GB2511110A

GB2511110A - Pigments

Info

Publication number: GB2511110A
Application number: GB1303262.8A
Authority: GB
Inventors: Yogesh Sandbhor; Manisha Deshpande; Racheria Satyanarayan; Rajendra Chitale; Balasaheb Diwate
Original assignee: SUDARSHAN CHEMICAL IND Ltd
Current assignee: SUDARSHAN CHEMICAL IND Ltd
Priority date: 2013-02-25
Filing date: 2013-02-25
Publication date: 2014-08-27
Also published as: GB201303262D0

Abstract

A process for the preparation of quinacridone (I) comprises: (a) reacting a 2,5-dianilinoterephthalic acid derivative (II) in the presence of a polyphosphoric acid; (b) adding sulphuric acid in an amount of up to and including 0.5 weight% based on the weight of (II); (c) drowning the reaction mixture of (b) in water and recovering the resulting quinacridone pigment; and (d) recrystallizing the quinacridone obtained in step (c) in an aqueous organic solvent at an elevated temperature and elevated pressure. R3 - R12 are hydrogen or C1- to C10-alkyl with the proviso that at least one of R8 and R12 is hydrogen and at least one of R3 and R7 is hydrogen; R1 and R2 are hydrogen or C1 to C10 alkyl. The method may provide quinacridone pigments that are highly transparent and yellower in shade than prior art methods.

Description

Pigments

Field of the Invention

The present invention relates to a process for the preparation of transparent quinacridone pigments.

Background of the Invention

Quinacridones are a family of synthetic pigments used to make high performance paints. Quinacridone pigments have an exceptional colour strength and weather fastness. In automotive and architectural industry, quinacridone pigments) preferably in the I-and y-phase, are of particular interest as these pigments produce a deep bluish to yellowish red metallic finish.

It is desirable that the quinacridone pigment is highly transparent for these applications. In the past, the desired transparency grades have been achieved to a certain level by wet milling and acid pasting. In recent years, various quinacridone derivatives such as suipho derivatives, suiphonamido derivatives or phthalimidomethyl derivatives have been found to control and direct the crystal growth in such a way that desired transparency levels can be achieved.

These quinacridone derivatives may be added at any stage during the synthesis of the quinacridone pigments, i.e during the cyclisation, oxidation or final conditioning for the desired purpose. The derivatives may also be synthesised in situ during the manufacture in order to simplify the process with consistent pigment qualities.

US 6,284,890 discloses a process for production of quinacridone pigments wherein substituted and/or unsubstituted 2,5-diarylamino-6,13-dihydroterephthalic acid and polyphosphoric acid are reacted to form a quinacridone melt which is treated with 1 to 30 wt.% of concentrated sulphuric acid. The resulting reaction mixture is then drowned in a liquid in which the quinacridone is substantially insoluble.

However, employing a considerable concentration of sulphuric acids leads to the formation of water-soluble sulphonated quinacridones and thus to a considerable loss in yield.

US 6,241,814 discloses the preparation of a quinacridone pigment by cyclizing dianilinoterephthalic acid with polyphosphoric acid. The reaction mixture is then drowned in an amount of water or orthophosphoric acid which is such that the final orthophosphoric acid concentration is greater than or equa' to 50% by weight in the hydrolysis mixture.

The production processes disdosed in both these US patents generate a large amount of acidic effluent. The effluent of the process according to US 6,284,890 is an aqueous mixture of phosphoric and sulphuric acid whereas in case of the process described in US 6,241,814 a large amount of an aqueous phosphoric acid is obtained which has to be disposed of Both processes, furthermore, yield pigments exhibiting a bluish shade of red which may be undesirable for certain applications where a more yellowish shade is required.

The inventors have, following extensive experimentation, identified an alternative process for making a quinacridone pigment.

Summary of the Invention

Surprisingly it has been found that a process for the preparation of a quinacridone of formula (I) R2 [I) wherein Ri and Rz are identical or different and each is independently of the other hydrogen or Ci to Ciu alkyl, comprising (a) reacting a 2,5-dianilinoterephthalic acid derivative of formula (II) (II) wherein R3 to Ru are identical or different and each is independently of the other hydrogen or Ci-to C io-alkyl with the proviso that at least one of RH and Riz is hydrogen and at least one of R3 and R7 is hydrogen, with a polyphosphoric acid, (b) adding sulphuric acid in an amount of up to and including 0.5 weight% based on the weight of the 2,5-dianilinoterephthalic acid derivative of formula (II), (c) drowning the reaction mixture of (b) in water and recovering the resulting quinacridone pigment) and (d) recrystallizing the quinacridone obtained in process step (c) in an aqueous organic solvent at an elevated temperature and an elevated pressure yields quinacridone pigments which are highly transparent and yellower in shade than the pigments known from the prior art Furthermore, after isolation of the quinacridone pigment the filtrate on'y comprises a diluted aqueous phosphoric acid solution as opposed to a mixture of phosphoric and sulphuric acid as in US 6,284,890 or a 50% by weight solution of phosphoric acid as in US 6,241,814.

2,5-dianilinoterephthalic acid derivatives may therefore be converted by the process according to the present invention into quinacridone pigments that exhibit a high transparency and excellent colour strength.

2,5-dianilinoterphthalic acid derivatives which undergo cyclisation in accordance with the present invention are preferably the ones according to formula [II] (II] wherein R3 to Ru are identical or different and each is independently of the other hydrogen or Ci-to C io-alkyl with the proviso that at least one of RH and Riz is hydrogen and at least one of R3 and R7 is hydrogen.

In a preferred embodiment, a 2,5-dianilinoterephthalic acid derivative of formula (II] is used in which R5 and R10 are methyl and R3, R4, R6 to R9, R11 and R12 are hydrogen.

In another preferred embodiment, a 2,5-dianilionoterephthalic acid derivative of formula (II) is used in which P3 to Rn are hydrogen.

As ring-closing or dehydrating agent polyphosphoric acid is used in the cyclisation step (a]. In a preferred embodiment the polyphosphoric acid provides an equivalent of 115 to 119 % of orthophosphoric acid. Polyphosphoric acid can be produced by adding phosphorous pentoxide to an aqueous solution of ortho phosphoric acid.

Preferably the polyphosphoric acid is prepared immediate'y before the cyclisation reaction as the polyphosphoric acid may absorb moisture upon storage and become too diluted to effect ring closure.

In embodiment the polyphosphoric acid is used in a weight ratio with regard to the 2,5-dianilinoterephthalic acid derivative of formula (II) of from and induding 2.9:1

S

to including 5:1 and preferably in a weight ratio of from and including 3:1 to and including 4:1.

In the sulphonation step (b) sulphuric acid in an amount of up to and including 0.5 % by weight based on the amount of 2,5-dianilinoterephthalic acid derivative of formula (II) is added to the cyclisation reaction mixture. Concentrated sulphuric acid which is generally understood to have a concentration of 98% of sulphuric acid.

is preferably used. The use of sulphuric acid of a lower concentration may affect the actual colour shade of the final pigment.

Preferably, from 0.15 to 0.5 weight % of sulphuric acid based on the amount of the 2,5-dianilinoterephthalic acid derivative of formuLa (II] are added to the cyclisation reaction mixture. After addition of the sulphuric acid the reaction mixture is stirred at a temperature of 110 to 130°C, preferably at 120 to 122°C, and for a time of 1 to 40 minutes, preferably for 30 minutes.

After the sulphonation process step (b) the reaction mixture is drowned in water.

Drowning generally involves vigorous agitation. During the drowning step (c) water is used in a quantity of from 500 to 3000 weight%, preferably of from 1000 to 2250 weight% based on the weight of the 2,5-dianilinoterephthalic acid derivative of formula (II).

The sulphuric acid treated reaction mixture is drowned in water while the temperature of the resuking mixture is kept between 0 and 80 °C, preferalMy between 0 and 30°C and most preferably between 0 and 20°C. Drowning of the reaction mixture while maintaining a lower temperature leads to an improved chroma (higher C* volue), more yellowish shade (higher Db) and higher colour strength.

The crude pigment that is obtained after the drowning step (c) is in the unstable alpha form which is furthermore unsuitable for direct use as a pigment and must be subjected to further processing. In process step (d) the pigment obtained from the drowning step (c) is recrystallized in an aqueous organic solvent at an elevated temperature and elevated pressure to obtain a pigment in the desired gamma form.

Elevated temperature means a temperature that is above 25°C) preferably a temperature that is in the range of from 100°C to 140°C. Elevated pressure means a pressure of from 1.5 to 4.0 kg/cm2) preferably of from 3.0 to 3.5 kg/m2.

As organic solvents alcohols with 1 to 4 carbon atoms may be used. In a preferred embodiment methanol, ethanol, propanol, isopropanol, butanol, isobutanol or mixtures thereof are used. In an especially preferred embodiment methanol is used.

In another especially preferred embodiment isobutanol is used.

The slurry of the crude pigment and the aqueous organic solvent is adjusted to a pH of equal to or above 11 with sodium hydroxide. Sodium hydroxide can be used as pellets or as aqueous solution. Under alkaline conditions Ostwald ripening occurs which is responsible for crystal growth and crystal transformation from alpha to gamma form.

Examples

Exam vie 1 (comparative example -without usin a sulphur/c acid): Preparation ofpolyphosphoric acid: Polyphosphoric acid was prepared by adding 102.9 g phosphorous pentoxide to 57.1 g of 85% aqueous ortho phosphoric acid under stirring. The temperature rose to 180°C. Stirring was continued until a clear and homogeneous solution was obtained. The phosphoric acid equivalent of the resulting solution was 119%. The solution was then cooled to 100°C.

Cyclysation reaction: g of 2,5-dianilinoterephthalic acid was introduced under stirring to the above polyphosphoric acid solution at 100°C. The resulting reactions mixture was stirred at 120°C for 3 hours.

Drowning: The hot reaction mixture was then poured in a continuous stream into 900 g cold water at 15 ± 2°C keeping the temperature below 20°C. The slurry thus obtained was stirred for 30 mm and filtered. The pigment thus obtained was washed with cold water till neutral to get the press cake.

Solvent treatment: The press cake was immersed in 120 g water and stirred to prepare a slurry. The pH was adjusted to above 11 with caustic lye. 225g methanol were then added to the slurry and the mixture was transferred to an autoclave. Under stirring the slurry was heated to 120°C, resulting in a pressure rise to 3.2 kg/cm2. The mixture was stirred under these conditions for 6 hours. The slurry was then cooled to 40°C, filtered and washed with water until neutral. The wet cake was dried at 80°C, and pulverised to obtain the final pigment A significantly opaque pigment was yielded.

Exam vie 2 (Comparative exam vie as per Example I of US 6284890): Cyclisation reaction: g of 2,5-dianilinoterephthalic acid was introduced under stirring at 80°C to 90°C into 400 g of polyphosphoric acid, containing 115 to 119% P205, and the mixture was heated at 125°C for 1 hour.

Sulfonation process: 1 g of concentrated su'phuric acid (98%] was added to the reaction mixture and the resulting slurry was heated at 125°C for 30 mm.

Drowning: The reaction mixture was then drowned into 1000 g water at 60°C under vigorous agitation while the temperature rose to 80°C. The mixture was stirred at 60°C to 80°C for 30 mm to one hour and the crude pigment was then filtered off and washed until neutral.

It was observed that the filtrate was highly red in colour indicating a significant loss of pigment during the washing step. The pigment was obtained in the unstable a form which furthermore does not possess the required colour and transparency properties.

To improve the pigment properties, the crude pigment was solvent treated to yield they form.

Solvent treatment: The solvent treatment was carried out as described in Example 1.

Example 3 faccording to this invention): Preparation of polvphosphoric acid Polyphosphoric acid was prepared as in example 1.

Cyclisation reaction g of 2,5-dianilinoterephthalic acid was added under stirring to a polyphosphoric acid solution [prepared according to Example 1) at 100°C. The mixture was stirred at 120°C for 3 hours.

Sulfonation process 0.15 g of concentrated sulphuric acid (98%), corresponding to 0.37% w/w of sulphuric acid based on 2,5-dianilinoterephthalic acid) was added to the reaction mass at the end of 3 hours and stirring was continued for additional 15 mm.

Drowning The hot reaction mass was then poured in a continuous stream into 900 g cold water at 15 ± 2°C maintaining the temperature below 20°C. The slurry thus obtained was stirred for 30 mm and filtered. The pigment thus obtained was washed with cold water until neutral to obtain a press cake.

Example 4 (comparative example according to US 6284890 using 30% of sulphuric acid): Example 2 was repeated except that the quantity of 98% sulphuric acid used was 30% w/w based on 2)5-dianilinoterephthalic acid. After addition of the total amount of sulphuric acid, the reaction mass became extremely viscous and sticky. Stirring became impossible, thus) the reaction mass was discarded.

Examole 5 (according to the invention): Preparation of polyphosphoric acid Polyphosphoric acid was prepared as described in Example 1.

Cyclisation reaction g of 2,5-dianilinoterephthalic acid was introduced under stirring to the polyphosphoric acid solution at 100°C stirred at 120°C for 3 hours.

Sulphonation process 0.075 g of concentrated sulphuric acid (98%), corresponding to 0.19% w/w based on 2,S-dianilinoterephthalic acid, was introduced into the reaction mass at the end of the 3 hours and stirring was continued for a further 15 mm.

Drowning The hot reaction mass was then poured into 900 g cold water at 15 ± 2°C maintaining the temperature below 20°C. The resulting slurry was stirred for 30 mins and filtered. The pigment thus obtained was washed with cold water until neutral to obtain a press cake.

Solvent treatment: The solvent treatment was carried out as in example 1. This pigment was found to be highly transparent, strong and significantly yellowish red.

Exam vie 6 rinventive method): Example 3 was repeated with the quantity of water used during the drowning step being reduced to 400 g instead of 900g.

Example 7 (inventive method): Example S was repeated with the quantity of water used for the drowning step being reduced to 400 g instead of 900g.

Example 8 (inventive method): Example 6 was repeated with the drowning temperature being 60-80°C. This pigment was found to be highly transparent, strong and significantly yellowish red.

Exam vie 9 (inventive method): Example 7 was repeated with the only difference that the drowning step was carried out at a temperature of 60 to 80°C.

Example 10 (identical to Example 1, however, less water used for drowninifl: Preparation of polyphosphoric acid Polyphosphoric acid was prepared according to Example 1.

Cyclisation reaction g of 2,S-dianilinoterephthalic acid was added under stirring to the above polyphosphoric acid solution at 100°C. The resulting reaction mixture was stirred at 120°C for 3 hours.

Drowning: The hot reaction mass was then poured in a continuous stream into 400 g cold water at 15 ± 2°C keeping the temperature below 20°C. The slurry thus obtained was stirred for 30 mm and filtered. The pigment thus obtained was washed with cold water until neutral to obtain a press cake.

Example 11 (without using sulphuric acidi: Preparation of polvphosphoric acid: Polyphosphoric acid was prepared by adding 82.2 g phosphorous pentoxide to 57.8 g of 85% aqueous ortho phosphoric acid under stirring. The temperature rose to 180°C. Stirring was continued until a clear and homogeneous solution was obtained.

The phosphoric acid equivalent of the resulting solution was 115%. The solution was then cooled to 100°C.

Cyclisation reaction: 40 g of 2,5-ditoluidinoterephthalic acid was introduced under stirring to the above polyphosphoric acid solution at 100°C. The resulting reaction mixture was stirred at 120°C for 3 hours.

Drowning: The hot reaction mass was then poured in a continuous stream into 750 g cold water at 23 ± 2°C keeping the temperature below 30°C. The slurry thus obtained was stirred for 30 mm and filtered. The pigment thus obtained was washed with cold water until neutral to obtain a press cake.

Solvent treatment: The press cake was immersed in 100 g water and stirred to prepare a slurry. The pH was adjusted to >11 with caustic lye. lBOg isobutanol were then added to the slurry and the mixture was transferred to an autoclave. Under stirring the slurry was heated to 130°C, resulting in a pressure rise to 3.0 kg/cm2. The mixture was stirred under these conditions for 6 hours. The slurry was then cooled to 40°C, filtered and washed with water until neutral. The wet cake was dried at 80°C, and pulverised to obtain the final pigment

Example 12:

Preparation of polvphosphoric acid: Polyphosphoric acid was prepared as in example 11.

Cyclisation reaction: 40 g of 2,S-ditoluidinoterephthalic acid was added under stirring to the above polyphosphoric acid solution at 100°C. The mixture was stirred at 120°C for 3 hours.

Sulfonation process: 0.18 g of concentrated sulphuric acid (98%], corresponding to 0.44% w/w of sulphuric acid based on 2,S-ditoluidinoterephthalic acid, was added to the reaction mass at the end of 3 hours and stirring was continued for an additional 15 mm.

Drowning: The hot reaction mass was then poured in a continuous stream into 750 g cold water at 23 ± 2°C maintaining the temperature below 30°C. The slurry thus obtained was stirred for 30 mm and filtered. The pigment thus obtained was washed with cold water until neutral to obtain a press cake.

Solvent treatment: The solvent treatment was carried out as described in Example 11.

Example 13

g of pigment obtained after the solvent treatment from Examples 1 to 3 and 5 to 12, 5 g of DISPERBYK-166 additive (solution of a high molecular weight block copolymer with pigment affinic groups], 42.5 g of Worlee SM400 (short oil alkyd resin (60 wt% solids], 52.5 g thinner (xylene: butanol 3:1, v/v] and 160 g glass beads (1.2-1.5 mm] were dispersed together using a Irsha Vibroshaker RPM 720 for two hours.

After two hours, the dispersion was analysed on a Flegman gauge in accordance with ISO 1524. If the dispersion was found to be less than 10 p. the mixture was dispersed for additional 15 mm. 50.0 g of Worlee SM400 (60 wt% solids] was then added and 40.0 g of melamine-formaldehyde hardener (Synpol MF-268, butylated melamine formaldehyde resin, (60 wt% solids] and the mixture was dispersed for mi Finally, the mixture was filtered in a clean glass beaker through a nylon cloth to separate the glass beads.

The paint thus obtained was applied on a varnish coated opacity card using K Coater (lOORm) applicator. The coated cards were kept at ambient temperature (25-30°C) for 10 mm for flash-off and then baked in an oven at 120°C for 20 mm.

The colouristic values were measured on a spectrophotometer (X-Rite Colour i7) according to Iso 7724-1, 150 7724-2 and ISO 7724-3. The following Table 1 summarises the C* values and Db values for the samples obtained in all the examples above. The samples obtained from the pigment of Example 1 was used as standard for the measurement of the Db values for the samples obtained with the pigments of Examples 2, 3 and 4 to 10, while the sample obtained from the pigment of Example 11 was used as standard for the measurement of the sample obtained from the pigment of Example 12.

Table 1: C* and Db values for pigments obtained in Examples ito 3 and S to 12.

Db values

Example C* Value

Full Tone 1 46.85 -- 2 44.19 -2.09 3 52.67 4.49 52.17 3.88 6 53.18 5.02 7 50.6 2.82 8 47.9 1.72 9 50.29 2.67 41.15 -5.18 11 36.47 - 12 37.48 0.75 Note: Paint incorporating pigment obtained in Example I was used as standard for the measurement of Db values for Examples 2 to while the paint incorporating pigment obtained in Example 11 was used as standard

for Example 12.

Comparing the C* values corresponding to the chroma of the different pigments, it is obvious that the chroma increases with decreasing concentration of sulphuric acid used. The pigments of example 2 which correspond to the closest prior art exhibit the lowest C* value while example 9 with the lowest amount of sulphuric acid used during preparation exhibits the highest value for C*.

In addition, the amount of sulphuric acid not only influences the chroma of the pigments but also their colour shade. Whereas the pigments of Example 2 which were prepared according to a process of the prior art have a distinct shift towards a blue shade in comparison to the pigments produced without the use of sulphuric acid, all pigments prepared using an amount of concentrated sulphuric acid according to the invention exhibit a shift to more yellowish colour shades.

The temperature during drowning of the reaction mixture also appears to influence the chroma and colour shade of the resulting pigments. Independent of the amount of sulphuric acid used, a higher temperature (60°C to 80°) leads to a slightly decreased chroma and a bluer colour tone of the resulting pigments.

Example 14

75g TiOz [DuPont Ti-Pure R-902+], 40 g of Worlee SM 400 (short oil alkyd resin, 60 wt% solids), 15 g thinner (xylene: butanol 3:1, v/v) and 240 g glass beads (1.2-1.5 mm) were dispersed together in a Skandex shaker (Fast & Fluid Management model S0400. 620 rpm] for 30 mm.

After 30 mm, the dispersion was analysed on a Hegman gauge in accordance with Iso 1524. If the dispersion was found to be less than 10.t, the mixture was dispersed for an additional period of 15 mm. 64 g of short oil alkyd resin (Worlee SM400, 60 wt% solids), 92 g melamine-formaldehyde hardener (Synpol MF-268, butylated melamine formaldehyde resin] [60 wt% solids) and 14 g thinner [xylene: butanol 3:1, v/v) were then added and the mixture was dispersed for S mins.

Finally, the mixture was filtered through a nylon cloth to separate the glass beads from the paint to get a "25% white base".

g paint of the different samples obtained in Example 13 was mixed with 20 g of this "25% white base" with the help of a brush for uniform mixing. The paint thus obtained was applied on a varnish coated opacity card using a K coater (lOORm) applicator. The coated cards were kept at ambient temperature (25-30°C) for 10 mm to flash-off and then baked in an oven at 120°C for 20 mm.

The colouristic values were measured with the help of a spectrophotometer (X-Rite Colour i7) according to ISO 7742-1, ISO 7742-2 and ISO 7742-3. The following table 2 summarises the % strength of the paints comprising the pigments of examples 2-9 against the paint comprising the pigments of example 1. The term "strength" is calculated using the Kubelka & Munk equation.

Table 2: Colour strength of paints prepared with the pigments obtained from Examples ito 3 and 5 to 10 and 12.

Example % Strength 1 --

2 91.83 3 107.76 107.35 6 105.21 7 110.56 8 99.69 9 103.99 105.9 11 --12 100.9 Note: Paint prepared with the pigments of example 1 was used as standard for examples 2 to 10 wlule the paint prepared with the pigments of example 11 was used as standard for example 12.

Inline with the results regarding chroma and colour shade, the colour strength also increases with decreasing amounts of sulphuric acid used. The effect of the temperature during the drowning step is also reflected in the colour strength of the resulting pigment.

Claims

Claims: 1. A process for the preparation of a quinacridone of formula (1) wherein R1 and R2 are identical or different and each is independently of the other hydrogen, or C1 to C10 alkyl, comprising (a) reacting a 2,5-dianilinoterephthalic acid derivative of formula (II) RRl2NH 6 (TI) wherein R3 to Riz are identical or different and each is independently of the other hydrogen or Ci-to Cio-alkyl with the proviso that at least one of R8 and Riz is hydrogen and at least one of R3 and R7 is hydrogen, in the presence of a polyphosphoric acid, (b) adding sulphuric acid in an amount of up to and including 0.5 weight% based on the weight of the 2,5-dianilinoterephthalic acid derivative of formula (II), (c) drowning the reaction mixture of (b) in water and recovering the resuTting quinacridone pigment, and (d) recrystallizing the quinacridone obtained in process step (c) in an aqueous organic solvent at an elevated temperature and elevated pressure.
2. The process of claim 1 wherein the sulphuric acid is added in an amount of from 0.15 o 0.5 weight% based on the weight of the 2,5-dianilinoterephthalic acid derivative.
3. The process of any one of claims 1 to 2, wherein during the drowning step (c) the temperature of the reaction mixture is kept in the temperature range of from 0 to 80°C.
4. The process of any one of claims 1 to 2, wherein during the drowning step (c) the temperature of the reaction mixture is kept in the temperature range of from 0 to 3 0°C.
5. The process of any one of claims 1 to 4, wherein during the drowning step (c) water is used in a quantity of from 500 to 3000 weight% based on the weight of the 2,5-dianilinoterephthalic acid derivative of formula (II).
6. The process of any one of claims 1 to 4, wherein during the drowning step (c) water is used in a quantity of from 1000 to 2250 weight% based on the weight of the 2,S-dianilinoterephthalic acid derivative of formula [II).
7. The process of any one of claims ito 6, wherein the organic solvent of step (d) is selected from aliphatic alcohols with 1 to 4 carbon atoms.
8. The process of any one of claims 1 to 6, wherein the organic solvent is methanol orisobutanol.
9. The process of any one of claims 1 to 8, wherein in step (d] the p1-I of the reaction mixture is adjusted to a pH of equal to or above 11.
10. The process of any one of claims 1 to 9, wherein in the 2,S-dianilinoterephthalic acid derivative of formula (II) R3 to Riz are hydrogen.ti. The process of any one of claims 1 to 9, wherein in the 2,S-dianilinoterephthalic acid derivative of formula [II) Rs and Rio are methyl and R3, R4, R6 to R9, Rn and R12 are hydrogen.