FR2492387A1 - CONTINUOUS DRY CHLORINATION PROCESS OF VINYL POLYHLORIDE - Google Patents

Abstract

CONTINUOUS PROCESS FOR THE CHLORINATION OF VINYL POLYCHLORIDE CONSISTING OF CONTINUOUSLY ARRIVING IN AT LEAST ONE REACTOR UNDER IRRADIATION, on the one hand, VINYL POLYCHLORIDE PARTICLES AND, ON THE OTHER HAND, A CHLORINATION GAS AND SUPPLYING POLY CHLORINATED VINYL SHAPED, AND IN WHICH THE PARTICLES ARE IN A THIN LAYER AND MOVE IN THE REACTOR IN BIG SUCCESSIVE, WITH A PISTON-TYPE FLOW. APPARATUS FOR CARRYING OUT THE PROCESS. APPLICATION OF CHLORINATED VINYL POLYCHLORIDES TO THE MANUFACTURE OF TUBES, FIBERS, PLATES, INJECTED FITTINGS, ANTI-CORROSION COATINGS.

Description

CONTINUOUS PROCESS FOR CHLORINATION BY SECTIONS

VINYL POLYCHLORIDE

  The subject of the invention is a continuous process of chlorination with

  dry route of polyvinyl chloride.

  It is known that the chlorination of polyvinyl chloride makes it possible to obtain chlorinated polymers having glass transition temperatures and fire resistance that are much greater than

those of the starting product.

  To perform this chlorination, techniques by lane

  have been proposed. They consist in carrying out the chlorination

  fluidized bed polymer, vortex layer in rotary tubes, or thin fixed bed on endless belt. However, these techniques require, in most

  case, to put the sources of radiation inside the reaction

  high energy consumption and lead to heterogeneous chlorinated products and the formation of agglomerates and

  deposits on the walls of the reactor.

  The method according to the invention avoids these disadvantages; the irradiation sources being outside, the equipment is more

  simple, moreover, the energy consumption is low, the pro-

  Chlorinated products are homogeneous, and there is no formation of agglomerates.

mates and depot.

  The continuous process for the chlorination of polyvinyl chloride, according to the invention, consists in continuously arriving, in at least one reactor under irradiation, on the one hand

  polyvinyl chloride and, on the other hand, a possible chlorination gas

  it is diluted with an inert gas and continuously withdraws the chlorinated polyvinyl chloride formed and is characterized in that the polyvinyl chloride particles are in a thin layer and

  move in the reactor by successive leaps, with a

piston type.

  The polyvinyl chloride used is in the form of particles preferably having a porous structure, the

  granulometry is between 50 and 150 tons, the visco-

  sity is between 70 and 150 and the porosity is between and 40m1 / 100g. Such particles can be obtained by known polymerization processes, such as solution, suspension or emulsion polymerization, and more particularly

by mass polymerization.

  The polyvinyl chloride particles to be chlorinated may be more or less chlorinated prior to their use; the chlorinated polyvinyl chloride being obtained by any known method and more particularly by the method of the invention. Although this is not essential, it is possible to perform the chlorination in the presence of a swelling agent of the

  polyvinyl chloride, which gives a better homogeneity

  chlorinated particles, especially when the particles are not porous. It is represented, for example, by chlorinated hydrocarbons, such as: chloroform, tetrachloride of

  carbon, 2-chlorobutane and is added to the polymer,

  chlorination, ie during chlorination, by introducing

  continuous discharge into the reactor of the separate blowing agent

  but simultaneously, or mixed with the chlorination gas.

  After chlorination, the swelling agent is removed by any known technique, such as, for example, evaporation under vacuum and / or heating and / or entrainment with an inert gas; elimination which is advantageously carried out at the same time as that of the reaction gases. By chlorination gas is meant chlorine gas and all compounds releasing under irradiation chlorine radicals, such as thionyl chloride. The chlorination gas is used

  alone or diluted in an inert gas, that is to say without chemical action.

  only on polyvinyl chloride and chlorination gas. Examples of inert gases that may be mentioned are argon, nitrogen and hydrochloric acid. The temperature of the chlorination gas alone or diluted

  is generally between 0 and 80 ° C.

  To initiate the reaction, the irradiation of the polyvinyl chloride particles is obtained by a radiation whose

  wavelength is preferably between 290 and 450 nm.

  To obtain chlorination, the rate of introduction of the poly-

  vinyl chloride circulating in the reactor is a function of the nature of the polymer, the width of the reactor, the thickness of the polyvinyl chloride particle layer and the velocity

  advancing said particles into the reactor.

  The thickness of the particle layer, which must be sufficient

  thin so that all the particles are irradiated and to avoid their agglomeration, is generally between

0.1 and 5 mm.

  The speed of advancement of the polyvinyl chloride particles in the reactor is advantageously between 0.3 and m / h. The particles move individually in successive leaps that promote contact between the chlorination gas and the particles and allow the irradiation of the entire surface of the particles.

  each particle, and with a piston-like flow, that is,

  to say that they move regularly and at a constant speed, which allows a homogeneous chlorination. This displacement by successive leaps, with a piston type flow is obtained by simple conventional means, such as, for example, electromechanical means. The amount of chlorination gas to be used is

  depending on the chlorine content of the chlorinated polymer to be obtained, corresponding to

  maximizes the stoichiometric amount of chlorine radicals necessary to obtain a 73.2% by weight chlorinated polyvinyl chloride. Depending on the chlorine content of the chlorinated polymer to be obtained, the rate of introduction of the chlorination gas into the reactor is advantageously between 5 and 50 liters per hour, whether

pure or diluted by a gas. inert.

  The passage of the chlorination gas alone or diluted in the reaction

  in the same direction as the passage of

  polyvinyl chloride or against the current; the first possibility

  it is a preferred form because it avoids turbulence

  These and the risks of deposits on the walls of the reactor.

  As long as these conditions for the introduction of particles and

  chlorine gas are produced, the chlorine content of the polychlorinated

  The higher the average residence time of the polyvinyl chloride in the reactor, the higher the chlorinated vinyl chloride content. This average residence time is generally less than 8

  hours and preferably between 1 and 5 hours.

  Oxygen having a detrimental action on the reaction and the chlorinated polymer to obtain, it is preferable to implement

  products containing little oxygen and to rid the appliance of

  the oxygen it contains; which is easily obtained

by passing an inert gas.

  The reaction temperature which is between the ambient temperature and the softening temperature of the product to be chlorinated, depending on the quality of the product to be obtained, is obtained either by the heat generated by the reaction which is exothermic and / or by use. of hot chlorination gas and / or by the irradiation source when it provides a heating radiation whose wavelength can reach, for example 3000 nm. In

  In some cases, it may be necessary to maintain the temperature

  constant temperature inside the reactor, to reduce the heating by radiation reduction and / or by acting on the temperature

incoming gases.

  During the chlorination, the pressure in the reactor is the atmospheric pressure or a slightly higher pressure,

not exceeding 1.5 bar.

  The continuously extracted chlorinated polyvinyl chloride is stripped of the unreacted chlorination gas and the hydrochloric acid formed therein by any known means, for example evacuation, passage through the particles a non-reactive gas, such as air, at a temperature below the softening temperature of the chlorinated polyvinyl chloride. The

  where appropriate, this degassing is carried out simultaneously with the removal

nation of the swelling agent.

  The gases leaving the reactor, consisting of excess chlorination gas, hydrochloric acid formed and possibly gas

  inert, can be used in other manufacturing or recycling.

  key after separation of polyvinyl chloride particles

Chlorinated coaches.

  The process of the invention makes it possible, by varying the operating conditions, such as the rates of introduction of the polymer particles and of the chlorination gas, residence time of the particles in the reactor, temperature, radiation, to be prepared within the given limits. homogeneously chlorinated polyvinyl chloride, with chlorine levels between 56.8 and

73.2% by weight.

  The equipment used consists of at least one reaction

  equipped with an irradiation source, a continuous supply of polyvinyl chloride particles, a device ensuring the arrival of the chlorination gas alone or diluted with an inert gas, a continuous evacuation system chlorinated polyvinyl chloride formed and a chlorine gas evacuation system

  unreacted, hydrochloric acid formed and possibly

  inert gas and is characterized in that the reactor

  the largest possible area exposed to radiation, in that the irradiation source is outside the reactor and

  in that the lower surface of the reactor is provided with a device

  of displacement of the polymer particles by successive

  sifs, with piston-type flow.

  Any device that meets these characteristics can be

  used, but preferably there may be mentioned a parallel reactor

  the large-area lipipedic, whose ratio width / length

  is between 0.025 and 0.15 and the thickness of which is preferably

  the lowest possible concentration, in order to avoid having too great a thickness of chlorination gas between

chlorinate and the source of irradiation.

  The lower surface of the reactor is provided with any system allowing the displacement of the particles in the direction of the height and the length with a flow of piston type,

  such as a vibrating conveyor, a perforated plate

  thrown with directed gas jets. This system must be adjustable, in order to give different speeds of advancement of the particles and consequently different thicknesses, depending on the chlorine content of the final product to be obtained. Thus, the speed of advancement will be even more

  low that the rate of chlorine to be obtained will be greater.

  The irradiation source, placed above the largest surface of the reactor gives a radiation necessary for the reaction whose wavelength is between 290 and 450 nm. An irradiation source giving a radiation whose distribution

  wavelengths are more spread out, for example reaching

  dre 3000 nm, allows both reaction and heating.

  iron the reaction medium.Any light source giving this ray-

  can be used. Among these sources, are to mention, between

  others, discharge lamps, metal halogen lamps,

  the sun, which is a particularly advantageous source. In order to increase the action of the irradiation source, it may be necessary to use reflectors placed around

lamps and / or around the reactor.

  The continuous particle feeding system must be

  a flow regulator and a distributor giving a layer

  of particles throughout the width of the inferior surface.

reactor.

  The continuous evacuation system of chlorinated polyvinyl chloride is connected to a desorption device, where the particles

  are freed from the gases and possibly the gelling agent.

they contain.

  The gas evacuation system is advantageously in common

  nication with a recycling circuit of said gases.

  In order to increase the production of chlorinated polyvinyl chloride, it is obvious that a

  larger capacity reactor and / or more reactors

  sive. In the latter case, there is circulation of the polymer from one reactor to another. The chlorinating gases circulate on the one hand in the same direction as the polymer or in countercurrent in each

  reactors and, on the other hand, against the flow of the poly-

  mother from one reactor to another; in such a way that the chlorine content of the polymer increases from one reactor to another, while the chlorination gases are depleted in chlorine. The gases leaving the first reactor are recycled to the last. Such devices provided with several continuous chlorinated polyvinylchloride evacuation systems, placed at different locations of a

  large reactor or at the end of each of the reactors

  sifs, allows, in the same operation, to obtain polychlorides

  chlorinated vinyl at different chlorine levels.

  The equipment may optionally be used to effect the chlorination of polymers and copolymers of olefins and diolefins, polyvinyl compounds such as polymers

  acrylic and polystyrene, fluoropolymers.

  The chlorinated polymers according to the process of the invention possess

  significantly better properties than the starting polyvinyl chloride, especially their transition temperature

  vitreous and their fire resistance.

  Chlorinated polyvinylchlorides obtained according to the invention

  are applicable to the manufacture of objects requiring

  properties superior to those of polyvinyl chloride, such as in the manufacture of tubes, fibers, plates, fittings

  injected, anticorrosive coatings.

  We give, below, by way of indication and without limitation,

  embodiments of the invention.

Example 1

  A parallelepipedic reactor 60 cm long is used.

  7 cm wide and 1 cm high, comprising - a vibration conveyor formed of a metal container

  U, whose bottom is equipped with a system of vibrations.

  - an upper wall made of glass transparent to UV radiation - at one end, - an inlet for polyvinylchloride to be chlorinated provided with a flow regulator and a hopper which deposits the powder over the entire width of the reactor, - a chlorine gas inlet - at the other end - an outlet for chlorinated polyvinyl chloride, a gas outlet;

  - at 7 cm above the upper wall two lighting lamps

  halogen (quartz-iodine tungsten filament) 1000 watt and wavelength 300 to 3000 nm, above

  of which are placed reflectors.

  The reactor is freed of the air contained therein by

  nitrogen for 10 minutes, then pure chlorine at room temperature.

  ambient temperature is introduced at a flow rate of 5 l / h, which is maintained for the duration of the reaction, the pressure in

  the reactor being maintained at 1.2 bar.

  When the reactor is filled with chlorine, the introduction of polyvinyl chloride is started with a flow rate of 50 g / h. Polyvinyl chloride has an average diameter of 10 μm, a

  viscosity index of 78, and a porosity of 16 ml / 100 g of poly-

  mother. At the same time, the lamps are switched on and the vibration system is switched on, in order to progressively and uniformly advance the polychloride particles.

  vinyl of 36 cm / h, with a thickness of 1.5 mm.

  After 10 minutes, the temperature of the reaction medium is 800 ° C.

  and stabilizes at this temperature.

  At the outlet of the reactor, the chlorinated polyvinyl chloride formed is collected and degassed under vacuum to remove excess chlorine and hydrochloric acid formed. Thus, after 2 h 30 min, 100 g of polyvinyl chloride, homogeneously chlorinated to 63.6%, are obtained. There are no agglomerated particles in the chlorinated polymer and no deposit on the transparent wall

of the reactor.

Example 2

  We operate as in Example 1, but the lamps are replaced

  by the sun of the same intensity, and the reactor is calorific-

  Fuge. After 10 minutes, the temperature of the medium is 80 ° C and stabilizes. After 2 hours 30 minutes, 100 g of homogeneously chlorinated polyvinyl chloride are obtained, the chlorine level is

  62.8%. There is neither agglomeration nor deposit.

Claims (9)

  1) Continuous process of chlorination-polyvinyl chloride which is to continuously arrive in at least one reactor under irradiation, firstly polyvinyl chloride particles and secondly a chlorination gas optionally diluted by a inert gas and continuously withdrawing the chlorinated polyvinyl chloride formed and is characterized in that the polyvinyl chloride particles are thin layer and move in the reactor by successive leaps, with a piston type flow. 2) Process according to claim 1, characterized in that the particles have a particle size of 50 to 150Opm, an index of   viscosity 70 to 150 and a porosity of 10 to 40 ml / 100g.   3) Method according to claim 1, characterized in that the   chlorine gas is chlorine or a compound releasing under irra- of chlorine radicals.   4) Process according to claim 1, characterized in that the temperature of the chlorination gas alone or diluted with an inert gas, is between 0 and 80C.   Process according to Claim 1, characterized in that the irradiation of the polyvinyl chloride particles is obtained by radiation of wavelength between 290 and 450 nm.   6) Process according to claim 1, characterized in that the thickness of the layer of polyvinyl chloride particles is between 0.1 and 5 mm.   7) Process according to claim 1, characterized in that the speed of advancement of polyvinyl chloride particles in   the reactor is between 0.3 and 70 m / h.   8) Process according to claim 1, characterized in that the rate of introduction of the chlorination gas into the reactor is between 5 and 50 1 / h.   9) Process according to claim 1, characterized in that the residence time of the polyvinyl chloride in the reactor is less than 8 hours.   Process according to Claim 1, characterized in that the chlorination is carried out at atmospheric pressure or under a pressure not exceeding 1.5 bar.   11) Apparatus for carrying out the process according to claim 1, composed of at least one reactor provided with an irradiation source, a continuous feed of the particles of   polyvinyl chloride, a chlorine gas supply device   feed alone or diluted with an inert gas, a continuous evacuation system of the chlorinated polyvinyl chloride formed and a system for evacuating the unreacted chlorination gas, the hydrochloric acid formed and optionally the inert gas and characterized in that the reactor has the largest possible surface exposed to radiation, in that the irradiation source is outside the reactor and in that the lower surface of the reactor is provided with a device of displacement of polyvinyl chloride particles by successive leaps, with flow of piston type.   12) Apparatus according to claim 11, characterized in that the irradiation source is represented by lamps or by the sun.   2 () 13) Apparatus according to claim 11, characterized in that   that the device for moving particles is a transpor-   vibration tester or a perforated plate with directed gas jets.