JP3276693B2 - Latex for paper coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a binder for paper coating.
As to latex. More specifically, the present invention relates to a paper coating latex as a binder necessary for obtaining a printing paper having good blocking resistance.

[0002]

2. Description of the Related Art In order to enhance the printing effect of printing paper, a coating liquid such as starch or poval is applied,
Application of inorganic pigments has been performed. However, when applying starch or poval, there are problems such as foaming at the time of work and solid content not being increased due to high viscosity. Therefore, latex is often used together,
Because of the inherent tackiness of latex, it can easily cause machine stains and cause problems such as sticking of coated paper.

When an inorganic pigment is applied, a latex is usually used in combination as a binder, and a flexible latex is required to increase the adhesive strength.
However, the flexible latex has the property that it easily sticks, and has the drawback that each part of the machine is stained in the coating process and the coated papers adhere to each other.

[0004]

Means for Solving the Problems In view of the above-mentioned circumstances, the present inventors have made intensive studies to solve the present problems, and as a result, have found that latex containing montanic acid wax (hereinafter abbreviated as wax) is used. It has been found that the use of the binder as a binder lowers the tackiness while maintaining the original adhesive strength of the latex, thereby leading to the present invention.

[0005] The montanic acid wax used in the present invention is a hard wax obtained by distillation or solvent extraction from asphalt-like lignite, and R-COOH
An acid wax represented by the formula: R-COO- (CH ₂ CH ₂ )
ester wax represented by n-OOC-R, R-CO
It means a partially saponified ester wax represented by O-Ca-OOC-R. R is usually 28 to 3
2 carbon atoms.

Further, the acid value and the saponification value differ depending on the acid wax, ester wax and partially saponified ester wax, but generally have the following numerical values. Acid value Saponification value (DIN53402) (DIN53401) Acid wax; 110 to 160 130 to 180 Ester wax; 5 to 100 50 to 170 Partially saponified ester wax; 5 to 50 70 to 120

In the present invention, a paraffin wax such as polyethylene wax, and a lubricant such as calcium stearate and ethylenebisstearylamide may be used in combination with the above-mentioned montanic acid wax as long as the effect is not impaired.

The method of adding the montanic acid wax to the latex is not particularly limited, and there is a method of emulsifying the montanic acid wax in advance and adding the emulsion to the latex.
Since it is preferable that the montanic acid wax is contained in the latex particles from the viewpoint of the effect of addition, a monomer or toluene, cyclohexane,
It is preferable to use a solvent previously dissolved in a solvent such as cyclohexene or to dissolve it in a solvent such as toluene, cyclohexane, or cyclohexene in advance, and then add the solvent to latex to swell and contain the latex particles.

In the present invention, the montanic acid wax is added in an amount of 0.1 to 100 parts by weight of the solid content of the latex for paper coating.
5 to 10 parts by weight,
If the amount is less than the weight part, the effect of improving the blocking resistance is inferior. On the other hand, if it exceeds 10 parts by weight, the decrease in the original adhesive strength of the latex will increase. The amount of the montanic acid wax is particularly preferably 1 to 6 parts by weight.

[0010] The latex to be used in the present invention is all latex used for paper coating, and the composition of the latex is not limited at all. In particular,
Examples thereof include butadiene-based latexes such as styrene-butadiene-based latex, carboxy-modified styrene-butadiene-based latex, and methyl methacrylate-butadiene-based latex. In particular, examples of the carboxylic acid used in the carboxy-modified styrene-butadiene-based latex include mono- or dicarboxylic acids such as acrylic acid, maleic acid, methacrylic acid, itaconic acid, and fumaric acid.

Further, in the above-mentioned butadiene-based latex, methyl methacrylate, butyl acrylate
Unsaturated carboxylic acid alkyl esters such as methacrylamide, glycidyl methacrylate and hydroxyethyl acrylate; unsaturated nitriles such as acrylonitrile and methacrylonitrile; and unsaturated amides such as acrylamide and methacrylamide as comonomers. It can also be used. Of course, some or all of styrene or butadiene can be replaced with other aromatic vinyls or other aliphatic conjugated diolefins. In particular, the latex in which the effects of the present invention are exhibited is a latex having high adhesiveness containing 35% by weight or more of an aliphatic conjugated diolefin.

In the polymerization of the latex, any addition method such as batch addition, continuous addition and divided addition of monomers may be used, and polymerization methods such as seed polymerization and two-stage polymerization may be employed. Further, known emulsifiers, polymerization initiators, molecular weight regulators and the like can be used.

[0013] The paper coating latex of the present invention may be applied alone as it is, mixed with starch or poval, and further coated with kaolin, calcium carbonate, satin white, as in the case of ordinary latex. ,titanium dioxide,
It is coated and used by mixing with an inorganic pigment such as aluminum hydroxide.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples in order to clarify the excellent effects of the present invention. It is not limited at all by the examples. In addition,
Parts and percentages shown in Examples and Comparative Examples are based on weight unless otherwise specified.

Production method of copolymer latex In a pressure-resistant autoclave, 95 parts of water, 0.6 parts of sodium dodecylbenzenesulfonate, 0.5 parts of t-dodecylmercaptan, 0.4 parts of sodium carbonate, After 0.8 part of ammonium sulfate was charged and sufficiently stirred, each monomer shown in Table 1 was added, and polymerization was performed at 65 ° C. for 10 hours. The conversion at the completion of the polymerization was 98%. Then
The pH of these copolymer latexes is adjusted with an aqueous solution of caustic soda.
8 to remove unreacted monomers by steam distillation,
Copolymer latexes a to g were obtained.

In the case of latex a to f, a predetermined amount of montanic acid wax (acid value 15 to 20, saponification value 130 to 1)
60 ester wax) was dissolved and dispersed in styrene in advance and then polymerized to be contained in the latex particles. Latex g does not contain wax. 15% of the above wax is added to this latex g in advance.
The latex obtained by adding the toluene solution dissolved in the above with stirring so that 2 parts of the wax is contained with respect to 100 parts of the solid content of the latex is designated as h. (Toluene swelling in the latex was removed by steam distillation.) Further, a montanic acid wax emulsion (acid value: 30 to 40, saponification value: 135 to 1) previously emulsified in latex g.
50 ester wax was emulsified in advance with a nonionic surfactant), and 100 parts of latex solids were mixed with 3 parts of the active ingredient.
And stirred for 2 hours to obtain latex i.

Example 1 Preparation of Coating Solution A 5% solution of poval (Kuraray 117) was cooked at 90 ° C. for 15 minutes, and then halved with latexes b, g, h, and i at a solid content ratio of each. Blend to become coating liquid 1-4
I got The solid content of the coating solution was adjusted to 8%.

Preparation of Coated Paper Each coating liquid was applied to a high quality paper having a basis weight of 85 g / m ^{2 with} a wire rod so that the coating amount was 3 g / m ² . After coating,
After drying in a 120 ° C. oven for 30 seconds, and then humidifying overnight in a constant temperature room, coated paper (1 to 4) corresponding to each coating liquid
I got

Test of coated paper Each coated paper sample was cut into a strip having a width of 3 cm, and 4
Paste the seed coated paper side by side. On top of this, filter paper is superimposed and passed through rolls using an RI printing machine and pressed. afterwards,
The adhesiveness of each coated paper is compared by observing the state of attachment of the fibers of the filter paper to the surface of each coated paper after removing the filter paper. Those having high adhesiveness were evaluated as "x", and as the evaluation became low, they were visually ranked as "O" and "O".

<Results> The tackiness of 1 and 3 coated with latex b and h containing wax inside the latex particles is clearly lower and improved as compared with latex g containing no wax. In addition, the latex i to which the wax emulsion is added is better than the latex g. (Table 2)

[Example 2] Preparation of coating liquid A coating liquid was prepared by the following coating composition . Kaolin 80 parts (solid content) Heavy calcium carbonate 20 ポ リ Sodium polyacrylate 0.2 〃 Caseisoda 0.15 〃 Starch oxide 5 〃 Latex 25 〃 (Solid content 63%) In the case of ordinary paint, latex Is about 10 parts (solid content), but in order to accelerate and expand the test results,
It was made up to 5 parts (solid content). Latex a
To i, the paint was created, but each paint was
To 13.

Preparation of Coated Paper A commercially available high-quality paper (basis weight 85 g / m ² ) was coated using a wire rod under the following conditions and dried to obtain a coated paper. Co - DOO weight 18 g / m ² Drying conditions 0.99 ° C. o - 30 seconds Drying humidity thermostatic chamber C. in oven (20 ℃, 60% RH) after overnight humidity at, 55 ° C. des - Pa - Calendar - over To obtain a smooth coated paper. Latex a to i paints 5 to 13
The coated papers prepared by coating are coated papers 5 to 13 respectively.
And

Test of Coated Paper Each coated paper sample is cut into a strip having a width of 3 cm, and the coated surfaces are combined and pressed by a press capable of heating. Thereafter, the peel strength was measured with an Instron tensile tester, and the adhesive strength was determined. The conditions for press-bonding with a press were appropriately changed so as to show a difference. However, since the influence of the temperature was great, two conditions of room temperature and 50 ° C. were used.

<Results> As shown in Table 3, the peel strengths of the wax-containing latexes a to f, h, and i were lower than those of the latex g, indicating that the tackiness was improved. Even when the pressing temperature is increased to 50 ° C., although the general tendency that the latex containing a large amount of butadiene has poor adhesion remains, the peel strength is lower than that of the latex g containing no wax, and the adhesiveness is improved. Can be From the results of the latexes b, e, f, h, and i, swelling the wax in the latex particles is more effective than blending the wax emulsion, in other words, it is used to obtain the same level of improvement. It can be seen that a small amount of wax is required.

[0025]

[Table 1]

[0026]

[Table 2]

[0027]

[Table 3]

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-211394 (JP, A) JP-A-56-148997 (JP, A) JP-A-57-117337 (JP, A) JP-A-60-1985 135462 (JP, A) JP-A-55-94983 (JP, A) JP-B-46-42986 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27 / 42

Claims (1)

(57) [Claims] (1) 0.5 to 10 parts by weight of montanic acid wax per 100 parts by weight of solid content of diene rubber latex
Latex for paper coating characterized by being present in latex particles .