IL25244A - Process for the manufacture of linear polyamides - Google Patents

Description

PATENTS FORM O.

PATENTS AND DESIGNS ORDINANCE S PE CI FI C A TIO "PROCESS FOR THE MANUFACTURE OF LINEAR POLYAMIDES " We, ICI FIBRES LIMITED, a British Company of Pontypool, Monmouthshire, England DO HEREBY DECLARE the nature of this invention and in what manner the same is to be performed to be particularly described and ascertained in and by the following statement : - The present invention relates to a continuous process for the manufacture of high molecular weight linear polyamides by the condensation polymerisation of defined monomers which are omega-amino carboxylic acids or polymethylene diammoiiium salts of dibasic acids, said acids and salts being aliphatic but optionally containing phenylene links in the carbon chain.

It is known from British Patent Specification Ko.924 > 630 to manufacture high molecular weight linear polyamides continuously by the condensation polymerisation of a monomer which is a polymethylene diammonium salt of an aliphatic alpha, omega dicarboxylic acid containing from 8 to 24 carbon atoms or which is an omega-amino aliphatic carboxylic acid containing from 6 to 12 carbon atoms, by a process comprising pumping an aqueous solution of said monomer into the entry end of a long narrow tube having an internal diameter not exceeding 2.5 cm heated to polymerisation temperatures so that the material polymerises as it passes through the tube, wherein the pressure is at least 14 atmospheres at the entry end of said tube, continuously decreases along the tube and falls to substantially atmospheric or substmospheric pressure at the exit end of said tube but always permits the evolution of steam which is derived from the aqueous solution or the water of condensation, and at any point in the tube has a value constituting a continuous monotonic single value function of the distance of said point along the tube, the rate of passage of the polymerising material through the tube being such that a-t least JQffo of the total theoretical water of chemical condensation is evolved during said passage.

In British patent there is claimed the application of the above process in a tube having an internal diameter not exceeding 3 · 5 cm to the manufacture of certain defined aryl-polyamides, namely those derived from a monomer which is a diammonium dicarboxylate salt derived from a diamine of formula and a dicarboxylic acid of formula H00C-Y-CO0H or which is an aminocarboxylic acid of formula NH2-Z-C00H, X designating a chain of p methylene groups containing, not joined directly to nitrogen, q meta- or para-phenylene links, Y a chain of r methylene groups containing s meta- or para-phenylene links and Z a chain of t methylene groups containing, not joined directly to nitrogen, u meta- or para-phenylene links, wherein p, q, r, s, t and u are positive integers, q and s being the same or different are each zero, 1 or 2 but Hither q or s is at least 1, u is 1 or 2, p is at least 6 if q is zero but at least 2 if q is not zero, r is at least 4 if s is zero, the sum of p and r is at least 6 and t is at least 3, X> and Z optionally bearing substituents and optionally containing -0- links in the chain, providing the groupings -0-0-, -O-CI^-IT^ and -O-CH^-CH^-C0- be absent.

The above processes are satisfactory for rather modest outputs of polyamide. Indeed the fact that tubes of relatively small manufacturing capacity can be operated efficiently makes these processes most attractive for this purpose. The rate at which polyamide can be manufactured in a given tube naturally depends on the degree of polymerisation required. Preferably for melt-spinning into textile filaments the polyamide should possess a degree of polymerisation of at least 72. This degree of polymerisation corresponds in the case of polyhexamethylene adipamide to the elimination of 8"2$ of the water of condensation. Polyamides of this degree of polymerisation can efficiently be produced by the above processes at rates of approximately 10-15 kgm per hour, by means of tubes having a length in the region of 100 metres.

The simplicity of the tube apparatus employed in the above process and consequent economy in running expenses made it desirable to extend the processes to larger outputs. The attainment of this goal has however proved to be by no means easy for the following reasons.

In general if the rate of pumping of the monomer solution into the tube, that is to say, the rate of throughput, is increased, the pressure in the tube is increased and the time of residence in the tube or time of reaction reduced. For both these reasons the degree of polymerisation obtained decreases. Attempts to lengthen the time of reaction by lengthening the tube cause an even greater rise in pressure and thus defeat their object. It is thus necessary to increase not only the length but also the diameter of the tube. But here another difficulty is encountered for if a tube of too great a diameter be used, the reaction mass forms slug-like droplets filling short sections of the tube (like the ?ater in an air-lift water pump) and ceases to run steadily through the tube. As a result the pressure becomes erratic and an excessive quantity of diamine is lost. Unsuitable design of tube, especially in the case of higher outputs of polyamide, may aleo lead, apart from the slugs just mentioned, to a number of evils including excessive drop in pressure, erratic pre sure, excessive degradation of polymer, the formation of gel and undue loss of diamine.

Intensive research has now demonstrated that rates of production of polyamide of a larger order of magnitude, for example 50-100 kgm per hour or even 250 kgm per' hour can successfully be attained by means of tubes, or, in other words, elongate reaction zones, exceeding 1 0 metres in length, provided the dimensions (i.e. diameters) of the tubes or elongate reaction zones are carefully designed so as to fall within certain rather narrow limits. By elongate reaction zones are meant (in accordance with the dictionary meaning of the word "elongate") reaction zones which are notably long in comparison to their width or diameter. 'The present elongate reaction zones may possess a circular or non-circular cross-section, provided that in the latter case the largest axis or diameter does not exceed four times the smallest axis or diameter. Accordingly whenever the diameter, i.e. the diameter of the cross-section, of the elongate reaction zone at any point along its length is referred to, the term "diameter" is to be understood, in the case of elongate reaction zones of non-circular cross-section, as referring to the diameter of a circle which would have the same area as the non-circular cross-section in question.

Naturally the size or volume of the tube or reaction zone required depends on the desired rate of output. Moreover the diameter of the elongate reaction zone must increase gradually and/or in one or more stages from the inlet end of the zone to the outlet end thereof, but never decrease. The shape of the elongate reaction zone can be envisaged as defined by the diameters thereof all the way along its length. Research has elucidated two relationships regarding these diameters and thus enabled a range of successful polymerisation processes to be worked. Firstly it has been found that the diameter at any given point in the reaction zone is related to the throughput or rate of output of polymer. Secondly there is a relationship between the diameter of the elongate reaction zone at any given point along its length and the volume of the reaction zone from the inlet end thereof up to that point. These relationships can b ascribed to the nature of the polymerisation process including the changes in pressure, viscosity of reagents etc. associated therewith and also the mode or pattern of flow of the materials in the reaction zone or tube. In fact the said materials constitute a two-phase system inasmuch as they comprise steam and molten (unfinished) polya id There is a number of established patterns of flow for such two-phase systems in tubes (see Advances in Chemical Engineering, ^3 > Academic Press, N. York & London Volume IV, p.207) of which a well-known (but little understood) one is the annular pattern. The latter is found to be the mode of flow in the present process, ?rtierein the molten polyamide streams along the tube in the form of a molten layer on the internal surface thereof while the steam rushes along the centre 5 of the tube. The above relationships can be quantified and the elongate--- reaction zone according to the present process thus precisely defined in the following manner.

Definition of symbols relating to present polymerisation process Q = rate of output of polyamide (throughput) in kilograms per hour V = total volume of the reaction zone in cubic centimetres v = volume of the reaction zone from its inlet end up to a given point along its length in aubic ■ 5 centimetres d = diameter of reaction sons at any given point along its length in millimetres d = maximum diameter of reaction zone at any given max· point along its length in millimetres 2 ^0 dmm. . = the minimum value of the above diameter a = f(v/Q,), this function being defined below It will be evident that T/Q, denotes the total volume of the reaction zone per unit of output and that v/¾ designates the volume of the reaction zone from its inlet end up to a given point per unit of throughput.

Nov/ it has been found that for the polymerisation process to run successfully the total volume V of the reaction zone must have a value falling within the range of from 1600Q to 3600Q. In other words successful reaction zones have a total volume of from 1600 to 36ΟΟ cc Per km per hour of output. Preferably V equals from 2000Q, to 3000Q.

It has further been found that if the output Q is to be altered and the shape of the reaction zone maintained the same, then the diameter thereof at any given point along its length must be varied nearly proportionally to the cube root of the output.

Thus ( 1 ) d*^36 d 0< Q0-36 ■ By taking logarithms to the base 10 of both sides of the equation one obtains s ( 2) lo 1Qd = a + 0. 36 lo 1QQ wherein N.B. The logarithmic suffix 10 will henceforward be omitted, since all logarithms in the specification are to the base 10.

At any given point along the length of the reaction zone the invention prescribes a range of values for d. The diameter of the zone must fall within this prescribed range for the polymerisation reaction to be successful. This range is defined by equations Nos. '4 and 5 of which NO. 4 gives the maximum value of a and No. 5 the minimum value of a:- ( 4) a = 1 .00 + tan-1 (v/l 0Q - 40 ) ( 5 ) a = Ο.67 + ¾ tan"1 (v/500Q - 2) N.B. Throughout the specification it is to be understood that the principal value of the inverse tangent (i.e. tan ) expressed in radians is intended to be understood.

Equations Nos. and 5 thus give the maximum and minimum values of the function in equation No. 3 · B substituting these values for a in equation No. 2 , equations Nos. 6 and 7 are obtained which give the maximum and minimum values of d, that is to say they define the range of d according to the invention. ( 6) log d = 1 .00 + O. 43 tan"1 (O.I V/Q, - 40) + 0. 36 log <¾ Equation No. 6 shows how the maximum value of d varies along the length of the reaction zone, since, plainly d is a function of v, which itself so varies, in accordance with its definition already given.

Similarly equation No. 7 shows how the minimum value of d varies along ^ the length of the reaction zone.

These relationships can be expressed graphically as shown in the accompanying drawing of a graph in which the variation of d with v is illustrated, ¾ being assigned the value, for example, of 100.

(Cartesian co-ordinates only admit of two variables in one plane, •jQ usually termed x and y) . When Q = 100 , equations Nos. 6 and 7 become respectively : - (8) log d = 1 . 72 + O. I 43 tan*1 (0.001 v - 40) niclX ( 9) log dmin = - 1 .34 + Ο.25Ο tan"1 (0.00002 v -2 ) On the y axis log d is plotted and on the x axis V/Q, that is to say 1 5 (when Q = 100 ) v/lOO. A-B is the graph of equation No. 8. C-D is the graph of equation No. 9 · Both graphs exhibit inflections which is characteristic of tan functions. Both graphs terminate at a maximum reaction zone volume of 36ΟΟ cc. per unit of output, since the maximum total volume V of the reaction zone is, as already stated, 36OOQ,. The area enclosed between the graphs A-B and C-D consequently embraces all the permissible values of log d according to the invention.

Thus at any given point in the reaction zone, for example, where v/Q, that is to say v/lOO (since the graphs are drawn for Q, = 100) has a value of 800, the range of values of log d corresponds to the vertical such as 2^ intcrcept/E F. In other words the range of values for log d at the point in the reaction zone where v/l 00 = 800, i.e. v = 80,000 cc. is from 1.3 to I.92.

In fact the graph, subject to its ordinates being logarithmic and its abscissae measured by volume illustrates the profiles of the elongate reaction zones according to the invention for ¾ = 100.

As mentioned, only two variables can be shown in such a graph, but equations Nos. 6 and 7 embody the general definition of d in terms of v and ¾.

Definition of elongate reaction zone The elongate reaction zone according to the invention is therefore defined by the following four conditions (the symbols having the meanings already assigned to them):- I. d increases gradually and/or in one or more stages, but never decreases, as v increases.

II . V has a value from 600¾ to 36OOQ,.

III. (Equation No. 6) log d = 1 .00 + 0.1 43 tan~1 (0.1 V/Q - 40) + Ο. 36 log ¾.

IV. (Equation No. 7) log = Ο.67 + 0.250 tan" ( 0.002 v/¾ - 2) + Ο.36 log ¾.

Preferred dimensions of elongate reaction zone It is preferred that V has a value from 2000Q to 3000Q.

It is also preferred that log d be equal to the arithmetic mean of log d and log d . plus or minus 0.05 · max mxn -"■ Accordingly the invention consists of a continuous process for the manufacture of high molecular weight linear polyamides by the condensation polymerisation of a monomer which is a diammonium "dicarboxylate salt derived from a diamine of formula NH^- -NH^ and a dicarboxylic acid cf formula HOOC-Y-COOH or which is an aminocarbbxylic acid of formula N^-Z-COOH, X designating a chain of p methylene groups containing, not joined directly to nitrogen, q m- or p-phenylene links, Y a chain of r methylene groups containing 3 m-or p-phenylene links, Z a chain of t methylene groups containing, not and t are .joined directly to nitrogen, u m- or p-phenyl,ene links, wherein , &ψ = different are each zero, 1 or 2, r> is at least 6 if q is zero and s is u not zero but at least 2 if Examples of suitable monomers for use in the present process are listed elovr. Particularly important ares- hexamethylene diammonium adipate hexamethylene diammonium sebacate hexamethylene diammonium suberate octamethylene diammonium adipate epsilon-amino caproic acid omega-amino undecanoic acid The following may also be employed decamethylene diammonium adipate pentamethylene diammonium sebacate dodocamethylene diammonium adipate hexamethylene diammonium azelaate dodecamethylene diammonium suberate p-(gamma-amino-n-propyl)phonoxyacetic acid l-p-(gamma-carboxy-ngpropyl)phenyl-2- aminoethane p-(gamma-carboxy-n-propyl)phenylmethylamine p-(delta-carboxy-n-butyl)phenylmethylamine p-(beta-aminoethyl)phenyl-n-valerio acid There may likewise ba employed diammonium dicarboxylate salts containing phenylene groups which are derived from the following pairs of diamines and dicarboxylic acids. diamine gamma- (p-gainma-amino-n-propylphenyl) -n-propylamine acid sebacic acid diamine 2 , 5-di(beta-aminoethyl) -p-xylene I j ;acid pimelic acid i :diamine di-(beta-aminoethyl) durene I acid 1, 16-hexadecane dicarboxylic acid I ;diamine p-di-(aminomethyl) benzene ;acid di(delta-carboxy-n-bu yl) oxide ;diamine beta- (p-aminoethylphenyl) ethylamine ■acid adipic acid diamine gamma- (p-beta-aminoethylphenyl) -n-propylamine iacid adipic acid ;diamine delta- (p-beta-aminoethylphenyl)-n-butylamine acid adipic acid diamine m-xylylene diamine acid azelaic acid ;diamine m-di-(beta-aminoethyl) benzene :acid adipic acid 'diamine di-(aminomethyl) mesitylene .acid azelaic acid •diamine 1 ,5-7-dioxadecane acid terephthalic acid diamine 3-ethyl-hexamethylene diamine acid terephthalic acid diamine 2 , 3-dimethylhexamethylene diamine acid terephthalic acid diamine hep amethylene diamine acid p-di-(beta-carboxyethyl) benzene diamine decamethylene diamine acid 2 ,5-di-(beta-carboxyethyl) -p-xylene diamine decamethylene diamine ;acid p-di-(beta-carboxyethyl) benzene diamine hexamethylene diamine \ acid p-(beta-carboxyethyl) phenyl acetic acid :diamine I decamethylene diamine ■acid \ 1 , 2-di-(p-carboxymethoxyphenyl) ethane diamine i nonamethylene diamine :acid 1 terephthalic acid 1 d amine dodecamethylene diamine acid terephthalic acid j diamine 1 , 6-diainino-3-methyl-n-hexane acid terephthalic acid diamine hexamethylene diamine acid p-di-(beta-carboxyethyl) benzene diamine hexamethylene diamine acid p-di-(gamma-carboxy-n-propyl) benzene diamine hexamethylene diamine acid p-(gaiania-oarboxy-n-propyl) phenylacetic acid diamine hexamethylene diamine acid isophthalic acid diamine hexamethylene diamine acid di-(m-carboxyphenyl) methane : diamine p-di(gamma-amino-n-propyl) benzene acid p-di-(beta-carbox ethyl ) bensene di mi e p-di(gamma-amino-n-propyl) benzene acid p-di (carboxymeth l) benzene Especially preferred are those diammonium dicarboxylate salts containing phenylene groupa which are derived from terephthalic acid, isophthalic acid or p-di-(beta-carboxyethyl) - benzene and/or from one of the followin diamines : p-xylylene diamine m-xylylene diamine 2 , 5-di(beta-aminoethyl) -p-xylene di-(beta-aminoethyl) durene m-di(beta-aminoethyl) benzene p-nethyl-m-xylylene diamine di-(aminomethyl) mesitylene di-(aminoethyl) mesitylene 1 ,3-dimethyl-4j6-xylylene diamine By employing a mixture of two, three or more monomers in the above process interpolyamides may be made. Examples of suc mixtures are the following.

No. Mixture of monomers SM0I.56 salt hexamethylene diamine and 60 ' from p-di-(beta-carboxyethyl) benzene salt hexamethylene diamine and 40 from beta-(p-carboxymethylphenyl)propionic acid salt hexamethylene diamine and from p-di-(beta-carboxyethyl) benzene salt hexamethylene diamine and 90 from beta-(p-carboxymethylphenyl) propionic acid salt hexamethylene diamine and 60 from p-di-(beta-carboxyethyl) benzene 3. salt hexamethylene diamine and 40 from sebacic acid Small amounts of the order of a few per cent of other polyamide forming monomers, e.g. Ν,Ν' - piperasine-di-( amma) -n-propylammonium adipate may also be employed in conjunction with the above monomers. There nay also be added to the reaction mixture bifunctional or monofunctionai compounds in small quantity, notably monoamines or monobasic acids, e.g. acetic acid, in order to prevent polymerisation proceeding beyond the desired decree at elevated temperatures, for example, when the polyamide is held molten for the purpose of melt-spinning. Such monofunctionai compounds are known as viscosity stabilisers. Other adjuvants may also be added at any convenient stage of the process for instance:- dyes, pigments., dyestuff formers, heat stabilisers, light stabilisers, plasticisers, delustrants, polyamide and other resins.

For making a given polyamide it is found in practice that a temperature at least 10°G. above the melting point of the polyamide can be regarded as a suitable polymerisation temperature i.e. a temperature at which amide fornation proceeds at a useful rate, provided it be not too high otherwise degradation of the polyamide is likely to occur. The temperature of the polymerising material is preferably not allowed to fall as it passes through the elongate reaction zone. It is convenient that the whole zone be at one uniform temperature. The temperature is advantageously from 275°C to 300°C.

The mixture of monomer and water should constitute a strong solution or suspension and contains preferably at least &£f/o by weight of monomer. Furthermore suspensions of monomer are desirably heated so as to bring about solution ; in any case sufficient water should be present to dissolve the monomer at polymerisation temperatures.

The elongate reaction zone, conveniently contained by a tube, may possess any convenient shape, e.g. a helix positioned vertically or horizontally. The vertical helix can be traversed by the polymerising mass in an upward or downward direction. The material of which the tube is constructed is preferably one not subject to corrosion by the polymerising mass and may be, for instance, stainless steel. The tube must be capable of withstanding a high pressure which may, for example reach 28 atmospheres at the inlet end. __. The invention includes melt-spinning the above polyanides into filaments, films, ribbons and like lengthy extruded objects and the said objects when so melt-spun.

Conventional processes for the melt-spinning of polyamides are normally effected at a temperature of about 240-300°C. Higher temperatures are inconvenient both iron an engineering point of view and because they are apt to cause the polyamide to become degraded by oxidation and/or decomposition. Whilst many of the present homopolyamides melt at a very convenient temperature, it is to be noted that the interpolyamides in general melt at a lower temperature than do homopolyamides. Moreover in the case of a homopolyamide, the melting point of which is o the high side, it is always possible to lower the melting point by the admixture of a suitable plasticiaer. Such plasticisers should be devoid of halogen and must contain no ester grouping. Examples of plasticisers that may usefully be employed are phenols, medium and high boiling glycols and sulphonamides for instances- 1 , 12-di(p-hydroxyphenyl) -octadecane 1 ,8-di(p-hydroxyphenyl) -octadecane 2 ,8-di(p-hydroxyphenyl) -nonane 1 , 0~di(p-hydroxyphenyl)-decane 2 , 15-di(p-hydroxyphenyl) -hexadecane hexamethylene glycol 2-ethylhexane diol- ,3 3-methylhexane diol-1,6 3-methoxy-3-ethylhexane diol-1,6 2-ethyl-4-ethoxypentane diol-1 ,5 N-ethyl-o-toluene sulphonamide N-butyl-p-toluene sulphonamide -T-phenylcyclohexane sulphonamide N-diamyl-p-toluene sulphonamide Examples of elongate reaction zones Elongate Reaction Zone A It is desired to construct an elongate reaction zone of stainless steel tubing of two internal diameters, viz. 14 mm. and 45 nm. a length of the former to be followed by a length of the latter. The tube is to produce polyamide at a rate of 45 kgm. per hour (i.e. a = 45) .

Clearly in this case d will increase in one stage as v increases. Q = 45· Substituting this value in equations Nos. 6 and 7, the following equations are obtained (10) log d = 1.S0 + 0.143 tan"1 (0.0022 v - ITlclX 40) (11 ) log dmin = 1.27 + 0.250 tan"1 (θ.0000 v - 2) At the inlet end of the reaction sono v = 0. Substituting- this value in equations Nos. 10 and 11 one obtains log d = 1.38, hence d = 24.0 mm. max max log d . = 0.99, hence d . = CJ.8 mm. mm ism The permissible range of diameters at the inlet end is therefore from $,6 to 24.0 mm. Values for CL and d can be calculated from the above equations for any value of v and a list of such values is tabulated below.

V : lO d d log d . d . max max mm mm 0 ; 1.38 24.Ο Ο.99 9-8 9000 j 1.38 24.Ο 1.02 '> IO. 8000 I . 35.5 1.05 : .2 21100 \ 1.80 63.1 1.06 ! .5 36000 1.82 66.1 1.17 ■ 14.8 54ΟΟΟ j 1.82 66.1 1.36 j 22.9 72ΟΟΟ 1.82 66.1 1.49 3Ο. 9OOOO ; 1.82 66.1 1.55 \ 35.5 108000 1.82 66.1 1.58 1 38.0 162000 ! 1.82 66.1 1.62 ' 41.7 The tube of 14 mm. diameter may be employed for the first 21100 cc. of the reaction aone, since the range of values for d at v = 21100 cc. is from 11.5 mm. up to 63.1 mm. At v = 36ΟΟΟ cc. however the not be employed for so large a volume of the reaction zone, In fact the maximum volume of the reaction zone which could be accommodated in the tube of 4 mm. diameter is found by substituting d = 14·0 in equation No. 11 and calculating v, the corresponding value of which is 336ΟΟ cc. From the aforesaid limits of d at v = 21100 cc, namely 11.5 - 63. mm. it is clear that the 45 mm* tube may be employed at this point on the reaction zone. The maximum possible volume of the reaction zone is V = 36001 = 162000 cc. The above table shows that 45 mm. is within the permissible limits of zone diameter from v= 21100 cc. onwards.

Since t_e internal area of cross-section of the tube of 1 mm. diameter is 1.54 sq. cm. the length which accommodates 21100 cc. is 137 metres.

The prescribed total volume V of the reaction zone is from I6OOQ to 3600Q,, that is, from 72000 to 162000 cc. Consequently the volume of the tube of 45 mm. diameter must lie in the range from 72000 -21100 = 0 OO cc. to 162000 - 21100 = 120900 cc.

Preferably the total volume of the reaction zone is from 2000Q. to 3000Q i.e. from 90000 to 135000 cc. If the preferred limits are observed then the tube of 45 mm. diameter must possess a volume of 68900 to I39OO cc.

A volume of 82700 cc. is chosen for the tube of 45 mm. internal diameter. The length of this tube may easily be calculated to be 52 metres. The total volume V of the reaction zone is therefore 21100 + 82700 = 103800 cc.

The elongate reaction zone is consequently contained in 137 metres of tube of 14 mm. internal diameter joined to 5 metres of tube of 45 mm. internal diameter. This combined tube which is of stainless steel, will be referred to hereinafter as Tube A Application of Tube A to output of 36 kgm. per nr.

The preferred total volume of the elongate reaction zone for an output of 36 kgm. per hour (i.e Q = 36) is from 2000Q to 3000Q, i.e. from 72 , 000 to 108, 000 cc. ¾e total volume V of Tube A is 1 24900 cc. which does not comply with the above preferred limits; it does however fall within the range of volume prescribed according to the invention, namely, from I6OOQ, to 36OOQ i.e. from 57 , 600 to 1 29 , 600 cc.

Substituting Q = 36 in equations Νοε. 6 and 75 one gets the following equations. (12) log d = 1 .56 + 0.143 tan-1 (θ.00278ν - 40) πιειχ ( 1 3) log d = 1 .23 + Ο.25Ο tan-1 (θ.0000555ν - 2 ) The values for d and d . at v = 0 , 21100 and 103800 are found max mm from these equations to be as follows.

V log d d log d . d . max max : B mm mm 0 1.34 21.9 Ο.95 8.9 21 100 1.78 6Ο. 3 I.06 11. 5 ; 103800 1.78 6Ο. 3 1.56 36.3 The values for d in Tube A namely 1 4 mm. from v = 0 to v = 21100 and 45 mm. from v = 21100 to v = 1038C0 fall within the prescribed ranges.

Elongate Reaction Zone B.

Using stainless steel tubing of 1 7 mm. and 57 mm. internal diameter, one wishes to construct a reaction zone capable of an output of 100 kgm. polyamide per hour (i.e. Q = 100).

By substituting Q, = 100 in equations Nos. 6 and 7 > equations Nos. 8 and (already quoted above and illustrated in the accompanying graph aB AB and CD) are obtained s- (8) log d = I.72 + 0.143 tan-1 (0.001v - 40) ( 9) log d = 1. 39 + Ο.25Ο tan"1 (θ.00002ν - 2) It will be found that 203 metres of the narrower tube 1 mm. reaction zone according to the invention for the reasons given bel This combined tube will be referred to as Tube B.

Volume of narrower tube = 46,080 cc.

Volume of wider tube = 178, 500 cc.

Total volume = 224,580 cc.

Preferred total volume 2000·^ - 3000Q, i.e. 200, 000 - 300 , 000 cc.

Clearly 224,580 falls within this range.

By substituting v = 0 , 46Ο8Ο , and 224580 in equations No. 8 and > 'the permissible ranges of d which correspond, can be found, Thus from v = 0 to v = 46Ο8Ο 1 7 nun. falls within the range of diameters obtained from equations Nos. 8 and 9 whilst from v = 46Ο8Ο to v = 224580 the diameter 57 mm. is similarly appropriate.

Graphical Method That the diameters employed in Tube 3 fall within the range prescribed by the invention can also be ascertained by using the accompanying graph. The intercepts indicating the ranges of diameter are lettered as follows :- The logarithms of the diameters (log 17 = 1 .239 ; log 57 = 1 -.756) of tube B are plotted as the dotted line I - J - K - L. Inspection of the graph shows that the line I - J - K - L falls within the limits prescribed by the curve ASGB and the curve CFHD. Indeed one convenient plotting such curves and constructing the desired contour between then. For, as already pointed out, the curves, subject to the ordinates being logarithmic and the abscissae measured by volume, define the maximum and minimum profiles of the elongate reaction zones, in other words, the limits between which all the profiles of such zones according to the invention must fall.

Application of Tube B to output of 76 kgm. per nr.

The preferred total volume of the elongate reaction zone for an output of 76 kgm. per hour (i.e. Q, = 76) is from 2000Q to 3000Q, i.e. from 1 52 ,000 to 228,000 cc. Clearly the volume of Tube B which is 224580 cc. falls within this range.

By substituting Q = 7 in equations Nos. 6 and 7 > equations Nos. 14 &nd 15 are obtained:- ( 14) log d = 1 .68 + O. 43 tan"1 (θ.00 32ν - 40) ( 1 5) log d . = 1 .35 + Ο.25Ο tan"1 (θ.0000263ν - 2) mixi The values for d and d . at v = 0 , 46Ο8Ο and 224580 are max Bin found from these equations to be as follows.

The values of d employed in Tube B, namely 17 mm. from v = 0 to v = 460S0 and 7 mm. fr0m v = 46Ο6Ο to v = 224580 , fall well within the necessary ranges.

Consequently Tube B 13 suitable for an output of 7 kgm. per hour. Since Tube B also deals with 100 kgm. per nr., it can be taken that it is also suitable for any output lying between the values 7 and 00.

Elongate Reaction Zone C designed in stainless steel tubing having seven different diameters as listed below together with the cross-sectional areas, the volumes of the relevant sections, the values of v at the end of each section, and the lengths of the sections.

The preferred volume is 2000¾ - 3000Q, i.e. from 1000 ,000 to 1 500 ,000. The total volume of the reaction zone, 1425 > 000 , falls within this preferred range.

By substituting the value 500 for Q, in equations Nos. 6 and 7 > equations Nos. 1 6 and 7 are obtained. (16) log d = . 7 + O .I 4 tan"1 (0.0C02v - 40) (17) log = 1 .64 + 0.250 tan-1 (0.000,OO4 - 2) The values for d and d . for the above values of v including max mm v = 0 , are calculated from these equations and tabulated below, together with the actual values of d. It is clear that the latter fall within the prescribed ranges . log d d log d . d . max max 0 mm mm 0 1.75 56.2 1.36 22.9 - 3 I 100,000 1.75 56.2 1.39 24.6 33 > i 200,000 1.97 93.3 1.42 26.3 37, 47 I 300,000 2.19 154.9 I 1.47 29.5 47, 9 i 400,000 i 2.19 5 . \ 1.55 35.5 59, 74 I : 500,000 ! 2.19 154.9 i 1.64 43-7 74, 93 j 1525,000 2.19 4. 1.67 46.8 93, .118 1 ,425,000 ; 2.19 1 4.9 1.99 j 97-7 118 - Therefore the above tube having seven different diameters encloses an elongate reaction zone according to the invention. This tube will be henceforth referred to as .Tube C.

The following Examples are intended to illustrate not limit the invention. The parts and percentages are calculated by weight.

EXAMPLE 1 Tube A is maintained at 290°C by neans of a jacket containing a mixture of diphenyl and diphenyl oxide vapour (in the proportion of the eutectic mixture thereof).

A solution having the following composition is pumped through the tube at a rate of 90 kgm. per hour.

Composition of Solution 48.5fe hexamethylene dia monium adipate 0-3 hexamethylene diamine 0.1b acetic acid . water The rate of pumping corresponds to a rate of polyamide production of 36 kgm. per hour. The resulting polyhexamethylene adipamide has a degree of polymerisation of 82.

EXAMPLE 2 of 190 kgm. per hour tlirough Tube B, which is maintained at 20 C, the rate of output of polyhexamethylene adipanide being 76 kgm. per hour. 48.5 hexamethylene diammoniuin adipate 0.7l7° hexamethylene diamine O . C o acetic acid 50.73 water.

The resulting polyanide has a degree of polymerisation of 102.

Claims (5)

25244/ 2 Claims: 1. A continuous process for the manufacture of high molecular weight polyamides by the condensation polymerisation of a monomer which is a diammonium dicarboxylate salt derived from a diamine of formula H2~X-NH2 and a dicarboxylic acid of formula HOOC-Y-COOH or which is an amino carboxylic acid of formula NH2-Z-COOH. X designating a chain of p methylene groups containing, not joined directly to nitrogen, q^m- or p-phenylene links, Y a chain of r methylene groups containing s^m- or p-phenylene links, Z a chain of t methylene groups containing ( not joined directly to nitrogen, u^m- or p-phenylene links wherein p, and t are positive integers, r is zero or a positive integer, q, s and u being the same or different are each zero, 1 or 2, p is at least 6 if q is zero and s is not zero but at least 2 if q is not zero, r is at least 4 if q is not zero and s is zero, the sum of p and r is at least 6 and t is at least 5 if u is zero, but a t least 3 if u is not zero, X, Y and Z optionally bearing alkyl substituents and optionally containing -0- links in the chain, providing the groupings -0-0-, -O-CHg-N- and be absent, characterised in that the monomer mixed with water is pumped reaction through an elongate reaction zone, which/zone is defined by the conditions:

1. I. d increases gradually and/ or in one or more stages, but never decx'eases, as v increases II. V has a value from 1600 Q to 4400Q. ΠΙ. lo d = 1. 00 + 0. 143 tan 6 max 'V- 1 v/Q - 40) + 0. 36 log Q. a IV. log dmin = 0. 67 + 0. 250 tan_ 1(0. 002 v/Q -2 ) + 0. 36 log Q. wherein d = diameter of reaction z one at any given point along its length in millimeters wherein v - volume of the reaction zone from its inlet end up to a given point along its rlength in cubic centimeters wherein V = total volume of the reaction zone in cubic centimeters wherein Q = rate of output of polyamide (throughput) in kilograms per hour a n d heated to polymerisation temperatures. 25244/2

2. A continuous process as claimed in Claim 1, wherein the monomer is aliphatic.

3. A continuous process as claimed in Claim 1, wherein the monomer is epsilon aminocaproic acid.

4. A continuous process as claimed in Claim 1, wherein the monomer is hexamethylene diammonium adipate.

5. A continuous process comprising the manufacture of high molecular weight linear polyamides by a process claimed in Claims 1-4 and melt-spinning the resulting polyamide into filaments, films, ribbons and like lengthy extruded objects. Agents for Applicants