JPS5927706B2 - Manufacturing method of cardboard - Google Patents

Description

[Detailed description of the invention] This invention relates to a method for manufacturing corrugated board.

Corrugated cardboard is constructed by laminating a flat liner to the top of a corrugated medium, and is assembled into a corrugated cardboard case and used extensively as a material for packaging containers.

The corrugated cardboard used for the packaging container is required to have strength such as burst resistance and pressure resistance, and compressive strength is an important quality factor, especially for the core that constitutes the corrugated cardboard.

In corrugated corrugating, the corrugating paper is passed between a pair of heated corrugating rolls installed in the single facer section of a corrugator, which is a corrugated sheet manufacturing machine, and molded under pressure. In the stage forming process, the core base paper is subjected to external forces such as tension, compression, bending, and shearing, and if the core is not compatible with these external forces, normal stage formation will not be possible, resulting in high-low phenomenon and other problems. Top break, step jump,
Unfavorable phenomena such as step flow occur.

This compatibility of the medium is called corrugated line suitability or step formability, and is an important factor that affects not only the medium manufacturing process but also the quality of corrugated board products such as packaging containers.

Therefore, the core used in corrugated cardboard is required to have the functions required for the finished cardboard case, compressive strength that affects the pressure resistance, functions in the core manufacturing process, and step formability.

In order to improve the compressive strength of the core after molding, it is easy to increase the basis weight of the core paper, but the size of the steps of the core is standardized, As the basis weight of the core increases relative to the corrugation, the thickness and rigidity also increase, and the above external forces that the core paper receives when forming the corrugation also increase, making it difficult to form the corrugation properly and decreasing the production speed. Declines rapidly.

The basis weight of the medium paper currently in use is 125.
g/772” is common.

Another method for improving the compressive strength of the core paper is to internally add strength-improving agents such as polyacrylamide, polyethyleneimine, epoxidized polyamide, or urea resin during the manufacturing process of core base paper, or to beat the pulp used. These methods improve not only the compressive strength but also the tensile strength, but on the other hand, they become brittle or the folding strength decreases, causing problems during step molding. There are limits to how much improvement can be made.

Furthermore, the core material obtained by internally adding the above-mentioned strength improver is difficult to adhere with commonly used starch adhesives.

On the other hand, in order to improve the step formability of core paper, methods have been adopted in which the density is maintained low in the core paper manufacturing process or the formation is slightly broken during the paper making process. In this case, the strength in compression, tension, bursting, etc. is reduced.

As mentioned above, it is difficult to simultaneously improve both the stage formability of the core paper and the compressive strength of the core after molding.
Even if the compressive strength of the produced medium base paper is unnecessarily improved, the rigidity and compressive strength after step forming are not maintained.

Sodium silicate has long been used as an adhesive to the liner by being applied to the top of corrugated corrugated corrugated cardboard during the production of corrugated board sheets, but when sodium silicate is used as an adhesive, Currently, starch adhesives are mainly used as the adhesive between the liner and the top of the corrugated corrugated board because of problems such as speed limitations and the occurrence of contamination and discoloration of the corrugated board surface due to alkali stain.

Since sodium silicate is easily available and inexpensive in Japan, the present inventors have proposed using alkali metal silicate salts such as sodium silicate to improve the strength such as the compressive strength of the medium and the step formability. As a result of intensive research, we have achieved this invention.

That is, this invention coats or impregnates alkali metal silicate on solid paper to a solid content of 2 to 20 g/m, and then dries it, then heats and pressurizes it to form a step-formed medium.A liner is applied to at least one side of the medium. This method of manufacturing corrugated board is characterized by pasting them together using starch adhesive.

The medium paper used in this invention is made from waste paper pulp, kraft pulp, semi-chemical pulp, etc., and has a standard basis weight of 125i/rr? The commonly used range is 115 to 250 ji/rn.

In terms of the effect of improving step formability, compressive strength after step forming, etc. of this invention, materials with a basis weight of less than 115 g/m'' and up to 50 i/lri', which were conventionally considered to be unsuitable as medium cores. can also be applied.

The alkali metal silicate salt adhered to the above-mentioned medium base paper is represented by the general formula M2O-nSiO2, where M is an alkali metal such as sodium, potassium, or lithium;
Further, n is in the range of 0.5 to 4 and is generally commercially available.

The above-mentioned alkali metal silicate may be added to any corrugator during the paper-making process of the corrugated paper, after the paper-making process of the corrugated base paper, or before the paper is passed through the single facer in the stage forming process during the production of the corrugated paper. At the location, the aqueous solution of the alkali metal silicate is applied, sprayed or impregnated, and then dried and applied.

The solid content amount of alkali metal silicate is 2 to 20 g/m,
Preferably it is 2 to 10 g/rrf.

The following experiment was conducted to find out the relationship between the solid distribution amount and the physical properties of the core.

Experimental example 1 Medium-sized paper with a basis weight of 100.9/m was prepared according to JIS-1408.
No. 3 sodium silicate aqueous solution (concentration 20% by weight, N
a2O:5i02 molar ratio 1:3) and squeezed by changing the squeezing amount, the impregnated base paper was dried by contacting it with a dryer roll at 110°C for 15 seconds, and then
The compressive strength (JIS-
p8126) and the MIT bending strength (JIS-P8115) in the machine direction (MD) were measured, and the results are shown in Table 1.

As shown in Table 1 above, the amount of sodium silicate added is 2g.
If it is less than /m, the improvement in compressive strength is small, and 20j
When exceeding i/rri', the compressive strength improves, but MI
Since the T-folding strength decreases, it becomes difficult to form steps in a single facer of a corrugator.

An acid and a metal salt can be used together in the treatment of the alkali metal silicate salt.

Conventionally, when using sodium silicate as a leakage prevention agent, it is known that the purpose is to add an acid or a metal salt to sodium silicate to obtain a hard gel and at the same time shorten the reaction rate. In this invention, when an acid and a metal salt are mixed into an aqueous solution of an alkali metal silicate, the acid and metal salt must have a slow reaction rate.

Boric acid and the like are exemplified as additives for this purpose.

In addition, if acids and metal salts are applied to the medium base paper before and after applying the alkali metal silicate without mixing with the alkali metal silicate, there is no problem even if the reaction rate is fast. Examples of acids and metal salts include metal salts such as sodium sulfate and lead sulfate, and acids such as sulfuric acid and phosphoric acid.

The amount of acid and metal salt is preferably 0.1 to 10 parts by weight per 100 parts by weight of alkali metal silicate.

By using the above-mentioned acid and metal salt in combination, the effect of improving the compressive strength of the batten and the step formability of the batten base paper is not inhibited, and there is an effect of preventing alkaline staining, improving the compressive strength, and waterproofing property.

The medium base paper treated with an alkali metal silicate salt is dried to a moisture content in the range of 3 to 10, and then heated and pressurized to form into steps.

Heating temperature is 60-230℃, pressurization is 10-90kg/C
A range of r/L is preferred.

The above heating and pressurization are performed in the single facer part of the corrugator when forming the core into stages.

Heating temperature during step molding and corrugated crush strength (
The following experiment was conducted regarding the relationship with CCT).

Experimental example 2 Basis weight 110. The surface of F/m medium paper base paper was preheated to 90℃, and No. 4 sodium silicate (Na20:S) was coated with a roll coater.
iO2 molar ratio -1:4) aqueous solution with a solid content of 5.5 g
/71j, immediately dried by contact with a dryer roll for 15 seconds, molded into stages by changing the temperature during step forming of Conco Cola Furuta, and then conditioned for 24 hours under environmental conditions of 20°C and 65.1RH. The core corrugated crush strength (CCT) was measured in this state, and the values are shown in Table 2.

For comparison, the same test was performed on medium paper before the sodium silicate treatment, and its physical properties are also listed.

Moreover, the index is the ratio of Experimental Example 2 to Comparative Example.

As is clear from Table 2, as the stage forming temperature increases, CC
The T value improves, and the CCT value becomes optimal in the range of 149 to 233°C.

Further, the CCT value of Experimental Example 2 at each stage molding temperature is larger than the maximum CCT value of Comparative Example, and its index is about 1.6.

Therefore, even if the corrugated board is manufactured by lowering the heating temperature, the corrugated board that maintains and improves sufficient strength can be obtained, and the thermal energy required during the manufacturing of the corrugated board can be saved.

If the above corrugated crush strength (CCT) is A
According to the test method specified by STM-D2806, a corrugated paper sample with a width of 12.7 mm (in the longitudinal direction of the long paper) and a width of 12.7 mm was tested using a Concora fluter at a corrugated roll temperature of 17 mm.
This is the value (kg) obtained by measuring the strength at which the material was molded into an A-flute stage at 7° C. and a nip pressure of 10 kg, placed in a predetermined support, and then subjected to vertical compression to break.

To explain the above-described predetermined support with reference to the drawings, reference numeral 1 denotes a fixing base having a step portion 1a formed by cutting out the upper half,
On the missing side surface, there are wave-shaped teeth 1b that match the shape of the core, which is formed in stages using a concora fruiter.

Reference numeral 2 denotes a crimping table placed on the stepped portion 1a of the fixing table 10, and has wave-shaped teeth 2b on its side surface corresponding to the teeth 1b on the side surface of the fixing table 1.

The pitch P of the wave-shaped teeth 1b on the side surface of the fixed table 1 is 8.5.
0mm, tooth depth D is 4.75mm, tooth tip curvature radius r is 1.50mm, tooth root curvature radius R is 2.0mm, height 6
．． The width is set to 35 mm (half the width of the sample).

Wave-shaped teeth 1b and 2 of the fixing table 1 and the crimping table 2, respectively.
After vertically inserting the step-molded medium core sample A into the gap 3 created by meshing b, the crimping table 2 is horizontally crimped to apply uniform pressure in the length direction of the sample. Hold the lower half of the

A compressive load is then applied vertically to the protrusion of the sample.

The corrugated boards produced in this invention include commonly used single-sided corrugated cardboard, double-sided corrugated cardboard, and multi-sided corrugated cardboard.

Examples of the present invention will be described below.

Example 1 Aqueous solution of No. 5183 sodium silicate (concentration 20% by weight) was coated with a gravure coater at a solid content of 9.79/m to a medium paper with a basis weight of 11 i/m, which was made from waste paper pulp.
K coated, and then dried in a hot air drying chamber at 110°C with a moisture content of 10.
After drying to %, roll it up without applying pressure.

The core paper is lined with front and back liners (JIS-P3902, B
It was fed to a corrugator (step molding pressure 40 kg/cm, temperature 1.80'C) with grade basis weight 22 (L9/G) at a lamination speed Loom/min, and A-flute double-sided corrugated board was made using ordinary starch adhesive. was manufactured.

Furthermore, using the double-sided cardboard, the inner dimension is 36o x 300 x 25
Manufactured a 0-fight A-1 type glue joint case.

Table 3 shows the physical properties of the above-mentioned medium, corrugated board, and corrugated pole case.

For comparison, a medium without sodium silicate treatment was also tested in the same manner, and its physical properties are also listed.

In Table 3, the basis weight of the medium is JIS-P8124, the thickness is JIS-P8118, the tensile strength is JIS-P8113,
The bursting strength is a value measured according to JIS-P8112.

Concola flat crush strength (CMT) u
, is the value of the plane compressive strength of the sample molded into the A flute stage in the measurement of the above-mentioned corrugated crush 'M (CCT).

Vertical compressive strength and planar compressive strength of corrugated board are JIS-
The values were measured according to ZO401, and the pressure resistance of the cardboard case was measured according to JIS-20212.

In all measurements, the humidity was adjusted for 24 hours at 20° C. and 65% RH, and then measurements were made under the same conditions.

Moreover, the index is the ratio of Example 1 to Comparative Example 1.

As seen in Table 3 above, the example for Comparative Example 1 [the compressive strength of the medium was 20%, the bursting strength was 38%,
Tensile strength is improved by 34%.

Normally, when the compressive strength, bursting strength, and tensile strength improve, the folding strength tends to decrease, but contrary to this tendency, the folding strength of Example 1 improved by 41% and CMTU by 5.7%. There is.

This means that the medium treated with sodium silicate not only improves the rigidity but also improves the corrugated formability without impairing the flatness of the corrugated board manufactured using this medium. The vertical compressive strength and the compressive strength of the cardboard case were also improved compared to Comparative Example 1.

Example 2 Basis weight 1.03 El with addition of 0.5 weight factor of sulfuric acid
/ rn' medium paper raw material was processed into a JI83 sodium silicate aqueous solution (concentration 2
0% by weight) with a size press to a solid content of 5, 7 ji
/ 771: and then dried to a moisture content of 5%, and a laminating speed of 150 m/min was carried out to produce A-flute double-sided corrugated cardboard in the same manner as in Example 1. Furthermore, a corrugated pole case similar to that in Example 1 was manufactured. was manufactured.

Table 4 shows the physical properties of the above-mentioned cardboard, cardboard, and cardboard case, as well as the physical properties of Comparative Example 2 which was not subjected to the sodium silicate treatment.

As shown in Table 4, various physical properties were improved to the same extent as in Example 1.

Example 3 Medium paper with a basis weight of 112.9/i was made at a papermaking speed of 350 m/
In the paper-making process, No. 4 sodium silicate aqueous solution (concentration 20% by weight) was applied with a calender to a solid content of 4.5 g/7 g, and then dried to a moisture content of 5 parts to 20 kg/crIL.
A double-sided corrugated board with an A flute was manufactured in the same manner as in Example 1 by winding and laminating at a speed of 200 m/min, and a corrugated cardboard case in the same manner as in Example 1 was further manufactured.

Table 5 shows the physical properties of the above-mentioned cardboard, cardboard, and cardboard case, as well as the physical properties of those not treated with sodium silicate.

Example 4 The same medium cardboard (basis weight 110 g/m'') as in Example 1 was made at a papermaking speed of 350 m/min, and the same sodium silicate aqueous solution as in Example 1 was added to the solid content using a gravure coater. A-flute double-sided corrugated board was manufactured using starch adhesive at a lamination rate of 10.00 g/m' and lamination speed 160 m/min as in Example 1; Manufactured a case.

For comparison, a latex emulsion was applied instead of the above-mentioned sodium silicate to produce cardboard, cardboard, and a cardboard case.

The physical properties of the above-mentioned cardboard, cardboard, and cardboard case are shown in Table 6 below.

As shown in Table 6 above, in Comparative Example 4, in which latex emulsion was applied instead of sodium silicate, the compressive strength of the core was the same as in Example 4, but when it was made into a corrugated board or a corrugated cardboard case, the compressive strength Example 4 is superior in strength and double side adhesive strength.

This is because sodium silicate has good permeability into paper and does not interfere with the adhesive effect of the starch adhesive.

[Brief explanation of drawings]

The figure is a perspective view of an instrument used for measuring corrugated crush strength (CCT).

Claims (1)

[Claims] 1 Solid content amount of alkali metal silicate on medium base paper 2
~20 jp / 771'' A method for producing corrugated board, characterized by applying or impregnating it to a sheet of paper, drying it, then heating and pressurizing it to mold it into steps, and then attaching a liner to at least one side of the corrugated cardboard using a starch adhesive.