CN102875711B - Condensing washing method of polyvinylidene fluoride emulsion - Google Patents
Condensing washing method of polyvinylidene fluoride emulsion Download PDFInfo
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Abstract
The invention relates to a condensing washing method of polyvinylidene fluoride emulsion. The condensing washing method comprises the steps as follows: (1) adding water at 1 to 15 DEG C to polyvinylidene fluoride emulsion; adjusting specific gravity of emulsion to value between 1.04 and 1.18; (2) condensing the polyvinylidene fluoride emulsion obtained in an agitating mode; controlling the agitating speed to 500 to 2000 rotation per minute; completely demulsifying for 1 to 15 minutes; and (3) washing the separated polyvinylidene fluoride emulsion resin after condensing with water. According to the condensing washing method provided by the invention, the production capacity of equipment is greatly improved, water consumption is reduced, the processing period is shortened, and the benefit is brought to the scale industrial production.
Description
Technical field
The present invention relates to the aftertreatment field of polymer emulsion, particularly, relate to a kind of cohesion washing methods of polyvinylidene difluoride (PVDF) emulsion.
Background technology
Polyvinylidene difluoride (PVDF) (PVDF) has remarkable physical strength, shock-resistant, radiation resistance, water-fast and chemicals-resistant, the performance such as weather-proof, and has that piezo-electric modulus is large, refractive index is low, frequency response is wide, low resistance easily mates feature.Long term operation temperature-50 ~ 150 ℃, available general thermoplastics processing method processing.Its outstanding feature is that mechanical property is high, has good chemical stability.Polyvinylidene difluoride (PVDF) is by a large number for the manufacture of various electric wires, chemical industry pipe fitting, container conduit lining, weatherability coating and film and piezoelectric film etc.
Polyvinylidene difluoride (PVDF) now industrialized polymerization process is mainly letex polymerization, and the emulsion that letex polymerization forms must be through just can further processing after cohesion.Agglomeration process is exactly the process of a breakdown of emulsion, and the method for breakdown of emulsion mainly contains physics breakdown of emulsion and two kinds of methods of chemical demulsification, and physics breakdown of emulsion is as freezing, stirring etc., and chemical demulsification is as saltoutd etc.
The breaking method that at present polyvinylidene difluoride (PVDF) adopts is mainly mechanical breakdown of emulsion, and emulsion, by certain whipped form, is mutually clashed into molecule to be combined into the particle that volume is larger to separate out from emulsion by high speed shear, thereby reached demulsification.Because various ions residual in polymerization process can have influence on the outward appearance of product, so the material after breakdown of emulsion is separated out will wash, after being removed, further processes residual ion-cleaning.
Document " research of polyvinylidene difluoride (PVDF) emulsion after-treatment technology " (synthetic resins and plastics, 2005,22 (2): 35) reported the aftertreatment of polyvinylidene difluoride (PVDF) emulsion, comprised the process of breakdown of emulsion cohesion, separating, washing.Wherein breakdown of emulsion cohesion adopts the mode that adds flocculation agent to carry out, and specifically adopts the salts such as aluminum nitrate, calcium chloride, Repone K as flocculation agent, and especially best with the flocculating result of aluminum nitrate, its massfraction is 1%; Condensation temperature remains on more than 60 ℃, mixing speed be the particle diameter of the resin of 100r/min(cohesion be 28 ~ 32 μ m).Wherein wash conditions is: with high purity water washing, through the washing of 6 ~ 7 times, other conditions too much do not illustrate that (specific conductivity of washing mother liquor is less than or equal to 5 μ s/cm, washs 7 times; And washing is 4 times time, specific conductivity is also greater than 10).The problem that document public technology exists is: the particle diameter after cohesion is less, condenses the pvdf resin that in the pasty state, is unfavorable for next step washing, and 4 specific conductivity of washing are also greater than 10.
Summary of the invention
In order to overcome the problem of prior art existence, the object of this invention is to provide a kind of cohesion washing methods of polyvinylidene difluoride (PVDF) emulsion.
The cohesion washing methods of polyvinylidene difluoride (PVDF) emulsion provided by the invention, comprises the following steps:
(1) be the water of 1 ~ 15 ℃ to adding temperature in polyvinylidene difluoride (PVDF) emulsion, regulate emulsion proportion between 1.04 ~ 1.18;
(2) the polyvinylidene difluoride (PVDF) emulsion that adopts alr mode to obtain upper step is condensed, and mixing speed control is 500 ~ 2000 revs/min, and the breakdown of emulsion time is 1 ~ 15min completely;
(3) polyvinylidene fluoride resin of separating out after cohesion, washes with water.
Wherein, in step (1), preferably 5 ~ 10 ℃ of the temperature of described water, more preferably 8 ℃.
Wherein, in step (1), the proportion of polyvinylidene difluoride (PVDF) emulsion preferably 1.06 ~ 1.12, more preferably 1.08.
Wherein, in step (2), preferably 1200 ~ 1600 revs/min of mixing speed, more preferably 1400 revs/min.If do not adopt such mixing speed, the particle diameter that can make to separate out resin is very little, and following process is very inconvenient.
Wherein, because the freezing breakdown of emulsion of step (1) and the mechanical breakdown of emulsion of step (2) carry out simultaneously, described in step (2), the breakdown of emulsion time is this two steps breakdown of emulsion time sum completely, preferably 5 ~ 10min, more preferably 8min.
In the step (1) of aforesaid method, if emulsion proportion is less than 1.04, pool time is long, and productive rate is low, and the resin particle diameter obtaining is less than normal; Emulsion proportion is higher than 1.18, and under stirring action, when cohesion, some emulsion can be scattered in toner, when washing, along with the eliminating of water, causes the waste of emulsion, reduces productive rate.Water temp is during lower than 1 ℃, and emulsion particle movement rate reduces, thereby has reduced the chance of colliding between particle, just can not make emulsion primary particle reunite, and cohesion generation secondary particle particle diameter is just little; Temperature is during higher than 15 ℃, and to secondary particle, grain diameter influence is little, has extended on the contrary the time of breakdown of emulsion.
Wherein, in step (3), the temperature of described water is 50 ~ 100 ℃, preferably 70 ~ 90 ℃, and more preferably 80 ℃.
Wherein, in step (3), the number of times of washing is 2 ~ 6 times, preferably 3 ~ 4 times, and more preferably 4 times; All wash 3 ~ 10min, preferably 4 ~ 8min, more preferably 6min at every turn.
Wherein, in step (3), the polyvinylidene fluoride resin that while washing, upper step is separated out at every turn and the volume ratio of water are 1:(1.5 ~ 2).And the process of the freezing breakdown of emulsion of step (1), the ratio that the volume ratio of emulsion and water is not determined, adds the volume of water how many, see the proportion height situation of former emulsion; If the proportion of former emulsion is high, the amount of that water adding is just large, otherwise the amount just adding is just few.
Wherein, in step (3), after washing, electrical conductivity of water is less than or equal to 10 μ s/cm.
The method of the invention, described water can be used deionized water, distilled water or high purity water.Preferably deionized water, industrial production cost is lower.
The method of the invention, as the polyvinylidene difluoride (PVDF) emulsion of raw material, can directly bring use, also can leave standstill at normal temperatures for some time to carry out aforesaid method again and operate.The emulsion of coming through letex polymerization, in just polymerization out, emulsion is to have higher temperature, by leave standstill for some time in normal temperature environment, the temperature potential of emulsion must reduce, and for adopting Refrigerating Machinery flocculate and break emulsion, the carrying out of the low more favourable subsequent operations of temperature.
If the independent mechanical breakdown of emulsion time increase, independent freezing breakdown of emulsion not only the breakdown of emulsion cycle long, the energy consumption of refrigerating process is high in addition, certainly will for industrial production, greatly increase the cost of product.Machinery breakdown of emulsion is strong mechanical stirring for PVDF emulsion, because the collision rate of PVDF particle in emulsion is accelerated, make the position, motor point of emulsifying agent in emulsion be not enough to overcome its Efficiency Decreasing of bonding force while collision, cause PVDF molecule to be separated from emulsion, i.e. breakdown of emulsion.Freezing breakdown of emulsion is that most emulsions produce demulsifying phenomenon after freezing, and its reason is that after being to be refrigerated to freezing point, first water separates out ice crystal, so because the density of ice forms tectum gradually lower than water.Be subject to mechanical pressure because the continuation of ice crystal increases the emulsion being closed in below tectum, and the electrolyte concentration in emulsion system strengthens comparatively speaking, thereby cause high-polymer molecular to be separated out, be i.e. breakdown of emulsion.And the present invention adopts freezing and mechanical condensed phase to be combined to have reached compared with prior art, better demulsification.
The method of the invention provides is the cohesion washing methods of the polyvinylidene difluoride (PVDF) emulsion that forms for letex polymerization, mechanical breakdown of emulsion and freezing breakdown of emulsion are combined, there is better demulsification, median size increases that (median size of the inventive method is in 200 about μ m greatly, only have 30 μ m left and right and other usual ways obtain), and the flocculate and break emulsion time greatly shorten (in 15min).And further, washing process adopts hot wash, has increased electrolytical solubleness, thereby has shortened washing time, just can obtain qualified product by less washing times and water consumption.In a word, the present invention has improved the throughput of equipment greatly, reduces the consumption of water, has shortened treatment cycle, is conducive to large-scale industrial and produces.
Embodiment
Following examples are used for illustrating the present invention, but are not used for limiting the scope of the invention.
Other operations of not writing exactly in the present invention are added to the normal condition of this area, and the material using is the conventional material for buying from the market also.
Embodiment 1
(1) be the deionized water of 8 ℃ to adding temperature in 500mL polyvinylidene difluoride (PVDF) emulsion, regulating emulsion proportion is 1.08;
(2) open and stir, mixing speed control is 1400 revs/min, and the breakdown of emulsion time is 8min completely; Before cohesion, the median size of PVDF emulsion is in 20 μ m left and right, and the median size after cohesion is 230 μ m;
(3) polyvinylidene fluoride resin that flocculate and break emulsion is separated out, it is the deionized water wash of 80 ℃ by temperature, when each washing 5min(washs at every turn, the polyvinylidene fluoride resin that upper step is separated out and deionized water volume ratio are 1:2), repetitive scrubbing 7 times, measure the rear deionization electrical conductivity of water of washing, lower than i.e. qualified (washing 4 times just conforms with the regulations) of 10 μ s/cm, after washing, PVDF is white in color Powdered.
Embodiment 2
(1) be the deionized water of 10 ℃ to adding temperature in 500mL polyvinylidene difluoride (PVDF) emulsion, regulating emulsion proportion is 1.06;
(2) open and stir, mixing speed control is 1600 revs/min, and the breakdown of emulsion time is 5min completely; Before cohesion, the median size of PVDF emulsion is at 20 μ m left and right, the median size 180 μ m after cohesion;
(3) polyvinylidene fluoride resin that flocculate and break emulsion is separated out, it is the deionized water wash of 70 ℃ by temperature, when each washing 8min(washs at every turn, the polyvinylidene fluoride resin that upper step is separated out and deionized water volume ratio are 1:1.18), repetitive scrubbing 4 times, measure the rear deionization electrical conductivity of water of washing, qualified lower than 10 μ s/cm, after washing, PVDF is white in color Powdered.
Embodiment 3
(1) be the deionized water of 5 ℃ to adding temperature in 500mL polyvinylidene difluoride (PVDF) emulsion, regulating emulsion proportion is 1.12;
(2) open and stir, mixing speed control is 1200 revs/min, and the breakdown of emulsion time is 10min completely; Before cohesion, the median size of PVDF emulsion is at 20 μ m left and right, the median size 200 μ m after cohesion;
(3) polyvinylidene fluoride resin that flocculate and break emulsion is separated out, it is the deionized water wash of 90 ℃ by temperature, when each washing 4min(washs at every turn, the polyvinylidene fluoride resin that upper step is separated out and deionized water volume ratio are 1:6), repetitive scrubbing 4 times, measure the rear deionization electrical conductivity of water of washing, qualified lower than 10 μ s/cm, after washing, PVDF is white in color Powdered.
Embodiment 4
(1) be the deionized water of 15 ℃ to adding temperature in 500mL polyvinylidene difluoride (PVDF) emulsion, regulating emulsion proportion is 1.18;
(2) open and stir, mixing speed control is 500 revs/min, and the breakdown of emulsion time is 15min completely; Before cohesion, the median size of PVDF emulsion is at 20 μ m left and right, the median size 210 μ m after cohesion;
(3) polyvinylidene fluoride resin that flocculate and break emulsion is separated out, it is the deionized water wash of 50 ℃ by temperature, when each washing 10min(washs at every turn, the polyvinylidene fluoride resin that upper step is separated out and deionized water volume ratio are 1:1.5), repetitive scrubbing 3 times, measure the rear deionization electrical conductivity of water of washing, qualified lower than 10 μ s/cm, after washing, PVDF is white in color Powdered.
Embodiment 5
(1) be the deionized water of 1 ℃ to adding temperature in 500mL polyvinylidene difluoride (PVDF) emulsion, regulating emulsion proportion is 1.04;
(2) open and stir, mixing speed control is 2000 revs/min, and the breakdown of emulsion time is 1min completely; Before cohesion, the median size of PVDF emulsion is at 20 μ m left and right, the median size 170 μ m after cohesion;
(3) polyvinylidene fluoride resin that flocculate and break emulsion is separated out, it is the deionized water wash of 100 ℃ by temperature, when each washing 3min(washs at every turn, the polyvinylidene fluoride resin that upper step is separated out and deionized water volume ratio are 1:2), repetitive scrubbing 4 times, measure the rear deionization electrical conductivity of water of washing, qualified lower than 10 μ s/cm, after washing, PVDF is white in color Powdered.
Comparative example
Other conditions are the experiment condition 1 in following table with embodiment 1(embodiment 1 corresponding group), difference be all use normal-temperature water (25 ℃) to carry out the washing of the cohesion of step (1) (the polyvinylidene fluoride resin volume after breakdown of emulsion is 250mL) and step (3) (each washing is added deionized water and is 500mL, each washing time is 5min), group is the experiment condition 2 in following table.
Comparing result see the following form (sensing range in form is specific conductivity≤30 μ s/cm):
Can find out from the comparative analysis of upper table result, with the breakdown of emulsion time of cold water than shortened for 44% time by normal-temperature water.And, when washing, just qualified with hot deionized water washing 4 times, all do not have for 7 times qualifiedly and washed by normal-temperature water, bath water is than how over half with hot deionized water, and washing afterwards PVDF be micro-yellow.By breakdown of emulsion time and the comparison of bath water amount, present method has shortened the breakdown of emulsion time, has reduced bath water amount, thereby has greatly improved the throughput of equipment, is conducive to suitability for industrialized production.
Although above the present invention is described in detail with a general description of the specific embodiments, on basis of the present invention, can make some modifications or improvements it, this will be apparent to those skilled in the art.Therefore, these modifications or improvements without departing from theon the basis of the spirit of the present invention, all belong to the scope of protection of present invention.
Claims (13)
1. a cohesion washing methods for polyvinylidene difluoride (PVDF) emulsion, comprises the following steps:
(1) be the water of 1～15 ℃ to adding temperature in polyvinylidene difluoride (PVDF) emulsion, regulate emulsion proportion between 1.04～1.18;
(2) the polyvinylidene difluoride (PVDF) emulsion that adopts alr mode to obtain upper step is condensed, and mixing speed control is 500～2000 revs/min, and the breakdown of emulsion time is 1～15min completely;
(3) polyvinylidene fluoride resin of separating out after cohesion, washes with water; The temperature of described water is 50～100 ℃, and the number of times of washing is 2～6 times, all washs 3～10min at every turn; When each washing, the polyvinylidene fluoride resin that upper step is separated out and the volume ratio of water are 1:(1.5～2).
2. method according to claim 1, is characterized in that, in step (1), the temperature of described water is 5～10 ℃.
3. method according to claim 2, is characterized in that, in step (1), the temperature of described water is 8 ℃.
4. method according to claim 1, is characterized in that, in step (1), the proportion of polyvinylidene difluoride (PVDF) emulsion is 1.06～1.12.
5. method according to claim 4, is characterized in that, in step (1), the proportion of polyvinylidene difluoride (PVDF) emulsion is 1.08.
6. according to the method described in claim 1～5 any one, it is characterized in that, in step (2), mixing speed is 1200～1600 revs/min.
7. method according to claim 6, is characterized in that, in step (2), mixing speed is 1400 revs/min.
8. according to the method described in claim 1～5 any one, it is characterized in that, in step (2), the described complete breakdown of emulsion time is 5～10min.
9. method according to claim 8, is characterized in that, in step (2), the described complete breakdown of emulsion time is 8min.
10. according to the method described in claim 1～5 any one, it is characterized in that, in step (3), the temperature of water is 70～90 ℃.
11. according to the method described in claim 1～5 any one, it is characterized in that, in step (3), the number of times of washing is 3～4 times; All wash 4～8min at every turn.
12. according to the method described in claim 1～5 any one, it is characterized in that, in step (3), after washing, electrical conductivity of water is less than or equal to 10 μ s/cm.
13. methods according to claim 1, is characterized in that, described water is deionized water, distilled water or high purity water.
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| CN104530265B (en) * | 2014-12-18 | 2017-07-11 | 中昊晨光化工研究院有限公司 | A kind of fluoropolymer powder and preparation method thereof |
| CN109320634B (en) * | 2017-07-31 | 2019-11-22 | 中昊晨光化工研究院有限公司 | A kind of cohesion washing methods of fluorinated ethylene propylene resin |
| CN110317286A (en) * | 2018-03-30 | 2019-10-11 | 浙江蓝天环保高科技股份有限公司 | A method of improving polyvinylidene fluoride resin degree of purity |
| CN110016098B (en) * | 2019-02-25 | 2021-03-26 | 聊城氟尔新材料科技有限公司 | Poly (perfluoroethylene-propylene) production condensation washing device |
| CN110078846A (en) * | 2019-04-22 | 2019-08-02 | 中昊晨光化工研究院有限公司 | A kind of post-processing approach of polyvinylidene fluoride emulsion |
| CN111440255B (en) * | 2020-03-26 | 2021-03-02 | 东莞东阳光科研发有限公司 | Post-treatment method of fluorine-containing resin emulsion and fluorine-containing resin |
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