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(11) | EP 0 837 124 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Fluorescent whitening agent formulation |
| (57) The present invention provides a liquid fluorescent whitening agent formulation which
is a solution having a viscosity of 50 to 5000 mPas, preferably 100 to 3500 mPas,
especially 100 to 1000 mPas and which comprises:
a) 10-25%, preferably 15-20% by weight of an anionic fluorescent whitening agent, based on the total weight of the formulation; b) 15-35%, preferably 20-30% by weight of a polar solvent, based on the total weight of the formulation; and c) 45-75%, preferably 50-70% by weight, based on the total weight of the formulation,
of a nonionic surfactant having the formula:
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[0001] The present invention relates to a fluorescent whitening agent formulation and, in particular, to a liquid fluorescent whitening agent formulation comprising a solution of a fluorescent whitening agent in a specific type of nonionic surfactant.
[0002] Traditionally, detergent manufacturers have produced solid detergent products by spray drying an aqueous slurry containing the various components of the detergent composition, including a fluorescent whitening agent. For this purpose, the detergent manufacturers prefer to use the fluorescent whitening agent component in the form of a liquid formulation, in order to facilitate the incorporation of the fluorescent whitening agent into the slurry to be spray-dried. As a consequence, fluorescent whitening agents are often supplied to the detergent manufacturers in the form of an aqueous slurry. Such aqueous slurries of fluorescent whitening agent, however, usually contain large amounts of water, which must be removed during subsequent spray drying, and are often beset by problems, such as the formation of clumps during spray-drying, as well as instability to sedimentation on storage.
[0003] It has recently been found that detergent manufacturers can considerably simplify the detergent production process by applying a liquid formulation of a fluorescent whitening agent, at the end of the detergent production process, to a previously spray-dried granular-form mixture of the remaining detergent components. For this application, there is a need to provide the fluorescent whitening agent in a liquid form in which the water content is reduced. Moreover, the detergent manufacturers have expressed a wish that the fluorescent whitening agent be provided in the form of a homogeneous solution, namely in a form which avoids the problems associated with traditional aqueous slurries. A still further requirement is that the viscosity of said homogeneous solution be sufficiently low to permit conventional pumping of the fluorescent whitening agent formulation.
[0004] Also known are liquid formulations of fluorescent whitening agents which use organic solvents and are substantially anhydrous. These liquid formulations, however, are usually highly viscous and need to be incorporated into the detergent powder by means of special mixing techniques.
[0005] Surprisingly, it has now been found that anionic fluorescent whitening agents are soluble in a mixture comprising a predominant amount of a certain type of nonionic surfactant and a lesser amount of water, to provide stable, clear solutions of low viscosity.
[0006] Accordingly, the present invention provides a liquid fluorescent whitening agent formulation which is a solution having a viscosity of 50 to 5000 mPas, preferably 100 to 3500 mPas, especially 100 to 1000 mPas and which comprises:
a) 10-25%, preferably 15-20% by weight of an anionic fluorescent whitening agent, based on the total weight of the formulation;
b) 15-35%, preferably 20-30% by weight of a polar solvent, based on the total weight of the formulation; and
c) 45-75%, preferably 50-70% by weight, based on the total weight of the formulation,
of a nonionic surfactant having the formula:
in which m is 1, 2, 3 or 4 and, when m is 1, R is a C8-C18-alkyl residue or a C8-C18-alkylcarboxy residue; when m is 2, R is a C2-C4alkylene glycol residue from which the two hydroxy groups have been removed; when
m is 3, R is the residue of trimethylolpropane from which the three hydroxy groups
have been removed; and when m is 4, R is the residue of pentaerythritol residue from
which the four hydroxy groups have been removed; R1 is hydrogen, methyl or ethyl; and n is a number ranging from 1 to 40.
[0007] Preferably, m is 1, 3 or 4 and, when m is 1, R is a C8-C18-alkyl residue or a C8-C18-alkylcarboxy residue; when m is 3, R is the residue of trimethylolpropane from which the three hydroxy groups have been removed; and when m is 4, R is the residue of pentaerythritol residue from which the four hydroxy groups have been removed; R1 is hydrogen, methyl or ethyl; and n is a number ranging from 1 to 40.
[0008] The viscosity of the liquid fluorescent whitening agent formulation according to the present invention is determined at a shear force of 100/s and at a temperature of 25°C. ± 1°C.
[0009] Preferred anionic fluorescent whitening agents for use in the present invention are those having either of the formulae:
or
in which R2 and R3, independently, are OH, NH2, O-C1-C4-alkyl, O-aryl, NH-C1-C4-alkyl, N(C1-C4-alkyl)2, N(C1-C4-alkyl)(C1-C4-hydroxyalkyl), N(C1-C4-hydroxyalkyl)2, NH-aryl, morpholino, S-C1-C4-alkyl(aryl), Cl or OH; R4 is H, SO3M, O-C1-C4-alkyl, CN, Cl, COO-C1-C4-alkyl, or CON(C1-C4-alkyl)2; M is H, Li, Na, K, Ca, Mg, ammonium, mono-, di-, tri- or tetra-C1-C4-alkylammonium, mono-, di- or tri-C1-C4-hydroxyalkylammonium or ammonium that is di- or tri-substituted with a mixture of C1-C4-alkyl and C1-C4-hydroxyalkyl groups; and p is 0 or 1.
[0010] In the compounds of formulae (2) or (3), C1-C4-alkyl groups are, e.g., methyl, ethyl, n-propyl, isopropyl and n-butyl, especially methyl. Aryl groups are, e.g., naphthyl or, especially, phenyl.
[0011] Preferred compounds of formula (2) are those in which R2 and R3, independently, are methoxy, phenoxy, NH2, NH-methyl, N(methyl)2, N(methyl)(hydroxyethyl), NH-ethyl, N(hydroxyethyl)2, NH-phenyl, morpholino, S-methyl(phenyl), Cl or OH.
[0012] Specific examples of preferred compounds of formula (2) are those having one of the formulae:
and
[0014] Specific preferred examples of compounds of formula (3) are those having one of the formulae:
and
[0015] Especially preferred is the compound of formula (10) or a crystal modification thereof, as described in EP-A-0 577 557.
[0016] If desired, a mixture of two or more anionic fluorescent whitening agents may be used as component a) of the formulation according to the present invention.
[0017] The polar solvent, component b) of the formulation according to the present invention, is preferably water. If desired, however, water may be used together with one or more polar co-solvents such as an alkylene glycol, e.g. ethylene glycol or 1,2-propylene glycol, or a polyalkylene glycol, especially polyethylene glycol or polypropylene glycol. The amount of any co-solvent preferably ranges from 0-15% by weight, based on the total weight of the formulation.
[0018] The radical R in the compounds of formula (1), when m is 1, is derived from a C8-C18-alkyl monoalcohol. Examples of such monoalcohols include naturally-occuring monoalcohols such as lauryl alcohol, myristyl alcohol, cetyl alcohol and stearyl alcohol, as well as synthetic alcohols such as 2-ethylhexanol, 1,1,3,3-tetramethylbutanol, octan-2-ol, isononyl alcohol, trimethylhexanol, trimethylnonyl alcohol, n-decanol, C9-C13-oxoalcohols, tridecyl alcohol, isodecyl alcohol or C8-C18-linear primary alcohols. Such C8-C18-linear primary alcohols are commercially available under the trade name Alfols, typical examples being Alfol (8-10), Alfol (9-11), Alfol (10-14), Alfol (12-13) and Alfol (16-18). The name "Alfol" is a registered trade mark.
[0019] Preferred examples of compounds of formula (1) in which m is 1 include, e.g., polyadducts of 3-20 moles of ethylene oxide with 1 mole of a C8-C18-alkyl monoalcohol. Especially interesting are polyadducts of 3-20 moles of ethylene oxide with 1 mole of a C11-C13-oxoalcohol and polyadducts of 8-20 moles of ethylene oxide with 1 mole of a C12-C14-fatty alcohol.
[0020] The radical R in the compounds of formula (1), when m is 2, is derived from a C2-C4alkylene glycol residue from which the two hydroxy groups have been removed. Examples of such C2-C4alkylene glycols include ethylene glycol, n-butylene glycol and, especially propylene glycol.
[0021] Preferred examples of compounds of formula (1) in which m is 2 include, e.g., polyadducts of 2-20 moles of ethylene oxide with 1 mole of a C2-C4alkylene glycols, preferably polyethylene glycol ethers of propylene glycol, in particular those having the formula:
in which x and y are each an integer within the range of from 1 to 10, preferably within the range of from 1 to 5, the sum of x and y preferably being about 10.
[0022] The alkyl radical R in the compounds of formula (1), when m is 3, is derived from trimethylolpropane.
[0023] Preferred examples of compounds of formula (1) in which m is 3 include polyadducts of 3-20 moles of ethylene oxide with 1 mole of trimethylolpropane. Especially interesting are polyadducts of 7-20 moles of ethylene oxide with 1 mole of trimethylolpropane.
[0024] The alkyl radical R in the compounds of formula (1), when m is 4, is derived from pentaerythritol.
[0025] Preferred examples of compounds of formula (1) in which m is 4 include polyadducts of 4-20 moles of ethylene oxide with 1 mole of pentaerythritol. Especially interesting are polyadducts of 5-20 moles of ethylene oxide with 1 mole of pentaerythritol.
[0026] Mixtures of two or more of the compounds of formula (1) may be used as component c) of the formulation according to the present invention.
[0028] Optional auxiliaries which may be present in the formulation of the present invention include stabilisers which are effective in adjusting the flow properties of the formulation, anti-foam agents, alkaline agents, fabric softeners, anti-redeposition agents, antioxidants, auxiliary builders such as polyacrylic acid and fragrances.
[0029] Examples of such stabilisers include, e.g., kaolin, an Mg/Al silicate, especially bentonite, montmorillonite, a zeolite or a highly dispersed silicic acid.
[0030] The formulation of the present invention may be produced by mixing fluorescent whitening agent, solvent and the compound of formula (1) together with any optional auxiliaries, and homogenising the the mixture so obtained, preferably at an elevated temperature, e.g. at 40-100°C. Mixing is conveniently effected by a suitable stirring device.
[0031] The resulting formulation is normally a clear and stable solution. On occasion, however, it may be necessary to filter the formulation in order to remove minor amounts of insoluble components.
[0032] The formulation of the present invention is particularly suitable for incorporation into a dry detergent composition, conveniently by adding the required amount of the formulation of the present invention to a dry detergent composition and then homogenising the mixture so obtained. The formulation of the present invention may also be used, however, for the production of liquid detergents by adding the required amount of the formulation of the present invention to a liquid detergent composition and then homogenising the mixture so obtained.
[0033] The following Examples further illustrate the present invention. Parts and percentages shown therein are by weight unless otherwise stated. The viscosity data quoted in the Examples are expressed in mPas and are determined at a shear force of 100/s and at a temperature of 25°C. ± 1°C.
Example 1
[0034] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of a C13-oxoalcohol with 9 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent
whitening agent having the formula:
[0035] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. After 4-5 hours, an almost clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 40-50°C. and filtered. A clear yellow solution is obtained having an active substance content of 15% by weight, a water content of 25% by weight and a viscosity of 462 mPas.
Examples 2 to 7
[0036] Using the procedure described in Example 1, further solution formulations of the compound of formula (10) are prepared by varying the amounts of the respective components and/or by varying the number of parts of ethylene oxide in the condensation product. The results are set out in the following Table.
| Example | cpd. (10) presscake % by wt. | water % by wt. | parts of EO in adduct | adduct % by weight | Appearance of product at 25°C | Viscosity mPas |
| 2 | 30 | 10 | 8 | 60 | slightly opalescent | 397 |
| 3 | 30 | 15 | 9 | 55 | slightly opalescent | 505 |
| 4 | 30 | 0 | 10 | 70 | clear | 1060 |
| 5 | 30 | 10 | 10 | 60 | clear | 575 |
| 6 | 40 | 0 | 15 | 60 | clear | 1880 |
| 7 | 40 | 0 | 20 | 60 | clear | 3263 |
Example 8
[0037] The following materials are charged into a 1 litre flask:
600g. of an adduct of 1 part of a C13-oxoalcohol with 10 parts of ethylene oxide;
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10); and:
100g. of 1,2-propyleneglycol.
[0038] Using the procedure described in Example 1, a liquid formulation is obtained which is a clear solution at 25°C. and has a viscosity of 702 mPas.
Example 9
[0039] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of a C11-oxoalcohol with 11 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0040] Using the procedure described in Example 1, a liquid formulation is obtained which is a clear solution at 25°C. and has a viscosity of 397 mPas.
Example 10
[0041] The following materials are charged into a 1 litre flask:
100g. of deionised water;
420g. of an adduct of 1 part of a C13-oxoalcohol with 8 parts of ethylene oxide;
180g. of an adduct of 1 part of a C13-oxoalcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0042] Using the procedure described in Example 1, a liquid formulation is obtained which is a clear solution at 25°C. and has a viscosity of 434 mPas.
Example 11
[0043] The following materials are charged into a 1 litre flask:
150g. of deionised water;
385g. of an adduct of 1 part of a C13-oxoalcohol with 8 parts of ethylene oxide;
165g. of an adduct of 1 part of a C13-oxoalcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0044] Using the procedure described in Example 1, a liquid formulation is obtained which is a clear solution at 25°C. and has a viscosity of 550 mPas.
Example 12
[0045] The following materials are charged into a 1 litre flask:
50g. of deionised water;
455g. of an adduct of 1 part of a C13-oxoalcohol with 8 parts of ethylene oxide;
195g. of an adduct of 1 part of a C13-oxoalcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0046] Using the procedure described in Example 1, a liquid formulation is obtained which is a clear solution at 25°C. and has a viscosity of 540 mPas.
Examples 13 to 16
[0047] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0048] Using the procedure described in Example 1, a liquid formulation (Example 13) is obtained which is a clear solution at 25°C. and has a viscosity of 1600 mPas.
[0049] Similar good results are obtained when the adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide is replaced by an adduct of 1 part of a C12-C14-fatty alcohol with 20 parts of ethylene oxide (Example 14; viscosity 3261 mPas); or by an adduct of 1 part of a C12-C14-fatty alcohol with 8 parts of ethylene oxide (Example 15; viscosity 829 mPas); or when no deionised water is used and the amount of the moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10) is increased to 400g (Example 16; viscosity 2417 mPas).
Examples 17 and 18
[0050] The following materials are charged into a 1 litre flask:
100g. of deionised water;
420g. of an adduct of 1 part of a C12-C14-fatty alcohol with 8 parts of ethylene oxide;
180g. of an adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0051] Using the procedure described in Example 1, a liquid formulation (Example 17) is obtained which, after filtration, is a clear solution at 25°C. and has a viscosity of 732 mPas.
[0052] Similar good results are obtained when the amount of the adduct of 1 part of a C12-C14-fatty alcohol with 8 parts of ethylene oxide is reduced to 300g. and the amount of the adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide is increased to 300g (Example 18; viscosity 893 mPas).
Examples 19 and 20
[0053] The following materials are charged into a 1 litre flask:
150g. of deionised water;
385g. of an adduct of 1 part of a C12-C14-fatty alcohol with 8 parts of ethylene oxide;
165g. of an adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0054] Using the procedure described in Example 1, a liquid formulation (Example 19; viscosity 807 mPas) is obtained which, after filtration, is a clear solution at 25°C.
[0055] Similar good results are obtained when the amount of the adduct of 1 part of a C12-C14-fatty alcohol with 8 parts of ethylene oxide is reduced to 275g. and the amount of the adduct of 1 part of a C12-C14-fatty alcohol with 15 parts of ethylene oxide is increased to 275g (Example 20; viscosity 913 mPas).
Examples 21 to 23
[0056] The following materials are charged into a 1 litre flask:
600g. of an adduct of 1 part of pentaerythritol with 5 parts of ethylene oxide; and
400g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0057] Using the procedure described in Example 1, a liquid formulation (Example 21; viscosity less than 500 mPas) is obtained which is a clear solution at 25°C.
[0058] Similar good results are obtained when the adduct of 1 part of pentaerythritol with 5 parts of ethylene oxide is replaced with the adduct of 1 part of trimethylolpropane with 7 parts of ethylene oxide (Example 22; viscosity 446 mPas); or with the adduct of 1 part of trimethylolpropane with 20 parts of ethylene oxide (Example 23; viscosity 558 mPas).
Examples 24 to 26
[0059] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of pentaerythritol with 5 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0060] Using the procedure described in Example 1, a liquid formulation (Example 24; viscosity less than 500 mPas) is obtained which is a clear solution at 25°C.
[0061] Similar good results are obtained when the adduct of 1 part of pentaerythritol with 5 parts of ethylene oxide is replaced with the adduct of 1 part of trimethylolpropane with 7 parts of ethylene oxide (Example 25; viscosity 101 mPas); or with the adduct of 1 part of trimethylolpropane with 20 parts of ethylene oxide (Example 26; viscosity 206 mPas).
Examples 27 and 28
[0062] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of castor oil with 40 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0063] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. After 4-5 hours, an almost clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 50-60°C. and filtered. A clear yellow solution is obtained having an active substance content of 15% by weight, a water content of 25% by weight and a viscosity of 3000 mPas. The solution remains clear after standing for 2 days.
[0064] Similar results are obtained when the adduct of 1 part of castor oil with 40 parts of ethylene oxide is replaced by an adduct of 1 part of castor oil with 11 parts of ethylene oxide.
Example 29
[0065] The following materials are charged into a 1 litre flask:
1132g. of an alkylpolyglycoside (53%) based on a C10-C12alkanol; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0066] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. The evaporated water is separated. After 4-5 hours, an almost clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 50-60°C. and filtered. A clear dark brown solution is obtained having an active substance content of 12% by weight, a water content of 42% by weight and a viscosity of 3500 mPas.
Examples 30 and 31
[0067] The following materials are charged into a 1 litre flask:
600g. of polyethylene glycol of mean molecular weight 300; and
400g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0068] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. After 4-5 hours, an almost clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 50-60°C. and filtered. A clear yellow solution is obtained having an active substance content of 20% by weight and a water content of 20% by weight. The solution remains clear after standing for 2 hours.
[0069] Similar results are obtained when the combination of 200g. of deionised water with 200g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10) is replaced by a combination of 100g. of deionised water and 300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
Example 32
[0070] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of sorbitol monooleate with 20 parts of ethylene oxide; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0071] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. After 4-5 hours, an almost clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 50-60°C. and filtered. A clear yellow solution is obtained having an active substance content of 15% by weight, a water content of 25% by weight and a viscosity of 3300 mPas. The solution remains clear after standing for 2 days.
Example 33
[0072] The following materials are charged into a 1 litre flask:
100g. of deionised water;
600g. of an adduct of 1 part of an ethoxylated lauric acid polyglycerol ester; and
300g. of a moist presscake (containing 50% by weight of active substance) of the fluorescent whitening agent having the formula (10).
[0073] The suspension so obtained is heated, with stirring, to an internal temperature of 70-80°C. After 4-5 hours, a clear solution is obtained which contains less than 1% by weight of undissolved components. The solution is cooled to 50-60°C. and filtered. A clear yellow solution is obtained having an active substance content of 15% by weight, a water content of 25% by weight and a viscosity of 517 mPas. The solution remains clear after standing for 6 days.
a) 10-25% by weight of an anionic fluorescent whitening agent, based on the total weight of the formulation;
b) 15-35% by weight of a polar solvent, based on the total weight of the formulation; and
c) 45-75% by weight, based on the total weight of the formulation, of a nonionic surfactant
having the formula:
in which m is 1, 2, 3 or 4 and, when m is 1, R is a C8-C18-alkyl residue or a C8-C18-alkylcarboxy residue; when m is 2, R is a C2-C4alkylene glycol residue from which the two hydroxy groups have been removed; when
m is 3, R is the residue of trimethylolpropane from which the three hydroxy groups
have been removed; and when m is 4, R is the residue of pentaerythritol residue from
which the four hydroxy groups have been removed; R1 is hydrogen, methyl or ethyl; and n is a number ranging from 1 to 40.
or
in which R2 and R3, independently, are OH, NH2, O-C1-C4-alkyl, O-aryl, NH-C1-C4-alkyl, N(C1-C4-alkyl)2, N(C1-C4-alkyl)(C1-C4-hydroxyalkyl), N(C1-C4-hydroxyalkyl)2, NH-aryl, morpholino, S-C1-C4-alkyl(aryl), Cl or OH; R4 is H, SO3M, O-C1-C4-alkyl, CN, Cl, COO-C1-C4-alkyl, or CON(C1-C4-alkyl)2; M is H, Li, Na, K, Ca, Mg, ammonium, mono-, di-, tri- or tetra-C1-C4-alkylammonium, mono-, di- or tri-C1-C4-hydroxyalkylammonium or ammonium that is di- or tri-substituted with a mixture of C1-C4-alkyl and C1-C4-hydroxyalkyl groups; and p is 0 or 1.
or
or
in which x and y are each an integer within the range of from 1 to 10.