JP2009028933A - Binder composition for ink-jet recording medium, coating composition for ink-jet recording medium, ink-jet recording medium and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink-jet recording medium excellent in white paper gloss, ink absorbency, printing density and clearness, to provide a binder composition for obtaining the ink-jet recording medium, and to provide a coating composition for the ink-jet recording medium a method of manufacturing the ink-jet recording medium. <P>SOLUTION: The binder composition for ink-jet recording medium comprises 100 pts.wt. of a polymer and 1-35 pts.wt. of a water soluble high molecular compound containing an alcoholic hydroxyl group, wherein at least 30 wt.% in the water soluble high molecular compound containing an alcoholic hydroxyl group having the hydrophobic group is combined or adsorbed to the polymer. The coating composition for ink-jet recording medium comprises this binder composition and pigment. The ink-jet recording medium is obtained by coating a support with this coating composition. The manufacturing method of the ink-jet recording medium is characterized in that, after forming a coating film composed of this coating composition on the support, the coating film is subjected to calendering under heating and pressurization. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a binder composition for an inkjet recording medium, a coating composition for an inkjet recording medium, an inkjet recording medium, and a method for producing the same. More specifically, a coating composition for an ink jet recording medium that can provide an ink jet image having excellent paint blending stability and excellent white paper gloss, print density, and sharpness, and a binder composition for an ink jet recording medium for obtaining the same. The present invention also relates to an ink jet recording medium obtained using the coating composition for ink jet recording medium and a method for producing the ink jet recording medium.

The ink jet recording method is a method for recording characters, images, and the like by ejecting fine ink droplets from nozzles by various operating principles and attaching them to a recording medium. This recording method is characterized in that it is easy to increase the speed and color, and does not require processing such as development and fixing, and is rapidly spreading in recording apparatuses such as printers and plotters.
In recent years, the ink jet recording technology has rapidly advanced, and a recorded matter having an image quality equal to or higher than that obtained by a general silver salt photography method has been obtained. Accordingly, ink jet recording media having a texture equivalent to that of photographic paper used in silver salt photography are required.

The recording medium used for the ink jet recording method usually has a coating film formed by applying an aqueous resin composition on a support such as paper and drying it as an ink receiving layer.
In order to obtain an ink jet recording medium excellent in texture using this aqueous resin composition, various studies have been made.

Patent Document 1 is provided with an ink receiving layer containing thermoplastic polymer fine particles having a minimum film-forming temperature of 40 to 160 ° C. such as a pigment such as vapor phase method silica, a hydrophilic binder such as polyvinyl alcohol, and a polyolefin resin. After or after providing a protective layer of the above composition on an ink receiving layer containing a pigment and a hydrophilic binder, a calender having a metal roll is used at a temperature not lower than the minimum film formation temperature of the thermoplastic polymer fine particles and not higher than 250 ° C. An ink jet recording material obtained by surface treatment is disclosed.
According to the study by the present inventors, this ink-jet recording material is excellent in white paper gloss and ink absorbency, but has a problem that surface strength is inferior.

In Patent Document 2, an inner ink receiving layer containing a pigment and a resin material is formed, a boric acid-containing solution is applied on the receiving layer, and then a polymer capable of crosslinking reaction with boric acid is included on the inner ink receiving layer. An ink jet recording sheet manufacturing method for forming an outer ink receiving layer containing a resin material and a pigment is disclosed. In this method, examples of the polymer capable of crosslinking reaction with boric acid include polyvinyl alcohol.
However, in order to obtain sufficient ink gloss and ink absorbency by this method, it is necessary to provide a very thick coating layer, which increases the drying load in the coating process and deteriorates productivity. When the recording sheet is bent, there is a problem in strength such that the coating layer is easily detached from the substrate.

Patent Documents 3 and 4 include emulsion resins and water-soluble resins (polyvinyl alcohol or polyvinyl alcohol or emulsion polymer obtained by emulsion polymerization with wet silica fine particles (Patent Document 3) or alumina (Patent Document 4) and a polymer dispersant having a hydroxyl group such as polyvinyl alcohol. An ink jet recording paper having an ink absorbing layer containing a binder containing a derivative thereof is disclosed. At this time, the ink having a compound having a group capable of reacting with the binder or a compound such as an epoxy compound, an aldehyde, a halogen compound, or boric acid (salt) that promotes the reaction between the groups of the binder is used as a crosslinking agent. It is preferable to add to the coating solution for forming the absorbent layer or to apply an overcoat after coating the coating solution.
According to these patent documents, a high-quality inkjet that is excellent in glossiness, ink absorption, image bleeding resistance after printing storage, and has a flexible ink absorption layer that does not crack even if it is rolled or folded. Recording paper is supposed to be obtained.
However, according to the study by the present inventors, the coating liquid containing each of the above components is inferior in coating composition stability, that is, the coating liquid thickens or aggregates with time. It became clear that there was a problem that things were generated.

Japanese Patent Laid-Open No. 2003-1928 Japanese Patent Laid-Open No. 2003-231342 JP 2004-188769 A JP 2004-314321 A

Accordingly, an object of the present invention is to provide a coating composition for ink jet recording excellent in paint blending stability for obtaining an ink jet recording medium excellent in blank paper gloss, print density and sharpness, and an ink jet recording binder for obtaining the same. It is to provide a composition. Another object of the present invention is to provide an ink jet recording medium obtained using the coating composition for ink jet recording medium. Still another object of the present invention is to provide a method for producing the ink jet recording medium.
As a result of diligent research to achieve the above object, the present inventors have found that a specific polymer obtained by using a specific water-soluble polymer compound can be used to achieve a binder composition for an ink jet recording medium that meets the above object. And a coating composition for inkjet recording media was found, and the present invention was completed based on this finding.

  Thus, according to the present invention, 100 parts by weight of a polymer and 1 to 35 parts by weight of an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group are contained. There is provided a binder composition for an ink jet recording medium, wherein at least 30% by weight of a molecular compound is bonded or adsorbed to the polymer.

  The binder composition for inkjet recording media of the present invention polymerizes the first monomer in the presence of a nonionic surfactant and an anionic surfactant, and then has a hydrophobic group in the obtained latex. It is preferably obtained by adding an alcoholic hydroxyl group-containing water-soluble polymer compound and a second monomer and further continuing the polymerization.

In the binder composition for an ink jet recording medium of the present invention, the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group preferably has a hydrophobic group at its molecular end.
In the binder composition for an ink jet recording medium of the present invention, the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is preferably a polyvinyl alcohol having a hydrophobic group.
Furthermore, in the binder composition for an inkjet recording medium of the present invention, the hydrophobic group contained in the water-soluble polymer compound containing an alcoholic hydroxyl group is preferably a hydrocarbon group having 5 to 20 carbon atoms.

Moreover, according to this invention, the coating composition for inkjet recording media formed by containing the binder composition for inkjet recording media of this invention, and a pigment is provided.
The coating composition for inkjet recording media of the present invention preferably further contains a crosslinking agent.
Furthermore, according to the present invention, there is provided an inkjet recording medium obtained by coating a coating composition for an inkjet recording medium on a support, comprising at least one layer of the coating composition for an inkjet recording medium of the present invention. An ink jet recording medium having a coated layer is provided.
In the inkjet recording medium of the present invention, the outermost surface layer of the coating layer is preferably a layer formed by applying the coating composition for an inkjet recording medium of the present invention.
Furthermore, according to the present invention, after forming a coating film comprising the coating composition for an inkjet recording medium of the present invention on a support, the inkjet coating is characterized by calendering the coating film under heat and pressure. A method for manufacturing a medium is provided.

  The ink jet recording medium coating composition obtained from the ink jet recording medium binder composition of the present invention is excellent in paint blending stability, and is used for ink jet recording excellent in white paper gloss, print density and sharpness. A medium can be obtained.

The binder composition for an inkjet recording medium of the present invention comprises 100 parts by weight of a polymer and 1 to 35 parts by weight of an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group, and the alcoholic group having the hydrophobic group. It is characterized in that at least 30% by weight of the hydroxyl group-containing water-soluble polymer compound is bonded or adsorbed to the polymer.
The ink jet recording medium binder composition functions as a medium for dispersing necessary components or optional components usually blended in the ink jet recording medium coating composition, and fixes them to a suitably selected support, It has a binder function for forming an ink receiving layer.

The polymer used as a constituent of the binder composition for an inkjet recording medium in the present invention is not particularly limited as long as it can be used for an inkjet recording medium.
Specific examples of monomers for obtaining such a polymer include olefins such as ethylene, propylene, 1-butene, and isobutene; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride. Carboxylic acid vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, isopropenyl acetate, vinyl versatate; styrene, α-methylstyrene, monochlorostyrene, dichlorostyrene, monomethylstyrene, dimethylstyrene Aromatic vinyl monomers such as trimethylstyrene, hydroxymethylstyrene, p-styrenesulfonic acid and sodium and potassium salts thereof; ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid, crotonic acid and itaconic acid And its esters, amides, etc. Derivatives; Ethylenically unsaturated polyvalent carboxylic acids such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, and derivatives thereof such as esters, anhydrides and amides; ethylenically unsaturated such as (meth) acrylonitrile Saturated nitrile monomer; 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 2-chloro-1, Conjugated dienes such as 3-butadiene, 1,3-pentadiene, 1,3-hexadiene, 2,4-hexadiene; methyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, Vinyl ether monomers such as dodecyl vinyl ether; allyl acetate, vinegar And allyl compounds such as methallyl acid, allyl chloride, and methallyl chloride; vinyl silane compounds such as vinyltrimethoxysilane; vinyl heterocyclic compounds such as vinylpyridine and N-vinylpyrrolidone; and the like.
In the present invention, “(meth) acrylic acid” means “acrylic acid” and / or “methacrylic acid”. Similarly, “(meth) acrylonitrile” means “acrylonitrile” and / or “methacrylonitrile”.

  Among these monomers, ethylenically unsaturated monocarboxylic acids and derivatives thereof, ethylenically unsaturated polyvalent carboxylic acids and derivatives thereof, and ethylenically unsaturated nitrile monomers are preferable. Carboxylic acid and its derivatives are preferred.

Specific examples of the ethylenically unsaturated monocarboxylic acid include acrylic acid, methacrylic acid and crotonic acid.
Specific examples of suitable ester derivatives of ethylenically unsaturated monocarboxylic acids include esters of ethylenically unsaturated monocarboxylic acids with alcohols having 1 to 12 carbon atoms. Specific examples thereof include (meth) acrylic. Methyl methacrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, (meth) Examples include 2-hydroxyethyl acrylate, dimethylaminoethyl (meth) acrylate, and the like.
Specific examples of amide derivatives of ethylenically unsaturated monocarboxylic acids include (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, (meth) acrylamide-2-methylpropane Examples thereof include sulfonic acid and its sodium salt.

  In the present invention, polymers that can be preferably used include (meth) acrylic acid ester homopolymers and copolymers, (meth) acrylic acid esters, conjugated dienes, aromatic vinyl compounds, (meth) acrylonitrile, etc. And a copolymer thereof.

The alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group used as a constituent of the binder composition for an inkjet recording medium in the present invention contains 5 to 25 alcoholic hydroxyl groups per 1,000 molecular weights. A high molecular compound having a hydrophobic group.
Specific examples of the alcoholic hydroxyl group-containing water-soluble polymer compound include: vinyl alcohol polymers such as polyvinyl alcohol and various modified products thereof; saponified products of copolymers of vinyl acetate and acrylic acid, methacrylic acid or maleic anhydride Cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, alkyl hydroxyalkyl cellulose; starch derivatives such as alkyl starch, carboxymethyl starch and oxidized starch; gum arabic, tragacanth rubber; polyalkylene glycol and the like. Of these, vinyl alcohol polymers are preferred from the viewpoint of easy availability of industrially stable products.

The hydrophobic group that the alcoholic hydroxyl group-containing water-soluble polymer compound should have is a hydrocarbon group having 5 to 20 carbon atoms. The hydrocarbon group may be an aliphatic group, an alicyclic group, or an aromatic group.
Although there is an example in which polyvinyl alcohol having a silyl group is used in the synthesis of a binder for inkjet recording paper (Patent Document 3), in the present invention, when an alcoholic hydroxyl group-containing water-soluble polymer compound having a silyl group is used, The particle size of the obtained binder becomes large, and the stability of both the ink jet recording binder composition and the ink jet recording coating composition obtained using the same decreases.
In the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group, the position of the hydrophobic group is not particularly limited, and even if it exists at the molecular end of the water-soluble polymer compound, it exists in the middle position of the molecular chain. However, those existing at the molecular ends are preferred.
The amount of the hydrophobic group is not particularly limited, but is usually 0.5 to 20% by weight based on the total weight of the polymer.

The alcoholic hydroxyl group-containing water-soluble polymer having a hydrophobic group can be obtained by introducing a hydrophobic group into the alcoholic hydroxyl group-containing water-soluble polymer by a known method.
For example, in the case of an alcoholic hydroxyl group-containing polyvinyl alcohol having a hydrophobic group, a method in which a hydrophobic monomer having a hydrocarbon group having 5 to 20 carbon atoms is copolymerized with vinyl acetate and then partially or completely saponified, , Allyl glycidyl ether, butadiene monoepoxide, N-glycidoxymethyl acrylamide, etc. are copolymerized with vinyl acetate and then saponified in the presence of a thiol compound to introduce a hydrophobic group at the middle position of the molecular chain. Can be mentioned. According to this latter method, the amount of the hydrophobic group can be controlled by controlling the amount of the epoxy group-containing monomer used for the copolymerization. Furthermore, polyvinyl alcohol which does not have a hydrophobic group can also be obtained by etherification, esterification or acetalization with a reactive compound having a hydrocarbon group having 5 to 20 carbon atoms.

  The weight average molecular weight of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is not particularly limited, but is usually 1,000 to 500,000, preferably 2,000 to 300,000. When the molecular weight is less than 1,000, the dispersion stabilizing effect when the monomer is polymerized using this as a dispersing agent becomes low. On the other hand, when the molecular weight is more than 500,000, the viscosity of the polymerization system becomes high and the polymerization becomes difficult. There is a fear.

In the binder composition for an inkjet recording medium of the present invention, the amount of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is 1 to 35 parts by weight, preferably 1 to 35 parts by weight with respect to 100 parts by weight of the polymer. 25 parts by weight, more preferably 1 to 15 parts by weight.
In the ink jet recording medium binder composition of the present invention, it is essential that at least 30% by weight of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is bound or adsorbed to the polymer. The degree of binding or adsorption can be adjusted by the type and amount of the alcoholic hydroxyl group-containing water-soluble polymer compound used.
What is excellent in surface strength, water-resistant surface strength, print density and sharpness of the resulting ink jet recording medium because the water-soluble polymer containing an alcoholic hydroxyl group having a hydrophobic group is bonded or adsorbed to the polymer. The effect of becoming.

Such a polymer and an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group are contained, and at least a part of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is contained in the polymer. The binder composition for ink jet recording bonded or adsorbed is not limited in its production method, but the monomer constituting the polymer is polymerized in the presence of an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group. Can be obtained.
Preferably, the binder composition for inkjet recording media of the present invention polymerizes the first monomer in the presence of a nonionic surfactant and an anionic surfactant, and then the obtained latex is subjected to It is obtained by adding an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group and a second monomer, and further continuing the polymerization. In the present invention, “monomer” is a concept including “monomer mixture”.

In the above method for producing a binder composition for ink jet recording, first, polymerization of a part of all monomers is performed in the presence of a nonionic surfactant and an anionic surfactant (this polymerization). (Sometimes referred to as “first stage polymerization”).
The ratio of the monomer used for the first stage polymerization is not particularly limited, but is 20 to 80% by weight, preferably 30 to 70% by weight, based on all monomers.
The composition of the monomer used in the first stage polymerization (this monomer may be referred to as “first monomer”) is not particularly limited, but the composition of the polymer obtained by the first stage polymerization is not particularly limited. It is preferable that the glass transition temperature is −85 to + 60 ° C., preferably −60 to + 20 ° C.

The first stage polymerization is preferably carried out in the presence of a nonionic surfactant and an anionic surfactant.
The nonionic surfactant suitably used in the first stage polymerization is not particularly limited.
Specific examples thereof include polyoxyalkylene alkyl aryl ether surfactants, polyoxyalkylene alkyl ether surfactants, polyoxyalkylene fatty acid ester surfactants, sorbitan fatty acid ester surfactants, silicone surfactants, acetylene alcohols Surfactant, fluorine-containing surfactant, etc. are mentioned.

Specific examples of the polyoxyalkylene alkyl aryl ether surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene dodecyl phenyl ether.
Specific examples of the polyoxyalkylene alkyl ether surfactant include polyoxyethylene oleyl ether and polyoxyethylene lauryl ether.
Specific examples of the polyoxyalkylene fatty acid ester surfactant include polyoxyethylene oleate, polyoxyethylene laurate, and polyoxyethylene distearate.
Specific examples of the sorbitan fatty acid ester surfactant include sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate and the like.

Specific examples of silicone surfactants include dimethylpolysiloxane.
Specific examples of the acetylene alcohol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, , 5-dimethyl-1-hexyne-3ol and the like.
Specific examples of the fluorine-containing surfactant include a fluorine alkyl ester.

  The amount of the nonionic surfactant used in the first stage polymerization is preferably 0.3 to 6.0 parts by weight with respect to 100 parts by weight of the monomer mixture in the first stage polymerization. The amount is more preferably 5 to 4.0 parts by weight, and still more preferably 1.0 to 2.5 parts by weight. If the amount used is less than the above lower limit, the resulting latex may be inferior in cation stability. On the other hand, when the amount used exceeds the above upper limit, the sharpness of the inkjet recording medium obtained using the obtained binder may be lowered.

The anionic surfactant suitably used in the first stage polymerization is not particularly limited, and specific examples thereof include a carboxylate surfactant, a sulfonate surfactant, a sulfate ester surfactant, and a phosphate ester. Mention may be made of surfactants.
Specific examples of the carboxylate surfactant include fatty acid salts, N-acylamino acids and salts thereof, polyoxyethylene alkyl ether carboxylates, acylated peptides, and the like.
Specific examples of the sulfonate surfactant include alkylbenzene sulfonate, alkyl naphthalene sulfonate, naphthalene sulfonate formalin condensate, melamine sulfonate formalin condensate, dialkyl sulfosuccinate ester salt, alkyl sulfoacetate salt, Examples thereof include α-olefin sulfonates and N-acyl alkyl sulfonates.

Specific examples of the sulfate ester surfactant include sulfated oil, higher alcohol sulfate ester salt, polyoxyethylene alkyl ether sulfate, higher alcohol ethoxy sulfate, polyoxyethylene alkyl phenyl ether sulfate, mono fatty acid glyceryl sulfate, Examples thereof include fatty acid alkylolamide sulfate salts.
Specific examples of the phosphate ester surfactant include an alkyl ether phosphate ester salt and an alkyl phosphate ester salt.

  The amount of the anionic surfactant used in the first stage polymerization is preferably 0.1 to 5.0 parts by weight with respect to 100 parts by weight of the monomer used in the first stage polymerization. 0.5 to 4.0 parts by weight is more preferable, and 0.5 to 3.0 parts by weight is even more preferable. If the amount used is less than the above lower limit, the particle size may increase, or the glossiness of the ink jet recording medium obtained using the resulting binder may decrease, and if the amount exceeds the upper limit, The resulting binder may be inferior in cation stability.

The ratio of the amount of the nonionic surfactant and the amount of the anionic surfactant preferably used for the first stage polymerization is not particularly limited, but preferably the amount of the nonionic surfactant / anionic interface The ratio of the amount of the activator is set in the range of 4/1 to 1/3.
Furthermore, the total amount of the nonionic surfactant and the anionic surfactant used in the first stage polymerization is 0.4 to 5.0 weights with respect to 100 parts by weight of the total monomers used in the polymerization. Part is preferable, 1.0 to 4.0 parts by weight is more preferable, and 1.5 to 3.0 parts by weight is still more preferable.
If the amount of the anionic surfactant used is too large, the cation stability of the resulting binder may be lowered. If the amount of the nonionic surfactant is too large, the particle size becomes too large, and the ink jet finally obtained. There is a possibility that the ink absorbability and glossiness of the recording medium are lowered.
In the present invention, it is preferable to use a nonionic surfactant and an anionic surfactant in combination in the first stage polymerization, and this is finally obtained while ensuring the cation stability of the resulting binder. Each characteristic of the ink jet recording medium can be made excellent.

The first stage polymerization is preferably carried out by an emulsion polymerization method in an aqueous medium.
As the aqueous medium, water or a mixture of water and an organic solvent miscible with water can be used.
In the first stage polymerization, the ratio of the monomer to the aqueous medium is not particularly limited, but usually the monomer is 5 to 100 parts by weight, preferably 10 to 70 parts by weight with respect to 100 parts by weight of the aqueous medium. Parts, more preferably 10 to 55 parts by weight.

A polymerization initiator is not specifically limited, An inorganic peroxide, an organic peroxide, an azo compound etc. can be used.
Specific examples of the inorganic peroxide polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; perphosphates such as potassium perphosphate; hydrogen peroxide; .
Specific examples of the organic peroxide polymerization initiator include hydroperoxides such as diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, and the like. And peroxides such as di-t-butyl peroxide, isobutyryl peroxide, and benzoyl peroxide;
Specific examples of the azo compound polymerization initiator include azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, methyl azobisisobutyrate, and the like.
Among the initiators, a water-soluble radical polymerization initiator is preferable, and a persulfate is preferable, and potassium persulfate and ammonium persulfate are particularly preferable.
These polymerization initiators may be used alone or in combination of two or more.

The usage-amount of a polymerization initiator is 0.05-3 weight part normally with respect to 100 weight part of all the monomers used for superposition | polymerization, Preferably it is 0.1-2 weight part.
These polymerization initiators can be used as a redox polymerization initiator in combination with a reducing agent. The reducing agent is not particularly limited, and specific examples thereof include compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; sulfonic acid compounds such as sodium methanesulfonate; dimethylaniline and the like An amine compound; and the like. These reducing agents may be used alone or in combination of two or more.
Although the usage-amount of a reducing agent changes with reducing agents, it is preferable that it is 0.03-10 weight part with respect to 1 weight part of polymerization initiators.

  A known chain transfer agent may be appropriately added to the polymerization reaction system in order to adjust the molecular weight of the polymer. In particular, when a monomer containing a conjugated diene monomer such as 1,3-butadiene is polymerized, it is preferable to use a chain transfer agent. In this case, the chain transfer agent is used in an amount of 0.2 to 5 parts by weight with respect to 100 parts by weight of the monomer mixture.

Specific examples of the chain transfer agent include α-methylstyrene dimer, mercaptan compound, sulfide compound, nitrile compound, thioglycolic acid ester, β-mercaptopropionic acid ester and the like.
Specific examples of the mercaptan compound include t-dodecyl mercaptan and n-dodecyl mercaptan.
Specific examples of the sulfide compound include dimethylxanthogen disulfide and diisopropylxanthogen disulfide.
Specific examples of the nitrile compound include 2-methyl-3-butenenitrile and 3-pentenenitrile.
Specific examples of the thioglycolic acid ester include methyl thioglycolate, propyl thioglycolate, octyl thioglycolate and the like.
Specific examples of the β-mercaptopropionic acid ester include methyl β-mercaptopropionate and octyl β-mercaptopropionate.
Among these, thioglycolic acid ester is preferable, and octyl thioglycolate is more preferable.
These chain transfer agents may be used alone or in combination of two or more.

Although polymerization temperature is not specifically limited, Usually, 0-100 degreeC, Preferably it is 5-95 degreeC.
In addition, the method for adding the monomer is not particularly limited, and the monomer used for the first stage polymerization may be added all at once, or all the amounts may be added sequentially, The remainder may be added all at once or sequentially.
From the viewpoint of stabilizing the polymerization and improving the stability of the resulting ink jet recording binder composition, the monomer is preferably added as an emulsion using an aqueous medium and a surfactant.
Furthermore, the stirring conditions during the polymerization are not particularly limited.

  In the first stage polymerization, the polymerization conversion rate is preferably 85 to 98.5% by weight. If this conversion rate is too low, there is a risk that the cation stability of the resulting ink jet recording binder composition will decrease, and it is economical to continue the polymerization until the conversion rate is higher than the above upper limit. Absent.

In the first stage polymerization, after the polymerization conversion rate reaches a certain level, the second stage polymerization is performed.
In the second-stage polymerization, the latex obtained by the first-stage polymerization is used in the first-stage polymerization among the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group and all monomers (this is the remainder). Is sometimes referred to as “second monomer”), and polymerization is continued.
The monomer used in the first stage and the monomer used in the second stage may have the same composition or different compositions. The composition of the second monomer is not particularly limited, but the glass transition temperature of the polymer obtained by polymerizing only the second monomer is in the range of −20 to + 100 ° C., preferably +30 to + 90 ° C. It is preferable that Further, it is preferable that the glass transition temperature in the second stage is higher than the glass transition temperature in the first stage.
In the second stage polymerization, a polymerization catalyst may be additionally added as necessary. The polymerization catalyst used may be the same as or different from that used in the first stage.
The second stage polymerization may be carried out in two or more stages. That is, after polymerizing a part of the second monomer, the remainder may be further divided into several times.

  In the present invention, the stability of the resulting ink jet recording binder composition is improved by using the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group.

  In the present invention, the amount of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group that is preferably used for the second stage polymerization is not particularly limited, but is preferably a single unit used for the second stage polymerization. The amount is 3 to 50 parts by weight, more preferably 5 to 25 parts by weight with respect to 100 parts by weight of the monomer. When the amount used is within the above range, the dispersion stabilizing effect at the time of polymerization becomes high, the viscosity of the polymerization system becomes appropriate, the polymerization proceeds smoothly, and the resulting ink jet recording binder composition is used. The water resistance of the ink jet recording medium is excellent.

  In the second stage polymerization, the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group may be added as an aqueous medium solution separately from the monomer used in the second stage polymerization. It is easy to prepare a dispersion of the monomer as a dispersant and add the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group, an aqueous medium and the monomer at the same time to maintain polymerization stability. This is also preferable.

  In the second stage polymerization, the amount of the aqueous medium to be used is not particularly limited, but usually, in the polymerization system in the second stage, the monomer (first monomer and second monomer) and hydrophobic The total concentration with the alcoholic hydroxyl group-containing water-soluble polymer compound having a group is in the range of 15 to 35% by weight. If the amount of the aqueous medium is too large, the concentration of the resulting ink jet recording binder composition may be low, and an operation such as concentration may be required. Conversely, if the amount is too small, the polymerization stability may be reduced. .

In the present invention, a nonionic surfactant may be newly added during the second stage polymerization.
By additionally adding a nonionic surfactant during the polymerization in the second stage, an effect of improving the cation stability of the resulting ink jet recording binder composition can be obtained.
As the nonionic surfactant, those similar to those used in the first stage polymerization can be used.
The amount of the nonionic surfactant added additionally in the second stage polymerization is not particularly limited, but is usually 3.0 parts by weight or less, preferably 100 parts by weight or less, preferably 100 parts by weight of the monomer used in the second stage. 1.5 parts by weight or less. If this amount is too large, the water resistance of the finally obtained inkjet recording medium may be lowered.
In the second stage polymerization, the additional nonionic surfactant is added as a dispersion or emulsion together with the monomer added in the second stage and the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group. Convenient.
In the second stage polymerization, it is not preferable to use an anionic surfactant or to add it to the latex after the polymerization because the cation stability of the resulting binder composition for an ink jet recording medium is lowered. .

  In the second stage polymerization, the polymerization temperature, the stirring conditions, the method for adding the monomer, etc. are not particularly limited. The polymerization is carried out until the polymerization conversion finally becomes usually 90% by weight or more, preferably 93% by weight or more, more preferably 95% by weight or more. If the final polymerization conversion is too low, it may take a long time to remove unreacted monomers.

  After the completion of the polymerization, the concentration of the unreacted monomer is removed, the concentration is adjusted by dilution or concentration, the pH is adjusted, and the like to obtain a binder composition for an ink jet recording medium.

  The solid content concentration of the binder composition for inkjet recording media is not particularly limited, but is usually 3 to 60% by weight, preferably 5 to 50% by weight, and more preferably 10 to 50% by weight.

The pH of the ink jet recording medium binder composition used in the present invention is preferably adjusted in the range of 2.0 to 7.0.
The method for adjusting the pH is not particularly limited, and can be carried out by adding a basic compound or an acidic compound to the ink jet recording binder composition.
The basic compound is not particularly limited, but ammonia or amine is preferably used.
The amine is preferably a tertiary amine, and specific examples thereof include trimethylamine, triethylamine, triethanolamine, dimethylethanolamine, diethylethanolamine, triisopropanolamine, butyldiethanolamine and the like.
These basic compounds may be used alone or in combination of two or more.
As the basic compound, alkali metal hydroxides such as potassium hydroxide, sodium hydroxide and lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide can also be used. .
In order to lower the pH of the ink jet recording binder composition, an acidic compound such as carbon dioxide, hydrochloric acid, nitric acid or sulfuric acid may be used.
What is necessary is just to select the usage-amount of these basic compounds and acidic compounds so that pH can be set to the said range, and it is not specifically limited.

  The binder composition for an inkjet recording medium thus obtained is an aqueous dispersion in which polymer particles are dispersed in an aqueous medium, and the volume average particle diameter of the polymer particles is usually 10 to 150 nm, preferably 30-130 nm.

The weight average molecular weight of the tetrahydrofuran-soluble component of the polymer constituting the binder composition for an inkjet recording medium used in the present invention is preferably in the range of 5,000 to 200,000, more preferably 15,000 to 200,000. It is in.
Moreover, the glass transition temperature of the polymer which comprises the binder composition for inkjet recording media used by this invention is although it does not specifically limit, Usually, it is -60- + 100 degreeC.
Moreover, the polymer which comprises the binder composition for inkjet recording media used by this invention has a gel content (methyl ethyl insoluble matter) of 10 to 85 weight% normally, when methyl ethyl ketone is used as a solvent.

The coating composition for inkjet recording media of the present invention comprises a pigment in addition to the binder composition for inkjet recording media of the present invention.
Examples of the pigment include silica, alumina, calcium carbonate, magnesium carbonate, kaolin, talc, titanium oxide, zinc oxide, aluminum oxide, barium sulfate, calcium sulfate, magnesium silicate, aluminum silicate, diatomaceous earth, zeolite, aluminum hydroxide, And inorganic pigments such as magnesium hydroxide; organic pigments such as hollow particles, styrene plastic pigments, and acrylic plastic pigments.
Among these, inorganic pigments are preferable, and inorganic pigments having a small particle diameter such as colloidal silica and colloidal alumina are particularly preferable. The blending amount is usually in the range of 100 to 5,000 parts by weight, preferably 200 to 2,000 parts by weight with respect to 100 parts by weight of the solid content of the binder composition for inkjet recording media.

The coating composition for inkjet recording media of the present invention preferably contains a crosslinking agent for crosslinking the binder composition for inkjet recording media of the present invention.
The cross-linking agent accelerates the reaction between the compound having a group capable of reacting with the group of the polymer constituting the ink jet recording medium binder composition or the reaction group of the polymer constituting the ink jet recording medium binder composition. As long as it is a compound, it is not particularly limited, and specific examples thereof include diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidylcyclohexane, N, N-diglycidyl- Epoxy crosslinking agents such as 4-glycidyloxyaniline, sorbitol polyglycidyl ether, and glycerol polyglycidyl ether; Aldehydic crosslinking agents such as formaldehyde and glycoxal; 2,4-dichloro-4-hydroxy-1,3,5-s- Active halogen such as triazine Crosslinking agent; 1,3,5-tris acryloyl - hexahydro -s- triazine, active vinyl compounds such as bis-vinylsulfonyl methyl ether; boric acid and salts thereof; borax; aluminum alum; and the like.

  Since the binder composition for an inkjet recording medium of the present invention contains a water-soluble polymer compound containing an alcoholic hydroxyl group as a constituent component, a crosslinking agent selected from boric acid and salts thereof and an epoxy-based crosslinking agent is used. preferable. The most preferred crosslinking agent is a crosslinking agent selected from boric acid and its salts. Boric acid and its salt mean oxygen acid and its salt having a boron atom as a central atom, specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, and octaborane. Acids and their salts are included.

  The amount of the crosslinking agent used depends on the type of polymer constituting the ink jet recording binder composition used, the type of crosslinking agent, the type of pigment particles blended in the ink jet recording coating composition, and the weight constituting the binder. Although it varies depending on the ratio to the coalescence, it is generally 0.5 to 50 parts by weight, preferably 1 to 40 parts by weight per 100 parts by weight of the polymer constituting the binder.

The coating composition for an inkjet recording medium of the present invention includes, in addition to the binder composition for an inkjet recording medium of the present invention, a pigment and a crosslinking agent, components commonly used in this field, for example, a pigment dispersant, a dye, Thickener, fluidity improver, antifoaming agent, foam suppressor, mold release agent, foaming agent, penetrating agent, fluorescent whitening agent, UV absorber, antioxidant, antiseptic, antifungal agent, waterproofing agent A wet paper strength enhancer, a dry paper strength enhancer, a dye fixing agent, and the like can be blended.
The amount of these components used, the method of blending into the coating composition for inkjet recording media, and the like are appropriately selected within a range that does not impair the object of the present invention.

  The method for preparing the coating composition for an inkjet recording medium is not particularly limited. Generally, a dispersing machine is used, and the binder composition for an inkjet recording medium and other compounding ingredients are added and dispersed as necessary. Let In addition, the total solid content concentration of the coating composition for inkjet recording media is usually 5 to 60% by weight, preferably 10 to 50% by weight.

  The method of blending the crosslinking agent into the inkjet recording medium coating composition is not particularly limited, and after blending the crosslinking agent into the ink jet recording medium binder composition, other components such as pigments are blended into the ink jet recording medium. A coating composition may be prepared, a pigment may be blended and then a crosslinking agent may be blended, or both may be blended simultaneously.

The ink jet recording medium of the present invention is formed by coating the support composition with the ink jet recording medium coating composition, and is formed by coating at least one layer of the ink jet recording medium coating composition of the present invention. Has a layer.
The ink jet recording medium of the present invention may have at least one ink receiving layer formed by coating the coating composition for ink jet recording medium of the present invention, and may have a multilayer structure including an ink receiving layer as necessary. For example, an under layer may be provided under the ink receiving layer.
In the ink jet recording medium of the present invention, the outermost surface layer of the coating layer is preferably a layer formed by coating the composition for ink jet recording medium of the present invention.

The support constituting the ink jet recording medium is not particularly limited, and may be appropriately selected according to the purpose of use of the ink jet recording medium and the recording apparatus. For example, base paper such as newspaper base paper, high-quality base paper, medium base paper, etc .; coated paper coated with polyvinyl alcohol, starch, etc. on the base paper; coated paper with a coating layer mainly composed of pigment, art paper Coated paper such as cast paper; synthetic paper (polypropylene resin-based multilayer film, paper with both sides covered with polyethylene); resin film such as polyester film and polyvinyl chloride film; metal, glass, ceramic, etc. And the like.
Of these, base paper, coated paper, and synthetic paper are preferable.

The method for applying the coating composition for an inkjet recording medium of the present invention on a support is not particularly limited. For example, it can apply | coat using common coaters, such as a roll coater, an air knife coater, a blade coater, a rod blade coater, a curtain coater, a bar coater, a die coater, a gravure coater.
The coating amount on the support is not particularly limited, but is usually 1 to 50 g / m ² , preferably 3 to 30 g / m ² . The thickness of the coating film is usually 10 to 40 μm.
After coating the coating composition for inkjet recording media onto a support, the coating layer can be formed on the support by heating at an appropriate temperature in the range of 40 to 150 ° C., if necessary.

  If necessary, the inkjet recording medium of the present invention may be subjected to a smooth finish by calendering with a super calender, soft calender, etc., under heating and pressurization, or while the coating film is in a wet state. By performing a so-called cast coating method in which the smoothness of the mirror surface is copied onto the surface of the coating layer by drying with a mirror surface of a heating dryer, the surface can be provided with smoothness and gloss.

  The ink jet recording medium of the present invention is particularly useful as a recording medium (sheet) by an ink jet recording method for recording by ejecting small droplets of ink, but also used as a sheet for water-based ink printing such as offset printing and flexographic printing. it can.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. In the examples, “%” and “parts” are based on weight unless otherwise specified.
Moreover, the evaluation method of each characteristic is as follows.

[Ratio of water-soluble polymer compound bound or adsorbed to polymer (grafting efficiency)]
40 g of a binder composition for an inkjet recording medium having a solid content concentration of 30% was cast on a glass plate with a frame (16 cm × 23 cm) and dried at 20 ° C. Get a film. This film is cut into a square of about 4 cm square, and about 2.5 g is accurately weighed (A) (unit: g) in a 325-mesh wire netting cage, and this is placed on the top of the Soxhlet extractor. Add 300 ml to the flask at the bottom of the Soxhlet extractor and reflux at 100 ° C. for 100 hours. Next, the film residue in the metal mesh cage is washed with distilled water and dried under reduced pressure at 100 ° C., and the weight (B) (unit: g) of the residue is measured. The weight (A) and (B) of the film before and after immersion, the amount of water-soluble polymer compound (C) (unit: g) in the film before immersion calculated from the amount charged during polymerization and the polymerization conversion rate are expressed by the following formula ( Applying to 1), the ratio (%) of the water-soluble polymer compound bound or adsorbed to the polymer with respect to the amount of the water-soluble polymer compound used is calculated.
{[C- (AB)] × 100} / C (%) (1)
[Viscosity of binder composition for inkjet recording medium]
The solid content concentration of the binder composition for an inkjet recording medium is adjusted to 20% by weight by vacuum concentration or addition of deionized water, and then measured at 25 ° C. using a B-type viscometer.

(Volume average particle diameter of binder particles)
Using a light scattering diffraction particle size measuring device (“LS-230”: manufactured by Coulter, Inc.), an average particle size (““ It is called “volume average particle diameter”.

[Glass Transition Temperature of Binder Composition for Inkjet Recording Medium]
A binder composition for an inkjet recording medium is collected on an aluminum dish, dried at room temperature, and then vacuum dried at 40 ° C. to obtain a sample. About this sample, it measures at a temperature increase rate of 10 degree-C / min using a highly sensitive differential scanning calorimeter (The Seiko Instruments company make, brand name "EXSTAR6000").

[PH of binder composition for inkjet recording medium]
Using a pH meter (trade name “pH METER M-12”, manufactured by HORIBA), measurement is performed at 20 ° C.

[Paint formulation stability]
After 100 parts by weight of colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name “Snowtex 50”) is added 20 parts by weight of the binder composition for an inkjet recording medium in terms of solids, and the solids concentration is adjusted to 40% by weight. After adding 1 or 2 parts by weight of boric acid as a 5% aqueous solution and further adding deionized water to adjust the solid content concentration to 35% by weight, the mixture is sufficiently stirred and coated for an inkjet recording medium. The state of the work composition is visually observed and determined based on the following criteria.
(Double-circle): Aggregate does not generate | occur | produce and there is no sudden viscosity rise.
A: Aggregates are not generated, but the viscosity slightly increases.
X: Aggregates are generated.

[Viscosity of coating composition for inkjet recording medium]
After 100 parts by weight of colloidal silica (manufactured by Nissan Chemical Co., Ltd., trade name “Snowtex 50”) is added 20 parts by weight of the binder composition for an inkjet recording medium in terms of solids, and the solids concentration is adjusted to 40% by weight. After adding 1 or 2 parts by weight of boric acid as a 5% aqueous solution and further adding deionized water to adjust the solids concentration to 35% by weight, use a B-type viscometer at 25 ° C. taking measurement.

[Blank gloss]
Using a gloss meter (GM-26D, manufactured by Murakami Color Co., Ltd.), the light reflectance (%) on the surface of the ink jet recording sheet (ink jet recording medium) is measured under the conditions of an incident angle of 75 degrees and a reflection angle of 75 degrees. The larger the value, the better the glossiness of blank paper.

[Clarity]
Printing is performed on an ink jet recording sheet using an ink jet printer (PM-870C: manufactured by Seiko Epson Corporation) in an atmosphere of 23 ° C. and a relative humidity of 65%. The degree of bleeding of this printing ink is visually determined according to the following criteria.
○: No blurring △: Slightly blurring ×: Clearly blurring

[Print density]
Using an inkjet printer (PM-870C: manufactured by Seiko Epson Corporation) in an atmosphere of 23 ° C. and a relative humidity of 65%, black (BK), magenta (M), cyan (C), yellow ( Y) Each ink is solid-printed. The print density of the solid portion of each ink of this printed matter is measured using a Macbeth ink densitometer, and the numerical value of the print density for each ink is simply averaged. The higher the value, the higher the print density.

[Example 1]
(Binder composition L1 for inkjet recording media)
In a pressure vessel equipped with a stirrer (preparation vessel for emulsion for the first stage polymerization), 15 parts of deionized water, 15 parts of 2-ethylhexyl acrylate, 35 parts of methyl methacrylate, and sodium polyoxyethylene alkyl ether sulfate (anionic) Surfactant (manufactured by Kao Corporation, trade name “Latemul E118B”) (0.3 parts) was added and stirred to obtain a monomer emulsion I.
In another pressure-resistant vessel with a stirrer (a container for preparing the emulsion for the second stage polymerization), 50 parts of deionized water, 10 parts of 2-ethylhexyl acrylate, 40 parts of methyl methacrylate and a hydrophobic group (carbon number 12) 6 parts of polyvinyl alcohol (trade name “PVA-MP102” manufactured by Kuraray Co., Ltd.) (hereinafter referred to as “polyvinyl alcohol P1 having a hydrophobic group”) having a hydrocarbon group), and stirring, Emulsion II (1) was obtained.
Separately, in a pressure-resistant reaction vessel equipped with a stirrer, 85 parts of deionized water, 2 parts of polyoxyethylene lauryl ether (nonionic surfactant) (trade name “Emulgen 120” manufactured by Kao Corporation) and sodium polyoxyethylene alkyl ether sulfate 0.5 part of salt (anionic surfactant) (trade name “Latemul E118B”, manufactured by Kao Corporation) is added, the temperature is raised to 75 ° C., and the temperature is maintained at 75 ° C., and the monomer emulsification is performed in the reaction vessel. Continuous addition of product I was started, and then a polymerization initiator solution in which 0.5 part of potassium persulfate was dissolved in 10 parts of deionized water was added.
Continuous addition of monomer emulsion I was completed over 120 minutes. After completion of the addition, a post-reaction was further performed for 120 minutes. The polymerization conversion rate at this time was 98.2%. Subsequently, a polymerization initiator solution in which 0.5 part of potassium persulfate was dissolved in 10 parts of deionized water was added, and the monomer emulsion II was continuously added to the reaction vessel over 180 minutes. The post reaction was carried out for 120 minutes. Thereafter, the reaction was terminated by cooling. The polymerization conversion rate at this time was 98%, and pH was 2.5.
After removing the unreacted monomer, the solid content concentration was adjusted to obtain a binder composition L1 for an inkjet recording medium having a solid content concentration of 23%.
The obtained binder composition L1 for inkjet recording media had a viscosity of 50 mPa · s, a volume average particle diameter of 105 nm, and two glass transition temperatures of −27 ° C. and 65 ° C. were observed. The graft efficiency was 67%.
These results are shown in Table 1.

(Under layer coating composition)
In a disperser, 100 parts of wet silica (trade name “Fine Seal X-45” manufactured by Tokuyama Co., Ltd.) and 0.5 part of sodium polyphosphate are dispersed in water, and then the degree of saponification is about 98.0 to 99.0. 30 parts of polyvinyl alcohol (trade name “PVA117”, manufactured by Kuraray Co., Ltd.) having a mol% of 1,700 degree of polymerization was added as a 10% aqueous solution, mixed for 30 minutes, and an under layer coating composition having a solid content concentration of 17%. Got.

(Coating composition S1 for inkjet recording medium)
Using a disperser, 20 parts of the binder composition L1 for inkjet recording medium was added to 100 parts of colloidal silica (manufactured by Nissan Chemical Industries, trade name “Snowtex”) in terms of solid content and dispersed for 10 minutes. After adjusting the solid concentration to 40%, add 1 part of boric acid as a 5% aqueous solution and disperse sufficiently, then add deionized water to adjust the solid concentration to 35% and inkjet A recording medium coating composition S1 was obtained. The viscosity of this product was 30 mPa · s.
The coating composition stability of the coating composition for inkjet recording media was evaluated. The results are shown in Table 1.

(Inkjet recording sheet M1)
The underlayer coating composition was coated on a high-quality base paper having a basis weight of 130 g / m ² using a wire bar so that the dry weight was 15 g / m ^{2 on} one side, and dried with a hot air dryer at 120 ° C. for 60 seconds. did. On this coated paper, the inkjet recording medium coating composition S1 was applied so that the dry weight was 15 g / m ^{2 on} one side, and dried with a hot air dryer at 120 ° C. for 60 seconds to obtain a coated paper. Obtained. The obtained coated paper was conditioned overnight under an atmosphere of 23 ° C. and a relative humidity of 65%. Thereafter, the coated paper was calendered twice using a laboratory mini-calender under the conditions of 80 ° C. and linear pressure of 75 kg / cm to obtain an inkjet recording sheet M1. The recording sheet M1 was evaluated for white paper gloss, sharpness, and print density. The results are shown in Table 1.

[Examples 2-3]
(Binder compositions L2 to L3 for inkjet recording media)
Binder compositions L2 and L3 for inkjet recording media were obtained in the same manner as in Example 1 except that the amount of polyvinyl alcohol P1 having a hydrophobic group was changed as shown in the table. The properties are shown in Table 1.

(Inkjet recording sheets M2 and M3)
Inkjet recording medium coating compositions S2 and S3 were obtained in the same manner as in Example 1 except that the inkjet recording medium binder compositions L2 and L3 were used instead of the inkjet recording medium binder composition L1. These were used to obtain inkjet recording sheets M2 and M3. The characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
(Inkjet recording sheet M4)
A coating composition S4 for an inkjet recording medium was obtained in the same manner as in Example 1 except that the amount of boric acid was 2 parts, and an inkjet recording sheet M4 was obtained using this. The characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
(Manufacture of binder composition CL1 for inkjet recording media)
Instead of 6 parts of polyvinyl alcohol P1 having a hydrophobic group, polyvinyl alcohol having excellent water-solubility and having a 1,2-glycol bond (trade name “HP105” manufactured by Kuraray Co., Ltd.) (hereinafter referred to as “polyvinyl alcohol P2”) .) Polymerization was carried out in the same manner as in Example 1 except that 25 parts were used to obtain a binder composition CL1 for an ink jet recording medium.
The obtained binder composition CL1 for inkjet recording media had a viscosity of 95 mPa · s, a volume average particle diameter of 85 nm, and a glass transition temperature of 70 ° C. was observed. The graft efficiency was 70%.
These results are shown in Table 1.

(Preparation of inkjet recording sheet CM1)
The inkjet recording medium coating composition CS1 was obtained in the same manner as in Example 1 except that the inkjet recording medium binder composition CL1 was used instead of the inkjet recording medium binder composition L1, and an inkjet recording sheet was obtained using this. CM1 was obtained. The characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
(Production of Binder Composition CL2 for Inkjet Recording Medium)
In the same manner as in Example 1, a monomer emulsion I was obtained.
Further, instead of 6 parts of “polyvinyl alcohol P1 having a hydrophobic group”, polyvinyl alcohol having a saponification degree of about 87.0 to 89.0 mol% and a polymerization degree of 500 (trade name “PVA205” manufactured by Kuraray Co., Ltd.) Polyvinyl alcohol P3). ) Monomer Emulsion II (C2) was obtained in the same manner except that 15 parts were used.
Separately, in a pressure-resistant reaction vessel equipped with a stirrer, 85 parts of deionized water, 2 parts of polyoxyethylene lauryl ether (nonionic surfactant) (trade name “Emulgen 120” manufactured by Kao Corporation) and sodium polyoxyethylene alkyl ether sulfate 0.5 part of salt (anionic surfactant) (trade name “Latemul E118B”, manufactured by Kao Corporation) is added, the temperature is raised to 75 ° C., and the temperature is maintained at 75 ° C., and the monomer emulsification is performed in the reaction vessel. Continuous addition of product I was started, and then a polymerization initiator solution in which 0.5 part of potassium persulfate was dissolved in 10 parts of deionized water was added.
The continuous addition of the monomer emulsion I was completed over 120 minutes, but after the addition was completed, it was solidified in the post-reaction stage and the polymerization could not proceed to the end, and a binder composition for an inkjet recording medium was obtained. I couldn't.

[Comparative Example 3]
(Binder composition CL3 for inkjet recording medium)
A binder composition CL3 for an inkjet recording medium was obtained in the same manner as in Example 1 except that the amount of the polyvinyl alcohol P1 having a hydrophobic group was changed as shown in the table. The properties are shown in Table 1.

(Inkjet recording sheet CS3)
An ink jet recording medium coating composition CS3 was obtained in the same manner as in Example 1 except that the ink jet recording medium binder composition CL3 was used instead of the ink jet recording medium binder composition L1. It was generated and an ink jet recording coating composition could not be obtained.

(Note to Table 1)
* 1: Polyvinyl alcohol having a hydrophobic group at one end (trade name “PVA-MP102” manufactured by Kuraray Co., Ltd.)
* 2: Polyvinyl alcohol having a 1,2-glycol bond (Kuraray Co., Ltd., trade name “HP105”)
* 3: Polyvinyl alcohol having no hydrophobic group (Kuraray Co., Ltd., trade name “PVA205”)

Table 1 shows the following.
A coating composition for an ink jet recording medium using a binder composition for an ink jet recording medium obtained by using an alcoholic hydroxyl group-containing water-soluble polymer compound having no hydrophobic group has insufficient paint blending stability. The ink jet recording medium obtained by using is inferior in glossiness and printing density of blank paper (Comparative Example 1).
Also, depending on the type and amount of the alcoholic hydroxyl group-containing water-soluble polymer compound having no hydrophobic group, a binder composition for inkjet recording media cannot be obtained in the first place (Comparative Example 2).
In addition, even when an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is used, if the amount of use is outside the range defined in the present invention, a crosslinking agent is added to the ink jet recording medium. The coating composition for coating is inferior in paint blending stability, and an ink jet recording medium cannot be obtained using this (Comparative Example 3).
In contrast, an ink jet recording medium coating composition obtained by using the ink jet recording medium binder composition of the present invention has excellent paint blending stability, and is obtained by using this together with a crosslinking agent. Is excellent in all of white paper gloss, sharpness and print density (Example).

Claims (10)

  100 parts by weight of a polymer and 1 to 35 parts by weight of an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group, and at least 30 weights of the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group % Is bonded to or adsorbed to the polymer, and a binder composition for ink jet recording media.   Polymerization of the first monomer is carried out in the presence of a nonionic surfactant and an anionic surfactant, and then the resulting latex contains an alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group and a second monomer. The binder composition for an ink jet recording medium according to claim 1, which is obtained by adding the above monomer and continuing the polymerization.   The binder composition for inkjet recording media according to claim 1 or 2, wherein the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group has a hydrophobic group at the molecular end.   The binder composition for inkjet recording media according to any one of claims 1 to 3, wherein the alcoholic hydroxyl group-containing water-soluble polymer compound having a hydrophobic group is a polyvinyl alcohol having a hydrophobic group.   The binder composition for inkjet recording media according to any one of claims 1 to 4, wherein the hydrophobic group of the alcoholic hydroxyl group-containing water-soluble polymer compound is a hydrocarbon group having 5 to 20 carbon atoms.   The coating composition for inkjet recording media formed by containing the binder composition for inkjet recording media of any one of Claims 1-5, and a pigment.   Furthermore, the coating composition for inkjet recording media of Claim 6 containing a crosslinking agent.   An inkjet recording medium obtained by coating an inkjet recording medium coating composition on a support, wherein at least one layer of the inkjet recording medium coating composition according to claim 6 is applied. An inkjet recording medium having a layer.   The inkjet recording medium according to claim 8, wherein the outermost surface layer of the coating layer is a layer formed by coating the coating composition for inkjet recording medium according to claim 6.   A method for producing an ink jet recording medium, comprising: forming a coating film comprising the coating composition for an ink jet recording medium according to claim 6 on a support; and calendering the coating film under heat and pressure.