DE2324908A1 - METHOD OF RECHLORINATING POLYVINYL CHLORIDE - Google Patents

Description

The present invention relates to an improved one

Process for the post-chlorination of polyvinyl chloride (.PVC) on the "dry way" and has the purpose of a post-chlorinated To obtain polyvinyl chloride of homogeneous quality.

In this technical field, it is well known that a ¹ polyvinyl chloride, is obtained by the chlorination of polyvinyl chloride when it is accomplished with chlorine gas and using a photochemically active light source, the / esistance by a greater heat resistance, a larger 7 against chemical agents and characterized by a higher softening temperature.

So far there are two for the aforementioned post-dislocation Ve ge have been pursued, namely:

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1) the wet route, in which the chlorine gas with PVC in solution or in water or in organic liquids containing brought into contact, optionally with the addition of chlorinating _r auxiliary agents such as acids, thickenings, catalysts, usxir .;

2) on the dry route, in which the chlorine gas with

granular PVC is brought into contact, primarily using the vortex measuring method. Despite the obvious advantages of the dry route over the wet route, the latter has found greater industrial diffusion in view of the fact that the continuous chlorination of PVC by the dry route tends to produce an inhomogeneously chlorinated product because the Particles of the synthetic resin remain in the reactor at different times and therefore chlorinate each other in different ways. The constituents which remain for relatively long periods of time over-chlorinate, result in granular chlorine of PVC, which does not gelatinize easily, and the product chlorinated and extruded in this way has an imperfectly smooth surface due to pitting and is inferior mechanical properties compared to PVC obtained in non-continuous processes.

Moreover, in chlorination processes of PVC by dry, continuous and fluidized beds, it is necessary to achieve repeatable chlorination and ^{avoid the formation of crusts and blocks of sintered and inferior P Tr} C, at a linear rate of the To work with reaction gases, which are higher than the

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incrustations. leading critical speed is (siebe Z..3. the Italian patent 755 274) *

This speed can be ten times faster; The value reached as' that of the least liquefaction · * 3® according to the reaction rate and the grain size of the PVC in the initial stage.

The present invention is now a Method found for post-chlorination of PVC on dry 'iege, which allows the shortcomings and. the aforementioned problems " satisfying to meet and at the same time for industrial Application is suitable. During the post-chlorination of PVC by dry means and in a fluidized bed <, in / zelchem Chlorine gas is brought into contact with granular PVC under the action of a photoehemiseh active light source, sees one improvement in having the reaction in the presence a commonly used pigment in the next Connection of the chlorinated synthetic resin takes place, which has low chemical affinity for chlorine and which in the Reaction is present in the form of a solid powder mass or in small grains »

In practical tests it has been found that the aforementioned pigment acts as a regulator in the chlorination and, in particular, makes the degree of chlorination of the granular PVC surprisingly uniform throughout the synthetic resin composition in reaction. In other Porten, therefore, the presence of pigment, such below each other reaction condition ,, causes a uniform unc * repeatable velocity of chlorination in the present in the reaction resin mass. >

It has also been found that the presence of the aforementioned pigment, preferably between carbon black and titanium dioxide selected, reduces the toughness of the fluidized bed and has an antistatic and sinterless effect exercises. This makes it possible with a low ratio ^ · nis chlorine / PVC to work at two to three times the speed of operation compared to the lowest liquefaction of the fluidized bed and preferably below that which, according to the known technique, is the critical speed represents the formation of crusts and blocks.

According to the present invention, in fact, moved for an assumed grain size of resin (80-120 microns) the slowest condensation speed between each other 0.7 and iji cm / sec., Depending on the degree of chlorination, while the critical speed for crust formation in the sense and according to the methods of the prior art, 4-8 cm / sec. amounts to.

The amount of pigment added to the reaction mass moves

in
themselves / very small amounts, on the order of 0.001 parts. 100 parts of the synthetic resin, and the maximum permitted amount for the compound of the post-chlorinated synthetic resin.

It is important to note and this represents another The advantage of the present invention is that the amount of pigment added in the course of the reaction in the subsequent Compound of the synthetic resin is advantageously discontinued (peeled off), equivalent to an unchanged Costs of the raw materials that are needed for the preparation of the final mixture.

The invention can be better understood with reference to the following examples.

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EXAMPLE 1

The chlorinated reactor consists of a cylindrical shaped fluidized bed with 25 l volume and an annular chamber for temperature control, a thermometric Probe, a pneumatic system for loading and unloading the resin and a 60 Watt fluorescent tube for white light.

The reactor is continuous with synthetic resin PVC Pozzi S 65 charged and in an amount that allows it to remain for a period of 4 hours.

The discharge takes place in such a way that the volume of the liquefied mass remains constant.

The temperature is automatically regulated to 50 ⁰ C.

The properties of liquefaction as well as those of the chlorinated resin and the extruded pipe are shown in Table I. ,

3 EXAMPLE 2

Proceed as in Example 1, but with Synthetic resin PVC Pozzi S 65 charged reactor, 0.02 part of carbon black per 100 parts of synthetic resin was added.

The properties of the liquefaction of the achieved chlorinated resin and the extruded tube are shown in Table I.

EXAMPLE 3

The procedure is as in Example 1, but the reactor is charged with Pozzi S 65 synthetic resin with the addition of 0.1 parts Titanium dioxide. The properties of the liquefaction, the obtained chlorinated resin and the extruded pipe are shown in Table I.

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EXAMPLE 4

The procedure is as in Example 1, but with a reduced one Speed of chlorine that is less than the critical speed for crust formation.

The properties of liquefaction achieved chlorinated resin and the extruded tube are shown in Table I.

EXAMPLE 5 '

The procedure is as in Example 2, but with a reduced Rate of chlorine as in example 4

The properties of liquefaction achieved chlorinated resin and the extruded tube are shown in Table I.

EXAMPLE 6

The procedure is as in Example 3> but with a reduced rate Rate of chlorine as in example 4

The properties of liquefaction, achieved chlorinated Resin and the extruded tube are shown in Table I.

EXAMPLE 7

The procedure is as in Example J, but the reactor is charged with synthetic resin PVC Pozzi S 65 with the addition of 0.01 part of carbon black and 0.05 part of titanium dioxide.

The properties of liquefaction, achieved chlorinated Resin and the extruded tube are shown in Table I.

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TABEL EXAMPLE

PROPERTIES liquefaction 1 2 3 4th 5 6th 7th -Chlorine speed (cm / sec.) -Toughness of the fluidized bed (cent.poise) (l) 9 9, 9 O . 3 3 -Density of the bed (gr / cm ^) 120 65 70 180 95 98 "ω Chlorinated synthetic resin 0.28 0.32 0.32 0.32 0.36 . 0.36 0.36 K) < ^Cl 2 θ -Temperature resistance like generation of IIC1 65.0 64.2 65.3 63.9 63.9 65.8 € 64.7 » at I8O ° C (mgr / gr PVC at 3O ⁰ C) - Vicat softening temperature (° C) (2) 0.61 0.60 0.40 1.64 ■ 0.61 ο, 44 c ·,? 0 - Impact resistance with incision after 115 111 120 108 110 120 " 114 Charpy at 23 ⁰ C (kg χ cm / ^cm2 ) (.3) ■ 4 Vi f ^S I Extruded Tube (4) 6.4 11.3 15.4 4.3 14.5 12.3 10.5 -Vicat - breaking load under zag (kg / cm ² ) 106 106 115 93 106 114 - -108 -Extension at break (%) 457 500 49 5 439 488 490 43 C ψ -Ball drop 47.3 65 65 23.5 70 6 Q 65 -Appearance 2,500 ' 5 5 ' 0.900 5 5 ' ⁵ dotted glittering glittering strong glittering glittering glittering smooth smooth jjpunkt smooth smooth J

Remarks:

(1) Measurements in this regard carried out with a Brookfield type RVF viscometer, spindle No. 2, speed 20 rpm

(2) Mixture on foil, treated for 10 'at 180 ° C in a mixer with cylinders, prepared as follows: post-chlorinated PVCj tribasic lead sulfate 3.5j dibasic lead phosphite 1.5; Stearic acid 1.0

(3) a grain-derived plate, which is taken from a film which is treated for 10 'at 190 ⁰ C in a mixer with cylinders and consists of a mixture as prepared follows: post-chlorinated PVC 100; tribasic lead sulfate 3.5; dibasic lead phosphite 1.5J stearic acid 1.0; counteracting agent 10; Fillers. and dyes 5.

(4) achieved in that the grain according to point (3) is extruded over a die (diameter 45).

Using the table in which Examples 1 and 4 repeat previously known technique, it clearly emerges the advantages achieved with the present invention, namely:

- considerable reduction in the viscosity of the fluidized bed j

- remarkable increase in thermal stability;

- remarkable increase in impact resistance;

- Significantly improved properties of the extruded pipe such as appearance, elongation in the event of breakage and in the Sample "ball drop".

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Claims (7)

PATENT CLAIMS Process for post-chlorination by dry route of polyvinyl chloride, in which polyvinyl chloride in the form of Granules are made to react with chlorine gas, in the presence of a photochromically active light source, thereby characterized in that the reaction takes place in the presence of a pigment which is normally used in the under such subsequent connection of the chlorinated plastic selected and has a low affinity for chlorine and is present as a solid in small granules or in powder form is, 2) Method according to claim 1, characterized in that said pigment is carbon black. 3) Method according to claim 1, characterized in that said pigment is titanium dioxide. 4) Method according to claim 1, characterized in that said pigment is a mixture of carbon black and titanium dioxide is. 5) Method according to claim 1, characterized in that said pigment is added to the post-diorated synthetic resin is, in an amount that is not greater than the maximum permissible amount in the subsequent connection of the after- chlorinated synthetic resin. 6) Method according to claim 4 *, characterized in that said pigment added in the minimum order of magnitude of 0.001 parts per 100 parts of the post-chlorinated synthetic resin will. -9- 30985070855 7) Method according to claim 1, characterized in that the post-chlorination is accomplished in the fluidized bed at an operating speed which is lower than the critical one Speed for the formation of crusts and blocks, S) Method according to claim 6, characterized in that said working speed 2-3 times the lowest
Speed of liquefaction is. 309850/0855 -10-