RU2436883C1 - Method of manufacture of paper-based coloured product and paper-based coloured product - Google Patents

Abstract

FIELD: paper industry.

SUBSTANCE: one side of paper-based substrate is coated with the first dyeing composition to provide the degree of whiteness L* with the value of L1. The second dyeing composition is applied to the opposite side of the substrate having the degree of whiteness L* with the value of L2. A colored product is obtained, characterised by the degree of whiteness L* with a value of L3 for the first coated side. The second coated side of the product has a degree of whiteness L* with a value of L4. Thus L1 is not more than 8 points higher than L3, and L2 is at least 30 points higher than L4. The degree of whiteness L* is determined using the colour characteristics CIE L* a* b*, a clarifier D 65, and at the observation angle of 10°C. In this method, the penetration of dyeing substances of the dyeing composition is adjusted so that the minimal impact is achieved on the degree of whiteness of the coating of white or light colour on the opposite side of coloured paper.

EFFECT: obtaining high-quality colored paper, which has a high contrast ratio to ensure high-level package, simplification of method, reducing of cash expenses, time expenditures and labor.

15 cl, 1 dwg, 2 tbl

Description

BACKGROUND OF THE INVENTION

Paper or paperboard used to provide high-level packaging, such as packaging for cigarettes or cosmetics, usually has a high contrast between the two sides of the sheets. The contrast may be between black or dark on one side of the sheet and white or significantly lighter color on the opposite side. For example, this high-quality colored paper is made by laminating on one side of black paper with metal foil.

Colored paper is usually made by adding dyes, such as dyes and pigments, to the paper pulp, to the wet part of the papermaking process, before forming the paper web. This color paper manufacturing process has a lot of disadvantages. Coloring pigments are usually insoluble in water; therefore, alum and / or auxiliary holding means are required to hold the pigments in the paper web. In addition, poor adhesion of the coloring pigments to the pulp results in low color fastness. To overcome this drawback of poor adhesion, US Pat. No. 5,131,981 discloses a process for dyeing paper in the wet part of a paper machine by using coloring pigments and color fixing agents, in which pigment and color fixing substances are added simultaneously to the paper pulp to be dyed. Use cationic compositions of substances for fixing color, to improve the adhesion of coloring pigments with paper pulp. Adding dyes to the paper pulp causes the staining of waste water, which leads to environmental pollution and other complications of the process. Coloring occurs over the entire thickness of the paper, therefore, a large amount of coloring matter is required. This happens even if only the surface of the paper needs to be painted, which leads to unnecessary costs. In the development of each batch of paper, it is necessary to produce a large quantity of it. The minimum amount of paper produced at the paper mill during the production of each batch of paper is much larger than the usually required amount of high-quality colored paper. As a result, the paper manufacturer is burdened with a large supply of unused colored paper or the paper mill does not start producing colored paper until at least a minimum quantity of each batch of paper has been ordered.

Colored paper can be made by applying a coloring composition to the surface of the paper after forming the paper. As stated in PCT publication WO 2007/128077, this process enables the production of colored paper that has the quality characteristics that make it suitable for packaging, but, unfortunately, this process is costly. For high-quality paper used in the form of high-level packaging paper, which has high contrast requirements between the sides of the paper, this process has an additional drawback. When applying a coloring composition to the surface of the paper, coloring matter penetrates the inside of the paper and can adversely affect the color of the opposite side of the paper. This disadvantage is especially pronounced when the paper is first painted white or light, and then painted black or dark on the opposite side. Colorants of black or dark color can penetrate the paper and reduce the degree of whiteness on the opposite side, coated with colorants of white or light color. As a result, high-quality paper used to provide high-level packaging is usually made by: (a) dyeing the pulp in the wet part of the paper manufacturing process with black or dark color pigment; (b) molding the colored paper web from the colored paper pulp; (c) rolling a colored paper web resulting from a manufacturing process; (d) transferring and (e) rewinding the colored paper web to carry out the process of laminating paper with foil or to autonomously apply a white or light colored ink composition. This process, which corresponds to the state of the art in this field, is a process requiring a lot of labor and time, complicated and expensive.

Accordingly, there is still a need for a high-quality color paper manufacturing process with high contrast, used to provide high-level packaging that is relatively simpler, less capital-intensive, and also requires less time and labor compared to a modern process prior art in this field.

It is also advisable to have the process of manufacturing high quality colored paper with high contrast, consisting in applying a coloring composition to the formed paper, according to which the penetration of coloring substances of the coloring composition can be adjusted so that a minimum effect on the brightness of the coating is white or light color with the opposite sides of colored paper.

Disclosure of invention

High-quality colored paper with high contrast, suitable for providing high-level packaging, is made by controlled penetration of the ink composition through the paper. The first side of the paper is coated with the first ink composition. Then, the second coloring composition is applied to the second side (i.e., the opposite side) of the paper so that the coloring agent entering the second coloring composition penetrates the paper web but does not significantly affect the whiteness of the white or light colored coating of the first the coated side of the paper. If necessary, the first coloring composition can be applied to the paper on the production line during the paper manufacturing process.

Brief Description of the Drawing

The drawing shows one embodiment of the disclosed method for manufacturing high quality color paper with high contrast, suitable for providing high level packaging.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in more detail below, but not all embodiments of the invention are necessarily shown. Although the invention has been described with reference to exemplary embodiments, those skilled in the art should understand that various changes can be made to the invention and that elements of the invention can be replaced by equivalent solutions without departing from the scope of the invention. In addition, many modifications can be made to adapt specific situations or materials to the provisions of the invention without departing from its main scope.

The disclosed method for manufacturing a paper-based colored product includes the steps of:

(a) providing a paper-based backing having a first side and a second side;

(b) coating the first side of the substrate in the form of a first coloring composition to provide a brightness level L * with a value of L1; and

(c) coating a second side of the substrate having an L * whiteness of L * with a value of L2 as a second coloring composition to produce a paper-based color product characterized by a L * whiteness of the first side coated with an L3 value and L * of whiteness second side coated with a value of L4,

where L1 is no more than 8 points greater than L3, and L2 is at least 30 points greater than L4, and where the brightness degree of L * is determined using the CIE color characteristic L * a * b * (CIE - International Commission on lighting (CIE)), when using the D65 illuminator and at a viewing angle of 10 °.

Figure 1 shows one embodiment of the disclosed method for manufacturing high quality color paper having high contrast, suitable for providing high level packaging. The paper-backed substrate 100 has a first side 101 and a second side 102. The first ink composition is applied to the paper side 101, resulting in a degree of whiteness L * equal to L1 of the coated side 101. The uncoated second side 102 has a whiteness degree L * equal to L2. Then, a second coloring composition is applied to the substrate side 102 and a colored paper web with a double-sided coating is obtained, characterized by the brightness levels L * of the coated sides 101 and 102 equal to L3 and L4, respectively. The resulting high quality color paper has an L1 value that is more than 8 points higher than L3 and an L2 value that is at least 30 points higher than L4, where L * whiteness is determined using the CIE color characteristic L * a * b * , when using the D65 illuminator and at a viewing angle of 10 °.

In one embodiment of the present invention, the second coloring agent included in the second coloring composition penetrates the treated paper in a controlled manner so that a gradual decrease in the intensity of the second color can be achieved from the second coated side to the first coated side.

In addition, the penetration of the second dye included in the second dye composition can be controlled so that the treated paper is dyed by the second dye throughout its thickness or only partially. The second colorant can be colored, if necessary, from about 10% to about 100% of the thickness of the processed paper.

In one embodiment of the present invention, the paper-based substrate is first coated on the first side in the form of a white or light coloring composition. Then, the coloring composition of black or dark color is applied to the second side (i.e., to the opposite side) of the paper so that the coloring substance included in the composition of black or dark color penetrates the paper web, but does not significantly affect the color or degree the whiteness of the first coated side of the paper.

In one embodiment of the present invention, colored paper comprising a first side coated with a white or light ink composition can be produced on a production line during the paper manufacturing process.

In one embodiment of the present invention, the white or light ink composition is a paper coating composition, such as is commonly used in the pulp and paper industry.

In one embodiment of the present invention, a coating is applied to the first side of the paper-based substrate for coating paper on a production line during the paper manufacturing process to produce paper with one-side coated coating. Then, a black or dark color composition is applied to the uncoated side of the resulting paper with a single coated coating.

In one embodiment of the present invention, the second ink composition comprises a coloring agent and a surfactant in such a ratio that the coloring agent can controllably penetrate the paper web without significantly affecting the color or brightness of the other side of the paper. Here, the surfactant is a component that has a significant impact on the regulation of the penetration into the paper web of a coloring substance included in the second coloring composition. The ratio of the coloring matter to the surfactant in the second coloring composition can be optimized in such a way as to ensure minimal effect on the color or brightness of the other side of the paper. This ratio may depend on a variety of factors, for example, the thickness of the paper-based substrate, the type of colorants applied, the type of pulp used in the paper-based substrate, and especially the type of final destination of the package. Thus, there is a range of ratios of the coloring matter and surfactants in the actually used second coloring compositions.

In one embodiment of the present invention, the second coloring composition comprises:

(a) from about 1 wt.% to about 10 wt.% a coloring matter; and

(b) from about 1 wt.% to about 5 wt.% surfactant.

In one embodiment of the present invention, the second coloring composition comprises:

(a) from about 1 wt.% to about 10 wt.% a coloring matter; and

(b) from about 0.1 wt.% to about 3.0 wt.% surfactant.

Surfactants suitable for use in accordance with the present invention may be anionic, cationic, nonionic, amphoteric surfactants, and combinations thereof. Examples of surfactants include (but are not limited to this list): polyalkylene glycol, copolymers of polypropylene oxide and polyethylene oxide, fatty acid and surfactants based on derivatives of fatty acids.

In one embodiment of the present invention, the coloring composition contains a coloring matter and a surfactant and does not contain glue. Without any intention of being associated with any theory, it seems that the glue prevents the penetration of the coloring matter into the inside of the paper.

Coloring compositions can be applied to a paper-based substrate using any known application method. These methods include (but their composition is not limited to this list): the press method of applying the sizing, brushing, spraying, shafting, coating with the removal of excess strip, dipping, spilling, air scraper, watering, and combinations thereof.

Examples

Bleached cardboard was used as a paper-based backing. The coating composition was applied on one side of the cardboard. The resulting coated coated cardboard was then divided into two groups. The first group was saved as a control group of samples. On the uncoated side of the second group of coated paperboard samples, a black coloring composition was applied containing about 2 wt.% Surfactant and about 5 wt.% Black coloring material to obtain a color board with a double-sided coating. The thickness, color, shade and smoothness of the surface of the specified color cardboard with double-sided coating and the control group of samples of coated cardboard were determined.

The gauge, or thickness, of the paperboard was measured according to the standard for testing conditions TAPPI T 411 (TAPPI - Technical Association of the Paper Industry (USA)). Two types of methods were used to determine the smoothness of the cardboard surface: the Parker Print Surf Test Method (PPS), which meets the TAPPI 555 Test Standard, and the Sheffield Test Method, which meets the TAPPI 538 Test Standard.

The color and tint of each side of the test board was determined using the CIE L * a * b * color characteristic. The L * value represents the degree of whiteness or the total amount of light reflected by the surface of the paper, where L * = 0 means black, and L * = 100 means diffused white. The value a * represents the axis from green to red / magenta, where a negative value of a * means green, while a positive value of a * means magenta. The b * value represents the axis from blue to yellow, where a negative value of b * means blue, and a positive value of b * means yellow. The color of the cardboard was determined in the CIE L * a * b * color space at a viewing angle of 10 ° and when using the D65 illuminator as a light source. Each side of each paperboard was color-tested three times to obtain average values of L *, a * and b * .

The properties of the reference cardboard sample are shown in Table 1, and the properties of the double-sided color coated cardboard disclosed in the invention are shown in Table 2. The color in the CIE L * a * b * color space of the side of the coated coated control sample was compared with the coated side color of the cardboard sample disclosed in the invention. The color in the CIE L * a * b * color space of the uncoated side of the control cardboard sample was compared with the color of the side of the cardboard sample disclosed in the invention coated with a black ink composition.

When the uncoated side of the cardboard was coated with a black ink, the values of L *, a *, and b * decreased significantly, confirming a significant change in hue and color. The degree of whiteness L * (L4) of the side of the cardboard disclosed in the invention, coated with a black ink, was 66 points lower than the degree of whiteness L * (L3) of the uncoated side of the control sample of coated cardboard. On the other hand, the brightness degree L * (L2) of the coated side of the cardboard disclosed in the invention was approximately the same as the brightness degree L1 of the coated side of the coated cardboard of the control sample. This means that the black ink penetrated the inside of the cardboard to a certain level, but not through the cardboard. If the black ink penetrated through the cardboard to the opposite side with a coated coating, the degree of whiteness of L4 would be much less.

Table 1 Thickness (number of points) PPS smoothness Sheffield Smoothness White coated side Uncoated side L * (L1) a * b * L * (L3) a * b * 13,2 1.8 24 94,683 -1,130 2,836 93,623 -1,572 2,237 94,670 -1.177 2,796 93,654 -1,559 2,210 94,683 -1,160 2,782 93,690 -1.568 2,212 94,679 -1,156 2,805 93,656 -1,566 2,220

table 2 Thickness (number of points) PPS smoothness Sheffield Smoothness White coated side The side coated with the coloring composition disclosed in the invention L * (L2) a * b * L * (L4) a * b * 13.9 1.9 66 92,784 -1.079 2,924 27,364 0.014 -0.886 93,005 -1.048 2,493 27,323 -0.017 -0.903 93,326 -0.989 3,043 27,540 -0.002 -0.857 93,038 -1.039 2,820 27,409 -0.002 -0.882

Tables 1 and 2 show the controlled diffusion of a black coloring matter in cardboard with minimal impact on the shade or color of the coated side.

In the above example, the colored cardboard disclosed in the invention contains a coated coating on one side and a black coating on the opposite side. However, it should be understood that this example is just one embodiment and is not intended to limit the scope of the present invention.

Although the invention has been described with reference to various specific embodiments, it should be understood that a number of different changes can be made within the spirit and scope of the described invention. It is intended that the invention should not be limited by the described embodiments, but should cover the entire scope defined by the following claims.

Claims (15)

1. A method of manufacturing a colored product on a paper basis, comprising the steps of:
(a) providing a paper-based backing having a first side and a second side;
(b) coating the first side of the substrate in the form of a first coloring composition to provide a brightness level L * with a value of L1; and
(c) coating a second side of a substrate having an L * whiteness with an L2 value as a second coloring composition to produce a paper-based color product characterized by an L * whiteness with an L3 value for the first coated side and a whiteness L * with an L4 value for the second side coated;
wherein L1 is not more than 8 points greater than L3, and L2 is at least 30 points more than L4, and the brightness level L * is determined using the CIE color characteristic L * a * b * when using the D65 illuminator and at a viewing angle of 10 °. 2. The method according to claim 1, in which L1 is not more than 3 points more than L3. 3. The method according to claim 1, in which L2 is at least 40 points greater than L4. 4. The method according to claim 1, in which the second coloring composition contains a second coloring matter, and the color intensity of the second coloring matter in the colored paper-based product is gradually reduced in the direction from the second coated side to the first coated side. 5. The method according to claim 1, in which the second coloring composition contains a coloring substance, which stains from 10% to 100% of the thickness of the painted product on a paper basis. 6. The method according to claim 1, in which the first coloring composition contains a composition for coating paper. 7. The method according to claim 1, in which the first coloring composition is applied to the substrate during the papermaking process. 8. The method according to claim 1, in which the second coloring composition contains:
(a) from 1 wt.% to 10 wt.% a coloring matter; and
(b) from 1 wt.% to about 5 wt.% surfactant. 9. The method of claim 8, in which the second coloring composition does not contain glue. 10. A paper-based colored product obtained by a method comprising the steps of:
(a) providing a paper-based backing having a first side and a second side;
(b) coating the first side of the substrate in the form of a first coloring composition to provide a brightness level L * with a value of L1; and
(c) coating a second side of a substrate having a brightness degree of L * with a value of L2, in the form of a second coloring composition, wherein
(i) the first side of the product coated has a brightness of L * with an L3 value, and the second side of the coated has a brightness of L * with an L4 value;
(ii) L1 is not more than 8 points more than L3, and L2 is at least 30 points more than L4, and the brightness values of L are determined using the CIE color characteristic L * a * b * when using the D65 illuminator and at a viewing angle of 10 °. 11. The product of claim 10, characterized by an increase in smoothness index according to the Parker Print Surf method, by no more than 1 point after applying the second coloring composition in step (c). 12. The product of claim 10, characterized by an increase in thickness of not more than 1 point after applying the second coloring composition in step (c). 13. The product of claim 10, in which the second coloring composition contains a second coloring matter, and which is further characterized by a gradual decrease in the color intensity of the second coloring matter in the direction from the second coated side to the first coated side. 14. The product of claim 10, in which the second dye composition contains a second dye, and which is further characterized in that from 10% to 100% of its thickness is dyed by the second dye. 15. The product of claim 10, in which the second coloring composition contains:
(a) from 1 wt.% to 10 wt.% a coloring matter; and
(b) from 1 wt.% to 5 wt.% surfactant.

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