JPH10226987A - Easily disintegrable moistureproof paper board and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an easily disintegrable moistureproof paper board that has excellent moisture-and water-proofness, heat sealability, and disintegrability easing recoverable as waste paper, and improved foldability and sealability of ruling parts by coating a surface of the paper board with a specific emulsion mixture and drying the surface. SOLUTION: This easily disintegrable moistureproof paper board is produced by coating a surface of a paper board with an emulsion mixture obtained by mixing, as a solid content, 70-99wt.% of a copolymer emulsion which contains, as copolymer components, 25-35wt.% of aromatic vinyl monomers, 10-20wt.% of carboxyl group-containing acrylic monomers, 65-45wt.% of acrylic ester monomers and a small quantity of a silane coupling agent, and has a glass transition point of 25 deg.C or lower temperature, with 30-1wt.%, as a solid content, of a wax-based emulsion, and then drying the emulsion mixture on the paper board surface. The silane coupling agent is used preferably at a rate of 0.1-2 pts.wt. to 100 pts.wt. of the aromatic vinyl monomers, carboxylic group- containing acrylic monomers and acrylic ester monomers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-proof paperboard used for packaging, containers and the like, and more particularly to a coating and moisture-proof paperboard having excellent disintegration properties for facilitating recovery of used paper and excellent sealing properties of a folded-formed crease. It relates to paperboard.

[0002]

2. Description of the Related Art Tarpaulin paper and wax paper have been known as moisture-proof papers. Recently, high-molecular compounds such as polyethylene, polypropylene and vinyl chloride have been applied to papers or pasted on them to provide moisture-proof and waterproof. Those having properties are generally used. However, although they can sufficiently function as to moisture resistance, their disintegration properties are extremely poor when recovered as waste paper, resulting in waste paper, trimming debris and molding processing generated in the moisture-proof paper manufacturing process. It was not possible to collect the waste paper that sometimes occurred, and it was difficult to reuse the pulp. Therefore, a major problem remains from the viewpoint of resource saving and environmental problems.

[0003] In recent years, in order to improve the above-mentioned problems, a moisture-proof paper manufacturing technique using moisture-proof coating that can be reused as used paper has been proposed. For example, those using a wax emulsion (JP-B-63-39022, JP-B-63-sho-63)
JP-A-39023), a method of applying a mixture of butadiene-based latex and wax to obtain a moisture-proof paper (Japanese Patent Publication No. 55-22597), and a method of applying a wax to an acrylic emulsion and coating the mixture (Japanese Patent Publication No. Hei 6-1994). 200498
JP-A-7-133600) and a method of obtaining a moisture-proof paper having improved disintegration and heat-sealing properties by using a crosslinked acrylic emulsion in this system.
Japanese Patent Application Laid-Open No. H10-157, and a method of obtaining a moisture-proof paper having improved blocking resistance and slip resistance by further adding an inorganic pigment to an acrylic emulsion-wax emulsion mixture system in order to improve blocking resistance and slip resistance. 8-222609
6) has been proposed.

[0004] With such improvements, the disintegration property for facilitating the recovery of used paper from moisture-proof paper can be obtained, and the moisture-proof, water-proof, and blocking resistance have also been improved. Although it has reached a possible level, it is still not enough for applications requiring more stringent performance. Especially in paperboard, of course, moisture-proof and waterproof,
Abrasion resistance and blocking resistance, which are problems in the production process, are required. In processing into paper containers and paper boxes, etc., the ruled line is sealed in the process of forming a ruled line on the paper with a ruler and bending along the ruled line. Properties and heat sealing properties in the box making process are also required. In the prior art as described above, it cannot be said that these required performances are sufficiently satisfied.In particular, in the process of forming a ruled line with a ruler and folding along the ruled line portion, in the case of paperboard, the coating layer is Due to a large amount of change in elongation and shrinkage, a severe force is applied to the moisture-proof coating layer at the ruled line, which is liable to cause troubles such as breakage, cutting, or generation of pinholes (hereinafter, when bending along the ruled line, the coating layer The property of resisting troubles such as breakage, cutting, or generation of pinholes is called ruled line breakability.)

[0005]

In the field of paperboard,
It is difficult to satisfy all of the above-mentioned performances including disintegration and crease breakability, and it is extremely difficult to simultaneously satisfy such properties as disintegration, crease breakability and blocking resistance. Was. An object of the present invention is to provide a coated paperboard which is excellent in disintegration for facilitating moisture proofing, waterproofing, heat sealing properties, and recoverability of used paper, and excellent in sealing properties of a folded crease.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have obtained a paperboard obtained by applying a mixed emulsion composed of a specific copolymer emulsion and a wax-based emulsion on the paper surface. As a result, the present inventors have found that a more excellent disintegrating moisture-proof paperboard can be obtained, and have completed the present invention. That is, the present invention provides an aromatic vinyl monomer 2
5-35% by weight, carboxyl group-containing acrylic monomer 10-20% by weight, acrylic ester monomer 65-4
5% by weight and a small amount of a silane coupling agent as a copolymer component, 70 to 99 parts by weight as a solid content of a copolymer emulsion having a glass transition point of 25 ° C. or lower, and 30 to 1 part by weight of a wax emulsion as a solid content. An easily disintegrating moisture-proof board made by applying a mixed emulsion consisting of parts by weight on a paper surface, and a method for producing the same.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, a mixed emulsion composed of a copolymer emulsion and a wax-based emulsion is used.
5-35% by weight, carboxyl group-containing acrylic monomer 10-20% by weight, acrylic ester monomer 65-4
5% by weight and a small amount of a silane coupling agent are used as a copolymer component and have a glass transition point of 25 ° C. or lower.

As the aromatic vinyl monomer, for example, styrene, p-methylstyrene, o-methylstyrene, m
-Methylstyrene, α-methylstyrene and the like, among which styrene is preferably used. The proportion of the aromatic vinyl monomer in the copolymer component is 25 to 35.
% By weight, preferably from 27 to 32% by weight.
% By weight. When the proportion of the aromatic vinyl monomer in the copolymer component is less than 25% by weight, the blocking resistance of the paperboard becomes poor. On the other hand, when the proportion exceeds 35% by weight, the ruled line break cracking is deteriorated. It is not preferable.

Acrylic acid, methacrylic acid and the like are used as the carboxyl group-containing acrylic monomer. The proportion of the carboxyl group-containing acrylic monomer in the copolymer component needs to be 10 to 20% by weight, and preferably 12 to 17% by weight. In order to obtain good disintegration to facilitate recovery of waste paper, the coating film is crushed by shearing force in water, and it is necessary to separate pulp fiber and coating resin by water and the shearing force. . Since the carboxyl group-containing acrylic monomer has a carboxyl group that is a hydrophilic group, it is hydrophilic, and also contains a carboxyl group that is a hard segment, so that the carboxyl group-containing acrylic monomer accounts for in the copolymerization component. Is less than 10% by weight, crushing of the coating film by underwater shearing force and separation of the pulp fiber from the coating resin become insufficient. On the other hand, when it exceeds 20% by weight, the separation is easy, Conversely, it is not preferable because it has high hydrophilicity, becomes hard and brittle, and deteriorates the moisture permeability and crease breakability of the paperboard.

Further, as the acrylic ester monomer, for example, methyl acrylate, methyl methacrylate,
Ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, heptyl acrylate, heptyl methacrylate, acrylic acid Octyl, 2-ethylhexyl acrylate, dodecyl acrylate, dodecyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, and the like are preferable. Among them, 2-ethylhexyl acrylate is preferably used. These acrylic ester monomers may be used alone or in combination of two or more. The proportion of the acrylic ester monomer in the copolymer component needs to be 45 to 65% by weight, preferably 50 to 65% by weight. When the proportion of the acrylic ester monomer in the copolymer component is less than 45% by weight, the resin becomes hard, and the ruled line breakage and heat sealability of the paperboard become poor,
On the other hand, when the content exceeds 65% by weight, it is difficult to separate the pulp fiber and the coating resin, and the blocking resistance of the paperboard becomes poor.

As the resin component of the coating liquid for the moisture-proof paperboard for easy disintegration molding, a copolymer of only the above-mentioned aromatic vinyl monomer, carboxyl group-containing acrylic monomer and acrylic ester monomer is used. In addition, the mixing ratio is not sufficient, and it is necessary to contain a small amount of a silane coupling agent in order to improve the blocking resistance while maintaining the sealing property of the bent crease.

The silane coupling agent is not particularly limited as long as it is a silane coupling agent having a polymerizable α, β-ethylenically unsaturated double bond. Examples thereof include vinyltrichlorosilane, vinyltrimethoxysilane, and vinyltrimethoxysilane. Ethoxysilane, tris-2-methoxyethoxyvinylsilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and the like, among which a silane coupling agent having a (meth) acryl group is preferable. Used effectively.

The content of the silane coupling agent is preferably 0.1 to 2 parts by weight per 100 parts by weight of the aromatic vinyl monomer, the carboxyl group-containing acrylic monomer and the acrylic ester monomer. It is preferably used in a proportion of parts by weight, more preferably in a proportion of 0.3 to 1.5 parts by weight. If the amount is less than 0.1 part by weight, it is difficult to improve the blocking resistance of the paperboard. If the amount exceeds 2 parts by weight, the sealing property of the folded line portion cannot be maintained, and the heat sealing property tends to be poor.

In order to crosslink the obtained resin, a crosslinking agent other than the silane coupling agent, for example, divinylbenzene, diallyl phthalate, allyl methacrylate, ethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, etc. There are also crosslinkers having two α, β-ethylenically unsaturated double bonds, but crosslinking with these makes the resin too hard and can improve the disintegration and blocking resistance, but loses flexibility. Since the sealing property and the heat sealing property of the bent-formed crease portion cannot be maintained, it is not preferable to use them.

In the present invention, the copolymer obtained from the above copolymer component must have a glass transition point of 25 ° C. or lower. When the copolymer has a glass transition temperature of more than 25 ° C., the film forming property of the coating film formed at the time of coating and drying is deteriorated, and the sealing property and the heat sealing property of the crimped crease portion are poor. Because. Using the above-mentioned aromatic vinyl monomer, carboxyl group-containing acrylic monomer, acrylic ester monomer and silane coupling agent as copolymerization components, a copolymer emulsion can be obtained as follows.

That is, an emulsifier is mixed with deoxygenated deionized water, the above-mentioned monomers are mixed with stirring, the polymerization temperature is adjusted, and water containing a polymerization initiator is added.
What is necessary is just to polymerize. In the polymerization, a pH adjuster such as an acid and a salt thereof, aqueous ammonia and an alkali metal hydroxide may be used.

As the emulsifier, a nonionic surfactant or an anionic surfactant is used. Examples of the nonionic surfactant include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene octyl phenol ether, and polyoxyethylene nonyl phenol ether; polyoxyethylene alkyl phenol ether, polyoxyethylene sorbitan monolaurate and the like. Polyoxyethylene sorbitan fatty acid esters and the like, and as the anionic surfactant, for example, sodium lauryl sulfate,
Sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenol ether sulfate and the like can be mentioned.

The polymerization initiator is not particularly limited as long as it is a water-soluble radical initiator used in ordinary emulsion polymerization. For example, hydrogen peroxide, potassium persulfate, sodium persulfate, ammonium persulfate and the like can be used alone. Or a redox system in which it is combined with a reducing agent such as ferrous sulfate or Rongalite. The polymerization method is
Batch type or continuous type may be used, and the polymerization temperature is
About 40 to 80 ° C. is appropriate.

In the present invention, a mixed emulsion consisting of the above-mentioned copolymer emulsion and wax emulsion is used.
Known wax emulsions such as a paraffin wax emulsion, a polyethylene wax emulsion, and a microcrystalline wax can be used. Paraffinic wax emulsions have high water repellency and are highly effective when used in small proportions. The melting point is not particularly limited, but a melting point of 40 to 100 ° C. is preferably used depending on the drying temperature during the coating process and the conditions used.

The mixing ratio of the copolymer emulsion and the wax-based emulsion in the mixed emulsion according to the present invention is such that the solid content of the copolymer emulsion is 70-99.
It is necessary to be 30 parts by weight of the wax emulsion and 30 to 1 part by weight of the wax emulsion, and it is preferable to be 80 to 98 parts by weight of the copolymer emulsion and 20 to 2 parts by weight of the wax emulsion. If the compounding ratio of the wax-based emulsion is less than 1 part by weight, good water repellency, moisture resistance and blocking resistance cannot be obtained, while if it exceeds 30%, the resin layer becomes brittle and a ruled line is formed by a ruler. Breakage or pinholes are likely to occur during processing. Especially for paperboard,
This is because it hinders the use requiring bending, and the slip resistance deteriorates.

The mixed emulsion in the present invention is obtained by stirring and mixing the copolymer emulsion and the above-mentioned wax emulsion in a mixing tank equipped with a stirrer.

The moisture-proof paperboard of the present invention is obtained by coating the above-mentioned mixed emulsion on the paper surface. The base paper used may be either acidic paper or neutral paper, and depending on the surface size, starch, polyvinyl alcohol or the like may be applied. In addition, a pigment may be applied for the purpose of improving paper properties such as strength physical properties, smoothness, and light-shielding properties of the paper. Further, a small amount of a known water repellent, anti-slip agent, or a starch, polyvinyl alcohol, or the like containing them for the purpose of imparting performance such as water repellency, smoothness, and curling is applied to the surface of the base paper opposite to the coated surface. The coating solution may be applied, or a small amount of the above-mentioned coating solution in the present invention may be applied.

On the surface of the above-mentioned paper, the mixed emulsion is diluted and coated with water as required. As a coating method, a general method such as a bar coater, an air knife coater, a blade coater, and a curtain coater is employed. The coating amount is preferably 3 to 30 g / m ² as a solid content, and more preferably 5 to ²⁰ g / m ² . If the coating amount is less than 3 g / m ² , the moisture proof property, heat sealing property, and the quality of breakage of the ruled line are inferior. If the coating amount is more than 30 g / m ² , the burden on the drying capacity increases, and the chemical cost increases. It tends to be expensive.

After the mixed emulsion is applied on the paper surface, it is dried. The drying temperature at that time must be higher than the melting point of the wax emulsion used. Even if the drying temperature is lower than the melting point of the wax-based emulsion, drying can be carried out over a long period of time, but in this case, not only the moisture-proof and waterproof properties are reduced, but also the film properties of the coating layer become brittle, so that the creases are broken. The properties also deteriorate, which is not preferred. Therefore, the drying temperature of the present invention may be at least the melting point of the wax-based emulsion, but it is also important to remove the water content of the mixed emulsion. Therefore, the drying temperature is preferably 100 to 150 ° C. in consideration of the drying time.

The moisture-proof paperboard of the present invention obtained in this manner has excellent properties such as moisture-proof, waterproof, heat-sealing properties and breakage of creases. Is easily separated from the pulp fiber by its shearing force and crushed. The moisture-proof paperboard of the present invention can be disintegrated with a Tappi standard disintegrator in 15 minutes equivalent to ordinary uncoated paper,
Moisture proof paperboard with excellent waste paper recovery compared to polyethylene laminated paper, polypropylene film bonded products, etc.

Further, by changing the composition of the copolymer emulsion, or by adjusting the ratio of the copolymer emulsion to the wax-based emulsion and the amount of coating, the moisture-proof and waterproof properties can be improved.
It is also possible to adjust properties such as friction resistance, blocking resistance, crease breakage of ruled lines, and heat sealability.

[0027]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto. In the examples and comparative examples described below, “%” indicates “% by weight”. The glass transition point (Tg) of the polymer in the emulsion was determined using a differential scanning calorimeter at a heating rate of 10 ° C / min in the range of -100 to 100 ° C.

The measurement of each characteristic was performed as follows. a. The moisture permeability was measured in accordance with JIS Z0208, a moisture permeability test of a moisture-proof packaging material (constant temperature / humidity condition: 40 ° C., 90% RH).

B. Using a ruler testing machine (manufactured by Sagawa Seisakusho), make a ruled line on the test piece, bend it along the ruled line, make a box of 5 cm long × 5 cm wide × 3 cm high, put 30 ml of distilled water in it,
After standing for 24 hours, the state of seepage of water was examined and evaluated on a 4-point scale. ◎: Does not exude ○: Almost does not exude Δ: Partly exudes ×: Exudes

C. Water disintegration (recovery of recovered paper) Standard disintegrator (Tappi standard disintegrator used in JIS P8209 pulp test handsheet preparation method):
3,000 rpm) and tap water at room temperature for about 2.5 c
The test piece of m-square is added to the pulp concentration of 4%, and the amount is 15
Disintegrated for minutes. The evaluation was carried out by visually observing the disintegration state after disintegration for 15 minutes and visually observing handsheets prepared using the disintegration as a raw material, and evaluated on a 4-point scale. ◎: Completely disintegrated ○: Almost disintegrated Δ: Partially disintegrated ×: Not disintegrated

D. Heat sealability After thermocompression bonding under the condition of 170 ° C. × 2 kg / cm ² × 2 seconds using a heat seal tester manufactured by Tester Sangyo Co., Ltd., the coating film was visually evaluated for heat sealability in three steps. ：: Heat sealable ○: Heat sealable but weak strength ×: No heat sealable

E. Blocking resistance The test piece was placed on top of the coated surface so that the coated surface or the coated surface or the coated surface and the uncoated surface were in contact with each other, left at a temperature of 50 ° C., a humidity of 75%, a pressure of 500 g / cm ² for 24 hours, and then manually. The film was peeled off and visually evaluated on a 5-point scale. ◎: No resistance at peeling ○: Slight noise at peeling, but no resistance Δ: Slight resistance at peeling ×: Resistance at peeling, slight peeling at the surface XX: Strong resistance at peeling, interlayer peeling

F. Ruled line breakability The test piece is cut into 15 cm squares, and ruled lines (ruled line width: 0.9 mm) are formed using a ruled line testing machine in the vertical and horizontal directions under the condition of ² kg / cm ² × 1 second so that the coated surface becomes convex. Ruled line depth 0.5
mm), make a single reciprocating fold along the ruled line, fix the habit, apply a methylene blue / ethanol solution to the coated surface, and apply a pinhole,
The presence or absence of cracks was observed visually and using a magnifying glass, and evaluated on a 5-point scale. ：: No cracks in pinholes ○: One or two minute pinholes can be confirmed by using ぺ ぺ: One or two minute pinholes can be visually confirmed ×: Three or more minute pinholes ××: Ruled line With cracks along

Synthesis Example 1 (Copolymer resin emulsion A1) Using a glass polymerization apparatus equipped with a heating device, stirrer, condenser, thermometer, and nitrogen gas inlet, styrene 300
g, 150 g of methacrylic acid, 550 g of 2-ethylhexyl acrylate, 7 g of γ-methacryloxypropyltrimethoxysilane, and 750 ml of deoxygenated / deionized water containing 16 g of sodium lauryl sulfate as an emulsifier, and mixed by stirring to obtain an emulsion. Was. 75 ° C
And 2.2 g of ammonium persulfate as a polymerization catalyst
Was uniformly added for 4 hours, and the mixture was further reacted for 2 hours to complete the polymerization. Solids concentration 5
A 2% aqueous emulsion was obtained, to which deionized water was added to a solids concentration of 45%.

Synthesis Examples 2 to 11 Copolymer resin emulsions having a solid content of 45% for each composition were prepared by changing the type and amount of the comonomer and adjusting the concentration in the same manner as in Synthesis Example 1. (A2 to B6) were obtained.

[0036]

[Table 1]

Example 1 Emulsion A1 obtained in Synthesis Example 1 and a paraffin-based special wax emulsified emulsion Haricoat C-300 (trade name, manufactured by Harima Chemicals, Inc.) were used in a solid content ratio of 100: 1.
The mixture was mixed so as to have a solid content of 40%. A double-coated paperboard having a basis weight of 310 g / m ² (manufactured by Tokyo Paper Co., Ltd., trade name: Snow Ace) is coated with a Meyer bar, dried at 130 ° C. for 30 seconds, and coated at a coating weight of 11.2 g / m ² . Obtained paperboard. As shown in Table 2, the obtained coated paperboard had very good moisture-proof properties, waterproof properties, defibration properties, heat-sealing properties, blocking resistance, and crease breakability.

Examples 2 to 7 and Comparative Examples 1 to 8 Using the copolymer emulsions shown in Tables 2 and 3 and the same wax emulsion as in Example 1, each coated paperboard was prepared in the same manner as in Example 1. did. The properties of the obtained coated paperboard were measured in the same manner as in Example 1.

[0039]

[Table 2]

[0040]

[Table 3]

[0041]

Industrial Applicability According to the present invention, it has excellent disintegration properties to facilitate the recovery of waste paper, and is suitable for creasing and heat sealing, which is not only moisture-proof, waterproof and blocking-resistant, but also strict performance as coated moisture-proof paperboard. It is possible to provide a moisture-proof paperboard that simultaneously satisfies the performances of the various colors.

──────────────────────────────────────────────────の Continued on front page (51) Int.Cl. ⁶ Identification code FI // (C08L 33/08 91:06)

Claims (4)

[Claims] 1. 25 to 35% by weight of an aromatic vinyl monomer,
A copolymer having 10 to 20% by weight of a carboxyl group-containing acrylic monomer, 65 to 45% by weight of an acrylic ester monomer and a small amount of a silane coupling agent and having a glass transition point of 25 ° C. or lower. An easily disintegrating moisture-proof paperboard obtained by applying a mixed emulsion comprising 70 to 99 parts by weight of an emulsion as a solid and 30 to 1 part by weight of a wax-based emulsion as a solid on a paper surface. 2. An aromatic vinyl monomer, a carboxyl group-containing acrylic monomer and an acrylic ester monomer 1.
2. The easily disintegrating moisture-proof paperboard according to claim 1, wherein the paperboard is used in a ratio of 0.1 to 2 parts by weight with respect to 00 parts by weight. 3. 25 to 35% by weight of an aromatic vinyl monomer,
A copolymer having 10 to 20% by weight of a carboxyl group-containing acrylic monomer, 65 to 45% by weight of an acrylic ester monomer and a small amount of a silane coupling agent and having a glass transition point of 25 ° C. or lower. A mixed emulsion obtained by mixing 70 to 99 parts by weight of the emulsion as a solid content and 30 to 1 part by weight of a wax-based emulsion as a solid content is applied on a paper surface, and then heated to a temperature higher than the melting point of the wax-based emulsion. A method for producing an easily disintegrating moisture-proof paperboard characterized by drying. 4. An aromatic vinyl monomer, a carboxyl group-containing acrylic monomer and an acrylic ester monomer 1.
The method for producing an easily disintegrating moisture-proof paperboard according to claim 3, wherein the silane coupling agent is used in an amount of 0.1 to 2 parts by weight with respect to 00 parts by weight.