CF paper

Abstract

The invention concerns a CF paper comprising a base paper and a coating applied thereto, said coating containing at least one binding agent, at least one ink-absorbing agent, at least one coating pigment and conventional additives, and being characterised in that the at least one binding agent comprises a cross-linked biopolymeric material in the form of nanoparticles.

Claims

1. CF paper comprising a base paper and a coating applied thereto, which coating contains at least one binder, at least one developer, at least one coating pigment and at least one additive selected from dispersion agents, defoaming agents, crosslinking agents, rheology controlling agents, antioxidants, UV stabilizers, optical brighteners, lubricants, surfactants, and dyes, wherein the at least one binder comprises a crosslinked biopolymer material in the form of nanoparticles, and wherein said paper contains the crosslinked biopolymer material in the form of nanoparticles in an amount of from 7 to 25 wt. %, based on the overall weight of the coating.

2. CF paper according to claim 1, characterised in that the crosslinked biopolymer material in the form of nanoparticles has a degree of swelling of less than 2.

3. CF paper according to claim 1, characterised in that the crosslinked biopolymer material in the form of nanoparticles is a starch, a starch derivative or a polymer mixture comprising at least 50 wt. % starch or starch derivative.

4. CF paper according to claim 1, characterised in that the crosslinked biopolymer material in the form of nanoparticles has an average particle size of between 10 nm and 1000 nm.

5. CF paper according to claim 1, characterised in that the coating contains an additional binder.

6. CF paper according to claim 5, characterised in that the additional binder is selected from the group consisting of native starches, modified starches, polyvinyl alcohol, styrene-butadiene latices (SB latices), and styrene-acrylate latices (SA latices).

7. CF paper according to claim 6, characterised in that the additional binder is a styrene-butadiene latex and/or a styrene-acrylate latex.

8. CF paper according to claim 5, characterised in that the crosslinked biopolymer material in the form of nanoparticles comprises from 2 to 99 wt. %, of the overall weight of the binders.

9. CF paper according to claim 1, characterised in that the developer is selected from the group consisting of zinc-doped phenolic resins and zinc salts of alkyl-arylated, salicylic acid derivatives or mixtures thereof.

10. CF paper according to claim 1, characterised in that the coating contains a styrene-butadiene latex and/or a styrene-acrylate latex as the additional binder, zinc salts of styrenated salicylic acid derivatives or zinc-doped phenolic resins as the developer, CaCO.sub.3 as the coating pigment, and at least one additive selected from dispersion agents, defoaming agents, crosslinking agents, rheology controlling agents, antioxidants, UV stabilizers, optical brighteners, lubricants, surfactants, and dyes.

11. CF paper according to claim 10, characterised in that the crosslinked biopolymer material in the form of nanoparticles comprises from 2 to 99 wt. %, of the overall weight of the binders.

12. A carbonless copy paper comprising the CF paper according to claim 1 in combination with a CB paper, or in a CFB paper.

13. A method of printing comprising UV-curing offset printing on the CF paper according to claim 1.

14. CF paper according to claim 1, characterised in that the crosslinked biopolymer material in the form of nanoparticles has a degree of swelling less than 1.

15. CF paper according to claim 1, characterised in that the crosslinked biopolymer material in the form of nanoparticles has an average particle size of between 40 nm and 200 nm.

16. CF paper according to claim 1, characterised in that said paper contains the crosslinked biopolymer material in the form of nanoparticles in an amount from 15 to 22 wt. % based on the overall weight of the coating.

17. CF paper according to claim 8, characterised in that the crosslinked biopolymer material in the form of nanoparticles comprises from 40 to 60 wt. % of the binders.

18. CF paper according to claim 3 wherein said nonparticle is starch.

19. CF paper according to claim 9, characterised in that said developer is styrenated.

20. CF paper according to claim 1, characterized that the coating contains an additional binder comprised of styrene-butadiene latex.

Description

EXAMPLES

Example 1: Production and Evaluation of a CF Paper in Which 50% of the SB Latex has been Replaced with Ecosphere 2240 (Developer: Zinc Salicylate Derivative)

(1) Homogeneous aqueous coating slips were prepared according to the dry formulations described in table 1, and uncoated base papers (basis weight 48 g/m.sup.2) were coated using a laboratory coating machine from Koehler SE by means of blade application. Drying was carried out by means of an infrared radiator and hot air. The coating application was determined by means of differential weighing. Prior to evaluation, the temperature of the papers was controlled (22 C., 50% RH) and the additional functional tests were also tested under constant indoor climate conditions. An objective comparison of the carbon copying performance is only possible when the coating binding (test: dry picking) and the whiteness of the paper on which the carbon copy is generated have comparable values.

(2) TABLE-US-00001 TABLE 1 Formulation A B PCC (precipitated [parts by weight] 80 80 calcium carbonate) GCC (ground [parts by weight] 20 20 calcium carbonate) Zn salicylate [parts by weight] 8.8 8.8 derivative SB latex [parts by weight] 25.24 12.62 Ecosphere 2240 [parts by weight] 12.62 Other additives [parts by weight] 2.4 2.4 Dry coating [g/m.sup.2] 4.2 4.0 application Carbon copying [contrast %] 28.0 33.5 performance Whiteness R 457 [%] 91.0 90.6 Dry picking [m/s] 2 1-2

(3) The carbon copying performance was determined as follows: using an electric typewriter (Olympia common 200i, OCR-A.10 daisy wheel, symbol solid area) a defined 34 cm large carbon copying surface was generated on the CF paper to be tested (developer) by a CB paper-tested quality (colour former, black print) and at a defined penetration strength, and the blackening was measured as the reflection 30 s later using an ink measuring device (Elrepho SE070, illuminant D65). The contrast is given in % [(reflection R.sub.y of the unprinted regionreflection R.sub.y of the printed region)/reflection R.sub.y unprinted].

(4) The whiteness of the papers was likewise determined using the ink measuring device Elrepho SE070. Plies of paper were placed one top of one another until the opacity of the stack reached 100% and the whiteness of the surface was then determined by measuring the reflection (illuminant R 457 D 65).

(5) A common test in the paper industry is dry picking, which is used as a measure of the coating binding and thus as a measure of the offset printability. This test was carried out using the printability testing unit Prfbau MZ II from Prfbau Dr.-Ing. H. Drner GmbH. A specific amount of a standardised printing ink was printed, by means of a rubber roller, on a strip of defined dimensions of the paper to be tested in accordance with a specific procedure. If this process were carried out at different speeds, there would be an increased number of flaws in the printed image as a result of paper fibres of pigments tearing out. The maximum printing speed [m/s] in which an error-free printed image is still provided is stated as the value for the dry picking.

(6) This example shows that the use of a coating having formulation B (50% of the SB latex replaced with Ecosphere 2240) leads to a clear improvement in the carbon copying performance compared with the use of a coating having formulation A (100% SB latex).

Example 2: Production and Evaluation of a CF Paper in Which 50% of the SB Latex has been Replaced with Ecosphere 2240 (Developer: Zinc-Doped Phenolic Resin)

(7) CF papers were produced in a similar way to in example 1. The corresponding dry formulations can be seen in table 2.

(8) TABLE-US-00002 TABLE 2 Formulation C D PCC (precipitated [parts by weight] 80 80 calcium carbonate) GCC (ground [parts by weight] 20 20 calcium carbonate) Zn-doped phenolic [parts by weight] 16.0 16.0 resin SB latex [parts by weight] 25.24 12.62 Ecosphere 2240 [parts by weight] 12.62 Other additives [parts by weight] 2.4 2.4 Dry coating [g/m.sup.2] 4.0 4.3 application Carbon copying [contrast %] 25.3 32.5 performance Whiteness R 457 [%] 89.1 89.0 Dry picking [m/s] 1-2 2

(9) The use of a coating having formulation D (50% of the SB latex replaced with Ecosphere 2240) led to a clear improvement in the carbon copying performance compared with the use of a coating according to formulation C (100% SB latex).

Example 3: Production and Evaluation of a CF Paper in Which 50% of the SB Latex has been Replaced with Various Starch-Based Binders (Developer: Zinc-Salicylate Derivative) and of a CF Paper Only Having Ecosphere 2240 as the Binder

(10) CF papers were produced in a similar way to in example 1. The dry formulations can be seen in table 3.

(11) This example shows that replacing some of the SB latex with Ecosphere 2240 leads to a comparable or even slightly better carbon copying performance than replacing some of it with other soluble types of starch.

(12) Ecosphere 2240 was replaced with two conventional starch-based soluble binders in what was otherwise the same coating ink formulation. Native potato starch was used as a 20% solution, which was produced by being heated and subsequently partially enzymatically decomposed by means of -amylase. Sobex 222 is a cold water-soluble highly-substituted depolymerised starch that was used in powder form. In formulation I, SB latex was completely omitted and only Ecosphere 2240 was used as the binder. In comparison with formulation F (SB latex: Ecosphere 2240, 50:50), although a slightly lower carbon copying performance was found, this was still higher than the carbon copying performance of the standard (formulation E).

(13) TABLE-US-00003 TABLE 3 Formulation E F G H I PCC [parts by 80 80 80 80 80 (precipitated weight] calcium carbonate) GCC [parts by 20 20 20 20 20 (ground weight] calcium carbonate) Zn [parts by 8.8 8.8 8.8 8.8 8.8 salicylate weight] derivative SB latex [parts by 25.2 12.6 12.6 12.6 weight] Ecosphere [parts by 12.6 25.2 2240 weight] Sobex 222 [parts by 12.6 weight] Native [parts by 12.6 potato weight] starch Other [parts by 2.4 2.4 2.4 2.4 2.4 additives weight] Dry coating [g/m.sup.2] 4.0 4.0 4.0 4.0 4.0 application Carbon [contrast 32.0 37.5 35.1 35.1 35.2 copying %] capacity Whiteness [%] 91.0 90.4 90.8 90.3 89.6 R 457 Dry picking [m/s] 0.5-1 1 2 1-2 1-2

Example 4: Printability by Means of the CF Paper According to the Invention

(14) In order to demonstrate that replacing 50% of the SB latex with Ecosphere 2240 does not adversely affect printability using UV offset printing inks, a pilot coating test was carried out in order to be able to provide the corresponding amount of paper.

(15) The pilot coating test was carried out using coating inks analogous to those in example 3. Of the two different soluble starches tested in example 3, the cold water-soluble starch Sobex 222 was selected. The coating slips are applied by means of rollers and a flat blade in order to set the coating weight at a speed of 300 m/min.

(16) The papers were printed in a printer by means of offset printing using rollers (7000 running metres) a) using conventional printing inks (absorption drying) and b) using UV-curing printing inks and UV-direct drying after each printing unit (four different inks in four printing units).

(17) Conventional offset printing presented no problems and led to a good printed image in all cases.

(18) In UV offset printing, the coating according to formulation G (soluble starch) led to a build-up of ink on the rubber blanket in two printing units during the printing process, which led to a disturbed print and poor printed image, while the paper having the coating according to formulation F could be printed on without any problems.

(19) The dry formulations and the respective properties can be seen in table 4.

(20) TABLE-US-00004 TABLE 4 Formulation E F G PCC [parts by 80 80 80 (precipitated weights] calcium carbonate) GCC (ground [parts by 20 20 20 calcium weight] carbonate) Zn salicylate [parts by 8.8 8.8 8.8 derivative weight] Ecosphere pre- [parts by 12.6 dispersion weight] Sobex 222 [parts by 12.6 weight] SB latex [parts by 25.2 12.6 12.6 weight] Other additives [parts by 2.4 2.4 2.4 weight] Application [g/m.sup.2] 1.8 1.7 2.8 Carbon copying [contrast %] 25.9 28.2 29.1 performance Dry picking [m/s] 3.5 3.5 3.5 UV offset Ink build up No No Evident in printing using 4 after 7000 m 2 printing inks in 4 units printing units Conventional Overall OK OK OK offset printing evaluation