3MPa under the compression ratio of 400) and assistant oil Isopar M, and curing at 25 ℃ for 16h to obtain a cured material; wherein the addition amount of the assistant oil Isopar M is 28wt percent of the mass of the dispersed polytetrafluoroethylene;
b. after curing, adding suspended polytetrafluoroethylene (SSG is 2.153, and the average particle size is 30.8 mu m) into the cured material obtained in the step a, and mixing in a three-dimensional mixer for 30min to obtain a mixture; wherein the mass ratio of the dispersed polytetrafluoroethylene to the suspended polytetrafluoroethylene is 80.
(2) Preforming, extruding, calendering and deoiling: prepressing the mixture to prepare a blank, extruding at the temperature of 60 ℃ and the compression ratio of 177, then calendering at the speed of 50 ℃ and 15m/min, and drying and deoiling at the temperature of 180 ℃ to obtain the deoiled calendered film.
(3) Stretching: the calendered film after deoiling was longitudinally stretched at 280 ℃ at a stretch ratio of 5 times.
(4) Slitting and secondary stretching:
cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 2mm by a coaxial blade cutting device;
and carrying out secondary longitudinal stretching on the slit flat filament, wherein the temperature of the secondary longitudinal stretching is 320 ℃, and the multiple of the secondary longitudinal stretching is 8 times.
(5) And (3) relaxation heat setting: and (3) carrying out hot air heat setting on the secondarily stretched flat filaments at 330 ℃ for 1min, controlling the feeding rate at 2m/min, controlling the winding rate at 1.8m/min, and keeping the relaxation rate at 10%.
The polytetrafluoroethylene fiber prepared by the preparation method is used for preparing dental floss: 5 polytetrafluoroethylene fiber monofilaments are twisted and formed through a twisting machine, the twisting direction is S twist, the twist degree is 500 twist/m, the feeding speed is 35m/min, and the twisted filaments are wound.
Example 2
The preparation method of the polytetrafluoroethylene fiber comprises the following specific steps:
(1) Mixing materials:
a. mixing dispersed polytetrafluoroethylene (SSG is 2.165, extrusion pressure is 37.3MPa under the compression ratio of 400) and assistant oil Isopar M, and curing at 25 ℃ for 16h to obtain a cured material; wherein the addition amount of the assistant oil Isopar M is 26wt% of the mass of the dispersed polytetrafluoroethylene;
b. after curing, adding suspended polytetrafluoroethylene (SSG is 2.164, and the average particle size is 27.1 mu m) into the cured material obtained in the step a, and mixing in a three-dimensional mixer for 30min to obtain a mixture; wherein the mass ratio of the dispersed polytetrafluoroethylene to the suspended polytetrafluoroethylene is 85 percent.
(2) Preforming, extruding, calendering and deoiling: prepressing the mixture to prepare a blank, extruding at the temperature of 60 ℃ and under the compression ratio of 100, then calendering at the speed of 60 ℃ and 20m/min, and drying and deoiling at the temperature of 200 ℃ to obtain the deoiled calendered film.
(3) Stretching: the calendered film after deoiling was longitudinally stretched at 300 ℃ at a stretch ratio of 6 times.
(4) Slitting and secondary stretching:
cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 2mm by a coaxial blade cutting device;
and carrying out secondary longitudinal stretching on the slit flat filament, wherein the temperature of the secondary longitudinal stretching is 340 ℃, and the multiple of the secondary longitudinal stretching is 10 times.
(5) And (3) relaxation heat setting: and (3) carrying out hot air heat setting on the secondarily-stretched flat filament at 320 ℃ for 1min, controlling the feeding rate at 2m/min and the winding rate at 1.85m/min, and keeping the relaxation rate at 7.5%.
The dental floss is prepared from the polytetrafluoroethylene fibers prepared by the preparation method: twisting 3 polytetrafluoroethylene fiber monofilaments by a twisting machine to form the polytetrafluoroethylene fiber monofilaments, wherein the twisting direction is S twist, the twist degree is 800 twist/m, the feeding speed is 40m/min, and the twisted filaments are wound.
Example 3
The preparation method of the polytetrafluoroethylene fiber comprises the following specific steps:
(1) Mixing materials:
a. mixing dispersed polytetrafluoroethylene (SSG is 2.157, extrusion pressure is 40.1MPa under the compression ratio of 400) and assistant oil Isopar M, and curing at 25 ℃ for 16h to obtain a cured material; wherein the addition amount of the assistant oil Isopar M is 28wt percent of the mass of the dispersed polytetrafluoroethylene;
b. after curing, adding suspended polytetrafluoroethylene (SSG is 2.153, and the average particle size is 32.7 mu m) into the cured material obtained in the step a, and mixing in a three-dimensional mixer for 30min to obtain a mixture; wherein the mass ratio of the dispersed polytetrafluoroethylene to the suspended polytetrafluoroethylene is 90.
(2) Preforming, extruding, calendering and deoiling: and prepressing the mixture to prepare a blank, extruding at the temperature of 60 ℃ and the compression ratio of 123, then calendering at the speed of 55 ℃ and 15m/min, and drying and deoiling at the temperature of 180 ℃ to obtain the deoiled calendered film.
(3) Stretching: the calendered film after deoiling was longitudinally stretched at 300 ℃ at a stretch ratio of 10 times.
(4) Slitting and secondary stretching:
cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 5mm by a coaxial blade cutting device;
and carrying out secondary longitudinal stretching on the slit flat filament, wherein the temperature of the secondary longitudinal stretching is 350 ℃, and the multiple of the secondary longitudinal stretching is 15 times.
(5) And (3) relaxation heat setting: and (3) carrying out hot air heat setting on the secondarily-stretched flat filament, wherein the heat setting temperature is 380 ℃, the time is 1min, the feeding rate is controlled at 2m/min, the winding rate is controlled at 1.7m/min, and the relaxation rate is kept at 15%.
The polytetrafluoroethylene fiber prepared by the preparation method is used for preparing dental floss: twisting 3 polytetrafluoroethylene fiber monofilaments by a twisting machine to form the polytetrafluoroethylene fiber monofilaments, wherein the twisting direction is S twist, the twist degree is 900 twist/m, the feeding speed is 45m/min, and the twisted filaments are wound.
Example 4
The preparation method of the polytetrafluoroethylene fiber comprises the following specific steps:
(1) Mixing materials:
a. mixing dispersed polytetrafluoroethylene (SSG is 2.165, extrusion pressure is 37.3MPa under the compression ratio of 400) and assistant oil Isopar M, and curing at 25 ℃ for 16h to obtain a cured material; wherein the addition amount of the assistant oil Isopar M is 26wt% of the mass of the dispersed polytetrafluoroethylene;
b. after curing, adding suspended polytetrafluoroethylene (SSG is 2.164, and the average particle size is 27.1 mu m) into the cured material obtained in the step a, and mixing in a three-dimensional mixer for 30min to obtain a mixture; wherein the mass ratio of the dispersed polytetrafluoroethylene to the suspended polytetrafluoroethylene is 95.
(2) Preforming, extruding, calendering and deoiling: prepressing the mixture to prepare a blank, extruding at the temperature of 60 ℃ under the compression ratio of 100, then calendering at the speed of 80 ℃ and 20m/min, and drying and deoiling at the temperature of 200 ℃ to obtain the deoiled calendered film.
(3) Stretching: the calendered film after deoiling was longitudinally stretched at 300 ℃ at a stretch ratio of 12 times.
(4) Slitting and secondary stretching:
cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 5mm by a coaxial blade cutting device;
and carrying out secondary longitudinal stretching on the slit flat filament, wherein the temperature of the secondary longitudinal stretching is 340 ℃, and the multiple of the secondary longitudinal stretching is 6 times.
(5) And (3) relaxation heat setting: and (3) carrying out hot air heat setting on the secondarily stretched flat filaments at 320 ℃ for 1min, controlling the feeding rate at 2m/min, controlling the winding rate at 1.85m/min, and keeping the relaxation rate at 7.5%.
The polytetrafluoroethylene fiber prepared by the preparation method is used for preparing dental floss: twisting 3 polytetrafluoroethylene fiber monofilaments by a twisting machine to form the polytetrafluoroethylene fiber monofilaments, wherein the twisting direction is S twist, the twist degree is 900 twist/m, the feeding speed is 45m/min, and the twisted filaments are wound.
Comparative example 1
The preparation process of comparative example 1 is otherwise the same as example 1 except that: suspension polytetrafluoroethylene is not added during material mixing in the step (1).
The method comprises the following specific steps:
(1) Mixing materials:
a. mixing dispersed polytetrafluoroethylene (SSG is 2.151, extrusion pressure is 42.3MPa under the compression ratio of 400) and assistant oil Isopar M, and curing at 25 ℃ for 16h to obtain a cured material; wherein the addition amount of the assistant oil Isopar M is 28wt percent of the mass of the dispersed polytetrafluoroethylene;
b. and c, after curing, placing the cured material in the step a in a three-dimensional mixer to mix for 30min to obtain a mixture.
As a result, it was found that the polytetrafluoroethylene fibers produced in this comparative example had smooth surfaces and low roughness.
Comparative example 2
Comparative example 2 was prepared by the same method as example 1 except that: and (2) during material mixing in the step (1), the mass ratio of the dispersed polytetrafluoroethylene to the suspended polytetrafluoroethylene in the step (b) is 60.
As a result, it was found that: in this comparative example, when the drawing in step (3) was carried out, the strength of the obtained deoiled and rolled film was too low to carry out the high-ratio drawing at all. It follows that when the amount of suspended polytetrafluoroethylene incorporated is too high, it is difficult or even impossible to stretch it.
Comparative example 3
Comparative example 3 was prepared according to the same method as example 1, except that: in the mixed material obtained in the step (1), the suspended polytetrafluoroethylene with SSG of 2.149 and particle size of 20.7 μm is selected.
As a result, it was found that the surface roughness of the polytetrafluoroethylene fibers obtained was not significant and Ra and Ry were both reduced because the particle size of the suspended polytetrafluoroethylene was too small.
Comparative example 4
Comparative example 4 was prepared by the same method as example 1 except that: in the mixed material obtained in the step (1), the suspended polytetrafluoroethylene with SSG of 2.144 and 42.1 mu m of grain size is selected.
As a result, it was found that the suspended polytetrafluoroethylene particles were too large to cause burrs and cracks during the stretching process. The strength and elongation at break are significantly reduced.
Comparative example 5
Comparative example 5 was prepared according to the same method as example 1, except that: and (2) mixing in the step (1) in different mixing sequences. The method comprises the following specific steps:
(1) Mixing materials:
firstly, dispersed polytetrafluoroethylene (SSG of 2.151, extrusion pressure of 42.3MPa at a compression ratio of 400) and suspended polytetrafluoroethylene (SSG of 2.153, average particle diameter of 30.8 μm) were added to a three-dimensional mixer at a mass ratio of 80 for 30min;
then, adding an auxiliary oil Isopar M into the mixed material for mixing, wherein the addition amount of the auxiliary oil Isopar M is 28wt% of the mass of the dispersed polytetrafluoroethylene;
finally, curing for 16h at 25 ℃ to obtain a mixture.
As a result, it was found that the dispersed polytetrafluoroethylene was significantly fiberized upon mixing, resulting in a lower final strength.
Comparative example 6
Comparative example 6 was prepared by the same method as example 1 except that: and (5) not performing relaxation heat setting, namely controlling the feeding speed of the heat setting to be the same as the winding speed, and straightening the fibers. The method comprises the following specific steps:
and (3) carrying out hot air heat setting on the secondarily-stretched flat filament, wherein the heat setting temperature is 330 ℃, the time is 1min, the feeding rate and the winding rate are both controlled at 2m/min, no relaxation rate exists, and no relaxation heat setting is carried out.
As a result, it was found that the elongation at break was significantly reduced and the toughness was decreased.
The properties of the polytetrafluoroethylene fibers obtained by the preparation methods described in examples 1 to 4 and comparative examples 1 to 6 were measured, and the detailed results are shown in Table 1.
All test properties were tests performed on monofilaments:
1. and (3) testing tensile property: the test is carried out according to GB/T14344-2008 test method for tensile properties of chemical fiber filaments.
2. And (3) testing the linear density: the test was carried out according to GB/T14343-2008 "test method for filament linear density of chemical fibers".
3. The tenacity of the fiber is compared by the elongation at break, and the higher the tenacity, the higher the elongation at break.
4. The surface roughness was measured by a Mitutoyo portable SJ-210 surface roughness tester.
TABLE 1 Performance index of the Polytetrafluoroethylene fibers
Claims (10)
1. A preparation method of polytetrafluoroethylene fibers with high surface roughness comprises the following steps:
(1) Mixing the dispersed polytetrafluoroethylene with lubricating oil, and curing; so as to obtain the cooked material, and then,
(2) Adding suspended polytetrafluoroethylene into the cured material obtained in the step (1) and mixing to obtain a mixture;
(3) And performing, extruding, rolling, deoiling, stretching, slitting and relaxing heat setting on the mixture to prepare the polytetrafluoroethylene fiber with high surface roughness.
2. The method for preparing polytetrafluoroethylene fiber with high surface roughness as claimed in claim 1, wherein the amount of the lubricating oil added is 26-28% of the weight of the dispersed polytetrafluoroethylene; in the total weight of the dispersed polytetrafluoroethylene and the suspended polytetrafluoroethylene, the weight ratio of the suspended polytetrafluoroethylene is 5-20%.
3. The method for preparing polytetrafluoroethylene fibers with high surface roughness according to claim 1, wherein the SSG of the dispersed polytetrafluoroethylene is 2.130 to 2.180, and the extrusion pressure is 30 to 50MPa under a compression ratio of 400; the SSG of the suspended polytetrafluoroethylene is 2.150-2.170, and the average grain diameter is 25-35 mu m.
4. The method for preparing polytetrafluoroethylene fibers with high surface roughness as set forth in claim 1 wherein the lubricating oil is isoparaffin solvent oil;
preferably, the lubricating oil is Isopar M.
5. The method for preparing polytetrafluoroethylene fibers with high surface roughness as set forth in claim 1, wherein the curing temperature in the step (1) is 25 to 30 ℃ and the curing time is 15 to 20 hours;
the compression ratio of the extrusion in the step (3) is 50-300, and the extrusion temperature is 55-65 ℃;
the temperature of the rolling in the step (3) is 40-80 ℃, and the speed of the rolling is 5-40 m/min;
the deoiling temperature in the step (3) is 100-250 ℃;
the stretching temperature in the step (3) is 150-300 ℃, and the stretching multiplying power is 5-30 times;
the specific operation of slitting in the step (3) is as follows:
1) Cutting the stretched polytetrafluoroethylene film into flat filaments with the width of 0.5-5 mm;
2) And carrying out secondary longitudinal stretching on the flat filament, wherein the temperature of the secondary longitudinal stretching is 200-350 ℃, and the multiple of the secondary longitudinal stretching is 5-30 times.
6. The method for preparing polytetrafluoroethylene fiber with high surface roughness as set forth in claim 1, wherein the relaxation heat setting in the step (3) is carried out by: carrying out hot air heat setting on the secondary stretched flat filament;
wherein the heat setting temperature is 320-380 ℃ and the time is 0.5-3 min;
the feeding and winding rates are controlled, and the relaxation rate is kept between 2 and 20 percent.
7. A polytetrafluoroethylene fiber produced according to the process of any of claims 1-6 wherein the fiber has an average surface roughness Ra > 2 μm and/or a maximum peak-to-valley height Ry > 15 μm.
8. The polytetrafluoroethylene fiber according to claim 7 wherein the fiber has a strength greater than 3.3cN/dtex; elongation at break is greater than 10%; the linear density is 300 to 1000dtex.
9. A dental floss, which is produced by using the polytetrafluoroethylene fiber produced by the production method according to any one of claims 1 to 6.
10. A method for preparing the dental floss of claim 9, wherein 1-20 filaments of the polytetrafluoroethylene fiber are twisted and formed by a twisting machine, the twisting direction is S twist, the twist degree is 200-1000 twist/m, the feeding speed is 30-50 m/min, and finally the twisted filaments are wound.
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