JPH08176316A - Alkali-soluble film and its use, alkali-soluble coating agent - Google Patents

Abstract

PURPOSE: To obtain an alkali-soluble non-blocking film comprising a specific polymer and a polyvalent metal, capable of being printed, high in mechanical strength, having a stable strength and a stable dimensional characteristic, and useful as a substrate for labels, etc. CONSTITUTION: This film comprises (A) a polymer obtained by copolymerizing (i) an α, β-unsaturated carboxylic acid monomer with (ii) at least one vinylic monomer in a non-aqueous medium, and (B) a polyvalent metal (preferably either one of Mg, Ca and Zn). Therein, the component (i) is preferably methacrylic acid or acrylic acid, and at least 30 pts.wt. of the component (ii) is preferably an alkyl acrylate or alkyl methacrylate. The component A has an acid value of 70-300mg KOH/g, a number-average mol.wt. of 10000-500000, and a glass transition temperature of -30 to 120 deg.C, and is preferably insoluble in neutral or acidic water and soluble in an alkaline water.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an alkali-soluble film, its use, and an alkali-soluble coating agent. The alkali-soluble film and the alkali-soluble coating agent of the present invention are particularly useful when used in the fields of label substrates, packaging bags and processed paper. It can also be used as a laminated film with a water-soluble resin or a hydrophobic resin.

[0002]

2. Description of the Related Art Alkali-soluble films have been conventionally known. For example, in Japanese Patent Laid-Open No. 6-193000, at least one copolymer containing (meth) acrylic acid / alkyl (meth) acrylate as an essential component is used. It is described that an alkali-soluble film obtained by stretching in the axial direction and shrinking in water is used for packaging and labeling. Further, Japanese Patent Laid-Open No. 60-155212 discloses that
(Meth) acrylic acid / acrylate and optionally,
An alkali-soluble film that contains a termonomer and shrinks in water is used for temporary automobile packaging, shipping packaging,
It is described to be used for agricultural films, packaging of laundry and the like. However, both of these alkali-soluble films easily cause blocking even at room temperature,
The mechanical strength (tensile strength, tear strength, etc.) of the film is low, and there is a problem that the strength and dimensions of the film change significantly when the temperature or humidity changes, so that the application is limited.

Further, a technique of applying a alkali-soluble resin to paper to obtain reprocessed processed paper and release paper is disclosed in Japanese Patent Laid-Open No. 5-2.
It is disclosed in Japanese Patent No. 47894 and Japanese Unexamined Patent Publication No. 5-320595. However, in these recyclable processed papers and release papers, the alkali-soluble resin layer formed on the paper easily causes blocking, the alkali-soluble resin layer easily contracts due to moisture absorption and curls, and the strength is not sufficient. There is a problem.

Conventionally, in order to improve various physical properties of a polymer, there is a method of crosslinking the molecular chains of the polymer with a metal. As a method utilizing this method, Japanese Patent Publication No. 36-5
No. 885 describes a non-blocking coating composition containing a zinc ammonium complex salt and containing an aqueous dispersion of a water-insoluble addition polymer obtained by emulsion polymerization. A transparent continuous film is obtained by coating the coating composition on paper or the like and drying. However, since the film is based on hydrophobic polymers and is not alkali-soluble, once the coating composition is applied to paper, the paper can no longer be recycled. Further, since the water-insoluble addition polymer is obtained by emulsion polymerization using an emulsifier, the resin structure of the water-insoluble addition polymer is not uniform, and the continuous film is liable to whiten and the tear strength is not sufficient.

Further, Japanese Patent Publication No. 47-15597 discloses an aqueous glazing composition containing a polyvalent metal ion and an alkali-soluble resin. This aqueous composition for polishing also contains an alkali-soluble resin obtained by emulsion polymerization, using an emulsifier as in the coating composition of JP-B-36-5885. Here, the polyvalent metal ion is merely dispersed in the emulsion of the alkali-soluble resin and may act like an ionic bond on the surface of the alkali-soluble resin particle, but the metal is The salt structure is difficult to form and is not homogeneous. The resulting coating may use an emulsifier,
Whitening is easy and tear strength is not sufficient. Moreover, since this composition contains as a main component a polymer insoluble in water having a pH of 11 or less, its alkali solubility is insufficient. Further, it is difficult to form the alkali-soluble resin particles obtained by emulsion polymerization into a film by an extrusion molding process that is more efficient than the casting method, because complicated steps are required.

Japanese Examined Patent Publication No. 31-6747 discloses an emulsion of a water-insoluble resin cross-linked with dissociated ions. This also has the same problems as those of the above aqueous glazing composition.

[0007]

The problems to be solved by the present invention include printability and non-blocking property, high mechanical strength (tensile strength and tear strength, etc.), and stability against changes in temperature or humidity. It is an object of the present invention to provide an alkali-soluble film and an alkali-soluble coating agent having the above strength and dimensional characteristics.

Another problem to be solved by the present invention is printability and non-blocking property, high mechanical strength (tensile strength and tear strength, etc.), and excellent dimensional stability.
An object of the present invention is to provide a label base material which can be easily removed by alkali treatment and has excellent water resistance.
Still another problem to be solved by the present invention is to provide a packaging bag which is non-blocking, has high mechanical strength (tensile strength, tear strength, etc.), and is easily dissolved in alkaline water.

Still another problem to be solved by the present invention is to provide a recyclable processed paper which is printable, has non-blocking properties, can be easily regenerated, and has little deformation. Still another problem to be solved by the present invention is to provide a reproducible paper label which has non-blocking property, can be easily regenerated, and has little deformation. Still another problem to be solved by the present invention is to provide a release paper which is printable, has non-blocking properties, is easily reproducible, has little deformation, and has peeling properties.

[0010]

The alkali-soluble film of the present invention is a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl-based monomer. And a polyvalent metal. The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight or more of the vinyl-based monomer is an acrylic acid alkyl ester and methacrylic acid. It is preferably at least one selected from the group consisting of acid alkyl esters.

The acid value of the polymer is 70 to 300 mg KO.
H / g, number average molecular weight 10,000 to 500,000
0, a glass transition temperature of −30 to 120 ° C., insoluble in neutral or acidic water and soluble in alkaline water. The polyvalent metal is preferably at least one metal selected from the group consisting of magnesium, calcium and zinc.

The label substrate of the present invention comprises the above alkali-soluble film. The packaging bag of the present invention comprises the alkali-soluble film. The recyclable processed paper of the present invention includes the alkali-soluble film and paper laminated on the alkali-soluble film. The renewable paper label of the present invention can be obtained by printing on the alkali-soluble film of the renewable processed paper.

The release paper of the present invention further comprises a release agent layer laminated on the alkali-soluble film of the renewable processed paper. The alkali-soluble coating agent of the present invention,
It contains a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl-based monomer, a polyvalent metal, and a solvent.

The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight of the vinyl-based monomer is alkyl acrylate. It is preferably at least one selected from the group consisting of esters and methacrylic acid alkyl esters. The polymer has an acid value of 70 to 300 mgKOH / g and a number average molecular weight of 5,000.
0-500,000, glass transition temperature -30-120
C., preferably insoluble in neutral or acidic water and soluble in alkaline water.

The polyvalent metal is preferably at least one metal selected from the group consisting of magnesium, calcium and zinc. ******** The present invention is described in detail below. Alkali-soluble film and alkali-soluble coaty
Polymers contained in the alkali-soluble film and the alkali-soluble coating agent of the present invention are obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl monomer. .

The α, β- used to obtain the polymer
Specific examples of the unsaturated carboxylic acid monomer include α, β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, itaconic acid and fumaric acid; α, β such as maleic anhydride and itaconic anhydride. -Unsaturated carboxylic acid anhydrides: α, β-unsaturated dicarboxylic acid monoesters such as maleic acid monoester, fumaric acid monoester and itaconic acid monoester can be mentioned. Two or more kinds of these α, β-unsaturated carboxylic acid monomers may be used in combination. Above all, it is preferable to use at least one selected from the group consisting of acrylic acid and methacrylic acid as the α, β-unsaturated carboxylic acid monomer, since flexibility and toughness are improved.

Specific examples of the vinyl monomer used to obtain the polymer include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate,
Esters of monohydric alcohols having 1 to 18 carbon atoms such as butyl methacrylate and stearyl methacrylate with acrylic acid or methacrylic acid; nitrile group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; amide groups such as acrylamide and methacrylamide. Vinyl-containing monomer; Hydroxyl acrylate, hydroxypropyl methacrylate, and other hydroxyl-containing vinyl monomers;
Epoxy group-containing vinyl monomers such as glycidyl methacrylate; α, β such as zinc acrylate and zinc methacrylate
-Metal salts of unsaturated carboxylic acids; aromatic vinyl-based monomers such as styrene and α-methylstyrene; aliphatic vinyl-based monomers such as vinyl acetate; vinyl chloride, vinyl bromide, vinyl iodide, vinylidene chloride Halogen-containing vinyl monomers such as; allyl ethers; maleic acid derivatives such as maleic anhydride, mono- and dialkyl esters of maleic acid;
Fumaric acid derivatives such as mono- and dialkyl esters of fumaric acid; maleimide derivatives such as maleimide, N-methylmaleimide, stearyl maleimide, N-phenylmaleimide, N-cyclohexylmaleimide; mono- and dialkyl esters of itaconic acid, itaconic amides, itaconimide And itaconic acid derivatives such as itacone amide esters; alkenes such as ethylene and propylene; and dienes such as butadiene and isoprene. You may use together 2 or more types of these vinyl type monomers. Above all, it is preferable to use at least one selected from the group consisting of alkyl acrylates and methacrylic acid alkyl esters as the vinyl-based monomer because a film excellent in flexibility, toughness, gloss, and weather resistance can be obtained. In addition, when the content is 30% by weight or more of the entire vinyl monomer used, flexibility, toughness,
It is preferable because the gloss and weather resistance are further improved. further,
It is preferable that the acrylic acid alkyl ester and the methacrylic acid alkyl ester are esters of a monohydric alcohol having 1 to 18 carbon atoms and acrylic acid or methacrylic acid, because flexibility, toughness, gloss, and weather resistance are further improved.

The ratio of the α, β-unsaturated carboxylic acid monomer to the vinyl monomer used is not particularly limited, and they can be blended in any ratio. In order to obtain a flexible film while keeping the above balance, the blending ratio of the α, β-unsaturated carboxylic acid monomer and the vinyl monomer is 9:91 to 50:50.
(Weight ratio) is preferable.

The method for producing the polymer is not particularly limited as long as it is a non-aqueous reaction, and a conventionally known polymerization method can be adopted. The non-aqueous reaction method means a polymerization method that does not use water, and is a polymerization method other than an aqueous solution polymerization, an emulsion polymerization in an aqueous system, and a suspension polymerization in an aqueous system. The reason why the reaction in a non-aqueous system is preferable is that there are restrictions on the monomers that can be used in the polymerization in an aqueous solution, and the film obtained by emulsion polymerization in an aqueous system is likely to be whitened due to its heterogeneous structure and also has a high strength. Because it is not enough. Specific examples of the polymerization method include anionic polymerization, cationic polymerization and radical polymerization, but radical polymerization is preferred.

The radical polymerization initiator used in radical polymerization is not particularly limited, and specific examples thereof include
Azo initiators such as 2,2′-azobisisobutyronitrile and 2,2′-azobis (2,4-dimethylvaleronitrile); peroxides such as benzoyl peroxide and di-t-butyl peroxide Examples thereof include system initiators. You may use together 2 or more types of these radical polymerization initiators.

The polymerization mode is preferably solution polymerization or bulk polymerization using an organic solvent. The raw material monomers and, if necessary, the radical polymerization initiator may be charged all at once to carry out the polymerization, or the polymerization may be carried out while supplying the above-mentioned components to the reaction vessel at any time. Further, after a part of the solvent is charged in the reaction vessel in advance, the polymerization may be carried out by a method of supplying the raw material monomer and the radical polymerization initiator to the reaction vessel.

The solvent used in the solution polymerization is not particularly limited as long as it is a solvent other than water that does not interfere with the radical polymerization reaction, and specific examples thereof include alcohols such as methanol, ethanol and isopropyl alcohol. ;
Aromatic hydrocarbons such as benzene and toluene; acetone,
Examples thereof include ketones such as methyl ethyl ketone; aliphatic esters such as ethyl acetate and butyl acetate. You may use together 2 or more types of these solvents.

As the reaction vessel used for producing the polymer, any reaction vessel can be used. Specific examples of the reaction vessel include an ordinary tank reactor, a tubular reactor such as a kneader and a static mixer, and the like. The pressure in the reaction vessel at the time of producing the polymer may be any of reduced pressure, normal pressure and increased pressure.

The acid value of the polymer is not particularly limited, but an acid value of 70 to 300 mgKOH / g is preferable because the solubility in alkaline water and the water resistance can be balanced. When the acid value is less than 70 mgKOH / g, the film obtained is difficult to dissolve in alkaline water, and the acid value is 300.
If it exceeds mgKOH / g, the water resistance of the film may deteriorate, which is not preferable.

The number average molecular weight of the polymer is 5,000 or more. From the viewpoint of moldability, the number average molecular weight is preferably 5,000 to 500,000. A number average molecular weight of 10,000 to 500,000 is more preferable because a film having higher strength can be obtained. When the number average molecular weight is less than 5,000, the mechanical strength of the obtained film is low and the number average molecular weight is 50.
If it exceeds 50,000, moldability may deteriorate.

The glass transition temperature of the polymer is not particularly limited, but from the viewpoint of the mechanical strength and non-blocking property of the obtained film, the glass transition temperature is -30.
It is preferably ˜120 ° C. Glass transition temperature is -3
When the temperature is lower than 0 ° C, the tensile strength of the obtained film is low and blocking is likely to occur. When the glass transition temperature exceeds 120 ° C, the obtained film becomes hard and brittle.

The structure of the polymer is not limited to the linear one. Particularly, a polymer having a star-shaped polymer structure obtained by using a polyfunctional mercaptan or the like is effective because it has high tear strength and flexibility at low temperature to normal temperature. The alkali-soluble film and the alkali-soluble coating agent of the present invention include a polyvalent metal. Specific examples of polyvalent metals include beryllium, magnesium, calcium, strontium and barium group IIa metals; zinc, cadmium and mercury group IIb metals; boron, aluminum,
Mention may be made of the Group IIIb metals gallium, indium and thallium. You may use together 2 or more types of these polyvalent metals. Among them, the polyvalent metal is at least 1 selected from the group consisting of magnesium, calcium and zinc.
It is preferable that the metal is a kind of metal from the viewpoint of the elongation property, water resistance and economy of the obtained film.

It is preferable that the polyvalent metal is contained as a polyvalent metal compound (weak acid salt, oxide, hydroxide, etc.) rather than a simple substance because the polyvalent metal is likely to be uniformly contained. Specific examples of the weak acid salt of a polyvalent metal include acetates such as magnesium acetate, calcium acetate, zinc acetate, cadmium acetate, and aluminum acetate; carbonates such as magnesium carbonate, calcium carbonate, zinc carbonate, cadmium carbonate, and aluminum carbonate; Oxalates such as magnesium oxalate, calcium oxalate, zinc oxalate, cadmium oxalate and aluminum oxalate; phosphates such as magnesium phosphate, zinc phosphate, cadmium phosphate, aluminum phosphate; magnesium stearate, Examples thereof include stearates such as calcium stearate, zinc stearate, cadmium stearate and aluminum stearate.

Specific examples of polyvalent metal oxides include magnesium oxide, calcium oxide, zinc oxide, cadmium oxide, aluminum oxide and the like. Specific examples of the hydroxide of polyvalent metal include magnesium hydroxide, calcium hydroxide, zinc hydroxide, cadmium hydroxide, aluminum hydroxide and the like.

Among the compounds of polyvalent metals, magnesium acetate, calcium acetate, zinc acetate, magnesium carbonate,
It is preferable to include calcium carbonate, zinc carbonate, magnesium stearate, calcium stearate, zinc stearate, magnesium hydroxide, calcium hydroxide, and zinc hydroxide from the viewpoint of elongation, water resistance and homogeneity of the obtained film.

The above-mentioned polyvalent metal compound may be contained as it is in a solid form in the alkali-soluble film or the alkali-soluble coating agent of the present invention, but a part or all of the polyvalent metal compound is a polymer. It is preferably present in the form of a salt therein. When a so-called metal crosslink is formed by the interaction between the polyvalent metal compound and the carboxyl group of the polymer, a film excellent in mechanical strength and nonblocking property is obtained, which is preferable. It is more preferable that the metal crosslinks are formed uniformly with the carboxyl groups of the polymer, and the film will be more excellent in terms of mechanical strength and whitening.

It is preferable that the alkali-soluble film and the alkali-soluble coating agent of the present invention are insoluble in neutral or acidic water and soluble in alkaline water because they are selectively soluble in alkaline water. The alkali-soluble film and the alkali-soluble coating agent of the present invention contain the polymer and the polyvalent metal as essential components. The blending ratio of the polymer and the polyvalent metal is not limited as long as it is 0.05 parts by weight or more of the polyvalent metal with respect to 100 parts by weight of the polymer, but is preferably polyvalent with respect to 100 parts by weight of the polymer. The amount of metal is 0.05 to 10 parts by weight. When the polyvalent metal exceeds 10 parts by weight with respect to 100 parts by weight of the polymer, moldability may be deteriorated.

If necessary, the alkali-soluble film and the alkali-soluble coating agent of the present invention may be blended with other additives such as fillers and plasticizers. Specific examples of the filler include kaolin, asbestos, mica and the like. The blending amount of the filler is 100 parts by weight of the total amount of the polymer and the polyvalent metal,
It is preferably from 1 to 20 parts by weight.

Specific examples of the plasticizer include dioctyl phthalate and tributyl acetylcitrate. The compounding amount of the plasticizer is preferably 0.5 to 10 parts by weight based on 100 parts by weight of the total amount of the polymer and the polyvalent metal. The alkali-soluble coating agent of the present invention contains the polymer, the polyvalent metal, and a solvent. It is not always necessary to heat the mixture of the polymer, the polyvalent metal, and the solvent, but heating may be performed to promote metal crosslinking.

When the polymer and the polyvalent metal are mixed, a solvent is added if necessary. Specific examples of the added solvent include methanol, water, benzene, toluene, ethyl acetate and the like. Here, if the polyvalent metal is a salt of a polyvalent metal, the one that can dissolve the salt of the polyvalent metal is used as a solvent, and when the salt of the polyvalent metal is added in a state of being dissolved in the solvent, it is more It is preferable because the polyvalent metal can be introduced uniformly. Specific examples of the combination of the polyvalent metal salt and the solvent include magnesium acetate-methanol, calcium stearate-toluene and the like. The amount of the solvent used is preferably 10 to 400 parts by weight based on 100 parts by weight of the total amount of the polymer and the polyvalent metal. After mixing the polymer and the polyvalent metal, part or all of the solvent used, if necessary, is devolatilized under atmospheric pressure or reduced pressure using a tank reactor, a twin-screw extruder, or the like.
A solvent may be newly added to give the alkali-soluble coating agent of the present invention.

By applying the alkali-soluble coating agent of the present invention to the surface of various objects, an alkali-soluble film or film is formed on the surface. Specific examples of various objects include films, papers, sheets, metal plates,
Concrete examples can be given. In particular, it is preferable to use an alkali-soluble coating agent for films and papers because not only gloss and the like are imparted at the time of use but also paper and the like after use can be reused.

The alkali-soluble film of the present invention may be produced by using the above-mentioned alkali-soluble coating agent by a so-called casting method in which the solvent contained in the coating agent is evaporated at room temperature or under heating. A film may be produced by molding the alkali-soluble composition obtained by devolatilizing the solvent in the above alkali-soluble coating agent. Further, a film may be produced in the same manner as in the case where the unreacted monomers and the like are devolatilized from the polymer composition obtained by bulk polymerization, and then a polyvalent metal is added.

The alkali-soluble film of the present invention can be produced by using an alkali-soluble coating agent. In order to keep the mechanical strength of the obtained film constant, the film thickness is preferably uniform. A commonly used coating machine such as a roll coater, a reverse coater, a gravure coater, or a bar coater is used to keep the film thickness uniform. The alkali-soluble film can be produced by applying the alkali-soluble coating agent on the surface of paper, film or the like using the above coating machine and then evaporating the solvent contained in the coating agent. Here, if the surface of the paper, film or the like coated with the alkali-soluble coating agent has releasability,
The surface and the film can be separated, and a single alkali-soluble film can be obtained. Further, when the surface of paper, film or the like has no releasability and the surface and the film are in close contact with each other, a film in which an alkali-soluble film is laminated and a paper in which an alkali-soluble film is laminated can be obtained.

The alkali-soluble film of the present invention can be produced by molding an alkali-soluble composition. For example, the film can be produced by an extrusion molding method such as T-die molding, inflation molding, blow molding, laminate molding, or a calendering method, in which the composition is melt extruded by an extruder. If necessary, the obtained film may be further uniaxially or biaxially stretched.

The thickness of the alkali-soluble film of the present invention is not particularly limited, but is usually 10 to 200 μm, strength,
From the viewpoint of moldability, it is preferably 30 to 100 μm. Uses of Alkali-Soluble Film The alkali-soluble film of the present invention is printable and non-blocking, has high mechanical strength (tensile strength and tear strength, etc.), and has stable strength and dimensional characteristics against changes in temperature or humidity. It is used in various applications by taking advantage of its characteristics.

The label substrate of the present invention comprises the above alkali-soluble film. To use it as a label substrate,
It is necessary for the film to have a tensile strength sufficient to withstand the tension during printing. The film has a uniform thickness and is preferably 30 μm or more. As a method for producing the label base material, it is preferable to perform it by T-die extrusion molding, casting method or the like. The obtained label base material is used for bottles, paper labels and the like, and can be easily removed by alkali treatment after use, and has excellent water resistance.

The packaging bag of the present invention comprises the alkali-soluble film. In order to use it as a packaging bag, it must have excellent heat sealability, elongation, tensile strength and tear strength. As a method of manufacturing the packaging bag, the packaging bag is obtained by molding by various molding methods to obtain an alkali-soluble film and then heat sealing. As a molding method, inflation molding is the most simple and preferable.
The size of the packaging bag is not particularly limited and can be freely set depending on its use. The packaging bag thus obtained can be subjected to the next necessary steps without opening the bag and taking out the contents in the bag.
It is useful as an individual packaging bag for pesticides, detergents, and as a laundry bag.

The renewable processed paper of the present invention comprises the alkali-soluble film and paper laminated on the alkali-soluble film. There is no particular limitation on the paper constituting the recyclable processed paper, and for example, plain paper, high-quality paper, kraft paper, glassine paper and the like are used. The thickness of the alkali-soluble film is not particularly limited, but is 10 to 1
It is preferably 00 μm.

There is no particular limitation on the method for producing the recyclable processed paper, and it can be obtained by laminating an alkali-soluble film and paper by any method. For example, the above-mentioned alkali-soluble coating agent is roll coater or gravure coater. After coating or impregnating the paper with a coating machine such as, the solvent is evaporated, and the composition obtained by devolatilizing the alkali-soluble coating agent is T-die extruded and simultaneously laminated on the paper. There is a way to do it.

The recyclable processed paper of the present invention is non-blocking and has little deformation, and when it is stirred with alkaline water, for example, 1% sodium hydroxide aqueous solution, the laminated alkali-soluble film is easily removed and the paper is disintegrated. Therefore, it is reproducible. The renewable paper label of the present invention can be obtained by printing on the alkali-soluble film of the renewable processed paper. The printing method is not particularly limited, and any method can be used for printing. Examples of the printing ink used for printing include letterpress ink, planographic ink, gravure ink, flexo ink, screen ink, intaglio ink,
Examples thereof include thermal transfer ink and resist ink.

Similar to the recycled processed paper, the renewable paper label is also non-blocking and has little deformation, and the laminated alkali-soluble film can be easily removed by stirring with alkaline water, for example, 1% sodium hydroxide aqueous solution. , It can be recycled because the paper is disaggregated. The release paper of the present invention further comprises a release agent layer laminated on the alkali-soluble film of the renewable processed paper.

Examples of the release agent include silicone resin, fluororesin, acrylic resin and the like. As a method for laminating on recyclable processed paper, for example, there is a method in which a release agent is dispersed in an organic solvent such as toluene, coated, and dried. The thickness of the release agent layer is not particularly limited, but is preferably 0.5 to 5 μm, for example, since a release agent layer having sufficient release ability and fixability can be obtained by one coating.

The alkali-soluble film of the present invention can be laminated on a water-soluble resin film such as polyvinyl alcohol, polyethylene oxide or polydioxolane.
Similarly, an alkali-soluble film can be laminated on a hydrophobic resin film such as polyester or polyolefin. These laminated films can also be used for various purposes.

[0049]

The following examples are illustrative of the invention and are not intended to limit the scope of the claims of the invention. In the following Examples and Comparative Examples, "parts" and "%" represent "parts by weight" and "% by weight", respectively. -Example 1-In a tank reactor having a capacity of 100 liters, 4 kg of ethyl acrylate, 1.5 kg of acrylic acid, 4.5 kg of methyl methacrylate, 10 kg of methanol, 2,2-azobis (2,4-dimethylvaleronitrile). Charge 40g,
It heated at 60 degreeC and superposed | polymerized for 2 hours, and obtained the polymer solution (1). The number average molecular weight of the obtained polymer was 57,000, and the glass transition temperature was 40 ° C. A hot toluene solution of 450 g of calcium stearate was added to the polymer solution (1) and stirred at 30 ° C. for 30 minutes to obtain an alkali-soluble coating agent (1).

The obtained alkali-soluble coating agent (1) was devolatilized under reduced pressure heating using a twin-screw extruder, and the obtained composition was T-die molded at 220 ° C. to obtain a film. Using this film as a label substrate, mechanical strength and the like were measured by the following methods. Table 1 shows the results. Tensile strength and elongation Tested according to JIS K7127. The film used for the test has a thickness of 50 μm and the test speed is 100 mm /
min. Met. Tear strength Tested according to JIS K7128. The thickness of the film used in the test is 50 μm, and the test speed is 200 mm /
min. Met. The appearance at the time of measuring the whitened tensile strength was observed and evaluated. The evaluation criteria are as follows.

◯: No whitening occurred. B: Whitened immediately after fracture. X: Whitening occurred until the elongation reached 100%. The rate of dimensional change after leaving for 72 hours in an atmosphere of shrinkage of 30 ° C. and 80% RH was measured. Blocking property The coiled film was left at room temperature or at 50 ° C. to evaluate the degree of blocking. The evaluation criteria are as follows.

⊚: Rewinding was easy. ○: There was some resistance to rewinding. Δ: There were places where the film could not be rewound. X: Rewinding was not possible at all. Acid value Hiranuma Sangyo Co., Ltd. automatic titrator (COMTE-98
0) was used to determine a solution of 1 g of the film dissolved in 100 g of methanol by titration with a 0.1 N aqueous sodium hydroxide solution. When a film was attached as a label to an alkali peelable bottle and immersed in a 0.4% sodium hydroxide aqueous solution, the time required for dissolution and peeling was measured. 10 g of a soluble film in neutral and acidic water was immersed in ion-exchanged water and 0.1 N hydrochloric acid for 24 hours and then dried, and the weight loss rate was measured to determine the elution amount (%). Printed image Offset printing was performed with RI-1 type printing tester. The appearance (degree of deviation, wrinkles, and bleeding) was observed and evaluated.
The evaluation criteria are as follows.

⊚: Very good ∘: Good Δ: Slightly bad ×: Poor ink fixing property F-Gloss manufactured by Dainippon Ink and Chemicals, Inc.
Offset printing was performed with a RI-1 type printing tester, and 10 minutes after printing, fine papers were overlaid and pressed, and the density of the ink transferred to the fine papers was observed and evaluated. The evaluation criteria are as follows.

◯: No transfer occurred. Δ: Slightly transferred. X: Transferred in large quantities. -Comparative Example 1- The polymer solution (1) of Example 1 was directly used as a comparative alkali-soluble coating agent (1).

The obtained comparative alkali-soluble coating agent (1) was devolatilized under reduced pressure heating using a twin-screw extruder, and the obtained composition was T-die molded at 200 ° C. to obtain a film. . Using this film as a label substrate, mechanical strength and the like were measured in the same manner as in Example 1, and the results are shown in Table 1. -Comparative Example 2- 10 kg of water was obtained by polymerizing a monomer mixture having the same composition as in Example 1.
Was charged and emulsion polymerization was carried out. At the start of the polymerization, 150 g of sodium lauryl sulfate, 25 g of ammonium persulfate and 300 g of bromotrichloroethane were added. 36 g of magnesium hydroxide was added to the obtained comparative polymer dispersion liquid (2), and the mixture was stirred for 1 hour to obtain a comparative alkali-soluble coating agent (2).

The comparative alkali-soluble coating agent (2) obtained was cast into a film. Using this film as a label substrate, mechanical strength and the like were measured in the same manner as in Example 1, and the results are shown in Table 1. -Comparative Example 3-Ethyl acrylate 4.0k was prepared in the same manner as in Example 1.
g, acrylic acid 0.6 kg, methyl methacrylate 5.4
kg, methanol 10 kg, 2,2-azobis (2,4
-Dimethylvaleronitrile) (40 g) was charged and polymerized to obtain a comparative polymer solution (3). The number average molecular weight of the obtained polymer was 51,000, and the glass transition temperature was 38 ° C. A hot toluene solution of 450 g of calcium stearate was added to the comparative polymer solution (3) and stirred at 30 ° C. for 30 minutes to obtain a comparative alkali-soluble coating agent (3).

The obtained comparative alkali-soluble coating agent (3) was heated under reduced pressure using a twin-screw extruder to devolatilize, and the resulting composition was T-die molded at 200 ° C. to obtain a film. . Using this film as a label substrate, Example 1
The mechanical strength, etc. were measured by the same method as in Table 1, and the results are shown in Table 1.
Shown in -Comparative Example 4-Ethyl acrylate 4.0k was prepared in the same manner as in Example 1.
g, acrylic acid 4.5 kg, methyl methacrylate 1.5
kg, methanol 10 kg, 2,2-azobis (2,4
-Dimethylvaleronitrile) (40 g) was charged and polymerized to obtain a comparative polymer solution (4). The number average molecular weight of the obtained polymer was 63,000, and the glass transition temperature was 45 ° C. A hot toluene solution of 450 g of calcium stearate was added to the comparative polymer solution (4) and stirred at 30 ° C. for 30 minutes to obtain a comparative alkali-soluble coating agent (4).

The comparative alkali-soluble coating agent (4) obtained was heated under reduced pressure using a twin-screw extruder to devolatilize, and the resulting composition was T-die molded at 230 ° C. to obtain a film. . Using this film as a label substrate, Example 1
The mechanical strength, etc. were measured by the same method as in Table 1, and the results are shown in Table 1.
Shown in

[0059]

[Table 1]

From Table 1, since the label base material of Example 1 is excellent in mechanical strength and dimensional stability, image shifts and wrinkles do not occur during printing, and the ink fixability is good. There is no problem in processing the label. Further, the label base material is difficult to whiten because the resin structure is homogeneous,
There was little shrinkage, blocking did not occur, and it could be easily peeled off by the alkali treatment.

Example 2-Ethyl acrylate 6.5k was prepared in the same manner as in Example 1.
g, acrylic acid 1.5 kg, methyl methacrylate 2 k
g, methanol 10 kg, 2,2-azobis (2,4-
40 g of dimethyl valeronitrile) was charged and polymerized,
A polymer solution (2) was obtained. The number average molecular weight of the obtained polymer was 62,000, and the glass transition temperature was 30 ° C. A methanol solution of 150 g of magnesium acetate tetrahydrate was added to the polymer solution (2) and stirred at 30 ° C. for 30 minutes to obtain an alkali-soluble coating agent (2).

The alkali-soluble coating agent (2) thus obtained was heated under reduced pressure using a twin-screw extruder to devolatilize, and the resulting composition was inflation-molded at 200 ° C. to obtain a film. Using this film as a packaging bag, mechanical strength and the like were measured by the same method as in Example 1 and the following method, and the results are shown in Table 2. Solubility in Detergent Aqueous Solution A film was immersed in a detergent aqueous solution of 50 ° C. in which 5 g of a powder detergent (Attack, manufactured by Kao Corporation) was dissolved in 1 liter of tap water, and the time until the film was dissolved was measured. 20 heat-sealable films (size: 5 cm x 5 cm)
After heat-sealing with a heat sealer at 0 ° C. for 1 second, the force required for peeling was measured.

-Comparative Example 5-Using the film obtained in Comparative Example 2 as a packaging bag, Example 2
The mechanical strength was measured in the same manner as in Table 2, and the results are shown in Table 2.
Shown in -Comparative Example 6- The polymer solution (2) of Example 2 was directly used as a comparative alkali-soluble coating agent (6).

The obtained comparative alkali-soluble coating agent (6) was devolatilized under reduced pressure heating using a twin-screw extruder, and the composition obtained was inflation-molded at 200 ° C. to obtain a film. Using this film as a packaging bag, mechanical strength and the like were measured in the same manner as in Example 2, and the results are shown in Table 2. -Comparative Example 7-Polyvinyl alcohol having a polymerization degree of 1500 and a saponification degree of 90 mol% was synthesized, and a film was produced by a casting method. Using this film as a packaging bag, the mechanical strength was measured in the same manner as in Example 2, and the results are shown in Table 2.

[0065]

[Table 2]

From Table 2, the packaging bag of Example 2 has sufficient strength and heat-sealing property, has no whitening, and is suitable as a packaging bag. Further, it has non-blocking property and alkali solubility. -Example 3-Alkali-soluble coating agent (1) obtained in Example 1 was coated on a plain paper having a thickness of 50 µm using a bar coater and then dried, and an alkali-soluble coating having a thickness of 10 µm was applied on the plain paper. A processed paper on which a film layer was formed was obtained.

The physical properties of the obtained processed paper were measured by the following methods, and the results are shown in Table 3. Two pieces of blocking- processed paper (size: 5 cm × 5 cm) were stacked and left at room temperature to evaluate the degree of blocking. The evaluation criteria are as follows. ◯: Peeling is easy.

Δ: There is some resistance to peeling. X: Peeling is difficult. Curled paper (size: 5 cm x 5 cm) at 30 ° C, 80% R
It was left in a thermo-hygrostat of H for 5 hours and then dried, and its appearance was observed and evaluated. The disaggregated processed paper (size: 5 cm × 5 cm) was immersed in 1 liter of a 0.1% aqueous sodium hydroxide solution and stirred with a mixer, and then the presence or absence of undisaggregated substances was observed and evaluated.

Comparative Example 8 The comparative alkali-soluble coating agent (1) obtained in Comparative Example 1 was coated on plain paper in the same manner as in Example 4,
It was dried to obtain a processed paper. The physical properties of the obtained processed paper were measured in the same manner as in Example 3, and the results are shown in Table 3.

Example 4 A solution prepared by dispersing a silicone resin in toluene was applied to the alkali-soluble film layer of the processed paper obtained in Example 4 using a bar coater and then dried to a thickness of 1 μm. A release paper on which the release layer of No. 1 was formed was obtained. The physical properties of the obtained processed paper were measured in the same manner as in Example 3, and the results are shown in Table 3.

[0071]

[Table 3]

From Table 3, the processed paper obtained by using the alkali-soluble coating agent of Example 3 is excellent in the dimensional stability of the resin, is hard to curl, is non-blocking, and is resistant to alkali treatment. Easy disaggregation.

[0073]

The alkali-soluble film of the present invention is
Since it contains a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl-based monomer, and a polyvalent metal, it is printable and non-blocking. High mechanical strength (tensile strength and tear strength), and stable strength and dimensional characteristics against changes in temperature or humidity.

The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight of the vinyl-based monomer is an alkyl acrylate. When it is at least one selected from the group consisting of esters and alkyl methacrylates, a film having excellent flexibility, toughness, gloss and weather resistance can be obtained.

The acid value of the polymer is 70 to 300 mg KO.
H / g, number average molecular weight 10,000 to 500,000
0, having a glass transition temperature of -30 to 120 ° C, being insoluble in neutral or acidic water and soluble in alkaline water,
It is possible to obtain a flexible film that is selectively soluble in alkaline water, has a good balance between the solubility in alkaline water and water resistance, has good mechanical strength and moldability, and has good mechanical strength.

When the polyvalent metal is at least one metal selected from the group consisting of magnesium, calcium and zinc, the elongation property and water resistance of the film are improved, which is economically advantageous. Since the label base material of the present invention comprises the alkali-soluble film, it is printable and non-blocking, has high mechanical strength (tensile strength and tear strength, etc.), has excellent dimensional stability, and is easily removed by alkali treatment. It is possible and has excellent water resistance.

Since the packaging bag of the present invention is made of the above alkali-soluble film, it is non-blocking, has high mechanical strength (tensile strength, tear strength, etc.), and is easily dissolved in alkaline water. Since the regenerable processed paper of the present invention comprises the alkali-soluble film and the paper laminated on the alkali-soluble film, it has printability and non-blocking property and can be easily regenerated.

Since the reproducible paper label of the present invention is obtained by printing on the alkali-soluble film of the recyclable processed paper, it has a non-blocking property and can be easily regenerated. Since the release paper of the present invention further includes a release agent layer laminated on the recyclable processed paper, it has printability, nonblocking property, is easily reproducible, and has releasability.

The alkali-soluble coating agent of the present invention comprises a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl monomer, and a polyvalent metal. And a solvent, the film layer is printable and non-blocking, has high mechanical strength (tensile strength and tear strength, etc.), and has stable strength and dimensional characteristics against changes in temperature or humidity. can get.

The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight of the vinyl-based monomer is an alkyl acrylate. When it is at least one selected from the group consisting of esters and alkyl methacrylates, a film layer excellent in flexibility, toughness, gloss and weather resistance can be obtained.

The acid value of the polymer is 70 to 300 mg KO.
H / g, number average molecular weight of 5,000 to 500,000,
When it has a glass transition temperature of -30 to 120 ° C, is insoluble in neutral or acidic water, and is soluble in alkaline water, it is selectively soluble in alkaline water, and moreover, it has solubility in alkaline water and water resistance. A film layer that is well balanced, has good mechanical strength and moldability, and is flexible.

When the polyvalent metal is at least one metal selected from the group consisting of magnesium, calcium and zinc, the elongation property and water resistance of the film layer are improved,
It is economically advantageous.

Claims (13)

[Claims] 1. An alkali-soluble film containing a polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl monomer, and a polyvalent metal. . 2. The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight of the vinyl-based monomer is acrylic. The alkali-soluble film according to claim 1, which is at least one selected from the group consisting of acid alkyl esters and methacrylic acid alkyl esters. 3. The acid value of the polymer is 70 to 300 mg KO.
H / g, number average molecular weight 10,000 to 500,000
The alkali-soluble film according to claim 1 or 2, which has a glass transition temperature of −30 to 120 ° C., is insoluble in neutral or acidic water, and is soluble in alkaline water. 4. The alkali-soluble film according to claim 1, wherein the polyvalent metal is at least one metal selected from the group consisting of magnesium, calcium and zinc. 5. A label substrate comprising the alkali-soluble film according to any one of claims 1 to 4. 6. A packaging bag comprising the alkali-soluble film according to any one of claims 1 to 4. 7. A recyclable processed paper comprising the alkali-soluble film according to any one of claims 1 to 4, and a paper laminated on the alkali-soluble film. 8. A renewable paper label obtained by printing on the alkali-soluble film of the renewable processed paper according to claim 7. 9. A release paper further comprising a release agent layer laminated on the alkali-soluble film of the renewable processed paper according to claim 7. 10. A polymer obtained by non-aqueous polymerization of an α, β-unsaturated carboxylic acid monomer and at least one vinyl monomer, a polyvalent metal, and a solvent. Alkali-soluble coating agent. 11. The α, β-unsaturated carboxylic acid monomer is at least one selected from the group consisting of acrylic acid and methacrylic acid, and at least 30% by weight of the vinyl-based monomer is acrylic. The alkali-soluble coating agent according to claim 10, which is at least one selected from the group consisting of acid alkyl esters and methacrylic acid alkyl esters. 12. The acid value of the polymer is 70 to 300 mgK.
OH / g, number average molecular weight of 5,000 to 500,000
The alkali-soluble coating agent according to claim 10 or 11, which has a glass transition temperature of -30 to 120 ° C, is insoluble in neutral or acidic water, and is soluble in alkaline water. 13. The alkali-soluble coating agent according to claim 10, wherein the polyvalent metal is at least one metal selected from the group consisting of magnesium, calcium and zinc.