JPH0121278B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition for paper, and particularly to a coating composition for paper that can greatly improve the whitening effect when improving the whiteness of coated paper. It is well known that the whiteness of the resulting coated paper is improved by incorporating a water-soluble fluorescent white dye into a paper coating composition containing a pigment and an aqueous binder as main components. It is also known that by incorporating water-soluble hydroxyethylcellulose together with a water-soluble fluorescent white dye, the whitening effect and level dyeing properties can be improved (Japanese Patent Laid-Open No. 54-55612).
Publication No.). However, in such paper coating compositions, a large amount of water-soluble hydroxyethylcellulose must be used to obtain a sufficient whitening effect; This causes a significant increase in the viscosity of paper coating compositions whose main components are pigments containing white dyes and aqueous binders, and this is further accelerated by aging, heating, etc., and can cause serious troubles during actual use. Become. In view of this, the present inventors have made various studies to improve the drawbacks of the known paper coating compositions, and have also developed a dehydrated condensate of polyalkylene polyamine and dibasic carboxylic acid, or a polyalkylene polyamine. A polyamide polyurea (hereinafter referred to as a specific polyamide polyurea) obtained by reacting a dehydrated condensate of a polyamine and a dibasic carboxylic acid produced by a deammonification reaction with urea and urea. By blending the reaction product with formaldehyde, it is not only possible to reduce the viscosity of the resulting paper coating composition, but also
It has been discovered that very excellent effects can be obtained in terms of whitening effect and leveling properties, leading to the present invention. That is, the present invention provides a paper coating composition which mainly contains a pigment and an aqueous binder, and further contains a reaction product of a specific polyamide polyurea and formaldehyde, a water-soluble hydroxyethyl cellulose, and a water-soluble fluorescent white dye. This is what we provide. The whitening effect obtained with the paper coating composition of the present invention,
The level dyeing effect is much better than when water-soluble hydroxyethyl cellulose alone is used in combination with water-soluble fluorescent white dye, and in order to obtain the same effect, the amount of water-soluble hydroxyethyl cellulose contained must be greatly increased. As a result, troubles such as an increase in the viscosity of the coating composition can be avoided. At the same time, due to the action of the reaction product between a specific polyamide polyurea and formaldehyde, coated paper treated with the paper coating composition of the present invention has significantly improved water resistance of the coated layer and improved ink receptivity. It also has desirable properties as a coated paper for printing, such as improving effects. The reaction product of polyamide polyurea and formaldehyde is already used for the purpose of imparting water resistance to coated paper, but it is also used for the purpose of brightening and leveling coated paper that undergoes fluorescent whitening. This method of use was previously unknown, and was discovered for the first time by the present inventors' discovery of a synergistic effect with water-soluble hydroxyethyl cellulose. In addition to reaction products of specific polyamide polyurea and formaldehyde, condensates of melamine and formaldehyde, dialdehydes such as glyoxal, epoxy compounds, and polyvalent metal salts such as zirconium are also used for the purpose of improving water resistance. However, these water resistant agents do not have a synergistic whitening or leveling effect with water-soluble hydroxyethyl cellulose, or even cause a decrease in whiteness, and the reaction between certain polyamide polyureas and formaldehyde. It is surprising that only the products have a specific synergistic brightening, leveling effect. The polyamide polyurea in the present invention is a dehydrated condensate of a polyalkylene polyamine and a dibasic carboxylic acid, or a dehydrated condensate of a polyamine and a dibasic carboxylic acid produced by a deammonization reaction of a polyalkylene polyamine and urea. It can be obtained by deammonization reaction with Examples of the polyalkylene polyamine mentioned here include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, iminobispropylamine, and 3-azahexane-1,6-diamine. These polyalkylene polyamines can be used alone or as a mixture of two or more. Examples of dibasic carboxylic acids include aliphatic carboxylic acids such as succinic acid, glutaric acid, adipic acid, maleic acid, sebacic acid, and fumaric acid, and aromatic carboxylic acids such as isophthalic acid and terephthalic acid. The reaction between a specific polyamide polyurea and formaldehyde can be carried out under alkaline or acidic conditions. The amount of each component in the paper coating composition of the present invention is per 100 parts by weight of the pigment in the coating composition mainly consisting of a conventional pigment and a water-soluble binder. amount i.e. about 0.05
~0.5 part by weight, and the reaction product of a specific polyamide polyurea and formaldehyde is about 0.05 part by weight.
~3 parts by weight, preferably 0.1 parts by weight or more, and 0.1 parts by weight or more of water-soluble hydroxyethyl cellulose. Pigments in the paper coating composition of the present invention include white inorganic pigments such as kaolin clay, talc, titanium dioxide, aluminum hydroxide, calcium carbonate, satin white, and barium sulfate, and white pigments mainly containing polystyrene, urea resin, etc. Examples include organic pigments, and examples of aqueous binders include oxidized starch, modified starch, polyvinyl alcohol,
Examples include water-soluble binders such as casein and gelatin, and water emulsion and dispersion binders such as styrene/butadiene synthetic resins, vinyl acetate synthetic resins, ethylene/vinyl acetate synthetic resins, methyl methacrylate, and butadiene synthetic resins. Each of these can be used alone or in combination in any proportion. In addition, water-soluble fluorescent white dyes are commonly used for fluorescent whitening of cellulose fibers such as cotton and rayon, as well as paper and pulp, and a typical example is diaminostilbendisulfonic acid derivatives. For example, whitex (Sumitomo Chemical)
Examples include those commercially available under trade names such as kayaphar (Nippon Kayaku). The paper coating composition of the present invention contains the above-mentioned pigment, a water-based binder, a water-soluble fluorescent white dye, a water-soluble hydroxyethyl cellulose, and a reaction product of a specific polyamide polyurea and formaldehyde as essential components. However, if necessary, auxiliary agents such as dispersants, viscosity modifiers, antifoaming agents, preservatives, and release agents, as well as a small amount of dye called a blue tint imparting agent, etc., may be added. This does not impede the effectiveness of the invention. The paper coating composition of the present invention is coated onto a paper substrate using a conventional method such as a blade coater, an air knife coater, a size press coater, a roll coater, etc., and is then dried as required. Coated paper with excellent whitening effect and level dyeing properties can be obtained by performing gloss finishing treatment according to the conditions. The present invention will be explained below with reference to Examples. In addition, "Example Middle" and "%" indicate weight units. The measurement tests and evaluation methods are as follows. (1) Viscosity of coating composition B-type viscometer, 60 rpm, measurement temperature 25℃ (2) Whiteness of coated paper (a) Whiteness Whiteness according to the A.BERGER whiteness formula, the higher the value, the whiter it is. Good (b) Whiteness under natural light Observe with the naked eye in accordance with the observation and lighting conditions of JISL0801-1978 General Rules for Color Fastness Testing. Judgment: Excellent ←――――――→ 54321 Poor (c) Whiteness under black light Observation with naked eye under ultraviolet light Judgment: Excellent ←――――――→ 54321 Poor (3) Level staining of coated paper Observe with the naked eye under an ultraviolet light Judgment: Excellent ←――――――→ 54321 Poor (4) Water resistance of coated paper (a) Wet Rub method Drop approximately 0.1ml of water onto the coated surface and rub it with your fingers. Transfer the eluate to black paper, and visually observe and evaluate the amount of elution. Judgment: Excellent ←――――――→ 54321 Poor (b) Wet pick method Using a PI tester (manufactured by Mei Seisakusho Co., Ltd.), the coating surface was moistened with a water supply roll and then printed.
Visually observe and evaluate whether the coating layer has fallen off or is damaged. Judgment: Excellent ←――――→ 54321 Poor (5) Ink receptivity of coated paper Printing was performed as shown below using an RI tester, and the ink receptivity was observed and judged with the naked eye. Judgment: Excellent ←――――→ 54321 Poor (A) Method A Drop water into the ink that is being mixed in and print after mixing. (b) Method B The surface to be coated is pre-wetted with a water supply roll and then printed. Example 1 (Synthesis of reaction product A of polyamide polyurea and formaldehyde) 292 g of triethylenetetramine and 60 g of urea were placed in a four-necked flask equipped with a thermometer, reflux condenser, and stirring bar.
The reaction was carried out at 145 to 150°C for 4 hours while removing the generated ammonia from the system, and then 146 g of adipic acid was added, and the condensation reaction was carried out at 150 to 155°C for 5 hours. Urea after cooling to 120℃
240 g was added and ammonia removal reaction was carried out at 125-130°C for 2 hours. Then, gradually add 1350g of water.
An aqueous solution of polyamide polyurea was obtained. Next, 202.5 g of 37% formalin was added, and the pH was adjusted to 5 with concentrated hydrochloric acid, followed by stirring at 65° C. for 4 hours. Thereafter, it was cooled to 30° C., and the pH was adjusted to 8 with a 30% aqueous solution of caustic soda to obtain an aqueous solution of a reaction product of polyamide polyurea and formaldehyde with a solid content of 30%. This is called reaction product A.
(Preparation and measurement of coating compositions for paper and coated paper) Coating compositions for paper having the formulation shown in Table 1 were prepared, and the viscosity and stability of each coating composition and the coating composition were measured. The whiteness, level dyeing properties, etc. of the coated paper obtained by coating were observed and measured, and the results shown in Table 2 were obtained. The coating composition was applied to the paper base by hand using a wire rod at a coating density of about 20 g/m ² on one side, and after drying, calendering was performed.

【table】

【table】

[Table] Example 2 A coating composition consisting of the basic formulation shown in Table 3 was added with water-soluble hydroxyethyl cellulose or some water-soluble polymers commonly used in paper coating compositions and the coating composition obtained in Example 1. A coated paper was prepared in the same manner as in Example 1 using the coating composition obtained by adding the reaction product A. The whiteness and level dyeing properties of the coated paper obtained were as shown in Table 4.

【table】

【table】

[Table] Example 3 (Synthesis of reaction product B of polyamide polyurea and formaldehyde) 146 parts of triethylenetetramine and 146 parts of adipic acid were added to the same experimental apparatus as in the synthesis example of reaction product A in Example 1. Prepare, heat up while stirring,
The reaction was carried out at 150 to 155°C for 4 hours, dehydrated, cooled to 120°C, 120 parts of urea was added, and 130 parts of urea was added.
The mixture was stirred at ~135° C. for 3 hours to carry out the deammonia reaction. Then gradually add 800g of water.
An aqueous solution of polyamide polyurea was obtained. Next, add 162 parts of 37% formalin and add 10N−
The pH was adjusted to 10.3 with NaOH. Then 60-63℃
After keeping warm for 2 hours, cool to 30℃ and pH with concentrated hydrochloric acid.
was adjusted to 7.8 to obtain an aqueous solution of a reaction product of polyamide polyurea and formaldehyde with a solid content of 30%. This is called reaction product B. (Preparation and measurement of coating composition for paper and coated paper) Several waterproofing agents used to impart water resistance to the coating layer are added to the coating composition with the basic formulation shown in Table 5. Coated paper was prepared in the same manner as in Example 1 using the coating composition obtained. The performance of the obtained coated paper is shown in Table 6.

【table】

【table】

[Table] *6: Initial condensate of melamine and formaldehyde manufactured by Sumitomo Chemical *7: Water-soluble polyepoxy compound manufactured by Nagase Sangyo Co., Ltd.

Claims (1)

[Claims] 1 A dehydration condensation product of a polyalkylene polyamine and a dibasic carboxylic acid, which is mainly composed of a pigment and an aqueous binder, or a dehydration condensation of a polyamine and a dibasic carboxylic acid produced by a deammoniation reaction of a polyalkylene polyamine and urea. A paper coating composition comprising a reaction product of formaldehyde and a polyamide polyurea obtained by reacting a polyurea with urea through a deammoniation reaction, a water-soluble hydroxyethyl cellulose, and a water-soluble fluorescent white dye.