60

e f 50 0 M Y . - : a Y

Y 5 40 6l > D

30

"/' Dyeing temperatures 80, 85, 90°C No carrier + Phenol 0.02 rnol/l

0.08 mol/l x Phenylphenol

0.0015 mol/l 0 i_ 0.00075 mol/l 0

4 5 6 7 8 9 1 0 1 1 1 2

Figure 6 - Relation between dye uptake and structural parameter

J tan S dT

The variation of the structural parameters with tempera- ture is shown in Figures 4 and 5. When the maximum dye uptake is plotted against the structural factor, a linear relationship is found for all the experimental data confirming the validity of the hypothesis (Figure 6). The data (Tables 2, 3 and 4) show that the proportionality constant obtained by dividing the saturation dye uptake by the appropriate struc-

tural factor is almost constant, although it decreased by about 5% in going from a dyeing temperature of 80°C to 90°C. This is likely to be due to the small error in the tan 6 curves mentioned above, leading to an overweighting of the lower-temperature integrals.

CONCLUSIONS The work gives evidence for the assumption that the accessi- bility of the fibre for dye is related to the fraction of the polymer segments that are mobile. This fraction ideally would be the ratio of the integral from 20 to T2 and that from 20 to a high temperature. I f these are referred to as F and F then the saturation value becomes:

T2 T3

FT S=So X 2

T3 F

The evaluation of FT unfortunately is not possible because the instrument u&d in this study does not work above the boiling point of water. To calculate a dye's affinity at a particular temperature re uires a knowledge of S. It is

investigation. hoped that a calculation of K , a will form part of a further

RE FE RENCES 1. Gur-Arieh, lngamells and Peters, J.S.D.C., 92 (1976)

2. Rosenbaum, Text. Research J., 33 (1963) 899. 3. Beckman and Glenz, Melliand Textilber., 38 (1957) 783. 4. Balmforth, Bowers and Guion, J.S.D.C., 80 (1964) 577. 5. Beckmann, J.S.D.C., 77 (1961) 616. 6. Vogel, De Bruyne and Zimmerman, Amer. Dyestuff

7. Fukuda and Omori, Sen4 Gakkaishi, 27 (1971) 83. 8. Waters and Buchanan, Text. Research J., 47 (1977) 451. 9. Gulrajani and Saxena,J.S.D.C., 95 (1979) 330.

332.

Rep., 47 (1958) 581.

10. Asquith, Blair and Spence, J.S.D.C., 94 (1978) 49. 11. Smith, Polymer, 17 (1 976) 761. 12. Yanumet, PhD Thesis, Manchester, 1979.

The Polymorphism of C.I. Pigment Red I -

A Whitaker Department of Physics Brunel University Uxbridge M iddlesex

Thepolymorphism of C.I. Pigment Red I (1-[(4'-nitrophenyll- a201 -2-naphtholl in commercial samples has been inwsfigat- ed by interpreting their X-ray diffraction patterns. These have been compared with each other and with those from three wnglecrystal polyrnorphs (or, p and 7). It is concluded that commercial samples are predominantly o f either one or two phases (or or 7). There is evidence that a fourth phase (61 exists in powder form.

INTRODUCTION There are several cases of pigments being polymorphic, probably the best known are those of copper phthalocyanine and linear trans-quinacridone. However, polymorphs can also occur in other pigments [I] and can be important since the colour and other physical properties may be different with the various forms.

It is also possible that different manufacturers may unwittingly produce different polymorphs of the same pigment due to slightly different conditions (e.g. temperature or pH) in the manufacturing process. Hence, if a consumer changes his supplier he may obtain a product with different properties.

X-ray studies of single crystals of C.I. Pigment Red 1 (C.I. 12070) (see Figure 1 ) indicate that there are three polymorphs. Other polymorphs, which have not been isolat- ed as single crystals, may occur in powder form and their existence have been hitherto undetected. This investigation was started with a view to determine whether.they could be identified.

Fbure I - C.I. Pigment Red 1

436 jSDC Volume 98 December 1982

TABLE 1

Manufacturers of C.I. Pigment Red 1 Commercial

GS

FNC

HC HOR

IMP

KON

NSK PYO

Code Manufacturer Name

G Sieale & Co. GmbH Toner Red M _ - (nowkASF Farben & Fasern AG) Fabrication National de Colorantes Para Toner B SA Horace Cory 81 Co. Ltd Para Red 8576 NV Chemische Verfstoffenfabriek Paranitraniline vh LTh Red N-41 (now Ten Horne Pigment Chemie BV) Paranitraniline

Red 8559 Pa ran itrani line Red 20575

Imperial Color & Chemical Dept, A1 757 CP Para Hercules Inc. Toner Deep

A4329 CP Para Toner X Light Para Red Toner A491 1

Para Red Toner

H Kohnstamm & Co. Inc.

Sumitomo Chemical Co. Ltd *Unknown Pigmentos y Oxidos SA

R PT- 52

The &/our lndex lists this as Lake Brown BRA However, the manufacturer gives Lake Brown BRA to be C.I. Pigment Brown 2 (C I. 12071 1

There is a second consideration in the case of C.I. Pigment Red 1; over the last few years the number of manufacturers of the pigment has decreased, and purchasers may well have had to change their source of supply. For them, it may be

better to obtain an alternative supplier with a product similar to the discontinued one, so that the same colour standards may be maintained.

The investigation started by writing to all the manufac- turers listed in the Colour Index, Volume 5, Revised 1975, with a request to supply a small sample of their versions of C.I. Pigment Red 1. The names of the manufacturers who replied and the commercial names of their products are listed in Tables 1 and 2. Table 1 gives those who st i l l manufacture, Table 2 gives those who have discontinued manufacture but who supplied a sample for this investigation and Table 3 gives those who have discontinued manufacture and have no samples available.

TABLE 2

Companies No Longer Manufacturing C.I. Pigment Red 1, but which Supplied a Sample for this Investigation

Code Manufacturer

CFB Cappelle Frsres

CGY James Anderson Co.

ICI(A) Imperial Chemical Industries of

Pol CIECH SCW Sanyo Colour Works

(now Gebroeders Cappelle NV)

(now Ciba-Geigy)

Australia and New Zealand

Commercial Name

Para Red B3843 Para Red G5105 Jamander Red BS

Monolite Red BA

Pigment Red B Sanyo Signal Red

TABLE 3

Companies No Longer Manufacturing C.I. Pigment Red 1, and Had No Samples Available

Code Manufacturer Commercial Name

ACY

AMS

CKC DUP KKK MVC RCL RV

SCC

Silo Spcm

American Cyanamid Co.

Ridgeway Color & Chemical Division

Crompton & Knowles Corp. E I du Pont de Nemours & Co. Inc. Kaseihin Kogyo Kyokai Manuel Vilaseca y Cia Resinous Chemicals Reeves & Sons Ltd

SCC Colours Ltd (now Blythe Burrell Silo \

I

Ltd

Colours Ltd)

Soci6t6 de Produits Chimiques e t Matieres Colorantes de Mulhouse

Duplex Para Red XD20- 2900 Para Red B B20-2080 Y Para Toner B Para Red Para Red Dark Para Toner Tertropigment Red PAB Para Red Dark Dainichi Para Red Toner Lacal Red GN Recolite Para Red B,G Para Red Toner Para Toner Conc Para Red BS, TS Kromon Para Red BS, YS Siloton Red B,G Lake Red PN, 2R

JSDC Volume 98 December 1982 437

PREVIOUS WORK Singlecrystal X-ray diffraction techniques have shown the existence of three polymorphs: a, 0 and y. Crystals of the a form were obtained by cooling a hot saturated solution of the pigment in pyridine 121. The crystal structure was determined but no X-ray powder diffraction data were reported; attempts by this author t o reproduce that work have failed. Finally, however, a powder pattern for this polymorph was calculated from the singlecrystal data [21 using the program Lazy Pulverix [31. The pattern (Table 4) was calculated for cobalt X-ray radiation (CoK, = 1.79020 A), assuming that lines closer than 0.25' would overlap and their intensities would add. The calculation was completed twice, once assuming the Debye-Waller temperature factors from the original article and the other assuming zero for these factors.

TABLE 4

X-Ray Powder Diffraction Patterns of C.I. Pigment Red 1

Pattern (a) Pattern (b) Pattern (c)

d I n l o d I d I

12.229 23 7.199 19 6.906 17 6.204 100 6.115 8 5.396 65 4.661 21 4.076 10 3.755 22 3.561 12 3.435 76 3.325 77 3.235 48 3.105 6 2.992 15 2.934 3 2.899 <3 2.763 <3 2.698 <3 2.598 6 2.485 8 2.388 6 2.355 3 2.125 <3 2.096 3 1.990 4 1.961 <3 1.924 3 1.892 <3 1.820 <3 1.799 <3 1.789 <3 1.756 4 1.716 <3 1.626 3 5

22 18 16

100 8

65 23 12 24 14 89 92 57 7

19 4 3 3 3 8

12 8 5 3 6 8 3 5 4 3 3 5

10 4 7

12.24 7.20 6.89 6.20

5.39 4.65 4.06 3.75 3.55 3.436 3.328 3.235 3.106 2.991

2.901 2.762 2.702 2.594 2.498 2.393 2.350 2.124 2.088 1.987 1.959 1.926 1.882 1.825

1.786 1.753 1.715 1.624

29 13.35 26 10.45 25 8.63

100 7.00

65 6-441 6.21 37 5.54 14 5.41 27 4.68 13 4.42 83 4.05 85 3.72 55 3.64

5 3.436 18 3.325

3.237 <3 2.822

6 2.493 6 2.203 7 2.106

11 2.000 9 6 5

12 11 9 7

10 3

6 8 5

100 19 10 11

40 *

16 23 c3 14 17 41 29 41 40 40

4 3 8

<3 6

*Broad diffuse band (a) Calculated from the singlecrystal results for the (Yform, the

intensities calculated using the single-crystal temperature factors ( ITF) and also for zero temperature factors U0 ) (Intensities less than 3% of the maximum were ignored)

(b) Observed from A4329 CP Para Toner X Light (IMP) (cl Observed from Jamander Red BS (CGYI

Crystals of the 0 form were obtained by cooling a hot saturated solution of the pigment in toluene [41; both the X-ray powder data [41 and the crystal-structure analysis [51 have been reported.

Crystals of the y form were obtained by cooling a hot saturated solution of the pigment in chlorobenzene [61 ; again both the X-ray powder data 161 and the crystal struc- ture analysis 171 have been reported. Subsequently it has been learnt that this form may also be obtained by crystalliz- ing from pyridine [81.

Another crystallization of C.I. Pigment Red 1 has been reported 191, this time from benzene. No X-ray data were given but the morphology and extinction directions suggest that this was also they form.

EXPER I MENTA L X-ray powder patterns of al l products given in Tables 1 and 2 were obtained using an 11.46 cm diameter Debye-Scherrer camera and filtered copper (CuK, = 1.54178 A) and filter- ed cobalt (CoK, = 1.79020 & radiation, although only patterns taken with the latter radiation were measured accurately .

In addition to using these patterns t o identify various polymorphs and possible impurities, an attempt was made to judge the relative crystallinity and/or crystal size. Both these are related to the sharpness of the diffraction lines; the number of lines recorded and the resolution of close doublets were used as an indication. No measurements were made of the diffraction-line profiles and hence this judgement was subjective.

RESULTS Almost al l the X-ray powder patterns, except Sanyo Signal Red (SCW), exhibited a triplet of diffraction lines correspond- ing to interplanar spacings of approximately 3.42, 3.32 and 3.22 A. Comparison of the patterns showed that they were not all identical and could be divided into two major groups. In one all three lines were of approximately equal intensity, with an additional very strong line (the strongest of the pattern) at approximately 6.20 A; in the second group the central line was considerably stronger than the other two, which were of approximately equal intensity.

There were eight patterns in the first group and seven in the second; in addition two patterns, those from Jamander Red BS (CGY) and Sanyo Signal Red (SCW), did not f it into either group, both were different t o each other. The pattern from Jamander Red BS (CGY) also had the triplet of diffrac- tion lines of equal intensity, but with the strongest line at 13.4 A.

The predominant pattern from the first group agreed with

TABLE 5

Manufacturers' Samples Mainly Composed of 01 Form ~ ~~ ~

Code Commercial Name Interpretation of Pattern

CF B

HC

HOR IMP

KON NSK Po I h/o

a form +trace of unknown impurity

(Y form +sodium chloride +trace of unknown impurity

a form only detected a form only detected

a form only detected (Y form only detected a form +sodium chloride a form only detected

Para Red G5105

Para Red BS76

Paranitraniline Red 8559 A4329 CP Para Toner X Light Para Red Toner A491 1 Unknown Pigment Red B Para Red Toner RPT-52

438 J SDC Volume 98 December 1982

that calculated from the a form. Table 5 gives the manufac- turers' codes, proprietary names and interpretation of the patterns from the eight compounds in this group. Not all the specimens gave identical patterns; two, Pigment Red BS (Pol) and Para Red BS76 (HC), contained sodium chloride with, in the la t te r case, a trace of an unknown impurity. Para Red G5105 (CFB) also contained a trace of an unknown, although different, impurity .

It is known that some manufacturers add compounds to the pigment to modify thecharacteristics. Thus the 'unknown impurities' in the samples may be additions and not impuri- t ies in the normal sense of the word.

Another point that must be remembered is that it is not known to what extent these patterns are reproducible in other batches. In one case, Monolite Red BA (ICI) (see below), impurities were not detected in X-ray powder patterns from another batch.

A subjective assessment of crystallinity/crystaI size indica- ted that Para Red BS76 (HC) was the most crystalline follow- ed by four very similar products: A4329 CP Para Toner X Light (IMP), Para Red Toner A4911 (KON), Para Red Toner RPT-52 (PyO) and Para Red G5105 (CFB). The crystallinity/ crystal size appeared to be slightly less for Paranitraniline 8559 (HOR) while it was least for Pigment Red B (Pol) and the sample of unknown name from Sumitomo Chemical Co. Ltd (NSK).

The pattern from A4329 CP Para Toner X Light (IMP) is given in Table 4 as a comparison with the calculated pattern. Two sets of intensities were calculated for the theoretical pattern, the first assuming the temperature factors given in the original paper [21 and the second assuming zero tempera- ture factors. The pattern obtained by experiment tends to agree better with the latter than with the former, suggesting that the crystallinity in this powder was better than that in the single crystal.

Comparison of the patterns of the second group with those already known indicated that the major phase in these was the y form. Table 6 gives the manufacturers' codes, proprietary names and interpretations of the patterns from the seven samples in this group. Five of the compounds contained at least one other phase in addition to the y form. In one case, Para Red B3843 (CFB), this was deliberate as there was a shading component present at the coupling stage (private communication). However, two of the compounds, Para Toner B (FNC) and Toner Red M (GS), contained

TABLE 6

Manufacturers' Samples Composed of y Form

CFB FNC GS HOR

HOR

ICI (A)

IMP

Commercial Name Interpretation of Pattern

Para Red B3843 y form +another phase Para Toner B y form +sodium chloride Toner Red M y form +sodium chloride Paranitraniline y form +trace unknown Red N-41 impurity Paranitran iline y form only detected Red 20575 Monolite Red BA y form +minor unknown

A1 757 CP Para y form only detected Toner Deep

impurity (a form?)

sodium chloride, while two other samples contained uniden- tified impurities. In both these cases there was an insufficient number of diffraction lines unaccounted for by the y phase to identify the impurity positively, but in the case of Monolite Red BA (ICI) t h e impurity could be the a! phase.

Again the reproducibility of these patterns from batch to batch is unknown and no impurities were detected in a second batch of Monolite Red BA (ICI).

A subjective assessment of the crystallinity/crystal size indicated that A1757 CP Para Toner Deep (IMP) and Mono- l i te Red BA (ICI) were the most crystalline, Para Red 83843 (CFB) slightly less so; Para Toner B (FNC), Paranitraniline Red N41 (HOR) and Paranitraniline Red 20575 (HOR) were again less crystalline but similar t o each other; while Toner Red M (GS) had the poorest crystallinity.

The sample of Jamander Red BS (CGY) gave a unique pattern, which could not be interpreted as being that due to a, /I or y form, either individually or in combination. Presum- ably this pattern must be due to another form, 6; again the pattern is given in Table 4. The crystallinity of this sample is poor.

Sanyo Signal Red (SCW) gave a different pattern. In spite of a warning that this sample contained 20% of a precipi- tated inorganic salt, the pattern could not be interpreted in terms of those of the other forms of C.I. Pigment Red 1, nor was the inorganic sal t identified.

CONCLUSIONS In addition to the three polymorphs of C.I. Pigment Red 1 isolated as single crystals, it would appear that a t least one more polymorph, 6, exists, although it has been found only once.

Most commercial samples consist of either the 01 or y form, although some manufacturers deliberately add a second phase. Some of the samplescontain impurities; these are often, but not always, sodium chloride. It is not known whether the impurities are deliberately added, or how reproducible is the quality control of the various batches.

ACKNOWLEDGEMENTS The author would like to acknowledge the assistance given him by all the manufacturers listed in Table 1-3, without whose help this work could not have been completed. A reprint of this article will be sent to the individuals (too numerous t o mention) who were responsible for sending manufacturers' samples.

He would also like to thank Dr Andrew Quick of the University of London Computer Centre for obtaining and testing the program Lazy Pulverix so that it could be used in the present work.

REFERENCES 1. Whitaker, 'The Analytical Chemistry of Synthetic Dyes'

(Ed. Venkataraman), (New York: Wiley Interscience, (1 977) 269.

2. Grainger and McConnell, Acta Cryst., B25 (1969) 1962. 3. Yvon, Jeitschko and Parthe, J. Appl. Cryst., 10 (1977) 73. 4. Whitaker, J. Appl. Cryst., 12 (1979) 626. 5. Whitaker, Z. Kristallogr., 152 (1980) 227. 6. Whitaker, J. Appl. Cryst., 13 (1980) 458. 7. Whitaker, Z. Kristallogr., 156 (1981) 125. 8. Grainger. Private communication. 9. Hannam and Patterson, J.S.D.C., 79 (1 963) 192.

JSDC Volume 98 December 1982 439