Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H25/00—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00
  • D21H25/18—After-treatment of paper not provided for in groups D21H17/00 - D21H23/00 of old paper as in books, documents, e.g. restoring

Definitions

• the present invention relates to microemulsions of water-in-oil (W/O) type and to their use in the treatment of paper products.
• W/O water-in-oil
• the present invention relates to W/O microemulsions containing alkali metal and alkaline earth metal salts, and to their use for deacidifying paper and paper products, such as books, drawings, paintings on paper and printings.
• Paper is known to undergo degradation over time. The most important factor among those factors which cause paper degradation is the acidity present in paper products.
• Such an acidity may have several origins, such as, for example:
• the acid-catalysed degradation process of paper products can be stopped by deacidification.
• the most widely used deacidification process is based on the precipitation of an alkaline buffer on the cellulosic fibres of paper (W.J. Barrow, Restoration methods; Society of American Archivists, Richmond, Virginia, Oct. 27, 1942).
• the sheets are soaked in a solution of calcium hydroxide, which neutralizes the acids present; residual calcium hydroxide is subsequently converted into carbonate by means of a bicarbonate solution.
• Carbonate deposited on paper supplies an alkaline reserve which, during a certain time period, neutralizes the acids coming from same paper and from surrounding environment.
• GB-A-2 180 248 discloses an expensive process for paper products preservation, in which a polymeric film is coated on paper sheets.
• U.S. patent 3 676 055 proposes a post-treatment for acidic books.
• the books are first dipped in a solution or suspension composed by alkali metal and alkaline earth metal oxides, and an organic solvent.
• a solution of alkyl oxides, or of a mixture of alkyl oxides under pression developed by a propellant (Freon 12) is used.
• Said process requires a very deep pre-drying because the reaction between water and diethilzinc is very fast; this pre-drying operation might cause damages to paper product.
• diethylzinc is explosive, and process safety conditions must be carefully controlled.
• Acid paper can be deacidified also in gas phase.
• Such a process is disclosed in U.S. patent 4 619 735, which uses amines, such as melamine derivatives. Unfortunately, this process makes it possible a low alkaline reserve to be obtained, and furthermore causes paper yellowing and displays toxicity risks.
• the purpose of the present invention is of overcoming the disadvantages of the processes known from the prior art and of supplying a low-cost product and process for deacidifying paper and paper products in bulk, which process renders such paper products resistant to the effect of acids present in paper and/or deriving from surrounding environment.
• microemulsion makes it possible an alkaline reserve to be deposited and consequently a protection of paper to be achieved, with a simpple, low-cost and environmentally compatible process, because only surfactants are used, which can be recovered at process end.
• Microemulsion means a dispersed system of oil-in-water or water-in-oil.
• Oil means a hydrophobic, water immiscible liquid.
• microemulsions are very stable, clear systems.
• the stability of microemulsions is obtained by using surfactants (and, possibly, co-surfactants) which form a stabilizer monolayer around dispersed water droplets.
• the subject-matter of the present invention is a microemulsion of water-in-oil type containing the following components:
• the subject-matter of the present invention is a microemulsion of water-in-oil, characterized in that its essential components are the following:
• the microemulsion possibly comprises from 1 to 20% by weight (based on surfactant) of an organic co-surfactant.
• Particularly preferred according to the present invention is a microemulsion containing 5-10% by weight of a 10 ⁇ 2 - 10 ⁇ 1 M aqueous solution of alkali metal and alkaline earth metal salts, 70-90% by weight of a hydrophobic solvent, 5-25% by weight of a surfactant.
• water is used in order to act as the vehicle for the alkalifying agent, therefore the amount of water used in the process is really kept at a minimum.
• the salts of alkali metals and alkaline earth metals used in the emulsion according to the present invention can be oxides, hydroxides, carbonates and bicarbonates of the metals of Groups I and II, as well as diborates (e.g.: Na2B4O7); all of them being water-soluble.
• Preferred compound are those containing Mg, Na, Ca; particularly preferred are non-toxicant compounds, such as magnesium ans sodium oxides, carbonates and bicarbonates, and calcium and magnesium hydroxides.
• the hydrophobic organic solvent used in the microemulsion according to the present invention has a boiling point comprised within the range of from 0°C to 160°C, preferably comprised within the range of from 50°C to 100°C.
• Exemplifying solvents are cyclohexane, n-heptane, n-hexane, isooctane.
• the preferred solvent is heptane.
• the surfactant present in the microemulsion according to the present invention is used in order to stabilize the small dispersed water droplets, reducing the interfacial tension of the system.
• ionic surfactants examples include AOT (sodium dioctylsulfosuccinate) and SDS (sodium laurylsulfate).
• a non-ionic surfactant When a non-ionic surfactant is used, the use of only one surfactant is enough. On the contrary, when a ionic surfactant is used, the use is sometimes required of a co-surfactant which decreases the density of surface charge generated by the ionic surfactant, reaching the interface and thus decreasing the interfacial tension. In that way, the co-surfactant makes it possible the dispersion of small water droplets to be achieved.
• An example of such a co-surfactant is a linear-chain aliphatic alcohol with 3-16 carbon atoms, in particular n-butanol, n-pentanol, n-hexanol.
• microemulsion according to the present invention obtained in that way is suitable for the treatment of acidic paper in order to decrease the acidity thereof, and considerably slow down its degradation over time and alteration of its mechanical properties.
• Another object of the present invention is a process for the treatment of paper products, charaterized in that said products are impregnated by dipping into the above disclosed microemulsion, and the surfactant is subsequently removed by washing with solvent and the products are dried.
• the impregnation of paper with the emulsion is carried out at room temperature (25°C).
• the weight ratio of microemulsion to paper is comprised within the range of from 1:1 to 50:1.
• the washing of the impregnated paper is carried out with a solvent, for example with an apolar solvent, such as n-heptane, or an alcohol, such as ethanol.
• a solvent for example with an apolar solvent, such as n-heptane, or an alcohol, such as ethanol.
• the resulting treated paper is dried at a temperature comprised within the range of from 0°C to 80°C, preferably comprised within the range of from 25°C to 60°C.
• the evaluation of the treatment is carried out by means of measurement of pH value and of alkaline reserve of paper.
• the W/O microemulsion is prepared by starting from an aqueous solution containing salts of alkali metals or alkaline earth metals, a hydrophobic solvent and a surfactant.
• the acidic paper is impregnated by being dipped into this microemulsion at room temperature.
• the ratio of microemulsion to paper, by weight, is comprised within the range of from 2:1 to 20:1.
• the process according to the present invention make it possible paper products, such as books (without that they have to be disassembled), drawings, paintings on paper, paintings, documents, and so forth, to be treated in bulk; the fast deposition of alkalifier agents on paper fibres, or fast deacidification of paper; and the removal of soil from paper.
• the process according to the present invention is suitable for deacidifying cellulose-based paper, as well as pulp-containing paper.
• the process according to the present invention is simple and cheap, because it does not require special equipment, and is environmentally compatible, because the reactants used can be recycled without releasing eco-toxic substances into the environment.
• a water-in-oil (W/O) microemulsion was prepared by simply mixing the following components: 77% of heptane, 15% of sodium dioctylsulfosuccinate, and 8% of an aqueous solution of sodium bicarbonate at 5% by weight.
• a sheet of pure cellulose Whatman paper with pH 5.7 was immersed in this microemulsion.
• the paper was soaked for one hour at room temperature (25°C).
• the ratio of microemulsion to paper, by weight, was 5:1.
• So treated paper was sussequently washed with ethanol, and then was dried inside an air-circulation oven at 50°C for 30 minutes.
• a water-in-oil (W/O) microemulsion was prepared by simply mixing the following components: 80,0% by weight of heptane, 11,5% by weight of sodium dioctylsulfosuccinate, and 8,5% by weight of an aqueous solution of magnesium bicarbonate at 4% by weight.
• a sheet of pure cellulose Whatman paper with pH 5.7 was immersed in this microemulsion.
• the paper was soaked for one hour at room temperature (25°C).
• the ratio of microemulsion to paper, by weight, was 5:1.
• So treated paper was subsequently washed with ethanol and then was dried inside an air-circulation oven at 50°C for 30 minutes.
• a water-in-oil (W/O) microemulsion was prepared by simply mixing the following components: 80 % of heptane, 11,5% of sodium dioctylsulfosuccinate, and 8,5% of an aqueous solution of magnesium bicarbonate at 4% by weight.
• So treated paper was subsequently washed with ethanol and then was dried inside an air-circulation oven at 50°C for 30 minutes.
• the resulting paper was exposed to those conditions which are known to cause an accelerated paper ageing. Therefore, paper was kept stored inside an oven at 90°C with a relative humidity of 50%.
• a water-in-oil (W/O) microemulsion was prepared by simply mixing the following components: 80 % of heptane, 11,5% of sodium dioctylsulfosuccinate, and 8,5% of an aqueous solution of magnesium hydrogen carbonate at 4% by weight
• a book (tied paper sheets having a pH value of 5.1) was dipped into this microemulsion. The book was soaked for one hour at room temperature (25°C). The ratio of microemulsion to book, by weight, was 2:1.
• the so treated book was subsequently washed with ethanol and then was air-dried, at room temperature.
• the treated books had a pH value of 7.2.
• a water-in-oil (W/O) microemulsion was prepared by simply mixing the following components: 67,5% of heptane, 22,5% of LIALET 125/2 (R) (a mixture of diethoxylated C12OH and C15OH), 10,0% of an aqueous solution of magnesium bicarbonate at 4% by weight.
• a sheet of pure cellulose Whatman paper with pH 5.7 was immersed in this microemulsion.
• the paper was soaked for one hour at room temperature (25°C).
• the ratio of microemulsion to paper, by weight, was 5:1.
• So treated paper was subsequently washed with ethanol and then was dried inside an air-circulation oven at 50°C for 30 minutes.

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Citations (2)

• 1991
  • 1991-11-20 IT ITMI913102A patent/IT1252006B/it active IP Right Grant
• 1992
  • 1992-11-18 JP JP4309053A patent/JPH0615161A/ja active Pending
  • 1992-11-19 EP EP92119718A patent/EP0543372A1/en not_active Withdrawn
  • 1992-11-20 CA CA002083460A patent/CA2083460A1/en not_active Abandoned

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