JPS592473B2 - Cooling-setting starch adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling-setting starch-based adhesive particularly suitable for laminating corrugated cardboard. The object of the present invention is to provide an energy-saving adhesive that sometimes does not require heating operations.

Conventionally, starch-based adhesives have generally been used to manufacture corrugated cardboard.

This starch-based adhesive is made by gelatinizing the starch using a combination of steam heating and caustic soda and applying it to the surface of the cardboard to be bonded as a sticky gelatin.
A method is used in which the water content of this glue solution is evaporated by heating, and the bonding operation is completed by drying and solidifying it.

However, the thermal energy consumption in this lamination process accounts for a very large proportion of the total energy consumption of a corrugated board factory, and therefore, if this heating operation during lamination is omitted, the energy saving effect will be significant. Becomes large. Therefore, a heating operation is required when bonding the cardboard.

Developing a bonding method for corrugated cardboard that does not require conventional methods has become a challenge for the corrugated cardboard industry. In recent years, methods to meet the demands of the corrugated board industry include cold corrugation systems (a method of forming corrugated corrugated boards without the use of heat) and cold-set corrugated adhesives (chill-setting corrugated contact bonding agents). ) was developed.

In view of this situation, the inventors of the present invention conducted extensive research to develop a starch-based adhesive that hardens when cooled and is an adhesive for corrugated cardboard that does not require heating during lamination. In addition, the combination of high amylose corn starch with an amylose content of 50% or more and regular corn starch has excellent ability to achieve this purpose, and the low speed of lamination that occurs when high amylose corn starch is used alone. They discovered that the disadvantages of conventional methods (increase in adhesion failure rate) could be overcome to some extent, and filed a patent application.

The present inventors further continued this research and found that the combination of high-amylose corn and starch, regular corn starch, and waxy corn starch was effective in low-speed lamination without losing suitability for high-speed lamination. The present invention was completed based on the discovery that a starch-based adhesive that solidifies on cooling can be obtained, which can further improve the drawbacks.

That is, the present invention provides high amylose corn starch having an amylose content of 50% or more or modified starch thereof from 20 to 80% by weight, regular corn starch or modified starch thereof from 79 to 10% by weight, and waxy corn starch from 1 to 10% by weight ( It is a starch-based adhesive that hardens upon cooling and consists of a high-temperature, high-concentration paste solution mainly consisting of 100% by weight).

Hot melt adhesives are well known as cooling-setting adhesives that do not require heating operations when bonding corrugated boards.

However, the use of hot melt adhesives is not desirable in countries like Japan, where the rate of recovery and reuse of waste cardboard is extremely high, as it poses a major hindrance to the recovery and reuse of waste cardboard.

In addition, hot melt adhesives are petrochemical products, so
The fact that it will become increasingly difficult to obtain resources will also become a major problem in the future. In this regard, corn and corn starch made from it are
As seen in OhObi, corrugated cardboard adhesive is a resource that is attracting attention as a source of energy to replace oil in the future era of oil shortages, and is an adhesive material that causes fewer problems when recovering waste paper. It can be said to be an excellent resource as a material. Of the corn starch, which is an excellent resource as a raw material, the present invention uses three types of starch with significantly different characteristics: high amylose corn starch with an amylose content of 50% or more;
Based on the combination of ordinary corn starch and waxy corn starch within a specific range, a high-performance cooling-setting starch-based adhesive was obtained by effectively bringing out the characteristics of each of these. .

The Bahia Gulose corn starch used in the present invention is a starch produced from special corn that has been cultivated through breeding, and has a higher amylose content (more than 50%) compared to normal corn starch (approximately 25%). It is characterized by its existence.

High amylose corn starch has a high amylose content, so (a) it is difficult to gelatinize under normal conditions;
It has characteristics such as (b) high concentration paste can be prepared, (c) very easy to age, (d) strong film strength, and (e) high adhesive strength.

High amylose corn starch having such characteristics is extremely suitable as an adhesive material for achieving the object of the present invention.

That is, since the present invention aims to provide a starch-based adhesive that does not require heating operation when bonding corrugated cardboard and is solidified by cooling, (a) the size liquid reduces the amount of water evaporation; (1) It is necessary to have a high concentration for this reason, and (1) the adhesive has the ability to quickly gel because it is required to cause a setting phenomenon immediately after being applied to the bonding surface of the cardboard. etc., and high amylose corn starch can fully satisfy these conditions.

As described above, when a corrugated adhesive is produced using high amylose corn starch, which has many excellent properties, a starch-based adhesive with excellent cooling solidification properties can be obtained.

However, on the other hand, these excellent performances and features may also have drawbacks.

In corrugated board manufacturing, the lamination speed of a corrugator changes within a range of 0 m/min to 250 m/min depending on the size of the product rod, paper splicing, the start and end of operation, etc.

Therefore, the adhesive used must be one that does not affect the adhesion (lamination) even if the lamination speed changes, in other words, it must be one that can tolerate changes in the lamination speed. It won't happen.

Furthermore, the higher the speed of the corrugator, the wider its tolerance must be.

A cold-setting starch-based corrugated adhesive prepared using high amylose corn starch exhibits excellent lamination properties during high-speed lamination, but on the other hand, the aging rate and drying rate are too fast during low-speed lamination. Because of its low water retention capacity, it may solidify on the glue roll, or after being transferred to the top of the step, it dries or solidifies before the adhesion between it and the liner is complete. Therefore, adhesives prepared using high amylose corn starch alone have a narrow tolerance range for lamination properties as the lamination speed changes.

That is, with such properties, the rate of defective adhesion increases when corrugated cardboard is laminated at low speed. Therefore, the present inventors' problem was how to impart low-speed lamination suitability to a cold-setting starch-based corrugated adhesive using high-amylose corn starch having high-speed lamination suitability. In the process of researching this point, the present inventors found that when three types of starches with different properties were mixed to prepare a cold-setting starch-based corrugated adhesive, the properties would normally be averaged out. However, new findings have been obtained that in the adhesive of the present invention, each property remains without being lost.

That is, the present inventors have developed a cooling-setting property that combines the high-speed lamination suitability of adhesives prepared with high-amylose corn starch and the low-speed lamination suitability of adhesives prepared with ordinary corn starch and waxy corn starch. The company succeeded in producing a starch-based adhesive.

In the present invention, the mixing ratio of high amylose corn starch having an amylose content of 50% or more, normal corn starch, and waxy corn starch is 20 to 80% by weight of high amylose corn starch, 79 to 10% by weight of normal corn starch, and 79 to 10% by weight of normal corn starch, and 1% of waxy corn starch. The amount of corn starch is 1 to 10% by weight, and it is necessary to mix within this range so that the total amount is 100% by weight.

If the mixing ratio of high amylose corn starch is less than 20% by weight, the aforementioned high-speed lamination suitability will not be exhibited, while on the other hand, when the mixing ratio of ordinary corn starch is less than 20% by weight, the aforementioned low-speed lamination suitability will be exhibited. Not done. The greatest feature of the present invention is that the mixture of high-amylose corn starch and regular corn starch is further combined with waxy corn starch to further improve the adhesive performance during low-speed lamination without losing the suitability for high-speed lamination of corrugated cardboard. This is something that could have been improved.

Waxy corn starch is a starch that does not contain any amylose and is composed only of amylopectin, so it has high amylose properties such as (a) easy gelatinization, (b) strong stickiness, and (c) good water retention. It has properties that conflict with corn starch.

Therefore, when this waxy corn starch is added to a mixture of high amylose corn starch and regular corn starch, it supplements the water retention capacity of the starch glue solution during low-speed lamination, and the water retention capacity of the starch glue solution is supplemented during low-speed lamination, before solidification on the glue roll and completion of bonding the cardboard. Since drying and solidification are eliminated, the low-speed lamination suitability of the cooling-setting starch adhesive is further improved. In the present invention, the mixing ratio of waxy and corn starch is 1% by weight.
If it is less than 10% by weight, the adhesion performance improvement effect during low-speed lamination of corrugated board as described above cannot be sufficiently obtained, and if it is more than 10% by weight, the stringiness of the size solution increases and uniform roll application becomes impossible. will occur.

The method for preparing and using the cold-setting starch-based adhesive of the present invention involves adding water to a mixture of high amylose corn starch, regular corn starch, and waxy corn starch, and adding persulfate and peroxide, if necessary. Add and mix oxidizing agents such as borates, gelling promoters such as boric acid, borax, sulfites, pH adjusters such as caustic soda, etc., and use any heating method such as heating, autoclaving, on-radar, etc. A high-temperature, high-concentration glue solution with a temperature of about 80 to 100°C, a concentration of about 20 to 50% by weight, and a viscosity of about 500 to 1500 CPS is prepared using a shoe packing device. The starch paste solution is applied to the surface to be bonded, and immediately after bonding, the starch paste is allowed to cool or is forced to cool to complete the bonding process.This cooling causes the starch paste to rapidly solidify, creating strong adhesive strength.

The material for the cold-setting starch adhesive used in the method of the present invention includes not only high amylose corn starch having an amylose content of 50% or more, but also high amylose corn starch that has been oxidized, etherified, esterified, etc. according to known methods. Modified high amylose corn starch obtained by processing is also effective.

By subjecting high-amylose corn starch to oxidation, etherification, and esterification, not only does it become easier to gelatinize high-amylose corn starch, which is difficult to gelatinize, but it also becomes possible to prepare a homogeneous and stable sizing liquid.

In addition, when ordinary corn starch is subjected to treatments such as crosslinking and etherification according to known methods, the size liquid turns into a starch and water retention is improved, so that an adhesive with even better lamination properties can be obtained.

The cooling-setting starch adhesive of the present invention has the disadvantage of large shrinkage during solidification, but this disadvantage is similar to that of bentonite, clay, calcium carbonate, wood flour, walnut shell powder, perilla shell powder, etc. This problem can be solved by using a conventionally known inorganic or organic filler, and a stronger adhesive layer can be formed.

The cooling-setting starch adhesive of the present invention has both high-speed lamination suitability and low-speed lamination suitability, so it not only shows excellent adhesive performance during high-speed lamination as well as low-speed lamination, but also Strong adhesive strength can be obtained without the need for heating operations, which can significantly reduce thermal energy consumption in corrugated board factories, and also facilitate the recovery and reuse of waste paper, as is the case with hotmelt adhesives. It won't cause any major trouble.

The adhesive of the present invention exhibits particularly excellent effects when used as an adhesive for corrugated cardboard, but its use is not limited to adhesion of cardboard, but also paper, cloth, wood, plastic, inorganic materials, etc. Of course, it can be effectively used for bonding all kinds of materials.

Next, examples of the present invention will be shown.

Example 1 High amylose corn starch (amylose content 7
0%) 60 parts by weight, 35 parts by weight of regular corn starch and 5 parts by weight of waxy corn starch and 186 parts by weight of water.
After adding 2 parts by weight of sodium persulfate, 0.5 parts by weight of sodium sulfite, 2 parts by weight of boric acid, and 1 part by weight of caustic soda, the mixture was heated in a continuous gelatinization device (Sakura Manufacturing Co., Ltd.). It was gelatinized using a commercially available product (manufactured by OnRadar).

This paste solution was diluted with a 50% by weight aqueous caustic soda solution to pH 9.
．． The starch-based adhesive of the present invention was prepared by adjusting the temperature to about 90° C. and a high-temperature, high-concentration paste liquid having a concentration of about 33% by weight. Using this adhesive, lamination on the single side of the cardboard was carried out in two stages: low speed lamination (4 m/min) and high speed lamination (20 m/min) using a corrugator test machine.

In other words, a high-temperature, high-concentration size solution with a temperature of about 90℃ and a concentration of about 33% by weight is kept at about 90℃, and this size solution is poured onto the corrugated top of corrugated cardboard (core) for about 5 minutes (as dry matter). ), and after overlaying a craft liner for corrugated board on this, cold air was blown to cool and solidify the paste solution, thereby completing the pasting of the corrugated board.

The cardboard base paper is liner (manufactured by Honshu Paper Industries, K Liner 2)
80) and a core (manufactured by Honshu Paper Industries, SCP125) were used.

One side of the bonded cardboard was cut into a size of 8 (7 L x 5 CTIL), and the adhesive strength was measured using a compression tester according to JIS-2-0402.

Example 2 High amylose corn starch (amylose content 7
0%) 3509 was suspended in 400 ml of 40°C warm water, and adjusted to 11.5 with a 3% aqueous caustic soda solution, and then 28 ml of a 3-chloro2-hydroxypropyltrimethylammonium salt aqueous solution with a 50% concentration was added. Add and temperature 4
Stirring was continued for 4 hours at 0°C.

After that, after neutralizing the pH to 65 with hydrochloric acid, dehydration, washing with water,
It was dried to obtain positive high amylose corn starch.

60 parts by weight of this positive high amylose corn starch, commercially available etherified normal corn starch (Nippon Shokubai Chemical Co., Ltd., hydroxyethyl corn starch,
5-B) Using 35 parts by weight and 5 parts by weight of waxy and corn starch, a high-temperature, high-concentration paste solution with a temperature of about 90°C and a concentration of about 33% by weight was prepared in the same manner as in Example 1. A cooling solidified starch adhesive of the invention was obtained.

Using this adhesive, bonding of cardboard was completed in the same manner as in Example 1, and the adhesive strength of the cardboard was measured in the same manner as in Example 1.

Control Example 1 A high-temperature, high-concentration sizing solution was prepared in the same manner as in Example 1, except that ordinary corn starch (amylose content 24%) alone was used, and this sizing solution was used in the same manner as in Example 1. The pasting of the cardboard was completed.

The adhesive strength of the obtained cardboard was measured in the same manner as in Example 1.

Control example 2 High amylose corn starch (amylose content 7
A high-temperature, high-concentration starch solution was prepared in the same manner as in Example 1, except that 60 parts by weight of 0%) and 40 parts by weight of ordinary corn starch were used, and waxy corn starch was not used. The lamination of cardboard was completed in the same manner as in Example 1.

The adhesive strength of the obtained cardboard was measured in the same manner as in Example 1.

The measurement results for the above Examples and Control Examples are shown in the following table.

Claims (1)

[Scope of Claims] 1. High-amylose corn flour with an amylose content of 50% or more or processed starch thereof from 20 to 80% by weight
, ordinary corn starch or modified starch 79
~10% by weight and 1 to 1 waxy corn starch
A starch-based adhesive that hardens upon cooling, consisting of a high-temperature, high-concentration glue solution containing 0% by weight. 2. The cooling-setting starch adhesive according to claim 1, wherein the paste temperature is 80 to 100°C. 3. The cooling-setting starch adhesive according to claim 1 or 2, wherein the glue concentration is 20 to 50% by weight. 4 High amylose corn processed starch is oxidized,
The cooling-setting starch-based adhesive according to claim 1, 2, or 3, which is a starch that has been subjected to a processing treatment such as etherification or esterification to facilitate gelatinization. 5. Claims 1, 2, and 3, in which the processed ordinary corn starch is a starch that has been processed to change the viscosity or water retention of the size liquid, such as crosslinking or etherification.
The cooling-setting starch adhesive according to item 1 or 4. 6 Claims 1, 2, 3, 4, or 5 in which a filler such as bentonite, clay, calcium carbonate, wood flour, walnut shell powder, coconut shell powder, etc. is used in combination A starch-based adhesive that hardens when cooled. 7. The cooling-setting starch adhesive according to claim 1, 2, 3, 4, 5, or 6, wherein the adhesive is a corrugated cardboard adhesive.