JP3345979B2 - Latex for web offset printing paper and composition for web offset printing paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for coating web offset printing paper and a latex used in the composition. More specifically, the present invention relates to a composition for coating a rotary offset printing paper for obtaining a coated paper excellent in adhesive strength and blister resistance and excellent in their balance, and a latex used in the composition.

[0002]

2. Description of the Related Art In recent years, with the rapid development of web offset printing technology, the performance required for coated paper has also become strict, for example, improving both inconsistent properties of adhesive strength and blister resistance. In addition, there is a need for a composition for coating web offset printing paper to obtain a coated paper having a good balance. As the latex used for the offset rotary printing paper coating composition, a latex having a low gel content is generally used. As a method for adjusting the gel content of the latex, a method is known in which a monomer is polymerized in the presence of a chain transfer agent such as t-dodecyl mercaptan and α-methylstyrene dimer. However, the coated paper obtained by coating the latex obtained by this method has an insufficient balance between adhesive strength and blister resistance, and does not sufficiently satisfy the above requirements.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an offset rotary printing paper coating for improving both the contradictory properties of adhesive strength and blister resistance and obtaining a coated paper having a good balance. An object of the present invention is to provide a working composition and a latex used therein. The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that the present object can be achieved by using a specific compound as a chain transfer agent and using a latex obtained by emulsion polymerization. The present invention has been completed.

[0004]

Thus, according to the present invention, 15 to 50% by weight of an aliphatic conjugated diene monomer, 1 to 6% by weight of an ethylenically unsaturated carboxylic acid monomer and copolymers thereof are available. A latex of a copolymer having a gel content of 15 to 65% by weight, obtained by emulsion polymerization of a monomer comprising 44 to 84% by weight of a suitable ethylenically unsaturated monomer in the presence of a chain transfer agent. And a chain transfer agent obtained by using a tertiary mercaptan having at least one tertiary butyl group and having 7 to 16 carbon atoms in total. Latex is provided. Further, according to the present invention, there is provided a composition for coating an offset rotary printing paper containing the latex and the pigment as essential components.

The latex for web offset printing of the present invention uses a tertiary mercaptan having at least one tertiary butyl group and a total number of carbon atoms of 7 to 16 as a chain transfer agent. And those obtained by emulsion polymerization of a monomer comprising an aliphatic conjugated diene monomer, an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated monomer copolymerizable therewith.

[0006] The chain transfer agent used in the present invention is a tertiary mercaptan having at least one tertiary butyl group. The total number of carbon atoms of the chain transfer agent used in the present invention is 7 to 16, preferably 10 to 13.

Specific examples of the chain transfer agent used in the present invention include 2,5,5-trimethylhexane-2-thiol,
2,2,4,6,6-pentamethylheptane-4-thiol, 2,2,4,4,6-pentamethylheptane-6
-Thiol, 2,2,4,6,6,8,8-heptamethylnonane-4-thiol, 2,2,5,8,8-pentamethylnonane-5-thiol, 2,2,5,5 , 6,
8,8-heptamethylnonane-6-thiol and the like.

The amount of the chain transfer agent to be used is generally 0.05 to 4 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of all monomers. If it exceeds 4 parts by weight, the adhesive strength of the coated paper may decrease, and if it is less than 0.05% by weight, the blister resistance of the coated paper may decrease.

In the present invention, in addition to the chain transfer agent,
Other compounds having a chain transfer effect can be used in combination as needed.

Other compounds having a chain transfer effect include n-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan (containing no tertiary butyl group), n-hexadecyl mercaptan, and n-tetradecyl. Mercaptan, 2,2,4,6,6-pentamethylheptane-4-methylenethiol, 2,4,6-
Mercaptans such as trimethylnonane-4-thiol;
Xanthogen disulfides such as dimethylxanthogen disulfide, diethylxanthogen disulfide, diisopropylxanthogen disulfide; thiuram disulfides such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide; halogenated hydrocarbons such as carbon tetrachloride and ethylene bromide; pentaphenyl Hydrocarbons such as ethane; α, β-unsaturated aldehydes such as acrolein and methacrolein; allyl alcohol; 2-ethylhexylthioglycolate; terpinolene, α-terpinene, β
-Terpenes such as terpinene, γ-terpinene and dipentene; α-methylstyrene dimers such as 2-4-diphenyl-4-methyl-1-pentene; and 2,5-dihydrofuran. Among these compounds, t-dodecyl mercaptan, terpene and α-methylstyrene dimer are preferably used. The amount of t-dodecyl mercaptan is usually 0.05 to 100 parts by weight of all monomers.
To 3 parts by weight, preferably 0.1 to 1.5 parts by weight,
The amount of the terpene or α-methylstyrene dimer is usually 0.1 to 3 parts by weight, based on 100 parts by weight of all monomers.
Preferably it is 0.5 to 1.5 parts by weight.

The aliphatic conjugated diene monomer used in the present invention includes 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3 -Pentadiene, chloroprene and the like.

The ethylenically unsaturated carboxylic acid monomer used in the present invention includes acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and monoethyl maleate.

The monomers copolymerizable with the aliphatic conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, Aromatic vinyl monomers such as halogenated styrene; cyano group-containing ethylenically unsaturated monomers such as acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile; methyl (meth) acrylate; Ethylenically unsaturated carboxylic esters such as ethyl (meth) acrylate, butyl (meth) acrylate and dibutyl maleate; and ethylenically unsaturated amides such as (meth) acrylamide and N-methylol (meth) acrylamide. These monomers are used in an appropriate combination in order to improve coated paper properties such as adhesive strength and inking property.

The amount of each monomer used in the present invention is such that the aliphatic conjugated diene monomer is 15 to 100 parts by weight of the total monomer.
50% by weight, preferably 20-45% by weight, 1-6% by weight of ethylenically unsaturated carboxylic acid monomer, preferably 1.5-5% by weight, and 4% by weight of a monomer copolymerizable therewith.
It is 4 to 84% by weight, preferably 50 to 78.5% by weight. Outside of these ranges, coated paper properties such as adhesive strength and inking property may be reduced.

The latex for offset rotary printing paper coating of the present invention has a gel content of a copolymer constituting the latex of 15 to 15.
It is 65% by weight, preferably 20 to 60% by weight. Fifteen
If it is less than 50% by weight, the adhesive strength of the coated paper is low, and
If the content is more than 10% by weight, the blister resistance of the coated paper decreases.

The latex for coating an offset rotary printing paper of the present invention is obtained by emulsion polymerization of the above monomers in the presence of the above chain transfer agent. The chain transfer agent is added to the reactor all at once before the start of the polymerization, or all at once, dividedly or continuously added after the start of the polymerization. In the case of divided addition or continuous addition, the addition amount can be uniform or constant, and can be changed according to the progress of polymerization. Further, the chain transfer agent may be added alone as it is, a monomer,
It may be mixed with or dissolved in water, an auxiliary polymer material or an organic solvent.

[0017] The composition for coating web offset printing paper of the present invention comprises the latex for coating web offset printing paper of the present invention and a pigment as essential components.

The pigment used in the present invention is a powdery substance generally used for paper coating. Specific examples thereof include inorganic pigments such as clay, calcium carbonate, talc, titanium oxide, and satin white; and organic pigments such as plastic pigment.

The ratio of the pigment to the latex for web offset printing is usually 5 to 100 parts by weight of the pigment for latex for web offset printing (solid content).
30 parts by weight, preferably 7 to 20 parts by weight.

Further, the composition for coating a web offset printing paper of the present invention may further comprise, if necessary, other latex binders,
It may contain a dispersant, a water-soluble polymer, a waterproofing agent, an antifoaming agent, a dye, a lubricant, and the like.

The composition for coating webs of offset rotary printing of the present invention is used by applying it to a base paper for web offset printing.
The method of application is not particularly limited, and the application is performed using an application device such as a blade coater, a roll coater, an air knife coater, and a short dwell coater. The coating amount is usually 3 to 30 g in terms of solid content of the composition.
/ M ² , preferably 5 to 20 g / m ² .
Further, it is preferable that each of the compositions is dried after being applied.

[0022]

According to the present invention, it is possible to obtain an offset rotary printing coated paper which has both good adhesive strength and blister resistance and is excellent in their balance.

[0023]

The present invention will be described below in more detail with reference to examples. The parts and percentages in the examples are on a weight basis.

The latex and the coated paper obtained by coating the paper coating composition containing this latex as a main component were evaluated according to the following method. (Evaluation of latex) Gel content After adjusting the pH of latex to 8.0, it was cast on a glass plate with a frame and dried at 100 ° C. under reduced pressure to obtain a film. 0.5 g of this film was placed in a basket of 80 mesh wire mesh, and was placed in a tetrahydrofuran 100 m at 20 ° C.
After immersion for 24 hours in l, the film remaining in the basket of the wire mesh was dried under reduced pressure at 100 ° C., and the residual ratio was calculated to determine the gel content. Average particle size Observed with an electron microscope, the particle size of
Zero was measured and the number average was shown.

(Evaluation of Coated Paper) Dry Pick Strength After the printing ink (tack value: 14) was overprinted four times on the coated paper using an RI tester (manufactured by Akashi Seisakusho), the paper surface was peeled off (picking). Was observed and evaluated by the 5-point method.
The higher the score, the higher the dry pick. Wet pick strength After applying water to the coated paper using a Molton roll, RI
Using a tester (manufactured by Akashi Seisakusho), the printing ink (tack value: 20) was applied four times, and then evaluated by a five-point method in the same manner as in the evaluation method of dry pick strength. The higher the score, the higher the wet pick. Blister resistance After the coated paper was conditioned to about 6%, it was thrown into a heated oil bath and indicated by the minimum oil bath temperature at which blisters were generated.

Example 1 35 parts of 1,3-butadiene, 42 parts of styrene, 15 parts of methyl methacrylate, 5 parts of acrylonitrile, 1 part of acrylic acid, 2 parts of itaconic acid, 2,2,4,6,6-pentamethyl One part of heptane-4-thiol and 0.5 part of sodium dodecylbenzenesulfonate were added to 50 parts of soft water and mixed with stirring to obtain a monomer emulsion. Separately, put 34 parts of soft water and 0.5 parts of potassium persulfate in an autoclave equipped with a stirrer.
And 1 part of sodium dodecylbenzenesulfonate were charged and heated to 80 ° C., and then 10% of the monomer emulsion was added to an autoclave and reacted for 1 hour. Next, after adding 1.0 part of potassium persulfate and 20 parts of soft water to the autoclave, the remaining monomer emulsion was added to the reactor over 4 hours. During this time, the autoclave was kept at 80 ° C. After the addition of the monomer emulsion, the mixture was reacted at 80 ° C. for further 4 hours. Then, steam was blown to remove unreacted monomers, cooled to room temperature, and a 20% aqueous sodium hydroxide solution was added. The pH was adjusted to 8 to obtain a polymer latex A of the present invention having a solid content of 50%. Table 1 shows the evaluation results of this latex.

Next, 70 parts of kaolin clay (UW90, manufactured by Engelhard), 30 parts of calcium carbonate (Escalon # 2000, manufactured by Sankyo Flour Milling Co., Ltd.), and 0.15 part of a dispersant (Alon T-40, manufactured by Toagosei Co., Ltd.) , Sodium hydroxide 0.15 part, oxidized starch 3 parts and polymer latex A
10 parts (solid content) were mixed and stirred to obtain a solid content of 65%.
%, A paper coating composition having a pH of 9.5. This composition was applied to a base paper so that the coating amount was 12 g / m ² per one side, and immediately after the application, dried with hot air at 140 ° C. for 4 seconds,
° C, 65% R.C. H. Was left overnight in a constant temperature and humidity room. Thereafter, a super calender treatment was performed twice at a temperature of 40 ° C. and a linear pressure of 40 kg / cm.

Examples 2-6 and Comparative Examples 1-2 Polymer latexes B-H were obtained in the same manner as in Example 1 except that the formulations shown in Tables 1 and 2 were used. These latexes were evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2. Further, using polymer latexes B to H, a coating composition was obtained in the same manner as in Example 1, and a coated paper was obtained. These coated papers were evaluated in the same manner as in Example 1, and the results are shown in Tables 1 and 2.

[0029]

[Table 1]

[0030]

[Table 2]

From Tables 1 and 2, at least one third
When a chain transfer agent other than a tertiary mercaptan having a tertiary butyl group and a total number of carbon atoms of 7 to 16 is used (Comparative Examples 1 and 2), the dry pick strength, the wet pick strength, and the blister resistance It turns out that the property is low. on the other hand,
When a tertiary mercaptan having at least one tertiary butyl group and having 7 to 16 total carbon atoms is used (Example), dry pick strength, wet pick strength and blister resistance are obtained. Are high and the balance is good.

Claims (2)

(57) [Claims] 1 to 15% by weight of an aliphatic conjugated diene monomer, 1 to 6% by weight of an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated monomer copolymerizable therewith.
A latex of a copolymer having a gel content of 15 to 65% by weight, obtained by emulsion polymerization of a monomer consisting of ８４84% by weight in the presence of a chain transfer agent. A latex for web offset printing paper obtained by using a tertiary mercaptan having a tertiary butyl group and having a total number of carbon atoms of 7 to 16. 2. An offset rotary printing paper coating composition comprising the latex for offset rotary printing paper coating according to claim 1 and a pigment as essential components.