GB2098975A - Improvements in the manufacture of so-called safety matches - Google Patents

Abstract

Safety matches consisting of a match-stick of wood or impregnated cardboard provided with an inflammable tip, characterised in that the said tip is made from a paste containing: -gelling agents consisting, in a manner known per se, of gelatin glue, sulphur, chlorate and conventional fillers; -emulsified oils such as, in particular, boiled linseed oil, liquid paraffin or paraffin; and -small hollow spheres prepared from a thermoplastic copolymer. e

Description

SPECIFICATION Improvements in the manufacture of safety matches The present invention relates to improvements in the manufacture of so-called "safety" matches, and is aimed more especially at a new type of match intended for countries in tropical regions.

It is known that safety matches comprise a tip designed so as to ignite when struck on a surface formed by the matchbox covered on at least one of its two sides with a "friction surface" consisting of a substance containing amorphous phosphorus. These matches have in particular the following advantages: all types of wood can be used to make the matchstick, in particular wood available in the country of origin, simple and cheap products are used, such matches are economical on account of the substantial reduction in the consumption of raw materials and, finally, they can be made and used in regions of very high humidity.

At the present time the match-tip is made from a paste traditionally consisting of a mixture comprising, in particular: a combustive, combustibles, fillers, catalysts, dyes, and a glue of animal origin.

this latter component ensures the bonding of all the constituents and causes them to adhere, when dry, to the support consisting of a wooden or cardboard matchstick.

The gelatin glue extracted from bones or skins and constituting the binder for the components of the tip is characterised by a very high hygroscopicity due to the presence of large amounts of hydroxyl groups and free carboxyl groups. This characteristic confers a very low humidity resistance on the match, which is undesirable for use in countries having a very high degree of humidity. Moreover, the manufacture of matches involving such an animal glue presents problems during the last stages of chemical treatment, corresponding to the hardening of the tip and the evaporation of water, given the ambient manufacturing conditions, which are characterised by a high temperature, of the order of 30 to 350C, and a high humidity, of the order of 60 to 95%.

Numerous attempts have been made to remedy these disadvantages.

Covering the surface of the head of the match with water-impermeable coatings was first of all considered. A.M. Vaseva and M.L. Lakshevich, Chemical Abstract 62, 6333b (1965), describe the use of a mixture of glue and potassium chlorate. Waxes, paraffins or synthetic resins have also been considered for use for the same purpose. Finally, matches covered with a nitrocellulose lacquer have been produced for the army (see in particular Kirk-Othmer, Encyclopaedia Technical Chemistry, Vol. 1 3, p. 164). This process is still used for production purposes of a very limited and publicity nature. This known solution has the double disadvantage that it is complicated to implement on a large scale, and above all gives a product of only mediocre sensitivity, which means that this solution can only be used for very special cases.

Another solution consists of replacing at least part of the gelatin glue by a substitute. To this end, French Patent Specification No. 1 515 152 proposes an insolubilising resin that can be used in aqueous media, of the urea-formaldehyde or melamine-formaldehyde type, combined with cellulose derivatives, e.g. ethyl cellulose, hydroxyethyl cellulose, and hydroxypropylmethyl cellulose. It has also been suggested for the same purpose to use, as binder, synthetic resins insoluble in water but soluble in alcohol or acetone, e.g. cellulose phenolformaldehyde acetate (see UK Patent Specification No. 414 938). This involves a solution that is difficult to use and which requires large modifications to the material (paraffining).These solutions, or similar solutions do not always give the expected results, and they present difficulties in use on account of certain shelf life criteria that are incompatible with the demands of industrial production.

It has also been proposed to incorporate polymerisable products leading to copolymers. Thus, US Patent Specification No. 3 31 4 904 discloses the use of methacrylic acid esters and glycerol chlorhydrin, and US Patent Specification No. 3 441 456 recommends for this purpose a copolymer of methyl vinyl ether and maleic anhydride. It has also been suggested to use methyl, ethyl or butyl acrylates or methacrylates in the presence of catalysts (see in particular EDA, KENICHI, Chemical Abstracts 75, 152 504 d, 1971). These various formulations should be used with care and in limited amounts since they have an effect on the shelf life of the match paste that is detrimental to their use on the production materials.Moreover, the combustion and cohesion of the tip tend to deteriorate, and in any case the same percentages, mixed with the other constituents of the paste, do not have a sufficiently decisive effect as regards moisture resistance.

For their part, the present Applicants, in order to solve this problem, first of all examined combinations offering a high calorific power. In their French Patents Nos. 1 523 349, 69 22 307 and 73 25 548, the Applicants have described pastes for match-tips containing high levels of potassium chlorate and a dispersed polymerisable resin. The combustion and the transmission of the flame from the tip to the matchstick was thus able to be improved; however, the cohesion of the tip is not perfect during the striking of the match on the friction surface.

This invention therefore proposes to provide a solution which does not have the disadvantages of the prior art solutions described above.

The invention concerns safety matches consisting of a small stick of wood or impregnated cardboard provided with an inflammable tip, characterised in that the said tip is made from a paste composed of gelling agents consisting, in a manner known per se, of gelatin glue, sulphur, chlorate, and conventional fillers; emulsified oils, such as in particular boiled linseed oil, liquid paraffin or paraffin; and 'small hollow spheres prepared from a thermoplastic copolymer.

The incorporation of oils according to the invention effectively prevents the absorption of moisture.

It is in fact possible to add to the match paste sufficient amounts of oil to form a moisture barrier without having any disadvantageous effect on the duration of use of the production materials and on combustion, as is the case when using the cross-linking agents employed in the techniques described above. At the same time, the invention provides means enabling the density of the match paste, i.e. the structure of the tip, to be adjusted. These means consist of introducing small hollow spheres made from a thermoplastic copolymer. A structure more homogeneous than that obtained by the conventional methods is thus conferred on the tip. Moreover, this procedure enables very low densities to be obtained and thus enables a substantial saving to be made in the raw materials employed.

According to one feature of this invention, the oil used is mixed with a compound having a high emulsifying power, such as for example oleic acid (olein), norpholine or stearic acid (stearin). The proportion of oil emulsion used in the match paste may be of the order of 3 to 25% by weight with respect to the total weight of the dry products used, depending on the type of oil and emulsifying compound used.

According to the invention, the small hollow spheres are added to the paste in an amount of 0.5 to 2% by weight of the total weight of the dry products used, and their diameter is of the order of 10 to 1008.

Before describing the process for making a match paste according to the invention, this preparation as carried out at the present time will be briefly described.

A glue stock consisting of water and glue of animal origin (collagen) is generally prepared. It is preferred to use a mixture, so as to obtain the best results during the treatment enabling a blob of paste to be deposited on the match support (this procedure is generally termed "chemicalisation") S determining, in particular, the shape and cohesion of the blob. The glue stock is heated to a temperature 15 to 250C above the melting point of the gel. The glue stock and the following additives are next added to a mixer: triturated sulphur (3 to 6%), chlorate (45 to 55%), and fillers (1 to 3% diatomaceous earths, and 10 to 20% glass powder, silica, sand or quartz, having a grain size below 100 y). Zinc oxide (1 to 3%), potassium bichromate (1 to 2%), and a soluble colourant or pigment to provide the desired colour are also added.The gelatin glue represents in general 8 to 1 5%. The percentages given above are calculated with respect to the weight of dry products. Mica and Kaolin in the form of a very fine powder may also be added. In order to improve the fineness of the mixture, grinding may be carried out, for example in a disc mill. The amount of water is adjusted according to the required viscosity for the "chemicalisation" or soaking operation.

The process for preparing a match paste according to the present invention includes the main stages of the known process as described above, but modified and supplemented in the following manner: 1 - the proportions of the base constituents included in the composition of the paste mixture are modified so as to adjust these base data in order to make best use of them having regard to the regions where the matches are produced and sold (hot and humid countries); 2-an additional stage is provided for the incorporation of oil emulsions in the gelatin glue in order to obtain the glue stock; 3 - an extra additional stage is provided for the incorporation of the small hollow spheres into the match paste, so as to alleviate the disadantages resulting from this incorporation.

The invention employs a mixture of base constituents having the following modified composition: - chlorate: 50 to 60%, preferably more than 55%; -triturated sulphur: between 6 and 7; - addition of products of the colophony type or derivatives obtained from the distillation of pine wood: 1 to 3%; fillers, such as in particular diatomaceous earths: 1 to 3%; - glass powder, silicon, sand or quartz: 10 to 20%.

These fillers may in addition contain asbestos, mica or kaolin.

In addition to ensuring a well balanced combustion, suitably chosen proportions of these constituents enables a homogeneous ash having a sufficiently high softening point to be obtained.

Finally, dyes or pigments may be added so as to obtain the desired colour of the match tip; if a brown paste is desired, a mixture of 0.2 to 0.7% of carbon black and 1 to 4% of iron oxide is used. As regards the latter constituent, it is not essential to choose the best quality; in fact, the impurities consist of silica and alumina, which do not affect the combustion of the match-tip.

In order to bind the above constituents, a small amount of gelatin glue (approximately 6.5 to 8.5%) in combination with 0 to 4% of a synthetic resin consisting of an aqueous dispersion of an acrylate copolymer are used according to the invention. This resin is not absolutely essential, though it reinforces the cohesion of the matchtip. 0.7 to 3% of zinc oxide is added. Finally, it is preferred to add a high viscosity cellulose derivative, such as preferably a carboxymethyl cellulose or, possibly, a hydroxyethyl cellulose in an amount of between 0.2 and 0.7%, so as to be able to correct and adjust the viscosity of the paste at the same time as the amount of water.

An emulsified oil, such as linseed oil, paraffin, paraffin oil or liquid paraffin, mixed with a compound having a high emulsifying power, e.g. oleic acid, morpholine or stearic acid, is added to the mixture having the composition specified above. The following table gives some non-limiting examples of compounds that may be used according to this invention.In the table, the parts are parts by weight.

(1) (2) (3) (4) (5) Paraffin or paraffin oil - 10-50 20-100 20-100 Linseed oil 20-100 10-50 - - 900 Stearic acid - - - 10-30 Oleic acid 8-40 10-40 10-40 - 80 Morpholine 2-12 3-12 3-12 3-12 20 Water 1000 1000 1000 1000 1000

The linseed oil emulsion is prepared cold, whereas the paraffin emulsion is prepared hot (60 ).

A badly prepared emulsion leads to the formation of lumps. The homogeneity of the mixture is no longer guaranteed, which means that the matchhead has a poor appearance and the desired results aimed at by the invention are not obtained. This is especially true for paraffin, which is a very difficult substance to use. In order to avoid this disadvantage, all the constituents are poured into a mixer having a powerful stirrer of sufficient specifications and speed (of the order of 1 500 revsiminute). As long as the emulsion is well stirred, it may be kept for 24 to 48 hours without deteriorating. In cases where it is found that the emulsion has settled out slightly, it is sufficient before use in making the match paste to remix the remaining fractions.

As regards choosing the types of oils incorporated as an emulsion in the match paste, the following factors will be taken into account: - the paraffin chosen will be of a type having a high melting point; - the paraffin oil should be a carefully refined oil; - the boiled linseed oil, treated with magnesium salts, is more siccative and should be selected in preference to the other types.

The proportion of oil emulsion used in the match paste may be 1 5 to 25% by weight of the total weight of the dry products constituting the formulation, as regards the formulations (1), (2), (3) and (4) in the table above, and 3 to 7% in the case of formulation (5), linseed oil enabling more concentrated solutions to be prepared. According to the invention, the proportions indicated above are higher the more adverse the climatic conditions and the more marked the variations in the latter.

As has been indicated above, the incorporation of these oils is reflected in particular by a very large increase in the density of the paste, and by a reduction in the sensitivity of the match when the match-tip is struck on the friction surface.

In general, a paste prepared in humid climates should meet a precise density criterion. In fact, the paste is emulsified by virtue of the foaming ability of the gelatin glue. This enables the paste, when dry, to contain microscopic air inclusions, which facilitate and regulate the combustion of the match-tip. At the end of the preparation stage the paste should have a density of 1.2 + 0.5 g/cm3. It has been found that the introduction of oil emulsions produces a marked increase in the density to 1.6 g/cm3. This is the reason why the invention provides for the incorporation in the paste of small hollow spheres having a diameter of the order of 10 to 100 y. The small spheres are prepared from a thermoplastic copolymer, e.g. vinylidene chloride/acrylonitrile.The small spheres are used in general in combination with unsaturated polyester resins so as to reduce the density of the resin. It is possible to carry out the expansion immediately before preparing the paste, in a supplementary operation.

An addition of the order of 0.5 to 2% of these small spheres is sufficient to adjust the density of the paste to a value of 1.20 to 1.0 g/cm3. 35 to 60% of the weight of the raw materials consumed may thus be saved. Moreover, experience shows that the cohesion of the match tip is not adversely affected by using a paste having a density of 1.00 g/cm3, which is not the case with a conventional formulation.

This advantage is due to the fact that the small hollow spheres combined with the glue themselves form a coherent structure, which is not the case with the air inclusions present in a conventional paste.

Higher concentrations, giving a density of the order of 1.00 g/cm3, may thus be used without any fear.

In order to correct the loss in sensitivity of the match when it is struck, due to the presence of the oil emulsions, the concentrations of potassium bichromate and manganese dioxide are adjusted according to the invention so that they are of the order of 1 to 2% and 1 to 4% respectively. If this measure proves to be insufficient, it may be completed by a UV treatment. In fact, it has been found that a high level of potassium bichromate, combined with the action of a UV lamp during the drying of the matchheads, enables a very good sensitivity to be obtained.

The process for preparing the match paste according to the invention, and comprising the constituents specified above, is carried out in the following manner: The starting point is one of the oil emulsion formulations specified in the table above, which serves as the basis of the glue stock: Emulsion (1), (2), (3), (4) or (5) + gelatin glue + water (adjusted as necessary).

The water + oil emulsion mixture is very vigorously stirred and the gelatin glue is added progressively during this operation, care being taken to ensure that this addition does not take more than 1 5 to 30 seconds. After the mixture has swelled under the effect of the absorption of water by the gelatin, the resultant gel is heated to a temperature of the order of 40-450C so as to obtain the glue stock. The latter is ready after about 30 to 40 minutes.

This glue stock is then added to a mixer, together with the following dry products correctly homogenised and in the proportions specified above; triturated sulphur, potassium chlorate, fillers, oxides, dyes, remainder of the gelatin, aqueous dispersion of an acrylate copolymer, etc. Mixing is carried out for a time which does not exceed 30 minutes and which is a function of the material employed. The latter should be chosen so as to permit an intimate mixing of all the paste constituents, or to permit rolling so as to reduce all lumps, which are unacceptable in match-tips. To this end, one or more items of equipment satisfying one and/or the other of these functions may be used.

In the case of the emulsion (5), the glue stock is first of all prepared and the emulsion is then added to the latter.

According to the invention, the small hollow spheres added to the mixture may either be added to the glue stock or at the same time as the dry products.

Before adding the paste thus obtained to the machine for "chemicalising" the match-heads, it is absolutely essential that the paste satisfies the requirements as regards temperature (40--450C in hot and humid climates), viscosity (function of the chemicalising materials used), and density (1.00 g/cm3).

The following examples, which are not intended to be of a limiting nature, illustrate some embodiments of the invention.

EXAMPLE 1 This example involves a small proportion of gelatin glue. The figures express percentages with respect to the dry products.

Linseed oil emulsion (5): linseed oil 3.0 gelatin 7.3 potassium chlorate 58.0 sulphur 6.7 acrylate copolymer (dry) 3.0 colophony or colophony derivatives 1.3 silica 8.3 mica 4.3 diatomaceous earth 1.0 zinc oxide 1.0 carbon black 0.3 iron oxide - 1.3 manganese dioxide 1.7 potassium bichromate 1.7 carboxymethyl cellulose 0.3 small hollow spheres 0.8 100.0 water 36.7 water emulsion 3.3 EXAMPLE 2 The formulation given in Example 1 may be found to be too active, and it is possible to moderate the combustion.

Linseed oil emulsion (5): boiled linseed oil 3.0 gelatin 8.5 potassium chlorate 57.0 Linseed oil emulsion (5): - Continued sulphur 6.3 colophony and derivatives thereof 1.0 silica 8.3 mica 4.3 kaolin 3.0 diatomaceous earth 1.5 zinc oxide 1.0 carbon black 0.3 iron oxide 1.3 manganese dioxide 1.7 potassium bichromate 1.7 carboxymethyl cellulose 0.3 small hollow spheres 0.8 100.0 water 36.7 water emulsion 3.3 EXAMPLE3 This formulation is used for operating under less adverse conditions.

Linseed oil emulsion (5): boiled linseed oil 1.5 gelatin 8.0 potassium chlorate 57.0 sulphur 6.5 acrylate copolymer (dry) 1.9 colophony and derivatives thereof 1.7 silica 8.3 mica 4.0 kaolin 3.0 diatomaceous earth 1.0 zinc oxide 1.0 carbon black 0.3 iron oxide 1.3 manganese dioxide 1.7 Linseed oil emulsion (5): - Continued potassium bichromate 1.7 carboxymethyl cellulose 0.3 small hollow spheres 0.8 100.0 water 38.3 water emulsion 1.7 In these first three cases, the emulsion is added to the glue stock.

EXAMPLE 4 The use of paraffin involves a special feature. The emulsion is of a different formulation, requiring a different operational method. In fact, the emulsion will serve as a base in the preparation of the glue stock.

Paraffin emulsion paraffin 3.0 gelatin 7.3 potassium chlorate 58.0 sulphur 6.3 acrylate copolymers (dry) 2.4 colophony or derivatives thereof 2.3 silica 8.3 mica 4.3 diatomaceous earth 1.0 zinc oxide 1.0 carbon black 0.3 iron oxide 1.3 manganese dioxide 1.7 potassium bichromate 1.7 carboxymethyl cellulose 0.3 small hollow spheres 0.8 100.0 water 33.3 water emulsion 6.7 EXAMPLE 5 Use of a paraffin emulsion under less adverse conditions.

Paraffin emulsion: paraffin 1.5 gelatin 8.0 potassium chlorate 57.0 sulphur 6.5 acrylate copolymers (dry) 1.9 colophony or derivatives thereof 1.7 silica 8.3 mica 4.0 kaolin 3.0 diatomaceous earth 1.0 zinc oxide 1.0 carbon black 0.3 iron oxide 1.3 manganese dioxide 1.7 potassium bichromate 1.7 carboxymethyl cellulose 0.3 small hollow spheres 0.8 100.0 water 33.3 water emulsion 6.7 The methods of operation are in accordance with those disclosed in the preceding description, and three phases in particular are involved: mixing, grinding and homogenisation.

It follows from the above description that the invention provides improvements in the manufacture of safety matches, which are characterised in particular by the following advantages: - a much greater degree of regularity of the characteristics of the match paste during its preparation, and the ability to use this paste under difficult conditions, namely widely varying ambient humidity of between 50 and 100% (subtropical and equatorial regions) and temperatures of 25 to 400, thanks to a modification in the basic formulation; - a shelf life ("pot life") compatible with the demands of industrial production, thanks to the incorporation of oil emulsions which, when dry, form the necessary barrier to prevent the absorption of moisture during storage, and use of the paste in adverse atmospheric conditions;; - improvement in combustion, sensitivity and mechanical strength of the match-tip, obtained thanks to the very great adjustments to the density (1.2-1.0 instead of 1.6), by incorporating small hollow spheres and suitably regulating the levels of potassium bichromate and manganese dioxide; - large savings in raw materials, amounting up to 20%, resulting from the unusually low values of the density of the paste due to the incorporation of the small spheres, which guarantee a reinforcement of the structure of the match tip; - a perfect adherence of the ingredients, irrespective of the type of wood used to make the match- sticks, in particular all the tropical varieties of trees satisfying the physical characteristics appropriate to the manufacture of matches.

To summarise, the addition to the match paste of oil emulsions and small hollow spheres enables stable matches to be produced in a simple manner, while preserving all their properties during use in hot and humid climates. Moreover, the resultant matches are economically produced, given that they require simple and inexpensive products, and that the process according to the invention enables, as has been seen, substantial savings to be made in the consumption of the raw materials.

It should of course be understood that this invention is not restricted to the various examples of embodiments given in the preceding description, but in fact covers all possible variations.

Claims (11)

1. Safety matches consisting of a match-stick of wood or impregnated cardboard provided with an inflammable tip, characterised in that the said match-tip is made from a paste containing: - gelling agents consisting, in a manner known per se, of gelatin glue, sulphur, chlorate and conventional fillers; - emulsified oils such as, in particular, boiled linseed oil, liquid paraffin or paraffin; and - small hollow spheres prepared from a thermoplastic copolymer.

2. Safety matches according to claim 1 , characterised in that a compound having a high emulsifying power, such as in particular oleic acid, morpholine or stearic acid, is added to the oil used in the paste mixture.

3. Safety matches according to one of claims 1 and 2, characterised in that the proportion of oil emulsion used in the match paste is of the order of 1 5 to 25% by weight of the total weight of the dry products constituting the emulsion in the case of paraffin oil, liquid paraffin or paraffin, and 3 to 7% in the case of linseed oil, these amounts being selected higher the more adverse the climatic conditions and the more marked the variations thereof.

4. Safety matches according to any one of claims 1 to 3, characterised in that the thermoplastic copolymer from which the said small spheres are prepared is a vinylidene chloride/acrylonitrile copolymer, preferably used in combination with unsaturated polyester type resins.

5. Safety matches according to any one of claims 1 to 4, characterised in that the small spheres are incorporated in the paste in an amount of 0.5 to 2% by weight with respect to the dry products.

6. Safety matches according to any one of the preceding claims, characterised in that the diameter of the small spheres is of the order of 10 to 1 00 FL.

7. Safety matches according to any one of the preceding claims, characterised in that the proportion of gelatin glue in the paste is of the order of 6.5 to 8.5% by weight with respect to the dry products.

8. Safety matches according to claim 7, characterised in that the gelatin glue is used in combination with a synthetic resin consisting of an aqueous dispersion of an acrylate copolymer, in a proportion of O to 4%.

9. Safety matches according to any one of the preceding claims, characterised in that the basic constituents of the paste incorporated in the gelatin glue comprise, in particular: - 50 to 60% of chlorate, preferably more than 55%; - 6 to 7% of triturated sulphur; - 1 to 3% of products of the colophony type, or derivatives obtained from the distillation of pine wood; - fillers, consisting of 1 to 3% of diatomaceous earths, and

10 to 20% of glass powder, silica, sand or quartz, or possibly mica, kaolin or asbestos; - dyes; - 0.7 to 3% of zinc oxide; - 0.2 to 0.7% of a high viscosity cellulose derivative, such as a carboxymethyl cellulose or a hydroxyethyl cellulose; - 1 to 2% of potassium bichromate; and - 1 to 4% of manganese dioxide.

TO. Process for manufacturing safety matches according to any one of the preceding claims, characterised by the following successive steps: - the mixture of water and chosen oil emulsion is poured into the tank of a mixer provided with a powerful stirrer,in such a way as to produce a vigorous stirring action; - the gelatin glue is added progressively to the tank of the mixer during stirring, the addition lasting 1 5 to 30 seconds; - after expansion of the mixture under the action of the absorption of water by the gelatin, the gel is heated at 40-450C for about 30 to 40 minutes to obtain the glue stock;; - the glue stock is next added to a mixer, followed by the correctly homogenised dry products, and the whole is mixed for a period not exceeding 10 minutes, the small hollow spheres being added either to the glue stock or at the same time as the dry products.

11. Process according to claim 10, characterised in that the linseed oil emulsion is prepared cold, whereas the paraffin emulsion is prepared hot, at a temperature of the order of 60"C.

1 2. Process according to one of claims 10 and 11, characterised in that in order to correct the loss of sensitivity of the match resulting from the presence of the oil emulsion, the control of the amounts of potassium bichromate and manganese dioxide, of the order of 1 to 2% and 1 to 4% respectively, is completed by a UV treatment during the drying of the match-head.