GB2216555A

GB2216555A - Surface-sizing paper

Info

Publication number: GB2216555A
Application number: GB8906637A
Authority: GB
Inventors: Theodor Lang
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1988-03-25
Filing date: 1989-03-22
Publication date: 1989-10-11
Anticipated expiration: 2009-03-22
Also published as: AU3165189A; CH678868A5; AU612249B2; FR2629110B1; JPH026690A; IT1232825B; IT8947773A0; FR2629110A1; GB2216555B; KR890014834A; GB8906637D0

Description

16555 Case 150-5239 Surface-sizing of paper structures It has been found

that by the combined use of chitosanes and parti cular fatty acid-chromium(III)-complexes as described below, for the surface-sizing of flat structures of paper-stuff, there may be achieved outstanding sizing effects.

The invention provides a process for the surface-sizing of flat structures made of paper stuff, wherein these are treated, after formation of the plain surface, with a sizing composition comprising (a) a chitosane and (b)-a (C12-22-fatty acid)-Cr(III)-complex as sizing active components.

Paper structures made of any paper qualities as conventionally employed for surface-sizing, namely from fine onion skin paper up to cardboard and heavy pulp board, are suitable as substrates for the sizing process of the invention. They may be produced from a large choice of conventional cellulosic fibrous materials of various ori gin, e.g. from wood fibres, mechanical pulp, annual plants, rags (of linen, hemp, cotton, jute etc.) or re-used wastepaper (recycled paper). The paper structure to be surface-sized according to the invention may be unsized or presized and may optionally be reinfor ced with a wet strength agent (as it is e.g. conventional in label paper for the mechanical labelling of bottles and jars). The cellu losic fibrous material employed may be bleached or unbleached. Occa sionally also synthetic paper may be used as a substrate. Advanta- geously there are used paper structures of at least 60g/M2 [heavier papers and board (including cardboard and pulpboard)], in particular board with a basis weight of at least 400g/M2. The surface-sizing of the invention is of particular advantage on flat structures of paper stuff that are produced from optionally bleached secondary fibre derived from re-used wastepaper.

As chitosanes usable as component (a) according to the invention there are suitable any derivatives of chitin known under the name of chitosane that are soluble at least colloidally in aqueous acid (the solubility being meant under such conditions - in particular concen tration, acid content and temperature - as occurring in the applica tion of the compositions). Deacetylation products of chitins of the most various origins in particular of the cx-, 0- or y-forms of chitin or also mixtures thereof (see e.g. M. FLORKIN and E.H. STOTZ "Comprehensive Biochemistry", vol. 26, part C, chapter IX - Elsevier Publishing Company, 1971) come into consideration. The degree of deacetylation may vary in a broad range, in particular so that the average degree of substitution of the amino groups of the poly amino-saccharide backbone by acetyl (as acetylamino) [= Sg(NAc)] is within the scope of 0.70 to 0.00 [Sg(NAc) = 1.0 corresponds to a chitin in which all of the amino groups of the polyamino saccharide backbone occur as acetylamino]. Advantageously there are employed chitosanes in which said degree of substitution Sg(NAc) is < 0.50, preferably < 0.30. Principally there are employed products in which Sg(NAc) is > 0.00, in particular > 0.05. The free amino groups of the chitosane may be unsubstituted or protonated or optionally alkyl-substituted (e.g. by alkylating reactions, principally by alkylation with Cl-4-alkyl), if desired up to the quaternary stage.

The chitosanes may be partially oxydized. The average molecular weight Mw of the chitosanes is advantageously within the range of 1 x 105 to 1 x 107, preferably within the range of 5 x 105 to x 106. According to the simplest and preferred feature in the sizing process of the invention there are employed chitosanes that are neither oxydized nor alkylated at the nitrogen, but which are preferably protonated. For protonation are suitable e.g. mineral acids, in particular hydrochloric acid, or organic, preferably ali phatic carboxylic acids with advantageously 1-6, preferably 2-4 carbon atoms, including formic acid, acetic acid, lactic acid, malic acid, maleic acid, oxalic acid, acrylic acid, crotonic acid, tarta ric acid, glycollic acid and ascorbic acid, of which those with 2-4 carbon atoms are preferred, in particular maleic acid and acetic acid, the latter being most preferred. Advantageously the available amino groups are protonated exhaustively.

As fatty acid-chromium(III)-complexes that are suitable as component (b) according to the invention, there are meant essentially so-called WERNER-complexes as resulting e.g. from the reaction of corresponding fatty acids with basic chromium(III)-salts of mono basic acids, in particular basic chromium chloride [Cr(OH)C121 in anhydrous medium, preferably in an alcohol. These complexes contain two chromium atoms on the average for every fatty acid radical and may contain co-ordinatively-bound water or also co-ordinatively bound alcohols, which may e.g. be those of the reaction medium or alcohols introduced by exchange reaction. These complexes may be represented by the following general formula C1 X2 Cr-Cl Y2 R-C O-H Y, / / / /. (I) I 0 Cr-Cl Cl X1 wherein R signifies an aliphatic hydrocarbon radical with 11-21 carbon atoms, X1? X21 Yj and Y2 signify independently from each other H20 or RI-OH N_ 25 and RI signifies Cl-8-alkyl, optionally interrupted by -0-- 4 Case 150-5239 The fatty acid radicals R-COO- may be radicals of conventional fatty acids, principally of lauric acid, palmitic acid, myristic acid, oleic acid, stearic acid, behenic acid or arachidic acid or also of fatty acid mixtures, in particular technical mixtures including coconut fatty acid, technical oleic acid and tallow fatty acid. Of the mentioned fatty acid, the ones with 12-18 carbon atoms are pre ferred. The alcohols that may optionally be co-ordinatively bound to the complexes (e.g. as X1, X29 Yj or Y2) may be linear or branched and, in particular when containing three or more carbon atoms, may be interrupted by -0(e.g. up to 3 -0-, including mono-, di- or triethylene glycol monoalkylether); preferably come into considera tion aliphatic alcanols with 1-4 carbon atoms, in particular metha nol, ethanol, isopropanol or butanol or also ether alcohols, in particular butylcarbitol. In the above complexes advantageously at least some of the co-ordinatively bound molecules X1, X21 Yj and Y2, preferably X, and X2, are water.

These WERNER-complexes may be produced in a manner known per se, e.g. as described in US Patents 2 273 040 and 3 284 215, which are incorporated herein by reference. Preferably they are employed in the form of an alcoholic or aqueous alcoholic composition with a fatty acid chromium complex content of preferably 10-50% by weight of the composition, the alcohol being of formula RI-OH; in the aqueous/alcoholic compositions, the weight ratio water/alcohol is advantageously in the range of 1:1 to 1:10, preferably 1:2 to 1:6.

The weight ratio (a)/(b) is advantageously in the range of 1/0.2 to 1/5, preferably 1/0.6 to 1/3 - referred to the non-protonated form of (a) -. When combining components (a) and (b) there may be formed com plexes; in these complexes some of the co-ordinatively bound molecules X11 X21 Yj and Y2 may be replaced by an amino or ammonium group of the chitosane and/or optionally by a hydroxy group of the chitosane.

For application on the plain surface structures components (a) and M are expediently formulated to aqueous sizing compositions con- taining advantageously 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight, more preferably 0.05 to 0.25% by weight of component (a) and advantageously 0.03 to.1% by weight, preferably 0.04 to 0.6% by weight, more preferably 0.05 to 0.4% by weight of component (b). The here indicated quantities relating to component (a) refer to the non-protonated form; the acid for the protonation of component (a).

may be added directly into the sizing composition, so that the pro tonated form of component (a) is formed contemporarily, or the pro tonated form of component (a) may be produced previously and the acid content of the sizing composition may then be adjusted to the desired value. The pH of the sizing compositions is advantageously at values within 3 and 6, preferably within 3.5 and 4.5. The chito sane (a) is advantageously used in the form of an aqueous stock solution of its protonated form; preferably there is produced a stock solution that contains 0.5 to 1.2% by weight of chitosane (calculated as non-protonated chitosane) in 0.1N to 1.ON acid, more preferably 0.2N to OAN acid. Component (b) (preferably in the form of alcoholic or aqueous/alcoholic solution as indicated above) is advantageously added only when component (a) is present in dissolved form.

Further compatible sizing components may, if desired, be added to the sizing composition, in particular non-ionic or cationic sizing additives (c), including starch, polyvinyl alcohol or cationic starch. The weight ratio (c)/(b) is then advantageously within the range of 0.3:1 to 7.0:1, preferably within the range of 1.3:1 to 5.0:1. It is, however, particularly preferred not to add any further components but to employ components (a) and (b) as sole sizing-acti ve substances in the compositions of the invention. The aqueous sizing compositions containing (a) and (b) [in particular consisting essentially of (a), (b) and water, together with the required quan tity of acid and optionally alcohol - from the alcoholic or aqueous/ alcoholic solution of (b), if (b) is added in such form -1 may be used for sizing directly after their production or may, if desired, be stored even for a longer time before they are used.

- 6 Case 150-5239 The sizing of the plain-surface structures of paper stuff may be carried out according to conventional surface sizing methods known per se, e.g. by coating with an air-knife, with a doctor blade or with a curtain-coater or also in a size-press. The sizing composi tions of the invention may be applied on the still wet (e.g. only partially dried) substrate or also on the completely dry substrate, and the treated substrate may then be dried in conventional way and at conventional temperatures (in particular at temperatures within and 130C).

The sizing compositions of the invention are highly efficient and of high yield. Depending on the desired sizing effect, there may in particular be applied per M2 of surface such quantities of the sizing compositions that correspond to 0.005 to 0.3g of the sum of components (a) + (b). Depending on the constitution of the substrate and the desired effect the respective quantities may still be optimalized.

By the sizing process of the invention there may be achieved an outstanding high-grade sizing, in particular surface-sizing, which is distinguished by its very good properties, in particular writing and print quality, folding endurance and resistance to water-pene tration. The compositions are also appliable without difficulties on the substrate.

In the following Examples the employed chitosane is an m-chitosane derived from an cc-chitin produced from crab-shells and has an Sg(NAc) = 0.23 and an optical rotation [OF ]D26 = -5 (c = 0.9 in 2% aqueous acetic acid) ("Flonac-N'l);- the employed fatty acid chromium complex is used in the form of a 40% solution in butyl carbitol/ water (3.7/1) and is a myristic acid-chromium hydroxy chloride com plex of the WERNER-kind; the indicated quantities of the fatty acid chromium complex are referred to the 40% solution in butylcarbitol/ water. The indicated quantities of chitosane refer to the dry chito sane. The chitosane is used in the form of a 1% stock-solution in aqueous 2.5% acetic acid. The sizing compositions are produced by adding the chromium complex in these solutions with stirring and then adding the required quantity of water and, if required, acetic acid. The indicated percentages are by weight and the temperatures are indicated in 'C. The indicated Cobb-values are determined after 24 hours.

Example 1

A grey board with a basis weight of 450g/M2, which is produced from 100% mixed waste paper and is unsized in the stock, is surfacesized as follows:

16g/M2 of an aqueous solution containing 0.25g/1 chitosane 2.0g/1 fatty acid-Cr(III)-complex (40%) and 2.5g11 acetic acid are applied by means of a doctor blade to the surface of one side of the paper board and the treated side is then dried adhering to the drying. cylinder during 5 minutes at 901C.

Water-penetration-resistance (Cobb-values) of the paper board:

unsized board: Cobb60 = 46 20 Cobb600 = 360 surface-sized board: Cobb60 = 13 Cobb600 = 80 Example 2 A grey board with a basis weight of 520g/M2, which is produced from 100% mixed waste paper and is unsized in the stock, issurface-sized as follows:

8 - Case 150-5239 16g/M2 of an aqueous solution containing 0.75g11 chitosane 5.0g/1 fatty acid-Cr(III)-complex (40%) and 2.5g/1 acetic acid are applied by means of a doctor blade on one side on the surface of the paper board and the treated side is then dried adhering to the drying cylinder during 5 minutes at 90C. Water-penetration-resistance (Cobbvalues) of the paper board:

unsized board: Cobb60 = 525 10 Cobb600 = 690 surface-sized board: Cobb60 15 Cobb600 = 75. Example 3 A grey paper with a basis weight of 120g/M2, which is produced from 100% mixed wastepaper and is unsized in the stock, is surface-sized as follows:

9g/M2 of an aqueous solution containing 0.25g/1 chitosane 2.0g/1 fatty acid-Cr(III)-complex (40%) and 2.5g/1 acetic acid are applied in the size-press on each side of the two sides of the - paper. Drying is then carried out at the drying cylinder during 5 minutes at MC.

Water-penetration-resistance (Cobb-values) of the paper:

9 - Case150-5239 unsized paper: Cobb60 = 100 Cobb600 = 150 surface-sized paper: Cobb60 = 20 Cobb600 =70.

Example 4

A grey board with a basis weight of 600g/M2, which is produced from 100% mixed waste-paper and is unsized in the stock, is surface-sized as follows:

45g/M2 of an aqueous solution containing lg/1 chitosane 5g/1 fatty acid-Cr(III)-complex (40%) and 2.5g/1 acetic acid are applied by means of a doctor blade on each of the two sides of the board. Drying is then carried out at the drying cylinder during is 5 minutes at 1101C.

Hot-water-resistance of the board:

The sizing degree (impregnation) is tested by means of a floating test on water with a temperature of 90-951C. A sample of the board is allowed to float on the water-surface and the time required for the penetration of the water through the board is measured.

Unsized board: floating test 20 sec. Surface-sized board: floating test over 5 min.

The floating tests are carried out 1 hour after the treatment.

Example 5

A bleached raw paper with a basis weight of 90g/M2 and which is unsized in the stock is surface-sized as follows:

9g/M2 of an aqueous solution containing 0.5g/1 chitosane 6.0g/1 fatty acid-Cr(III)-complex (40%) and 2.5g/1 acetic acid are applied in the size-press on each of the two sides of the paper. Drying is then carried out on the drying cylinder during 5 minutes at MC.

Water-penetrationresistance (Cobb-values) of the paper:

unsized paper: Cobb60 = 96 surface-sized paper: Cobb60 18 Example 6 is A raw label-paper which is presized in the stock with rosin size and aluminium-sulphate and reinforced with a wet-strength agent and having an ashes content of 12% (China Clay) and a basis weight of 65g/M2, is treated in the size-press on the surface of both sides with log/M2 in total of an aqueous solution containing 15g11 fatty acid-Cr(III)-complex (40%) 0.75g11 chitosane and 2.5g/1 acetic acid and is then dried on the drying cylinder at 90C during 5 minutes.

Water penetration-resistance (Cobb-Values) of the paper:

Case 150-5239 Untreated paper: Cobb6o = 40 Treated paper: Cobb60 = 16.5 Sizing degree by the St6ckigt test method:

Untreated paper: 8 sec.

Treated paper: 70 sec.

The Cobb and St6ckigt values are determined 24 hours after the treatment.

Examples This to 6bis Analogously there is employed in examples 1-6 in place of the 40% solution of the fatty acid-Cr(III)-complex in butylcarbitol/water a 40% solution thereof is isopropanol/water.

- 12 Case 150-5239

Claims

1. A process for the surface-sizing of flat structures made of paper stuff, wherein these are treated, after formation of the plain surface, with a sizing composition comprising (a) a chitosane and (b) a (C12-22-fatty acid)-Cr(III)-complex as sizing active components.

2. A process according to claim 1 for the surface-sizing of paper or board, produced from re-used wastepaper.

3. A process according to claim 1 or 2 wherein sizing is carried out with an aqueous acidic liquor, containing (a) and (b).

4. A process according to any of claims 1-3 wherein the weight ratio (a)l(b) is in the range of 1/0.2 to 1/5.

5. A process according to any of claims 1-4 wherein 0.005 to 0.3g of [(a) + (b)] are applied per M2 of surface.

6. An aqueous composition comprising components (a) and (b) defined as in claim 1.

7. An aqueous composition according to claim 6 with a pH in the r ange of 3-6.

8. A composition according to claim 6 or 7, wherein (a) has a Sg(NAc) in the range of 0.00 to 0.50 and (b) is a WERNER-complex obtainable from C12-22-fatty acid and basic chromium chloride in alcoholic medium.

9. An aqueous composition according to any of claims 6 to 8 con- sisting essentially of (a), (b), water and the required quantity of acid and optionally alcohol.

10. A chromium-complex obtainable by admixing (a), a chitosane, with (b), a (C12-22-fatty acid)-Cr(III)-complex, in aqueous acidic medium.

11. A process for the production of compositions according to any of claims 6-9 or complexes according to claim 10 wherein component (b) is mixed with an aqueous acidic solution of component (a).

12. A process according to claim 11, wherein component (b) is added in the form of an alcoholic or aqueous/alcoholic solution.

13. A process for the surface-sizing of flat structures made of paper stuff, wherein these are surface-sized with a composition according to any of claims 6-9 and 11 or a chromium complex [(a) + (b)] according to any of claims 10 to 12.

14. A process according to claim 13 for the surface-sizing according to any of claims 1-5.

15. Substrates whenever surface-sized by a process according to any of claims 1-5, 13 and 14.

16. A process for the surface-sizing of flat structures made of paper stuff according to any of claims 1-5, 13 and 14 as herein before described and as specifically disclosed in any of examples 1 to 6 and This to 6bis.

17. A composition according to any of claims 6-9 or chromium complex according to claim 10 as hereinbefore described and_as specifi cally disclosed in any of examples 1 to 6 and This to 6bis.

18. A process according to claim 11 or 12 as hereinbefore described and as specifically disclosed in any of examples 1 to 6 and This to 6bis.

19. A flat structure made of paper stuff according to claim 15 whenever surface-sized according to any of claims 1-5, 13 and 14 as hereinbefore described and as specifically disclosed in any of examples 1 to 6 and This to 6bis.

m Published 1989 at The Patent Office. State House. 66.71 High HolboMLondonWCIR 4TP. Further copies maybe obtainedfrom ThePatentofnce.

Sales Branch, St Mary Cray, Orpington, Kent BR5 3RD. Printed by Multiplex techniques ltd, St Mary Cray, Kent, Con. 1187