Cleaning compositions for solid surfaces – auxiliary compositions – Cleaning compositions or processes of preparing – Solid – shaped macroscopic article or structure
Reexamination Certificate
2000-03-09
2003-07-29
Gupta, Yogendra N. (Department: 1751)
Cleaning compositions for solid surfaces, auxiliary compositions
Cleaning compositions or processes of preparing
Solid, shaped macroscopic article or structure
C510S224000, C510S356000, C510S360000, C510S451000, C510S531000
Reexamination Certificate
active
06599871
ABSTRACT:
TECHNICAL FIELD
The present invention provides a detergent tablet comprising a nonionic surfactant having a melting point above ambient temperature suitable for use in an automatic dishwasher or laundry washing machine.
BACKGROUND
Detergent tablets in tablet form are known in the art. Detergent compositions in tablet form hold several advantages over particulate detergent compositions, such as ease of handling, transportation and storage. It is the aim of detergent tablet manufacturers to make tablets that are sufficiently hard such that they do not crumble or disintegrate on handling, transportation or storage.
Detergent tablets are traditionally prepared by the compression of a particulate detergent composition in a tablet press. The most common method used by detergent manufacturers to increase tablet hardness is to increase the compression pressure at which the tablets are formed. It has however, been found that dissolution of the tablet generally decreases with increasing compression pressure, leaving a residue of undissolved tablet.
Another consequence of increasing compression pressure is the parallel increase in force of ejection required to eject the tablet from the tablet press. Furthermore increasing compression pressure and force of ejection in the tablet press generally results in the outermost surface of the tablets becoming. In addition high compression pressure and ejection force may cause excessive wearing and potential damage to the tablet press itself. Damage to the outermost surface of the tablet, such as scoring or scratching is unacceptable to the consumer.
Soft tablets that crumble or hard tablets that dissolve slowly, leaving a residue are also unacceptable to the consumer. Detergent manufacturers have thus directed tablet development efforts toward striking a balance between tablet hardness and dissolution.
In addition, soft tablets tend to exhibit high levels of surface dustiness, leaving dust on the hands of the person handling the tablet. Surface dustiness is also unacceptable to the consumer.
EP-A-0,711,828 (Unilever) relates to a process for making tablets by compacting a particulate detergent tablet distributed within which is a binder material. The melting temperature of the binder is in the range of from 35° C. to 90° C. The detergent tablet is compacted at a temperature which is at least 28° C. but below the melting temperature of the binder. Preferably the binder is polyethylene glycol; a costly additional detergent component providing no detersive benefits.
It is the object of the present invention to provide a detergent tablet that is not only sufficiently hard to meet handling, transportation and storage needs without compromising the rate of dissolution, but which exhibits reduced surface dustiness and can also be readily ejected from the tablet press without causing damage to the outermost surface of the tablet or the tablet press.
SUMMARY OF THE INVENTION
According to the present invention there is provided a detergent tablet comprising a nonionic surfactant having a melting point above ambient temperature and wherein the detergent tablet is obtainable by a process comprising the steps of:
a) heating the nonionic surfactant to above its melting point to form a liquid nonionic surfactant;
b) applying the liquid nonionic surfactant to a premix of detergent components to form a detergent composition;
c) forming the detergent composition into tablets.
In addition there is also provided a detergent tablet wherein the detergent tablet is formed in a tablet press and is ejected from the tablet press at a temperature below the melting point of the nonionic surfactant.
DETAILED DESCRIPTION OF THE INVENTION
Nonionic Surfactant
The detergent tablets of the present invention comprise a nonionic surfactant having a melting point above ambient temperature.
Suitable nonionic surfactants include any low foaming nonionic surfactant suitable for incorporation into an automatic dishwashing or laundry detergent composition with a melting point above ambient temperature such the surfactant is preferably solid or but may be highly viscous (at least 20,000 cps, preferably at least 35,000 cps, most preferably at least 40,000 cps) or wax-like at ambient temperature. Preferably the nonionic surfactant provides satisfactory suds control.
The nonionic surfactants suitable for use herein have a melting point of preferably greater than 35° C., more preferably greater than 25° C. More preferably the nonionic surfactant has a melting point of between 25° C. and 60° C., more preferably between 26.6° C. and 43.3° C.
Preferred nonionic surfactants include nonionic alkoxylated surfactants, especially ethoxylates derived from primary alcohols, and blends thereof with more sophisticated surfactants, such as the polyoxypropylene/polyoxyethylene/polyoxypropylene (PO/EO/PO) reverse block polymers. The PO/EO/PO polymer-type surfactants are well-known to have sud suppressing action, especially in relation to common food soil ingredients such as egg.
In a preferred embodiment, the nonionic surfactant is an ethoxylated surfactant derived from the reaction of a monohydroxy alcohol or alkylphenol containing from 6 to 20 carbon atoms, with preferably at least 12 moles, more preferably at least 15 moles, most preferably at least 20 moles of ethylene oxide per mole of alcohol or alkyl phenol on an average basis.
A particularly preferred nonionic surfactant is derived from a straight chain fatty alcohol containing from 16 to 20 carbon atoms (C
16
-C
20
alcohol), preferably a C
18
alcohol, condensed with an average of preferably at least 12 moles, more preferably at least 15 moles, and most preferably at least 20 moles of ethylene oxide per mole of alcohol. Preferably the ethoxylated nonionic surfactant so derived has a narrow ethoxylate distribution relative to the average.
The nonionic surfactant preferably also contains propylene oxide groups. Preferably the nonionic surfactants contain propylene oxide groups in an amount up to 25% by weight, preferably up to 20% by weight, most preferably up to 15% by weight of the total nonionic surfactant.
Highly preferred nonionic surfactants are ethoxylated monohydroxy alcohols or alkyl phenols additionally comprising a polyoxyethylene, polyoxypropylene block polymeric compound; the ethoxylated monohydroxy alcohol or alkyl phenol fraction of the nonionic surfactant comprising greater than 30%, preferably greater than 50%, most preferably greater than 70% of the total nonionic surfactant.
A particularly preferred nonionic surfactant contains from 40% to 70% of a polyoxypropylene/polyoxyethylene/polyoxypropylene block polymer blend comprising 75%, by weight of the blend, of a reverse block co-polymer of polyoxyethylene and polyoxypropylene containing 17 moles of ethylene oxide and 44 moles of propylene oxide; and 25%, by weight of the blend, of a block co-polymer of polyoxyethylene and polyoxypropylene initiated with trimethylolpropane and containing 99 moles of propylene oxide and 24 moles of ethylene oxide per mole of trimethylolpropane.
Nonionic surfactant which may also be used include those POLY-TERGENT® SLF-18 nonionic surfactants from Olin Corp., having the melting point properties discussed herein above.
A preferred nonionic surfactant has the general formula:
R
1
O[CH
2
CH(CH
3
)O]
x
[CH
2
CH
2
O]
y
[CH
2
CH(OH)R
2
] (I)
wherein R
1
is a linear or branched, aliphatic hydrocarbon radical having from 4 to 18 carbon atoms including mixtures thereof; R
2
is a linear or branched aliphatic hydrocarbon radical having from 2 to 26 carbon atoms including mixtures thereof; x is an integer having an average value of from 0.5 to 1.5; and y is an integer having a value of least 15.
Another preferred nonionic surfactant is the ether-capped poly(oxyalkylated) alcohol surfactants having the formula:
R
1
O[CH
2
CH(R
3
)O]
x
[CH
2
]
k
CH(OH)[CH
2
]
j
OR
2
wherein R
1
and R
2
are linear or branched, saturated or unsaturated, aliphatic or aromatic hydrocarbon radicals having from 1
Bolam Brian M.
Dressman Marianne
Gupta Yogendra N.
Mruk Brian P.
The Procter & Gamble & Company
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