JP4306356B2 - Surface sizing agent for inkjet printing paper and inkjet printing paper - Google Patents

Description

The present invention is an inkjet printing paper surface size relates及Beauty inkjet printing paper.

The surface sizing agent is a chemical that can impart a size effect by applying it to paper, and can improve the size effect such as the degree of steecht sizing and writing suitability. And so far, various surface sizing agents mainly composed of copolymers such as styrene- (meth) acrylic acid copolymers, styrene-maleic acid copolymers, olefin-maleic acid copolymers, etc. Has been developed.

By the way, with the diversification of paper and recording methods, various performances other than the size effect are required. For example, when printing on plain paper (such as PPC paper) by the inkjet recording method, which has been rapidly spreading in recent years, not only the size effect but also the improvement of print density and suppression of feathering to obtain high image quality, There is a demand for performance (inkjet aptitude) such as prevention of breakthrough due to ink sinking.

  In order to satisfy such ink jet aptitude, for example, a surface sizing agent (for example, see Patent Document 1) containing a copolymer containing a styrene monomer as a constituent component has been proposed. Since this is excellent in steecht size (size in the Z-axis direction), it can suppress the penetration of water and ink by itself and can obtain a high density image, but the size in the horizontal direction is weak. Bleeding easily occurs. For example, when applied to ink jet printing, feathering is likely to occur.

In addition, a surface sizing agent (for example, see Patent Document 2) mainly composed of a copolymer having a methacrylic acid butyl monomer and an anionic monomer as essential components has been proposed. However, since this is excellent in size in the horizontal direction, problems such as bleeding and feathering hardly occur, but it has a problem that the image density is likely to be lowered because the steecht size is weak.

JP-A-8-95282 JP 2001-232932 A

The present invention is an ink jet that can express not only the required performance as a general surface sizing agent but also a high degree of ink jet aptitude (particularly high print density and good feathering resistance) as compared with conventionally known surface sizing agents. surface sizing agent for printing paper, and an object of the invention to provide an ink jet printing paper formed by coating the ink-jet printing paper for surface sizing agent.

  In order to solve the above-described problems of the prior art, the present inventors have made extensive studies on the surface sizing agent applied to the surface of plain paper (such as PPC paper), and as a result, have a styrene monomer as a constituent. It has been found that according to a surface sizing agent for papermaking mainly composed of a mixture of a copolymer, a butyl (meth) acrylate monomer and a copolymer containing an anionic monomer as a constituent component, the above-mentioned problems can be solved. The present invention has been completed.

That is, the present invention relates to a styrene copolymer (A) (hereinafter referred to as copolymer (A)), and a copolymer (B) ((meth) acrylic acid monomer and (meth) acrylic acid). Hereinafter, the present invention relates to a surface sizing agent for ink jet printing paper containing a copolymer (B), and an ink jet printing paper obtained by coating the surface with the surface sizing agent.

  According to the present invention, compared with the conventional surface sizing agent using the copolymer (A) or the copolymer (B) as a single active ingredient, the ink jet aptitude is good, particularly high printing density and good It is possible to provide a papermaking surface sizing agent that can exhibit feathering resistance, and a coated paper obtained by coating the papermaking surface sizing agent.

  First, the copolymer (A) will be described. The copolymer (A) is composed of a styrene monomer and an anionic monomer copolymerizable therewith. Examples of the styrene monomer include styrene, α-methylstyrene, vinyltoluene, divinylbenzene and the like. The anionic monomer can be used without particular limitation as long as it has an anionic functional group or a salt thereof in the molecule. For example, (meth) acrylic acid (meaning acrylic acid or methacrylic acid; the same applies hereinafter) and the like. Monocarboxylic acids and maleic acids, dicarboxylic acids such as itaconic acid, citraconic acid, fumaric acid, muconic acid and the like, and half esters comprising these and various alcohols; vinylsulfonic acid, styrenesulfonic acid, 2-acrylamide 2-methylpropanesulfonic acid and other sulfonic acid group-containing unsaturated monomers; 2- (meth) acryloyloxyethyl acid phosphate and other phosphate group-containing unsaturated monomers; and alkali metals such as sodium salts and potassium salts thereof Salt, alkaline earth metal salt, ammonium salt, organic bases Salt and the like. In addition, as a substituent of the said half ester, a C1-C18 linear or branched alkyl group can be illustrated, for example, a methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group , Isobutyl group, t-butyl group, neopentyl group, n-hexyl group, cyclohexyl group, 2-ethylhexyl group, decyl group, palmityl group, stearyl group and the like. Other ester substituents include hydroxyalkyl groups such as 2-hydroxyethyl group and 2-hydroxypropyl group, and further benzyl group and allyl group. Of these ester substituents, an alkyl group having about 1 to 12 carbon atoms is preferred. This is because the viscosity of the surface sizing agent aqueous solution for papermaking according to the present invention is increased, and the stability at the time of coating (generation of an adhesive or the like) is degraded. Among the anionic monomers exemplified above, (meth) acrylic acid or (meth) acrylic acid neutralized salt is preferable because it is excellent in copolymerization with a styrene monomer and has a good size effect.

  The copolymer (A) usually contains about 20 to 80% by weight, preferably 40 to 60% by weight of the styrene monomer unit in the molecule, and an alkali metal salt or ammonia salt in the molecule. Alternatively, it is preferable to have at least one neutralized salt unit selected from the group consisting of organic amine salts from the viewpoint of facilitating water-solubilization.

  It should be noted that other polymerizable monomers can be used as needed as the monomer unit of the copolymer (A) as long as the effects of the present invention are not deviated and the effect can be maintained. Examples of the polymerizable monomer include vinyl esters such as (meth) acrylic acid ester, acrylonitrile, vinyl acetate, vinyl propionate, α-olefin having 6 to 22 carbon atoms, alkyl vinyl ether having 1 to 22 carbon atoms, vinyl pyrrolidone, and the like. Nonionic unsaturated monomers and acrylamide derivatives such as acrylamide and N-methylolacrylamide.

  The copolymer (A) can be produced according to various known polymerization methods. Specifically, a predetermined amount of the above-mentioned styrene monomer, anionic monomer, and polymerizable monomer used as needed are charged into a reaction vessel equipped with a suitable heating device and a stirrer, and then water, organic solvent are added to the vessel. In addition, various known emulsifiers are charged to emulsify and dissolve these monomers. Further, a known polymerization initiator may be added, heated to about 20 to 120 ° C., and polymerized with stirring for about 2 to 12 hours.

  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 dimethylformide. 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.

  As the polymerization initiator, various known ones can be used without particular limitation. Specific examples include inorganic peroxides such as hydrogen peroxide, ammonium persulfate, and potassium persulfate; benzoyl peroxide, dicumyl peroxide, lauryl peroxide. Examples thereof include organic peroxides such as oxides; azo compounds such as 2,2′-azobisisobutyronitrile and dimethyl-2,2′-azobisisobutyrate. When the polymerization initiator is a radical polymerization initiator, the reaction system may be a redox system in combination with a reducing agent such as sodium sulfite or sodium thiosulfate, and the polymerization degree (molecular weight) may be adjusted during the polymerization. In order to obtain viscosity, alkyl mercaptan chain transfer agents such as N-dodecyl mercaptan, N-octyl mercaptan, terrestrial decyl mercaptan, N-octadecyl mercaptan, N-hexadecyl mercaptan, and 2-mercaptobenzothiazole, bromotrichloromethane, Chain transfer agents such as α-methylstyrene dimer can also be used. The amount used is preferably about 0.01 to 5% by weight with respect to the total amount of each monomer constituting the copolymer (A).

  The water-soluble copolymer (A) thus obtained usually has a solid content of about 10 to 30% by weight, a viscosity in the solid content concentration range of about 10 to 5,000 mPa · s (25 ° C.), and a pH of 8. It is about 0.0 to 9.5. The molecular weight is not particularly limited, but is usually in the range of about 1,000 to 1,000,000, preferably 2,000 to 100,000 in terms of weight average molecular weight. When the molecular weight is less than 1,000, a sufficient size effect cannot be obtained, so that the print density tends to be lowered. On the other hand, when the molecular weight exceeds 1,000,000, the viscosity is transiently increased and the coating operation is performed. Tend to decrease.

  Next, the copolymer (B) will be described. The paper surface sizing agent according to the present invention is characterized in that a mixture of the copolymer (A) and the copolymer (B) is used, but a good size effect is expressed by adopting the configuration, In addition, a high print density and excellent feathering resistance can be obtained during ink jet printing.

  The copolymer (B) is composed of a butyl (meth) acrylate monomer and (meth) acrylic acid, and the butyl (meth) acrylate monomer is normal butyl (meth) acrylate, (meth) acrylic. Examples include isobutyl acid, sec-butyl (meth) acrylate, and tert-butyl (meth) acrylate, and these can be used alone or in combination. Among these butyl (meth) acrylate monomers, isobutyl (meth) acrylate and / or normal butyl methacrylate are preferable because they exhibit excellent inkjet suitability. Examples of (meth) acrylic acid include acrylic acid and methacrylic acid. These monomers can be used alone or in combination of two or more.

  The copolymer (B) usually contains about 20 to 80% by weight, preferably 40 to 70% by weight of a butyl (meth) acrylate monomer unit in the molecule, and an alkali metal in the molecule. It is preferable to have at least one neutralized salt unit selected from the group consisting of a salt, an ammonia salt or an organic amine salt, and this is preferable because water-solubilization is easy.

In addition, other polymerizable monomers can be used as necessary as monomer units of the copolymer (B) obtained without departing from the object of the present invention and maintaining the effect. Examples of the polymerizable monomer include (meth) acrylic acid esters other than (meth) acrylic acid butyl monomers, vinyl esters such as acrylonitrile, vinyl acetate, and vinyl propionate, α-olefins having 6 to 22 carbon atoms, and carbon numbers. 1 to 22 alkyl vinyl ethers, nonionic unsaturated monomers such as vinyl pyrrolidone, and the like, and dicarboxylic acids such as maleic acid, maleic acid, itaconic acid, citraconic acid, fumaric acid, muconic acid, and the anhydrides thereof, and various alcohols thereof Half-ester consisting of: sulfonic acid group-containing unsaturated monomer such as vinyl sulfonic acid, styrene sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid; phosphoric acid group-containing such as 2- (meth) acryloyloxyethyl acid phosphate Discordant monomers; and these Mention may be made of thorium salts, alkali metal salts such as potassium salts, alkaline earth metal salts, ammonium salts, the anionic unsaturated monomers, such as salts of organic bases.

  The said copolymer (B) can be manufactured by various well-known polymerization methods similarly to the said copolymer (A). Specifically, a reaction vessel equipped with a suitable heating device and a stirrer is charged with a predetermined amount of (meth) acrylic acid butyl monomer, (meth) acrylic acid and a polymerizable monomer used as required, and then the vessel. Water, an organic solvent and various known emulsifiers are added to the emulsion, and these monomers are emulsified and dissolved. Further, a known polymerization initiator may be added, heated to about 20 to 120 ° C., and polymerized with stirring for about 2 to 12 hours. As the organic solvent, the polymerization initiator, and the chain transfer agent, the same ones as described above can be used.

  The water-soluble copolymer (B) thus obtained usually has a solid content of about 10 to 30% by weight, a viscosity in the solid content concentration range of about 10 to 5,000 mPa · s (25 ° C.), and a pH of 8. It is about 0.0 to 9.5. The molecular weight is not particularly limited, but is usually in the range of about 1,000 to 1,000,000, preferably 2,000 to 100,000 in terms of weight average molecular weight. When the molecular weight is less than 1,000, a sufficient size effect cannot be obtained, so that the print density tends to be lowered. On the other hand, when the molecular weight exceeds 1,000,000, the viscosity is transiently increased and the coating operation is performed. Tend to decrease.

  As described above, the surface sizing agent for papermaking according to the present invention is characterized in that a mixture of the copolymer (A) and the copolymer (B) is used, but such a mixture is used in the copolymer (A). The copolymer (B) may be produced not only by simply mixing the copolymer (B) but also by continuously producing the copolymer (B) in the same system after producing the copolymer (A). Or after manufacturing a copolymer (B), you may manufacture a copolymer (A) continuously by the same system. In addition, the method of continuous production is not particularly limited, and any known means may be followed. The mixture thus obtained has a solid content concentration of usually 15 to 30% by weight, a viscosity (Brookfield rotational viscometer: 25 ° C.) at a solid content concentration of 20% by weight of usually 10 to 50000 mPa · s, and a pH of usually 8. It adjusts so that it may become 0-10.0, and uses for practical use.

The weight ratio (solid content) of the copolymer (A) and the copolymer (B) is not particularly limited, but is preferably about 9.5 / 0.5 to 1/9, particularly preferably 1/1. ~ 1/3. By setting it as such a range, it is possible to achieve higher printing density and better feathering resistance.

The surface sizing agent for inkjet printing paper according to the present invention is put to practical use by a conventionally known coating method such as an impregnation method, a size press method, a gate roll method, a bar coater method, a calendar method, and a spray method. Moreover, the application quantity is 0.001-5 g / m < ² > normally in conversion of solid content, Preferably it is 0.005-1 g / m < ² >.

In the surface sizing agent for inkjet printing paper according to the present invention, starches such as oxidized starch, phosphate esterified starch, enzyme-modified starch, and cationized starch that are usually used as other paper strength enhancers as other components; carboxymethylcellulose Celluloses such as water-soluble polymers such as polyvinyl alcohols, polyacrylamides and sodium alginate can be added. 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.

Inkjet printing paper according to the present invention, the ink-jet printing paper for surface sizing agent PPC paper, inkjet or toner printer paper, not only the information sheet of the heat-sensitive paper or the like, pressure-sensitive paper, writing paper, coat base paper, such as books paper wood free paper, medium-quality paper, medium-quality coated base paper, packaging paper, kraft paper, liner, paperboard, gypsum board liner, which was coated with the coating method to newsprint, etc., you particularly suitable for ink jet printing method .

  Hereinafter, the present invention will be specifically described with reference to production 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
<Production of copolymer (A)>
To a reactor equipped with a stirrer, a reflux condenser, and a nitrogen introduction tube, 100 parts of water and 75 parts of isopropyl alcohol were added while introducing nitrogen, and the mixture was heated with stirring to raise the temperature to 80 ° C. A total amount of a monomer mixture obtained by mixing 50 parts of styrene, 5 parts of isopropyl alcohol maleic anhydride half ester and 45 parts of methacrylic acid, and an aqueous polymerization initiator solution in which 5 parts of ammonium persulfate was dissolved in 120 parts of water in 3 hours. Then, the reaction was completed by aging for 2 hours. Thereafter, isopropyl alcohol was distilled off, and after cooling, 33.7 parts of 28% aqueous ammonia solution (100 mol% with respect to acrylic acid and isopropyl alcohol maleic anhydride half ester) was diluted with water, and the copolymer concentration was reduced. It adjusted so that it might become 20%, and the aqueous solution of the copolymer (A) whose viscosity of 25 degreeC is 1100 mPa * s was obtained.

Production Example 2
<Production of copolymer (B)>
A monomer mixture obtained by mixing 42.9 parts of isopropyl alcohol, 60 parts of normal butyl methacrylate and 40 parts of methacrylic acid in a flask equipped with a stirrer, a cooling pipe, a dropping funnel, a nitrogen introducing pipe and a thermometer, and 5 parts of ammonium persulfate A total amount of an aqueous polymerization initiator solution dissolved in 120 parts of water was dropped in 3 hours and then aged for 2 hours to complete the reaction. Thereafter, isopropyl alcohol is distilled off, and after cooling, 28.3 parts of a 28% aqueous ammonia solution (100 mol% with respect to methacrylic acid) is added and diluted with water to adjust the copolymer concentration to 20%. An aqueous solution of copolymer (B) having a viscosity of 20 mPa · s at 20 ° C. was obtained.

<Adjustment of sizing agent>
The copolymer (A) and the copolymer (B) are mixed at the ratio (solid content ratio) shown in Table 1, and further starch (trade name “Oji Ace A”, manufactured by Oji Corn Starch Co., Ltd.) is shown in Table 1. In addition, the surface sizing agents according to Examples 1 to 5 and Comparative Examples 1 and 2 were adjusted.

<Creating printing paper>
Calcium carbonate 20% with respect to pulp addition rate, alkenyl succinic anhydride sizing agent (Arakawa Chemical Industries, trade name “Sizepine SA 850”) 0.05%, sulfuric acid band 0.5%, cationized starch 0.4%, an anionic retention agent (trade name “KW-504”, manufactured by Arakawa Chemical Industries, Ltd.) is used in an internal additive of 0.01%, and the Steecht sizing degree is 22 seconds. sex PPC sheet using (weighing value 70 g / m ²⁾ in each sizing agent laboratory size press (manufactured by Kumagai Riki Kogyo Co.), sizing agent coating amount was applied so as to Table 1 . Next, each coated paper was placed in a circulation dryer and dried at 105 ° C. for 1 minute to obtain a printing paper.

<Stick human size>
About the coated paper which carried out the said size process, according to JISP-8122, the Steecht sizing degree (second) was measured. The larger the value, the better the sizing degree.

<Pen writing size>
Regarding the coated paper subjected to the above-mentioned size treatment, J. Org. Tappi No. 12 was used to measure the pen writing size. The larger the value, the better the sizing degree. The results are shown in Table 2.

<Inkjet aptitude evaluation (print density)>
The evaluation of the printing density was carried out by solid printing in monochrome and color on the coated paper subjected to the above size processing using an inkjet printer BJC-420J manufactured by Canon Inc. The results are shown in Table 3. Moreover, it performed by carrying out monochrome printing using the inkjet printer BJ-300J made from Canon. The print density was measured using a reflection densitometer (trade name GREDAG D186, manufactured by GREDAG MACBETH Co., Ltd.). The larger the value, the higher the print density. The results are shown in 4.

<Inkjet aptitude evaluation (feathering test)>
In the evaluation of the feathering test, straight lines and characters having a constant line width were printed on the printing paper obtained by the above method using BJC-420J, and the bleeding of the outer edges of the straight lines and characters was visually evaluated. . The results are shown in Table 3. In addition, straight lines and characters with a constant line width were printed using BJ-300J, and bleeding of the outer edges of the straight lines and characters was visually evaluated. The results are shown in Table 4. In addition, the case where there was no feathering was set to 6, and the case where ink was blurred and the character could not be identified was set to 1.

The surface sizing agent for papermaking according to the present invention can be suitably used as a surface sizing agent for not only ordinary paper (such as PPC paper) but also ink jet printing paper.

Claims (5)

A surface sizing agent for ink-jet printing paper comprising a styrene copolymer (A) and a copolymer (B) comprising a butyl (meth) acrylate monomer and (meth) acrylic acid. The surface sizing agent for ink-jet printing paper according to claim 1, wherein the weight ratio of the solid content of the copolymer (A) and the copolymer (B) is 9.5 / 0.5 to 1/9. The surface sizing agent for inkjet printing paper according to claim 1 or 2, wherein the copolymer (A) comprises a styrene monomer and an anionic monomer. The surface sizing agent for inkjet printing paper according to any one of claims 1 to 3, wherein the (meth) butyl acrylate monomer is isobutyl (meth) acrylate and / or normal butyl (meth) acrylate. Inkjet printing paper formed by coating the surface of the ink-jet printing paper for surface sizing agent according to any one of claims 1 to 4.