JP2005225234A - Binder for recording sheet and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a binder for a recording sheet containing an aqueous dispersion capable of obtaining a recording sheet which is low in viscosity at ordinary temperature and low temperature, and excellent in water resistance and solvent resistance and, when used as a binder for recording sheets, excellent in an ink absorbing property, water resistance, surface strength and plasticizer resistance, and to provide its manufacturing method. <P>SOLUTION: The binder for a recording sheet containing an aqueous dispersion of a polymer obtained by emulsion polymerization while a pre-emulsifier, wherein total amount of 100 pts.wt. of a monomer capable of being radically polymerized and 10-100 pts.wt. of hydroxy group-containing water-soluble polymeric material is previously emulsified only by a homogenizer, is dropped into water. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aqueous dispersion having a low viscosity at room temperature and low temperature and excellent water resistance and solvent resistance, and further comprising the aqueous dispersion, and includes ink absorption, water resistance, surface strength, and plasticizer. The present invention relates to a recording sheet binder having excellent properties and a method for producing the same.

  In emulsion polymerization of an aqueous dispersion, it has been conventionally known to use various nonionic, anionic or cationic surfactants alone or in combination. However, since emulsions using such emulsifiers contain a large amount of surfactants, there is room for improvement in terms of water resistance and solvent resistance. When used as a binder for sheets, the ink absorbency, water resistance, surface strength and plasticizer resistance are low, and it is necessary to solve them before practical use.

  As a countermeasure against this, a method of using a water-soluble polymer such as PVA as an emulsifier instead of a surfactant (JP-A-8-92306) has been proposed, but a part of PVA is charged into a reaction vessel in advance. For this reason, the viscosity of the resulting emulsion is high, and it is necessary to lower the solid content in order to obtain a usable viscosity, so that the productivity in the drying process or the like cannot be increased. Therefore, a recording sheet having a low viscosity at normal and low temperatures, excellent water resistance and solvent resistance, and excellent ink absorption, water resistance, surface strength, and plasticizer resistance when used as a recording sheet binder is obtained. An aqueous dispersion is required.

  The present invention was made to improve the above circumstances, and has a low viscosity at room temperature and low temperature, excellent water resistance and solvent resistance, and when used as a recording sheet binder, ink absorbency, water resistance, surface It is an object of the present invention to provide a recording sheet binder containing an aqueous dispersion from which a recording sheet excellent in strength and plasticizer resistance can be obtained, and a method for producing the same.

  As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention dropped a pre-emulsion liquid in which all of the radical polymerizable monomer and the hydroxyl group-containing water-soluble polymer substance were pre-emulsified into water. When emulsification polymerization is carried out, the viscosity is low at normal temperature and low temperature, water resistance and solvent resistance are excellent, and when used as a binder for recording sheets, ink absorbency, water resistance, surface strength and plasticizer resistance are improved. It has been found that an aqueous dispersion that enables an excellent recording sheet can be obtained, and the present invention has been completed.

  Accordingly, in the present invention, a pre-emulsion liquid obtained by pre-emulsifying only 100 parts by weight of a radical polymerizable monomer and 10 to 100 parts by weight of a hydroxyl group-containing water-soluble polymer substance with a homogenizer in advance is dropped into water. A binder for recording sheet comprising an aqueous dispersion of a polymer obtained by emulsion polymerization, 100 parts by weight of a radically polymerizable monomer, and 10 to 100 parts by weight of a hydroxyl group-containing water-soluble polymer substance A method for producing a binder for a recording sheet, which comprises emulsifying the whole amount of the above in advance only with a homogenizer and performing emulsion polymerization while dropping a pre-emulsion obtained by the emulsification into water, is provided.

  According to the present invention, by carrying out emulsion polymerization while dropping a pre-emulsion liquid in which all of the radically polymerizable monomer and the hydroxyl group-containing water-soluble polymer substance are pre-emulsified in an aqueous medium, In this case, when used as a recording sheet binder, it has a low viscosity, and when used as a recording sheet binder, an aqueous dispersion is obtained from which a recording sheet excellent in ink absorbability, water resistance, surface strength, and plasticizer resistance can be obtained. It is done.

Hereinafter, the present invention will be described in more detail.
The radically polymerizable monomer used in the present invention is a (meth) acrylic acid ester having an ethylenic double bond, for example, styrene, a styrene derivative, or an alcohol having an alkyl group having 1 to 18 carbon atoms. , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, glycidyl (meth) acrylate, allyl (meth) acrylate, ethylene glycol di (meth) ) Acrylate, diethylene glycol di (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, acrylonitrile, vinyl acetate, vinyl propionate, (meth) acrylic acid, vinyl chloride, and the like. The monomers may be used alone or in combination.

  Examples of the hydroxyl group-containing water-soluble polymer substance include fully saponified polyvinyl alcohol, partially saponified polyvinyl alcohol, various polyvinyl alcohols such as cation-modified polyvinyl alcohol and anion-modified polyvinyl alcohol, and celluloses such as methylcellulose, hydroxyethylcellulose, and carboxymethylcellulose. In addition to various starches, polyethylene glycol and the like, hydroxyl group-containing acrylic water-soluble polymers and the like can be mentioned, and polyvinyl alcohols are particularly preferable.

  In particular, the average degree of polymerization of polyvinyl alcohol is preferably 200 to 3,000, more preferably 300 to 2,500. The saponification degree of polyvinyl alcohol is preferably 60 to 99 mol%. When the average degree of polymerization of polyvinyl alcohol is 200 or less than 60%, it is difficult to obtain sufficient water resistance for the obtained aqueous dispersion, and when the average degree of polymerization exceeds 3,000, the obtained aqueous system is obtained. When the viscosity of the dispersion increases and the saponification degree exceeds 99 mol%, a stable pre-emulsion necessary for polymerization may not be obtained.

  Such a hydroxyl group-containing water-soluble polymer substance is used to obtain a stable pre-emulsion and a low-viscosity aqueous dispersion in the pre-emulsification of a radically polymerizable monomer when producing an aqueous dispersion. In addition, it is an essential component for ink absorption, water resistance, surface strength, and plasticizer resistance when used as a binder for recording sheets, and the amount used is 100 parts by weight of a radically polymerizable monomer. On the other hand, the hydroxyl group-containing water-soluble polymer substance is desirably 5 to 100 parts by weight, and more preferably 20 to 60 parts by weight. If the amount used is less than 5 parts by weight, the pre-emulsion cannot be stabilized, and if it exceeds 100 parts by weight, the viscosity of the aqueous dispersion obtained may be high and the water resistance may be poor.

  The feature of the present invention is that the whole amount of the radically polymerizable monomer and the hydroxyl group-containing water-soluble polymer substance is emulsified in advance. When the whole amount of the hydroxyl group-containing water-soluble polymer substance is charged into the reaction vessel as an initial component without pre-emulsification, the viscosity of the resulting aqueous dispersion becomes high, and the viscosity of the low viscosity at room temperature and low temperature, the object of the present invention An aqueous dispersion cannot be obtained. Alternatively, a known emulsification method may be employed in which a radical polymerizable monomer and a hydroxyl group-containing water-soluble polymer substance are uniformly emulsified and dispersed in water using a homogenizer or the like.

  Further, at the time of polymerization, a nonionic surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a water-soluble polymer other than a hydroxyl group-containing water-soluble polymer substance are added to the extent that the effects of the present invention are not impaired. A functional polymer can also be used in combination. Furthermore, various chain transfer agents can be used in combination as required. Examples thereof include mercaptans such as dodecyl mercaptan, lauryl mercaptan, normal mercaptan, octyl thioglycolate, alcohols such as methanol, ethanol and butanol, and halogenated hydrocarbons such as carbon tetrachloride, dichloroethane and chloroform.

  Polymerization initiators include persulfates such as potassium persulfate and ammonium persulfate, water-soluble types such as hydrogen peroxide, t-butyl hydroperoxide and azobisamidinopropane hydrochloride, benzoyl peroxide, diisopropyl peroxy Examples include oil-soluble types such as dicarbonate, cumylperoxyneodecanoate, cumylperoxyoctoate, and azobisisobutyronitrile. These amounts may be about 0.01 to 3 parts by weight with respect to 100 parts by weight of the radical polymerizable monomer. In addition, the redox type | system | group which used reducing agents, such as acidic sodium sulfite, Rongalite, L-ascorbic acid, saccharides, amines, together can be used together as needed.

  The polymerization reaction is usually carried out at a temperature of 35 to 90 ° C. with stirring, and the reaction time is usually about 3 to 40 hours. Further, by adjusting the pH by adding a basic substance at the start or end of emulsion polymerization, it is possible to improve the standing stability, freezing stability, chemical stability, etc. of the emulsion. In this case, the resulting emulsion is preferably adjusted to have a pH of 5 to 9, and for this purpose, bases such as ammonia, ethylamine, diethylamine, triethylamine, ethanolamine, triethanolamine, dimethylethanolamine, caustic soda, caustic potash, etc. Sexual substances can be used.

  The aqueous dispersion of the present invention thus obtained is desirably polymerized so that the solid concentration is 30 to 45% by weight and the viscosity is 500 mPa · s or less (15 ° C.).

  Furthermore, additives can be added to the aqueous dispersion of the present invention depending on the purpose. Additives include film forming aids, antifoaming agents, thickeners, various stabilizers, wetting agents, leveling agents, lubricants, coloring agents, matting agents, pigments, antifungal agents and the like.

  Since the aqueous dispersion of the present invention forms a coating film having low viscosity at room temperature and low temperature and excellent water resistance and solvent resistance, it is used for impregnation of fibers, nonwoven fabrics, paper, etc., plastic film, paper, leather, etc. In particular, it can be suitably used as a recording sheet binder.

  Examples of white pigments used when the aqueous dispersion of the present invention is used as a recording sheet binder include silica, clay, talc, kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum oxide, and silica. Examples thereof include inorganic substances such as magnesium silicate, calcium silicate, aluminum silicate, aluminum hydroxide, and magnesium hydroxide, and plastic pigments such as polyethylene and polystyrene. These are used alone or in combination of two or more. In particular, silica is the most common because it is a porous pigment, does not contain impurities, and is relatively advantageous in terms of price, availability, and the like.

  The aqueous dispersion as a binder used in the present invention is 5 to 100 parts by weight, preferably 10 to 70 parts by weight, particularly preferably 30 to 50 parts by weight, in terms of dry solid content, with respect to 100 parts by weight of the white pigment. It is.

  In the present invention, if necessary, a binder can be used in combination. Examples of the binder include copolymer latex of water-soluble polymers such as polyvinyl alcohol, methyl cellulose, and polyethyleneimine. These amounts can be replaced by 20 to 60% by weight of the dry solid content of the aqueous dispersion.

  EXAMPLES Hereinafter, although a synthesis example, an Example, and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In addition, the part and% in an example show a weight part and weight%, respectively.

[Synthesis Example 1] (Synthesis of Emulsion P1)
A polymerization vessel equipped with a stirrer, a condenser, a thermometer, and a nitrogen gas inlet was charged with 500 parts of deionized water, purged with nitrogen gas for 15 minutes, and then heated to 70 ° C. Next, 520 parts of ethyl acrylate, 420 parts of butyl acrylate, 20 parts of 2-hydroxyethyl methacrylate, 10 parts of N-methylolacrylamide, 30 parts of methacrylic acid, 30% aqueous solution of polyvinyl alcohol (trade name Kuraray PVA-205) 100 parts (in terms of solid content), 450 parts of deionized water mixed and emulsified with a homogenizer, and 130 parts of a 0.3% aqueous solution of ammonium persulfate were separately added to the above polymerization vessel with stirring for 4 hours. The solution was uniformly dropped and further reacted at 70 ° C. for 2 hours to complete the polymerization. After cooling, 25% aqueous ammonia was added to adjust the pH to 6. The obtained emulsion (hereinafter referred to as P1) had a solid content concentration of 45% and a viscosity (measured with a BM type rotational viscometer at a rotor rotational speed of 6 rpm and a temperature of 23 ° C.) of 50 mPa · s. The viscosity at 5 ° C. of this product was 55 mPa · s.

  Next, an emulsion was applied onto a PET film using an applicator for 100 μm and dried at 100 ° C. for 10 minutes to form an emulsion film (thickness: about 45 μm). The film was tested for water resistance and solvent resistance by the following method.

(Test method)
Water resistance: The whitening state of the film was observed when the sample (40 mm × 40 mm) was immersed in deionized water for 24 hours.
○: No whitening Δ: Slight whitening ×: Whitening solvent resistance: The swelling ratio of the film was measured when the sample was immersed in toluene for 24 hours.

[Synthesis Examples 2 to 4] (Synthesis of emulsions P2 to P4)
In the same manner as in Synthesis Example 1, copolymer emulsions (P2 to P4) were obtained by copolymerization using the monomers, water-soluble polymers, and types of emulsifiers shown in Table 1 and the amount (%) charged. The water resistance and solvent resistance of each are also shown in Table 1. In addition, about the synthesis example 1, each preparation amount was rewritten in%.

[Synthesis Comparative Example 1] (Synthesis of Emulsion P5)
A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet is charged with 1550 parts of deionized water and 300 parts of a 30% aqueous solution of polyvinyl alcohol (trade name Kuraray PVA-205) (in terms of solid content) for 15 minutes. After replacing with nitrogen gas, the temperature was raised to 70 ° C. Next, 400 parts of methyl acrylate, 370 parts of ethyl acrylate, 30 parts of 2-hydroxyethyl methacrylate and 200 parts of vinyl acetate and 130 parts of 0.3% aqueous solution of ammonium persulfate were separately prepared. It took 4 hours with stirring to the above polymerization vessel, and was added dropwise uniformly, and further reacted at 70 ° C. for 2 hours to complete the polymerization. After cooling, 25% aqueous ammonium was added to adjust the pH to 7 to obtain an emulsion (P5). The properties are listed in Table 1.

[Synthesis Comparative Examples 2 and 3] (Synthesis of Emulsions P6 and 7)
In the same manner as in Synthesis Example 1, copolymer emulsions (P6, P7) were obtained by copolymerizing with the monomers, water-soluble polymers, emulsifier types and charge amounts (%) shown in Table 1.

[Synthesis Comparative Example 4] (Synthesis of Emulsion P8)
A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet is charged with 1000 parts of deionized water and 50 parts of a 30% aqueous solution of polyvinyl alcohol (trade name Kuraray PVA-205) (in terms of solid content) for 15 minutes. After replacing with nitrogen gas, the temperature was raised to 70 ° C. Next, 400 parts of methyl methacrylate, 150 parts of ethyl acrylate, 400 parts of butyl acrylate, 30 parts of N-methylolacrylamide, 20 parts of methacrylic acid, 100 parts of 30% aqueous solution of polyvinyl alcohol (trade name Kuraray C-506) ( (In terms of solid content), an emulsion obtained by mixing and emulsifying 450 parts of deionized water with a homogenizer and 130 parts of a 0.3% aqueous solution of ammonium persulfate are added dropwise to the above polymerization vessel uniformly with stirring for 4 hours. And further reacted at 70 ° C. for 2 hours to complete the polymerization. After cooling, 25% aqueous ammonium was added to adjust the pH to 6 to obtain an emulsion (P8). The properties are listed in Table 1.

* Weight ratio to 100 parts by weight of monomer charge Kuraray PVA-205: Kuraray brand name (polyvinyl alcohol average polymerization degree 500, saponification degree 88 mol%)
Kuraray C-506: Kuraray brand name (polyvinyl alcohol average polymerization degree 600, saponification degree 77 mol%)
Shin-Etsu C-17: Product name manufactured by Shin-Etsu Chemical Co., Ltd. (polyvinyl alcohol average polymerization degree 1700, saponification degree 98 mol%)
PEG # 20000: Product name made from NOF (polyethylene glycol, molecular weight 20000)
Neugen EA-170: Product name (polyoxyethylene nonylphenyl ether) manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Emar O: Product name (sodium lauryl sulfate) manufactured by Kao Corporation
Cation AB: Product name (octadecyltrimethylammonium chloride) manufactured by NOF Corporation

[Example 1]
100 parts of finely divided silica (manufactured by Mizusawa Chemical Co., Ltd .: average particle size 4.5 μm) is gradually added and dispersed in 400 parts of water while stirring, and 100 parts of emulsion P1 obtained in Synthesis Example 1 is added. It was prepared, applied to non-size paper with a Mayer bar so that the application amount was 5 g / m ² (dry weight solid content), dried, and then a recording sheet was formed through a super calendar to obtain test piece S-1. . The obtained test piece S-1 was measured for ink absorptivity, water resistance of the printed image, and surface strength. Separately, the emulsion P1 obtained in Synthesis Example 1 was coated on a thermal recording paper with a Meyer bar so that the coating amount was 2 g / m ² (dry weight solids) and dried to obtain a test piece K-1. . The plasticizer resistance of the obtained test piece K-1 was measured.

(Test method)
Ink absorbability: Black, magenta, cyan, and yellow were simultaneously ejected to the same location with Epson printer PM-800C, and rubbed with a paper presser plate after 1 second, and ink stains were measured.
○: White portion is not smudged △: Slightly soiled ×: Water resistance of printed image: Epson printer PM-800C is used to print black, magenta, cyan, yellow, and the printed part After dipping in water, measure the time when printing bleeding occurs.
Surface strength: Black, magenta, cyan, and yellow colors were printed with an Epson printer PM-800C, and a Gakushin type friction test was performed under a load of 200 g and 50 times to measure the peeled state of the print.
○: No printing peeling Δ: Printing peeling slightly ×: Printing peeling plasticizer resistance: Three vinyl chloride wrap films are stacked on the test piece K-1 and a load of 100 g / cm ² is applied. Observe the discoloration after standing for 24 hours at 40 ° C.
○: No discoloration △: Slightly discolored ×: Discolored

[Examples 2 to 5, Comparative Examples 1 to 3]
A paint is prepared in the same manner as in Example 1 except that the type and amount of the aqueous dispersion shown in Table 2 and the kind and amount of finely divided silica are blended, and a test piece is prepared using the paint. Evaluation was carried out by the method, and the results are shown in Table 2.

a: Average particle size 4.5 μm Mizusawa Chemical Co., Ltd. b: Average particle size 3.5 μm Fuji Silysia Chemical Co., Ltd. A: Polyvinyl alcohol Shin-Etsu Chemical PA-15
B: Polyethyleneimine Nippon Shokubai Co., Ltd. SP-018

Claims (2)

  It is obtained by emulsion polymerization while dropping a pre-emulsion liquid in which 100 parts by weight of radically polymerizable monomer and 10 to 100 parts by weight of a hydroxyl group-containing water-soluble polymer substance are preliminarily emulsified only with a homogenizer, into water. A recording sheet binder comprising an aqueous dispersion of a polymer. The total amount of 100 parts by weight of the radical polymerizable monomer and 10 to 100 parts by weight of the hydroxyl group-containing water-soluble polymer substance is pre-emulsified only with a homogenizer, and the pre-emulsion obtained by the emulsification is dropped into water. A method for producing a recording sheet binder, wherein emulsion polymerization is carried out.