Process for preparing a solid detergent block

A detergent block of compressed granular material is provided, said block having a weight of 0.2-10 kg, being substantially free of phoshate builder material, and comprising a granulated builder material, an alkaline agent and a compressing aid. A process is also provided for preparing a block of compressed granular material being substantially free of a phosphate builder and having a weight of 0.2 to 10 kg, said process involving the steps of PA1 (i) granulating a non-phosphate builder material, with 0.1-10% by weight based on the weight of the builder of a co-ingredient selected from polycarboxylic polymer solutions, alkali metal silicate solutions, and mixtures thereof;and PA1 (ii) compressing a particulate mixture of said granulated builder material and other components of the block, including a compressing aid, in a mould under a pressure of 3-30 kN/cm.sup.2.

FIELD OF THE INVENTION 
The present invention relates to a solid detergent block for obtaining an 
aqueous chemical solution having a substantially constant concentration. 
The invention also relates to a process for preparing such a block. Such 
detergent blocks are suitable for use in an industrial cleaning process, 
particularly a mechanical warewashing process and generally comprise 
alkaline agents and detergency builders. 
BACKGROUND OF THE INVENTION 
Industrial ware washing machines generally comprise a wash tank which 
contains the cleaning solution for the wash process. In this process, the 
soiled wash load is doused with the cleaning solution and subsequently 
with rinse water which falls into the wash tank. Each cycle, the cleaning 
power of the cleaning liquor is reduced, first because some is exhausted 
by the soil-removing process and, secondly, because it is diluted with 
rinse water. The cleaning solution is therefore recharged from time to 
time by adding fresh cleaning product from a dispenser system, which 
usually provides liquid product or a concentrated aqueous solution of a 
composition including solid chemicals. 
A number of techniques are known for converting solid chemicals into a 
concentrated solution, dependent on the nature of the solid. For example, 
according to U.S. Pat. No. 2,371,720 a solid powdered chemical can be 
dissolved by placing it on a sieve and spraying water on to said sieve 
from below. 
Alternatively, the powdered material can be dissolved in a dispenser of the 
"water-in-reservoir" type. In this type of dispenser, the powdered 
material is submerged under water, which therefore becomes loaded or even 
saturated with the powder. When more water is added, the excess solution 
flows into an overflow pipe leading to the washing machine. 
It is also possible to use solid detergent materials in the form of 
briquettes such as, for instance, described in U.S. Pat. No. 2,382,163, 
2,382,164 and 2,382,165. Briquettes can be used with a 
"water-in-reservoir" type of dispenser. 
A well-known type of solid detergent is the cast block form, whereby a 
solid detergent block having a weight of several kilograms is formed by 
pouring a concentrated aqueous slurry into a container, in which it 
solidifies upon cooling as a result of the hydration of the salts in the 
composition. Such cast solid blocks are, for example, described in 
European patent 3,769. 
These solid blocks cast in containers require dispensing systems whereby 
water is sprayed onto the block while it is inside the container, thereby 
gradually dissolving the exposed surface to form a concentrated solution. 
Such a dispenser system is, for instance, described in European patent 
application 244,153. 
Solid detergent blocks have won a certain degree of popularity in the area 
of industrial warewashing because they constitute a non-dusty and 
therefore relatively safe product form for the often aggressive chemicals 
used. Furthermore, hydrated solid blocks are economical in use because 
they can be manufactured and transported as concentrated products. 
However, elevated temperatures are required in the manufacturing process of 
the above-mentioned solid detergent blocks and these temperatures have an 
adverse effect on the stability of heat-labile components of the blocks. 
In EP-A-375,022, an alternative type of detergent block is disclosed, 
namely a block of compressed granular material. This block constitutes an 
even more concentrated product and enables the incorporation of 
heat-labile components such as bleach compounds. 
However, the quality of said compressed blocks was found to be inadequate 
if they were prepared from material substantially free of any phosphate 
builder. 
We have now surprisingly found that compressed blocks of good quality but 
being substantially free of phosphate builder, can be produced by applying 
the process of the present invention. 
In the context of the present invention, a good quality detergent block is 
defined as a block having a bulk density of 1200-2100 kg/m.sup.3 and 
showing neither cracks in the block (lamination) nor at the top or bottom 
surface of the block (capping). Furthermore, a block which is 
substantially free of phosphate builder is defined as a block not 
containing more than 1% by weight of phosphorus. 
DEFINITION OF THE INVENTION 
According to the invention there is provided a process for preparing a 
block of compressed granular material being substantially free of a 
phosphate builder and having a weight of 0.2 to 10 kg, said process 
involving the steps of 
(i) granulating a non-phosphate builder material, with 0.1-10% by weight 
based on the weight of the builder of a co-ingredient selected from 
polycarboxylic polymer solutions, alkali metal silicate solutions, and 
mixtures thereof; 
(ii) optionally, drying the thus-granulated builder material in a fluid bed 
to a free moisture content of less than 5% by weight, preferably less than 
3% by weight; and 
(iii) compressing a particulate mixture of said granulated builder material 
and other components of the block, including a compressing aid, in a mould 
under a pressure of 3-30 kN/cm.sup.2. 
Another aspect of the invention is a solid detergent composition in the 
form of a block of a compressed granular material, said block having a 
weight of 0.2-10 kg, being substantially free of a phosphate builder and 
comprising: 
(i) 15-70% by weight of a granulated builder material including a 
non-phosphate builder and 0.1-10% by weight based on the weight of said 
builder of a co-ingredient as defined herein; 
(ii) 5-80% by weight of an alkaline agent; 
(iii) 0.5-5% by weight of a compressing aid selected from nonionic 
surfactants, metal soaps, paraffins, talcum powder, polyethylene glycol, 
mixtures of ketones and fatty alcohols, and mixtures thereof; 
(iv) 0-20% by weight of a bleaching agent.

DETAILED DESCRIPTION OF THE INVENTION 
Using the process of the invention, physically stable detergent blocks 
having a porosity of at most 10% by volume and a bulk density of 1200-2100 
kg/m.sup.3, preferably 1500-1900 kg/m.sup.3, can be prepared. For 
environmental reasons, said blocks do preferably not contain any phosphate 
builder. 
The detergent blocks of the invention have a weight of 0.2-10 kg, 
preferably 1-5 kg. The blocks are usable for various applications in the 
area of industrial cleaning, such as mechanical warewashing and fabric 
washing, but other industrial detergent processes are also envisaged (e.g. 
bottle washing or conveyor belt lubricating). The blocks are particularly 
suitable for use in a mechanical ware washing process. 
The detergent blocks of the invention generally contain detergent 
components usually found in material suitable for use in an industrial 
washing machine, such as a detergency builder, an alkaline agent, a 
bleaching agent and one or more types of foam-depressing and lubricating 
material. 
The granulating step 
During the granulation step, non-phosphate builder material is granulated 
with 0.1-10% by weight based on the weight of the builder of a 
co-ingredient selected from polycarboxylic polymer solutions, alkali metal 
silicate solutions, and mixtures thereof. 
The granulation step is preferably carried out by dry-mixing the builder 
with the co-ingredient, desirably at room temperature. This may be 
effectively performed in a Loedige or Fukae type batch or continuous 
mixer. Alternatively, the builder material may be granulated by forming a 
slurry containing said builder and the co-ingredient and subsequently 
spray-drying the slurry. If needed, the thus obtained granulated builder 
material may be dried in a fluid bed to a free moisture content of less 
than 5% by weight, preferably less than 3% by weight (measured at 
120.degree. C.). It was observed that the compactibility of the 
particulate mixture used for preparing the detergent block of the 
invention could be improved by applying the above described drying step. 
Suitable polycarboxylated polymers for use as co-ingredient are selected 
from the group consisting of homopolymers and copolymers of one or more of 
acrylic acid, methacrylic acid, maleic acid, acrylamide, itaconic acid, 
(C.sub.1 -C.sub.4)-alkyl (meth)-acrylates or amides, alpha-chloroacrylic 
acid, alkyl-vinylether or vinylesthers. Most preferred polymers are 
selected from the group of homopolymers and copolymers of acrylic acid and 
maleic acid. 
An alkali metal silicate solution is preferred for use as co-ingredient 
since this material can be used at much lower levels (i.e. 0.25-5%, 
preferably 0.5-3.0% by weight based on the weight of the non-phosphate 
builder) than the polycarboxylated polymer owing to its lower viscosity. 
The viscosity of the silicate solution is lower than 400 mPas at 
20.degree. C. whereas the viscosity of the polycarboxylated polymer 
solution is generally considerably higher. Preferably, sodium silicate 
containing silicium oxide and sodium oxide at a weight ratio in the range 
of 1.0-3.3, especially of 1.5-2.2, is applied. 
The compressing aid is selected from nonionic surfactants, metal soaps, 
paraffins, talcum powder, polyethylene glycol, mixtures of ketones and 
fatty alcohols, and mixtures thereof. Preferred types of compressing aids 
are nonionic surfactants and mixtures of ketones and fatty alcohols. The 
compressing aid is present at a level of 0.5-5% by weight, preferably 1-3% 
by weight, based on the total weight of the detergent block. 
After the above-described process steps, the granulated builder material is 
mixed with the other components of the detergent block including the 
compressing aid to form a particulate mixture. Subsequently, said mixture 
is compressed in a mould under a pressure of 3-30 kN/cm.sup.2, preferably 
3-15 kN/cm.sup.2. 
This compaction step can be carried out in a suitable press, preferably a 
hydraulic press, for instance a LAEIS Hydraulische Doppeldruckpresse, TYP 
HPF 630 as manufactured by LAEIS, West Germany. 
Preferably, more than one compaction cycle is applied in order to maximise 
the block density and quality. 
Builder material 
Generally, the detergent block of the present invention contains from 
15-70% by weight of a builder material granulated according to the process 
of the invention. As mentioned above, said granulated material includes a 
non-phosphate builder and a co-ingredient. 
This non-phosphate builder material is preferably selected from the group 
consisting of sodium nitrilotriacetate, sodium citrate, phosphonates, 
aluminosilicates, polycarboxylates, layered silica, oxidised starch, 
polypeptides, oxidised heteropolymeric polysaccharides, salts of 
dipicolinic acid (DPA), ethylene diamine tetraacetic acid (EDTA), salts of 
terpolymers from acrylic acid, maleic acid and vinylacetate, 3 Na-salt of 
methylglycine diacetic acid. The most preferred types of non-phosphate 
builder material are sodium nitrilotriacetate, sodium citrate, and 3 
Na-salt of methylglycine diacetic acid. 
Alkaline material 
Depending on the specific application, the detergent block of the invention 
contains, in addition to the above builder component, from 5-80% by 
weight, preferably from 10-70% by weight, of an alkaline agent, such as 
sodium- or potassium-hydroxide, -silicate, particularly -metasilicate, or 
-carbonate. Generally, compositions for use in a mechanical warewashing 
machine are most alkaline and contain the highest levels of these alkaline 
agents, which levels are suitably in the range of 20-70% by weight. 
Bleaching agent 
The detergent block of the invention may also comprise a bleach component, 
encapsulated or not, in an amount of up to 20% by weight. Said bleach 
component may be a hypohalite bleach such as NaDCCA, or a peroxygen 
compound, i.e. a compound capable of yielding hydrogen peroxide in aqueous 
solution. 
For environmental reasons, a peroxygen compound selected from alkali metal 
peroxides, organic peroxides, such as urea peroxide, and inorganic 
persalts such as the alkali metal perborates, percarbonates, 
perphosphates, persilicates and persulphates, is preferably used. Mixtures 
of two or more of such compounds may also be suitable. 
Particularly preferred are sodium perborate tetrahydrate and, especially, 
sodium perborate monohydrate. Sodium perborate monohydrate is preferred 
because of its high active oxygen content. Sodium percarbonate may also be 
preferred for environmental reasons. 
The peroxygen bleach compound is suitably present in the detergent block of 
the invention at a level of up to 20% by weight, preferably of from 5 to 
10% by weight. On the other hand, if present the hypohalite bleach may be 
suitably used in an amount of up to 5%, preferably 1-4% by weight, as 
active chlorine. 
Organic peroxyacids may also be suitable as peroxygen bleaching agent. Such 
materials normally have the general formula: 
##STR1## 
wherein R is an alkylene or substituted alkylene group containing from 1 
to about 20 carbon atoms, optionally having an internal amide linkage; or 
a phenylene or substituted phenylene group; and Y is hydrogen, halogen, 
alkyl, aryl, an imido-aromatic or non-aromatic group, a COOH or 
##STR2## 
group or a quaternary ammonium group. 
Typical monoperoxy acids useful herein include, for example: 
(i) peroxybenzoic acid and ring-substituted peroxybenzoic acids, e.g. 
peroxy-.alpha.-naphthoic acid; 
(ii) aliphatic, substituted aliphatic and arylalkyl monoperoxyacids, e.g. 
peroxylauric acid, peroxystearic acid and 6-(N-phthalimido)-peroxyhexanoic 
acid (PAP); and 
(iii) 6-octylamino-6-oxo-peroxyhexanoic acid. 
Typical diperoxyacids useful herein include, for example: 
(iv) 1,12-diperoxydodecanedioic acid (DPDA); 
(v) 1,9-diperoxyazelaic acid; 
(vi) diperoxybrassilic acid; diperoxysebasic acid and diperoxyisophthalic 
acid; 
(vii) 2-decyldiperoxybutane-1,4-diotic acid; and 
(viii) 4,4'-sulphonylbisperoxybenzoic acid. 
Also inorganic peroxyacid compounds are suitable, such as for example 
potassium monopersulphate (MPS). If organic or inorganic peroxyacids are 
used as the peroxygen compound, the amount thereof will normally be within 
the range of about 2-10% by weight, preferably from 4-8% by weight. 
All these peroxide compounds may be utilized alone or in conjunction with a 
peroxyacid bleach precursor and/or an organic bleach catalyst not 
containing a transition metal. 
Peroxyacid bleach precursors are known and amply described in literature, 
such as in the British Patents 836988; 864,798; 907,356; 1,003,310 and 
1,519,351; German Patent 3,337,921; EP-A-0185522; EP-A-0174132; 
EP-A-0120591; and U.S. Pat. Nos. 1,246,339; 3,332,882; 4,128,494; 
4,412,934 and 4,675,393. 
Another useful class of peroxyacid bleach precursors is that of the 
cationic i.e. quaternary ammonium substituted peroxyacid precursors as 
disclosed in U.S. Pat. Nos. 4,751,015 and 4,397,757, in EP-A0284292 and 
EP-A-331,229. Examples of peroxyacid bleach precursors of this class are: 
2-(N,N,N-trimethyl ammonium) ethyl sodium-4-sulphonphenyl carbonate 
chloride--(SPCC); 
N-octyl,N,N-dimehyl-N.sub.10 -carbophenoxy decyl ammonium chloride --(ODC); 
3-(N,N,N-trimethyl ammonium) propyl sodium-4-sulphophenyl carboxylate; and 
N,N,N-trimethyl ammonium toluyloxy benzene sulphonate. 
A further special class of bleach precursors is formed by the cationic 
nitriles as disclosed in EP-A-303,520 and in European Patent Specification 
No.'s 458,396 and 464,880. 
Any one of these peroxyacid bleach precursors can be used in the present 
invention, though some may be more preferred than others. 
Of the above classes of bleach precursors, the preferred classes are the 
esters, including acyl phenol sulphonates and acyl alkyl phenol 
sulphonates; the acyl-amides; and the quaternary ammonium substituted 
peroxyacid precursors including the cationic nitriles. 
Examples of said preferred peroxyacid bleach precursors or activators are 
sodium-4-benzoyloxy benzene sulphonate (SBOBS); N,N,N'N'-tetraacetyl 
ethylene diamine (TAED); sodium-1-methyl-2-benzoyloxy 
benzene-4-sulphonate; sodium-4-methyl-3-benzoloxy benzoate; SPCC; 
trimethyl ammonium toluyloxy-benzene sulphonate; sodium nonanoyloxybenzene 
sulphonate (SNOBS); sodium 3,5,5-trimethyl hexanoyloxybenzene sulphonate 
(STHOBS); and the substituted cationic nitriles. 
The precursors may be used in an amount of up to 12%, preferably from 2-10% 
by weight, of the composition. Organic bleach catalyst most suitable for 
being utilized here are the so-called sulphonimides as disclosed in 
EP-A-0453003 and EP-A-0446982. 
Antiscaling agent 
The detergent block of the invention preferably also comprises up to 25% by 
weight of an anti-scaling agent, consisting of a polycarboxylated polymer 
and a carrier material therefore. The concentration of said polymer in 
said anti-scaling agent is preferably in the range of from 20 to 50% by 
weight as calculated on the total weight of the anti-scaling agent. When 
present, the anti-scaling agent is, preferably, substantially 
homogeneously mixed throughout the detergent block of the invention. 
Suitable polymer materials for this anti-scaling agent may be the same as 
those of which the solution is suitable for use as co-ingredient in the 
granulating step of the present invention. 
Suitable inorganic carrier materials are selected from the group consisting 
of sulphates, carbonates, silicates, aluminosilicates, percarbonates, 
perborates, clays, and mixtures thereof. Most preferred carrier material 
is selected from silicates, carbonates, and mixtures thereof. 
The detergent block of the invention may further comprise suitable minor 
ingredients, such as bleach stabilizers, enzymes, etc. 
The invention is illustrated by the following non-limiting Examples, in 
which parts and percentages are by weight unless otherwise stated. 
In the Examples, the following abbreviations are used: 
Trilon A92: sodium nitrilotriacetate containing 1 mole of water (laq), ex 
BASF; 
Norasol WL2-Si: 40% polyacrylate (mol wt 4500) on 30% sodium silicate 
(SiO.sub.2 :Na.sub.2 O=2) and 30% sodium carbonate, ex NorsoHaas 
Perborate mono: sodium perborate monohydrate, ex Atochem 
Caustic : sodium hydroxide micropearls, ex Solvay; 
Dehypon 2429 : mixture of ketones in fatty alcohol, ex Henkel; 
Dequest 2047 : calcium salt of ethylene diamine tetra methylene phosphonic 
acid, ex Monsanto; 
Crystal-112 : 45% alkaline silicate solution, ex Crosfield; 
Norasol LMW-45N: 40% solution of sodium polyacrylate (mol wt: 4500) in 
water, ex NorsoHaas. 
EXAMPLE 1, COMATIVE EXAMPLE A 
In a Lodige-type mixer, 25 parts of Norasol WL-2Si were sprayed upon with 2 
parts of Dehypon 2429. The resultant material was mixed with the following 
ingredients: 
______________________________________ 
1 A 
Example no. (parts) (parts) 
______________________________________ 
Dequest 2047 0.5 0.5 
Perborate mono 7.0 7.0 
Caustic 50.0 50.0 
Sprayed Trilon A92 
-- 15.5 
NTA-granules 15.5 -- 
______________________________________ 
Said NTA-granules (NTA: sodium nitrilotriacetate) were made by granulating 
94.96 parts of Trilon A92 with 2.16 parts of Crystal-112 and subsequently 
spraying said granulated material with 2.88 parts of Dehypon 2429. The 
moisture content of these NTA-granules as measured before the spraying 
step was 1.9% by weight. 
The sprayed Trilon A92 shown in the composition of Example A, was made by 
spraying 97.12 parts of of Trilon A92 with 2.88 parts of Dehypon 2429. 
In both cases, the resulting powder was compressed to 3 kg blocks (having a 
density of 1710 kg/m.sup.3) in a mould under a pressure of 12 kN/cm.sup.2 
using a double punch press. 
The blocks prepared by compressing the powder of Example 1 were of good 
quality/stability and did not show any sign of lamination or capping. On, 
the other hand, the blocks prepared by compressing the powder of 
comparative Example A showed both capping and lamination phenomena and 
were not physically stable. 
EXAMPLE 2, COMATIVE EXAMPLE B 
Powder-form mixtures having the following compositions were obtained by 
mixing the components in a Lodige-type mixer: 
______________________________________ 
2 B 
Example no. (parts) (parts) 
______________________________________ 
Dequest 2047 0.35 0.35 
Perborate mono 7.0 7.0 
Caustic 48.0 48.0 
Sprayed Trilon A-92 
-- 35.0 
Norasol WL-2Si 12.5 12.5 
NTA-granules 35.75 -- 
______________________________________ 
Said NTA-granules were previously prepared by granulating 33.0 parts of 
Trilon A92 with 0.75 parts of Crystal-112, and subsequently spraying the 
thus-prepared granulated material with 2.0 parts of Dehypon 2429. The 
moisture content of these NTA-granules as measured before the spraying 
step, was 1.9% by weight. 
The sprayed Trilon A92 shown in the composition of Example B, was made by 
spraying 33.0 parts of of Trilon A92 with 2.0 parts of Dehypon 2429. 
In both cases, the resulting powder was compressed to 3 kg blocks (having a 
density of 1680 kg/m.sup.3) in a mould under a pressure of 12 kN/cm.sup.2 
using a double punch press. 
Similarly as in Examples 1 and A, the blocks prepared by compressing the 
powder of Example 2 showed good quality and stability, whereas the blocks 
obtained from the powder of Example B showed capping and lamination and 
were physically not stable. 
It can be concluded that both at low and high levels of NTA, pregranulation 
of NTA results in significant improvement of the quality and stability of 
the detergent blocks obtained. 
EXAMPLE 3, COMATIVE EXAMPLE C 
In a Lodige type mixer, two types of NTA-granules (indicated as 
NTA-granules (1) and NTA-granules (2)) were prepared by granulating 33 
parts of Trilon A92 with 1.67 parts respectively 2.78 parts of Norasol LMW 
45N. The moisture content of NTA-granules (1) is 3.41% by weight and of 
NTA-granules (2) is 5.01% by weight. 
On to these NTA-granules, 2 parts of Dehypon 2429 was sprayed. Immediately 
thereafter, the resultant material was mixed with the other ingredients as 
given below to obtain the following formulations: 
______________________________________ 
3 C 
Example no. (parts) (parts) 
______________________________________ 
NTA-granules (1) 34.67 -- 
NTA-granules (2) -- 35.78 
Dehypon 2429 2.00 2.00 
Dequest 2047 0.25 0.25 
Perborate mono 7.00 7.00 
Caustic 47.75 47.75 
Norasol WL-2-Si 10.63 9.38 
______________________________________ 
In both cases, the resulting powder was compressed to 3 kg blocks (having a 
density of 1670 kg/m.sup.3) in a mould under a pressure of 12 kN/cm.sup.2 
using a double punch press. 
The blocks prepared by compressing the powder of Example 3 showed good 
quality and stability, whereas the blocks obtained from the powder of 
Example C showed lamination and were physically not stable. 
It can be concluded that, when applying NTA-granules with low moisture 
content, detergent blocks are obtained having significantly improved 
quality and stability.