FR2508466A1 - PROCESS FOR THE PREPARATION OF IMIDIZED ACRYLIC POLYMERS - Google Patents

Abstract

THE INVENTION RELATES TO ACRYLIC POLYMERS. IT RELATES TO A PROCESS FOR IMIDIZING AN ACRYLIC POLYMER ACCORDING TO WHICH THE ACRYLIC POLYMER IS REACTED WITH AMMONIA OR AN AMINE IN A TUBULAR CHICANE REACTOR, AT A TEMPERATURE OF 200 TO 300C. USE IN THE ACRYLIC POLYMER INDUSTRY.

Description

The present invention relates to a method for

  for imidizing acrylic polymers, and more particularly

  a continuous process implemented in a

internal baffle tube.

  The homopolymer of methyl methacrylate (MMA) and copolymers with, for example, acrylates, styrene or butadiene, can be imidized by reacting the polymer with ammonia or with alkyl or aryl amines so as to to form imides as represented in the following equation:

? CH CH CHRC

OR 3, 3 3 C "3 2 C

CH 2 C CH-CH -> CH 2 C C

c = 2 Rc NH 2 C 8

at I ÈI O NEU

ORO O 'o // C N "" Co

R "

  Imide polymers can also be obtained

  cyclic by heating selected amides or nitriles.

  Recently, a continuous imidization process has been described in US Pat. No. 4,246,374 in which a methacrylate or acrylate polymer is placed in a screw extruder ventilated with an amine and the imide is formed while the materials are moved through the plodder at temperatures

  raised under substantially anhydrous conditions.

  We have now found a new process for imidizing methacrylic and acrylic resins which does not require the use of a screw extruder and in which the temperature and pressure can be adjusted more carefully than in a screw extruder. The novel process is a process for imidizing a methacrylate or acrylate polymer in which, successively: a) a molten methacrylate or acrylate polymer is mixed with ammonia or a primary alkyl or aryl amine; introducing the molten mixture into a tubular baffled reactor which provides a dispersed bulk flow,

  (c) raising the temperature of the mixture to the

  in the tubular reactor so as to bring it to a level between 2000 ° C. and 3000 ° C., d) the molten mixture is led through the tubular reactor in a time sufficient to carry out the imidization, but shorter than that required

  for a significant degradation of the polymer.

  The polymer to be imidized is an acrylic and / or methacrylic polymer It contains adjacent stitches of R

-CH 2-C-

  CO R 'o R is -CH 3 or -H and R' is an alkyl group of 1 to carbon atoms These polymers may also contain stems derived from up to 40% by weight of methacrylic or acrylic acid, styrene , from

  butadiene, ethylene, acrylonitrile, etc.

  The molecular weight of the polymers can vary within wide limits. Those having an inherent viscosity of at least 0.3 measured in a 0.5% solution in a mixture are preferred. methanol and methylene chloride (20/80) at 250 ° C. The polymer to be imidized can be used in any form, but generally the polymer is in the form of

  powder or granules before it melts.

  The ammonia or the primary alkyl or aryl amine used will generally have the formula R "NH 2 in which R" is -H an alkyl group of 1 to 12 carbon atoms, cycloalkyl of 7 to 11 carbon atoms or

  aryl of 6 to 10 carbon atoms, preferably phenyl.

  Examples of amines useful herein include methyl, ethyl, n-propyl, n-butyl, heptyl, hexyl, octyl, nonyl, decyl, dodecyl, hexadecyl, octadecyl, isobutyl, sec-butyl, t-butyl, isopropyl, 2-ethylhexyl,

  phenethyl, allyl, benzyl, para-chlorobenzyl and dimethoxy-

  phenethyl amines; and also alanine, glycine, 3'-aminoacetophenone, 2-aminoanthraquinone and p-amino-benzoic acid. Other amines which can be used are cyclohexylamine, 2-amino-4,6-dimethylpyridine,

  3-aminophthalimide, 2-aminopyrimidine, 2-amino

  thiazole, 5-aminothiazole, 5-amino-1-H-tetrazole, aniline, bromoaniline, dibromoaniline, tribromoaniline, chloroaniline, dichloroaniline,

  trichloroaniline, p-phenetidine and p-toluidine.

  In the process according to the present invention, the melt polymer and the ammonia or amine are mixed just before or just after they are introduced into the tubular reactor. A method of mixing is to introduce the polymer into an extruder in a controlled manner. to melt the polymer, and to make

  advance the molten polymer into the tubular reactor.

  An addition made more t 8 t can lead to some premature reaction, thus making unnecessary the careful adjustment of temperature and pressure obtained

  by conducting the reaction in the tubular reactor.

  Reaction temperatures may be as low as allowable to maintain a short reaction time and as high as tolerable to avoid excessive degradation of the polymer. Use of an internal baffle tubular reactor with high mixing efficiency and associated uniformity

  temperatures of the substances contained allow the use

  short reaction times at relatively high temperatures without fear of hot spots in the reaction medium.

  and an uneven radial distribution of temperatures.

  erations lead to degradation of the polymer and

  otherwise unacceptable or undesirable polymeric material.

  When the residence time of the contained materials can be kept substantially constant and when the temperature gradients perpendicular to the flow axis

  can be kept very low, it has been found that

  to conduct the reaction at high temperatures in a short period of time rather than at low

  temperatures with a longer time.

  Important factors for efficient reaction conduct include accurate overall control of the temperature of the reactants and the maintenance of a short and uniform residence time of the materials in the reactor. melt temperature of reactant bodies, there will be unequal degrees of reaction, i.e. incomplete reaction in low temperature areas and polymer degradation in high temperature areas in a reactor the temperature differences perpendicular to the principal flow direction of the materials (radially) must be kept to a minimum. To minimize these temperature differences, there must be effective radial dispersion of the materials so that a transfer of heat occurs

  from one place in the reactor, radially, to another.

  Axial temperature control is also important to avoid uneven degrees of reaction that could result from varying exposure to high temperatures.

  of appropriate reaction A steady state operation

  It is necessary for an acceptable continuous process operation. A reactor which has the necessary temperature control, heat transfer efficiency and residence time uniformity is a tubular reactor equipped internally with a series of baffles. This alternating reactor is described in the US Pat.

U.S. 3,286,992.

  In order to obtain a uniform auality polymer, it is important that all the materials

  in reaction is exposed to substantially the same m 9 my

  reaction during substantially the same time.

   This is called a "dispersed block flow." Such a dispersed block flow has the effect that

  each molten polymer element is in the reaction

  during substantially the same time and that there is a considerable movement of domains of the molten polymer relative to other areas of the molten polymer in a radial direction rather than in one direction.

axial or longitudinal.

  In the present process, the polymer is heated to the reaction temperature before it is introduced into the reactor, and the ammonia or amine is added just before or just after this introduction. In the reactor, the temperature is maintained between 200 O and 3000 C, preferably between 24000 and 2800 C In the reactor, the reactants are intimately mixed and each element of material undergoes substantially the same reaction temperature for practically the same time.

  same duration The reaction time is usually less than

  than about ten minutes and more than about a quarter of a minute.

  is between about five minutes and one half

  minute, the relatively short maximum time being important to avoid excessive degradation, crosslinking and other undesirable side reactions. Precise temperature control, small radial temperature gradients, and a short and uniform residence time have been found to allow a good reaction without the excessive degradation that would have been expected at the elevated temperature after completion of the reaction. , the resulting imide is

  evacuated and volatiles are removed.

  The resulting imide is then cooled and cut into pellets. The degree of imidization of the acrylic polymer

  can be easily adjusted in the process according to the invention.

  The desired degree of imidization can be easily adjusted by adjusting the reaction parameters, such as the residence time and the temperature, although imidization of the polymer is also possible. as low as only 1% is possible, in general an imidization of at least 10% is carried out, to obtain a significant improvement of the properties

acrylic polymer.

  No catalyst is required in the process according to the invention. It has the great advantage that the removal of a catalyst is avoided. However, small amounts of a catalyst can increase the

  reaction rate if desired.

  A solvent is not necessary in the process according to the present invention and it is preferred to operate in the absence of solvent. However, if desired, a solvent can be used to reduce the viscosity of the solvent.

  the melt or to convey a catalyst.

  The imides prepared by the process of the present invention are useful as thermoplastic molding resins, and can be extruded as fibers, tubes or film etc. Molding resins can be used to prepare molded articles such as toys, feathers, boot cases, etc.

  The process according to the present invention is

  Especially useful in the preparation of imides containing from 1 to 40% by weight of cyclic anhydride meshes. These imides thus contain R a) CH 2 C OR

R CH 2

b) H 1 C -

L o / C o

) R CH 2 R

c) -H 100 2H 2-C

O N O

  R is -CH 3 or -H; R 'is an alkyl group of 1 to 10 carbon atoms; and R "is HR, an alkyl group of 1 to 10 carbon atoms, a cycloalkyl of 7 to 11 carbon atoms, a cyclophenyl or a phenylalkyl of 7 to 9 atoms

  in which the phenyl groups can contain

  include lower alkyl, lower alkoxy or halo substituents; and the stitches of (a) constitute from 20 to 94% by weight of the total of the stitches, the stitches of (b) constitute from 1 to 40% by weight of the total of the stitches and the stitches of (c) constitute from 5 to 80% by weight of the total of the meshes, the total of these percentages being%. In the following examples, a polymer is heated and introduced into a tubular baffled reactor

  and passed through this reactor by means of the force

  The internal baffled reactor having a dispersed block flow used in the examples was provided by Kenics Corporation, Danvers Mass, EU A. A 2.54 cm Killian extruder having a vacuum port and a two-stage screw was equipped at the die outlet with an adapter plate, three Kenics Thermogenize sections and 2.54 cm

  diameter in succession, followed by a die valve.

  The Killian extruder was used to melt the

  polymer and advance it into the Kenics sections.

  A diffusion plate 5.2 mm thick with

  64 holes were placed at the entrance of the Kenics sections.

  This plate, used to promote the mixing action, was about 2.54 cm upstream of an injection probe opening at 6.35 mm into the melt stream (fixed in an adapter plate) and about 38 mm upstream of the first element of the first Kenics section Ammonia or amine was introduced through the injection probe or through the Killian extruder vent port. A sieve assembly was placed after the last Kenics section and before

  valve die to help adjust the pressure

  A heated transfer pipe was used to drive the melt from the valve die to the backside vacuum of a 28 mm Werner and Pfliederer twin-screw extruder that was used to remove volatile matter. The 28 mm extruder feed was used as a vacuum source to remove volatiles, and the prior vacuum port was used to devolatilize the imide product as well. The outgoing imide strand was then quenched and cut. Unless otherwise indicated, percentages

are by weight.

EMPXE 1 I

  This example shows that the imidization reaction occurs in the tubular baffled reactor and

  not in one of the extruders Two flow mixers

  Kochu fine (DY) and two coarse (CY) baffled blocks replaced Kenic elements in t9 te in the first of three Kenics sections and two coarse Koch elements (CY) replaced the Kenics leading elements in the second Eenics section. The Killian extruder was operated at 144 rpm with temperature settings at 250 C for the posterior area,

  225 C for the central zone and 225% C for the former zone.

  The Kenie sections were all set to give a temperature of 2800 C; the die valve and the transfer pipe were set at 2250 C. The 28 mm twin-screw extruder was of a through-pass type with the exception of a group of inverted elements between the two vacuum ports Normal to form a melt seal It was operated between 108 and 135 rpm with the following temperature settings: rear (1) 500 C, (2) 2000 C, (3), (4), (5) and die = 2500 C. We operated on four batches using the

  cyclohexylamine and a polymethyl methacrylate of a screw

  inherent coseness between 0.47 and 0.53 For batches 1 and 2, the amine was discharged into the empty port of the Rillian plodder of 2.54 cm; for the

  lots 3 and 4, it was pushed back into the injection probe

  fixed in the adapter plate For batches 1 and 3, the final product was isolated in the form of pellets cut after devolatilization in the 28 mm extruder. For batches 2 and 4, samples 2 and 4 were evacuated. by a melt thermocouple hole at the downstream end of the transfer pipe just before the melt came into contact with the screw of the twin screw extruder Table 1 shows that 63% of the amine reacted with the polymer during mixing only in the tubular reactor (lots 3 and 4)

  and only 57% of the amine reacted with the poly-

  mother when the amine was introduced into the Killian extruder and the product was passed through the double screw extruder (lot 1) As a higher conversion was obtained in lots 3 and 4 than in lot 1, conclude that the reaction is

  produced in the tubular reactor.

Lot Pump pressure (bars)

Amine introduced

  at (cm 3 / min) Production rate of the finished polymer (g / min)% of N in the final product Conversion% of imide amine 38.6 tl * 41 t 4 n *

2.24 57.5

57% 2.55 39.3 not measured

2.22 57.3

2.22 37.3

  % * These flow rates could not be measured really, but no adjustment was changed during the short duration of

  these states; as a result, flow rates probably remain unchanged.

  n O% O O CD cm J 1% - Qr 12.5 12.5 12.0 12, O I 1

EXAMPLE 2

  The same apparatus was used as in Example 1, except that only two Koch mixers (in the initial portion of the first Kenics section replaced all Kenics elements. The 2.54 cm Killian extruder was operated. at 145 rpm with temperature settings of 175 C (posterior),

  22500 C (middle part) and 2500 C (front part).

  The temperature of the three Kenics sections was set at 280 C. The 28 mm twin-screw extruder was operated at 130 rpm with the following temperatures recorded: I 1400 C (rear), 2445 C, 3245 C, 4500 The cyclohexylamine was discharged into the vacuum port of the Killian extruder at a flow rate of 16.1 cm 3 / min at a pressure of 56 bar. A polymer composed of methacrylate methyl / styrene / butadiene (70/25/5) was introduced into the 2.54 cm extruder and a devolatilized final product was obtained at a rate of 41.9 g / min which contained 2.58% of corresponding nitrogen. to 43.2% of N-cyclohexyl imide structure having a temperature Tg of 144 C

  as determined by differential calorimetric analysis

  power compensation.

EXAMPLE 3

  We used the same device as in the example

  1, apart from the presence of 2 elements DY E Koch and 4 elements

  CY in the first section Kenics, 8 elements

  CY in the second and 2 elements CY in the third.

  The 2.54 cm Killian extruder was run

  at 144 rpm with temperatures of 25000 C (pos-

  2340 C (middle part) and 227 C (front part) The three Kenics sections were each set at 28000 C. The 28 mm double screw extruder was operated at 104 rpm with temperatures of 1 153 C (part posterior), 2 24790 C, 3275 C, 27700 C, 273 C and die 28400 C Aniline was pumped into the vacuum port of the Killian extruder at 9.5 cm 3 / min. The polymer used was a copolymer of methyl methacrylate / methacrylic acid (87/13, inherent viscosity in CH 2 C 2 = 0.53) was obtained at a rate of 35 g / min

  an imide product which contained 1.50% nitrogen corresponding to

  spiked with 24.6% of N-cyclohexyl imide of methacrylic acid.

EXAMPLE 4:

  The same apparatus and the same temperatures as in Example 3 were used. Ammonia was fed for introduction to the adapter plate at a rate of 5 g / min. 140 bar level The polymer was introduced at a rate of 40 g / min The polymer used was a terpolymer having the components methyl methacrylate / styrene / butadiene in a weight ratio of about 75/20/5, with an inherent viscosity in OH 2 C 12 of 0.51 The imidized resin

  produced contained 4.65% N and had a temperature

  This example illustrates the reaction of cyclohexylamine and a methacrylate polymer to form at once.

  cyclic imide and anhydride meshes.

  The Killian extruder was operated at a rate of 2.54 cm at 144 rpm with temperature settings of 250 C in the posterior zone, 225 C in the center and in the anterior zone.

  baffles used included the three Kenics sections.

  In section 1, Kenics baffles were replaced

  Koch DY and CY baffles In Section 2, the first Kenics baffle was replaced by a Koch CY baffle. The sections were set at 2800 C. The valve die and the transfer pipe were set at 225 C. 28 mm was of a through-pass type with the exception of a group of inverted elements between normal vacuum ports to form a melt seal and operated at 108-135 rpm with temperature settings of 50 C

  (posterior), 2000 C (center) and 250 C (die).

  A copolymer of methyl methacrylate and ethyl acrylate (95.5 / 4.5%) having an inherent viscosity of 0.575 was introduced into the 2.54 cm extruder at about 37 g / min and cyclohexylamine was discharged at point A (the vacuum port of the Killian extruder) or at point B (the injection probe)

  at 63 bar and at about 10.4 g / min (22% w / w).

  Imidized polymer was sampled as it came out of the baffled tubular reactor (Item I) or after devolatilization in the twin screw extruder (Item II). The results are as follows:

  of the amine anhydrid imide * sample

  ** I A II polymer weight 37.5 wt% 7.5 wt%

2 to I 39.3 5.2

3 B II 37.3 5.6

4 B I 37.3 5.6

  * Imide content based on nitrogen analysis and

infrared spectrum.

  ** Anhydride content by titration and infrared spectrum.

Claims (4)

  A process for imidizing a methacrylate or acrylate polymer in which, successively: a) a molten polymer of methacrylate or acrylate is mixed with ammonia or an aliphatic or aromatic primary amine; b) the molten mixture is introduced; in a tubular baffled reactor which provides a dispersed bulk flow, c) the temperature of the mixture is raised within the tubular reactor to bring it to a level between 200 ° and 500 ° C and the molten mixture through the tubular reactor in a time sufficient to perform the imidization, but shorter than necessary   for a significant degradation of the polymer.   2 Process according to claim 1, characterized in that in step c) the temperature is between 240 and 2800 C. 3 Process according to claim 1 or 2, characterized in that the meshes of the polymer are composed of at least 80% by weight of methacrylate of methyl.   4 Process according to claim 1 or 2, characterized in that the amine is cyclohexylamine or ammonia. Process according to Claim 4, characterized in that the meshes of the polymer are composed of   minus 80% by weight of methyl methacrylate.