Match head formulations

The present invention relates to match head formulations suitable for the production of safety matches and to matches when coated with the said formulations.

For many years match head formulations have contained chromium compounds, phosphorus sesquisulphide, sulphur and/or sulphur compounds and zinc oxide. These compounds are now widely recognised as having undesirable environmental properties both in relation to the manufacture of such formulations and in relation to their use and it is therefore an object of the present invention to provide a match head formulation in which these compounds are substantially absent.

One type of match in common use has a match head formulation which is ignited by an abrasive contact with any suitable roughened surface. These are referred to as `strike anywhere' matches. A second type of match in common use has a match head formulation which is ignited by an abrasive contact with a surface containing a formulation for initiating ignition of the match head. These are referred to as `safety matches'.

According to the present invention there is provided a match head formulation suitable for the production of safety matches containing potassium chlorate and red amorphous phosphorus, the balance comprising a binder, a thickener, a filler, and a foaming agent to the exclusion of sulphur, zinc oxide and dichromates, said formulation being dispersed in water forming a wet composition characterised in that the amount of red phosphorous is within the range 0.5 to 2.0 % by weight and when in the form of a wet composition the formulation has a density of approximately 1.15 g/cm³.

Preferably the proportion of potassium chlorate present is in the range from 40 to 60 percent dry weight while the amorphous phosphorus is present in proportions ranging from 0.5 to 2.0 percent dry weight - too little and the match is hesitant while too much and the match is able to be struck anywhere. Gelatine may provide a suitable binder if present in proportions ranging from 3 to 12 percent dry weight or alternatively the binder may be in the form of animal glue. The thickener is preferably a starch present in proportions of up to 5 percent dry weight while the foaming agent may be Arylan PWS an amine salt of an alkyl aryl sulphonic acid present in proportions of up to 0.2 percent dry weight. Felspar may be chosen as the filler. The formulation may also include an ash improver such as infusoria in proportions of up to 6 percent dry weight or a cellulose flour such as olivestone flour in proportions of up to 7 percent dry weight and a pigment such as iron oxide in proportions ranging from 3 to 10 percent dry weight. In formulations not containing iron oxide potassium hexacyanoferrate II or potassium hexacyanoferrate III may be included as a sensitizer and ash improver each in proportions of up to 7 percent dry weight.

Some examples of the present invention will now be described with reference to formulations suitable for the production of safety matches.

Safety Matches

In the past match head formulations suitable for the production of safety matches have contained chromium compounds, sulphur compounds and zinc oxide and in particular have contained potassium dichromate, sulphur powder and zinc oxide. In the first example all these are absent from the formulation and have been replaced by red amorphous phosphorus.

Example 1

A match head formulation suitable for the production of safety matches is prepared in which 54.18 percent dry weight of potassium chlorate is mixed with 4.06 percent dry weight of gelatine, 4.06 percent dry weight of starch, 20.32 percent dry weight of felspar, 2.71 percent dry weight of infusoria, 6.77 percent dry weight of iron oxide, 0.09 percent dry weight of Arylan PWS, and 6.77 percent dry weight of limestone ensuring good wetting and dispersion of all the ingredients before adding 1.03 percent dry weight of amorphous phosphorus as an aqueous slurry.

The water content of the above formulation may be in the range 40 to 55g per 100g of solids but is typically 48.8g /100g solids.

The density of the formulation when in the form of a wet composition may be in the range from 1.0 to 1.4 g/cm³ but is typically 1.15 g/cm³. This figure is lower than is usual for match head formulations of this type as a result of being more highly aerated and contributes towards an improved sensitivity and a faster drying rate.

It was found that the proportion of potassium chlorate present may range from 40 to 60 percent dry weight and the proportion of amorphous phosphorus may range from 0.5 to 2.0 percent dry weight for the formulation to maintain a satisfactory performance.

The gelatine is present as a binder. The binder content of the formulation is lower than is usual and consequently improves the sensitivity of the formulation as well as the drying rate. Gelatine may be present in proportions ranging from 3 to 12 percent dry weight without adversely affecting the sensitivity. In place of gelatine animal glue may provide a satisfactory binding agent.

Emcol Starch is present as a thickener to improve the head formation during drying and constitutes a major component of the binder system. In order to serve this function satisfactorily the starch may be present in proportions ranging from 0.5 to 5.0 percent dry weight.

Infusoria acts as an ash improver to prevent the head of the match from falling after use and may be present in proportions of up to 6 percent dry weight while Arylan PWS is a foaming agent which entrains air to control the thermal conductivity of the formulation and hence its sensitivity. Arylan PWS may be present in the formulation in proportions of up to 0.2 percent dry weight.

The presence of amorphous phosphorus makes it difficult to achieve clear bright colours but does not hinder the production of standard brown formulations. To this end iron oxide is used as a pigment and may be present in proportions ranging from 3 to 10 percent dry weight.

Limestone may be present in proportions ranging from 3 to 14 percent dry weight while felspar is used as a filler and serves to make up the balance of the formulation.

It is to be noted that the above formulation is free of potassium dichromate, sulphur and zinc oxide. The absence of sulphur from the formulation reduces the smell produced on striking a match coated with the formulation. The absence of potassium dichromate is advantageous because potassium dichromate is difficult to handle during manufacture.

The above formulation combines a satisfactory sensitivity and burn rate and has no propensity to produce burning fragments or dropping of hot ash. The formulation meets all the requirements of BS3795 and provides cost benefits over other existing formulations.

Example 2

In order to achieve a more brightly coloured match head formulation suitable for the production of safety matches and having properties similar to those described with reference to Example 1 above 55.52 percent dry weight of potassium chlorate is mixed with 4.16 percent dry weight gelatine, 4.16 percent dry weight of starch, 13.88 percent dry weight of felspar, 5.55 percent dry weight of infusoria, 0.09 percent dry weight of Arylan PWS, 6.94 percent dry weight of limestone, 6.94 percent dry weight of olivestone flour, up to 7.0 percent dry weight of a chosen pigment, and 1.39 percent dry weight of titanium dioxide ensuring good wetting and dispersion of all the ingredients before adding 1.05 percent dry weight of amorphous phosphorus as an aqueous slurry.

This formulation is similar to that described in Example 1 above and differs essentially only in that it may be more brightly coloured. Consequently the proportions of the chlorate, amorphous phosphorus, gelatine, starch, infusoria, Arylan PWS, limestone, and felspar may vary within substantially the same ranges as disclosed in Example 1. Of the constituents not found in that Example olivestone flour acts as an ash improver and may be present in proportions of up to 7 percent dry weight while titanium dioxide may also be present in proportions of up to 7 percent dry weight and acts as a masking agent. Olivestone flour may be substituted by other cellulose flours.

Potassium hexacyanoferrate II and potassium hexacyanoferrate III may be included in the above formulation each in proportions of up to 7 percent dry weight in order to provide a sensitizer system in place of a dichromate. Potassium hexacyanoferrate II and potassium hexacyanoferrate III also act as an ash improver.