CA1106541A - Imidized acrylic polymers - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Polymers containing imide units and a process of imidizing acrylic to any desired degree of imidization without the use of added water or solvent.

Description

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_~CKGROUND 01~ Tll:~ INVENTION
`ield ol.' lhe Inven-tion 'I'h-is invention relates to novel imide polymers and to me-thods for preparati.on thereof'.

II. Descrip-tion of the Prior Art The basic reaction of f'ormation of imides by reacting ammonia, butylamine, dodecyl amine or oc-tyl amine with polyme-thyl methacrylate is shown in Graves U. S. Paten-t ~.
No. 2~1L~6,209, German Patent 1~0777872 and German Paten-t 1,2ll2~369. Schroder e-t al U. S. Patent 3~28L~ 25 and British l'atent 926~629 show a route toward lmidized acrylics by re- .' actirLg polymethyl methacrylate~ wi-th ammonium hyd:roxi.de~ ammon-ium phosphate, alkyl amines or a combination of partial re-ac-tion wi-th ammonium hydroxide followed by reacti.on wl-kh a3kyl : 15 amine. British Patent 1,045,229 shows chemical modlricatlon oL' methacrylic acid/methacrylonitrile (MMA/MAN) copolymers or terpolymers by heating at 180-3000 C . to give the cyclic ; `:
amide product~ optional.ly with a dispersing solven-t. German Patents 1, 2L~7,517; 2,041, 736; and 2~0L~7~ 096 show methacryl- ' amide/methyl methacrylate (MAN/MMA) copolymers~ inert solvent~
and heat -to achieve imide f'ormation accompanied by evolu-tion of ammonia. Most prior patents and literature on proc~esses to imidized acrylics via reac-tion of` ammonia and prlmary amines~
with polymethyl methacrylates~ U. S. Patent 3,284,L~25 for example, are directed to an autoclave batch process requiring lengthy heating time, usually 7 hours or more7 in the presence of' ine~t dissolving or suspending solvent. U. S. Patent 3, 557 7070 describes a process f'or preparing e-thylene/meth acrylic acid/methacrylamide -terpolymers f'rom an ethylene.-isopropyl methacryla-te copolymer by heating the copolymer .

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~o the decomposition temperature (3250C.) of the isopropyl cster to form methacrylic anhydride units which are then reacted with gaseous ammonia to give methacrylamide and methacrylic acid residues in the polymer chain. The reac-tion ~ -is run neat witnout solvent and the patent examples mention decomposition "zones". Although this patent does not mention that these reactions are taking place in an extruderg the Derwent abstract of this patent mentioned that these reactions may be run in an extruder. The use of extruders as polymer reactors has been shown as a route to copolyesters (Prepara-tion and Properties of Copolyesters Polymerized in a Vented Extruder, J. Applied Polymer Science 12,2403[1968J, nylon products (Direct Extrusion of NYlon product from Lactams, Modern Plastics, August 1969 --- Werner Pfleiderer) and graft polymerization of polyolefins (Steinkamp et al U. S. 3,862~265).
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West German Patent 1,077,872 discloses an extruder process of ~;
imidizing acrylic polymers using a water solution of ammonia, but the product is a foamed strand with deficient thermal stability and which requires further processing before it can

2~ be used to fabricate usèful items; furthermore, the process described is not commercially feasible in that the foamed polymer exits the extruder under high pressure with free ammonia vapor.
It is an object of the present invention to provide a process for imidization of acrylic polymers at low residence times It is a further object to provide a process for imid-ization of acrylic polymers without substantial molecular weight degradation and wherein the polymers produced have a high, uniform molecular weight and are non-crosslinked and thermoplastio~ and ha~e improved thermal stabili Jy. A further

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object is to provide a process wherein less than substan-tially complete imidization of acrylic polymers is possible, especially to produce uniformly imidized polymers.
Another object is to provide nove:L imidi2ed acrylic polymers. A still further object is to provide an improved process for producing imide polymers with improved proper-ties, free of the disadvantages of prior processes.

SUM~L~RY OF THE INVENTION
_ These objects and others as will become apparent from the following disclosure are achieved by the present invention which comprises in one aspect a process for pro-ducing a polymer con-taining imide units comprising reacting under substantially anhydrous conditions in an extruder an acrylic polymer with ammonia or a primary amine at a tempera-15 ture of about 200 to 450C. while applying subatmospheric pressure to at least one vent port of said extruder.
The polymer product containing imide units produced by this product is another aspect of this invention. The thermoplastic polymer, part of the invention, contains imide units of the structural formula ; ~3 ~ o : ~
~ ~ CH~

Rl 2 wherein Rl, R2, and R3 independently represent hydrogen or unsubstituted or substituted Cl to C20 alkyl, aryl, or aralkyl, alkaryl, or mixtures thereof, said polymer being further -4a-: ' ,' characteri2ed as non-crosslinked and soluble in dimethyl formamide, and having a degree o~ thermal stability as `:
measured by TGA such ''' : ~
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that the temperature at which said polymer has a 1% compo -.ition in air is above 285oc.
Dynamic thermogravimetric analysis, (TGA), as used in this specification, is a standard test conducted with a progra~ned temperature increase rate of 200 C./min. in either an air or a nitrogen atomosphere on a du Pont thermogravimetric analyzer in combination with a differential thermal analyzer as described in du Pont Instrument Products Division Prelim-lnary Product Bulletin 950-1 (A-36177).
DETAILED DESCRIPT~ION ~ :
The acrylic polymer is any polymer containing units derived from esters of acrylic or methacrylic acid. The polymer can be single or multiple stage~ but in the latter case the outer or final stage must contain units derived from acrylic or methacrylic àcid since it is belie~ed that the imldization reaction takes place mainly in this stage. While any such acrylic or methacryIic acid esters can comprise the acrylic polymer, and can comprise any amount of the polymer, generally at least 25 percent by weight, preferably at least about 50 ~;
percent by weight, more preferably above about 80 percent, and most preferably about 95 to 100 percent by weight of the acrylic polymer is of said esters. Preferred are the species wherein the ester moiety contains l to 20 carbon atoms, most preferably methyl methacrylate (MMA~ due to its lower cost and avail~
abllity. Polymers of monomer systems comprisedof at least 80 ~-percent by weight l~MA are very sultable. The acryIic polymer can contain units derived from other ethylenically unsaturated monomers such as styrene, acrylonitrlle, and even such monomers as butadiene. ~he acrylic polymer can be a single stage polymer 3o or can be a multiple stage polymer such as a core-shell polymer ~"
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or a gra:r-t polymer, with varying degrees of` graf'-ting be-twecn ~;-L.ages.
The acrylic polymer can be of' a wide range of molecular weights. Since commercially available acrylic polymers range in intrinsic viscosities, [ ~ ~DM~ of about .
0.01 and below -to abou-t 7.0 and above, these are of course preferred. Acrylic polymers having an ~ ~ ~DM~ of about 0.28 to 2 0 are most preferred.
Frequently the starting materials will comprise a single s-tage polymer dry or melt bIended with a multiple stage impac-t modif'ier polymer~ in which case the single stage polymer and primarily -the outer stage of the mul-tiple stage polymer are imidized. Such blends are more compatible than blends of the imldi.zed single stage polymer ~ith the same multiple stage polymer, especially when the latter is not imidized. Preferred are blends of single stage acrylic polymers with about lO to 60~ by weight multiple stage polymer.
The acrylic polymer can be in any form, but is gen-erally in molding powder or granule form, and can be colorless or colored~ but in some cases the imidization process affects -the dyes or pigments~ in which case the coloring agent is incorporated af'ter processing.
The ammonia or primary amine is a cornpound of the formula R3NH2 wherein R3 is hydrogen or substituted or~un-; 25 substituted alkyl or aryl havin~ up to 20 carbon atoms.
~ he substantially anhydrous ammonia or primary amine,or mixtures thereof, is introduced to the reaction zone in gaseous or liquid form under pressure, but in the case of ; primary amines can optionally be introduced in solid form~ Due to ready availability, ammonia and methylamine are most preferred of the compounds of the ~ormula R3NH2~ but others work very well , in the process also, and also gi~e very desirable products.
Other suitable amines include, for example~ ethyl~ n-propyl~
n-butyl,heptyl, hexyl, octyl, nonyl, decyl, dodecyl, hexadecyl~
octadecyl~ îsobutyl, sec-butyl, t-butyl, isopropyl, 2~ethyl hexyl, phenethyl, allyl, benzyl, parachloro benzyl, and dimetnoxy phenethyl amines; alanine; glycine; 3'-amino-acetophenone; 2-aminoanthraquinone; and p-aminobenzoic acid.
Also cyclohexyl amine, 2-amino-~,6-dimethyl pyridine, 3-amino phthalimide, 2-aminopyrimidine, 2-aminopyridine, 2-aminothiazole~
5-amino-1-H-tetrazole, aniline, bromoaniline, dibromoaniline, tribromoaniline, chloroaniline, dichloroaniline, trichloro-aniline, p-phenetidine,~nd pwtoluidine are suitable. It is important that little or no water be introduced with the ammonia or primary amine, never more than about 2 percent by weight~
preferabl~ less than 1 percent~ water based on ammonia or primary amine. For purposes of this invention, the term sub-stantially anhydrous is defined by the aforementioned maximum water contents.
In accordance with the process aspect of the in~
vention, the acrylic polymer is continuously fed to an extruder, and the ammonia or primary amine is introduced continuously at the same time, usually through an injection port. Unwanted by-products and excess ammonia or primary amine are removed by progressively reducing the pressure at downstream extruder vents, with at least one downstream vent at vacuum (subatmos-pheric pressure). Sometimes only one vent under vacuum is all that is necessary to adequately remove all by-products and un-reacted ammonia or primary amine.
The temperature in the extruder can be varied, de-pending on the nature of the starting materials, pressure, residence time, etc., ~ut is especially dependent on the melt viscosity of the polymer being extruded. Usually, about 300 ' ~ ~.

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to 3750 C. is suitable, bu-t about 200 to l1500 C. would ~enerally be the outer limits of -the inte:rnal temperature o.L' the ex-trucler. Dif'f'eIent secti.ons of'-the ex-truder-reactor can be maintained at di:E'feren-t tempera-tllres.
i As high a pressure as possible is pref'erred, but again the pressure most suitable depend~ on other factors such as equipment limitations and the like. As low as atmos-pheric is operable, and as high as 1000 atmospheres is poss-i.ble. In most embodiments~ below 500 a-tmospheres pressure is suitable. When the primary amine is i.ntroduced in solid form it can be introduced as a dry blend with the acrylic polymer rather than through a separate addition port.
l'he reaction time (or average residence time in the reaction zone) is about 0.1 to 1000 seconds, prefera'bly about 3 to 300 seconds.
The degree of imidization of' the acrylic polymer is readily controllable in my process,.and different.degrees are chosen for different properties desi~ed in the final product.
l'he desired degree is consistently achievable by adjustment of the reaction parameters such as residence time. Although as low as 1% imidization can be achieved~ at least 10% is usually needed for noticeable property improvement of the acrylic polymers. Up to about 100% imidization can readily ~ ~e achieved ~r the process~ meaning essentially a~l of the ~:
ester moleties of the acrylic polymer are converted to glutar-imide moieties.
No catalys-t is necessary in the process. This re~
sults in the great advantage of eliminating the necessity of catalyst removal. Sma.ll amounts of catalyst conceivably 0 increase production rates, however.

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No solvent is necessar~, and it is preferred not to use it.
The product exits the extruder in melt form, at which point other additives such as fibersr colors, flame retard-ants and the like can be incorporated. Optionally, additivessuch as, for example, impact modifiers, pigmen-ts, fibers, stabilizers, lubricants, etc. can be added with the acrylic polymer prior to introduction in the reactor. The product can then be allowed to solidify in any desired form, e.g., sheet, tube, film, rodr or strand, and the solidified product can be chopped into powder or granule form as de-sired.
Impact modifiers of the ABS(acrylonitrile/butadiene/
styrene), MBS~methyl methacrylate/butadie~le/styrene) and all acrylic type have been found to be useful for improving the impact strength of the imide polymers while retaining high service temperature. The ratio of impact modifier to imide polymer can be varied over a wide range, depending upon how much impact modification is needed for the particulate application. Ratios of impact modifier to imide polymer of from about 1:99 to about 70:30 are useful, with the prefer-red range being about 5:95 to 60:40. Impact modifiers can be single or multipIe stage polymers. In the case of multiple stage polymers, thé impact modifier can have a hard or soft ~irst or "core" stage followed by stages varying in hard-ness or softness. Exemplary impact modifiers are those disclosed in U.S. Patent No. 3,985,704 of D.H. Jones et al, X

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~9a-issued Oct. 12, 1976~ and entitled "MBS Graft Polymers and Process for their Production, and in U.S. Patent 3,808,180 of April 30, 1974.

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:E~:rom about 0.1 to ahout; 25 percent by weight :~lame :retlIdant can be employed, preferably compounds o:f bromine~
chlorine, antimony, phosphorus aluminum trihydrate, certain organic compounds containing -two or more hydroxyl groups, or mixtures thereof~ More speci.fic examples of flame retardants are -triphenyl phosphate, phosphonium bromide, phosphonium oxide, tris (di-bromo propyl) phosphate, cycloaliphatic chlorides, chlorinated polyethylene7 antimony oxide, ammonium polyphosphate, decabromo-diphenyl ether and chlorinated poly-phosphonate. The high service temperature of the poly (glutarimide)in its base resin permits larger amoun-ts of fire retardants to be added than can be added -to other base resins~ :
while yet maintaining acceptable service -ternperature.
~ ~ide variety of fillers can be employed~ at filler levels of from abou-t 5 to oO percent. Surprisingly large a~lounts of filler such as hydrated alumina can be blended wlth the glutaramide polymer kase resin, up to about 60 to 70 : percent, while maintaining -thermoformability. On the other - hand~ most thermoplas-tic systems cannot accept more than abou-t Lto percent iner-t filler with retention of thermoform-ability. The novel:imide polymers can be blended with glass reinforcement at glass levels of about l -to 60 percent to enhance strength~ stif:~ness, creep resistance and deforma-tion resistance at high temperatures and to reduce the thermal ex~ansion co-efficient. The compatibility of the glass re-inforcement with the novel imide polymers is unusally high and frequently permits -the use of glass reinforcement which ha.s standard coupling agents rather than specially prepared re-inforcements.

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If desired, the novel imide polymers can be foamed.
A variety of methods o~ foaming can be used, ~or example chemical blowing agents can be mixed with -the imide polymer and fed to an injection molding machine which plas-ticizes the polymer and decomposes the blowing agen-t under pressure in the cylinder of the injection molding machine with sub-sequent rapid feeding to the cavity of the mold. Articles of variable density, for example, about 0.~ -to 1.2 g/cc-~ can be obtained. Such foamed parts have advantages of rigidity~
design freedom, acous-tic dampening, and corrosion resistance.
In other embodiments, glass fibers can be added along with a chemical blowing agent so as to produce a foamed9 strong, heat resistant part with an asthetically appealing surface and excellent chemical and stain resistance. Also~ fillers such as~ ~or example~ alumina trihydrate can be included with chemical blo~ing agent and~ for example, extruded into flat sheet having a variety of desirable properties such as lower density, good flexural modulus and flame resistance.
~he extruder is preferably multiple screw typej for example a twin screw tangential counter-rotating extruder or a twin screw intermeshing co-rotating extruder.

The product o[` the process is novel~ and has proper-tie'. not po~lble wlth previ.olls lm:ide~ polyrne~ more speci-~`lcal.ly hig'h-tarlx-ile ancl:rlexural strength~ solvent and hydrolysis resls-tance, thermal stablli-ty, hlgh service tempe:rature, good optical properties, weatherability, barrier properties, and others.
I'he polymers of the inven-tion are non-crosslinked, and this ls evlclenced 'by solublllty i.n dimethyl f'orrnamide (DMF) The uniformity of molecular weight and imide content of' my polymers is a ~particularly desirable property O:r the polymers of the invention, and was not achievable in prior processes More specifically, most of the polymer molecules have -the same imide content, and so the compositions have a narrow, controlled composition distribu-tion.
The molecular weight of these compositions is the same as or very close to that of the starting acrylic polymer, which is also a great advantage as contrasted with prior pro-cesses in which molecular weight degradation occurred Chemically, the compositions comprise a thermoplastic polymer containing imide units of the structural formula ~3 o N ~ ::

__ C _-CH2 -R / \ CH / ~ ~

wherein Rl, R2 and R3 independently represent h~drogen or Cl to C20 unsubstituted or substituted alkyl~ aryl, alkaryl7 or:
aralkyl~ Rl and R2 being derived from the acrylic or methacrylic ' acid esters, and the R3 from the ammonia or primary`amine or mixtures thereof'.

In the cases of 100% lmidized polymers~ the glu-tar-imi(le structure is essentially the only repelting unit, but in the case of lower degrees o~ imidiza-tion~ in additlon -to the glu-tarimide uni-ts~ acr~lic uni-ts of the formula ~ O OR) ~, _ ~ ClI2--Rl wherein Rl~ is lower alkyl or other radicals derived from the ester moiety of the acrylic unit will be presen-t.
When acrylic uni-ts are present, the ratio of imide units to acrylic uni-ts~is usually from about 1:9 to about 9 preferably about 3:~ to L~:3.
~ The ammonia-derived imides are mos-t preferred~ and - so R3 is preferably hydrogen. The acrylic polymer is prefer-ably a homopolymer of methyl methacrylate.
The polymers of` this invention have utility as mold-lng powders~ pellets or granules for use in making molded ~
articles such as tail light lenses, toys, watch crystal`s, to name but a ~ew examples. Also, the polymer can be in the form~
~ lof sheet, rod, tube, and the like.
The compositions of the invention can also be used as oil additives due to good viscosity characteristics, not adding to viscosity a-t low temperatures but thickening oil at higher temperatures.
The imide polymers of this invention do not have any significant odor when prepared under the preferred conditions, ~and can be processed by injec-tion molding, extruding, milling~
~or any other polymer processing procedure without odor of degredation. Even at temperatures of over L~oOo C., no polymeric 0 decompositions so as to give off ammonia or amine takes place.
The thermal stability of the polymers of the invention is one of the distinguishing advantages of the materials as -]~3-compared to analogous prior polymers. With thermogravi_ metric analysis, TGA, as the test method, the polymers of the invention have a degree of thermal stability wherein the temperature at which the polymers have a 1% weight loss is above 285 C. in air and above 300 C. ln nitrogen.
To illustrate the invention, the following non~
limiting examples are presented~ All parts and percentages are by weight unless otherwise indicated. ;~
~he follo~ng abbreviations are used:
P _ - pol~mer of _ MMA - methyl methacrylate EMA - ethyl methacrylate EA - ethyl acrylate 3A - bu.tyl acrylate MA - ~ methyl acrylate AA - acrylic acid MAN - methacrylonitrile ,~.
E - eth~lene V~ - vinyl acetate D~F - dimethyl formamide ~ ;~
MDC - methylene dichloride , :, :::
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-rn a -twin screw counter-rotating ex-trllder se t up wlth a feed port for introducing acrylic polymer in ;olld L`OI~m such as granule, pellet, or powder, an acldition port ror introducing ammonia or primary amine a-t elevated pressure, an extruder barrel hea-ted or cooled with oil in f`ive separate zones, each about 84 cm., a die which serves as -the exi-t por-t f`or the polymer product, and a vent por-t operated under vacuum and located in the last zone, acrylic polymer as specified in Table I is introduced via the feed port.
~mine or ammonia reagent, as speclfied in Table I, is introduced in the extruder barrel just after a non-flighted screw sectlon (compounder) which forms a vapor seal which keeps the reagent from going back toward the polymer feed port. ~he reagent contacts and mixes with the polymer as it moves for-ward through the reaction zone, under pressure as specified in Table I. The unreacted reagent as well as the volatile products and by-products of the reactor are removed under vacullm at the vent. The imidized polymer product leaves the extruder through the die in melt f`orm, non-foamed, and essent-ially free of volatile m~terials.
The e~truder used for examples7 to 21 and 27 -to L~5 includes two addi-tional vents, the first being a vent upon which a high pressure is malntained by means of a restrictive valve on the vent, the second being at atmospheric pressure, said vents being loca-ted after the amine introduction port bu-t before the vacuum vent which is at the negative pressure specificed in Table I.
~he extruder used for examples 22 -to 26 is the same 3o as for examples 7 to 21 and 27 to 45 excep-t that it includes -thlrd ancl ~ourth ad~itional vents, located beEore the amine introduction ports, the third being at; atmospheric pressur~
and -the fo~lrth heing at vacuum.
In rlable I, the degree of` imidizat;ion is indicated by ~ ni-trogen (~N), and the rollowing base polymers are used:
~- pM~lA of [ ~ ]DMF of 1.15.
B p(MMA/EA), in a weight ratio of 96/4 in the polymer~ and of [ ~ ]DMF
C. p(~A/EA), 96/4, and of [~ ]DMF = 55 D. pMMA of [~ ]DM~ = 1.35.
E- pMMA [ ~ ]DMF =
F. p(MMA/EA)7 (95/15)~ [ ~ ]DMF 5 ~ ~
G. A syrup of 50~ A and 50% MMA monomer. ~i H. A syrup of 60~ B wi-th 4-0~ of a monomer mixtures f MMA and EA in a ratio of 85/15.
I- pMMA of ~ ~ ]DMF 7 J. p(EM~/BA/MA), 75/25/25 and [ ~ ]DMF = 0.51.
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K- p(MMA/BA), 5/5~ [~ ]DMF
L. p(MMA/AA), 95/5? [~ ]DMF 5 ~:~
; 20 M. p(MMA/MAN, 90/10- [ ~ ]DMF = -7-N. p(MMA/MAN), 98/2 and [ ~ ]DMF = 1-35-o p(MMA/vA)~ 80/20, [ ~ ]DMF = 0-51-p p(MMA/E), 75/25~ [ ~ ]MDC 5 Q. p(MMA/E), 75/25, [ ~ ]MDC 57 R. (pMMA), [~ ]DMF
S. p(MMA/EA)~ 5/5, of [ ~ ]DMF = o-64-~ ~ pMA [~ ] =
j U. p(MMA/E)~ 80/20~ [ ~ ]MDC

V pMMA~ [~ ]DMF = o.64.
O W. p(M~/BA), 95/5~ [~ ]DMF 7 X. 50/50 Blend of I and V.

I~l ce:r tain example ~-,, t,he produc-t pr oduced in a (.lil`:L`erent examplo is introducecl as :~ee~d; this is in~lica-ted b-~Y entry in -t~le '.rable of -tha-t example number under "f eed" .

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I',XAMP:L,F. 1 ~ ~
In an e~x-truder reactor as used in ~xamples 1 to ~15 cxcept ~ith a conf'iguration:polymer feed/high pressure vent/
amine I'eed/a-tmospheric ven-t/vacuum vent/exit die, base polymer ~ is imidized under the same conditions as Example 7 resulting in a nitrogen content of 1.5~ and 'bonds in its IR spectra indicating -the formation of imide groups.
EXAMPL~ 1~7 2724 Kg/hr of a copolymer of 70/30 M~A/EA with a ~ ~ ] ~MF = 2.7 are fed to the feed throat of a twin scre~ counter-ro-tating tangential èxtruder with a screw diame-ter of 51.4 cm. The polymer is conveyed down the barrel~ fluxed, ancl then passed through a restrictive section which ac-ts as a pressure seal. In a section of ex--truder barrel, 15 barrel diameters long, which is isolated with regard to gas transfer from the rest of the extruder, ;
ammonia is added at the rate of 272.4 kg/hr. The ammonia is~
:
aclded to the down stream port of the reaction zone and the ~; ~unreacted ammonia'and reaction products exit the reaction zone on the up stream end of' the reaction zone. The ~apor stream is thus counter~current to the polymer stream. The pressure in the reaction zone is kept at 33.42 atmospheres.
The polymer passes from the reaction zone to a vent :
zone, at atmospheric pressure; at this zone most of the re- ~
.
maining methanol and ammonia are removed. The polymer is then ' ~conveyed into a vent zone operated under reduced pressure to aid in the removal of the last traces of ammonia and methanol.
~The polymer then leaves the extruder through a die containing many holes. The many strands thus formed are cut to glve 2084 kg/hr.of the final product. The product has a nitrogen -22_ ;5~

conten-t of 9.0~ and a~ica-t so~-tening point of 2000 C. It is insoluble in boiling wa-ter and not attacked by mild acids or bases. rhe molecular weight of the produc-t is wlthin 10~ of that of the s-tar-ting polymerD
~_X~MPLE_~8 To an ex-truder, as described in Example L~7~ a co-polymer of 96~ methyl methacrylate with l~ e-thyl acrylate with [ ~ ]DMF of 0.8L~ is introduced at lL~30 kg/hr. This polymer is compacted~ mel-ted, and formed into a continuous stream of molten plastic which is propelled along in the extruder barrel. Through the use of non-flighted and reverse-flighted screw sections the extruder is divided in-to zones through which the polymer can flow but vapors can not pass; pressure di~feren-tials of over 68 a-tm. can be established between zones without vapor transpor-t between them. Io the "reactionl' zone of this extruder is added 738 kg/hr.~of anhydrous monomethyl amine;this material is a gas under the condition of the ex-trusion operation. The monomethylamine gas and the polymer melt are caused to come lnto intima-te contact by havlng several intensive mixing screw sections in the reaction zone. Some of the amine dissolves in the polymer melt. The dissolved amine the reac~s with the ester units in the polymer to displace methanol and to form six membered cycllc imide rings attached to the polymer backbone. The excess amine and the methanol reac-tion product in the vapor phase are removed from the ex-truder at a vent located at the end of the reaction zone.~ A
pressure regulation valve at this vent estabilishes a pressure of 4l~ atm. within -the reaction zone. The polymer melt7 which con-tains dissolvedmonome-thyl amine and methanol, is propelled ;, ' into a ~ren-t zone operated at; a-tmospheric preC;sure~ In -this ' ' 7.0ne most ol' the dissolve(l amine and methanol is removed. The polymer nex-t passes into a vent; zone under a pressure o~' 0.06 atm. In the æone -the remainder of the dlssolved amine and ~lcohol are removed. The polymer melt, now f'ree of volatile materials is rorced through a die to form many strands of polymer which extrude from the machlne. These strands are continuously cooled and cut to give 1195 kg/hr. of the product ~ -polymer in molding powder form. The extruder lS heated to keep -the barrel temperature in all zones at 2800 C., except the ini-tial feed zone which is kept at 150 C. The materials coIlec-ted ~rom the three vents are processed in such a way -to recover most of the monomethylamine in a pure form for recycle to the reaction zone, and a solution of' methanol with some monomethyl amine in it. There are several commercial uses for such a solution, such as in the production of monoethyl amlne by the reaction of' ammonia with methanol.
The polymer produced by this process has a~[~ ]DMF =
.76. I'he reduc-tion in molecular weight upon lmldization is ;~
.
due to the loss of weight due to the chemical transf'ormation of the side chains and not to any significant reduction in the length of -the polymer backbone.
This polymer has a ~ica-t softening poin-t of 182 C.
measured in accordance with ASTM Dl 525-70. It is cle~ar and colorless~and can be processed by all the normal technlques used to prepare useful articles ~rom thermoplastic materials.
The polymer has a Charpy unnotched Impact Streng-th of 7.5 f't.-lbs. measured in accordance with ASTM D-256-56.

.

E.XI\ MP.L.E, 11-9 50 g/lllin. o[` p~ is a(l(lod to a Wc-~rnor l`l'leidoreL t~Ln screw intermeshlng extruder type ZDS-L 28. To an injection port near the feed end o~ this extruder 10 g/min. of methyl-amine is added at 170 a-tm. 'I`he unreacted methylamine and volatile products are removed from the extruder at a vacuum vent near the die end of'-the extruder. The resul-ting polymer has a nitrogen conten-t of 8.~% and gives an ~R spectra which shows that the polymer is essentially all imide.

50 g/min. of' pMMA is added to a 1" Killion single screw extruder. To this extruder ammonia is added at 8 g/min. at an inlet port near the feed end of' the extruder. llhe unreacted ammonia and reaction products are removed at a vacuum vent near -the fron-t end of the machine. The resulting product is a clear colorless polymer soluble ln DMF.
EXAMPLE 51 - (Comparative) A. Attempted repeat of Example 7 of West German Patent IDAS L,077~872. `I
As in the reference, an aqueous ammonia (~I3/~20 ratio of 80/20 by wt.) solution was introduced through a vent plug oL` a single screw at a rate of 5 cc/min. -to a ~0 g/min.
feed of pMMA (~ SP/C of 0.5). llhe extruder was a 1" Killion with an l/d of 2L~/1 and a 1/2" x 2" vent port located 60~ of the way from the feed to the die, the vent being equipped with a plug with an inlet port which was, in turn, connec-ted by a steel line to a LAPP LS-5 pump which, in turn, was connected -to a feed cylinder. The extruder was run at 100 RPM with a barrel tempera-ture of 2650 C.
With a f'irst screw having a channel width reduction f'rom 0.255 -to 0.110 (going from vent area to die), the highest ammonia pressure obtainable was 15 atm. since the pressure seemed to be venting through the die. Attempting to achieve - the pressure specified in the reference. (a) the polymer feed rate was increased to 70 g/min., but the ammonia pressure remained at 15 atm.; (b) the ammonia rate wasincreased to 11 cc/min. with resultant ammonia pressure increase to 20 atm., but the pressure still seemed to be venting through the dle.
Attempting to achieve the pressure~conditions reported in the reference, a second screw~ having a channel width reduction of 0.200 to 0.050, a screen pack, and an ammonla `
rate of 5cc/min. were used, but again only 15 atm. ammonia pressure could be obtained since the pressure seemed to vent through the polymer feed port. However, the die pressure was 5 atm. leading one to believe that this is where pressure was measured in the reference. The pMMA had to be~force fed to keep the system running. The ammonia rate was increased to 10 cc/min. but the pressure dld not lncrease.
No imidization was observed in any of these attempts .
to repeat Example 7 of the reference.
EXAMPLE ~2 - (Comparative~
A In accordance with the invention, an 0.8" Welding Engineer's twin screw extruder havin~ the configuration de-scribed in Examples 1-6 is used to completely imidlze a pMMA
25~ having a ~ ~ ~ DMF of 1.65 with non-aqueous ammonia under a pressure of 53 atm. and temperature of 260-2700 C. at a point about 1/3 the way down the screw. A vacuum of 0.9 to 0.001 is applied to the vacuum vent.
A smooth, continuous product strand exits the ex-truder. The product does not require drying, and it can be ~f~

.Lul~her pro((~;(.e(l wi-thout in-torme~(.l.l.a-te step.. No am~o:nia ven-ts into the cnvironment, and all by-proclucts are re-pl.acea ble .
The prodllct is poly(glu-tarimide), and is -tested for the:rmcll stabili-ty by the dynamic-thermo~ravimetric analysis method (TGA) wi-th results reported in Table 2. .
B. To show the cri-tical importance of the amine being non-aqueous and the subatmospheric pressure being applied to at least one vent port~ a comparative experiment was con-ducted using the same conditions of A, supra, but using aqueous ammonia (NH3/H20 ratio 80/20 by wt.) and plugging the vacuum vent. The produc-t exited the extruder in foamed, dis-continuous masses propelled by -the ammonia pressure at high .velocity and was stopped by a shield mounted about L~ ~eet ~rom the ex-truder die. Large quan-ti-ties of ammonia vented from the die in-to the environment. The product was ground to a fine powder and had to be dried. It was vacuum dried at 1200 C.
for 16 hours and tes-ted for thermal stability by dynamic TGA.
Iwith the results reported in Table 2.
Although the products produced in accordance with the inventi.on (A, supra) and in this comparative experiment, B, both had equal degrees of imidization (lO0~) and melt viscosity~
the comparati.ve experiment produced a product which was sign-ificantly less thermally s-table than the analogous product of 2~ the invention. The results in Table 2 imply -that at typical processing -temperatures, around 300 C., product A only loses around 1% of its weight, whereas product B loses over 2~.
This difference can mean the difference between a no bubble, smooth surfaced product and a bubble-containing,rough-surfaced product.

s~

;
.TA[3i,E 2 TIIERMAL SrrABILIrrY
DYNAMIC TGA ~ TEMP . INCREASE RATE
200 C~/min.

% Weight Temp.~ oC~ Air or Ni-trogen, at which total Loss wt loss is as indicated AIR NITROGEN
A B A B
285 100 3 105 : ~:
2 370 175 l~oo 275 3 385 350 L~L~0 385 :
::
t 395 380 L~20 405 L~o 390 L~20 410 :

; NOTE: A - represents invention B~ - is comparatlve :

:

:
: : :
;:.~ ~ :

-, .:

.

E~AMPLE ~
This example compares the polymers prepared in Graves U. S. Patent 2,146,209,and Schroder et al U.S. Patent 3,284,425 with the polymers of the invention.
~ ~ 9~
The polymer prepared in Examples I and II of the Gravec Patent are supposedly polymethacrylimides. However, accord-ing to these Examples the polymers actually produced were soluble in dilute ammonia and boiling methanol. The poly-glutarimide polymers of the present invention are insoluble in dilute ammonia and insoluble in boiling methanol, The Graves product appears to be a copolymer of methacrylimide~
methacrylamide, and ammonium methacrylate, B, SCHR~DER_et al Autoclave For purposes of comparison7 Example 1 of U~ S~ate~t 3,284,425 is repeated using 120 parts polymethyl methacrylate ~ - -heated ~or 7 hours at 2300 C. in a Parr stirred autoclave with - :~
~ 129 parts of a 33 1/3~ aqueous solution of methylaminç and ~ .
j780 parts water, A pressure~of 31 atm. develops. The ~ ~
reaction product comprises a watery phase and 32.7 ~arts of a ~`
solid polymer which was washed and analyzed to have a nitrogen content o~ 8,5 + 0~2~. ,The 32,7 parts represents 34.6% of the i~itialcharge, The Schroder polymer is compared to the polymethyl-methacrylate/methyl amine reaction product prepared ln the extruder in accordance with the invention with the results reported in Table 3.

. -These data show -that the Schroder et a:L polymer is cl.e(lrly less ~hermally stable i;han the polymer p:repa:red in accorclance with the lnvention; the Schroder et al polymer exhibi-ts weak, ill-defined glass trans:ition -tempera-ture as I compared to the polymer of the invention; and it begins to so~ten at a lower -tempera-ture (DTUFL and Vica-t). The trans-lucency o~ -the Schroder e-t al material seems -to indicate a non~uniform imide level, as compared to the transparent, and hence uni~orm, polymer of the invention. The difference in water resistance indicates lnferior properties of the Schroder et al polymer.

::

.

Six and one-half parts of the poly(glutarimide) polymer produced in accordance with Example 18 are blended with three and one-half parts of the MBS impact modifier produced in accordance with Example 1 of U.S. Patent No. 3,985,704 of D.H. Jones et al, and 0.5 weight percent antioxidant at 460 510F. in a vacuum~vented single screw extruder to produce translucent strands which are then pelletized, dried at 90C.
and injection molded at extrusion temperatures. The polymer 10 blend produced had a Vicat of 185C., a DTUFL (C.) oE 180 (66 psi), 160 (264 psi), and 170 (264 psi annealed). The pxoduct had a notched Izod impact strength of 1.1 ft.-lbs./in.
and tensile modulus of 4 x 105, tensile strength of 9 x 103 psi at break.

Compositions similar to that of Example 4 except for using the impact modifier produced in accordance with Example 1 of V.S. Patent 3,808,180 with imide to modifier ratios of 3/2 and 1/1 gave similar results. Substitution of MBS
and ABS modifiers gave excellent balance of properties.
EXAM LE` 56 A composition as per Example 54, except with the ratio of poly(glutarimide) to MBS moaifier of 6 parts to 4 partsr ga~e translucent articles having the following proper-ties, Vicat 135C.; DTUFL 120C. (66 psi), 100C. (264 psi);notched Izod 205 ft.-lbs./in.; tensile modulus 3 x 105 psi;
tensile break strength 6 x 103 psi.
.~.

' '"`;~
~; ' . `

E,YAMP~
E~ample 54 ~as repeated exceptfor substituting one part of polycarbonate for one part polyglutarimide, pro-ducing opaque polymer blends having the following properties, jVicat 170 C.; DTUFL 170 C. (66 psi), 135 C. ~264 psi), I45 C. t264 psi, annealed); notched Izod 2.1 ft. lbs./in.;
tensile modulus 3 x 105 psi; tensile break strength 7 x 103 psi .

Example 54 was repeated except for using 5.9 parts polyglutarimide to 4.1 parts impact modifier, and substituting for the MBS impact modifier one of the following formula:
Bd/St//MMA//St//MMA/AN/St: 71/3//3//11//4/4/4.
The properties of the resultant blend were as follows: Vicat 160 C.; DTUFL 1470 C. (66 psi), 140 C.
(264 psi); notched Izod 1.5 ft. lbs./in.; tensile modulus 3 x lO ; tensile strength at break 8 x 103 psio : , .

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Claims (38)

CLAIMS:

1. Method for producing a polymer containing imido units comprising reacting under substantially anhydrous conditions in an extruder an acrylic polymer with ammonia or a primary amine at a temperature of about 200 to 450°C.
while applying subatmospheric pressure to at least one vent port of said extruder.

2. Method of Claim 1, wherein said anhydrous ammonia or primary amine is introduced through an extruder addition port at a pressure of about atmospheric to 1000 atmospheres.

3. Method of Claim 1, wherein the average residence time is 0.1 to 1000 seconds.

4. Method of Claim 1, wherein the degree of imidization is controlled by control of the average residence time and temperature.

5. Method of Claim 1, wherein the temperature is about 300 to 375° C.

6. Method of Claim 1, further characterized as being carried out in the absence of a solvent.

7. Method of Claim 1, further characterized as carried out in the absence of a catalyst.

8. Method of Claim 1, wherein anhydrous ammonia is introduced through an extruder addition port at a pressure of about atmospheric to 500 atmospheres, the average residence time is maintained at 30 to 300 seconds, a partial pressure of about 0.9 to 0.01 is applied to at least one vent port, the temperature is maintained at about 325 to 375° C., and the reaction is conducted in the absence of solvent.

9. Method of Claim 1, wherein a partial pressure of about 0.9 to 0.01 atmospheres is applied to said vent port.

10. Composition comprising the polymer product con-taining imide units produced by the method of Claim 1.

11. The composition of Claim 10 in the form of a sheet, rod, tube, powder, granule, or molded article.

12. The composition of Claim 10, wherein the polymer comprises a multiple stage polymer containing imide units in the outer stage of said multiple stage polymer.

13. The composition of Claim 10, wherein the acrylic polymer is a blend of single stage and multiple stage polymers, and the polymer containing imide units is a blend of a single stage polymer and multiple stage polymer containing imide units in the outer stage.

14. The composition of Claim 13, wherein the multi-stage polymer containing imide units comprises about 10 to 60% by weight of the blend.

15. The composition of Claim 10, wherein the polymer containing imide units has an intrinsic viscosity, [? ] DMF, of about 0.01 to 7Ø

16. The composition of Claim 10, wherein the polymer containing imide units further contains acrylic units and the numerical ratio of imide units to acrylic units is about 1:2 to about 9:1.

17. The composition of Claim 10, wherein 95 to 100%
of the polymer units are imide.

18. The composition of Claim 10, wherein 1 to 35%
of the polymer units are imide.

19. The composition of Claim 10 further including an impact modifier.

20. The composition of Claim 19, wherein impact modifier is a multiple stage polymer.

21. The composition of Claim 20, wherein the impact modifier selected from the group consisting of MBS, ABS, and all acrylic.

22. Composition comprising a thermoplastic polymer containing imide units of the structural formula wherein R1, R2, and R3 independently represent hydrogen or C1 to C20 unsubstituted ox substituted alkyl, aryl, or mixtures thereof, said polymer being further characterized as non-cross-linked and soluble in dimethyl formamide, and having a degree of thermal stability as measured by TGA in an air atmosphere wherein the temperature at which said polymer has a 1% decom-position is above 285°C.

23. The composition of Claim 22 further including an impact modifier.

24. The composition of Claim 23, wherein said impact modifier is a multiple stage polymer.

25. The composition of Claim 24, wherein the impact modifier is selected from the group consisting of MBS, ABS, and all acrylic.

26. The composition of Claim 22, wherein the thermo-plastic polymer is a multiple stage polymer containing units of said structural formula in the outer stage.

27. The composition of Claim 22 comprising a blend of a single stage thermoplastic polymer containing imide units of said structural formula and a multiple stage polymer containing imide units of said structural formula in the outer stage.

28. The composition of Claim 27, wherein the multi-stage polymer comprises about 10 to 60% by weight of the blend.

29. The composition of Claim 22, wherein said thermo-plastic polymer further includes units from other ethylen-ically unsaturated monomers.

30. The composition of Claim 22, wherein said thermo-plastic polymer has an intrinsic viscosity, [? ]DMF, of about 0.1 to 7Ø

31. The composition of Claim 22, further characterized as being soluble in tetrahydrofuran and dimethyl sulfoxide.

32. The composition of Claim 22, in the form of sheet, rod, tube, powder, granule or molded article.

33. The composition of Claim 22, wherein the polymer containing imide units further contain acrylic units and the numerical ratio of imide units to acrylic units is about 1:2 to about 9:1.

34. The composition of Claim 22, wherein 95 to 100%
of the polymer units are imide.

35. The composition of Claim 22, wherein 1 to 35%
of the polymer units are imide.

36. The composition of Claim 22 in which said polymer has a degree of thermal stability as measured by TGA in an air atmosphere wherein the temperature at which said polymer has a 1% decomposition is at least about 365°C.

37. The composition of Claim 22 wherein said polymer is the reaction product of ammonia or a primary amine with an acrylic polymer containing units derived from esters of acrylic acid or methacrylic acid.

38. The composition of claim 37 in which said polymer has a degree of thermal stability as measured by TGA in an air atmosphere wherein the temperature at which said polymer has a 1% decomposition is at least about 365°C.