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
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/03—Non-macromolecular organic compounds
  • D21H17/05—Non-macromolecular organic compounds containing elements other than carbon and hydrogen only
  • D21H17/06—Alcohols; Phenols; Ethers; Aldehydes; Ketones; Acetals; Ketals

Definitions

• the dimensional. instability of paper is mainly caused by the swelling and shrinking of the cellulose fibres at varying humidities. However, as it seems that wet paper shows. a greater dimensional increase than is possible'as a result offibre swelling alone, it is also probable that some fibre separation occurs due to the breaking of interfibre bonds. Furthermore, contact with moisture produces a relaxation of stresses present in dry paper, and such relaxation also results in changes of volume. The dimensional changes of paper are, therefore, not simply reversible, and, when paper is exposed to varying atmospheric conditions with the same humidity at the beginning and at the end of the cycle, the dimensions ofthe paper are usually not the same. mensionalchanges is also dependent on the degree of beating of the'cellulose pulp used and on the manufacturing conditions of the paper. I
• the present invention which-provides a method or the treatment of paper and cardboard consisting essentially of natural and/or regenerated cellulose fibres and possessing a high wet strength and a substantial dimensional stability While retaining or even improving its mechanical properties in the dry state, which comprises impregnating paper or card-' board consisting essentially of natural and/ or regenerated cellulose fibres, with a liquid composition containing formaldehyde, a halogen-containing acid, water, and a water- It is known that paper The amount of the dimiscible solvent. Although hydrobromic acid has proved to give the highest wet strength, hydrochloric acid is the.
• acetic acid is preferred as a cheap and suitable medium.
• the method of treatment according to the present invention is very simple and easy to perform.
• the optimum period of immersion depends on the cencentration of the reagentsand on the temperature of the bath, which is usually kept between 20 and 40 C.
• the paper need not remain in the bath during the whole time of the reaction. pregnate the material thoroughly for a few seconds, to squeeze out the superfluous liquid, and to keep the paper wetted with the liquid as long as required before wash ing.
• the process can be carried out discontinuously or it may be carried out in a continuous manner by feeding paper from a supply roll through the impregnating bath, taking it up again on a further roll, keeping the rolls soaked during the prescribed time,
• paper treated according to the present invention not only acquires a high wet strength and a very good dimensional stability, but also acquires an increased dry strength and a considerably higher folding endurance, while its elongation at break'is practically no change of its elongation at break.
• the stabilised I paper is exposed to a humidity change from to 100% and again to 65%, the improvement in dimensional stability as compared with untreated paper is 90% in the machine direction and over in the cross-machine direction.
• the improvement in dimensional stability in the cross-machine direction even reached 94%.
• paper of a'finefibre structure is especially sensitive to humidity changes.
• paper made from a cellulose pulp beaten during'90 minutes and treated according to the present invention still has a wet breaking length of over 2000- metres and an improved dimensional stability of 55% as compared with an untreated sample.
• the increase of the folding endurance of paper stabilised with a liquid formaldehyde composition according to the invention is usually more than twice that of an Patented Jan. 18, 1966 It is sufficient to im untreated sample. This is in sharp contrast to the above mentioned stabilisation method using formaldehyde in the vapour phase with subsequent heating, which causes the folding endurance of the paper to drop considerably.
• Example 11 Three different kinds of paper leaves each having a weight of 100 g./m. are made from bleached sulphate cellulose fibres, the first one from unbeaten material and the second and third leaf from cellulose beaten in a Valley beater with a lbs. load during 30 and 90 minutes respectively. From all three kinds of leaves samples are left untreated, while other samples are stabilised with a liquid formaldehyde composition in the manner described conditions with liquifi compositions cqntaining 10 and 10 in Example I.
• the first composition contains 1% generated cellulose fibres and having a Weight of 45 a of hydrobromic acid
• the third composition 1% of perchlo position having a temperature of 28 C. and nta g ric acid.
• a fourth composition serving as control is made of formaldehyde, of hydrochloric acid, 88.5% without an additional acid and contains instead 1% more of acetic acid, and 7.5% of Water.
• the testing es s for P p stabilised in this squeezed out and left impregnated with their respective manner and for an untreated control sample ar Sh Wn liquid composition during 30 minutes at room temperain the following table: ture, When they are washed with faintly alkaline water.
• the following table shows the wet strength of the four Percent Dimen- P p leaves: Breaking length sional change after (m) Elonga- 65%,100%, 65% Bredklng length Paper 253;?
• Example IV Thus the stabilised paper possesses a dry strength increased by 40%, a wet strength increased 15 times, and Porous P p leaves made from equal Parts Of ⁇ latllrai an improvement I in dimensional stability of 90% in the and regenerate? cellulose fibfes and hflvmg Weight of machine direction and of 70% in the cross-machine dii 8- immersed dul'lng 3o.mlnllies 111 diifefent rection, as compared with untreated papen liquid compositions all of them hav1ng a temperature of Exposure of the same paper to another humidity cycle C and eafih cfmialnlng 23% of formaldehyde, gives the following results; ofhydrochloric acid, between 55.8% and 88.3% of acetic acid, and between 7.5 and 40% of water. The paper Percent Dimensionalchange leaves are then washed with faintly alkaline water and after 90%, 65%, 10%, dried at 120 C. The testing results of the leaves are
• the leaves are squeezed out and kept impregnated at room temperature for different periods, when they are washed with faintly alkaline water and dried at 120 C.
• the following table shows the wet strength and folding endurance of the leaves in relation to the period of impregnation and in comparison with an untreated control leaf:
• a process for dimensionally stabilizing a paper product consisting essentially of cellulosic fibers selected from the class consisting of natural and regenerated cellulose comprising impregnating the paper product with a liquid composition which comprises, in weight percent, 15% formaldehyde, 15% of a halogen-containing acid and at least 60% of a water-miscible liquid with the balance essentially water, washing the impregnated paper product with faintly-alkaline water and subsequently drying the product whereby said product is dimensionally stabilized.
• liquid composition comprises 1-5% of formaldehyde, 1-5% of halogen-containing acid, and at least of acetic acid, the balance being water.
• a process for dimensionally stabilized paper consisting essentially of cellulosic fibres selected from the class consisting of natural and regenerated cellulose, which comprises impregnating the paper at a temperature in the range of 20 C. to 40 C. with a liquid composition comprising about 3% of formaldehyde, about 1% of hydrochloric acid, about 88.5% of acetic acid, the balance being water; washing the impregnated paper with faintlyalkaline water having a pH value of about 8 and drying the washed paper at a temperature about C. whereby said paper is dimensionally stabilized.

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Cited By (3)

Citations (3)

• 0
  • NL NL285530D patent/NL285530A/xx unknown
  • BE BE625211D patent/BE625211A/xx unknown
• 1961
  • 1961-11-24 GB GB42178/61A patent/GB969356A/en not_active Expired
• 1962
  • 1962-11-16 US US238272A patent/US3230108A/en not_active Expired - Lifetime
  • 1962-11-21 AT AT916162A patent/AT251404B/de active
  • 1962-11-22 CH CH1369662A patent/CH407734A/de unknown
  • 1962-11-23 LU LU42741D patent/LU42741A1/xx unknown

Patent Citations (3)

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