JPH07258307A - Method for producing aqueous emulsion and easily disintegratable moisture-proof paper - Google Patents

Abstract

(57) [Summary] [Structure] A method for producing an aqueous emulsion containing a copolymer composed of the following (A) to (C) and having a glass transition temperature of −15 to 30 ° C. Do (A)
To (C), a method for producing an aqueous emulsion in which (A) to (C) are emulsion-polymerized in the presence of 2 to 25 parts by weight of wax per 100 parts by weight, and to at least one surface of the base paper by the above method. An easily disintegratable moisture-proof paper obtained by coating 5-30 g (solid content basis) / m ² of the produced aqueous emulsion. (A) Aromatic vinyl compound unit 10 to 50 wt% (B) (Meth) acrylic acid ester unit 25 to 85 wt% (C) α, β-ethylenically unsaturated carboxylic acid unit 5 to
25% by weight [Effect] An easily disintegratable moisture-proof paper having excellent performances in all respects of moisture resistance, easy disintegration property, blocking resistance, and anti-slip property, and an optimum aqueous emulsion for obtaining the easily disintegratable moisture resistant paper. A manufacturing method can be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aqueous emulsion and an easily disintegratable moisture-proof paper obtained by coating an aqueous emulsion produced by the method.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of resource saving, there is an increasing demand for collecting used paper, dissolving it in water, etc., and then recycling it again into paper. The paper that can meet these demands needs to have so-called easy disintegration, which easily disintegrates into fine fibers when dissolved in water or the like.

By the way, one major application of paper is in the field of packaging paper. The packaging paper is usually required to have moisture resistance. However, the moisture-proof property and the above-mentioned easy disintegration property are essentially contradictory properties, and it is difficult to realize both of these two properties, that is, to realize a paper excellent in moisture resistance property and also excellent in easy disintegration property. there were. For example, as a paper with excellent moisture resistance, a base paper laminated with polyethylene etc.,
So-called laminated paper is known, but it does not have a disintegrating property.

By the way, Japanese Patent Laid-Open No. 61-47896 discloses an easily disintegratable moisture-proof paper obtained by coating a base paper with a wax emulsion containing styrene-butadiene rubber latex. However, the paper obtained by this method is unsatisfactory in that blocking due to the winding pressure during coating tends to occur in a hot and humid atmosphere in summer.

Further, Japanese Patent Laid-Open No. 5-29200 discloses that
An easily disintegratable moisture-proof paper having a well-balanced improvement in moisture resistance, easy disintegration property and blocking resistance is disclosed. However, the moisture-proof paper is insufficient in terms of slip resistance. That is, when the wrapping papers are overlapped with each other, the papers slip and the load collapses, which is inconvenient.

[0006]

In view of the above situation, the problem to be solved by the present invention is to solve the problems of the prior art and to provide all of moisture resistance, easy disintegration property, blocking resistance and anti-slip property. In view of the above points, the present invention provides an easily disintegratable moisture-proof paper and a method for producing an aqueous emulsion most suitable for obtaining the easily disintegratable moisture-proof paper.

[0007]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems.

That is, one of the inventions is composed of the following (A) to (C) and has a glass transition temperature of -1.
A method for producing an aqueous emulsion containing a copolymer having a temperature of 5 to 30 ° C. in the presence of 2 to 25 parts by weight of wax per 100 parts by weight of (A) to (C) in total ( The present invention relates to a method for producing an aqueous emulsion in which A) to (C) are emulsion-polymerized. (A) Aromatic vinyl compound unit 10 to 50 wt% (B) (Meth) acrylic acid ester unit 25 to 85 wt% (C) α, β-ethylenically unsaturated carboxylic acid unit 5 to
25% by weight

The other invention of the present invention is easily obtained by coating 5-30 g (solid content basis) / m ² of the aqueous emulsion produced by the above method on at least one surface of the base paper. It relates to disintegratable moisture-proof paper.

The aqueous emulsion obtained by the production method of the present invention comprises (A) an aromatic vinyl compound unit and (B)
It contains a copolymer composed of (meth) acrylic acid ester units and (C) α, β-ethylenically unsaturated carboxylic acid units.

Specific examples of the aromatic vinyl compound (A) as the aromatic vinyl compound unit include styrene and α-
Methyl styrene etc. can be mentioned. Preferred is styrene. The content of the (A) aromatic vinyl compound in the copolymer is 10 to 50% by weight, preferably 15 to 45% by weight. If the content is too small, the moisture resistance is poor. On the other hand, if the content is too large, the glass transition temperature of the copolymer is high and the film-forming property is deteriorated, so that the moisture resistance is poor.

(B) The (meth) acrylic acid ester as the (meth) acrylic acid ester unit means an acrylic acid ester or a (meth) acrylic acid ester. Specific examples of these include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, heptyl acrylate,
Octyl acrylate, 2-ethylhexyl acrylate,
Decyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate,
Propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, 2-methacrylic acid
Examples thereof include ethylhexyl, dodecyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like.
In addition, these may be used individually by 1 type, or may be used in mixture of 2 or more types.

Specific examples of the α, β-ethylenically unsaturated carboxylic acid (C) as the α, β-ethylenically unsaturated carboxylic acid unit include acrylic acid, methacrylic acid, crotonic acid, itaconic acid and maleic acid. , Fumaric acid, maleic anhydride and the like.

The content of the (C) α, β-ethylenically unsaturated carboxylic acid unit in the copolymer is 5 to 25% by weight, preferably 8 to 20% by weight. If the content is too small, the easiness of disintegration is poor, whereas if the content is too large, the viscosity of the emulsion is high and the moisture resistance is poor.

The production method of the present invention is subjected to polymerization (A).
(A) to (C) are emulsion polymerized in the presence of 2 to 25 parts by weight of wax per 100 parts by weight of (C) to (C).

The wax used has a melting point of 40.
Those in the range of -100 ° C are preferred. If the melting point is too low or too high, the moisture resistance may be poor.

Specific examples of the wax include paraffin wax, microcrystalline wax, paraffin wax containing a zirconium compound, and polyethylene wax.

The amount of wax used depends on the polymerization (A).
2 to 25 parts by weight, preferably 3 to 15 parts by weight, per 100 parts by weight of (C). If the amount used is too small, the moisture resistance is poor, while if the amount used is too large, the easy disintegration property and the blocking resistance are poor.

In the present invention, it is necessary to allow the wax to coexist in the polymerization system during the polymerization. When the wax is added to the emulsion after polymerization without using the present invention, the anti-slip property and the blocking resistance are poor, and the aqueous emulsion and the wax are separated during storage of the emulsion,
Poor storage stability.

The copolymer of the present invention has a glass transition temperature of -15 to 30 ° C, preferably -10 to 25 ° C. If the glass transition temperature is too low, blocking resistance is poor. On the other hand, if the glass transition temperature is too high, the film-forming property deteriorates and the moisture resistance is poor.

Regarding the glass transition temperature, a few g of the emulsion containing the copolymer was thinly spread on a film using a glass rod, and dried at 60 ° C. for 30 minutes or more. In a cell made of aluminum foil, and using a thermal analysis system (for example, SSC5000 thermal analysis system manufactured by Seiko Instruments Inc.) at 10 ° C /
It is determined by measuring at a temperature rising rate of min in the range of -100 ° C to 100 ° C.

The following methods can be mentioned as specific examples of the method for producing the aqueous emulsion of the present invention. That is, an emulsion obtained by emulsifying the components (A) to (D) of the present invention in water containing an emulsifier is added to water containing a polymerization initiator,
It may be emulsion polymerized. When polymerizing, pH
Modulators and chain transfer agents may be used.

As the emulsifier, a nonionic surfactant or an anionic surfactant is used. Examples of the nonionic surfactant of the nonionic dispersant include polyoxyethylene lauryl ether, polyoxyethylene octylphenol ether, polyoxyethylene nonylphenol ether, and other polyoxyethylene alkyl ethers; polyoxyethylene alkylphenol ethers,
Examples thereof include polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monooleate, and other polyoxyethylene sorbitan fatty acid esters; and polyoxyethylene polyoxypropylene block copolymers in which the amount of ethylene oxide added is 10 to 80% by weight. Examples of the anionic surfactant include sodium lauryl sulfate, sodium dodecylbenzene sulfonate,
Examples include sodium dialkyl sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenol ether sulfate, and the like.

In the present invention, various water-soluble polymers can be used as a protective colloid together with the emulsifier. Examples of the protective colloid include polyvinyl alcohol, partially saponified polyvinyl alcohol, fiber cellulose derivatives such as methyl cellulose and hydroxyethyl cellulose.

As the polymerization initiator, a water-soluble radical initiator used in ordinary emulsion polymerization, such as hydrogen peroxide,
Redox system such as potassium persulfate, sodium persulfate, ammonium persulfate, tert-butyl hydroperoxide alone or in combination with a reducing agent such as L-, D-ascorbic acid, sulfite, Rongalit, ferrous sulfate, etc. Can be used.

As the pH adjuster, acids such as hydrochloric acid, phosphoric acid, acetic acid, succinic acid, carbonic acid and salts thereof; bases such as alkali metal hydroxide, aqueous ammonia and amine are used.

As the chain transfer agent, those usually used in radical polymerization, such as mercaptans, can be used.

The polymerization system may be either batch system or continuous system. The polymerization reaction temperature is usually 30 to 85.
A range of ° C is suitable.

The easily disintegratable moisture-proof paper of the present invention has an aqueous emulsion of 5-30 g / m 2 of the present invention on at least one side of a base paper.
It is obtained by applying ² . If the coating amount is too small, the moisture resistance and water repellency are poor due to pinholes, fluffing of the base paper fibers, and the like, while if the coating amount is too large, there is a cost disadvantage. As the base paper, for example, kraft paper, high-quality paper, cellulose pulp paper such as corrugated cardboard can be used, but the base paper is not limited thereto.

To obtain the easily disintegratable moisture-proof paper of the present invention, for example, a base paper may be coated with a predetermined amount of an aqueous emulsion and then dried at about 120 ° C. or higher. If the temperature during drying is too low, the waterproof property of the easily disintegratable moisture-proof paper obtained may be poor.

The easily disintegratable moisture-proof paper of the present invention takes advantage of its excellent properties in a wide range of fields, such as newspaper roll wrapping paper,
It is optimally used for water resistant cardboard paper, wrapping paper for copy paper, etc.

[0032]

EXAMPLES Next, the present invention will be described with reference to examples. Example 1 600 g of styrene which is (A), 1100 g of 2-ethylhexyl acrylate which is (B), 300 g of methacrylic acid which is (C), and petroleum paraffin wax which is (D) (solid content concentration 30% by weight, melting point 50). (650C) and 650 ml of water containing 30 g of sodium laurate as an emulsifier were mixed with stirring to obtain an emulsion. The emulsion is
Water 10 containing 4 g of potassium persulfate which is a polymerization initiator
It was uniformly added to 00 ml over 4 hours for emulsion polymerization to obtain an aqueous emulsion (solid content: 52% by weight).
The polymerization temperature was 75 ° C.

Kraft paper (basis weight 80 g / m ² ) was coated with # 18 wire rod (coating amount 20 g / m ² ) with the above aqueous emulsion and dried at 120 ° C. for 2 minutes to give a grammage of The coated paper was about 95 g / m ² .

Various performances shown in Table 1 were evaluated. The evaluation method is as follows. (1) Water vapor transmission rate: measured according to the cup method JIS Z-0208. (2) Disaggregation property: 5 g of the sample was put into 250 ml of water, stirred for 30 minutes at a rotation speed of 3000 revolutions / minute using a homomixer, and the disaggregated state was visually observed. The evaluation was performed by ⊚ (complete defibration), ◯ (almost defibration), Δ (partially defibration) and × (not defibration). (3) Blocking resistance: A coated paper and a coated surface or a coated surface and a non-coated surface of coated paper are left at a temperature of 45 ° C., a humidity of 90% and a pressure of 5 kg / cm ² for 24 hours, and then, Peel by hand, from A (best: no resistance) to E
The evaluation was made on a scale of 5 (worst: material destruction). (4) Anti-slip property: According to JIS P-8147, the dynamic friction coefficient between the coated surface and the non-coated surface was measured. Usually, those having a dynamic friction coefficient in the range of 0.3 to 0.7 are preferable. (5) Leaving stability: After leaving the aqueous emulsion at room temperature for 1 month, the state of emulsion (whether separation, sedimentation and coagulation occurred) was visually observed. It was evaluated as “good” or “poor” depending on the presence or absence of abnormalities such as occurrence of separation, sedimentation and solidification.

Examples 2 to 3 and Comparative Examples 1 to 5 Example 1 was repeated except that the conditions shown in Tables 1 and 2 were used. The results are shown in Tables 1-2.

In all the examples satisfying the conditions of the present invention, the results to be satisfied are shown in all the evaluation items. On the other hand, Comparative Example 1 in which wax was not used during the polymerization was inferior in water vapor permeability. Comparative Example 2 in which the wax was used but added to the emulsion after the polymerization was completed according to the conventional method was inferior in blocking resistance, slip resistance and leaving stability. Comparative Example 3 using the copolymer not containing the component (C) of the present invention is inferior in easy disintegration property and blocking resistance. Comparative Example 4 using a copolymer having a low glass transition point is inferior in easy disintegration property and blocking resistance, and has a too large dynamic friction coefficient, which is not preferable. Commercially available polyethylene laminated paper is inferior in easy disintegration.

[0037]

[Table 1]

[0038]

[Table 2] ------------------------------------------ wt% (A) Styrene 30 30 50 10 Ichira (B) 2EHA * 1 55 55 50 80 Sales (C) MA * 2 15 15 0 10 Pone Glass transition temperature ℃ 0 0 0 -30 Li I Wax * 3 * 4 Et type-(W1) W1 W1 paper Melting point ℃-(50) 50 50 Weight wt-(7.5) 7.5 7.5 Evaluation moisture permeability g / m ² 24Hr ＞ 1000 12 40 15 30 Degradability ◎ ○ × △ × Blocking resistance Coated surface / Coated surface ACEEA Coated surface / Non-coated surface ABDEA Anti-slip property (Dynamic friction coefficient) 0.52 0.21 0.60 0.75 0.47 Leaving stability Good Poor * 5 Good Good --------------- −−−−−−−−−−−−−−−−−−−−−−−

* 1 2EHA: 2-ethylhexyl acrylate * 2 MA: methacrylic acid * 3 Wax: wax used together with the polymerization system during polymerization Type: W1 (petroleum paraffin wax) W2 (polyethylene wax) Amount: for polymerization Total 1 of the copolymer components (A) to (C) used
Parts by weight per 00 parts by weight * 4 Wax was not used during polymerization, and wax was added to the emulsion after polymerization * 5 Separation occurred

[0040]

Industrial Applicability As described above, according to the present invention, an easily disintegratable moisture-proof paper and an easily disintegratable moisture-proof paper having excellent performances in all points of moisture resistance, easy disintegration property, blocking resistance and anti-slip property are provided. It was possible to provide the most suitable method for producing an aqueous emulsion for obtaining.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08F 220/14 MLY 8619-4J D21H 19/20

Claims (3)

[Claims] 1. A process for producing an aqueous emulsion containing a copolymer comprising the following (A) to (C) and having a glass transition temperature of -15 to 30 ° C., which is subjected to polymerization (A): A method for producing an aqueous emulsion, in which (A) to (C) are emulsion polymerized in the presence of 2 to 25 parts by weight of wax per 100 parts by weight of (C) in total. (A) Aromatic vinyl compound unit 10 to 50 wt% (B) (Meth) acrylic acid ester unit 25 to 85 wt% (C) α, β-ethylenically unsaturated carboxylic acid unit 5 to
25% by weight 2. The method according to claim 1, wherein the melting point of the wax is 40 to 100 ° C. 3. An easily disintegratable moisture-proof paper obtained by coating 5-30 g (solid content basis) / m ² of the aqueous emulsion produced by the method of claim 1 on at least one side of a base paper.