CN101670243A - Preparation method of polyethylene hollow fiber membrane with aperture in gradient distribution - Google Patents
Preparation method of polyethylene hollow fiber membrane with aperture in gradient distribution Download PDFInfo
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Abstract
The invention discloses a preparation method of polyethylene hollow fiber membrane with the aperture in gradient distribution, comprising the following steps: (1) adding material compositions, and fusing at the temperature from 160 DEG C to 250 DEG C to form homogeneous phase solution, wherein the material compositions comprise polyethylene and diluent which have thermal liquid-liquid separation points; (2) adopting a spinning machine to squeeze the homogeneous phase solution and spin to obtain hollow yarns, and cooling, solidifying and forming by gradients; (3) removing the diluent by an extraction process; and (4) carrying out tensioning thermoforming to the hollow yarns obtained in the step (3) to obtain the polyethylene hollow fiber membrane with the aperture in gradient distribution.The prepared polyethylene hollow fiber membrane has the characteristics of small surface aperture, large internal aperture, high porosity factor and high flux.
Description
(1) technical field
The present invention relates to the preparation method of polyethylene hollow fiber membrane that a kind of bore diameter gradient distributes, the polyethylene hollow fiber membrane that this bore diameter gradient distributes is suitable for household water filter, sewage disposal, middle water reuse and continuous microfiltration technology.
(2) technical background
Polyethene microporous membrane is a kind of membrane material of function excellence, is widely used in micro-filtration, sewage disposal, plasma separation, battery diaphragm etc.Polyethylene is a kind of high-crystallinity copolymer material, and its film-forming method mainly contains two classes, melt extrudes-pulling method and thermally induced phase separation.
Melt extrude-pulling method is that straight polymer melts body and melt extrudes, and melts to form manyly perpendicular to extruding the lamellar structure that direction is arranged in parallel in the body, in drawing process, lamellar structure is drawn back the formation micropore, then by the heat setting process fixation hole configurations.United States Patent (USP) 4401567 and 4530809 has been reported high density polyethylene (HDPE) (density＞0.965g/cm respectively
3) by melt extrude-drawing process prepares the macaroni yarn microporous barrier.Melt extruding the spinning draw ratio is 100-2000, at the following cold stretch 5-100% of room temperature (being lower than 40 ℃), passes through hot-stretch 100-900% under 80-125 ℃ of temperature then, and the maximum diameter of hole of film is 0.62 μ m, and porosity is 30-90%.United States Patent (USP) 42006/88 discloses the formation condition of this microcellular structure: melt index is that the high density polyethylene (HDPE) of 1-15g/min carries out melt spinning under the condition of draw ratio 1000-10000, the cold stretch rate of deformation of macaroni yarn can not be less than 50%/s, the temperature of hot-stretch is between 80-125 ℃, and total stretch rate is at 400-700%.United States Patent (USP) 5294338 discloses a kind of preparation method of wide-aperture hydrophilic polyethene hollow fiber membrane.Adopt earlier to melt extrude-pulling method prepares the macaroni yarn microporous barrier, then with ethylene-vinyl acetate or ethylene-vinyl alcohol surface hydrophilic modification or the cross-linking modified hydrophilic polyethene macaroni yarn microporous barrier for preparing of acrylamide.The average pore size of this film is 2-10 μ m, and porosity is 75-95%.
Thermally induced phase separation is thermoplasticity, crystalline high polymer and some high boiling micromolecular compound (diluent) (fusing point T that generally is higher than crystalline polymer under the rising temperature
m) form homogeneous phase solution, reduce temperature solid-liquid or liquid-liquid phase separation take place again, remove diluent then and form polymer microporous material, micropore is to be formed being removed the back by the shared position of diluent.United States Patent (USP) 4020230 early discloses polyethylene and the fusion of low-molecular-weight ester type high temp makes the thread goods of hollow, the ester class as diluent is extracted obtain polyethylene macaroni yarn microporous barrier again, and the maximum diameter of hole can reach
United States Patent (USP) 4247498 has reported that 27 kinds of energy and polyethylene form the diluent of homogeneous phase solution, provide more system for thermally induced phase separation prepares polyethylene film.United States Patent (USP) 4867881 and 5238618 all adopts HDPE and DOP system melt blending, adopts double screw extruder to extrude with 18Kg/hr speed and makes the strip flat sheet membrane, with the cold water quenching system is separated then.Extractant is with 1,1, the 1-trichloroethanes, and final drying is removed extractant and is carried out axial tension, and along with the increase of level of stretch, film thickness and Gurley value reduce, and aperture, porosity and matrix hot strength increase.
From above-mentioned patent report, melt extrude-condition that pulling method prepares polyethylene hollow fiber membrane is relatively harsher, to the requirement height of raw material, and the process more complicated, be not easy to continued operation.And thermally induced phase separation needs the parameter controlled few in forming process, stable and the continued operation of easier realization, but existing technology can only obtain the polyethylene hollow fiber membrane that the aperture is symmetrically distributed, and can't directly prepare the resistant to pollution polyethylene hollow fiber membrane that bore diameter gradient distributes.The problem that exists is, though existing polyethylene film flux is big, owing to membrane aperture is big, film hold back weak effect.In addition on the one hand, post processing means such as the general using plasma radiation of hydrophilic modification of existing polyethylene film, chemical graft, surface-coated are improved the anti-fouling performance of membrane material at present.These post-processing approach equipment and process complexity, effect is not good enough.
(3) summary of the invention
The present invention is directed to big flux, the low contradiction of holding back efficient that existing polyethylene film material exists, the preparation method of polyethylene hollow fiber membrane that provides a kind of bore diameter gradient to distribute, this polyethylene hollow fiber membrane have inner large aperture, surperficial small-bore, high porosity and high-throughout characteristics.
For solving the problems of the technologies described above, the present invention adopts following technical scheme:
The preparation method of polyethylene hollow fiber membrane that a kind of bore diameter gradient distributes comprises the steps:
(1) add feedstock composition, 160～250 ℃ of fusions become homogeneous phase solution; Described feedstock composition comprises polyethylene and diluent, and described polyethylene and diluent have thermic liquid-liquid phase separation point;
(2) adopt spinning-drawing machine, described spinning-drawing machine comprises spinning box and spinning head, establishes air supply pipe in the spinning head, logical nitrogen in the tracheae; Nitrogen pressure is that 0.1～0.5MPa, spinning box temperature are 120～200 ℃ in the control air supply pipe, the described homogeneous phase solution of step (1) is fed spinning box obtain macaroni yarn through the spinning head extruding spinning, behind the air clearance of described macaroni yarn through 5～300mm of one section controllable temperature, in 10～50 ℃ of water-baths, cool off and the also curing molding that is separated, control the air of described nitrogen, controllable temperature and the temperature of water-bath respectively, make the air of described nitrogen, controllable temperature and the adjacent in twos thermograde of water-bath have a thermograde at least more than 20 ℃; Promptly control aforementioned three's temperature, make the poor of the air themperature of the difference of air themperature of nitrogen temperature and controllable temperature or controllable temperature and bath temperature, have a temperature difference among both at least more than 20 ℃, such temperature difference, the bore diameter gradient that helps in the polyethylene hollow fiber membrane distributes.Preferred 5～the 200nm of the distance of air clearance.
(3) will remove diluent by extraction process through the macaroni yarn of water-bath and curing molding; Described extraction process comprises: macaroni yarn is soaked in extracts diluent in the extractant, and the extractant drying is carried out in the macaroni yarn taking-up, the dry anxiety extraction drying that adopts of described extractant;
(4) macaroni yarn that step (3) is obtained carries out nervous thermal finalization, promptly obtains the polyethylene hollow fiber membrane that described bore diameter gradient distributes.
Below above-mentioned technology is done and specified.
In the step (1), comprise polyethylene and diluent in the feedstock composition that the present invention uses, the polyvinyl resin that the present invention uses comprises low density polyethylene (LDPE) (LDPE), high density polyethylene (HDPE) (HDPE), ultra-high molecular weight polyethylene (UHMW-PE), preferred use highdensity polyvinyl resin because such resin have must characteristic as it high strength.
At thermally induced phase separation, judge whether a kind of solvent is suitable as diluent, mainly investigate it and whether can more than the fusing point of polymer, evenly form homogeneous phase solution and whether have thermic liquid-liquid phase separation point with mixed with polymers.If diluent has thermic liquid-liquid phase separation point, when being cooled after the feedstock composition fusion of being made up of polymer-diluent forms homogeneous phase solution, system can be carried out the thermic liquid-liquid phase separation under the temperature that is not less than the polyethylene crystallization temperature.The solvent that the present invention preferably has thermic liquid-liquid phase separation point with polyvinyl resin more preferably has the non-volatile solvents of thermic liquid-liquid phase separation point as diluent with polyvinyl resin as diluent.When if diluent does not have thermic liquid-liquid phase separation point when mixing with polyvinyl resin, be difficult to obtain microporous barrier all satisfied aspect permeation flux and intensity two.
Whether polymer and diluent have thermic liquid-liquid phase separation point, can measure by the following method:
Measure first method of thermic liquid-liquid phase separation point, polymer and diluent place beaker respectively according to predetermined concentration proportioning, put into the baking oven that is heated to 150 ℃ in advance then, be warmed up to 220 ℃ again, and stir with glass bar and to make its even mixing, then blend melt is taken out from baking oven, cooling at room temperature obtains sample.With blade sample is thinly sliced, be placed between two slides, the slide that sample will be housed then is placed on the micro melting point apparatus warm table, be warming up to 220 ℃ of coolings again, observe in the cooling procedure cloud point and write down corresponding temperature, so the temperature when the thermic liquid-liquid phase separation is put available cloud point and occurred is estimated.
Measure second method of thermic liquid-liquid phase separation point, under enough temperature and in the time with simple screw rod kneading device, the feedstock composition melt kneading that to form by predetermined ratio by polymer and diluent of Haake flow graph for example, when continuing screw rod kneading,, estimate the variation of mediating moment of torsion with the composition cools of mediating.According to this method, the temperature that the thermic liquid-liquid phase separation is put when the kneading moment of torsion reduces rapidly in the available cooling procedure is estimated.For mediating the degree that moment of torsion reduces, the inventor studies show that, with respect to the torque value before reducing, mediate moment of torsion reduce about 10% or temperature more for a long time can think the liquid-liquid phase separation point.But the absolute value of mediating moment of torsion is unimportant at this, because it is subjected to the influence of resin viscosity, diluent viscosity, polymer concentration and kneaded material compaction in the screw rod kneading container.
According to mentioned above principle, the diluent that the present invention is suitable for comprises: a kind of or several combination arbitrarily in aliphatic acid low-carbon-ester (as fatty acid methyl ester, fatty-acid ethyl ester, aliphatic acid propyl ester etc.), aliphatic acid high alcohol ester (as fatty glyceride, aliphatic acid C4-12 alcohol ester etc.), phthalic acid low-carbon-ester (as dibutyl phthalate), the phthalic acid high alcohol ester (as two certain herbaceous plants with big flowers esters, phthalic acid diiso decyl ester, di-n-octyl phthalate) etc.Described aliphatic acid comprises: vegetable fatty acids, soya fatty acid, rape oil fatty acid, palm oil fatty acid, coco-nut oil fatty acid, animal oil fatty acid, a kind of or several combination arbitrarily in the fatty acid mixed etc.
About the polyethylene that uses among the present invention and the ratio of diluent, as long as the feedstock composition that obtains has thermic liquid-liquid phase separation point, and each ratio can prepare homogeneous phase solution and be enough to form hollow thread under the kneading temperature that reality adopts, and any ratio all can adopt.In general, based on polyethylene and diluent, poly weight fraction is at 20～50wt%, when the part by weight of polyvinyl resin less than 20%, the macaroni yarn film strength will reduce, this is undesirable.On the other hand, when the part by weight of polyvinyl resin greater than 50%, make the hollow fiber membrane that has than macroporous structure and become very difficult, cause permeation flux to reduce.
The present invention recommends to comprise following polyvinyl resin and diluent in the feedstock composition: the 1. phthalic acid diiso decyl ester of the polyethylene of 20～50wt% and 50～80wt%, 2. the fatty acid ester of the polyethylene of 20～45wt% and 55～80wt%, the 3. di-n-octyl phthalate of the polyethylene of 20～50wt% and 50～80wt%.Above weight fraction is based on polyvinyl resin and diluent meter.Described fatty acid ester is a kind of in aliphatic acid low-carbon-ester, the aliphatic acid high alcohol ester or several arbitrarily arbitrarily than mixture.
Further, well-known, polarity, electric charge, the topological structure on the pollution problem of film and membrane material surface have confidential relation.The compatible ethylene copolymer of selection of the present invention and polyethylene adds ethylene copolymer as alloying agent in feedstock composition, make the microporous barrier that makes have the little and hydrophily characteristics of resistance, improves the anti-pollution ability of film.Described ethylene copolymer, optimal ethylene-vinyl alcohol (EVOH), ethene-glycol copolymer (PEEG), ethylene-acrylic acid copolymer (PEA) etc.In the described feedstock composition, the weight of ethylene copolymer is recommended as 0～40wt% of polyethylene and diluent gross weight, preferred 5～25wt%.
Among the present invention, only otherwise offset the advantage that obtains from the present invention, can in feedstock composition, add additive according to purpose, as antioxidant, nucleator etc.Described antioxidant can be 2,6-BHT, butylated hydroxy anisole, n-propyl gallate etc., and the content of antioxidant is generally at 0.5～5wt%; Described nucleator can be phosphate ester salt, glucitols etc., and the content of nucleator is generally at 0.25～5wt%.Above weight fraction is that the gross weight in polyvinyl resin and diluent is 100%.
The present invention is after becoming homogeneous phase solution with the feedstock composition high-temperature fusion, adopt spinning-drawing machine with the homogeneous phase solution extruding spinning, the spinning head of spinning-drawing machine adopts the used spinning head type of preparation macaroni yarn usually, the hollow spinning head has the bushing type spinning head of air feed (liquid) pipe in being, the logical nitrogen (core liquid) of central gas-supply (liquid) pipe, pressure is 10～100cm water column.The present invention specifically can carry out extruding spinning by following technology: nitrogen pressure is 0.1～0.5MPa in the control air supply pipe, the spinning box temperature is 120～200 ℃ (best spinning temperature is 130～180 ℃), homogeneous phase solution is obtained macaroni yarn through the spinning head extruding spinning, macaroni yarn is through one section air clearance, cooling and be separated and make the macaroni yarn curing molding in 10～50 ℃ of water-baths then, the air themperature and the bath temperature of control air clearance, make the difference of the difference of air themperature of nitrogen temperature and air clearance and air clearance and bath temperature in the two one of them temperature difference more than 20 ℃.In general, the nitrogen that passes through in the spinning head can obtain higher temperature through the heating of spinning head and homogeneous phase solution.The present invention make the outer surface generation cooling earlier or the outer surface cooldown rate of macaroni yarn be higher than inner surface, thereby the gradient that realizes the aperture distributes by macaroni yarn being carried out above-mentioned gradient cooling.
Behind step (2) macaroni yarn curing molding, for the degree of orientation and the permeation flux that improves macaroni yarn, preferred elder generation adopts continuously elongated technology to the macaroni yarn behind the curing molding, and then removes diluent by the extraction process of step (3).It is 40～80 ℃ that the present invention recommends continuously elongated temperature, and draw ratio is between 100～250%.
Macaroni yarn through after the moulding of step (2) gradient cooling curing or through above-mentioned continuously elongated after, need to adopt extraction process to remove diluent.Extraction process comprises extraction diluent and the dry two parts of extractant among the present invention.
The extraction diluent is about to macaroni yarn and is soaked in the container that is full of extractant, fully washes extractant with water after the extraction.Preferably repeatedly soak and wash,, can reduce quantity of solvent remaining in the micropore because repeat like this.The general extractant that uses is a poor solvent for polyvinyl resin, is good solvent for diluent, and has the boiling point that is lower than the hollow fiber membrane fusing point.The extractant that the present invention uses comprises pentane, isopropyl alcohol, n-hexane, normal heptane, cyclohexane, ethanol, methyl alcohol, isopropyl alcohol, carrene, oxolane, toluene etc.In addition, for the solvent of giving an example above, consider that from environment availability, safety and health angle alcohols is proper.
First method of extractant drying, promptly nervous extraction is dry, and macaroni yarn takes out from water-bath extracting completely, shrinks in the process of drying for preventing silk, needs promptly two of silk to be fixed room temperature or hot-air drying.Second method of extractant drying, promptly free dry, precursor takes out from water-bath extracting completely, silk is not imposed any restrictions, and makes silk free dry under room temperature or hot-air condition.The present invention preferably uses nervous extraction dry.
The present invention also carries out the described nervous thermal finalization of step (4) to the macaroni yarn that obtains after step (3) extraction process.Described nervous thermal finalization is to keep draw ratio or macaroni yarn is being fixed in stretching, extension, heat-treats when making silk present extended configuration.Nervous thermal finalization can be removed the residual stress and strain that produces in the stretching process, can also improve the degree of crystallinity of film, makes film have better spatial stability, and the suitable control permeability function of (representing with porosity and permeation flux) is arranged.The present invention recommends nervous heat setting temperature to be controlled at 100～125 ℃, shaping time 5～45min.
The polyethylene hollow fiber membrane that the present invention makes has the strong advantage of anti-pollution, high porosity, low-pressure high-throughput, good toughness, resistance to acids and bases and oxidation resistance.The average pore size 0.1-0.6 μ m of film, porosity＞50%, air penetrability＞0.12cm
3/ cm
2ScmHg, permeability rate＞1.3m
3/ m
2Hr.Membrane material anti-pollution ability in long-term use can not decay.
Compared with prior art, beneficial effect of the present invention is:
A) the present invention is by adopting the gradient cooling method, and gradient is bigger, makes the polyethylene hollow fiber membrane that makes keep high voidage and high-throughout while, and bore diameter gradient distributes, and there is the good effect of holding back inner large aperture, surperficial small-bore.
B) the present invention has the little and hydrophily characteristics of resistance by adding ethylene copolymer in feedstock composition, make the hollow fiber membrane that makes, and has improved the anti-pollution ability of film.
C) the present invention has adopted nervous thermal finalization behind extraction process, can remove the residual stress and strain that produces in the stretching process, can also improve the degree of crystallinity of film, make film have better spatial stability, the suitable control permeability function of (representing with porosity and permeation flux) is arranged.
D) the present invention has adopted continuously elongated technology at extraction process, has effectively improved air flux, aperture and the porosity of hollow fiber membrane.
(4) description of drawings
Fig. 1 shows the polymer-diluent system moment of torsion and the temperature relation of reference example 1, and this system has thermic liquid-liquid phase separation point, is used for the present invention.
Fig. 2 shows the polymer-diluent system moment of torsion and the temperature relation of reference example 3, and this system does not have thermic liquid-liquid phase separation point.
Fig. 3 is a self-control device for spinning schematic diagram of the present invention.1, nitrogen cylinder; 2, agitating device; 3, spinning box; 4, spinning head; 5, the water-bath coagulating bath; 6, wrap-up; 7, water-bath; 8, stretching device.
Fig. 4 is the typical polyethylene hollow fiber membrane surface scan Electronic Speculum figure of the embodiment of the invention 7 preparations.
(5) specific embodiment
Illustrate in greater detail below in conjunction with hereinafter specific embodiment, but described embodiment is not construed as limiting the invention.
Experimental technique among the embodiment is described as follows:
(1) thermic liquid-liquid phase separation point
To add in the Haake flow graph by the feedstock composition that contains polyvinyl resin, diluent, additive that predetermined ratio is formed, and under predetermined temperature with screw speed fusion-kneading of 40rpm.At this moment, though select time is arbitrarily considered preferred 10～15 minutes from the stability of mediating moment of torsion and the decomposition of prevention resin and the angle of damage.Then, when continuing screw rod kneading, close the cooling of heater air,, obtain an indicatrix to measure the correlation of mediating temperature and mediating moment of torsion.In indicatrix, mediate moment of torsion and be regarded as flex point because of liquid-liquid phase separation, and be called as thermic liquid-liquid phase separation point with the temperature of cooling off rapid decline part.
(2) physical dimension of film
Film length is measured with rule, and external diameter and wall thickness adopt the light microscope of band scale to measure in the film.
(3) porosity
Choose several sections uniform hollow fiber membranes, under the light microscope of band scale, measure its internal diameter and external diameter, average and calculate the volume V of certain-length film
Always, and the film dry weight W that claims with electrooptical balance
Do, the density p of polymer
RealFor known.Its porosity is calculated formula:
(4) air flux
The air flux of film is used under certain pressure, the nitrogen volume characterization that the unit interval unit are sees through.Detect the flow of infiltration gas with homemade gas flowmeter.Formula:
J
g: nitrogen air flux (cm
3/ cm
2ScmHg) L: filament length degree (cm)
V: nitrogen volume (cm
3) D
nFor: the silk outer diameter D
1And inside diameter D
2(cm)
P: test pressure (cmHg) t: testing time (s)
(5) average pore size
Adopt the filtering velocity method to measure the aperture of film, its formula that calculates the film average pore size is:
μ: the viscosity of nitrogen (Pas) 0.000163 d: the thickness of film (mm)
J
g: air flux (cm
3/ cm
2SPa) P
r: the porosity of film
(6) microporous barrier surface texture
Hollow fiber membrane is fixed on the sample platform; Gold-plated in cathode vacuum sputter device; The sample that makes is sent into the electron microscopic sample sight chamber, the different parts of sample is observed taken pictures.ESEM model: Hitachi S-4700 (II)
Reference example 1
With 18g high density polyethylene (HDPE) (Qilu Petrochemical J7000), the 42g di-n-octyl phthalate mixes, and adds in the Haake flow graph, under 185 ℃ with the screw speed fusion of 40rpm-kneadings 15 minutes, to temperature with mediate moment of torsion and stablize.Then, when continuing screw rod kneading, close heater composition is cooled to 100 ℃ from 180 ℃ of air, can observe and mediate the variation that moment of torsion reduces with temperature, therefore assess mechanism of separate.In the indicatrix that from Fig. 1, shows, can find out that the thermic liquid-liquid phase separation point of above-mentioned composition is 118 ℃.
Reference example 2
According to reference example 1 described same method assessment mechanisms of phase separation, except mixing with high density polyethylene (HDPE) described in the reference example 1 of 21g and 39g n-butyl phthalate, other are with reference example 1.The thermic liquid-liquid phase separation point that found that the composition that obtains is 116 ℃.
Reference example 3
According to the described same method assessment of reference example 1 mechanisms of phase separation, except being diluent with the 42g atoleine and temperature is set at 180 ℃ that other are with reference example 1.In the indicatrix that from Fig. 2, shows, can find out that above-mentioned composition does not have thermoinduction liquid-liquid phase separation point.
Embodiment 1
With 2 of the high density polyethylene (HDPE) (Qilu Petrochemical J7000) of 30wt%, 70wt% di-n-octyl phthalate, 0.5wt%, 6-BHT antioxidant (based on the gross weight of high density polyethylene (HDPE) and di-n-octyl phthalate), 185 ℃ of fusions become homogeneous phase solution, controlled pressure 0.20MPa, by the self-control spinning-drawing machine homogeneous phase solution extruding spinning is obtained macaroni yarn under 145 ℃, spinning head adopts the used spinning head type of preparation macaroni yarn usually.The hollow spinning head has the bushing type spinning head of air supply pipe in being, the central gas-supply pipe leads to nitrogen, and pressure is the 20cm water column, and nitrogen is 80 ℃ after the homogeneous phase solution heating.Macaroni yarn is earlier through the 10cm air clearance, 35 ℃ of air themperatures, quenching and be separated and make the macaroni yarn curing molding in 50 ℃ of water-baths then.The hollow precursor is immersed in the pentane, removes di-n-octyl phthalate, nervous subsequently fixing dry.At last film is carried out obtaining polyethylene hollow fiber membrane at 105 ℃ of nervous thermal finalization 30min.The performance of film is shown in Table 1, and the polyethylene cortina surface apertures that obtains of the present invention is significantly less than average pore size as can be seen from the table, means that membrane material possesses the good effect of holding back when keeping big flux lower resistance.
According to embodiment 1 in identical method, except before extraction process, having added continuously elongated technology.Draft temperature is 50 ℃, and draw ratio is 125%.The performance of film is as shown in table 1, and obviously improve in air flux and aperture.
Embodiment 3
According to embodiment 1 in identical method, except before extraction process, having added continuously elongated technology.Draft temperature is 50 ℃, and draw ratio is 145%.The performance of film is as shown in table 1, and the hollow fiber membrane that obtains has very high air flux, bigger aperture and porosity.
High density polyethylene (HDPE) (Qilu Petrochemical J7000) with 25wt%, (the auspicious chemical industry of Shandong occasion Co., Ltd produces the fatty acid methyl ester of the EVOH of 5wt% (ethylene-vinyl alcohol copolymer) and 70wt%, production code member is 9050014386) mix, 0.5% 2,6-BHT antioxidant is (based on high density polyethylene (HDPE), the gross weight of EVOH and fatty acid methyl ester), 185 ℃ of fusions become homogeneous phase solution, controlled pressure 0.25MPa, by the self-control spinning-drawing machine homogeneous phase solution extruding spinning is obtained macaroni yarn under 145 ℃, spinning head adopts the used spinning head type of preparation macaroni yarn usually.The hollow spinning head has the bushing type spinning head of air supply pipe in being, the central gas-supply pipe leads to nitrogen, and pressure is the 20cm water column, and nitrogen is 80 ℃ after the homogeneous phase solution heating.Macaroni yarn is earlier through the 10cm air clearance, 40 ℃ of air themperatures, quenching and be separated and make the macaroni yarn curing molding in 50 ℃ of water-baths then.For the degree of orientation and the permeation flux that improves macaroni yarn, the macaroni yarn behind the curing molding is carried out continuously elongated, draft temperature is 50 ℃, draw ratio is 145%.Again the hollow precursor that obtains is immersed in the ethanol, removes fatty acid methyl ester, nervous subsequently fixing dry.At last film is carried out nervous thermal finalization and obtain polyethylene hollow fiber membrane.The performance of film is shown in Table 1.
Embodiment 5
According to embodiment 4 in identical method, except replacing ethanol as extractant by cyclohexane.Because cyclohexane give is that extractant makes the relative shrinkage ratio of film bigger, as shown in table 1, the hollow fiber membrane air flux that obtains is all relative with the aperture less.
(the auspicious chemical industry of Shandong occasion Co., Ltd produces with the high density polyethylene (HDPE) (Qilu Petrochemical J7000) of 35wt%, the PEEG (ethene-glycol copolymer) of 5wt% and the fatty acid methyl ester of 60wt%, production code member: 9050014386) mix, 1% 2,6-BHT antioxidant (based on feedstock composition), 185 ℃ of fusions become homogeneous phase solution, controlled pressure 0.25MPa, by the self-control spinning-drawing machine homogeneous phase solution extruding spinning is obtained macaroni yarn under 145 ℃, spinning head adopts the used spinning head type of preparation macaroni yarn usually.The hollow spinning head has the bushing type spinning head of air supply pipe in being, the central gas-supply pipe leads to nitrogen, and pressure is the 20cm water column, and nitrogen is 107 ℃ after the homogeneous phase solution heating.Earlier through the 10cm air clearance, air themperature is 35 ℃ to macaroni yarn, then quenching and be separated and make the macaroni yarn curing molding in 50 ℃ of water-baths.For the degree of orientation and the permeation flux that improves macaroni yarn, again the macaroni yarn behind the curing molding is carried out continuously elongatedly, draft temperature is 50 ℃, draw ratio is 145%.The hollow precursor that obtains is immersed in the isopropyl alcohol, removes fatty acid butyl ester, nervous subsequently fixing dry.At last film is obtained polyethylene hollow fiber membrane at 105 ℃ of nervous thermal finalization 30min.The performance of film is shown in Table 1.
Embodiment 7
High density polyethylene (HDPE) (Qilu Petrochemical J7000) and 5wt% ethylene/acrylic acid copolymer (EAA with 25wt%, Canada's dust restrains loose EP70), 70wt% di-n-octyl phthalate, 1wt% 2,6-BHT antioxidant, 185 ℃ of fusions become homogeneous phase solution, controlled pressure 0.25MPa, by the self-control spinning-drawing machine homogeneous phase solution extruding spinning is obtained macaroni yarn under 145 ℃, spinning head adopts the used spinning head type of preparation macaroni yarn usually.The hollow spinning head has the bushing type spinning head of air supply pipe in being, the central gas-supply pipe leads to nitrogen, and pressure is the 22cm water column, and nitrogen is 105 ℃ after the homogeneous phase solution heating.Earlier through the 10cm air clearance, air themperature is 40 ℃ to macaroni yarn, then quenching and be separated and make the macaroni yarn curing molding in 50 ℃ of water-baths.For the degree of orientation and the permeation flux that improves macaroni yarn, again the macaroni yarn behind the curing molding is carried out continuously elongatedly, draft temperature is 50 ℃, draw ratio is 145%.The hollow precursor that obtains is immersed in the n-hexane, removes di-n-octyl phthalate, nervous subsequently fixing dry.At last film is obtained polyethylene hollow fiber membrane at 105 ℃ of nervous thermal finalization 30min.The performance of film is shown in Table 2.
The comparative example 1
Except nervous fixedly drying among the embodiment 4 is become the free drying, according to embodiment 4 in identical method, the film properties that obtains is shown in Table 1.
The comparative example 2
With the high density polyethylene (HDPE) (Qilu Petrochemical J7000) of 40wt%, the atoleine of 60wt% (letter sound chemical plant, Jiangsu produces) mix, 0.5wt% 2,6-BHT antioxidant, 180 ℃ of fusions become homogeneous phase solution, control spinning box pressure is 0.20MPa, by the self-control spinning-drawing machine homogeneous phase solution extruding spinning is obtained macaroni yarn under 125 ℃, spinning head adopts the used spinning head type of preparation macaroni yarn usually.The hollow spinning head has the bushing type spinning head of air supply pipe in being, the central gas-supply pipe leads to nitrogen, and pressure is the 20cm water column.Macaroni yarn is earlier through the 10cm air clearance, then quenching and be separated and make the macaroni yarn curing molding in 50 ℃ of water-baths.The degree of orientation and permeation flux in order to improve macaroni yarn carry out continuously elongated technology to the hollow precursor again, and draft temperature is 50 ℃, and draw ratio is 133%.The hollow precursor is immersed in the pentane, removes white oil, nervous subsequently fixing dry.At last film is obtained polyethylene hollow fiber membrane at 105 ℃ of nervous thermal finalization 30min.Because high density polyethylene (HDPE)-atoleine system do not have thermoinduction liquid-liquid phase separation point, as shown in table 1 in, the average pore size of the hollow fiber membrane that obtains is compared much smaller with air flux with embodiment 6.
The performance parameter of membrane material among table 1 embodiment 1-6 and the comparative example 1-2
Table 2 embodiment 7 membrane material characteristic parameters
Claims (10)
1, a kind of preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution comprises the steps:
(1) adds feedstock composition, become homogeneous phase solution 160～250 ℃ of fusions; Described feedstock composition comprises polyethylene and diluent, and described polyethylene and diluent have thermic liquid-liquid phase separation point;
(2) adopt spinning-drawing machine, described spinning-drawing machine comprises spinning box and spinning head, establishes air supply pipe in the spinning head, logical nitrogen in the air supply pipe; Nitrogen pressure is that 0.1～0.5MPa, spinning box temperature are 120～200 ℃ in the control tracheae, the described homogeneous phase solution of step (1) is fed spinning box to be extruded through spinning head, obtain macaroni yarn, behind the air clearance of described macaroni yarn through 5～300mm of one section controllable temperature, in 10～50 ℃ of water-baths, cool off and the also curing molding that is separated, control the air of described nitrogen, controllable temperature and the temperature of water-bath respectively, make the air of described nitrogen, controllable temperature and the adjacent in twos thermograde of water-bath have a gradient at least more than 20 ℃;
(3) will remove diluent by extraction process through the macaroni yarn of water-bath and curing molding; Described extraction process comprises macaroni yarn is soaked in the extractant to take out behind the extraction diluent and carries out the extractant drying that described extractant is dry to adopt nervous extraction dry;
(4) macaroni yarn that step (3) is obtained carries out nervous thermal finalization, promptly obtains the polyethylene hollow fiber membrane that described bore diameter gradient distributes.
2, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 1 is characterized in that also comprising in the described feedstock composition ethylene copolymer.
3, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 2 is characterized in that described ethylene copolymer is ethylene-vinyl alcohol, ethene-glycol copolymer or ethylene-acrylic acid copolymer.
4, the preparation method of polyethylene hollow fiber membrane that distributes as the described bore diameter gradient of one of claim 1～3 is characterized in that earlier the macaroni yarn of curing molding being carried out before in step (3) continuously elongated, and then removes diluent by extraction process.
5, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 4, it is characterized in that described continuously elongated process conditions are: draft temperature is 40～80 ℃, and draw ratio is 100～250%.
6, the preparation method of polyethylene hollow fiber membrane that distributes as the described bore diameter gradient of one of claim 1～3 is characterized in that described polyethylene is low density polyethylene (LDPE) or high density polyethylene (HDPE).
7, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 1 is characterized in that described diluent is the one or any several combination in aliphatic acid low-carbon-ester, aliphatic acid high alcohol ester, phthalic acid low-carbon-ester, the phthalic acid high alcohol ester.
8, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 1 is characterized in that in the described feedstock composition that based on described polyethylene and diluent, poly weight fraction is 20～50wt%.
9, the preparation method of polyethylene hollow fiber membrane of bore diameter gradient distribution as claimed in claim 8 is characterized in that described feedstock composition also comprises ethylene copolymer, and the weight of described ethylene copolymer is 0～40wt% of polyethylene and diluent gross weight.
10, the preparation method of polyethylene hollow fiber membrane that distributes as the described bore diameter gradient of one of claim 1～3, it is one of following to it is characterized in that described extractant is selected from: pentane, isopropyl alcohol, n-hexane, normal heptane, cyclohexane, ethanol, methyl alcohol, isopropyl alcohol, carrene, oxolane, toluene.
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