This application is a divisional of commonly owned copending U.S. application Ser. No. 10/548,205 filed on Sep. 7, 2005, which is the national phase application under 35 USC §371 of PCT/FI2004/000147, filed Mar. 15, 2004 and claims the benefit of priority from FR 0303229, filed Mar. 17, 2003, the entire content of which is hereby incorporated by reference.
Those skilled in the art know the vulcanising and parchmentising operations so well that these processes will not be described more in detail hereinafter. The main thing is that the vulcanising is an operation consisting in treating a paper substrate by immersing it into a zinc chloride solution, and the parchmentising is a similar operation, in which the zinc chloride is replaced by sulphuric acid. The present invention does not relate to the actual vulcanising and parchmentising operations, but it relates to the manufacturing process of webs that can be treated with the operations of these two types.
The ability of a substrate to be treated by vulcanising or parchmentising depends mainly, if not exclusively, on the reactivity of the cellulose fibres making up the web with regard to the zinc chloride or sulphuric acid solutions. Thus, the more reactive i.e. accessible to chemical components contained in the ionic solutions the cellulose fibre is; the more satisfactory is the vulcanising or parchmentising. The reactivity of a fibrous web depends on several factors, one of which is especially the degree of polymerisation (DP) of the cellulose making up the fibre, the latter corresponding to the number of repetition units, which form the cellulose polymer. In generally, it looks like the weaker DP is, the more reactive is the fibre.
In the rest of the application, the efficiency of the vulcanising or of the parchmentising is controlled by evaluating the barrier level of the obtained vulcanised or parchmentised paper according to a technique, which will be made clear in the examples.
At the moment, the number of webs intended to ve vulcanised is manufactured from textile waste coming especially from the “Jeans industry”, the jeans consisting 100% of long cotton fibres (staple), the size of which is between 20 and 50 mm. In practice, the jeans manufacturing clippings or rags are in the form of a bale, which is then opened and the size of the rags is reduced by different operations such as cutting and shredding. When these different steps have come to an end, the shredded pieces of jeans are cooked in a solution of soda concentrated to 7% in a closed reactor, under pressure, at a temperature of about 150° C. Then follows the tiresome step, in which the cooked fibres are washed with water in order to eliminate all of the cooking liquor. All these necessary operations of this discontinuous process may lead to duration of about 24 hours.
Soda cooking step allows both opening of the cotton fibres and reducing the degree of polymerisation of the cellulose. In practice, when the cotton fibres making up the jeans have, before cooking, an average degree of polymerisation of about 2000, this degree is only about 600, as far as vulcanising and parchmentising are concerned, immediately after the cooking step. The value of 600 seems in fact sufficient for obtaining reactivity, and consequently a satisfactory ability of the base paper to vulcanising or parchmentising.
The clusters of cooked fibres are processed in an aqueous environment so as to separate the fibres from each other, after which the individual fibres are refined, i.e. their structure is subjected to a deformation by mechanical action, allowing optimising the accessibility of the fibre. The suspension of the individual cotton fibres obtained right after these steps is then deposited on the wire of the paper machine, in the presence, or not, of fibres having different kind or same kind of nature such as e.g. wood fibres, so as to form in a known manner a web, which is then drained and dried until the actual paper substrate is obtained.
As already said, it is necessary, before vulcanising or parchmentising, to set out the most reactive cellulose fibres into the paper, this reactivity being obtained by lowering strongly the degree of polymerisation of the cellulose fibres.
The cooking step allowing obtaining this result has, however, some inconveniences. At first, the capital costs of an industrial chemical reactor are relatively high. Subsequently, the cooking consumes a lot of chemicals, in the case in question, soda. Finally and above all, the cooking leads to the formation of coloured effluents of concentrated soda having a pH of 13.5, the elimination of which is especially difficult and polluting. These operations of cooking and washing the rags take place generally with a yield in the order of 85% meaning a loss of the raw material of about 15%.
In other words, the invention tends to solve the problem by developing a clean and economical high yield (over 85%) manufacturing process of paper substrates intended to be vulcanised or parchmentised, which would be at least as reactive with regard to the zinc chloride or sulphuric acid solutions as the substrates obtained by the processes using a chemical cooking step of the cellulose fibres with a high degree of polymerisation.
To do this, the Applicant had the idea of substituting the cooking step in the concentrated soda solution with an energy radiation step, this radiation step being able to be performed, either, in a dry state, directly on the cellulose fibres, before the individualisation of the fibres and the refining in the aqueous environment, or in a dry state, on the final paper.
In other words and in a first embodiment, the invention relates to a manufacturing process of a paper substrate intended to be vulcanised or parchmentised, comprising the steps of: subjecting, in a dry state, the cellulose fibres to energy radiation, separating and refining in an aqueous environment the radiation-treated fibres until a homogenous fibre dispersion is obtained, forming a web from the obtained fibre suspension, which is thereafter drained and dried to obtain the actual paper substrate. Full Patent Description - Patent Application ClaimsClick on the above for other options relating to this Manufacturing process of a paper substrate intended to be vulcanised or parchmentised patent application. ### Other recent patent applications listed under the agent Nixon & Vanderhye, Pc: How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Manufacturing process of a paper substrate intended to be vulcanised or parchmentised or other areas of interest.### Previous Patent Application:Method for altering the tack of materialsNext Patent Application:Refiner for refining pulpIndustry Class:Paper making and fiber liberation###
