KR910001575B1 - High solids content coated back composition - Google Patents

Abstract

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Description

Aqueous composition for coatings with high solid content

The figures are graphs showing the reflectances of uncoated paper substrates, paper substrates coated with conventional low-solids coating compositions and paper substrates coated with coating compositions formulated according to the invention, prepared according to the present invention. Improved whiteness of CB paper.

The present invention relates to a coated back (CB) component of a pressure-sensitive record element, commonly referred to as carbonless copy paper. In particular, the present invention relates to a coating composition based on sodium carboxymethyl cellulose (CMC) and a paper coated with such a composition, which has a high coating viscosity and a high solid content.

Carbonless radiant paper consists of two or more stacked sheets. The back side of the sheet has a coated backing or coating containing color-forming material, referred to as "CB". The coating consists of a continuous matrix or microcapsules containing color-forming materials. In use, the front face of the receiver sheet that comes into contact with the backside of the sheet overlaid is covered with a composition containing a developer component that reacts with the color-forming material. Partial pressure on the top sheet causes the coating layer containing the color-forming material to rupture, thereby releasing the color-forming material in contact with and reacting with an interreactive or developer coating that coats on the receiver sheet. A visible color is formed at the portion corresponding to the position where pressure is applied to release the color-forming substance. Thus, applying pressure to the upper sheet results in a corresponding marking on each front of the sheet, which has been folded several sheets.

Processes for preparing coating materials containing color-forming materials (also called color precursors or leuco dyes) dissolved in a solvent have been disclosed in the prior art. Conventional patents, such as US Pat. Nos. 4,397,483, 4,082,688, and British Patent 1,280,769, for use in pressure sensitive recording materials consisting of carboxymethylcellulose precipitates containing oily solvents and color-forming reactants. CB coating material is described. The oil containing the color-forming reactant is emulsified in aqueous sodium carboxymethyl cellulose solution, and metal salts are added to precipitate the cellulose with a few drops of the oil dye solution contained in the separated phase. The resulting emulsion is coated on the backside of the upper sheet of the carbonless radiation system and then dried. Crosslinking resins are sometimes added to the emulsion to harden the resulting coating layer.

Although such claddings are typically successful, high CB compositions based on aspects of the art are unstable and their viscosity is too high to cover in the coatings and methods currently in use. CB coatings with low solids content (eg 20% non-aqueous components) require a lot of energy and require a longer drying time. Therefore, it is desirable to provide a CB coating having an efficient coating viscosity and a high solids content.

It is not possible to merely reduce the moisture content to increase the solids content of known CMC-based coating compositions, as a result of which several significant rheological problems arise. The characteristic of CMC aqueous solution is that the viscosity increases exponentially with increasing CMC concentration. Thus, any benefit of producing a coating composition that can be dried faster by simply increasing the CMC content is offset by the disadvantage that the viscosity of the composition is unacceptably high and poor workability.

It is an object of the present invention to provide an improved CB coating having a low viscosity and high solids content so as to be more easily coated on paper and other substrates. Another object of the present invention is to increase the drying efficiency by providing a coating composition having a high solid content and a low moisture content. In addition, an object of the present invention is to save labor and energy by providing a coating composition having a low moisture content. Another object of the present invention is to form an improved image on a computer using a pressure-sensitive paper and a dot matrix printer by providing CB paper with improved emission efficiency of the color-forming agent. It is a further object of the present invention to provide a CB coating which is whiter in appearance. Another object of the present invention is to reduce the deformation of paper substrates by the wetting of the fibers and to provide a CB coating that can be applied to papermaking machines.

It has been found that CB coatings with efficient and stable coating viscosities, improved CB products, and high solids content can be prepared using certain types of CMCs, acrylic resins, organic crosslinkers, and metal salts that can precipitate CMCs. lost. By using the composition of the present invention, it is composed of a CB coating composition having a high solid content, that is, about 30% by weight or more of non-aqueous materials, and can minimize various problems conventionally encountered in the CB coating composition, and the coating viscosity is effective. The composition can be prepared.

The coating composition is an emulsion of an oil containing at least one color-forming reactant in an aqueous solution of CMC, preferably a sodium CMC having a degree of substitution of 0.65 to 1.8, a wall-forming acrylic resin, a polyvalent metal salt, and an organic solvent. The crosslinking agent, and any other components, are formulated in an amount sufficient to bring the total solids content of the composition to at least 30% by weight, preferably at least 35% by weight, the Brookfield viscosity of which It is within the range of about 50 to 5000 centipoise (cps) required for use or for coating at selected web speeds. Solids weight percentages used herein include all components in the composition except water. Ie dyes present in oils and dissolved dyes or coating compositions. In a preferred embodiment, the wall forming acrylic resin is a carboxylated polyethylacrylate / methyl methacrylate copolymer, most preferably the ratio of ethylacrylate to methyl methacrylate is about 2: 1. Organic crosslinkers are polyamide-epichlorohydrin or other resins capable of crosslinking CMC and carboxylated acrylic resins. Preferred metal salts are aluminum nitrates. In a preferred embodiment of the present invention, CMC having a low viscosity (60 to 170 cps as a 6% aqueous solution) and a high degree of substitution (eg 1.1 to 1.5) is used.

In another aspect, the present invention is directed to an improved CB sheet consisting of a web having a bonded and dried coating layer of the type described above wherein the color-forming agent is released when pressure is applied. This CB sheet is characterized by enhanced phase strength, low limit pressure, and low price.

According to the present invention, low viscosity CMC having a degree of substitution of about 0.65 to 1.8 is dissolved in water. CMC is an anionic water soluble polymer derived from cellulose. Degree of substitution means the average number of substituted carboxymethyl groups per anhydroglucose unit. The high degree of substitution enhances the compatibility with other water soluble components of CMC. The CMC used according to the invention is preferably an alkali metal CMC such as sodium CMC having a degree of substitution of 1.1 to 1.5 (carboxymethyl group substitution on average of 1.1 to 1.5 per anhydrous glucose unit).

Wall-forming acrylic resin is added to this aqueous solution. Preferred resins are carboxylated copolymers of polyethylacrylate / methyl methacrylate (preferably with a ratio of about 2: 1), for example Carboset 514H (manufactured by carboset 514 H, B.F. Goodrich). Other resins that may be used include carboxylated copolymers of styrene with polybutylacrylates such as Acrysol-WS-24 (ACRYSOL-WS-24, manufactured by Rohm & Hass).

Subsequently, a dye solution in an oil solvent is added to the acrylic resin-CMC solution. Suitable dyes and oil solvents are known in the art. Preferred oil-dye solutions are colorless or light colored and dissolved basic, chromogenic lactone or phthalide dyes in effective solvents, such as alkyl biphenyls, which develop upon contact with acid. The particular dye or dyes and the particular oil or oils used do not form part of the invention by themselves.

In a preferred embodiment, however, the dye or dyes used are dissolved in active oil at a concentration of 3 to 12% by weight.

To the resulting biphasic mixture is added a crosslinking agent, ie a cationic, water soluble polyamide-epichlorohydrin resin which crosslinks carboxymethylcellulose and a water soluble wall forming carboxylated acrylic resin. Other useful crosslinkers include formaldehyde-donating resins such as formaldehyde resins or melamine formaldehyde resins. Kymene 557H (manufactured by Hercules, Inc.) is a preferred crosslinker. Kymenn 557H is a highly efficient, cationic, high wet strength resin that operates under acidic or alkaline conditions. The mixture of CMC, acrylic resin and the above crosslinking material provides a water-insoluble film coating having good flexibility and strength. The chimen reacts with hydroxyl and carboxyl groups, but a study reported by Hercules Inc. mainly reacts with carboxyl groups.

An aluminum nitrate solution (eg less than 5% by weight) is then added to the emulsion. Aluminum nitrate is used in CB compositions to insolubilize CMC. Finally, a starch dispersion or a dispersion of other particles acting as a spacer material is added to the mixture.

The resulting coating composition has a high solids content of at least 30% by weight. The viscosity of the composition can vary widely and can easily control the viscosity in certain cases by reducing water content and / or using high viscosity CMC. For air knife coating, the viscosity of the composition measured with a Brookfield RVF viscometer (# 4 spindle) at 100 RPMs is adjusted to 5 to 250 cps, preferably 60 to 100 cps. For roll coating, the viscosity should generally be in the range of 50 to 120 cps; For rod coating, it should be within 50 to 600 cps; For blade coating, it should be in the range of 300 to 5,000 cps. The viscosity used must be determined by the coating apparatus used and the coating speed.

In a preferred embodiment, the ratio of the inner phase composed of oil and dye to the outer phase composed of CMC and organic crosslinker is increased compared to the prior art. For example, in the preferred CB paper according to the present invention, the mass of the inner phase is increased by about 35% compared to the coating compositions of the prior art.

When used in a carbonless radiation system, the composition is coated on the back side of a paper or other substrate, usually at a coating weight (dry weight) of about 3.00 g or more per square meter, and then dried. When pressure is applied to the substrate, the color-forming material is transferred by the oil to the sheet of the underlying layer containing the material reactive with the dye to form a colored image corresponding to the pressured portion.

Essential components of the coating composition of the present invention are CMC having a degree of substitution of 0.65 to 1.8, a wall forming carboxylated acrylic resin, an organic crosslinking agent and a metal salt. The composition should generally contain about 50 to 200 parts acrylic resin, 10 to 150 parts crosslinker, 300 to 1,000 parts oil and dye, and 4.4 to 12.2 parts salt per 100 parts (dry weight) of CMC used. Preferably, about 60-100 parts of wall forming resin, 60-100 parts of crosslinking agent, 600-800 parts of oil and dye, and 5-6 parts of metal salt per 100 parts of CMC used should be present. As a preferred case, when spacer particles are used, there are 100 to 500 parts, preferably 200 to 300 parts, per 100 parts of CMC.

As a result of carrying out the present invention, it was found to be superior to the conventional composition. High solids content and low viscosity CB coating compositions can be coated and dried at high coating rates with practically energy savings. The productivity of the coating composition preparation increases with the ability to produce fewer batches while maintaining the same dry coat weight. The color of the composition of the present invention is whiter than conventional CMC base CB compositions. Improved release efficiency allows phase formation at low pressures. In the compositions of the present invention, CMC, carboxylated acrylic resins and crosslinkers can be prepared in aqueous coating compositions which can be adjusted in any of a wide range of viscosities and have stable rheological properties.

It is to be understood that the present invention will be further understood from the following examples which are intended to illustrate but not limit the invention.

Example 1

A composition for coating a blue labeled CB having a high solid content is prepared according to the following method. All ratios are expressed in parts by weight. Prepare the following solution.

Weight of substance

[Form A]

H ₂ O 920.00

Carboxymethylcellulose (1.2DS and low viscosity) 80.0

Solids content of the resulting solution is 8%.

[Form B]

Oils and dyes 1820.0

The dye content of the resulting solution is 4.7%.

[Formula C]

Starch Spacer Dispersion ₃ 1000.0

Solids content of the resulting solution is 32.48%.

1 Na-CMC 12UL (manufactured by Hercules, Inc.)

2 Preferably, 820 parts of deodorized kerosene (manufactured by Penreco) and 1000 parts of alkyl biphenyl (Suresol 290 manufactured by koch chemical Co.), and crystal violet lactone and Copikem IV (manufactured by Hilton Davis Co.)

3 Preferably, it is water; CMC-7H manufactured by Hercules Inc .; And starch particles (particle size approximately 10-25 μ).

120 parts of carboxylated polyethylacrylate / methyl methacrylate copolymer (preferably carboset 514H) is added to 1300 parts of Formulation A. 600 parts of Formulation B are added to the resulting mixture with stirring. Continue stirring until emulsification is complete. 100 parts of polyamide-epichlorohydrin crosslinker (preferably Kymene 557H) is then added to the emulsion. Then, 170 parts of aluminum nitrate aqueous solution having a solid content of 1.4% was slowly added to 1200.0 parts of the emulsion, wherein the solid content of the coating composition was 31% and the Brookfield viscosity was 250 cps at 100 RPM (78 ° F, pH 5.9). The particle size of the oil droplets is 2 to 10 microns. Finally, 300 parts of Formulation C were added to obtain a coating composition having a solid content of 32% and a Brookfield viscosity of 200 cps.

Example 2

According to the following method, a CB coating composition having a high solid content is prepared.

Formulations A to C are prepared according to the method of Example 1. 120 parts polyethylacrylate / methyl methacrylate copolymer is added to 670 parts Formulation A. 600 parts of Formulation B are added to the resulting mixture with stirring. 480 parts of polyamide-epichlorohydrin crosslinker are then added. Then 190 parts of aluminum nitrate solution having a solid content of 1.4% are slowly added to an emulsion of 1200 parts. The coating composition had a temperature of 78 ° F., a pH of 5.6, a solids content of 35%, a Brookfield viscosity of 100 cps, and an oil droplet size of 2 to 10 microns. Finally, 340 parts of Formulation C were added to the coating composition to prepare a coating composition having a solids content of 35.4% and a Brookfield viscosity of 90 cps. After mixing for 5-10 minutes, the viscosity was 120 cps.

Example 3

125 parts of carboxylated polyethylacrylate / methyl methacrylate copolymer are added to 765 parts of Formulation A. 900 parts of Formulation B are added to the resulting mixture with stirring. 400 parts polyamide-epichlorohydrin crosslinker is then added. Then 160 parts of aluminum nitrate solution (solid content 1.4%) are slowly added to 1200 parts of emulsion. The coating had a solids content of 42%, a viscosity of 160 cps, a pH of 5.8 and a temperature of 78 ° F. The droplet size of the oil droplets is 2-10 μ. Finally, 220 parts of Formulation C were added to the coating composition to obtain a composition having a solid content of 41% and a viscosity of 130 cps.

The coating composition described in the above examples was applied to a laboratory air knife coater on a white paper substrate at a selected coating weight in the range of 4.8 to 5.2 g / m 2, and for coatings representative of the prior art. The compositions are similarly tested by similar application of coating weights within the same range. The result obtained by comparatively dissolving the composition of Example 3 and the composition of Example 3 is as follows.

1 color-forming agent release effect

A strip of the sheet containing the test coating is placed on a strip of the receiver sheet such that the developer coating and the test coating are in contact. The two overlapping strips are passed between steel calender rolls at a fixed pressure.

A densitometer reflectance meter is used to measure the area where no phase is formed on the receiver sheet, calendering for 60 seconds, and then similarly determine the area where the phase is formed on the receiver sheet.

In each case, the strength of the phase is calculated as follows.

(The smaller the intensity value of the phase, the stronger and stronger the phase)

Result phase strength

Coating composition of the prior art 50.0

Coating composition of Example 3 45.6

n = 4

2. Discoloration of coating composition

Reflectances of uncoated paper substrates and test coatings are measured with Minolta chromameter II. In each case a sheet layer consisting of six sheets is placed under the measuring tip, and the sheet of each sheet striatum is positioned with the sheet side to be measured facing the measuring tip.

result

TABLE 1

The "a" and "b" values obtained are shown in the accompanying drawings, in which the circle represents the uncoated paper, the square represents the coating of the prior art, and the triangle represents the coating of Example 3.

As shown in the results, the coating of Example 3 is closer to a white paper substrate than the coating of the prior art in (preferably) color.

The present invention can be embodied in other specific forms without departing from the scope and spirit of the invention. Accordingly, other aspects are within the scope of the following claims.

Claims (20)

Carboxymethylcellulose, polyvalent metal salts, wall-forming carboxylated acrylic resins, organic crosslinkers, spacer particles, and color-forming dyes dissolved in an oil solvent, the materials having a total non-aqueous total content in the composition of at least 30% by weight. And present in an amount sufficient to have a Brookfield viscosity at 78 ° F. of from about 50 to about 5000 cps and be applied to a substrate to produce a pressure-releasing color-forming agent. The composition of claim 1 wherein the degree of substitution of carboxymethylcellulose is from 0.65 to 1.8 and the viscosity as a 6% by weight aqueous solution is less than 170 cps. The composition of claim 1 wherein the organic crosslinker is polyamide-epichlorohydrin. The composition of claim 1 wherein the wall forming acrylic resin is a carboxylated copolymer of polyethylacrylate / methyl methacrylate. The composition of claim 1 wherein the viscosity is between 50 and 250 cps. The composition of claim 1 wherein the materials are present in an amount sufficient to provide a nonaqueous total content of the composition of at least 35% by weight and a Brookfield viscosity of 60 to 100 cps. The composition of claim 1, wherein the dye in the oil present in the composition is present in the oil in 3 to 12%. The composition of claim 1 wherein the degree of substitution of carboxymethylcellulose is from 1.1 to 1.5 and the viscosity as a 6% by weight aqueous solution is less than 170 cps. The composition of claim 1, wherein the composition ratio is as follows: Weight of material Metal salt 4.4-12.2 Carboxymethyl Cellulose 100 Acrylic Resin 50-200 Crosslinker 10-100 Dyes and Oils 100-1000 Spacer Particle 100-500 The composition of claim 1, wherein the composition ratio is as follows: Weight of material Metal salt 5-6 Carboxymethyl Cellulose 100 Acrylic resin 60-100 Crosslinker 60-100 Dyes and Oils 600-800 Spacer Particles 200-300 A pressure-sensitive recording material comprising a substrate on which one side of the adhesive and dried coating composition as defined in claim 1 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for Used as a pressure-sensitive recording material, comprising a substrate on which one surface of the adhesive and dried coating composition as defined in claim 2 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for Used as a pressure-sensitive recording material, comprising a substrate on which one side of the adhesive and dried coating composition as defined in claim 3 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for A pressure-sensitive recording material comprising a substrate on which one side of the adhesive, dried coating composition as defined in claim 4 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for A pressure-sensitive recording material comprising a substrate on which one side of the adhesive, dried coating composition as defined in claim 5 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for Used as a pressure-sensitive recording material, comprising a substrate on which one side of the adhesive, dried coating composition as defined in claim 6 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for A pressure-sensitive recording material comprising a substrate on which one side of the adhesive and dried coating composition as defined in claim 7 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for A pressure-sensitive recording material comprising a substrate on which one side of the adhesive and dried coating composition as defined in claim 8 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for A pressure-sensitive recording material comprising a substrate on which one side of the adhesive, dried coating composition as defined in claim 9 is disposed, having a coating weight of 3.00 g or more per square meter, wherein the color-forming substance is released upon pressurization. Coated sheet for Used as a pressure-sensitive recording material, comprising a substrate on which one side of the adhesive, dried coating composition as defined in claim 10 is disposed, having a coating weight of at least 3.00 g per square meter, and which color-forming substance is released upon pressurization. Coated sheet for

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