DK142770B - LIGHT WEIGHT PAPER WITH GREAT STRENGTH AND PROCEDURE FOR PRODUCING THE PAPER - Google Patents

Description

(&) (11) PRESENTATION 1U2770 DENMARK ci. » d 21 h 1/10 '(21) Application No 1229/72 (22) Filed on 1 6 March. 1972 (24) race day 1 Mar 6 1972 (44) The application presented and submitted in publication on 19 · j8ΧΪ · 1 981

DIRECTORATE OF

PATENT AND TRADEMARK (3 °) Priority requested from it

Mar 18 · Mar. 1971, 2115216, DE

(71) PELDMUEHLE AKTIENGESELLSCHAFT, Duesseldorf-Oberkas cell, Fritz-Vomfelde-Platz 4, DE.

(72) Inventor: Fritz Opderbeck, 4005 Meerbusch 1, Rosenstr. 21, DE:

Volker Franzen, 4000 Duesseldorf-Golzheim, Erich-Hoepner-Str. 25, DE: Guicfo Dezeuer, 4000 Dueseeldorf-Gerreeheira, Ikenstr. 78, DE.

(74) Plenipotentiary in the proceedings:

The engineering firm Lehmann & Ree.

(54) Lightweight paper with high rigidity and method of making the paper.

The invention relates to a lightweight paper having a high stiffness for use in office and copying machines and to the process of making the paper.

Over the last 10 years, the field of office technology has seen a revolutionary development, which, in particular with regard to duplication and electronic data processing, has resulted in ever-increasing rates of work. Thus, everyone knows the xerographic method that has completely replaced the previous copying methods based on photographic processes.

The ever-increasing speeds of devices, such as copiers and information readers, place considerable demands on the properties of the paper used in these devices. So far, it has been a particular disadvantage that the paper used should have a high weight. An error-free transport through the apparatus can only be achieved if this paper has sufficient rigidity. On the other hand, this paper must nevertheless be suitable for folding and, in addition, possess some elasticity and sufficient light opacity. Therefore, it has not hitherto been possible to reduce the surface weight of the paper, and the surface weight prescribed by the manufacturers of the apparatus is in the order of about 90 g / m.

This implies the considerable disadvantage that the thickness and weight of such copies are often significantly above the thickness and weight of the original. Due to the ever-growing flow of paper and the associated problems of office space, sufficient storage space and postage costs, there is a great need for a lightweight and stiff paper that is impeccably transportable through modern appliances. In previous attempts to make such a paper, hitherto known finishing options, such as impregnation or coating (coating) of the paper, have proved insufficient. An impregnation of the raw paper results in the paper being stiff throughout and thus no longer possessing the necessary foldability and elasticity. In a surface treatment which is a refinement of the surface, this disadvantage is avoided, but still the desired effect is not achieved because any possible weight saving in raw paper is abolished due to the weight of the applied coating agent.

The object of the present invention is to provide a lightweight, high stiffness paper for use in office and photocopiers, whereby the disadvantages mentioned are eliminated.

This object is solved according to the invention by means of a lightweight paper, characterized in that a bulky inner layer is provided with thin tough elastic outer layers on both sides, which contain the reaction product of hydroxyl- and / or amino group-containing high polymers with compounds which act cross-linking on these, that these cross-linking compounds are aldehydes, aldehyde separating compounds or aldehyde-built precondensates, and that the paper has a surface weight of 35-70 g / m. Such a paper, owing to the elastic outer layers, possesses the absolutely necessary stiffness and, because of its bulky inner layers, can nevertheless be folded, while having sufficient elasticity and light impermeability. Furthermore, the advantage is obtained that the weight of the paper is significantly reduced below the usual weight of paper for use in office and copying apparatus. By means of the elastic properties of the outer layers, the advantage is obtained that, despite its stiffness, the paper can be folded the usual number of times for office paper without breaking the outer layers, even with repeated folding.

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In making the paper, it must be ensured that the bulky inner layer retains the good properties mentioned, namely good foldability and sufficient elasticity. This is achieved by the method of making the paper according to the invention, which is peculiar *, by applying the tough elastic outer layer to the bulky inner layer without impregnating it.

In addition, for technical and cost reasons, the outer layers must be capable of being applied by the usual technique in the paper industry and with the usual apparatus, i.e. application machines, while obtaining as thin and as regularly applied layers as possible * Therefore, components for the elastic outer layers are mixed, i.e. in particular, the hydroxyl group-containing high polyins and the compounds having the cross-linking effect, first immediately before application to the inner layer, so as to prevent the cross-linking reaction from occurring prematurely and an adverse change in the rbeological properties of the mixture.

An advantageous variant of the method consists in that the components are applied to the inner layer one after the other, i.e. first the high polymers and then the compounds having the crosslinking effect. This results in the advantage that the two components first interact with each other on the inner layer, so that there is no danger that the two components may interact with each other for a prolonged period of time before application and solidify by cross-linking, so that the containers and applicators in question are clogged and must be subjected to a difficult cleaning.

As mentioned, as mentioned, high polymers are used which contain the reaction product of hydroxyl and / or amino group-containing high polymers with compounds which act crosslinking on them. It should be noted here that the greater the basis weight of the surface paper, the greater the molecular weight of the high polymers must be to prevent too deep penetration or even impregnation. Therefore, the hydroxyl and / or amino group-containing high polymers should have a molecular weight of preferably between 30,000 and 90,000. Furthermore, the sail elastic outer layers in a preferred form of the invention also contain a thickening agent, e.g. bentonite, which does not participate in the crosslinking reaction, but which enables optimum viscosity control to help prevent ingress of the base paper. Advantageously, impregnation can also be hampered by the fact that the base paper is glued, so that the layer-building principle is strictly adhered to.

Particularly considered as hydroxyl and / or amino group-containing polymers are polyvinyl alcohols, preferably the highly hydrolyzed types, starches and starch derivatives, such as ethoxylated starches and oxyalkyl esters of acrylic and methacrylic acid and amides of these high polysolymers which may also be synthetic risers with other olefin-saturated compounds such as ethylene, propylene-vinyl acetate and vinyl chloride.

Conveniently, the high polymers also contain an addition of 10-60% by weight of protein substances, such as casein and soy protein, based on the weight of the high polymers. These components cause increased stiffness. However, the protein substances should not exceed 60% by weight, otherwise the outer layers will become too brittle, so that a sufficiently high elasticity and thus folding is not achieved.

Particularly suitable is such a lightweight paper in which the cross-linking reaction to the high polymers consists in the interaction of these aldehyde compounds with cyanamide. The use of cyanamide has the considerable advantage that the cyanamide takes on an additional function by forming a connection between the base paper and the outer layer. This extra stabilization of the outer layer and concomitant connection with the base paper is particularly important when it comes to copy paper, which will be discussed in more detail below.

The crosslinking reaction is expediently accelerated by the addition of catalysts such as NaCl, NH4 Cl, HCl or Lewis acid, which helps to prevent impregnation of the base paper.

The invention is described in the foregoing embodiments from the advantageous example in which the outer layers contain the reaction product of hydroxyl group-containing high polymers with compounds which act cross-linking thereto. This preferred embodiment is of great importance because, in particular, paper for copying purposes, especially by the xerographic method, in addition to meeting the requirements of low weight, stiffness and yet good foldability, must also possess a whole host of additional properties obtained by the preferred embodiment.

Such paper is required to maintain its ability to receive print and print sufficiently light impermeable to possess as little surface conductivity as possible, so that, when transported through apparatus such as copiers and readers, electrostatic charge, which causes the sheets to adhere to each other, that the elastic outer layers are not film-forming, but that their air permeability is maintained so that they can be retained in the apparatus by suction, being heat-resistant and not yellowing under heat effect, that the outer layers are not rough, thereby presenting a risk of atomization and soiling, that the stiffness and compressive strength are not lost in heat, which makes all thermoplastic outer layers unsuitable for applications where heat effect occurs and that the manufacture of the outer layers can as far as possible begins in an aqueous phase.

Surface layers of hydroxyl and / or amino group-containing high polymers and compounds having crosslinking effect on them satisfy, in particular, all of these requirements.

The foldability and other mechanical properties which are of particular importance with low weight paper can be further improved by the fact that, for the preparation of the paper according to the invention, a raw paper made in an alkaline environment is suitably used in a pH range of 7.2 to 9.7. Such raw paper has better bonding between the individual fibers, which is of particular importance for the purpose of this light paper.

The following describes the preparation of lightweight high stiffness paper by way of example.

Example 1: $ 60 sulfate needlewood pulp and $ 40 sulfate leafwood pulp are milled in the usual manner to a grinding degree of 38 ° S.R. and mixed with 6% calcium carbonate as filler. At a pH of 7.8 to 8, a paper sheet is then produced in the paper machine which is glued in the usual manner by the addition of a ketene dimer, e.g. "Aquapel" (reg. Trademark) and fixation with a cationic polyamide resin, e.g. "Kymene 557" (reg. Trademark). The paper produced in this way has a surface weight of 47 g / m2 air dry. With a blade, the paper is prepared on both sides with an application of 1.5 - 1.7 g / m The preparation solution used for this application is prepared as follows: For an aqueous solution of 120 g / l high and high viscosity hydrolyzed vinyl alcohol having a degree of polymerization between 1700 and 1800, corresponding to a molecular weight of 75,000 to 80,000 with a degree of saponification of 99.9% t is added to the same amount of an aqueous solution of 120 g / l melamine formaldehyde precondensate. The mixing of the two mentioned solutions must first take place shortly before use and therefore the two solutions are added a small mixing dish in constant uniform dosage with the aid of an irrigation pump and an overflow into this mixing dish.

Then, the crosslinking reaction is carried out in the drying section of the paper machine at a temperature above 100 ° C, conveniently 125 ° C.

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Example 2: 20 # Bleached Fine Wood Grinding Waste with a Grinding Degree of Appropriate 75-82 ° S.R. is milled with 40 # long-fiber sulphate pulp, 25 # deciduous pulp and 15 # decomposed used paper for a material with a degree of grinding between 35 and 40 ° S.R. The paper is glued in the usual way with resin glue and alum and is taken out at a pH of 4.5 -4.8. In a raking, ironing system, a mixture of 50 parts by weight of bone gelatin, 50 parts by weight of highly polymerized highly hydrolyzed polyvinyl alcohol, 25 parts by weight of urea-formaldehyde condensate and 0.5 parts by weight of sodium bentonite is applied. The aldehyde condensate is also added only immediately before application.

The solids content of the applicator is adjusted to the required viscosity under the ratchet and to the desired application. Here too, an application of 1.5 - 3 g / m on each side is sufficient.

Example 3:

Of 40% long-fiber sulphate pulp, 50 # sulphate birch pulp and 10 # wood-free paper waste, in the usual way, a sheet of paper is made with the addition of 10 # kaolin. The pH is 7.8. The bonding is performed by means of a ketene dimer, e.g. "Aquapel" (reg. Trademark) and a nitrogen-containing retention agent, e.g. "Luresin K 20" (reg. Trademark). A surface preparation mass of the following composition is applied to a glue press: 60 # high hydrolyzed polyvinyl alcohol, eg "Mowiol 75/99" (reg. Trademark), 6 # melamine-formaldehyde condensate, f. "Madurit OP" (reg. trademark), and 2 # monomer eyanamide.

Below, components are only mixed immediately prior to application on the paper web. During the subsequent drying in the adhesive press, the paper web is heated as much as possible and is conveniently wound in a warm state without cooling.

Example 4:

Corresponds to Example 3 · In this case, half of the vinyl alcohol is replaced by bone gelatin.

Claims (10)

1. Lightweight, high-stiffness paper for use in office and copying machines, characterized in that a bulky inner layer is provided with thin tough elastic outer layers on both sides which contain the hydroxyl- and / or amino group-containing high polymers turnover product with compounds which crosslinking acts on these, that these crosslinking action compounds are aldehydes, aldehyde separating compounds or aldehyde-built precondensates and that the paper has a surface weight of 35-70 g / m. Lightweight paper according to claim 1, characterized in that the hydroxyl and / or amino group-containing high polymers contain from 10-60% by weight of protein, calculated on the weight of the high polymers. Lightweight paper according to claims 1 and 2, characterized by. that the hydroxyl and / or amino group-containing high polymers have a molecular weight of preferably between 30,000 and 90,000. Lightweight paper according to any one of claims 1, characterized in that the tough elastic outer layers further contain a thickening agent which does not participate in the reaction. Lightweight paper according to claim 3, characterized in that the compounds having the crosslinking effect also contain 10 to 50% by weight of cyanamide. Process for making a lightweight paper according to any one of claims 1-5, characterized in that the tough elastic outer layers are applied to the bulky inner layer without impregnating it. Process for making a lightweight paper according to claim 6, characterized in that the components for the elastic outer layers are first mixed immediately prior to application to the inner layer. 7 142770 Patent Claims. Method for making a lightweight paper according to claim 6, characterized in that the components for the elastic outer layers are applied successively to the inner layer. Process for making a lightweight paper according to any one of claims 6-8, characterized in that the cross-linking reaction is accelerated by the addition of catalysts. Process for making a lightweight paper according to any one of claims 6-8, characterized in that, as a raw paper, an alkaline environment is used at a pH range of 7.2 to 9.7