EP0328826A2 — Process and apparatus for controlling the manufac…

Claim 1

Independent Claim 180 words

Process for the manufacture of a polymer defined by at least one property P equal to a desired value D, the property P characterising the molecular structure of the said polymer, or being related to the molecular structure, the process consisting of polymerising one or more monomers in the presence of a catalyst in a reactor provided with heat transfer means, with pressure control means feed means and optionally with purge means, which process is characterized in that the property P of the polymer is determined a number of times during the polymerization reaction by the application of a correlation relationship with n results R i of n absorbance measurements performed by means of an infrared spectrophotometer on the polymer at n wavelengths chosen in the near infrared region from 0.8 to 2.6 microns and in that, depending on the determined values and on the desired value D, the process parameters are controlled by means of a process computer so that the difference between each of the determined values and the desired value is smaller than a set value S.

Claim 2

Dependent Claim 180 words

Process for the manufacture of a polymer defined by at least one property P equal to a desired value D, the property P characterising the molecular structure of the said polymer, or being related to the molecular structure, the process consisting of polymerising one or more monomers in the presence of a catalyst in a reactor provided with heat transfer means, with pressure control means feed means and optionally with purge means, which process is characterized in that the property P of the polymer is determined a number of times during the polymerization reaction by the application of a correlation relationship with n results R i of n absorbance measurements performed by means of an infrared spectrophotometer on the polymer at n wavelengths chosen in the near infrared region from 0.8 to 2.6 microns and in that, depending on the determined values and on the desired value D, the process parameters are controlled by means of a process computer so that the difference between each of the determined values and the desired value is smaller than a set value S.

Claim 3

Dependent Claim 24 words

Process according to Claim 1, characterized in that the monomers are olefins chosen from ethylene or alpha-olefins containing from 3 to 10 carbon atoms.

Claim 4

Dependent Claim 44 words

Process according to Claim 1, characterized in that the monomers correspond to the general formula CH₂=CR₁R₂, in which R₁ and R₂ are identical or different radicals denoting a hydrogen atom, an alkyl radical containing from 1 to 8 carbon atoms or an aryl radical.

Claim 5

Dependent Claim 29 words

Process according to Claim 1, characterized in that the monomers are chosen from vinyl chloride, vinyl acetate, vinyl acrylate, methyl methacrylate, methyl vinyl ether, methyl vinyl ether and acrylonitrile.

Claim 6

Dependent Claim 24 words

Process according to Claim 1, characterized in that the catalyst employed is chosen from radical catalysts, cationic catalysts, anionic catalysts or anionic coordination catalysts.

Claim 7

Dependent Claim 44 words

Process according to Claim 1, characterized in that the polymerization reaction is carried out in gaseous phase in a reactor with a fluidized and/or mechanically agitated bed at a pressure ranging from 0.1 to 5 MPa and a temperature ranging from -20 to +115°C.

Claim 8

Dependent Claim 39 words

Process according to Claim 1, characterized in that the polymerization reaction is carried out in suspension or in solution in a liquid hydrocarbon medium, at a pressure below 10 MPa and at a temperature ranging from -20 to 300°C.

Claim 9

Dependent Claim 89 words

8 Process according to Claim 1, characterized in that the catalyst for the polymerization reaction is a solid catalyst based on chromium oxide activated by a thermal treatment, or a catalyst system of the Zieglar-Natta type consisting, on the one hand, of a solid catalyst based on a transition metal belonging to Groups IV, V or VI of the periodic classification of the elements and, on the other hand, of a cocatalyst consisting of an organometallic compound of a metal belonging to Groups I to III of this classification.

Claim 10

Dependent Claim 27 words

Process according to Claim 1, characterized in that a property P of the polymer is determined in a period of less than or equal to 5 minutes.

Claim 11

Dependent Claim 26 words

Process according to Claim 1, characterized in that the property P of the polymer is determined at least once every 15 minutes during the polymsrization reaction.

Claim 12

Dependent Claim 82 words

Process according to Claim 1, characterized in that the polymer is defined by at least one property chosen from the density, the viscosity, the isotacticity index, the melt index, the content of at least one of the comonomers forming the polymer, the degree of crystallinity, the melt flow ratio, the molecular weight, the molecular weight distribution, the unsaturation content of ethylenic type, the methyl group content, the rigidity, the yield stress, the stress cracking resistance, the impact strength,the gloss and the transparency.

Claim 13

Dependent Claim 32 words

Process according to Claim 1, characterized in that the correlation relationship is a linear function or an algebraic function of n results Ri of the absorbance measurements carried out on the polymer.

Claim 14

Dependent Claim 31 words

Process according to Claim 1, characterized in that the number n of the absorbance measurements carried out on the polymer is between 2 and 20 and preferably between 2 and 10.

Claim 15

Dependent Claim 37 words

Process according to Claim 1, characterized in that the absorbance measurements are performed by means of the infrared spectrophotometer by reflection on a polymer which is in a solid form or is easily isolated in this form.

Claim 16

Dependent Claim 102 words

Process according to Claim 1, characterized in that the absorbance measurements are carried out on the polymer, by means of the infrared spectrophotometer, at wavelengths, expressed in microns, or at substantially closely related wavelengths, chosen from the following series: a) 1.212 - 1.732 - 2.316 - 2.360 - 2.448 b) 2.332 - 2.452 - 2.456 c) 1.144 - 1.272 - 1.688 - 2.364 - 2.444 d) 2.320 - 2.344 - 2.440 e) 1.372 - 1.512 - 1.648 - 2.364 - 2.444 f) 1.112 1.696 - 2.184 g) 2.388 - 2.408 h) 1.504 - 1.652 i) 2.428 - 2.464 j) 2.212 - 2.216

Claim 17

Dependent Claim 51 words

Process according to Claim 1, characterized in that the correlation relationship is determined beforehand by multivariant regression with the results of absorbances measurements carried out on 3 to 50 standard polymers of previously known properties, under conditions identical to the absorbance measurements carried out on the polymer manufactured or being manufactured.

Claim 18

Dependent Claim 30 words

Process according to Claim 1, characterized in that the constituents feeding the polymerization reactor are the monomer(s), the catalyst, the cocatalyst, an inert gas, a solvent, and a chain-limiting agent.

Claim 19

Dependent Claim 19 words

Process according to Claim 1, characterized in that the set value S represents 10% of the desired value D.

Claim 20

Dependent Claim 185 words

A process for the manufacture of a polymer having at least one property P with a desired value D by polymerising one or more olefinic or vinyl monomers in the presence of a catalyst, the reaction being controlled by: (a) periodically taking a sample of the polymer, (b) analysing the sample to determine the value of at least one property P, (c) generating an input signal representative of the determined value of the property P, (d) comparing the input signal with a preset value, (e) generating a control signal as a function of the deviation between the input signal and the preset value, and (f) controlling process parameters responsive to the control signal characterised in that: (g) the sample is a liquid polymer or solid polymer which has been treated only to separate it from its polymerisation medium, (h) the sample is analysed by an infra red spectrometer at n wavelengths in the near infra red region from 0.8 to 2.6 microns, and (i) the input signal is generated by the application of a correlation relationship using n results R i of n absorbance measurements.

Claim 21

Dependent Claim 185 words

A process for the manufacture of a polymer having at least one property P with a desired value D by polymerising one or more olefinic or vinyl monomers in the presence of a catalyst, the reaction being controlled by: (a) periodically taking a sample of the polymer, (b) analysing the sample to determine the value of at least one property P, (c) generating an input signal representative of the determined value of the property P, (d) comparing the input signal with a preset value, (e) generating a control signal as a function of the deviation between the input signal and the preset value, and (f) controlling process parameters responsive to the control signal characterised in that: (g) the sample is a liquid polymer or solid polymer which has been treated only to separate it from its polymerisation medium, (h) the sample is analysed by an infra red spectrometer at n wavelengths in the near infra red region from 0.8 to 2.6 microns, and (i) the input signal is generated by the application of a correlation relationship using n results R i of n absorbance measurements.

Claim 22

Dependent Claim 30 words

A process as claimed in claim 19 in which the process is a process for producing polyolefins by gas-phase fluidised bed polymerisation and the sample is polymer powder or particles.

Claim 23

Dependent Claim 148 words

Apparatus for making use of the process according to any one of Claims 1 to 20, characterized in that it comprises a polymerization reactor provided with heat transfer means, with pressure control means, with at least one monomer feed pipework and one catalyst feed pipework, means for taking samples of polymer, means for transferring samples into the cell of an infrared spectrophotometer, a process computer coupled to the polymerization reactor provided with a program which makes it possible to control the polymerisation temperature, the polymerisation pressure, the feed rates and optionally the purge of the polymerization reactor, an infrared spectrophotometer capable of operating in at least one region of the near infrared ranging from 0.8 to 2.6 microns, intended to perform the absorbance measurements on the polymer, and a calculator intended for the calculation of the property P of the polymer by the application of a correlation relationship.

Claim 24

Dependent Claim 33 words

Apparatus according to Claim 21, characterized in that the polymerization reactor is additionally provided with a pipework for discharge of polymer at the bottom, itself equipped with a device for taking polymer samples.

Claim 25

Dependent Claim 16 words

Apparatus according to Claim 21, characterized in that the calculator is included in the process computer.

Claim 26

Dependent Claim 17 words

Apparatus according to Claim 21, characterized in that the infrared spectrophotometer is a Fourier transform infrared spectrophotometer.

Process and apparatus for controlling the manufacture of polymers

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