JPS6221538A - Reinforced corrugated board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to reinforced cardboard. More specifically, the present invention relates to corrugated board reinforced by impregnating one or both sides of liner paper or core corrugated paper with an acrylic emulsion and a hardening agent.

There is a strong demand for the packaging industry to improve the performance of corrugated cardboard as part of the rationalization of logistics departments in various industries.

The advantages of cardboard containers are that they are lightweight compared to other packaging containers, can be mass produced, can be folded, can be reused as cardboard, and can be used as pulp raw material. For example, it is possible to reuse the materials.

On the other hand, its drawbacks include that it is inferior in strength compared to other materials, and is relatively weak against sheet music.

Above all, strength is the most important factor for distribution containers, and various efforts have been made to improve strength.

(Prior art) Typical methods include increasing the basis weight of liner paper and core corrugated paper that make up the base paper for corrugated board;
Furthermore, it is possible to create a double-screen configuration, using two core corrugated papers.
These include pasting sheets together and processing the liner paper and core full-gate paper with resin.

(Problems to be Solved by the Invention) Among these methods, the method of increasing the basis weight has a large strength improvement effect, but not only does it increase the weight of the corrugated board, but it also makes the work during folding difficult due to the springback effect. It has poor elasticity, and cracks may appear at the bent portion.

Furthermore, if the double screen configuration is adopted, the thickness of the corrugated board increases, and in this case as well, the problem during the bending process is almost the same as when the tsubo 11 is increased.

Core Korgu 1 - When pasting papers together or applying resin ink, care must be taken in selecting the material of the adhesive and coating agent. The reason for this is that when used cardboard is N1-disintegrated with water to produce '11 recycled pulp, it must be disintegrated uniformly in water.

Conventionally, there are the following corrugated core corrugated paper or liner paper coated with resin.

For example, it is coated with a polyisocyanate compound, melamine resin, urea resin, etc.

However, when corrugated cardboard coated with these materials is defrosted with water and used as recycled pulp as described above, it does not disintegrate uniformly, and therefore I! J3H may cause defects in recycled paper.

In order to solve these problems, it is possible to select a polyvinyl acetate emulsion, which is the most common aqueous emulsion, as the resin to be applied, but applying a polyvinyl acetate emulsion will not increase the strength. The effect is small.

The reason for this is that vinyl acetate emulsion has a slow penetration rate into the core paper, liner paper, etc. that are the constituent materials of corrugated cardboard sheets, so it is not possible to increase the amount of coating, which is a factor in increasing strength. In order to do this, the coating speed must be slowed down.

This is not preferable because it leads to low productivity.

Even if a penetrant is added for the purpose of improving the permeability of vinyl acetate emulsion into materials, there is almost no improvement effect.In view of this situation, the present inventors conducted intensive studies and found that acrylic emulsion or acrylic-based emulsion The company discovered that a composition consisting of a system emulsion and a curing agent penetrates into the corrugated board material at a slow rate, and as a result, has the effect of increasing various strengths and is excellent in productivity, and has developed the following invention. Completed.

(Structure of the Invention) That is, the present invention is "a reinforced corrugated board characterized by impregnating liner paper and core paper with an acrylic emulsion or an acrylic-styrene emulsion and a hardening agent."

The corrugated board of the present invention is made of liner paper of about 1220 g/Td, which is the constituent material of ordinary corrugated board, and liner paper with a thickness of about 112 g/Td.
Apply an acrylic emulsion and a material containing melamine resin as a hardening agent to one or both sides of a core corrugated paper of about 0g/TIt and harden it as it dries, increasing the strength in the same way as increasing the basis weight. It is manufactured by gluing together the same materials using ordinary adhesives.

The reinforced cardboard of the present invention will be explained in detail below.

The acrylic emulsion used in the present invention has basically the same composition as the aqueous emulsion normally used for adhesives, various binders, paints, etc., but it is intended to increase the strength of corrugated board, and has a moderate amount of Toze L
1. Since it is necessary to have film-forming properties, the secondary transition temperature of the resin component in the emulsion is 20 to 100.
℃ is selected.

When the X-th transition temperature is less than 20°C, the strength improvement effect is small;
When the temperature exceeds 100°C, it becomes hard but brittle.

The secondary transition humidity is set in the following manner. In other words, since the secondary transition temperature unique to each homopolymer made by independently polymerizing each monomer constituting the copolymer is known from various documents, this and the weight of each monomer are Calculate and set the rate using the formula below.

1 Wa wb -=-+-4----- Tg Taa Tab However, Tg: Secondary transition temperature of copolymer (°K) Tga:
Second-order transition temperature Wa of homopolymer of component a: Weight fraction T of component a g b: Second-order transition temperature W of homopolymer of component b
b: Weight fraction of component b The following numerical values were used for the secondary transition temperature of the lli homopolymer of each monomer.

Acrylic acid: 379°C Edyl acrylate: 251°C Methyl methacrylate: 378°C Hydroxyethyl methacrylate = 328°C Butyl acrylate: -55°C 2-ethylhexyl acrylate 85°C Styrene: 10
0°C [Translated by Shigeyoshi Onogi, ``Mechanical Properties of Polymer Composite Materials'' ■ Kagaku Dojin (1976)] In the present invention, the acrylic emulsion refers to acrylic acid, methacrylic acid, or their various ester components alone. Polymers include copolymers and monomers thereof.
It is a copolymer of styrene and styrene, and is emulsion polymerized by a conventional method.

The acrylic emulsion used in the present invention is mixed in the following manner.

Potassium persulfate, ammonium persulfate, etc. are used as a catalyst at a temperature of 60 to 90°C and under normal pressure.
．． 1 to 15% of O is added, and a copolymerization reaction is carried out for 3 to 10 hours in a nitrogen gas atmosphere.

In addition, the characteristic of the resin impregnated into the constituent material of the reinforced cardboard of the present invention is that it is not only an acrylic emulsion, but also a specific hardening agent is added in a certain amount to the weight of the resin component of the emulsion. .

Appropriate curing agents include melamine resins, urea resins (for example, Sumitomo Chemical Co., Ltd.'s Sumiret, etc.), epoxy resins (for example, Nagase Kasei Co., Ltd.'s Denacol, etc.), and the use of melamine resins has a particularly large strength-improving effect.

Melamine resins are generally commercially available such as Sumimaru (manufactured by Sumitomo Chemical), Cymel, (manufactured by Mikata Toatsu), etc.
It is used in the form of a 0-90°C aqueous solution or a methanol mixed aqueous solution.

The addition of the curing agent (2) is in a weight ratio of 5 to 15%, preferably about 10%, based on the resin component in the emulsion. A curing accelerator may be added to the curing agent if necessary. A suitable addition amount is about 10% by weight based on the curing agent.

The amount of curing agent is 5% based on the resin solid content in the emulsion.
If it is less than 15%, the strength improvement effect will be small, and if it exceeds 15%, it will not be uniformly disintegrated when it is disintegrated in water and used as recycled pulp, impairing the quality of the recycled paper produced.

The solid content of the acrylic emulsion used is 40-50%
Suitably, the curing agent and curing accelerator are mixed into the emulsion immediately prior to impregnation into the corrugated material. In terms of productivity, the most suitable method for impregnating corrugated cardboard materials is a coating method using a roll coater.

When coating the corrugated cardboard material, it is more convenient to coat the back surface than the front surface because the impregnation into the interior is faster and the material dries more easily.

Further, when coating with a cardboard material, which may be coated on one side, use of a penetrant improves workability and increases the strength improvement effect. The penetrating material is a polyoxyethylene adduct system such as Nonion S-210 (
(manufactured by NOF Corporation) and sulfosuccinic acid-based products such as Rapizol B-80 (manufactured by NOF Corporation) are used, and the appropriate amount of addition is about 3% based on the emulsion. Even if the amount added is increased further, the penetration speed will not be increased very much.

The strength improvement effect increases as the coating amount increases to a certain extent, but considering productivity and economic efficiency, the resin coating amount is 10 to 40 g/TIt.

Preferably it is 20 to 30 g/Td.

Next, we will discuss the coating conditions for the cardboard constituent materials.

The coating speed with a roll coater is 10 to 60 m/min.
Coating at room temperature and continuously heating at 80-150℃
After the impregnating liquid dries and hardens, each material is bonded with an adhesive.

(Effects of the Invention) Next, the effects of the present invention will be explained using Examples and Comparative Examples.

Examples and Comparative Examples The various physical properties measured in the Examples and Comparative Examples were measured by the following methods.

Coating amount: J: Resisted in measuring the dry coating amount of the base paper before and after liquid coating.

Ring crush strength = Compressive strength of paperboard): Length 15
A paperboard test piece of 2.5 mm and width 12.7 mm was inserted into the circular groove of the sample holder to form a ring of a certain size, and the compressive strength against the load in the axial direction of one ring was measured using a load cell type universal testing machine. It was measured. (Based on JIS, P-81 26) Bursting strength: A test piece was firmly clamped between two annular planes, pressure was applied until the test piece broke, and the maximum pressure was measured using a pressure gauge. (Based on J Is, P-8112 for core, J Is, P-8131 for liner paper and cardboard sheets 1 to 1) Vertical compressive strength: Measured by the same method as end crush strength.

Overall compressive strength: The two factors in the theoretical formula (the most common example, the Cricut formula) that calculates the compressive strength of a box from the physical properties of the base paper that makes up the cardboard (ring crush strength), and the constant length of the cardboard The sum of the ring crush strengths of the liner paper and core base paper that make up the flute (perpendicular to the flute).

Note that the liner paper, which is the constituent material of the cardboard used in this example and comparative example, has a basis weight of 220 g/m
The RK-220 and C-210° core corrugated papers are 5CP-120 base paper with a basis weight of 120 g/TIl.

Table 1 also lists the types and amounts of each resin material, curing agent, curing accelerator, and penetrant used in each example and comparative example, the amount of resin deposited, and each physical property obtained.

The composition of each J-mulsion monomer listed in Table 1 is as follows.

PA=2'77 Composition Methyl methacrylate 82% Ethyl acrylate 14% Glycidyl methacrylate 3% Acrylic acid 1% PA-275 Composition Styrene 52% Butyl acrylate 31% Hydroxyethyl methacrylate 1 note 15% Acrylic acid 2
% PA-274 Composition Methylone 34% Methyl methacrylate 34% Butyl acrylate 29% Glycidyl methacrylate 2% Acrylic acid 1% ABA182 Composition Vinyl acetate 100% From the results listed in Table 1, the acrylic emulsion and curing agent according to the present invention It is clear that the reinforced cardboard impregnated with the present invention exhibits excellent emulsion penetration effect and strength improvement effect.

Claims (1)

[Scope of Claims] (1) A reinforced corrugated board characterized in that liner paper and core base paper are impregnated with an acrylic emulsion or an acrylic-styrene emulsion and a hardening agent. (2) The reinforced cardboard according to claim (1), wherein the acrylic emulsion is an emulsion consisting of 82% methyl methacrylate, 14% ethyl acrylate, 3% glycidyl methacrylate, and 1% acrylic acid. (3) The reinforced cardboard according to claim (1), wherein the hardening agent is a melamine resin. (4) The reinforced cardboard according to claim (1), wherein the curing agent is an epoxy resin. (5) The reinforced cardboard according to claim (1), wherein the curing agent is a urea resin. (6) The second-order transition temperature of the resin component in the acrylic emulsion is 20 to 1.
The reinforced cardboard according to claim (1), characterized in that the temperature is 00°C. (7) The reinforced cardboard according to claim (1), wherein the curing agent is added in an amount of 5 to 15% by weight based on the resin solid content in the acrylic emulsion.