CA1163403A - Composition containing a photo-activator for improved bleaching - Google Patents

Abstract

ABSTRACT

Bleach compostions comprising a weakly colouring to non-colouring porphine photo-activator and process for bleaching substrates or liquids using said porphine photo-activator are disclosed. The porphine photo-acti-vator used and as defined herein is selected such that the lowest energy allowed electronic transition of the photo-activator molecule gives rise to an absorption band (Q band) with maximum intensity at a wavelength greater than 700 nm.

Description

~ ~ ~3~03 C 594 (R) COMPOSITION CONTAINING A PHOTO-ACTIVATOR FOR
IMPROVED BLEACHING

This invention rela~es to compositions for bleaching and/or disinfecting of organic materials, and to pro-cesses for simultaneous removal of stains and fugitive dyes.

US Patent 3,927,967 relates to a washing and bleaching process utilizing photo-activating compounds, princi-pally sulphonated zinc phthalocyanine, in the presence of visible light and atmospheric oxygen. Japanese Patent Application OPI 50-113,479 teaches the use of specific mixtures of sulphonated zinc phthalocyanines as prefer-red bleach photo-activators~ In each of the foregoing references the detergent compositions utilizing sulpho-nated zinc phthalocyanine contained both organic surfac-tant and alkaline builder salt. US Patent No. 4,033,718 discloses the use of zinc phthalocyanine tri- and tetra-suphonates as bleach photo-activators in detergent com-posi~ions.

~ U5 Patents 2,951,797, 2,951,798, 2,951,799 and 2,951,800 describe certain porphines as catalysts for the photo-oxidation of olefins.

References to carboxylated porphines have appeared in US
Patent 2,706,199 ~nd C~R. Acad.Sci., Ser. C 1972, 275(11), 573-6 authored by Gaspard et al. See also Color Index No. 74320. References to aminosulphonyl porphines are West-German OLS 2,057,194, British Patent 613,781 and British Patent 876,691. See also Color Index No. 74350.
Other substituted porphines are discLosed in Austrian Patent 267,711, French Patent 1,267,094, US Patent

2,670,265 and British Patent 471,418.
`~

~ i 1 63403 c 594 (R) Porphine photo-activators are further disclosed in European Patent Applications 0.003149, 0.003371 and 0.003861.

Though porphine photo-activators could decolourize various stain chromophores, any such photo-bleaching benefit is generally accompanied by the risk of severe colouring (blueing or greening) of the substrate due to the "direct dye" nature of the porphine compounds. Hence, lQ although very efficient, the porphine compounds so far used as photo-activators, such as the metallated and un-metallated phthalocyanines and sulphonated phtalocyani-nes, are of limited photo-bleaching effectiveness because of the limited level that can be used. For example ~inc phthalocyanine tetrasulphonate and aluminium phthalo-~cyanine sulphonate are cellulose substantive materials and at levels above~ 0.5 mg/l (,v 0.01% on product) pro-duce unacceptable fabric blueing.

Inspection of the UV/visible absorption spectra of many porphine photo-activators, especially phthalocyanines, has shown that these materials have absorptions in the near ultra-violet and the red region separated by an extended transparent region. Thus it was investi~ated if the effectiveness of this apparently efficient photo-bleaching process could possibly be improved by shifting the visible absorption into the invisible infra-red regions and so produce a lightly coloured to colourless porphine molecule that could operate as efficiently as the coloured phorphines bu~ that could be used at higher, more effective levels.

The achievement of such a chromophoric shift by molecu-lar refinement requires a knowledge of the electronic transitions in the molecule responsible for both the visible and ultra-violet absorptions. A knowledge of the C 59~ (R) 34 ~ 3 nature of these transitions would allow variations of the energy associated with these transitions~by molecu-lar refinement. The photo-chemical behaviour of this class of compounds must be understood if the resulting molecular refinement is not ~o result in an unknown change to photo-chemical behaviour.

It has now been found that certain species of porphine photo-activators, of which the lowest energy allowed electronic transition gives rise to an absorption (Q
band) with maximum intensity at a wavelength greater than 700 nm, show a surprisingly effective photo-bleaching action in the presence of sunlight, natural or artificial lights having radiation wavelength 600 nm.
These photo-activators have the advantage that they form weakly coloured to colourless solutions, so that they can be used at more effective levels without the risk of directly dying the substrate.

Although often containing solubilizing substituents which render these photo-activators water-soluble, hy-drophobic application of these materials is also possi-ble without such substitution, e.g. for the bleaching of non-aqueous liquids.
Accordingly the invention provides a bleach composition comprising a weakly colouring to non-colouring porphine photo-activator having the general formula ~ fA )~
~ J~

1 63~3 C 594 (R~

where X is individually (=N-) or (=CY-), the total number of (=N-) groups being at least one; wherein Y is individually hydrogen or optionally substituted alkyl, cycloalXyl, aralkyl, aryl, alkaryl or heteroaryl; where each of Rl, R2, R3 and R4 is individually an op~ionally substituted ortho-arylene system forming to-gether with a pyrrole ring in the porphine core a con-den~ed nucleus; wherein M is 2 (H) atoms bound to dia-gonally opposite nitrogen atoms, or Zn(II), Ca(II), Mg ~II), Al(III) or Sn(IV); wherein Z is any necessary counterion for the ~olubilizing groups; wherein n is the number of solubilizing groups, wherein substituted into Y or any Rl, R2, R3 and R4 may be A, a solubilizing group 6elected from the group consisting of (a) catio-nic group~, where Z i8 an anion and n is from 0 to about10: (b) polyethoxylate nonionic groups -(CH2CH20)~H, where Z is ~ero, n i8 from 0 to about 10, and G = (ng) =
the number of (condensed ethylene oxide molecules per porphine molecule) i~ from 0 to about 7Q; (c) anionic group6 where Z is a cation and n is from 0 to about,10;
such that the lowe~t energy allowed electronic transi-tion of the photo-activator molecule gives rise to an absorption band (Q band) with maximum intensity at a wavel~ngth greater than 700 nm.
In another aspect of the invention a method i8 provided for bleaching substrates or liquids wherein a porphine photo-activator of the above formula and as defined above is used in the presence of ~unlight, natural or artificial lights having radiation wavelength~greater than 600 nm.

Preferably each of Rl, R2, R3 and R4 is individually an optionally substituted ortho-naphthalene system for-ming a condensed nucleus togeth~r with a pyrrole ring inthe porphine core. Preferably X iY (~

C ~4 ~K) -~ ~ 3 63~03 Normally an absoroption with maximum intensity at a wavelength of between 700 and 1200 nm will be suitable in the practice of this invention, but a preferred ab-sorption band maximum will be at a wavelength in the range of 700 to 900 nm.

Preferred cationic solubilizing groups are quaternary pyridinium and quaternary ammonium groups. Preferred anionic solubilizing groups are carboxylate, polyethoxy carboxylate, sulphate, polyethoxy sulphate, phosphate, polyethoxy phosphate, an sulphonate. Preferred nonionic solubilizing groups are polyethoxylates.

The solubilizing groups on a given porphine photo-acti-vator of this invention can be, but need not be, allalike; they can be different not only as to their pre-cise structure but also as to their electrical charge.
Thus cationic, anionic, and/or nonionic solubilizing groups can be present on an individual photo-activator molecule.

Preferably the composition of the instant invention con-tains a surfactant. The surfactant can be anionic, nonionic, cationic, semi-polar, ampholytic, cr zwitter-ionic in nature, or can be mixtures thereof. Surfactantscan be used at levels from about 10% to about 50~ of the composition by weight, preferably at levels from about 15~ to about 30~ by weight.

Preferred anionic non-soap surfactants are water-soluble saLts of alkyl benzene sulphonate, alkyl sulphate, alkyl polyetoxy ether sulphate, paraffin sulphonate, alpha-olefin sulphonate, alpha-sulfocarboxylates and their es-ters, alkyl glyceryl ether sulphonate, fatty acid mono-glyceride sulphates and sulphonates, alkyl phenol poly-ethoxy ether sulphate, 2-acyloxy~alkane-1-sulphonate, . . .

` . - 1 1 ~3~03 C 594 (R) and beta-alkyloxy alkane sulphonate. Soaps are also preferred anionic surfactants.

Especially preferred are alkyl benzene sulphonates with about ~ to about lS carbon atoms in a linear or branched alkyl chain, more especially about 11 to about 13 carbon atoms; alkyl suphates with about 8 to about 22 carbon atoms in the alkyl chain, more especially from abou~ 12 to about 18 carbon atoms, alkyl polyethoxy ether sulpha-tes with about 10 to about 18 carbon atoms in the alkyl chain and an average of about 1 to about 12 -CH2C~2O-groups per molecule, especially about 10 to about 16 carbon atoms in the alkyl chain and an average of about 1 to about 6 -CH2CH2O-groups per molecule; linear paraffin sulphonates with about 8 to about 24 carbon atoms, more especially from about 14 to about 18 carbon atoms; and alpha-olefin sulphonates with about 10 to about 24 carbon atoms, more especially about 14 to about 16 carbon atoms; and soaps having from 8 to 24, especi-ally 12 to 18 carbon atoms.

Water-solubility can be achieved by using alkali metal, ammonium, or alXanolamine cations; sodium is preferred.
Magnesium and calcium are preferred cations under cir-c~stances described by Belgian Patent 843,636. Mixtures of anionic surfactants may be contemplated; a preferred mixture contains alkyl benzene sulphonate ha~ing 11 to 13 carbon atoms in the alkyl group and an alkyl polyethoxy alcohol sulphate havins lO to 16 carbon atoms in the alkyl group and an average deg~ee of ethoxylation of 1 to 6.

Preferred nonionic surfactants are water-soluble com-pounds produced by the condensation of ethylene oxide with a hydrophobic compound such as an alcohol, alkyl phenol, polypropoxy glycol, or polypropoxy ethylene diamine.

i 1 63~03 C 594 (R~

Especially preferred polyethoxy alcohols are ~he con-densation product of-l to 30 moles ot ethylene oxide with 1 mol o~ branched or straight chain, primary or secondary aliphatic alcohol havin~ from about 8 to about 22 carbon atoms; more especially 1 to 6 moles of ethy-lene oxide condensed with 1 mol of s~raight or branched chain, primary or secondary aliphatic alcohol having from about 10 to about 16 carbon atomst certain species of polyethoxy alcohols are commercially available from the Shell Chemical Company under the trade-name "Neodol".

Preferred semi-polar surfactants are water-soluble amine oxides containing one alkyl moiety of from about 10 to 28 carbon atoms and 2 moieties selected from the group consis-ting of alkyl groups and hydroxyalkyl groups containing from 1 to about 3 carbon atoms, and especially alkyl di-methyl amine oxides wherein the alkyl group contains from about 11 to 16 carbon atoms, water-soluble phosphine oxide detergents containing one alkyl moiety of about 10 to about 28 carbon atoms and 2 moieties selected from the group consisting of alkyl groups and hydroxyalkyl groups con-taining from about 1 to 3 carbon atoms; and water-soluble sulphoxide dètergents containing one alkyl moiety of from about 10 to 28 carbon atoms and a moiety selected from the group consisting of alkyl and hydroxy~alkyl moieties of from 1 to 3 carbon atoms.

Preferred ampholytic surfactants are water-soluble deri-vatives of aliphatic secondary and tertiary amines in which the aliphatic moiety can be straight or branched and wherein one of the aliphatic substituents contains from about 8 to 18 carbon atoms and one contains an anionic water-solubilizing group, e.g. carboxy, sulpho-nate, sulphate, phosphate, or phosphonate.

~363~03 c5g~

Preferred zwitterionic surfactants are water-soluble derivatives of aliphatic quarternar~ ammonium, phospho-nium and sulphonium cationic compounds in which the ali-phatic moieties can be straight or branched, and wherein one of the aliphatic substituents contains ~rom about 8 to 18 carbon atoms and one contains an anionic water-solubilizing group, especially alkyl-dimethyl-propane-sulphonates and alkyl-dimethyl-ammonio-hydroxy-propane-sulphonates wherein the alkyl group in both types con-tains from about 1 to 18 carbon atoms.

A t~pical listing of the classes and species of surfac-tants useful in this invention appear in the books "Sur-face Active Agents", Vol. I, by Schwartz & Perry (Inter-science 1949) and "Surface Active Agents and Detergents", Vol. II by Schwartz, Perry and Berch (Interscience 1958), the disclosures of which are incorporated herein by re-ference. This listing, and the foregoing recitation of specific surfactant compounds and mixtures which can be used in the instant composi~ions, are representative but are not intended to be limiting.

The compositions of the present invention can be used for bleaching organic materials, for example fabrics and other taxtile materials, plastics material, staple, fibres, wood, paper, oils, fats and organic chemicals, and for the disinfection of for example swimming pools, sewage, etc.

Accordingly an essential component of the present inven-tion is a weakly colouring to non-colouring photo~acti-vator as described hereinbefoxe and further hereinbelow.
This component can also be described as a photo-chemical activator, or as a photo-sensitizer. The photo-activator of ~he invention is a porphine of the structure:

1 ~ 634~3 c 594 (R) ~ ~
~X~
R4 ~ R3 wherein X can be individually (=N-) or (=CY-), the total number of (=N-) groups being at least one; wherein Y can be individually hydrogen or optionally substituted alkyl, cycloalkyl, aralkyl, aryl, alkaryl or heteroaryl, where-in each of R1, R2, R3 and R4 can individually be an op-tionally substituted ortho-arylene system forming to-gether with a pyrrole ring in the porphine core a con~
densed nucleus; wherein M can be 2~H) atoms bound to diagonally opposite nitrogen atoms, or Zn(II), Ca(II), Mg(II), Al(III) or Sn(IV); wherein Z can be any necessa-ry counterion for the solubilizing groups; wherein n is the number of solubilizing groups: wherein substituted into Y or any of ~1~ R2, R3 and R4 may be A, a s~lubi-lizing group selected from the group consisting of (a) cationic groups, where Z is an anion and n is from O to about lO, (b~ polyethoxylate nonionic groups ~(CH2CH2O)gH~
where Z is zero, n is from O ~o about lO, and G = (ng) =
the number of (condensed ethylene oxide molecules per porphine molecule) is from O to about 70; (c) anionic groups where Z is a cation and n is from O about lO;
such that the lowest energy allowed electronic transi-tion of the photo-activator molecule gives rise to an absorption band (Q band) with maximum intensity at a wavelength greater than 700 nm.

J 63~03 Preferred photo-activators of the invention are those wherein each of Rl, R2, R3 and R4 is individually an optionally substituted ortho-naphthalene system forming a condensed nucleus together with a pyrrole ring of the porphine core. Preferably X is t-N-).

Normally an absorption with maximum intensity at a wave-length of between 700 and 1200 nm will be suitable in the practice of this invention, but a preferred absorption band maximum will be at a wavelength in the range of 700 to 900 nm.

The photo-activating compounds of the invention are sub-stantially non-toxic and can be unmetallated, M in the foregoing structural formula being comprised of two hydrogen atoms bonded to diagonally opposite inner ni-tro~en atoms of the ~yrrole groups in the molecule. Al-ternatively, the photo-activators can be metallated with zinc(lI), calcium(II), magnesium(II), aluminium(III), or tin(IV). Thus altogether, M can be 2(H) atoms bound to diagonally opposite N atoms or Zn(II), Ca(II), Mg(II), Al(III) or Sn(IV).

Solubilizing groups can be located anywhere on the por-phine molecule other than the porphine core as herein-before defined. Accordingly the solubilizing ~roups can be described as substituted into Y or R as hereinbefore defined.

Solubilizing groups can be anionic, nonionic, or cationic in nature. Preferred anionic solubilizing groups are carboxylate O O
- CO~;sulphate - O - S - ~,and O

~ 1 ~3~3 c 594 ~R) 11 , phosphate - O - P - ~. Ano~her preferred anionic so-OH
lubilizing group is S O
sulphonate - S - ~, o attached to a "remote" carbon atom as hereinafter defi-ned.
Other preferred anionic solubilizing a~ents are ethoxy-lated derivatives of the foregoing, especicially the polyethoxysulphate group -(CH2CH2O)nCOO- where n is an integer from 1 to about 20.
For anionic solubili7ing groups, Z the counterion is any cation that confers water-solubility to ~he porphine mo-lecule. A monovalent cation is preferred, especially ammonium, ethanolammonium, or alkali metal. Sodium is most preferred. For reasons described hereinafter the number of anionic solubilizing groups operable in the compositions of this invention is a function of the lo-cation of such groups or the porphine molecule. A solu~
bilizing group attached to a carbon atom of the photo-activator molecule displaced more than 5 atoms away fromthe porphine cores is sometimes herein referred to as "remote", and is to be distinguished from an attachment to a carbon atom displaced no more than 5 atoms from the porphine core, which is sometimes referred to herein as "proximate". For proximate solubilizing groups, the num-ber of such ~roups per molecule, n is from 0 to about 10, preferably from 3 to about 6, most preferably 3 or 4. For remote solubilizing groups, n is from ~ to abou~
8, preferably from 2 to about 6, most preferably 2 to 4.

' - 3 ~ 63403 c 594 (R) Preferxed nonionic solubilizing groups are polyethoxy-lates -tCH2CH20)nH. Defining n as the number of solubi-lizing groups per molecule, ~he number of condensed ethylene oxide molecules per porphine molecule is G =
ng-The water-soluble nonionic photo-activators of this in-vention have a value of G between about 8 and about 50, preferably from about 12 to about 40, most preferably from about 16 to about 30. Within that limitation the separate values of n and g are not critical.

For nonionic solubilizing groups, there is no counterion and accordingly Z is numerically e~ual to zeroO

Preferred cationic solubilizing groups are quaternary compounds, such as quaternary ammonium salts Rl R2 and qua~ernary pyridium salts ~ ~ - R, where all R's are alkyl or substituted alkyl groups.

For cationic solubilizing groups, M the counterion is any anion that coners water-solubility to the porphine molecule. ~ monovalent anion is preferred, espe~ially iodide, bromide, chloride or toluene sulphonate CH3 ~ 3 For reasons that are described hereinafter, the number of cationic solubilizing groups can be from O to about 10, preferably from about 2 to about 6, most preferably from 2 to 4.

~ 3~03 c 594 (R) Photo-activator usage in the composition of this inven-tion can be from about 0.001~ to about 2.0% by weight o~
the composition. Preferable usage is from about 0.005%
to about 0.1~ by weight of the composition. The weight ratio of photo-activator to surfactant, if present, can be between l/lQ000 and 1/20, preferably from 1/1000 to 1/100 .

Although it is not wished to be bound by theory, it is believed that the mechanism of bleaching using the in-stant photo-activators involves (1) absorption of dis-solved photo-activator on to substrates, e.g. abrics (2) excitation by light of the photo-activator in its groundstate to the excited singlet state, t3) intersys-tem crossing to the triplet state which is also excited but at a lower energy level than the singlet state and (4) interaction of the triplet species with the ground state of atmospheric oxygen to form the excited singlet state of oxygen and regenerate the photo-activator in its original ground state.

The excited singlet oxygen is believed to be the oxida~
tive species that is capable of reacting with stains to bleach them to a colourless and usually water~soluble state.

The mechanism above-described is predicated on solubili-ty of the photo-activator in the bath. Solubilization in aqueous media is accomplished by introducing solubilizing groups into the molecule.

However, some care must be taken, especially with anionic solubilizing groups, to ensure that there is no undesir-able aggregation of the photo-activator in solution, as then it wiIl become more colouring and/or photo-chemi-cally less active. This aggregation, probably dimerisa-tion, can be prevented through the presence of nonionic or cationic surfactants. It is therefore that the porphine photo-activators of this invention are especially useful in laundry baths, preferably in conjunction with cationic and/or nonionic substances. ~nasmuch as cotton surfaces are negatively charged, cationic substances have a strong af~inity for cotton fabrics and a strong tendency to adsorb or deposit thereon. In so doing they tend to bring down or co-adsorb other substance present in the laundry bath, such as the photo-activators of this invention.

The porphine photo-activators of this invention may con-tain in their molecular structure certain chemical groups which solubilize the photo-activator in an aqueous laun-dry bath. As detailed hereinafter these groups can con-tain a formal elec~rical charge, either positive or ne-gative, or can be electrically neutral overall, in which latter case they can contain partial charges of various degrees of strength. A photo-activator molecule can con-tain more than one solubilizing group, which can be allalike or can be different from one another in respect to electrical charge.

The co-adsorption phenomenon discussed above in relation to cationic substances assumes increasing importance in relation to photo-activators having, to some extent, an anionic or negative charge, whether a negative partial charge, a negative formal charge in an electrically neu-tral or even cationic molecule as a whole, or a multi-plicit~ of negative charges in an anionic photo-activa-tor molecule.

For anionic photo-activators having proximate solubili-zing groups, mono- and di- sulphonated photo-activator - 35 molecules are unsatisfactory for laundry use, and hence ~ ~ ~ 63~3 C 594 ~R) photo-activators of this invention for use in laundries have three or more proximate solubilizing groups per molecule. Compounds having more than about ten proxima*e solubilizing groups per molecule are often difficult to make and have no particular advantage. Hence photo-acti~
vators of this invention having proximate solubilizing groups for use in laundries have from three to about ten such groups per molecule; compounds having three to six proximate solubilizing groups per molecule are preferred, and compounds having 3 or 4 proximate solubilizing groups per molecule are especially preferred.

The foregoing discussion relates to anionic photo-acti-vators having proximate solubilizing groups. When the solubilizing groups are in remote locations, the tenden-cy of the photo-activator molecule to aggregate is re-duced because of both electrical and steric reasons, with the result that less dimerization occurs, less build up on the fabric occurs, and the solubilizing ef-fect of individual solubilizing groups is enhanced.Accordingly, a minimum of 2 remotely located anionic so-lubilizing groups per photo-activator molecule is satis-factory for laundry purposes, with 2 to about 6 being preferred and 3 or 4 being especially preferred.
Nonionic solubilizing groups have a low tendency to aggregate because there is no electrical charge-density effect and there is a particularly large steric effect reducing orderly association between photo-activator molecules. Because solubilization of polyethoxylated photo-activator molecules occurs primarily because of numerous ether groups in the polyethoxylate chains, it is of little consequence whether there is a single very long chain or a number of shorter chainsO Accordingly, the solubility requirement as hereinbefore expressed is in terms of the number of condensed ethylene oxide 0 3 ~
-' molecules per porphine molecule, which is from about 8 to about 50, preferably from about 12 to about 40, most preferably from about 16 to abou~ 30.

Photo-activators having cationic solubilizing groups do not effectively aggregate at all because the electron density in the ring is reduced. Direct substantivity on cotton fabrics is great. Only one solubili2ing group is enough to accomplish the purposes of ~he invention, al-though more are acceptable and indeed preferred. Accor-dingly the limiting numbers of solubilizing cationic groups are from O to about lO, preferably from about 2 to about 6, most preferably from 2 to 4.

lS As stated hereinabove, the macromolecular structure com-prising the porphine core contributes the essential photo-activation properties of porphine compounds. It follows inexorably that a large number of compounds ha-ving this macromolecular core, b~t with myriads of dif-ferent substituent groups, provided that the lowest energy allowed electronic transition of the photo-acti-vator gives riæe to an absorption band (Q band) with maximum intensity at a wavelength greater than 700 nm, are effective in the practice of this inven~ion. One versed in the art will recognize the impracticability of reducing to writing all possibilities that can be en-visaged by a skilful practitioner. The embodiments which follow are therefore to be considered exemplary but not exhaustive~

Weakly colouring to non-colouring photo-activators within the scope of this invention are for example:
i) tetra(sulpho-2,3-naphtho)tetraaza porphine zinc, tetrasodium salt:
ii) te~ra(sulpho-2,3 naphtho)tetraaza porphine aluminium, tetra(monoethanolamine) salt;

~ ~ ~3~0~ ~ ~Y4 ~K) iii) tri(sulpho-2,3-naphtho)mononaphtho-tetraaza porphine, calcium, trisodium salt;
iv) tetra(2,3-naphtho)tetraaza porphine, zinc;
v) tetra(4-N-ethylpyridyl-2,3-naphtho)tetraaza porphine, tetrachloride.

Each of the foregoing illustrative photo-activators is a specific chemical compound. Alternative photo-ac~ivators, each within the scope of the instant invention, are also those wherein substituted in each specific named compound are, inter alia:

a) instead of a specific cation listed: sodium, potassium, lithium, ammonium, monoethanol-amine, diethanolamine, or triethanolamine salts.
b) instead of a specific anion listed: chlori-de, bromide, iodide, or toluene sulphonate salts.
Z0 c) instead of the metallation listed: zinc(II), calcium(II), magnesium(II), aluminium(III), tin(IV), or metal free.
d) instead of the specific solubilizing group mentioned: carboxylate, polyethoxy carboxy-late, sulphate, polyethoxy sulphate, phos-phate, polyethoxy phosphate, sulphonate, quaternary pyridinium, ~uaternary ammonium, or polyethoxylate.
e) instead of the number of solubilizing groups mentioned: any number of solubilizing groups that is not greater than the number of pyrrole-substituted aromatic or pyrido groups plus the number of meso-substituted aroma~ic or heterocyclic groups and that is, for cationic or nonionic solubilizing groups, from 0 to 10; for remote anionic solubi-.

` ~ 1 6~4~3 c 59~ (R) lizing groups, from 2 to 10; and for non-remote solubilizing groups, from 3 to 10.

The alternative photo-activator compounds described above with Q band absorption maxima at wavelengt~s grea-ter than 700 nm are to be considered equally illustra-tive of the compounds of this invention as the compounds specifically named in the preceding list.

The literature contains references to numerous means of preparation of porphine and its derivatives, iOe. to the photo-activators of this invention. One skilled in the art of porphine chemistry will have no difficulty selec-ting a synthesis appropriate for his particular purpo-ses. Some of the synthesis reactions are accompanied byside reactions; in these cases conventional means of separation and purification are needed, such as chroma-tographic techniques, in a manner also detailed in the literature and well known to the skilled practitioner.
It may be said that there are two general preparative routes to make solubilized substituted porphines. The first route is to prepare the substituted porphine of choice and then solubilize it by introduction of appro-priate solubiliæing groups. This route is especiallyapplicable to the preparation of sulphonated porphines, and is illustrated hereinafter by the synthesis o di-verse individual sulphonated porphine species. The se-cond route is to prepare the solubiliæed porphine spe-cies of choice by using starting materials already containing the desired solubilizing groupts as part of their own constitution. This route is especially appli-cable to the preparation of porphines solubilized by groups other than sulphonate.

K/
~ ~ 63~3 . . .
Various principles for preparing porphine photo-acti-vators following these routes are described in European Patent Application No. 0003149, the disclosure of which is incorporated herein by reference.

It will be appreciated that one skilled in the chemical arts, and particularly in the colour and dye arts, can apply the foregoing principles to make his photo-acti-vator of choice according to this invention.
The foregoing description concerns compositions comprising a photo-activator and optionally a sur~actant. They are unbuilt compositions. As the photo-activators of this invention are useful in a great variety of otherwise conventional compositions, other optional components may be incorporated.

For instance, conventional alkaline detergent builders, inorganic or organic, can be used at levels up to about 80% by weight of the compositiont preferably from 10% to 60%, especially 20% to 40%. The weight ratio of surfac-tant to total builder in built compositions can be from 5:1 to 1:5, preferably from 2:1 to 1:2.

Examples of suitable inorganic alkaline detergency buil-der salts useful in this invention are water-soluble al-kali metal carbonates, borates, phosphates, polyphospha-tes, bicarbonates and silicates. Specific examples of such salts are sodium and potassium tetraborates, perbo-rates, bicarbonates, carbonates, triphosphates, pyrophos-phates, orthophosphates, and hexametaphosphates.

Examples of suitable organic alkaline detergency builder salts are: (1) water-soluble aminopolycarboxylates, e.g.
sodium and potassium ethylenediaminete~raacetates, ni trolotriacetates and N-(2-hydroxyethyl)-nitrilodiacetates;

; ~34~3 C 594 (R) (2) water-soluble salts of phytic acid, e.~. sodium and potassium phytates (see U.S.Pat,No. 2,739,942); (3) wa-ter-soluble polyphosphonates, including specifically, sodium, potassium and Lithium salts of ethane-l~hydroxy-l,l-diphosphonic acid; sodium, potassium and lithium salts of methylene diphosphonic acid; sodium, potassium and lithium salts of ethylene diphosphonic acid; and sodium, potassium and lithium salts of ethane-1~1,2-tri-phosphonic acid. Other examples include the alkali metal salts of ethane-2-carboxy-1,1-diphosphonic acid, hydro-xymethanediphosphonic acid, carboxyldiphosphonic acid, ethane-l-hydroxy-1,1,2-triphosphonic acid, ethane-2-hy-droxy-1,1,2-triphosphonic acid, propane-1,1,3,3,-tetra-phosphonic acid, and propane-1,1,2,3-tetraphosphonic acid; (4) water-soluble salts of polycarboxylate poly-mers and copolymers as described in U.S. Patent No.

3,308,067.

In addition, polycarboxylate builders can be used satis-factorily, including water-soluble salts of mellitic acid, citric acid, and carboxymethyloxysuccinic acid and salts of polymers of itaconic acid and maleic acid.

Certain zeolites or aluminosilicates enhance the function of the alkali metal pyrophosphate and add building capa-city in that the aluminosilicates sequester calcium hardness. One such aluminosilicate which is useful in ; the compositions of the invention is an amorphous water-insoluble hydrated compound of the formula Nax(sAl02.SiO2), wherein x is a number from 1.0 to 1.2 and y is 1, said amorphous material being further characterized by a Mg~+ exchange capacity of from about 50 mg eq. CaCO3/g. to about 150 mg eq. CaC03/g. and a particle diameter of from about 0.01 micron to about 5 microns. This ion exchange builder is more fully des-cribed in British Patent No. 1,470,250.

C 594 ~) 3 ~ ~ 3 A second watex-insoluble synthetic aluminosilicate ion exchange material useful herein is crystalline in na-ture and has the formula Naz~(Al02)z.(SiO~)]xH20, wherein z and y are integers of at least 6; the molar ration of z to y is in the range from l.Q to about 0.5, and x is an integer from about 15 to about 264; said aluminosilicate ion exchange material having a particle size diameter from about 0.1 micron to about 100 mi-crons; a calcium ion exchange capacity on an anhydrous basis of at least about 200 milligrams equivalent of CaCO3 hardness per gram; and a calcium ion exchange rate on an anhydrous basis of at least about 2 grains/gallon/
minute/gram. These synthetic aluminosilicates are more ully described in British Patent ~o. 1,429,143.
For nominally unbuilt compositions, it is contemplated that compositions can contain minor amounts, i.e. up to about 10%, of compounds that, while commonly classified as detergent builders, are used primarily for purposes other than reducing free hardness ions; for example electrolytes used to buffer pH, add ionic strength, con-trol viscosity, prevent gelling, etc.

It is to be understood that the bleach compositions of the present invention can contain other components com-monly used in detergent compositions. Soil suspending agents such as water-soluble salts of carboxymethylcel-lulose, carboxyhydroxymethylcellulose, copolymers of maleic anhydride and vinyl ethers, and polyethylene 30 glycols having a molecular weight of about 400 to 10,000 are common components of the detergent compositions of the present invention and can be used at levels of about 0.5% to about 10% by weight~ Dyes, pigments, optical brighteners, perfumes, enzymes, anti caking agents, suds control agents and ~illers can be added in varying ` amounts as desired.

` .

.

' 3 1 634~3 C 594 (R~

Peroxygen bleaches such as sodium perborate can optionally be used in the compositions of this invention. In con-junction therewith, conventional organic activators can be used to bleach more effectively at low temperatures, such as the anhydrides, esters and amides disclosed by Alan H. Gilbert in Detergent Aye, June 1967, pages 18 20, July 1967, pages 30-33, and August 1967, pages 26-27 and 67. It is generally believed that these activa-tors function by means of a chemical reaction of the activator with the peroxygen compound forming a peroxy acid.

Hence formulations are not precluded that contain com-ponents which bleach by two different mechanisms opera-ting independently.

The bleach compositions of the invention can be appliedfor bleaching substrates, e.g. fabrics; they are also effective photo-bleaches for dye stuffs in solution.
Hence the fabric bleach compositions of the invention have the additional advantage that they are also effective in reducing dye transfer in the wash.

Granular formulations embodying the compositions of the present invention may be formed by any of the conven-tional techniques, i.e. by slurrying the individual com-ponents in water and then atomizing and spray-drying the resultant mixture, or by pan or drum granulation of the components. A preferred method of spray-drying composi-tions in granule form is disclosed in U.S. Patents3,269,951 and 3,629,955 issued to Davis et al. on Decem-ber 28, 1971.

Liquid detergents embodying the photo~activating compo-sitions of the present invention can contain builders or can be unbuilt. If unbuilt, they can contain about 10 to i 1 63403 C 594 (R) about 50% surfactant, from 1 ~o about 15~ of an organic base such as mono-, di-, or tri-alkanolamine, and a so-lubiliztion system containing various mixtures of water, lower alcohols and glycols, and hydrotropes. Built liquid single-phase compositions can contain about 10 to about 25% surfactant, from about 10 to about 20% builder which can be inorganic or organic, about 3 to about 10~ hydro-trope, and water~ Built liquid compositions in multi-phase heterogeneous form can contain comparable amounts of surfactant and builder together with viscosity modi-fiers and stabilizers to maintain stable emulsions or suspensions.

The compositions of the present invention can also be prepared in the form of a laundry bar or can be impreg-nated into a water-insoluble substrate.

Detergent bleach formulations embodying the compositions of the present invention are commonly used in laundry practice at concentrations from about 0.1 to about 0.6 wt.~ in water. Within these approximate ranges are vari-ations in typical usage from household to household and from country to country, depending on washing conditions such as the ratio of fabric to water, degree of soiling of the fabrics, temperature and hardness of the water, method of washing whether by hand or by machine, speci fic formulation employed, etc.

It has been stated hereinbefore that photo-activator usage can be from about 0.001% to about 2.0% by weight based on the bleach composition, preferably from about 0.005% to about 0.1%. Combining these figures with the foregoing detergent bleach concentrations in water yields the results that photo-activator concentrations in water range from about 0.01 part per million ~ppm ) to about 120 ppm. Within this range, from about 0.05 to 1 ~1 63~03 about 6 ppm. are preferred. The lower side o~ the fore-going ranges are especially effective when the laundry process involves exposing fabric to photo-activator ~or a relatively long time, as for example during a 30 to 120-minute presoak, followed by a 20 to 30-minute wash, and drying the fabric in brilliant sunlight. The higher side of the foregoing ranges are needed when the laundry process involves exposing ~abric to photo-activator for a relatively short time, as for example during a short 10-minute wash, followed by drying in an illuminated dryer, on a line indoors, or outdoors on a cloudy da~.
While exposure to oxygen and light are essential, the source, intensity and duration of exposure of the light affect merely the degree of bleaching achieved.
In all the above conditions photo-bleaching occurs in contrast to the porphine photo-activators of the art, without the risk of undesirable colouring of the sub-strate.

-The absorption specctra of zinc-2,3-naphthalocyanine (ZNPC) of the invention and zinc phthalocyanine (ZPC) in dimethylformamide (DMF) solvent and of aluminium phtha-locyanine sulphonate (ALPCS) in water were determinedand shown in Figure 1. The figure shows zi~c naphthalo-cyanine ~tetra(2,3-naphtho)tetraaza porphine, zinc] ex-hibiting absorption with maximum intensity at a wave-length in the vicinity o~ 800 nm.

The relative photo-bleaching efficiency on Direct Red 81 of ZNPC of Example 1 was compared with that of ZPC and AlPCS. The results were plotted in Figure 2 showing DR 35 81 loss as function of irradiation time. The plots show the rate of loss of Direct Red 81 (DR 81) dye in soLu-63~03 tion when exposed to radiation from a 450 W Xe lampfiltered through a saturated Rhodamine B solution (Un-der these conditions - radiation wavelength ~ 600 nm -only the low energy transition of the phthalocyanine compounds are adsorbing. The high energy transition and the DR 81 are not excited). From this figure it can be seen that ZNPC of the invention photo-bleaches very much more efficiently than the conventional phthalocyanines.

Zinc 2,3-naphthalocyanine ~tetra(2,3--naphtho)tetraaza porphine, zinc], was prepared in a similar manner to as been described in the literature (A.Vogler ~ H.Kurkley, Inorganica Chimica Acta 1950, 44, L209) reacting naphtha-lene 2,3-dicarboxylic acid with urea and zinc acetate.
The resulting dark green solid was twice extracted in pyridine and vacuum dried. It was shown to have an elec~
tronic absorption spectrum, recorded in dimethyl ~orma-mide (DMF) solution, using a Perkin Elmer 552, spectro-meter with the following characteristics Wavelength ~ (nm) 760 720 678 381 (s)* 333 - Extinction coef.log. 5.15 4.29 4.34 4.78 4.61 *(s) = shoulder The spectrum -reported above is similar to that reported by Vogler and Kurkley for zinc 2,3-naphthalocyanine in chloronaphthalene solution. Assuming identical extinction coefficients in chloronaphtalene and DMF, the material prepared above was approx. 88% pure.

Zinc 2,3-naphthalocyanine sulphonate was prepared by adding 1 g of zinc 2,3-naphthalocyanine to 7.5 ml of 5%
fuming sulpheric acid and stirring at 117~C for 3 hours.

~ ~ 63~03 The reaction mixture was then cooled and carefully poured in to ice/water and then neutralised with 40% so-dium hydroxide solu~ion to give a green solution which w~s freeze-dried. The resulting solid was extracted wi~h methanol to give a green solid clearly containing sodium sulphate as impurity. The electronic absorption spectrum of this material recorded in 10% DMF/~20 soLution had the following charac~eristics Wavelength ~ (nm) 763 723 679 333 Extinction coef.log.~+ 4.99 4.16 4.19 4.4S

assuming tetra sulphonation, i.e. [tetra(sulpho-2,3-naphtho)tetraaza porphine, zinc, sodium salt~.
~XAMPLE 4 Aluminium 2,3- naphthalocyanine was prepared as follows:
-3g (0.017 moles) of 2,3 dicyanonaphthalene (see prepa-ration method below) was melted (251C) and 1 g (0.0075 moles) of anhydrous aluminium chloride added. The mixture was stirred for an hour at 300C. The reaction mixture was cooled and the dark solid resulting was ground to a fine powder, washed with water and then acetone and dried in a vacuum oven to give a dark green solid (3.2 g). The electronic absorption spectrum of this material recorded in DMF solution had the following absorption maxima Wavelength ~ (nm) 767 724 683 336 Extinction coef. log.~ 5,29 4.50 4.51 4.81 The 2,3-dicyano naphthalene used in this preparation was prepared according to a method of Russian Patent 232,963. A solution of 8.49 (0.02 moles) of w-tetrabro-moxylene, 2.34 (0.03 moles) fumaronitrite and, 189 (O.L2 moles) anhydrous sodium iodide in 50 ml dry DMF was stirred at 75-80C for 6-8 hours. The reaction mix-. ~ ~

2-1 C 594 (R) ture was cooled and poured into 120 mls. of cold wa~er.
The resulting precipitate was filtered, washed with water, vacuum dried and recrystallised from benzene.
3.56 g of 2,3 dicyanonaphthalene was obtained with Mpt 251C (literature 251C).
Aluminium 2,3 naphthalocyanine sulphonate was prepared by adding 1.0 g (1,35x 10--3 mole) of aluminium 2,3-naphthalocyanine to 7.5 mls of 5% fuming sulphuric acid and stirring for 3 hours at 117C. The reaction mixture was cooled and carefully poured into ice/water and neu-tralised with 40% sodium hydrGxide to give a green co-loured solution. This aqueous solution was freeze dried and the resulting solid with methanol to give 1.63 g of material (clearly containing sodium sulphate as impurity).
This material gave the following electronic absorption spectrum maxima when recorded in 10~ DMF/H20 solution Wavelength J\ (nm) 767 728 685 340 Extinction coef.log~ x 4.67 3.91 3.92 4.21 x assuming tetrasulphonation, i.e. [tetra(sulpho-2,3-naphtha)tetraaza porphine, aluminium, sodium salt].

~agnesium-2,3-naphthalocyanine was prepared as follows:
2.04 g of 2,3 dicyanonaphthalene were heated in 70 mls chloronaphthalene and 0.35 g magnesium powder added when dissolved (the 2,3 dicyanonaphthalene was prepared and puriied using methods described in Example 2). The reaction mixture was heated until it began to reflux, by which time the mixture had darkened. Refluxing was con-tinued or about 30 minutes or until the reaction was observed to have gone to completion.

~_ J ~ ~ ~ L~ ~
1 ~ 634~3 The mixture was allowed to cool and was filtered on mi-crocrystalline paper. The residue was dried in a vacuum oven at 80C while the filtrate, although containing some magnesium 2,3-naphthalocyanine was discarded.
1.731 g o product was thus obtained (theoretical full conversion yield - 2.106 g).
., The absorption spectrum of magnesium-2,3-naphthalo-cyanine recorded in DMF exhibited the following maxima Wavelength ~ (nm~ 755 719 674 Extinction coef. log. 5.11 4.38 4.36 Metal free-2,3 naphthalocyanine was prepared as follows:
0.5 g of magnesium 2,3-naphthalocyanine was dissolved in 38 ml of 98% sulphuric acid and left to stand at room temperature for 15 minutes. It was then filtered on to ice using a vacuum and a 3 sintered glass funnei. The brown precipitate was washed with 20 ml of 98% sulphu-~ric acid. Dilution of the acid solution to 500 ml re-precipated the brown material which was filtered, using a 4 sinter and the precipitate was washed with water and ethanol. It was then vacuum dried at 90C. 0.162 g of material were obtained which in chloronophthalene ex-hibited electronic absorption maxima at 784, 745 and 696 `nm.

Bleaching of the fugitive dye Direct Fast Red 5B (DR 81).

The bleaching of the fugitive dye Direct Fast Red 5B has been used as a model system for the simulation of dye-transfer inhibition effectiveness and for the bleaching of such species on fabric surfaces. This direct dye is similar in chemical structure to many direct dyes used in C 594 (R) ` ~ ~ 3 ~3~0~

the textile and dyeing industries and is a highly suitable model system due to its exceptional light fastness.

(a) In Table 1 below can be seen results of the compa-rison of the bleaching efficiency of Direct Fast Red 5B
using zinc phthalocyanine (ZPC3, zinc-2,3-naphthalo-cyanine (ZNPC) and aluminium 2,3- naphthalocyanine (AlNPC). The photosensitizers were dissolved in DMF and B lo were subjected to radiation emitted ~ rom ~ 450 W Xenon lamp filtered either through (a) a ~ /H20 filter (the transmitted radiation reasonably simulating solar radiation) or (b) an aqueous Rhodamin B solution, allow-ing only radiation of ~ 600 nm to be transmitted.
The three photosensitizers were compared at equal op tical densities at their respective visible/uv absorption maxima.

TABLE I
Photosensitizer Illumination Relative Rate of loss suppliedof DR 81 ZPC Simulated solar 34 ZPC > 600 nm 13 ZNPC Simulated solar 368 ZNPC > 600 nm 116 AlNPC Simulated solar 23.4 AlNPC ~ 600 nm 9.0 - - ~ 3 ~3~3 It can be clearly seen that the two naphthalocyanines tested, that have their Q band màxima ~ 700 nm, photo-bleach DR 81 and that the rate of bleaching is comparable with ZPC for AlNPC and a superior for ZNPC.
(b) In this example of the photo-bleaching efficiency of the porphine systems of this invention, the direct dye Direct Fast Red 5B has again been bleached and the effi-ciency of its photo-bleaching with AlNPCS, Z~PCS, AlPCS
compared in aqueous solution.

The photosensitizers whose photo-bleaching has been com-pared were again all employed at concentrations resul-ting in identical optical densities at their respective Q band absorption maxima.

As in Example 1 (a? radiation was supplied from a 450W
Xenon lamp filtered either through a pyrex/water system or a Rodamin B solution.
Again it is clear that the examples of this invention photo-bleach DR 81 in aqueous solution at least as effi ciently as a phthalocyanine whose Q band absorption maximum in the visible region of the electromagnetic spectru~ results in a high degree of colouration.

~ TABLE II

Photosensitizer IlluminationRelative Rate suppliedof loss of DR 81 AlPCS * Simulated solar 15.5 ~ 600 nm 8.8 AlNPCS * Simula~ed solar 15.2 - 35 ~ 600 nm 12.5 ZNPCS + Simulated solar 25.0 C 594 (R) - -- 11 G34()3 * solvent = 40% MeOh/H20.

+ aqueous solution in the presence of 5g/l synperonic 7 E0 nonionic surfactant.

When bleaching experiments were made on direct dye Acrinol Yellow TC 180, the results were as shown in Table III.
TABLE III

Photosensitizer Radiation Relative Photo-bleaching Ef~iciency AlNPCS Simulated 87 solar AlPCS Simulated 72 solar Solution: 40% methanol/H20.Radiation: Simulated solar, supplied by an Atlas Wea-therometer fitted with a 6KW Xenon lamp whose radiation 25 is suitably fil~ered.

Abbreviations Used:

ZPC - zinc phthalocyanine AlPC - aluminium ph~halocyanine AlPCS - sulphonated aluminium phthalocyanine ZNPC - zinc 2,3-naphthalocyanine ZNPCS - sulphonated zinc 2,3-naphthalocyanine AlNPC ~- aluminium 2,3-naphthalocyanine 35 AlNPCS - sulphonated aluminium 2,3-naphthalocyanine 3 ~ 0 3 MgNPC - magnesium 2,3-naphthalocyanine NPC - 2,3-napthalocyanine DR 81 - Direct Fast Red 5B
DMF - dimethyl formamide.

Suitable bleach compositions for fabrics were formulated from the following fabric washing composition and incor-porating therein by dry mixing 0.05~ by weight of the zinc-2,3-naphthalocynine sulphonate of Example 3 and 0.05% by weight of the aluminium 2,3-naphthalocyanine sulphonate of Example 4, respectively.

Composition % by weight Sodium C12 alkyl benzene sulphonate 14~5 Sodium stearate 2.5 Norylphenol/10 ethyleneoxide 3.0 Sodium triphosphate ~ 16.0 Alkaline sodium silicate 12.0 Sodium carboxymethylcellulose 0.5 Sodium toluene sulphonate 1.5 Sodium sulphate 30.0 Opti~cal brightener, perfume 0.5 Water and miscellaneous 19~5 These compositions, when used at about 5gjl. in wash so~
lutions, showed bleaching performances comparable to zinc- or aluminium phthalocyanine sulphonates, but having the advantage of non~colouring the substrate.

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A bleach composition comprising a porphine photo-activator, characterised in that the porphine photo-acti-vator is a weakly colouring to non-colouring porphine photo-activator having the general formula wherein X is individually (=N-) or (=CY-), the total number of (=N-) groups being at least one; wherein Y is individually hydrogen or optionally substituted alkyl, cycloalkyl, aral-kyl, aryl, alkaryl or heteroaryl; wherein each of R1, R2, R3 and R4 is individually an optionally substituted ortho-arylene system forming together with a pyrrole ring in the porphine core a condensed nucleus; wherein M is 2(H) atoms bound diagonally opposite nitrogen atoms, or Zn (II), Ca (II), Mg (II), Al (III) or Sn (IV); wherein Z is any necessary counter ion for the solubilizing groups; wherein n is the number of solubilizing groups, wherein substituted into Y or any R1, R2, R3 and R4 may be A, a solubilizing group selec-ted from the group consisting of (a) cationic groups, where Z is an anion and n is from 0 to about 10 (b) polyethoxy-late nonionic groups - (CH2CH20/gH, where Z is zero, n is from 0 to about 10, and G=ng= the number of condensed ethyl-ene oxide molecules per porphine molecule is from 0 to about 70; (c) anionic groups where Z is a cation and n isfrom 0 to about 10; such that the lowest energy allowed electronic transition of the photo-activator molecule gives rise to an absorption band (Q band) with a maximum intensity, at a wavelength greater than 700 nm.

C 594 (R)

2. A bleach composition according to claim 1, charac-terised in that each R1, R2, R3 and R4 is individually an optionally substituted ortho-naphthalene system forming a condensed nucleus together with a pyrrole ring in the por-phine core.

3. A bleach composition according to claim 1 or 2, characterised in that X is (=N-).

4. A bleach composition according to claim 1, characterised in that the absorption band with maximum in-tensity is at a wavelength in the range of 700 - 900 nm.

5. A bleach composition according to claim 1, charac-terised in that the porphine photo-activator is present in an amount of 0.001% to 2.0% by weight of the composition.

6. A bleach composition according to claim 5 characte-rised in that the porphine photo-activator is present in an amount of 0.005% to about 0.1% by weight of the composition.

7. A bleach composition according to c 1 a i m 1, characterised in that it contains a sur-factant.

8. A blsach composition according to claim 7, charac-terised in that the surfactant comprises a cationic and/or a nonionic surfactant.

9. A process for bleaching substrates or liquids using a porphine photo-activator, characterised in that a weakly co-louring to non-colouring porphine photo-activator as defined in claim 1 is used in the presence of sunlight, natural or artificial light having radiation wavelength greater than 600 nm.