JP3240223B2 - Moisture proof, easy disintegration coating agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moisture-proof and easily disintegrating coating agent for paper.
The present invention relates to a coating agent which is useful for producing waterproof paper, and is particularly suitable for producing wrapping paper such as newspaper base paper and copy paper.

[0002]

2. Description of the Related Art Conventionally, packaging papers include coated paper coated with wax, a general-purpose resin emulsion or vinylidene chloride resin, and laminated paper laminated with a thermoplastic film such as polyethylene. In recent years, a large amount of waste paper has been recovered and recycled due to the shortage of pulp raw materials.However, processed paper using the above-mentioned resin is increasing, and even if this is processed for waste paper recovery, the resin component is sufficiently disintegrated. And the undisintegrated fibers and resin fragments are mixed in the collected stock, which causes deterioration of paper formation, pitch trouble, and the like.

[0003] When wax is used to impart moisture-proofing properties to paper, not only is it necessary to apply a certain amount of coating, but also whitening occurs during folding, and the surface slips so badly that it is transported after winding. There is a problem in that the paper tube is displaced in the inside, so that the application of an anti-slip agent is inevitable. Also,
General-purpose resin emulsions have a problem in terms of moisture-proof performance, and paper coated with vinylidene chloride also exhibits excellent moisture-proof performance, but is often difficult to disaggregate during recycling of waste paper. Recently, coating agents combining wax emulsions and various types of emulsions have been developed. The required moisture proofing, waterproofing, easy disintegration for waste paper collection, bending whitening prevention,
There is no one yet having all of the anti-slip properties, anti-blocking properties and heat sealing properties, and this development has been desired.

[0004]

Under the circumstances described above, the present invention has excellent moisture proof and waterproof properties, easily disintegrates when collecting waste paper, and prevents the occurrence of troubles such as whitening, slippage and blocking during use. The present invention has been made to provide a coating agent capable of providing a coating having heat sealing properties.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a styrene-containing emulsion containing a specific range of a hydrophobic monomer as a main component and a specific range of a hydrophilic monomer It has been found that there is a possibility of solving the problem by a coating agent containing a (meth) acrylate-based emulsion composed of a body composition, a petroleum wax emulsion, and a carboxyl group-containing polyethylene-based wax emulsion. A test was conducted for the type and amount of the wax emulsion to arrive at the present invention.

That is, the present invention relates to (a) styrene and other hydrophobic monomers having a solubility in water at 25 ° C. of less than 1 g / water of less than 100 g / 100 g in a total solid content of 100 parts by weight. A styrene-containing emulsion obtained by copolymerization with a weight% of a main monomer composition is 40 to 90 parts by weight in terms of solid content, and (b) (meth) acrylate and other solubility in water at 25 ° C. Is 1 g / water 100
g to 90% to 97% by weight, and 3 to 10% by weight of α, β ethylenically unsaturated carboxylic acid
(Meth) acrylic acid ester-based emulsion obtained by copolymerizing is 5 to 50 parts by weight in terms of solids, and (c) an emulsion of petroleum wax having a melting point of 40 to 100 ° C is 2 to 15 parts by weight in terms of solids. And (d) an emulsion of a polyethylene wax having a carboxyl group and having an acid value of 30 to 200, the solid content of which is 0 to 15 parts by weight, and a moisture-proof, easily disintegrating coating agent for paper comprising an aqueous emulsion blended with each. It is an abstract.

Hereinafter, the present invention will be described in detail. The dried film made from the styrene-containing emulsion which is the component (a) of the coating agent of the present invention is of course dense and free from pinholes and cracks. However, it is an essential condition that the film has low moisture permeability. For this purpose, in addition to styrene as a monomer for producing an emulsion, a hydrophobic monomer having a solubility in water at 25 ° C. of less than 1 g / water of less than 100 g is used as a main component.

[0008] Such hydrophobic monomers other than styrene include α-methylstyrene, vinyltoluene, chlorostyrene, chloromethylstyrene, butadiene, isoprene, and acryl with an alcohol having an alkyl group having 3 to 18 carbon atoms. Examples thereof include acid esters, methacrylic acid esters with an alcohol having an alkyl group having 2 to 18 carbon atoms, vinyl chloride, and vinylidene chloride. Styrene with excellent moisture resistance is an essential component. However, if it is used in an amount exceeding 65% by weight of the total amount of the monomer, the coating film becomes hard, the texture is impaired, and bending whitening occurs. It is preferable to use only one kind or a combination of two or more kinds from among the hydrophilic monomers. In order to achieve the object of the present invention, the total amount of styrene and other hydrophobic monomers should be 80 to 97% by weight of the total amount of the monomers, but preferably is 9%.
0 to 97% by weight.

The styrene-containing copolymer in this emulsion includes a carboxyl group-containing monomer such as (meth) acrylic acid and maleic acid, 2-hydroxyethyl (meth) acrylate, and (meth) acrylic acid. Hydroxyl-containing monomers such as -2-hydroxypropyl, (meth) acrylamide, amide-containing monomers such as (meth) acrylic acid-N-methylolamide, dimethylaminoethyl (meth) acrylate, Amino group-containing monomers such as diethylaminoethyl (meth) acrylate, acrylonitrile, vinyl acetate, vinyl propionate, methyl (meth) acrylate,
Emulsion mechanical stability, coatability, etc. of monomers such as ethyl acrylate, methoxyethyl (meth) acrylate, and butoxyethyl (meth) acrylate having a solubility in water at 25 ° C of more than 1 g / 100 g of water. It is preferable to copolymerize in an amount of 3 to 20% by weight based on the total amount of the monomers in order to improve the content. If the amount of these monomers is too small, the mechanical stability and coatability tend to be poor, while if the amount is too large, the moisture permeability of the dried film tends to increase. More preferably, 3 to 10% by weight is copolymerized.

The styrene-containing emulsion (a) can be produced by a known emulsion polymerization method using each of the above-mentioned monomers. That is, the monomers to be used are mixed, and an emulsifier, a polymerization initiator and the like may be added thereto, and the emulsion polymerization may be performed in an aqueous system, such as a method of batch polymerization and a method of performing polymerization while continuously supplying each component. Various methods can be applied.

Examples of the emulsifier for emulsion polymerization include anionic emulsifiers such as alkyl or alkyl allyl sulfate, alkyl or alkyl allyl sulfonate, and dialkyl sulfosuccinate; cationic emulsifiers such as alkyltrimethylammonium chloride and alkylbenzylammonium chloride; Examples thereof include nonionic emulsifiers such as polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, and polyoxyethylene carboxylate, and polymerizable emulsifiers. The amount of the emulsifier used may vary depending on the properties required for the emulsion, but in general, the amount of the emulsifier used is increased for the purpose of improving polymerization stability or improving the mechanical and chemical stability of the emulsion. On the contrary, in order to improve the water resistance of the dried film, it is desirable that the amount used is small, and usually 1 to 1 based on 100 parts by weight of the total amount of the monomer.
The amount used is determined from the range of about 0 parts by weight depending on the purpose.

Examples of the polymerization initiator include water-soluble types such as persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide, azobisamidinopropane hydrochloride, benzoyl peroxide, cumene hydrochloride. Examples thereof include oil-soluble types such as peroxide, dibutyl peroxide, diisopropyl peroxycarbonate, cumyl peroxy neodecanoate, cumyl peroxy octoate, and azobisisobutyronitrile. Further, if necessary, a redox system using a reducing agent such as sodium acid sulfite, Rongalit, L-ascorbic acid, saccharide, amine or the like can also be used. The amount used may be about 0.01 to 3 parts by weight based on 100 parts by weight of the total amount of the monomers. The polymerization reaction may be carried out usually at about 35 to 90 ° C., and the reaction time may be usually about 3 to 10 hours.

At the start or at the end of the emulsion polymerization, a basic substance is added to adjust the pH to improve the polymerization stability, freezing stability, mechanical stability, chemical stability, etc. of the emulsion. Can be. In this case, it is preferable to adjust the pH of the obtained emulsion to 5 or more. Examples of the basic substance include ammonia, ethylamine, diethylamine, triethylamine, ethanolamine, triethanolamine, diethylethanolamine, caustic soda, and caustic potash. Can be used.

[0014] The dried film from the (meth) acrylic ester emulsion which is the component (ii) needs to have good water and alkali disintegration properties. Α, β with a hydrophilic monomer having a solubility in water of 1 g / 100 g or more at 25 ° C.
Ethylenically unsaturated carboxylic acids are used. Examples of such a hydrophilic monomer include, in addition to methyl (meth) acrylate and ethyl acrylate, (meth) acrylic acid-2-
Hydroxyl group-containing monomers such as hydroxyethyl and (meth) acrylic acid-2-hydroxypropyl; amide group-containing monomers such as (meth) acrylamide and (meth) acrylic acid-N-methylolamide; ) Amino group-containing monomers such as dimethylaminoethyl acrylate and diethylaminoethyl (meth) acrylate, acrylonitrile, vinyl acetate, vinyl propionate, methoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate and the like. These can be used alone or in combination of two or more. In order to achieve the object of the present invention, the total amount of the monomers is 90 to 90% of the total amount of the monomers.
The content is 97% by weight, preferably 93 to 96% by weight.

Another essential monomer component, α,
β-ethylenically unsaturated carboxylic acid is necessary for imparting water and alkali disintegration to the film, for example, acrylic acid,
Methacrylic acid, crotonic acid, itaconic acid, maleic acid,
Examples thereof include fumaric acid, maleic anhydride, and monoalkyl maleate. One of these may be used alone, or two or more thereof may be used simultaneously.
α, β ethylenically unsaturated carboxylic acids reduce the disintegration of water and alkali when the amount used is small, and conversely, when the amount used is large, the water vapor permeability and water resistance become poor.
-10% by weight, preferably 4-7% by weight.

In order to obtain the (meth) acrylate emulsion of the component (b), an emulsifier and a polymerization initiator selected from the same kind and amount as in the emulsion polymerization method of the styrene-containing emulsion of the component (a) are added. Emulsion polymerization.
At the start or after the end of the polymerization, add a basic substance to adjust the pH.
Adjusting is the same.

The main component of the coating agent of the present invention (A)
The component and the component (b) have greatly different monomer compositions and functions, respectively, and by using both of them, it is possible to have the reciprocal performance of moisture proofing, waterproofing and disintegration. For that purpose, the solid content derived from the component (a) in the total solid content of 100 parts by weight of the coating agent is 40 to 90 parts by weight, and the solid content derived from the component (b) is 5 to 50 parts by weight. But,
With only one copolymer having a weighted average composition ratio of the components (a) and (b), moisture proofing, waterproofing and disintegration cannot be simultaneously satisfied to a high degree. The reason is unknown,
The film formed by the combined use of the components (a) and (b) is non-uniform microscopically, and it is supposed that the film is easily disintegrated by the shearing force in the presence of water and alkali in the disintegration step.

The emulsion of the petroleum wax (c) is blended for imparting moisture-proof and water-proof properties to the film. A petroleum wax having a melting point in the range of 40 to 100.degree. Is an aqueous dispersion dispersed in If the melting point of the petroleum wax is higher than 100 ° C., the general condition for drying the processing composition applied on the paper surface is 130 ° C. × several tens of seconds. When the temperature is lower than 40 ° C., the petroleum wax penetrates into the fibers of the paper under the above-mentioned drying conditions, so that a sufficient moisture-proof property cannot be obtained. Thus, an emulsion of petroleum wax with a melting point range of 40-100 ° C is used,
A preferred melting point range is 40-65 ° C.

Examples of the petroleum wax include paraffin wax, microcrystalline wax, petrolatum, paraffin wax to which a zirconium compound is added, and paraffin wax is preferred. (C) If the compounding amount of the component is too small, sufficient moisture-proof and water-proof properties cannot be obtained, and if too large, an extreme whitening phenomenon appears at the time of bending or the disintegration is significantly impaired. The solid content from the petroleum wax emulsion in 100 parts by weight is 2 to 15 parts by weight, preferably 2 to 10 parts by weight.

The emulsion of the polyethylene wax as the component (d) is blended to improve the disintegration property and the slip resistance in addition to the moisture-proof and waterproof properties of the film. This polyethylene wax has a carboxyl group and has an acid value of 30 to 200, and preferably has a molecular weight in the range of 2,000 to 20,000. (D) Component is (a),
(B) and (C) are added when sufficient disintegration cannot be obtained while maintaining the moisture resistance of the coating film by adding only the components. If the amount is too large, sufficient moisture resistance and slip resistance can be obtained. Therefore, the solid content from the polyethylene wax emulsion in 100 parts by weight of the total solid content of the coating agent is 1%.
It is 5 parts by weight or less, preferably 10 parts by weight or less.

In the moisture-proof and easily disintegrating coating agent of the present invention, in addition to the above essential components, commonly used pigments, plasticizers, film-forming auxiliary agents, defoamers, viscosity modifiers, etc. do not impair the effects of the present invention. It can be arbitrarily compounded within the range.

[0022]

EXAMPLES Examples of the synthesis of styrene-containing emulsions, examples of the synthesis of (meth) acrylate-based emulsions, and specific examples and comparative examples using these emulsions will be described below. However, the present invention is not limited to this embodiment. In addition, the part and% in an example show a weight part and weight%, respectively.

Synthesis Example 1 (Synthesis of Emulsion A-1) A polymerization vessel equipped with a stirrer, condenser, thermometer and nitrogen gas inlet was charged with 275 parts of deionized water and purged with nitrogen. The temperature rose. Meanwhile, 138 parts of deionized water, 330 parts of styrene, acrylic acid-2-
176 parts of ethylhexyl, 11 parts of hydroxyethyl methacrylate, 16.5 parts of methacrylic acid, 16 parts of acrylic acid.
5 parts, 3.8 parts of sodium lauryl sulfate and 12.3 parts of polyoxyethylene nonyl phenyl ether were mixed and emulsified with a homogenizer, and 42 parts of a 3.8% aqueous solution of ammonium persulfate were separately placed in the polymerization vessel. The mixture was dropped uniformly over a long period of time, and further reacted at 82 ° C. for 2.5 hours to complete the polymerization. The obtained copolymer emulsion (hereinafter abbreviated as A-1) had a solid content concentration of 55%.
Table 1 shows the monomer composition (%).

Synthesis Examples 2 to 5 (Emulsions A-2 to A-
Synthesis of 5) In the same manner as in Synthesis Example 1, copolymerization was carried out in an amount based on the type and composition% of the monomers shown in Table 1, and the solid content concentration was 54 to 55.
% Copolymerized emulsions (A-2 to A-5) were obtained.

[0025]

[Table 1]

Synthesis Example 6 (Synthesis of Emulsion B-1) A polymerization vessel equipped with a stirrer, a condenser, a thermometer and a nitrogen gas inlet was charged with 275 parts of deionized water and purged with nitrogen. The temperature rose. On the other hand, 138 parts of deionized water, 308 parts of methyl methacrylate, 198 parts of ethyl acrylate, 11 parts of hydroxyethyl methacrylate, 22 parts of methacrylic acid, 11 parts of acrylic acid, 3.8 parts of sodium lauryl sulfate, 3.8 parts of polyoxyethylene nonyl A liquid obtained by mixing and emulsifying 12.3 parts of phenyl ether with a homogenizer and a 3.8% aqueous solution of ammonium persulfate 42
Were separately dropped into the above polymerization vessel uniformly over 3 hours, and further reacted at 82 ° C. for 2.5 hours to complete the polymerization. The obtained copolymer emulsion (hereinafter referred to as B
-1) was 55% solids concentration. Table 2 shows the monomer composition (%).

Synthesis Examples 7 to 9 (Emulsions B-2 to B-
Synthesis of 4) In the same manner as in Synthesis Example 6, copolymerization was carried out in an amount based on the type and composition% of the monomers shown in Table 2 to obtain a solid content concentration of 54 to 55.
% Copolymerized emulsions (B-2 to B-4) were obtained.

[0028]

[Table 2]

Example 1 110 parts of the emulsion A-1 obtained in Synthesis Example 1 (60 parts in terms of solid content), 55 parts of the emulsion B-1 (30 parts in terms of solid content), and a petroleum wax emulsion (paraffin wax, solid 11 parts (solids equivalent 5 parts) having a concentration of 45% and a melting point of 57 ° C.) and polyethylene wax emulsion E.
-1 (solid content 25%, molecular weight 15,000, acid value 1
50) and 20 parts (5 parts in terms of solid content) were placed in a container, and stirred and mixed at room temperature for 30 minutes. Table 3 shows the number of parts in terms of solid content.

This mixture was applied to the untreated kraft paper surface with a bar coater so that the thickness of the dried film became 10 g / m ^2, and dried at 130 ° C. for 30 seconds to obtain a test piece. About the obtained test piece, moisture permeability, waterproofness, disintegration,
Folding whitening property, slip resistance, blocking resistance, and heat sealing property were measured. The results were as shown in Table 4.

The measurement of each characteristic was performed as follows. a. Moisture Permeability The moisture permeability was measured by a water vapor permeability test method (JIS Z0208) by a cup method under a constant temperature and humidity condition (40 ° C., 90% RH). b. Using a test piece, a box of 5 cm long × 5 cm wide × 2.5 cm high was made using the test piece, 40 ml of deionized water was put therein, and after standing for 24 hours, the state of seepage of water was examined and evaluated in four steps. ◎: does not exude, ○: hardly exudes, △: partially exudes, ×: exudes

C. Water disintegration Approximately 2.5 in normal temperature tap water so that pulp concentration becomes 3%.
A test piece of cm square was put therein, and this was stirred for 15 minutes with a standard disintegrator (rotation speed: 3000 rpm) described in the Handsheet Adjustment Method for Pulp Test (JIS P8209), and the disintegration state was visually evaluated in four steps. . ◎: Completely disintegrated, ○: Almost disintegrated, Δ: Partially disintegrated, ×: Not disintegrated d. Alkali disintegration A test piece is put into a 1% aqueous solution of caustic soda at 45 ° C. so that the pulp concentration becomes 0.5%, and the mixture is stirred for 45 minutes with a stirrer (rotational speed 200 rpm), and the disintegration state is visually and microscopically observed. It was evaluated on a 4-point scale. ◎: Completely disintegrated, ○: Almost disintegrated, △: Partially disintegrated, ×: Not disintegrated

E. Folding whitening property The whitening state of the coating film at the fold portion when the test piece was bent was visually evaluated in three stages. ◎: not whitened, Δ: partially whitened, Δ: whitened f. Slip resistance The static friction coefficient was measured by the slope method of the friction coefficient test method (JIS P8147). Depending on the type of coated paper,
Usually, a coefficient of static friction in the range of 0.6 to 1.2 is preferable.

G. Blocking resistance A test piece cut into a square of 5 cm square was coated on each other or between the coated surface and the non-coated surface, and was left for 24 hours in an atmosphere of 40 ° C. and 90% RH with a load of 10 kg placed thereon. . Thereafter, the paper was allowed to cool at room temperature, and the surface state of the paper when the test piece was slowly peeled was visually evaluated in four steps. ◎: no blocking, ：: slight noise but no blocking, Δ: partial blocking, ×: overall blocking h. Heat sealability The coated surface of the test piece is overlapped with the coated surface, and using a thermal gradient tester, 160 to 180 ° C. × 4 kg / cm ² × 10 sec.
After thermocompression bonding under the above conditions, the coating film was visually evaluated for heat sealability in three steps. ◎: Heat sealable, ○: Heat sealable but weak, ×: No heat sealable

Examples 2 to 7 and Comparative Examples 1 to 5 The components were stirred and mixed in the same manner as in Example 1 with the composition shown in Table 3 (the number of parts in terms of solid content), and test pieces were produced in the same manner. . The characteristics of the obtained test pieces were measured in the same manner as in Example 1, and the results are shown in Table 4. The polyethylene wax emulsion E-2 has a solid content of 30%, a molecular weight of 5,000 and an acid value of 60.

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

According to the novel moisture-proof and easily disintegrating coating agent of the present invention, the coating film formed therefrom imparts excellent moisture-proof and waterproof properties to paper, and has no drawbacks such as bending whitening and slippage.
It has good blocking resistance and heat-sealing properties, and easily disintegrates at the time of collecting waste paper. Therefore, it is extremely useful for paper processing because it has such characteristics.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-56-148997 (JP, A) JP-A-5-302299 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D21H 11/00-27/42

Claims (1)

(57) [Claims] (1) Styrene and other solubility at 25 ° C. of 1 g / water in 100 parts by weight of the total solid content.
A styrene-containing emulsion obtained by copolymerizing 80 to 97% by weight of a total of hydrophobic monomers of less than 0 g as a main component monomer composition is 40 to 90 parts by weight in terms of solid content. (Meth) acrylates and other 2
It is obtained by copolymerizing 90 to 97% by weight of a total of monomers having a solubility in water at 5 ° C of 1 g / 100 g or more and 3 to 10% by weight of α, β ethylenically unsaturated carboxylic acid. (Meth) acrylic acid ester-based emulsion has a solid content of 5 to 50 parts by weight, and (c) a melting point of 40 to 100 ° C.
Oil wax emulsion has a solid content of 2-1
5 parts by weight and (d) an acid value of 30 to 2 having a carboxyl group
A moisture-proof and easily disintegrating coating agent for paper comprising an aqueous emulsion in which an emulsion of a polyethylene wax of No. 00 is added in an amount of 0 to 15 parts by weight in terms of solid content.