JP4306361B2 - Surface sizing agent for newsprint and newsprint - Google Patents

Description

  The present invention relates to a newsprint paper surface sizing agent and newsprint paper coated with the same.

  In order to meet the recent demand for high-speed, large-scale printing and multi-color printing, the newspaper printing system is rapidly changing from the conventional relief printing system to the offset (flat printing) printing system.

However, in the offset printing system, as is well known, dampening water is also supplied to newsprint during printing, so the paper absorbs water and the paper surface becomes sticky and sticks to the printing cylinder (blanket cylinder). (Rewetting tackiness) phenomenon occurs, and the equipment may become soiled or the printing surface may be disturbed due to pulp peeling, and in severe cases, the paper may tear.

Therefore, normally, the paper is sized to control the water absorption of the paper, but the method of adding chemicals to the pulp slurry like the internally added size has a poor yield of chemicals on the pulp, so the desired size effect is achieved. A large amount of sizing agent is required to obtain, which is disadvantageous in cost. Further, when DIP (deinked pulp), for which demand has been increasing in recent years, is used, there is a problem that the size effect is difficult to be exhibited due to poor paper quality. If the size effect is low, printability such as ink fillability deteriorates, and disadvantages such as image quality deterioration occur.

Therefore, in this field, there is a movement to replace the internal sizing agent with the surface sizing agent. Since the surface sizing agent yields almost 100% on the paper surface, it is possible to exert a size effect efficiently and is advantageous in terms of cost, and operations such as fluctuations in the size effect due to papermaking stains and papermaking temperature. There are various advantages that the above problems are few.

Various types of surface sizing agents are already known. For example, a surface sizing agent containing a copolymer of styrene / ethylenically unsaturated carboxylic acid monomer / ethylenically unsaturated carboxylic acid ester monomer. Has been proposed (see, for example, Patent Document 1). However, this has a problem that the size effect is good, but the Neppari is strong, and since styrene is used, foaming easily occurs when the sizing agent is applied.

Therefore, it is also possible to use a copolymer composed of an ethylenically unsaturated carboxylic acid monomer / ethylenically unsaturated carboxylic acid ester monomer (see, for example, Patent Document 2) as a surface sizing agent except for styrene. Although this can suppress neppari, it has a problem that the size effect is weak.

JP 60-185894 A JP 11-315493 A

  The problem to be solved by the present invention is to provide a surface sizing agent for newsprint paper that has a good balance between a good sizing effect and suppression of nippari at the time of offset printing, and has less foaming during coating.

  In order to solve the above-mentioned problems, the present applicant has made extensive studies focusing on the water-soluble copolymer described in Patent Document 1, and as a result, has obtained an ethylenically unsaturated carboxylic acid monomer and an ethylenically unsaturated group. It has been found that a surface sizing agent for newsprint that can solve the above-mentioned problems can be obtained by using a water-soluble copolymer using a carboxylic acid ester monomer in a specific ratio.

That is, the present invention is configured ethylenically unsaturated carboxylic acid monomers 4 5-60 wt%, the ethylenically unsaturated carboxylic acid ester monomer 5 5 to 40% by weight comprising (meth) butyl acrylate component And a water-soluble copolymer having a weight average molecular weight of 20,000 to 50,000, which is polymerized in the presence of an alkyl mercaptan chain transfer agent of 0.25 to 5% by weight based on the total amount of both monomers. The present invention relates to a surface sizing agent for newsprint, characterized by containing a coalesced (A) as a main component.

  According to the surface sizing agent for newsprint according to the present invention, it is possible to impart high sizing properties to newsprint, and it is possible to suppress the newsprint of newsprint during offset printing. Moreover, since there is little foaming at the time of sizing agent coating, operativity can be made favorable.

  The ethylenically unsaturated carboxylic acid monomer constituting the copolymer (A) can be used without particular limitation as long as it has a carboxyl group or a salt thereof in the molecule. For example, (meth) acrylic acid (acrylic acid) Or monocarboxylic acid such as maleic acid, itaconic acid, citraconic acid, fumaric acid, muconic acid, or the anhydride thereof, as well as sodium and potassium salts thereof. Alkali metal salts, alkaline earth metal salts, ammonium salts, and salts of organic bases. Two or more of these may be used in combination.

Specific examples of the ethylenically unsaturated carboxylic acid ester monomer include various alcohol esters and half esters of the ethylenically unsaturated carboxylic acid monomer, and the substituent of the ester has 1 carbon atom. A linear, branched or cyclic alkyl group of about ˜18 can be exemplified, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate (n-propyl, iso-propyl) , (Meth) butyl acrylate (n-butyl, iso-butyl, tert-butyl), neopentyl (meth) acrylate, hexyl (meth) acrylate (n-hexyl, cyclohexyl, 2-ethylhexyl, etc.), (meth) Examples thereof include decyl acrylate, palmityl (meth) acrylate, and stearyl group (meth) acrylate. In the present invention, the ethylenically unsaturated carboxylic acid ester monomer is butyl (meth) acrylate, particularly (meta), because it is easy to balance the size effect, suppression of neppari, and suppression of foaming at the time of sizing agent coating. ) Essentially contains n-butyl acrylate . Moreover, it is preferable to use together n-butyl acrylate and n-butyl methacrylate, and the use amount range of both in this case is 0.3-weight ratio of n-butyl acrylate / n-butyl methacrylate. It is about ~ 0.6.

The copolymer (A) needs to contain 45 to 60% by weight of the ethylenically unsaturated carboxylic acid monomer in the molecule, and also contains the ethylenically unsaturated butyl (meth) acrylate. It is necessary to contain 55 to 40% by weight of a carboxylic acid ester monomer . Ethylenically it becomes obtained as a high sizing effect by incorporating the unsaturated carboxylic acid monomer 4 5 wt% or more, tends to more Neppari When the monomer is more than 60 wt% is too strong .

Further, other polymerizable monomers may be used as necessary as a constituent of the copolymer (A) as long as the object of the present invention is not deviated and the effect can be maintained. Examples of the polymerizable monomer include vinyl esters such as (meth) acrylamide, vinyl acetate, and vinyl propionate, α-olefins having 6 to 22 carbon atoms, alkyl vinyl ethers having 1 to 22 carbon atoms, and nonions such as vinyl pyrrolidone. And unsaturated unsaturated monomers. The amount of the polymerizable monomer used is usually about 10% by weight or less in the copolymer (A) molecule.

  The copolymer (A) can be produced by various known polymerization methods. Specific examples include emulsion polymerization. In a reaction vessel equipped with an appropriate heating device and stirrer, an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated carboxylic acid ester monomer, and other polymerizations as required. The monomer is charged in predetermined amounts, then water and various known emulsifiers are charged into the container, and these monomers are emulsified and dissolved. Furthermore, what is necessary is just to add a well-known polymerization initiator and a chain transfer agent, to heat at about 20-120 degreeC, and to carry out emulsion polymerization over about 2 to 12 hours under stirring.

  Examples of the production method other than the emulsion polymerization method include solution polymerization. Specifically, an ethylenically unsaturated carboxylic acid monomer, an ethylenically unsaturated carboxylic acid ester monomer, and other polymerizable monomers as required, in a reaction vessel equipped with a suitable heating device and a stirrer In a predetermined amount, and then water and an organic solvent are added to the container. Further, a known polymerization initiator and chain transfer agent are added, heated to about 20 to 120 ° C., and stirred for 2 to 12 hours. What is necessary is just to superpose | polymerize. In addition, it is preferable to manufacture a copolymer (A) by the said emulsion polymerization from a viewpoint of the size effect of the surface sizing agent for newspapers which concerns on this invention, and Nepari suppression.

  Examples of the organic solvent include alcohols such as ethyl alcohol and propyl alcohol; aromatic hydrocarbons such as benzene and toluene; lower ketones such as acetone and methyl ethyl ketone; ethyl acetate, chloroform and dimethylformamide. However, in view of environmental load and work hygiene, it is desirable to distill off these organic solvents by distillation under reduced pressure or the like.

  Examples of the emulsifier include nonionic surfactants, anionic surfactants, cationic surfactants, and amphoteric surfactants. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, sorbitan alkyl ester, polyoxyethylene sorbitan alkyl ester and oxyethyleneoxypropylene block copolymer. Two or more of these may be used in combination. Examples of the anionic surfactant include alkyl sulfonates, alkyl sulfo fatty acid ester salts, dialkyl sulfosuccinic acid esters, polyoxyalkylene alkyl ether sulfosuccinic acid monoester salts, polyoxyalkylene alkenyl ether sulfosuccinic acid monoester salts, and polyoxyalkylenes. Aryl ether sulfosuccinic acid monoester salt, alkyl diphenyl ether disulfonate, sulfated oil, sulfated fatty acid ester salt, alkyl sulfate ester salt, alkenyl sulfate ester salt, polyoxyalkylene alkenyl ether sulfate ester, polyoxyalkylene aryl ether sulfate ester Salt, alkyl phosphate ester salt, polyoxyalkylene alkyl ether phosphate ester salt, polyoxyalkylene alkenyl Terurin acid ester salts, polyoxyalkylene aryl ether phosphoric acid ester salts and the like can be exemplified. Two or more of these may be used in combination. In addition, as the cationic surfactant, a hydrophilic group is a primary to quaternary ammonium group, a pyridinium group, or the like. Specifically, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, behenyltrimethylammonium chloride, chloride Octadecyltrimethylammonium chloride, hexadecyltrimethylammonium chloride, dodecyltrimethylammonium chloride, dioctyldimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, myristyldimethylbenzylammonium chloride, stearyldimethylbenzylammonium chloride, tetradecyldimethylbenzylammonium chloride , Octadecyldimethylbenzylammonium chloride, oxyethyldodecylamine, etc. It can be shown. Two or more of these may be used in combination. In addition, when a nonionic emulsifier is used, emulsion polymerization can be completed with a relatively small amount of use, and there is an advantage that foaming at the time of sizing agent coating can be suppressed.

Various known initiators can be used without particular limitation as the polymerization initiator. Specific examples include inorganic peroxides such as hydrogen peroxide, ammonium persulfate, and potassium persulfate; organic peroxides such as benzoyl peroxide, dicumyl peroxide, and lauryl peroxide; 2,2′-azobisisobutyl Examples include azo compounds such as nitrile and dimethyl-2,2′azobisisobutyrate. When the polymerization initiator is a radical polymerization initiator, a reducing agent such as sodium sulfite or sodium thiosulfate may be used in combination to make the reaction system a redox system. The chain transfer agent is used to adjust the degree of polymerization (molecular weight) during polymerization to make the copolymer (A) have a desired molecular weight. For example, n-dodecyl mercaptan, n-octyl mercaptan, tar lead decyl mercaptan, n- octadecyl mercaptan, may be used an alkyl mercaptan chain transfer agent such as n- hexadecyl mercaptan. Incidentally, the amount of the polymerization initiator is Ri usually 0.01 to 5 wt% of the preferred der for each monomer total amount constituting the copolymer (A), the amount of the chain transfer agent is the co It is 0.25 to 5 weight% normally with respect to the total amount of each monomer which comprises a polymer (A) .

The copolymer (A) thus obtained has a solid content concentration of usually about 10 to 30% by weight, a viscosity in the solid content concentration range of about 10 to 10,000 mPa · s (25 ° C.), and a pH of 8.0 to 9. About 5. As for the molecular weight, if the molecular weight is too large, the viscosity becomes high and the sharpness at the time of printing tends to be strong, and handling when applying to paper tends to be difficult. If the molecular weight is too small, the size tends to be insufficient. Therefore, the range of 20,000 to 50,000. The surface sizing agent for newsprint according to the present invention contains the copolymer (A) thus obtained as a main component.

The surface sizing agent for newsprint according to the present invention has a solid content concentration of the copolymer (A) of usually about 10 to 30% by weight and a viscosity at 15% by weight (Brookfield rotational viscometer: 40 ° C.). The pH is adjusted to about 10 to 100 mPA · s, and the pH is adjusted to about 8.0 to 9.5, and is practically used.

  The surface sizing agent for newsprint according to the present invention includes oxidized starch, phosphate esterified starch, enzyme-modified starch, starch derivatives (hydroxyethyl starch, dialdehyde starch, etc.) for the purpose of enhancing paper strength and size effect. , Starch such as cationized starch; celluloses such as carboxymethyl cellulose; polyvinyl alcohols, polyacrylamides; and surface paper strength enhancers such as sodium alginate can be used in combination with newspaper.

In addition, if necessary, various other known sizing agents, emulsion type sizing agents, anti-slip agents, antiseptics, rust inhibitors, pH adjusters, antifoaming agents, thickeners, fillers, antioxidants, water resistance Agents, film-forming aids, pigments, dyes and the like can be added.

The surface sizing agent for newsprint according to the present invention is applied to a newsprint base paper by a conventionally known method such as an impregnation method, a size press method, a gate roll method, a bar coater method, a calendar method, or a spray method. Also the coating amount, 0.001 to 1 g / ^{m 2} is usually in terms of solid content, preferably 0.01 to 0.5 g / ^{m 2.} When the coating amount is less than 0.001 g / m ² , the effect is not sufficiently exhibited in terms of imparting size. On the other hand, if the coating amount is more than 1 g / m ^{2, the} desired size effect cannot be obtained, and the cost is disadvantageous.

Newsprint base paper to which the surface sizing agent for newsprint according to the present invention is applied is mechanical pulp (MP) such as ground pulp (GP), thermomechanical pulp (TMP), chemithermomechanical pulp (CTMP), and semi-chemical pulp. ), Chemical pulp (CP) typified by kraft pulp (KP), deinked pulp (DIP) obtained by deinking waste paper containing these pulps, and recovery obtained by removing damaged paper from the papermaking process Pulp and the like are mixed alone or in an arbitrary ratio, and are generally made by a publicly known paper machine. The blending ratio of DIP is preferably in the range of 50 to 100% in view of the recent trend toward high blending of DIP. Further, the basis weight of the base paper is not particularly limited, but is about 34 to 45 g / m ² .

As such newsprint base paper, base paper with an internally added size may be used. However, in the present invention, there is also a meaning to solve the problems associated with the internally added size as described above. Therefore, the effect of the present invention is more exhibited by using a base paper that has not been internally added. be able to. That is, by external addition of the surface treatment agent of the present invention, it is possible to impart water absorption resistance equivalent to or larger than the internal addition size without performing the internal addition size.

The newsprint base paper to which the surface sizing agent according to the present invention is applied may be acid newsprint base paper, or neutral or alkaline paper newsprint base paper.

The newsprint according to the present invention can be obtained by applying the surface sizing agent for newsprint according to the present invention to the newsprint base paper in the coating amount and drying it by a known means.

  Hereinafter, the present invention will be specifically described with reference to reference examples, examples and comparative examples, but the present invention is not limited to these examples. In each example, all parts and% are based on weight unless otherwise specified.

Production Example 1
200 parts of soft water and nonionic surfactant (trade name “Neugen ET190”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) while introducing nitrogen into a reactor equipped with a stirrer, reflux condenser, and nitrogen introduction tube , 1 part of an anionic surfactant (trade name (trade name “Neohaitenol S-70”, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was charged, and the system was heated to 80 ° C. while stirring. About 2 hours of monomer mixture obtained by mixing 45 parts of methacrylic acid, 35 parts of n-butyl methacrylate, 20 parts of n-butyl acrylate and 0.5 part of n-dodecyl mercaptan as a chain transfer agent from the dropping funnel At the same time, an aqueous solution prepared by dissolving 4 parts of ammonium persulfate as an initiator in 100 parts of water was dropped from another dropping funnel over about 2 hours, and then the reaction system was kept warm for 2 hours to carry out an emulsion polymerization reaction. Was completed. Thereafter, 43.6 parts of a 48% aqueous sodium hydroxide solution (100 mol% with respect to acrylic acid) was added, diluted with water and adjusted so that the concentration of the copolymer was 15%, and the viscosity at 25 ° C. was 1000 mPa · s. A copolymer aqueous solution was obtained.

Production Example 2
While introducing nitrogen into a reactor equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube, 100 parts of soft water and 75 parts of isopropyl alcohol were charged, and the system was heated to 80 ° C. while stirring. Next, about 2 parts of a monomer mixture obtained by mixing 45 parts of methacrylic acid, 35 parts of n-butyl methacrylate, 20 parts of n-butyl acrylate, and 0.5 part of n-dodecyl mercaptan as a chain transfer agent from the dropping funnel. The solution was added dropwise over a period of time, and at the same time, an aqueous solution prepared by dissolving 4 parts of ammonium persulfate in 100 parts of water as an initiator was added dropwise from another dropping funnel over about 2 hours. Thereafter, the reaction system was kept warm for 2 hours to complete the solution polymerization reaction. Thereafter, isopropyl alcohol is distilled off, and after cooling, 43.6 parts of a 48% aqueous sodium hydroxide solution (100 mol% with respect to acrylic acid) is added and diluted with water to adjust the copolymer concentration to 15%. A copolymer solution having a viscosity at 25 ° C. of 40 mPa · s was obtained.

Production Examples 3-7, Comparative Production Examples 1-3
Each copolymer aqueous solution was obtained by emulsion polymerization in the same manner as in Production Example 1 except that the monomers and chain transfer agents shown in Table 1 were used.

In Table 1, BA: butyl acrylate, BMA: butyl methacrylate, MMA: methyl methacrylate, MAA: methacrylic acid, 2EHA: 2-ethylhexyl acrylate, St: styrene, NDM: n-dodecyl mercaptan (chain transfer agent) Means.

In Table 1, “molecular weight” means the weight average molecular weight of the obtained copolymer, and the value is a styrene equivalent value measured by gel permeation chromatography (trade name “High Speed GPC System HLC8120” manufactured by Tosoh Corporation). Means.

<Adjustment of test coating solution>
Table 2 shows commercially available starches (trade names “Oji Ace A”, manufactured by Oji Corn Starch Co., Ltd.) for each of the aqueous copolymer solutions (solutions) obtained in Production Examples 1 to 7 and Comparative Production Examples 1 to 3. It mixed so that it might become a ratio (solid content weight ratio), and also diluted with distilled water, and prepared the coating liquid. In Table 2, “Viscosity (mPa · s / 40 ° C.)” indicates a value measured with a Brookfield viscometer.

<Creation of test paper>
Using acid newspaper base paper (weighing 43 g / m ² ) as base paper, each surface sizing agent obtained by the above method was applied using a gate roll coater so that the coating amount of the sizing agent was as shown in Table 2. Next, each coated paper was dried at 80 ° C. for 30 seconds using a rotary drum dryer to obtain a target test paper. In addition, what applied only starch to this acidic newspaper base paper is made into a reference example.

Examples 1 to 7, Comparative Examples 1 to 3, Reference Example (size measurement: drop size)
Using the test paper obtained by the above method, based on the method according to Japan TAPPI No. 33, 1 μl and 5 μl of water are dropped on the surface of the test paper, and the time until the water drops are absorbed by the paper surface is measured. The size (drop size) degree (second) was measured. Note that the measurement of the drop size is considered to indicate the paper behavior of the time from when dampening water adheres to the paper in the offset rotary press until it is discharged as printed matter. The higher the number (longer seconds), the better the size. The results are shown in Table 2. The test result of the base paper is shown as a reference example.

(Measurement of sizing degree: contact angle)
Using each test paper obtained by the above method, using a Dynamic Adsorption Tester 1100 DAT (manufactured by Fibro), 1 μl of water droplet is dropped on the paper surface, and the contact angle is measured 0.1 seconds and 1 second after dropping. did. This contact angle is considered to indicate the paper behavior in a short time between the cylinders in an actual newspaper offset printing press. The larger the contact angle (degree), the better the size. The results are shown in Table 2. The test result of the base paper is shown as a reference example.

(Measurement of Neppari)
Using each test paper obtained by the above method, each test paper was dipped in water for 1 second and then pulled up, and passed through a roll with a linear pressure of 980 N / cm in a state where the surfaces were bonded together. After the test paper was air-dried, the T-shaped peel strength (N / m) was measured using a tensile tester (trade name “LRX” manufactured by Yasuda Seiki Shokai Co., Ltd.). The obtained measured value is defined as Nepari intensity. The higher the value, the stronger Nepari. The results are shown in Table 2. The test result of the base paper is shown as a reference example.

(Foaming test)
Starch (trade name “Oji Ace A”, manufactured by Oji Cornstarch Co., Ltd.) is added to each of the aqueous copolymer solutions obtained in Production Examples 1 to 7 and Comparative Production Examples 1 to 3, and an aqueous starch / copolymer solution ( Solid content) is 8.0 wt% / 1.3 wt%, and the resulting mixture is heated to 50 ° C and treated with a home mixer for 2 minutes. Height was measured. The liquid level before the treatment is 60 mm. The results are shown in Table 2.

The surface sizing agent according to the present invention is particularly suitably used for newsprint applications.

Claims (4)

Ethylenically unsaturated carboxylic acid monomer and 4 5-60 wt%, it as ethylenically unsaturated carboxylic acid ester monomer 5 5 to 40 wt% of a component including (meth) acrylate, butyl and these A water-soluble copolymer (A) having a weight average molecular weight of 20,000 to 50,000, which is polymerized in the presence of 0.25 to 5% by weight of an alkyl mercaptan chain transfer agent based on the total amount of both monomers. A surface sizing agent for newsprint, comprising as a component. The surface for newsprint according to claim 1, wherein the butyl (meth) acrylate is composed of n-butyl acrylate and n-butyl methacrylate, and the weight ratio thereof is 0.3 to 0.6. Sizing agent. The surface sizing agent for newsprint according to claim 1 or 2 , wherein the copolymer (A) is produced by emulsion polymerization. Newsprint paper obtained by coating the surface sizing agent for newsprint paper according to any one of claims 1 to 3 on the surface.