JP6909125B2 - Coating agent and coated product made by applying it - Google Patents

Description

The present invention relates to a coating agent having excellent high-speed coatability and a coated product obtained by applying the coating agent. The present invention also relates to a coated product in which the coating agent is applied to the surface of a paper base material or a film base material.

Polyvinyl alcohol (hereinafter, may be abbreviated as PVA) is a crystalline water-soluble polymer, and its aqueous solution is used as a coating agent. The aqueous solution is widely used as a coating agent for paper in order to improve the surface properties of paper such as surface strength, smoothness, gloss, gas barrier property, water resistance, printability, and oil resistance.

In the field of coating agents for paper as described above, in recent years, the coating speed has been improved for the purpose of improving productivity. Therefore, for example, the shear rate at the time of applying a coating solution using a blade coater is 10 6 ^{/ s} or more. However, when a conventional PVA aqueous solution is applied at such a shear rate, the PVA in the aqueous solution tends to be oriented and crystallized, so that it is difficult to uniformly apply the coating liquid to the paper. .. As a method for solving such a problem, a method for lowering the degree of polymerization or saponification of PVA, a method for introducing an ionic group or a hydrophobic group into PVA, and the like can be considered.

However, when PVA having a low saponification degree or PVA having an ionic group or a hydrophobic group introduced therein is used, there are problems that the water resistance of the dried film is low and the drying rate is slow. Further, when PVA having a low degree of polymerization is used, there is a problem that the film strength is low and the surface strength of the obtained coated paper is not sufficiently improved.

Patent Document 1 describes a coating agent for paper containing PVA obtained by polymerizing a vinyl ester at a high temperature under pressure and then saponifying it. By increasing the amount of 1,2-glycol bond in the main chain of PVA, the orientation and crystallization of PVA in the aqueous solution under high shear were slightly suppressed, but it was still insufficient. Further, the PVA has a problem that it has low heat resistance and is easily colored.

Patent Document 2 describes a coating material using a vinyl alcohol-based resin having 1,2-glycol units in the side chain, which is obtained by copolymerizing vinyl ester and vinyl ethylene carbonate and then saponifying and decarboxylating them. Has been described. By containing 1,2-glycol units in the side chain of the vinyl alcohol-based resin, the orientation and crystallization of the vinyl alcohol-based resin in the aqueous solution under high shearing are suppressed, and high-speed coatability is improved. However, since the content of 1,2-glycol units is high, there is a problem that the crystallinity is lowered and the water resistance is lowered.

Japanese Unexamined Patent Publication No. 11-279896 JP-A-2002-241433

The present invention has been made to solve the above problems, and provides a coating agent composed of an aqueous PVA solution capable of forming a film having excellent high-speed coatability and excellent water resistance and strength. With the goal. Another object of the present invention is to provide a coated product having excellent surface characteristics.

The subject is a coating agent composed of an aqueous solution containing PVA, wherein the aqueous solution contains 5 to 20 parts by mass of the polyvinyl alcohol with respect to 100 parts by mass of water, and the polyvinyl alcohol is the following formula (1). And (2) are satisfied by providing a coating agent.
60,000 ≤ Mw ≤ 600,000 (1)
1.5 ≤ Mm / Mw ≤ 6 (2)
Mw: Weight average molecular weight of the polyvinyl alcohol Mm: Molecular weight at which the signal intensity is 1/1000 of the peak top molecular weight in the elution curve of the polyvinyl alcohol obtained by GPC measurement.

A coated product in which the coating agent is applied to the surface of the base material is a preferred embodiment of the present invention. A release paper base paper obtained by applying the coating agent to the surface of a paper base material is a more preferable embodiment of the present invention, and the release paper base paper and a release layer formed on the surface of the release paper base paper are formed. The release paper to have is a more preferable embodiment.

The coating agent composed of the PVA aqueous solution of the present invention is excellent in high-speed coatability. Moreover, the film obtained by using the coating agent is excellent in water resistance, strength, crystallinity and gas barrier property. Further, the coated product obtained by using such a coating agent has excellent surface properties.

It is an elution curve of PVA obtained by GPC measurement in Example 1. It is a figure which plotted the viscosity of the PVA aqueous solution with respect to the shear rate in Example 1, Comparative Example 1 and Comparative Example 6.

The coating agent of the present invention comprises an aqueous solution containing PVA, the aqueous solution containing 5 to 20 parts by mass of the polyvinyl alcohol with respect to 100 parts by mass of water, and the polyvinyl alcohol having the following formula ( It satisfies 1) and (2).
60,000 ≤ Mw ≤ 600,000 (1)
1.5 ≤ Mm / Mw ≤ 6 (2)
Mw: Weight average molecular weight of the polyvinyl alcohol Mm: Molecular weight at which the signal intensity is 1/1000 of the peak top molecular weight in the elution curve of the polyvinyl alcohol obtained by GPC measurement.

Mw in the above formulas (1) and (2) is the weight average molecular weight of the PVA. The Mm (maximum molecular weight) in the above formula (2) is a molecular weight at which the signal intensity is 1/1000 of the peak top molecular weight in the elution curve of the PVA obtained by GPC (gel permeation chromatography) measurement. The weight average molecular weight (Mw) and the maximum molecular weight (Mm) of the PVA are determined by GPC measurement. In the GPC measurement, polymethylmethacrylate is used as a standard substance. Further, HFIP (hexafluoroisopropanol) is used as the mobile phase, and a column for HFIP is used as the column. Specifically, the GPC measurement in the present invention is performed by the method described in the examples.

The weight average molecular weight (Mw) of the PVA needs to satisfy the following formula (1).
60,000 ≤ Mw ≤ 600,000 (1)

When the weight average molecular weight (Mw) of the PVA is 60,000 or more, a film having excellent water resistance and strength is formed. The weight average molecular weight (Mw) is preferably 90,000 or more. On the other hand, when the weight average molecular weight (Mw) is 600,000 or less, the viscosity of the aqueous solution of PVA becomes appropriate, the aqueous solution becomes easy to handle, and the decrease in the dissolution rate of PVA in water is suppressed. The weight average molecular weight (Mw) is preferably 300,000 or less, more preferably 250,000 or less.

Then, the weight average molecular weight (Mw) and the maximum molecular weight (Mm) of the PVA need to satisfy the following formula (2).
1.5 ≤ Mm / Mw ≤ 6 (2)

The maximum molecular weight (Mm) in the above formula (2) can be obtained from the elution curve (GPC curve) of PVA obtained by the GPC measurement. FIG. 1 is an elution curve of PVA obtained by GPC measurement in Example 1 described later. The maximum molecular weight (Mm) will be described with reference to the elution curve of FIG. The horizontal axis of the elution curve is the molecular weight converted from the elution time using a calibration curve. The calibration curve is prepared using polymethylmethacrylate (standard material). The vertical axis of the elution curve is the detected signal intensity. In the elution curve of FIG. 1, the signal intensity at the peak top molecular weight (Mp) 228,100 is 1. When a plurality of peaks are present in the elution curve, the molecular weight at the highest peak is defined as the peak top molecular weight (Mp). The maximum molecular weight (Mm) is the molecular weight at the point where the signal intensity is 1/1000 of the signal intensity at the peak top molecular weight (Mp) in the elution curve. In the elution curve of FIG. 1, the signal intensity at a molecular weight of 880,000 is 0.001. Therefore, the maximum molecular weight Mm of PVA of Example 1 is 880,000. Further, since the weight average molecular weight (Mw) of PVA in Example 1 is 211,200, the ratio (Mm / Mw) of the maximum molecular weight (Mm) to the weight average molecular weight (Mw) of the PVA is 4.2. ..

The maximum molecular weight (Mm) indicates the molecular weight of a component having a particularly high molecular weight in PVA. A PVA satisfying the above formula (2) has a ratio (Mm / Mw) of a maximum molecular weight (Mm) to a weight average molecular weight (Mw) smaller than that of a general PVA. By satisfying the above formula (2), the viscosity of the PVA aqueous solution under high shear is remarkably reduced, the high-speed coatability is improved, and the mechanical strength of the formed film is improved. (Mm / Mw) is preferably 5.5 or less, and more preferably 5 or less.

From the viewpoint of improving the water resistance and strength of the formed film, it is preferable that the weight average molecular weight (Mw) of PVA is high. However, in general, when an aqueous solution of PVA having a high weight average molecular weight (Mw) is applied under high shear, PVA tends to be oriented and crystallized in the aqueous solution. Therefore, the viscosity of the aqueous solution increases, and it is difficult to apply the aqueous solution uniformly. For these reasons, it has been difficult to apply an aqueous solution of PVA having a high weight average molecular weight (Mw) at high speed. As a result of diligent studies to solve such a problem, the present inventors remarkably increase the viscosity of the PVA aqueous solution under high shear in a component having a significantly higher molecular weight than the weight average molecular weight (Mw). I found that I would let you. As a result of further studies, most of the PVAs satisfying the above formulas (1) and (2), that is, components having a high weight average molecular weight (Mw) and a significantly higher molecular weight than the weight average molecular weight (Mw). We succeeded in obtaining PVA that does not contain PVA, and it became possible to achieve both high-speed coatability and water resistance and strength of the obtained film.

From the viewpoint of further improving high-speed coatability, the molecular weight distribution (Mw / Mn) of the PVA is preferably 1.05 to 1.95. The molecular weight distribution (Mw / Mn) is more preferably 1.80 or less, further preferably 1.70 or less, particularly preferably 1.60 or less, and most preferably 1.55 or less. The number average molecular weight (Mn) of PVA is determined by the above-mentioned GPC measurement.

The saponification degree of the PVA is preferably 80 to 99.99 mol%. If the degree of saponification is less than 80 mol%, the crystallinity of PVA may decrease, and the water resistance, strength and gas barrier property of the formed film may decrease. The saponification degree is preferably 85 mol% or more, and more preferably 90 mol% or more. On the other hand, if the degree of saponification exceeds 99.99 mol%, it may be difficult to produce PVA. The saponification degree is preferably 99.95 mol% or less.

The total amount of the vinyl ester unit and the vinyl alcohol unit with respect to all the monomer units in the PVA is preferably 50 mol% or more, more preferably 80 mol% or more, further preferably 90 mol% or more, and 95 mol% or more. Is particularly preferable, and may be 100 mol%.

The yellow index (YI) of PVA of the present invention is preferably 50 or less. The yellow index (YI) is measured according to ASTM D1925. PVA having such a good hue is preferably used as a coating agent. YI is more preferably 40 or less, further preferably 30 or less, and particularly preferably 20 or less. Here, YI uses a spectrophotometer (D65 light source, CM-A120 white calibration plate, specular reflection measurement SCE) to measure the sample of PVA powder spread on a petri dish without pressing the powder. Is required. Specifically, it is a value measured according to the method described in Examples.

The content of 1,2-glycol bond in the PVA is preferably 0.7 to 1.5 mol%. Since PVA having a 1,2-glycol bond content of 1.5 mol% or less has high crystallinity, the mechanical strength of the formed film is further improved. The content of the 1,2-glycol bond is more preferably 1.4 mol% or less, and further preferably 1.3 mol% or less. On the other hand, if the content of the 1,2-glycol bond is less than 0.7 mol%, the water solubility may decrease and it may become difficult to handle. The content of the 1,2-glycol bond is more preferably 0.9 mol% or more, and further preferably 1.1 mol% or more.

A preferred method for producing PVA includes a polymerization step of controlling a vinyl ester monomer in the presence of a radical initiator and an organic cobalt complex, and a saponification step of saponifying the obtained polyvinyl ester to obtain PVA. The method. By using such a method, PVA satisfying the above formulas (1) and (2) can be obtained.

Controlled radical polymerization is a polymerization reaction in which the growth radical terminal (active species) is placed in equilibrium with a covalent bond species (dormant species) bound to a control agent and the reaction proceeds. By performing controlled radical polymerization, side reactions are suppressed, so that a polyvinyl ester having a high weight average molecular weight and a small ratio of the maximum molecular weight to the weight average molecular weight can be obtained. In the above production method, an organic cobalt complex is used as a control agent.

Examples of the vinyl ester monomer used in the above-mentioned production method include vinyl formate, vinyl acetate, trifluoroacetic acid vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, and laurin. Examples thereof include vinyl acetate, vinyl stearate, vinyl benzoate, vinyl versatic acid and the like, but vinyl acetate is preferably used from an economical point of view.

The produced polyvinyl ester may be a copolymer of a copolymerizable ethylenically unsaturated monomer as long as the effects of the present invention are not impaired. Examples of the ethylenically unsaturated monomer include olefins such as ethylene, propylene, 1-butene and isobutene; acrylic acid, methacrylic acid, crotonic acid, (anhydrous) phthalic acid, (anhydrous) maleic acid, (anhydrous) itaconic acid and the like. Unsaturated carboxylic acid, its salt, its mono or dialkyl ester or its anhydride; acrylamide, N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamide propanesulfonic acid or its salt, acrylamidepropyldimethylamine or its acid Acrylonitrile such as a salt or a quaternary salt thereof; methacrylamide, N-alkylmethacrylicamide, N, N-dimethylmethacrylate, 2-methacrylamide propanesulfonic acid or a salt thereof, methacrylicamidepropyldimethylamine or an ester thereof or its 4 Methacrylates such as grade salts; N-vinylamides such as N-vinylpyrrolidone, N-vinylformamide, N-vinylacetamide; vinyl cyanide such as acrylonitrile and methacrylonitrile; alkylvinyl ethers, hydroxyalkylvinyl ethers, alkoxyalkylvinyl ethers and the like Vinyl ether; vinyl halide such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, vinyl bromide; vinylsilane such as trimethoxyvinylsilane, allyl acetate, allyl chloride, allyl alcohol, dimethylallyl alcohol, trimethyl- (3-) Acrylo-3-dimethylpropyl) -ammonium chloride, acrylamide-2-methylpropanesulfonic acid and the like can be mentioned. The number of carbon atoms of the ethylenically unsaturated monomer to be copolymerized is not particularly limited, but the number of carbon atoms is preferably 2 to 20.

Examples of the method for polymerizing the vinyl ester monomer include known methods such as a massive polymerization method, a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among them, a massive polymerization method in which polymerization is carried out without a solvent or a solution polymerization method in which polymerization is carried out in various organic solvents is usually adopted. In order to obtain PVA with a small ratio (Mm / Mw) of the maximum molecular weight (Mm) to the weight average molecular weight (Mw), a massive polymerization method that does not use a solvent or dispersion medium that may cause side reactions such as chain transfer is used. preferable. On the other hand, solution polymerization may be preferable from the viewpoint of adjusting the viscosity of the reaction solution and controlling the polymerization rate. Examples of the organic solvent used as a solvent in solution polymerization include esters such as methyl acetate and ethyl acetate; aromatic hydrocarbons such as benzene and toluene; lower alcohols such as methanol and ethanol. Of these, esters and aromatic hydrocarbons are preferably used to prevent chain transfer. The amount of the solvent used may be determined in consideration of the viscosity of the reaction solution according to the weight average molecular weight of the target polyvinyl alcohol. For example, the mass ratio (solvent / monomer) is selected from the range of 0.01-10. The mass ratio (solvent / monomer) is preferably 0.1 or more, and preferably 5 or less.

As the radical initiator used in the polymerization step, conventionally known azo-based initiators, peroxide-based initiators, redox-based initiators and the like are appropriately selected. Examples of the azo-based initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-2,4-). Dimethylvaleronitrile) (“V-70”) and the like, and examples of the peroxide-based initiator include diisopropylperoxydicarbonate, di-2-ethylhexyl peroxydicarbonate, diethoxyethylperoxydicarbonate and the like. Percarbonate compounds; perester compounds such as t-butylperoxyneodecanate, α-cumylperoxyneodecanate, t-butylperoxyneodecanate; acetylcyclohexylsulfonyl peroxide, diisobutyryl peroxide; 2,4 , 4-trimethylpentyl-2-peroxyphenoxyacetate and the like. Further, potassium persulfate, ammonium persulfate, hydrogen peroxide and the like can be combined with the above-mentioned initiator to prepare the initiator. In addition, examples of the redox-based initiator include a combination of the above-mentioned peroxide and a reducing agent such as sodium hydrogen sulfite, sodium hydrogen carbonate, tartaric acid, L-ascorbic acid, and longalit. The amount of the initiator used differs depending on the polymerization catalyst and cannot be unconditionally determined, and is arbitrarily selected according to the polymerization rate.

The organic cobalt complex used as a control agent in the polymerization step may contain a divalent cobalt atom and an organic ligand. Suitable organic cobalt complexes include, for example, cobalt (II) acetylacetonate [Co (acac) ₂ ], cobalt (II) porphyrin complex and the like. Of these, cobalt (II) acetylacetonate is preferable from the viewpoint of manufacturing cost.

The polymerization temperature is preferably, for example, 0 to 80 ° C. If the polymerization temperature is less than 0 ° C., the polymerization rate becomes insufficient and the productivity decreases. From this point, the polymerization temperature is more preferably 10 ° C. or higher, and even more preferably 20 ° C. or higher. On the other hand, when the polymerization temperature exceeds 80 ° C., the molecular weight distribution of the obtained polyvinyl ester becomes wide. From this point, the polymerization temperature is more preferably 65 ° C. or lower, and even more preferably 50 ° C. or lower.

It is preferable to include a termination step of stopping the polymerization reaction by adding a proton-donating polymerization terminator or a terminator represented by the following formula (I) when the desired polymerization rate is reached. By including such a stopping step, the hue of the obtained PVA becomes good.

（式中、Ｒ^１は置換基を有してもよい炭素数６〜２０の芳香族基を表し、Ｒ^２は水素原子、炭素数１〜２０のアルキル基、または置換基を有してもよい炭素数６〜２０の芳香族基を表す。）

(In the formula, R ¹ represents an aromatic group having 6 to 20 carbon atoms which may have a substituent, and R ² may have a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a substituent. Represents a good aromatic group with 6 to 20 carbon atoms.)

The proton donating polymerization terminator is a polymerization terminator capable of providing a proton radical to the radical at the end of the polyvinyl acetate chain, and preferably has a chain transfer constant of 0.1 or more with respect to vinyl acetate at 60 ° C. .. Examples thereof include sorbic acid used in Examples described later. Further, an organometallic compound having a metal-hydrogen bond or the like can also be used.

Examples of the terminator represented by the above formula (I) include 1,1-diphenylethylene, styrene, α-methylstyrene, 4-tert-butylstyrene and the like.

The number of moles of the arresting agent added is preferably 1 to 100 times, more preferably 5 to 50 times, the number of moles of the added organic cobalt complex. The temperature of the reaction solution in the termination step is the temperature at which the proton-donating polymerization inhibitor can provide a proton radical to the radical at the end of the polyvinyl acetate chain, or the polymerization terminator represented by the above formula (I) is polyvinyl acetate. The temperature may be any temperature at which it can react with radicals at the end of the chain, and is preferably 0 to 80 ° C. If the temperature of the reaction solution is less than 0 ° C., the stopping step takes too much time and the productivity is lowered. From this point, the temperature is more preferably 10 ° C. or higher, and even more preferably 20 ° C. or higher. On the other hand, when the temperature of the reaction solution exceeds 80 ° C., unnecessary polymerization of vinyl acetate proceeds and the maximum molecular weight (Mm) increases. From this point, the temperature is more preferably 70 ° C. or lower, and even more preferably 60 ° C. or lower. The time required for the stopping process is 10 minutes to 5 hours.

After the stopping step, it is preferable to carry out an extraction step in which the obtained polyvinyl ester solution is brought into contact with an aqueous solution containing a water-soluble ligand to extract and remove the cobalt complex from the polyvinyl ester solution. As described above, by performing the saponification step after removing the cobalt complex contained in the polyvinyl ester solution in advance, PVA having a good hue and being hard to gel can be obtained. Specifically, the aqueous solution and the polyvinyl ester solution, which are insoluble in each other, are vigorously stirred so that the area of the interface between the two is large, and then allowed to stand, separated into an oil layer and an aqueous layer, and then the aqueous layer is formed. All you have to do is remove it. This operation may be repeated a plurality of times.

The water-soluble ligand used in the extraction step is preferably an acid having a pKa of 0 to 12 at 25 ° C. When a strong acid having a pKa of less than 0 is used, it is difficult to efficiently extract the cobalt complex, and the pKa is preferably 2 or more. Further, it is difficult to efficiently extract the cobalt complex even when a weak acid having a pKa of more than 12 is used, and the pKa is preferably 7 or less. When the acid is a polyvalent acid, the first dissociation constant (pKa1) needs to be in the above range. The acid having a pKa of 0 to 12 is preferably a carboxylic acid, and particularly preferably acetic acid (pKa 4.76).

The pH of the aqueous solution containing the water-soluble ligand is preferably 0 to 5. The pH is more preferably 1 or more, and even more preferably 1.5 or more. The pH is more preferably 4 or less, and even more preferably 3 or less.

The polyvinyl ester obtained after the polymerization reaction is saponified to obtain PVA. At this time, the polyvinyl ester obtained by performing a stop step after the polymerization reaction may be saponified, or the polyvinyl ester obtained by performing a stop step after the polymerization reaction and then an extraction step may be saponified. ..

In the saponification step, the polyvinyl ester produced by the above method is saponified in a state of being dissolved in alcohol or hydrous alcohol to obtain PVA. Examples of the alcohol used in the saponification reaction include lower alcohols such as methanol and ethanol, and methanol is particularly preferably used. The alcohol used in the saponification reaction may contain acetone, an ester such as methyl acetate or ethyl acetate, or a solvent such as toluene. Examples of the catalyst used in the saponification reaction include hydroxides of alkali metals such as potassium hydroxide and sodium hydroxide, alkaline catalysts such as sodium methylate, and acid catalysts such as mineral acid. For the temperature of the saponification reaction, for example, the range of 20 to 60 ° C. is appropriate. When a gel-like product is precipitated as the saponification reaction progresses, PVA is obtained by pulverizing the product at that time, washing the product, and then drying the product.

By dissolving the PVA thus obtained in water, an aqueous solution in which the PVA is dissolved can be obtained. The content of PVA in the aqueous solution is 5 to 20 parts by mass with respect to 100 parts by mass of water. If the content is less than 5 parts by mass, the coating efficiency is lowered. The content is preferably 7 parts by mass or more. On the other hand, when the content exceeds 20 parts by mass, the high-speed coatability is lowered.

The aqueous solution may contain a water-soluble organic solvent as long as the effects of the present invention are not impaired. The content of the water-soluble organic solvent is preferably 10 parts by mass or less, more preferably 1 part by mass or less, and further preferably substantially not contained in 100 parts by mass of water.

The coating agent of the present invention comprises the aqueous solution of PVA. At this time, the particles may be dispersed in the aqueous solution of PVA. The particles include inorganic pigments (titanium oxide, clay, kaolin, aluminum hydroxide, calcium carbonate, talc, etc.) generally used for coated paper, inorganic particles such as silica and ceramics, and organic pigments (plastic pigments, etc.). ), SBR latex, NBR latex, vinyl acetate emulsion, ethylene / vinyl acetate copolymer emulsion, (meth) acrylic ester emulsion, vinyl chloride emulsion and other organic particles such as aqueous dispersible resins.

The coating agent may contain water, a water-soluble organic solvent, PVA, and other components other than the particles as long as the effects of the present invention are not impaired. Other ingredients include raw starch obtained from wheat, corn, rice, maltose, sweet potato, tapioca, sago palm, etc .; raw starch decomposition products such as oxidized starch and dextrin; etherified starch, esterified starch, cationized starch, etc. Starch derivatives; cellulose derivatives such as methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, etc .; monosaccharides such as glucose, fructose, isomerized sugar, xylose; maltose, lactose, sucrose, trehalose, palatinose, reduced maltose, reduced palatinose, reduced lactose, etc. Disaccharides; oligosaccharides such as water candy, isomaltulose, coupling sugar, cyclodextrin compounds; polysaccharides such as purulan, starch, agar, konjak mannan, polydextulose, xanthan gum; albumin, gelatin, casein, gum arabic, polyamide Examples thereof include resins, melamine resins, poly (meth) acrylamide, polyvinylpyrrolidone, poly (meth) sodium acrylate, anion-modified PVA, sodium alginate, and water-soluble polyester. The content of other components in the coating agent is usually 10% by mass or less.

A preferred embodiment of the present invention is a coated product in which the coating agent is applied to the surface of a base material. As the base material, a paper base material and a film base material are preferable.

As the paper base material, known paper obtained by making chemical pulp such as broadleaf kraft pulp and coniferous kraft pulp and mechanical pulp such as GP (crushed wood pulp), RGP (refiner ground pulp) and TMP (thermomechanical pulp). Paper or synthetic paper can be used. Further, as the paper base material, high-quality paper, medium-quality paper, alkaline paper, glassin paper, semi-glassin paper, or paperboard used for corrugated cardboard, building materials, white balls, chipboard, etc., white paperboard, etc. are also used. be able to. The paper substrate may contain organic and inorganic pigments, as well as paper-making auxiliary chemicals such as a paper strength enhancer, a sizing agent, and a yield improver. Further, the paper base material may be one that has been subjected to various surface treatments.

The film base material is preferably a film base material made of a thermoplastic resin. Examples of the thermoplastic resin include polyolefins, polyesters, polyamides and the like.

The method for producing the coated product is not particularly limited, and a method including a step of applying the coating agent to the base material and a step of drying the base material after the coating is applied is adopted.

Examples of the coating apparatus used for manufacturing a coated product include a 2-roll size press, a gate roll size press, a metering size press, an air knife coater, a bar coater, a roll coater, and a blade coater. The coating speed is preferably 100 to 2,000 m / min. Since the coating agent of the present invention is excellent in high-speed coating property, it can be uniformly applied to the base material even when it is applied at high speed. If the coating speed is less than 100 m / min, the production efficiency may decrease. The coating speed is more preferably 300 m / min or more. On the other hand, if the coating speed exceeds 2,000 m / min, coating may not be uniform. The coating speed is more preferably 1,800 m / min or less. The amount of coating can be arbitrarily selected according to the properties of the paper, but usually 0.05 to 10 g / m ² per side of the paper is preferable.

Drying after coating can be performed by, for example, hot air, infrared rays, a heating cylinder, or a method combining these. The dry coated material can be further improved in barrier property by humidity control and calendar treatment. As the humidity control condition, it is preferable that the moisture content of the coated product is 5 to 20% by mass. As the calendar processing conditions, the roll temperature is preferably room temperature to 200 ° C., and the roll linear pressure is preferably 20 to 350 kg / cm.

The type of the coated product is not particularly limited, and examples thereof include release paper base paper, barrier paper, oil-resistant paper, wrapping paper, paperboard, polyethylene-based release film, polypropylene-based release film, polyester-based release film, and the like. Among them, a release paper base paper obtained by applying the coating agent to the surface of a paper base material is a more preferable embodiment of the present invention. A release layer is formed on the surface of the release paper base paper. When forming the release layer, solvent-based silicone, non-solvent-based (emulsion-based, oligomer-based) silicone, and the like are used. Since solvent-based silicone contains a solvent (toluene, etc.), it is required to have a barrier property against the solvent. Further, when non-solvent type silicone is used, water resistance is required. Since the release paper base paper of the present invention satisfies these requirements, a release paper having the release paper base paper and a release layer formed on the surface of the release paper base paper is also a preferred embodiment.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1
0.17 parts by mass of cobalt (II) acetylacetonate in a reactor equipped with a stirrer, a reflux condenser, and an initiator addition port, and V-70 [2,2'-azobis (4-methoxy-) as the initiator. 2,4-Dimethylvaleronitrile)] was added in an amount of 0.63 parts by mass, the inside of the reactor was evacuated, and then the inert gas substitution into which nitrogen was introduced was carried out three times. Then, 900 parts by mass of vinyl acetate purified by simple distillation was added, and then the reactor was immersed in a water bath, heated and stirred so that the internal temperature became 30 ° C. Sampling was performed as appropriate, and the progress of polymerization was confirmed from the solid content concentration. When the conversion rate of vinyl acetate reached 21%, the water bath was replaced with ice water, and the internal temperature was rapidly cooled to 10 ° C. or lower. Here, as a polymerization inhibitor, 15.2 parts by mass of a methanol solution of sorbic acid (chain transfer constant with respect to vinyl acetate monomer at 60 ° C. exceeds 0.1) (concentration: 10% by mass, 1.52% by mass as sorbic acid). Part) was added.

After adding the polymerization inhibitor, it was connected to a vacuum line and the remaining vinyl acetate was distilled off under reduced pressure at 15 ° C. While visually checking the inside of the reactor, when the viscosity increased, distillation was continued while appropriately adding methanol, and the internal temperature was further raised to 50 ° C. and heated and stirred for 1 hour. Then, the mixture was cooled to 30 ° C., and methanol was distilled off under reduced pressure at 35 ° C. while adding ethyl acetate to obtain an ethyl acetate solution of polyvinyl acetate. 600 parts by mass of an acetic acid aqueous solution (pH 2.0) having a concentration of 25% by mass was added thereto, and the mixture was stirred for 5 minutes and then allowed to stand for 30 minutes to separate into two layers. After the aqueous layer was withdrawn with a syringe, it was connected to a vacuum line again, and the remaining ethyl acetate was distilled off under reduced pressure at 30 ° C. When ethyl acetate was distilled off, methanol was added to dissolve polyvinyl acetate, and the solution was added dropwise to deionized water to precipitate polyvinyl acetate. The polyvinyl acetate was recovered by a filtration operation and dried in a vacuum dryer at 40 ° C. for 24 hours to obtain polyvinyl acetate.

Next, 50 parts by mass of the obtained polyvinyl acetate and 200 parts by mass of methanol were added and dissolved in the same reactor as above (concentration 20% by mass), and then the water bath was heated to bring the internal temperature to 40 ° C. Was heated and stirred until. To this, 5.0 parts by mass of a methanol solution of sodium hydroxide (concentration: 14% by mass) was added, and saponification was carried out at 40 ° C. (0.70 parts by mass as sodium hydroxide). The produced gelled product was pulverized with a pulverizer, left at 40 ° C. for 1 hour, and then saponified for 1 hour, and then 200 parts by mass of methyl acetate was added to neutralize the remaining alkali. After confirming that the neutralization was completed using a phenolphthalein indicator, a solid was obtained by filtration, 500 parts by mass of methanol was added thereto, and the mixture was heated under reflux for 1 hour. Then, the solid obtained by centrifugal dehydration was dried in a vacuum dryer at 40 ° C. for 24 hours to obtain the desired PVA. The saponification degree of the PVA was measured based on JIS K6726 and found to be 99.9 mol%.

[GPC measurement]
By performing GPC measurement of PVA obtained under the following conditions using a size exclusion high performance liquid chromatography device "HLC-8320GPC" manufactured by Tosoh Corporation, the weight average molecular weight (Mw), number average molecular weight (Mn) and The maximum molecular weight (Mm) was determined. Table 1 shows the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the PVA. The maximum molecular weight (Mm) was determined as follows. The elution curve of PVA is shown in FIG. The horizontal axis of the elution curve is the molecular weight converted from the elution time, and the vertical axis is the signal intensity. A calibration curve prepared using polymethylmethacrylate (standard substance) was used for conversion from the elution time to the molecular weight. In the elution curve of FIG. 1, the signal intensity at the peak top molecular weight (Mp) 228,100 was set to 1. The signal intensity at the molecular weight of 880,000 was 0.001, which is 1/1000 of the signal intensity at the peak top molecular weight (Mp). Therefore, the maximum molecular weight Mm of PVA in Example 1 was 880,000.
Column: HFIP-based column "GMHHR-H (S)" manufactured by Tosoh Corporation, connected in series Standard sample: Polymethylmethacrylate Solvent and mobile phase: Sodium trifluoroacetate-HFIP solution (concentration 20 mM)
Flow rate: 0.2 mL / min
Temperature: 40 ° C
Sample solution concentration: 0.1 wt% (filtered with a 0.45 μm aperture filter)
Injection volume: 10 μL
Detector: RI

[Measurement of 1,2-glycol bond amount]
The obtained PVA was dried under reduced pressure at 90 ° C. for 2 days. Dissolving the PVA in DMSO-d _6, it was subjected to measurement to prepare a sample by adding a few drops of trifluoroacetic acid. ¹ H-NMR measurement was performed at 80 ° C. using a nuclear magnetic resonance apparatus "LAMBDA 500" manufactured by JEOL Ltd. The peak derived from methine of vinyl alcohol unit is assigned to 3.2 to 4.0 ppm (integral value A), and the peak derived from one methine of 1,2-glycol bond is assigned to 3.25 ppm (integral value B). The 1,2-glycol bond content was calculated in 1. The results are shown in Table 1.
1,2-Glycol bond amount (mol%) = (B / A) x 100

[Evaluation of hue (YI)]
The obtained PVA powder YI (ASTM D1925) was measured using a spectrophotometer "CM-8500d" manufactured by Konica Minolta Co., Ltd. (light source: D65, CM-A120 white calibration plate, CM-A126 Petri dish set). Use, specular reflection measurement SCE, measurement diameter φ30 mm). 5 g of the sample was added to the petri dish, and the powder was lightly tapped on the side surface to shake it without pressing the powder, and the powder was spread evenly and evenly. In this state, a total of 10 measurements were performed (each time the petri dish was shaken once and then remeasured), and the average value was obtained as the YI of the resin. The results are shown in Table 1.

[Evaluation of aqueous solution viscosity under high shear]
A PVA aqueous solution having a concentration of 10% by mass was prepared. The viscosity of this aqueous solution was measured with a high-grade flow tester. The measurement conditions are as follows. FIG. 2 is a diagram in which the viscosity of the PVA aqueous solution is plotted against the shear rate.
Equipment: Shimadzu Advanced Flow Tester 301 type Die diameter: 0.2mm
Die length: 5 mm
Temperature: 30 ° C
Preheating time: 5 minutes Shear rate: 1 x 10 ^{3 to} 5 x 10 ⁶ / sec

[Evaluation of high-speed coatability]
A PVA aqueous solution (coating liquid) having a concentration of 8% by mass was prepared. ^{This coating liquid was coated on high-quality paper (basis weight 65 g / m 2} ) with a blade coater at a coating temperature of 30 ° C., a coating speed of 1200 m / min, and a gap of 0.004 mm between the paper and the blade. The shear rate applied to the coating liquid at this time is 5 × 10 ⁶ / S. After coating, it was dried in a drum dryer at 80 ° C. for 5 minutes. To evaluate whether the coating liquid is evenly applied to the obtained coated paper, apply colored toluene to the coated surface of the coated paper with a brush, observe the colored toluene coming out from the back surface, and use the following criteria. evaluated. The results are shown in Table 1.
A: Colored toluene is not strike-through and there is no uneven coloring on the coated surface B: There is strike-through of colored toluene or uneven coloring on the coated surface C: Colored toluene is severely strike-through and coloring of the coated surface There is also unevenness

[Evaluation of water resistance]
The coating liquid obtained above was cast on a PET film and dried at a drying temperature of 60 ° C. for 3 hours to prepare a film having a film thickness of 100 μm. The obtained film was immersed in warm water at 40 ° C. for 24 hours, the insoluble matter fraction was calculated from the dry weight of the film before and after immersion, and evaluated according to the following criteria. The results are shown in Table 1.
A: Insoluble matter fraction is 70% or more B: Insoluble matter fraction is less than 70%

[Evaluation of strength]
The coating liquid obtained above was cast on a PET film and dried at a drying temperature of 60 ° C. for 3 hours to prepare a film having a thickness of 100 μm and a width of 10 mm. The obtained film was pulled by an autograph device under the condition of humidity of 90%, and the maximum stress was measured. The results are shown in Table 1.
Equipment: Shimadzu Autograph AG-5000B
Pulling speed: 500 mm / min Grasping interval: 70 mm
Temperature: 23 ° C

Example 2
When saponifying polyvinyl acetate, 85 parts by mass of polyvinyl acetate and 1615 parts by mass of methanol were added and dissolved (concentration 5% by mass), and a methanol solution of sodium hydroxide to be added to this solution (concentration 5% by mass). The target PVA was obtained in the same manner as in Example 1 except that the amount (concentration: 14% by mass) was 3.9 parts by mass (0.55 parts by mass as sodium hydroxide). The same procedure as in Example 1 was carried out except that a sample that had been resaponified and had a saponification degree of 99.9 mol% or more was used for measuring the glycol bond amount, and the viscosity of the aqueous solution under high shear was not evaluated. PVA was evaluated. The results are shown in Table 1.

Example 3
The polymerization reaction of vinyl acetate was carried out under the same conditions as in Example 1 except that 0.12 parts by mass of cobalt (II) acetylacetonate and 0.43 parts by mass of V-70 as an initiator were added. When the conversion of vinyl acetate reached 20%, the water bath was replaced with ice water, and the internal temperature was rapidly cooled to 10 ° C. or lower. 10.4 parts by mass of a methanol solution of sorbic acid (concentration: 10% by mass, 1.04 parts by mass as sorbic acid) was added as a polymerization inhibitor, and the subsequent operations were the same as those described in Example 1. Was carried out to obtain polyvinyl acetate.

Next, 45 parts by mass of the obtained polyvinyl acetate and 180 parts by mass of methanol were added and dissolved in the same reactor as above (concentration: 20% by mass). Described in Example 1 except that the amount of the methanol solution (concentration 14% by mass) of sodium hydroxide added to this solution at each stage was 15.0 parts by mass (2.1 parts by mass as sodium hydroxide). The saponification reaction was carried out in two steps in the same manner as in the method to obtain the desired polyvinyl alcohol. PVA was evaluated in the same manner as in Example 1 except that the viscosity of the aqueous solution under high shear was not evaluated. The results are shown in Table 1.

Example 4
The polymerization reaction of vinyl acetate was carried out under the same conditions as in Example 1 except that 0.08 part by mass of cobalt (II) acetylacetonate and 0.29 part by mass of V-70 as an initiator were added. When the conversion of vinyl acetate reached 22%, the water bath was replaced with ice water, and the internal temperature was rapidly cooled to 10 ° C. or lower. To this, 8.4 parts by mass (concentration: 10% by mass, 0.84 parts by mass as sorbic acid) of a methanol solution of sorbic acid was added as a polymerization inhibitor, and the subsequent operations were the same as those described in Example 1. Was carried out to obtain polyvinyl acetate.

Next, 85 parts by mass of the obtained polyvinyl acetate and 1615 parts by mass of methanol were added and dissolved in the same reactor as above (concentration: 5% by mass). Same as the method described in Example 1 except that the amount of sodium hydroxide added to this solution in a methanol solution (concentration: 14% by mass) was 15.0 parts by mass (2.1 parts by mass as sodium hydroxide). The saponification reaction was carried out to obtain the desired polyvinyl alcohol. PVA was evaluated in the same manner as in Example 1 except that the viscosity of the aqueous solution under high shear was not evaluated. The results are shown in Table 1.

Comparative Examples 1-5
In the same manner as in Example 1, polyvinyl alcohols "PVA-117 (Comparative Example 1)", "PVA-217 (Comparative Example 2)", "PVA-124HF (Comparative Example 3)", "PVA-" manufactured by Kuraray Co., Ltd. "140H (Comparative Example 4)" and "PVA-105 (Comparative Example 5)" were evaluated. However, in Comparative Example 2, a sample having a saponification degree of 99.9 mol% or more after resaponification was used for measuring the glycol binding amount. Further, for PVA of Comparative Examples 2 to 5, the viscosity of the aqueous solution under high shear was not evaluated. The results are shown in Table 1.

Comparative Example 6
An aqueous solution prepared by dissolving 95 parts by mass of PVA obtained in Example 1 and 5 parts by mass of polyvinyl alcohol "PVA-140H" manufactured by Kuraray Co., Ltd. was evaluated in the same manner as in Example 1. The results are shown in Table 1 and FIG.

Comparative Example 7
When the conversion rate of vinyl acetate reached 3% under the same conditions as in Example 1, the water bath was replaced with ice water, and the internal temperature was rapidly cooled to 10 ° C. or lower. Subsequent operations were the same as those described in Example 1 to obtain polyvinyl acetate.

Next, 50 parts by mass of the obtained polyvinyl acetate and 200 parts by mass of methanol were added and dissolved in the same reactor as above (concentration 20% by mass), and then the water bath was heated to bring the internal temperature to 40 ° C. Was heated and stirred until. To this, 5.0 parts by mass of a methanol solution of sodium hydroxide (concentration: 14% by mass) was added, and saponification was carried out at 40 ° C. (0.70 parts by mass as sodium hydroxide). The produced gelled product was pulverized with a pulverizer, left at 40 ° C. for 1 hour, and then saponified for 1 hour, and then 200 parts by mass of methyl acetate was added to neutralize the remaining alkali. After confirming that the neutralization was completed using a phenolphthalein indicator, a solid was obtained by filtration, 500 parts by mass of methanol was added thereto, and the mixture was heated under reflux for 1 hour. Then, the solid obtained by centrifugal dehydration was dried in a vacuum dryer at 40 ° C. for 24 hours to obtain the desired polyvinyl alcohol. PVA was evaluated in the same manner as in Example 1 except that the viscosity of the aqueous solution under high shear was not evaluated. The results are shown in Table 1.

Claims (7)

A coating agent consisting of an aqueous solution containing polyvinyl alcohol.
A coating agent in which the aqueous solution contains 5 to 20 parts by mass of the polyvinyl alcohol with respect to 100 parts by mass of water, and the polyvinyl alcohol satisfies the following formulas (1) and (2).
60,000 ≤ Mw ≤ 600,000 (1)
1.5 ≤ Mm / Mw ≤ 6 (2)
Mw: Weight average molecular weight of the polyvinyl alcohol Mm: Maximum molecular weight in which the signal intensity is 1/1000 of the peak top molecular weight in the elution curve of the polyvinyl alcohol obtained by GPC measurement. The coating agent according to claim 1, wherein the degree of saponification of the polyvinyl alcohol is 80 to 99.99 mol%. The coating agent according to claim 1 or 2, wherein the content of 1,2-glycol bond of the polyvinyl alcohol is 0.7 to 1.5 mol%. The coating agent according to any one of claims 1 to 3, wherein the polyvinyl alcohol has a yellow index (YI) of 50 or less, which is measured according to ASTM D1925. A coated product obtained by applying the coating agent according to any one of claims 1 to 4 to the surface of a base material. A release paper base paper obtained by applying the coating agent according to any one of claims 1 to 4 to the surface of a paper base material. A release paper having the release paper base paper according to claim 6 and a release layer formed on the surface of the release paper base paper.

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