GB2141965A - Moulding of detergent bars - Google Patents

Abstract

Built laundry bars for fabric washing are manufactured by forming the components into granules using a pan granulator, followed by extrusion of the granules in a screw extruder to form an extrudate which is cut into the bars.

Description

SPECIFICATION Manufacture of detergent bars Field of Invention: This invention relates to built detergent bars and in particular their manufacture. Built detergent bars are widely used for cleaning fabrics and other surfaces; they are required to have acceptable properties for the user and to be manufactured by an economic route.

Background of the invention: The method of manufacturing built bars is required to be economical both on plant and running costs, which include enegy charges, as well as satisfying the physical and chemical demands.

The method of the invention allows for efficient loss of heat and venting of gases in the intial mixing step of the method.

General description: The built detergent bars of the invention will contain detergent active in the range 5% to 50% and builder in the range 5% to 60%. The active may comprise alkyl benzene sulphonates (in which the alkyl group may be straight or branched), olefin sulphonates, primary alcohol sulphonates, alkane sulphonates, fatty acid ester sulphonates, alkyl sulphates, nonionic detergents, for example ethoxylated alcohol, ethoxylated fatty acids, ethoxylated phenols, soaps and mixtures of these actives.

The builder component will usually be condensed phosphates, i.e. sodium tripolyphosphate but may be pyrophosphate or orthophosphate. Sodium carbonate is another example of a builder which may be; in general there is no criticality in the material used as detergent builder.

Other conventional ingredients may be present, examples are lather controllers, fluorescers, silicates, pH controllers, e.g. sodium bicarbonate, and germicides. Water will usually be present in the bar from 5% to 25%.

In the method of the invention built detergent bars are manufactured by adding the components in powder or liquid form to a pan granulator to form granules, passing the granules through a screw extruder and cutting the extrudate to form bars. A pan granulator is open topped and rotated about an axis inclined to the vertical. The components tumble with rotation of the pan and aggregate to form particles, a liquid component may be sprayed in droplet form onto the tumbling bed to assist granulation. Any gas produced vents to the atmosphere and the large moving surface of particles provides good heat exchange characteristics. If the initial mixing includes neutralisation then about 80% of the neutralisation occurs in the pan.

Preferably the screw extruder has intermeshing twin screws so that a degree of mixing is achieved during extrusion at the intermeshing zone. If a single screw extruder is used it may be necessary to include a roll mill, for example a triple roll mill, between the granulation and extrusion stages.

The use of a pan granulator allows flexibility in formulation and the pan acts as a surge vessel, that is it stores increases in component flow and provides a regular supply of granulate to the subsequent stages.

The free-flowing particles provided by the granulator provide the mill, or plodder direct, with a steady stream of particles which require only a steady power input for processing. The dough provided by a sigma mixer can require peak power for processing somewhat above the average.

Thus the procedure of the invention requires a lower instalied power input.

Examples: The detergent bars of these Examples were prepared by first mixing the ingredients in a pan granulator, followed by passing the granulated mix through a triple roll mill and then plodding the milled mass through a conventional plodder.

The aluminium pan granulator was constructed with a flat bottom and a cylindrical cross section of 1/3 m diameter 0.1 2 m height. It was rotatable around its vertical axis while its axis could be kept at any angle between 30-60' to the horizontai (foundation base). The speed of the rotation was kept between 50 and 55 r.p.m. employing 1/4 HP gear drive. For the purpose of this experiment the vertical axis of the pan was kept at 30 to the horizontal plane. An arrangement to have a baffle stationary at one position was also provided.

A conventional triple roll mill (3.5" diameter, 6" wide, 2 HP drive) and a 3" diameter, 2 HP single screw plodder were employed for further processing the granulated mass to give the milled mass and the bar respectively.

Besides this basic equipment, for the preparation of the detergent bar, the powder dosing as well as the liquid dosing and spraying equipment employed to feed the granulating pan in this experiment was as follows.

An electromagnetic vibratory feeder dosed the powder from a conical hopper into the pan.

A low pressure double head metering pump was used for dosing the liquids. The liquids were sprayed into the pan using a compressed air actuated spray nozzle. A double pipe-stream heated-heat exchanger just before the spray nozzle raised the sulphonic acid temperature to 80"C, this facilitated its spraying.

Powder ingredients were sieved through 80 mesh BS sieve using 1 8" diameter vibratory screen and premixed before dosing in a ribbon mixer which acted as a simple mixing device.

Formulations for the Examples are given in Table I in % by weight.

Table I 1 2 3 Soda ash 5 7 6.8 Sodium tripolyphosphate 20 30 34 Talc 10 4.3 Dicalcium phosphate - 10 9.7 Trisodium orthophosphate dodecahydrate 12 6 5.8 Calcite - 13.7 5.2 Starch 12.7 - Sodium hexameta phosphate 1 - Titanium dioxide 0.3 0.3 0.3 Sodium carboxy methyl cellulose - - 1.0 Wax - - 1.9 Sodium linear (C12) alkyl benzene - 20 24.3 sulphonate Sodium dodecyl benzene sulphonate 25 - Dextrin 4 - Photine C 0.3 0.3 0.3 Phthalocyanine colour pigment 0.2 0.2 0.2 Water 6 6 8.1 Processing Two streams of liquids were used during pan granulation: (i) sulphonic acid, and (ii) alkali (sufficient to neutralise the sulphonic acid) in water together with photine C, colour and dextrin.

All other solid powder ingredients were sieved (- 30 mesh) weighed and mixed in the ribbon mixer.

In the actual operation, the pan was kept rotating, anti-clockwise; baffle was located at 5 o'clock position and the premixed powder ingredients were fed at a controlled rate (0.25 kg/ml) onto the baffle and the liquids were sprayed into the rotating pan at the controlled rate on the freshly incoming powder in the pan. As the mix was continuously granulated the granules overflowed and passed through the mill and then the milled flakes were passed through the plodder to give detergent bar, which was cut and the pieces were stamped, wrapped and packed in the usual way.

Example 4: The components were granulated as described previously then passed through a single screw extruder including a breaker plate (a multi-apertured plate) and die attachment. The pan granulated material had a bulk density of 0.75 g/cc, particle size below 3 mm diameter and was free-flowing. The production rate of the bars was higher compared to the use of a sigma mixer, milling and plodding. In the known method the sigma mixed dough blocked while being fed to the mill. The granulated mass from the pan granulator passed freely through the extruder to give a continuously extruded mass which was cut and packed.

Claims (2)

1. A method of manufacturing detergent bars containing from 5% to 50% by weight of detergent active and from 5% to 60% by weight of detergent builder comprising the steps of i) mixing the components in powder or liquid form in a pan granulator to provide granules, ii) passing the granules through a screw extruder, and iii) cutting the extrudate to form bars.

2. A method according to claim 1 wherein the screw extruder has intermeshing twin screws.