Paper making and fiber liberation – Processes and products – Synthetic fiber
Patent
1984-12-19
1986-09-09
Chin, Peter
Paper making and fiber liberation
Processes and products
Synthetic fiber
162158, 162182, D21H 512
Patent
active
046107614
DESCRIPTION:
BRIEF SUMMARY
The invention is concerned with paper that contains chemically substituted cellulose. The paper in accordance with the invention has particularly good rot-proof and wet-strength properties. It can be used, e.g., as a raw-material for plant pot systems.
Rot-proof papers are used for a great number of purposes. In agriculture and forestry, they are used, e.g., as production material for plant pot systems.
The present-day production methods are based thereon that varying quantities of PVA fibres are mixed into the paper, by means of which fibres the desired strength against decomposition is obtained for the paper. A drawback of this method is the relatively high cost of the said fibres. It would be preferable to use such a rot-proof paper as is based exclusively on natural fibres.
By adding anti-rot agents to the paper, it is possible to provide a certain, but not sufficient, strength against decomposition. Possible toxic effects of anti-rot agents also restrict their more extensive use.
In the literature, there are several implications to the effect that by modifying the chemical structure of cellulose it is possible to provide prolonged strength against decomposition. For example, "Microbial decomposition of cellulose", Siu, R. G. H., Reinhold Publishing Corporation, New York (1951), gives a theoretical basis for this method. By substituting the hydrogen groups in the hydroxyl groups of cellulose with other groups, compounds of the formula
In order to obtain a sufficient strength against decomposition, it is necessary that the O-R linkage is as stable as possible, whereat the hydrolysis, if any, takes place very slowly.
In view of the strength properties of the paper, it is preferable that the reaction conditions are as mild as possible when these derivatives are being prepared.
Now it has been discovered that a paper that contains cellulose fibre chemically substituted with N-methylol compounds has an excellent strength against decomposition and wet strength. In this connection, the expression paper also means paperboard, board, and other, similar products.
Preferable N-methylol compounds that can be concerned are reaction products or urea, glyoxal, and formaldehyde, such as dimethylol-dihydroxy-ethylene-urea (DMDHEU), monomethylol-dihydroxy-ethyleneurea (MMDHEU), dihydroxy-ethyleneurea (DHEU), and acetylene-diureas. Also methylolated melamines and N-methylol-acryl-amide-copolymers can be used.
It has been noticed that all of the above compounds form stable linkages with cellulose. When cyclic N-methylol compounds are used, it is advantageous that a carbon atom placed as a neighbouring atom of a nitrogen atom has a nitrogen or oxygen atom as its neighbouring atom. This is the case, e.g., in the case of dimethylol-dihydroxy-ethyleneurea and of methylolated melamine.
The paper in accordance with the invention is preferably prepared by surface-treating conventional paper. When high temperatures or, in particular, a long reaction time is used, it is recommended to use surface treatment taking place in a unit separate from the paper machine. In principle, it is also possible to add the agents as early as in the size press of the paper machine and to perform mere condensing in a separate unit.
In order to produce the reaction, an elevated temperature and evaporation of the water generated in the reaction are required. N-methylol compounds additionally require a catalyst in order to react with cellulose. Latent or potential acids can function as a catalyst. A typical catalyst is MgCl.sub.2 ; an appropriate catalyst concentration is, e.g., 20 percent by weight as calculated from the reactive compound. The temperature may be, e.g., between 130.degree. C. and 200.degree. C., preferably between 140.degree. C. and 180.degree. C. The condensation time required depends on the temperature. If a strongly acid catalyst and a high temperature are used, a very short condensation time can be obtained.
By varying the concentrations of reactive agents in the solution or dispersion, it is, in a simple way, possible to adjust the
REFERENCES:
patent: 2407376 (1946-09-01), Maxwell
patent: 2624686 (1953-01-01), Kamlet
patent: 3773612 (1973-11-01), Avis
Eklund Dan
Erkkila Jukka
Ingman Matti
Lassus Anders
Peltonen Kauko
Chin Peter
Lannen Tehtaat Oy
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