JP3529978B2 - Paper coating agent - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating agent for paper. More specifically, the present invention relates to a coating agent for paper, which provides a coated paper excellent in surface properties such as water resistance and has a good compatibility with starch.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol has been used as a clear coating agent or a pigment coating agent in order to improve surface properties of paper such as surface strength, smoothness, gloss, gas barrier property, water resistance, printability and solvent resistance. (Hereinafter, polyvinyl alcohol may be abbreviated as PVA) is widely used. In recent years, the surface strength of paper tends to decrease with the increase in the proportion of southern wood and waste paper contained in pulp raw materials. Further, as the printing speed is increased, the surface strength of paper is required to be improved. In the case of barrier paper, higher barrier properties are required. In the case of paper used for offset printing using water, high water resistance is required. For such a problem, a paper coating agent comprising a modified PVA containing 1 to 10 mol% of an α-olefin unit having 4 or less carbon atoms has been proposed (JP-A-63-112794, JP-A-63-112794). Sho 6
3-85198). However, the modified PVA is
There was a problem in fluidity, and there was a problem that the coating agent aqueous solution was scattered during coating and the coated paper was not uniform.

[0003]

The object of the present invention is to obtain a coated paper which is excellent in surface strength, barrier property (a property that absorption and permeation of air, oil, organic solvent, etc. are small), water resistance and printability. Another object of the present invention is to provide a starch-based coating agent for paper, which has good fluidity of an aqueous coating agent solution.

[0004]

The above object consists of a modified polyvinyl alcohol (A) containing 1 to 20 mol% of an α-olefin unit having 4 or less carbon atoms and a starch (B), and 100 parts by weight of the component (A). By providing a paper coating agent in which the amount of the component (B) is 1 to 10000 parts by weight based on 100 parts by weight, the saccharide (C) is added to the composition in an amount of 0.1 parts by weight per 100 parts by weight of the component (A). ~ 100
This is accomplished by providing a paper coating formulation with 0 parts by weight.

[0005]

DETAILED DESCRIPTION OF THE INVENTION α of modified PVA used in the present invention
-The olefin unit is one having 4 or less carbon atoms, for example , a unit amount of ethylene, propylene, n-butene, isobutene, etc.
Body units are mentioned, but ethylene units are preferable from the viewpoint of surface properties such as water resistance of the coated paper obtained. The content of the α-olefin unit is 1 to 20 mol%, preferably 2 to 18 mol%, more preferably 2.5 to 15 mol%, and 3
-12 mol% is especially preferred. When the content of the α-olefin unit is less than 1 mol%, the water resistance of the coated paper decreases. When the content of the α-olefin unit is more than 20 mol%, the solubility of the modified PVA in hot water is lowered and the water resistance of the coated paper is lowered.

The modified PVA has a viscosity average degree of polymerization (hereinafter abbreviated as degree of polymerization) of preferably 50 to 8,000, and 100 to 8,000.
6000 is more preferable, and 200 to 4000 is particularly preferable. The degree of polymerization (P) of the modified PVA is JIS-K672.
It is measured according to 6. That is, after the modified PVA is re-saponified and purified, it is determined by the following formula from the intrinsic viscosity [η] measured in water at 30 ° C. P = ([η] × 10 ³ /8.29) ^{(1 / 0.62) When the} degree of polymerization is within the above range, the object of the present invention can be more suitably achieved.

The saponification degree of the modified PVA is 80-99.99.
Mol% is preferable, 85 to 99.9 mol% is more preferable, and 88 to 99.8 mol% is particularly preferable. If the degree of saponification is less than 80 mol%, the solubility of the modified PVA in hot water will decrease, and the water resistance of the coated paper will decrease. When the saponification degree is higher than 99.99 mol%, the coatability is lowered and the viscosity stability of the aqueous coating agent solution is lowered.

The modified PVA in the present invention is obtained by saponifying a copolymer of vinyl ester and α-olefin. As vinyl ester, vinyl formate,
Vinyl acetate, vinyl propionate, vinyl valerate,
Examples thereof include vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate and vinyl versatate, and among these, PVA
Vinyl acetate is preferred from the viewpoint of obtaining The modified PVA in the present invention may further contain an anion group or a cation group. The water solubility of the modified PVA can be improved by introducing these ionic groups, and the viscosity stability of the coating aqueous solution can be further improved. The monomer unit having an anion group or a cation group, a unit amount having a carboxyl group derived from fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or itaconic anhydride Body unit : ethylene sulfonic acid,
Monomer units having sulfonic acid groups derived from allylsulfonic acid, methallylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, etc .; vinyloxyethyl trimethyl ammonium chloride, vinyloxy butyl trimethyl ammonium chloride, vinyloxy ethyl Dimethylamine, vinyloxymethyldiethylamine, N-
Examples of the monomer unit having a cationic group derived from acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyltrimethylammonium chloride, methallyltrimethylammonium chloride, dimethylallylamine, allylethylamine and the like. To be Among these monomer units , maleic anhydride, a half ester derived from maleic anhydride, itaconic acid, allylsulfonic acid, and 2-acrylamido-2-methyl, from the viewpoint of easy availability and copolymerizability. A monomer unit derived from propanesulfonic acid, N-acrylamidomethyltrimethylammonium chloride or N-acrylamidoethyltrimethylammonium chloride is preferred. The content of these monomer units is usually 10 mol% or less, and more preferably 0.1 to 8 mol%.

The modified PVA in the present invention may contain a monomer unit other than the vinyl alcohol unit and the vinyl ester unit as long as the effects of the present invention are not impaired. Examples of such units include acrylic acid and salts thereof; acrylic acid esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, and i-propyl acrylate; methacrylic acid and salts thereof; methyl methacrylate and methacrylic acid. Methacrylic acid esters such as ethyl acidate, n-propyl methacrylate and i-propyl methacrylate; acrylamide; acrylamide derivatives such as N-methylacrylamide, N-ethylacrylamide; methacrylamide; N-methylmethacrylamide.
Methacrylamide derivatives such as N-ethylmethacrylamide; methyl vinyl ether, ethyl vinyl ether, n
-Vinyl ethers such as propyl vinyl ether and i-propyl vinyl ether; nitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride and vinylidene fluoride; allyl acetate, allyl chloride and the like allyl compounds; maleic acid, their salts or esters thereof; itaconic acid, their salts or esters thereof; be derived from isopropenyl acetate and the like; vinyl silyl compounds such as vinyl trimethoxysilane
Monomer units . The content of these monomer units is preferably 10 mol% or less, more preferably 5 mol% or less, still more preferably 3 mol% or less.

The blending ratio of the starch (B) in the paper coating agent of the present invention is 1 to 10000 parts by weight, more preferably 5 to 8000 parts by weight, and 10 to 100 parts by weight of the modified PVA (A). 5000 parts by weight is more preferable, and 20 to 3000 parts by weight is particularly preferable. As the starch (B), raw starch, raw starch degradation product, starch derivative and amylose are used. Examples of raw starch include starches obtained from wheat, corn, rice, potatoes, sweet potatoes, tapioca, sago palm and the like, and generally wheat starch,
Corn starch and potato starch are suitable. Examples of raw starch decomposition products include oxidized starch and dextrin, and oxidized starch is suitable. Examples of the starch derivative include etherified starch, esterified starch and cationized starch. If the proportion of starch is less than 1 part by weight, PVA
The effect of starch is not different from the physical properties of the polymer. When the starch content exceeds 10,000 parts by weight, the physical properties of the coated paper coated with the coating agent are the same as those of the coated paper coated with the starch itself, and the effect of the PVA polymer is not exerted.

Examples of the saccharide (C) in the paper coating agent of the present invention include monosaccharides, disaccharides, oligosaccharides and polysaccharides, with monosaccharides, disaccharides and oligosaccharides being preferred. As monosaccharides, glucose, fructose,
Examples include isomerized sugar and xylose. Examples of the disaccharide include maltose, lactose, sucrose, trehalose, palatinose, reduced maltose, reduced palatinose, reduced lactose and the like. Examples of oligosaccharides include starch syrup, isomaltoligosaccharide, fructooligosaccharide, lactose oligosaccharide, soybean oligosaccharide, xylooligosaccharide, coupling sugar, cyclodextrin compound, and the like, of which the cyclodextrin compound is preferable. As the oligosaccharide, those having 10-mer or less are preferably used. Examples of polysaccharides include pullulan, pectin, agar, konjac mannan, polydextrose, xanthan gum and the like. These sugars are preferably water-soluble or water-dispersible. The blending ratio of the saccharide (C) in the present invention is 0.1 to 1 with respect to 100 parts by weight of the modified PVA (A).
000 parts by weight, more preferably 0.2 to 200 parts by weight, further preferably 0.3 to 100 parts by weight, 0.4
˜70 parts by weight is particularly preferred. When the saccharide content is less than 0.1 part by weight, the physical properties of the mixture of the PVA polymer and the starch are the same and the effect of adding the saccharide is not obtained. If the saccharide content exceeds 1000 parts by weight, the physical properties of the saccharides are the main constituent, and the effect of the mixture of the PVA polymer and starch does not appear, and the coated paper of the present invention cannot be obtained.

The blending ratio of the PVA polymer (A) to the starch (B) and the saccharide (C) is not particularly limited as long as it is the above-mentioned use amount, but (A) and [(B) + (C). )] Is [(B) + (C)] based on 100 parts by weight of (A).
2 to 10000 parts by weight is suitable, 3 to 1000 parts by weight is preferable, and the weight mixing ratio of (B) and (C) is (B) 1
0.1 to 10000 parts by weight of (C) is suitable for 100 parts by weight, preferably 1 to 1000 parts by weight.

The paper coating agent of the present invention comprising a mixture of the PVA polymer (A) and the starch (B) has the following features. The aqueous coating agent solution for paper of the present invention has a higher transparency and a better storage stability than an aqueous solution of a coating agent for paper which is a mixture of a usual PVA polymer (A) and starch (B). Therefore, it is difficult to separate the layers, and the change in viscosity with time is small, and the handling is easy. In the paper coating agent of the present invention , this is α-having 4 or less carbon atoms.
It is considered that the olefin-modified PVA has good compatibility with starch. α-olefin modified PVA (A) and starch (B)
The aqueous solution of a coating agent for paper, which is composed of a mixture of a saccharide and a saccharide (C), has a higher transparency than the aqueous solution of a coating agent for a paper, which is composed of a mixture of the α-olefin-modified PVA and starch described above, and is left standing. The stability is good, the layers do not easily separate, the viscosity does not change with time, and the handling is easier. Since the saccharide (C) has good compatibility with the α-olefin-modified PVA (A) and the starch (B), the saccharide (C) contains the PVA-based polymer (A) and the starch (B).
It is presumed that the starch (B) plays a role as a compatibilizer, and it is considered that the starch (B) is uniformly dispersed in the aqueous solution without much aggregation. Further, in the present invention , modified P having simultaneously an anion group in α-olefin modified PVA
VA has a larger effect of the above.

The paper coating agent of the present invention has 4 carbon atoms.
It is obtained by preparing a mixed aqueous solution of the following α-olefin modified PVA (A) and starch (B). The mixed aqueous solution may be prepared by mixing the two in powder form and then adding water or pouring into water to gelatinize, or separately dissolving (A) and (B) and then mixing them. Method is adopted. When the PVA polymer (A) is mixed with the starch (B) and the saccharide (C), a method of mixing the three in powder and then adding water or pouring into water to form an aqueous solution,
A method in which (A) and (B) are mixed in a powder form and then water is added or poured into water to form an aqueous solution, and then (C) is directly added to the aqueous solution as a powder and dissolved. After mixing with, add water or add to water to make an aqueous solution and then leave 1
Any method such as a method of mixing the aqueous solutions of the three parties and a method of mixing the three solutions separately into aqueous solutions may be adopted. The concentration of solids (total solids) in the paper coating agent of the present invention is preferably in the range of about 0.1 to 65% by weight from the viewpoint of coatability of the coating agent aqueous solution. The paper coating agent of the present invention can be used in a high-concentration aqueous solution because it has good coatability even when the concentration of the aqueous solution is increased. The preferred concentration is 3 to 55%, more preferably 4
~ 55%.

In the paper coating agent of the present invention, if necessary, water resistance agents such as glyoxal, urea resins, melamine resins, polyvalent metal salts and water-soluble polyamide resins; glycols, plasticizers such as glycerin, and ammonia. A pH adjusting agent such as caustic soda, sodium carbonate, and phosphoric acid; various additives such as a defoaming agent, a release agent, and a surfactant can also be added. Further, the paper coating agent of the present invention includes non-modified PVA, carboxyl-modified PVA, and sulfonic acid group-modified PVA.
VA, acrylamide modified PVA, cationic group modified PV
A, various modified PVs such as long chain alkyl group modified PVA
A: Water-soluble polymers such as casein and carboxymethyl cellulose; synthetic resin emulsions such as styrene-butadiene latex, polyacrylic ester emulsion, vinyl acetate-ethylene copolymer emulsion, vinyl acetate-acrylic ester copolymer emulsion It can also be used in combination within a range that does not inhibit the effect of.

The coating amount of the paper coating agent of the present invention is not particularly limited, but is usually 0.1 to 30 g / m in terms of solid content.
It is about ² . The paper targeted by the paper coating agent of the present invention is not particularly limited, and examples thereof include paperboard such as Manila balls, white balls, and liners; printing paper such as general high-quality paper, medium-quality paper, and gravure paper. Examples of coaters used when applying the paper coating agent of the present invention include air knife coaters, blade coaters, roll coaters, and size press coaters. The coating agent for paper of the present invention is applied to the surface of paper using these coaters, dried in a drying step, and then finished through a super calendar.

When the paper coating agent of the present invention is used as a paper pigment coating agent, pigments such as clay, kaolin, calcium carbonate, titanium white, and satin white are used. As the dispersant for these pigments, sodium pyrophosphate, sodium hexametaphosphate, sodium polyacrylate, etc. are used. When used as a pigment coating agent for paper, the amount of the modified PVA used is preferably 0.5 to 15 parts by weight with respect to 100 parts by weight of the pigment,
1 to 10 parts by weight is more preferable. The solid content concentration of the pigment coating liquid is appropriately selected from the range of 30 to 65% by weight.

[0018]

The present invention will be described in more detail by the following examples. In the following examples, "part" and "%" mean weight basis unless otherwise specified.

<< Evaluation Method of Coating Agent Aqueous Solution >> The physical properties of the coating agent aqueous solution were evaluated by the following methods. <Aqueous solution viscosity> 3 using a Brookfield viscometer
It was measured at 0 rpm, 30 ° C. or 50 ° C. <Transparency of aqueous solution> Hitachi spectrophotometer (Hitachi Ltd.)
The transmittance of the coating agent aqueous solution can be measured by the wavelength:
It was measured at 650 nm, cell width: 10 mm, and 20 ° C.

<< Physical Properties of Coated Paper >> The physical properties of the coated paper were evaluated by the following methods. <Wetlab Method> About 0.1 ml of ion-exchanged water at 20 ° C. was dropped on the surface of the coated paper, and the surface was rubbed with a fingertip, and the elution state of the coating agent was observed, and the following 5 grades were evaluated. 5: Excellent water resistance and no slimy feel. 4: There is a slimy feel, but there is no change in the coating layer. 3: Part of the coating agent is emulsified. 2: The entire coating agent is re-emulsified. 1: The coating agent dissolves. <Wet Pick Method> After the coated surface was moistened with water at 20 ° C., the picking occurrence state was observed using an RI tester (manufactured by Mei Seisakusho), and the following five grades were evaluated. 5: No picking occurred. 4: Picking occurs very slightly. 3: Picking occurs considerably. 2: Picking occurs on almost the entire surface. 1: Picking occurs on the entire surface. <Printability> Using a RI printability tester, snap dry ink (manufactured by Dainippon Ink & Co., Inc.) was applied to a film thickness of 5 μm, and the ink acceptability and print gloss etc. were observed. Evaluated comprehensively. Excellent: The print density is high, there is no print density unevenness, and the boundary between the printed part and the non-printed part is clear. Good: The print density was slightly thin, the print density was slightly uneven, the print area was slightly blurred, and the boundary between the print area and the non-print area was somewhat unclear. Acceptable: The print density is low, the print density is considerably uneven, and the print area is considerably blurred, and the boundary between the print area and the non-print area is unclear. <Surface Strength> Using an IGT printability tester, IGT pick oil M
Ink (manufactured by Dainippon Ink and Chemicals, Inc.) was used, and printing was carried out at a printing pressure of 35 kg / cm and a spring drive B.
The larger the value, the higher the surface strength. <Air permeability> The air permeability was measured by an Oken type air permeability measuring device. The larger the value, the higher the barrier property. Table 1 shows the details of the PVA-based polymer used.

[0021]

[Table 1]

Example 1 A mixture of modified PVA (P-1) containing 5 mol% of ethylene, oxidized starch MS-3800 (Nippon Shokuhin Kako Co., Ltd.) and trehalose (Hayashibara: Trehaose) was used. It was heated and dissolved in hot water of 95 ° C. for 2 hours to prepare a coating agent aqueous solution having a solid content concentration of 6%. Using a test size press (made by Kumagai Riki Kogyo), basis weight 64 g /
An aqueous solution of the coating agent was size-press coated at 50 ° C. on a high-quality paper of m ² . Nip pressure 13kg for size press coating
/ Cm, 60 m / min. Then, using a cylinder type rotary dryer dryer, 105 ° C, 1
It was dried for a minute. The coating amount in terms of solid content of the coating agent was 1.2 g / m ² (both sides). After controlling the humidity of the obtained coated paper at 20 ° C. and 65% RH for 72 hours, the physical properties of the coated paper were measured. The results are shown in Table 2.

Examples 2 to 5 Coated papers were prepared in the same manner as in Example 1 except that the modified PVA used in Example 1 was replaced with the modified PVA shown in Table 1 and the sugars shown in Table 2. It was manufactured and the physical properties of the coated paper were measured. The results are shown in Table 2.

Comparative Examples 1 to 3 As Comparative Examples 1 and 2, coated papers were produced and coated in the same manner as in Example 1 except that the modified PVA used in Examples 1 and 2 was used alone. The physical properties of the paper were measured. Comparative Example 3
As the above, a coated paper was produced in the same manner as in Example 1 except that the oxidized starch MS-3800 was used alone, and the physical properties of the coated paper were measured. The results are shown in Table 2.

Comparative Examples 4 to 6 Instead of the modified PVA used in Example 1, the non-modified PVA or modified PVA shown in Table 1 was used.
A coated paper was produced in the same manner as in Example 1, and the physical properties of the coated paper were measured. The results are shown in Table 2.

[0026]

[Table 2]

Example 6 Aqueous solution 7 containing 0.3 part of sodium polyacrylate
Kaolin clay 100 while vigorously stirring 3.5 parts
An aqueous dispersion of kaolin clay was prepared by adding parts. A mixture of ethylene-modified PVA (P-1) shown in Table 1 and oxidized starch MS-3800 and trehalose was heated and dissolved in hot water of 95 ° C for 2 hours to prepare an aqueous solution having a solid content concentration of 15%. To 35 parts of the aqueous solution, 173.5 parts of an aqueous dispersion of kaolin clay was added and mixed to prepare an aqueous coating agent solution having a solid content concentration of 50%. This coating agent aqueous solution was applied to a fine paper base paper (basis weight 60 g /
m ² ), so that the solid content coating amount is 15 g / m ² and dried at 105 ° C. for 2 minutes, and then the surface temperature is 85 ° C.
Calendar finishing was performed under a linear pressure of 100 kg / cm. After controlling the humidity of the obtained coated paper at 20 ° C. and 65% RH for 72 hours, the physical properties of the coated paper were measured. The results are shown in Table 3.

Examples 7 to 9 Coated papers were prepared in the same manner as in Example 6 except that modified PVA shown in Table 1 and sugars shown in Table 3 were used instead of the modified PVA used in Example 6. It was manufactured and the physical properties of the coated paper were measured. The results are shown in Table 3.

Comparative Examples 7 to 9 As Comparative Examples 7 to 8, coated papers were produced and coated in the same manner as in Example 6 except that the modified PVA used in Examples 6 to 7 was used alone. The physical properties of the paper were measured. Comparative Example 9
As the coated paper, the coated paper was manufactured in the same manner as in Example 6 except that the oxidized starch MS-3800 was used alone, and the physical properties of the coated paper were measured. The results are shown in Table 3.

Comparative Examples 10 to 12 In place of the modified PVA used in Example 6, the unmodified PVA or modified PVA shown in Table 1 was used, except that
Coated paper was produced in the same manner as in Example 6, and the physical properties of the coated paper were measured. The results are shown in Table 3.

[0031]

[Table 3]

[0032]

As is apparent from the above examples, the paper coating agent of the present invention comprises a composition of a PVA polymer and starch, and has excellent compatibility with each other.
Since it is possible to obtain the same level of physical properties as the PVA-based polymer alone with a small amount of the PVA-based polymer, and it is possible to reduce the viscosity of the aqueous coating agent solution for paper,
It is possible to increase the concentration of the aqueous coating agent solution for paper and has excellent workability. When the coating agent for paper of the present invention is used as a surface treatment agent for paper, a coated paper which is not colored and is excellent in surface strength, air permeability and printability can be obtained. Further, when the paper coating agent of the present invention is used as a paper pigment coating agent, the viscosity of the aqueous paper coating agent solution is not colored, and a coated paper excellent in water resistance strength and printability is obtained. Since it can be lowered, the concentration of the aqueous coating agent solution for paper can be increased and the workability is excellent.

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-56-14544 (JP, A) JP-A-6-73259 (JP, A) JP-A-10-245797 (JP, A) JP-A-63- 85198 (JP, A) JP 63-112794 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (3)

(57) [Claims] 1. A modified polyvinyl alcohol (A) containing 1 to 20 mol% of ethylene units and a starch (B), wherein the compounding amount of the component (B) is 1 to 10000 parts by weight relative to 100 parts by weight of the component (A). Is a coating agent for paper. 2. An α-olefin unit having 4 or less carbon atoms is 1
20 mole% containing denatured polyvinyl alcohol (A), made from starch (B) and a saccharide (C), component
The compounding amount of the component (B) is 1 to 100 parts by weight of (A).
A coating agent for paper , which is 10000 parts by weight and the compounding amount of the component (C) is 0.1 to 1000 parts by weight with respect to 100 parts by weight of the component (A). 3. The paper coating agent according to claim 2, wherein the saccharide (C) is at least one saccharide selected from monosaccharides, disaccharides and oligosaccharides.