JPS6121979B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a starch-based adhesive used in the manufacture of corrugated cardboard. More specifically, the present invention relates to a starch-based adhesive used in the manufacture of corrugated cardboard. More specifically, it is used to save energy in the corrugated cardboard manufacturing process, speed up the lamination of base paper, and improve the quality of the product. This invention relates to starch-based adhesives that have (Prior art) Starch-based adhesives commonly used in the manufacture of corrugated board have traditionally been manufactured using a glue manufacturing method called the stain hole method, in which an alkali-gelatinized starch paste called a carrier part and an ungelatinized starch paste called a main part are used. It consists of a mixture with a suspension of starch. The bonding mechanism of this adhesive is basically that by heating during the lamination process, the ungelatinized starch in the main part swells and becomes gelatinized to develop adhesive strength, and then the water is evaporated by heating and then dried. The goal is to achieve stronger adhesion. Therefore, when such an adhesive is used, the amount of thermal energy consumed in the bonding process is very large. In particular, in the corrugated board bonding process known as double facer, heating the glue applied to the top of one tier must be done through a liner, so a huge amount of heat is spent just heating the liner.
In this state, only a small amount of the added heat serves to gelatinize the main starch.
Furthermore, when producing double-sided corrugated board, heating is required through one stage, so heat loss becomes significant. Therefore, with such adhesives, the heat conduction rate decreases due to indirect heating through the medium,
The lamination speed is also slower, and the production speed of corrugated board is limited to 1/2 to 2/3 of the maximum machine speed. On the other hand, with such adhesives, expansion and contraction of the paper due to the applied heat and water cannot be avoided, so there are manufacturing disadvantages such as warping of the corrugated paperboard sheet. In the corrugated board industry, there has been a strong desire to solve the above-mentioned problems due to the energy crisis that followed the oil shock crisis, and the development of energy-saving adhesives that can be bonded without the need for heating has become a major issue. In recent years, from the perspective of energy conservation, a method called the cold corrugation system, which forms corrugated cardboard without using heat, and a starch-based adhesive that does not require heating during the lamination process (see U.S. Pat. No. 3,300,360) have been developed. ) was developed. A feature of this starch-based adhesive is that it consists of a homogeneous starch paste that does not contain ungelatinized starch. The adhesion mechanism of this starch-based adhesive is to apply the adhesive maintained at high temperature and low viscosity to the corrugated top of the core base paper at room temperature, and to dry the liner base paper at the same time as the adhesive increases in viscosity due to natural cooling. It is to bond and fix.
Therefore, if this starch-based adhesive is used for manufacturing corrugated boards, heating can be completely omitted in the process of laminating corrugated boards. However, this adhesive has a very slow setting speed, and not only is it difficult to obtain a sufficient lamination speed, but when laminating the double facer side, it passes through a slitter and scorer, so the adhesive force cannot withstand the impact and it peels off. However, it has not yet reached the stage of practical use. (Objective of the Invention) The present inventors have overcome the current state of adhesives for manufacturing corrugated board as described above, and aim to significantly reduce the amount of heat required in the manufacturing process of corrugated board and improve the bonding properties of double facer. The present invention was completed with the aim of obtaining a starch-based adhesive for corrugated board manufacturing that has excellent setting properties, provides adequate lamination speed and corrugated sheet quality. (Structure of the Invention) Acid-treated corn having an amylose content of 35% by weight or more, a starch concentration of 30% by weight, and a pH of 12, in which the viscosity at 95°C of an aqueous suspension is 50 to 2000 Brabender units. An adhesive whose active ingredient is a steamed processed starch obtained by etherifying or esterifying starch, with a concentration of 20 to 50% by weight and a viscosity of 50 to 2000 Brabender units at a temperature of 85°C. This is a cold-set adhesive for corrugated board manufacturing, which is characterized by having the property of solidifying at room temperature and containing no ungelatinized starch. ((Starch)) The starch used in the present invention has an amylose content of 35% by weight.
The above high amylose corn starch can be used. High-amylose corn starch contains a large amount of linear molecules (amylose) that make up starch granules, so high amylose corn starch contains a lot of linear molecules (amylose) that make up starch granules.
25%), it ages extremely easily, has strong film strength, and has strong adhesive strength. High amylose corn starch having such properties is extremely suitable as a raw material for the adhesive of the present invention. ((Acid treatment)) The present invention provides a starch-based adhesive that does not require heating during corrugated board manufacturing and has excellent setting properties. In addition, it is required that the setting phenomenon occurs rapidly after being applied to the bonding surface of the corrugated board. Furthermore, in the production of corrugated board, a double facer is used to apply a slitter scorer, so the setting properties of the adhesive play a very important role. Therefore, acid-treated high amylose corn starch, which has been treated to reduce the viscosity in order to increase the concentration and maintain the fluidity of the size liquid, is considered to be a suitable raw material in the present invention because it sets rapidly. Acid-treated high amylose corn starch, which is a raw material in the present invention, is obtained by treating high amylose corn starch with mineral acids such as hydrochloric acid and sulfuric acid, or organic acids such as oxalic acid and acetic acid, and has a starch concentration of 30% by weight (25% caustic soda). (adjusted to PH12) 1.5 from 25℃
Temperature increase at °C/min, Brabender viscosity at 95 °C is 50
Starch of ~2000 B.U. is suitable. If the viscosity of the acid-treated starch exceeds 2000 B.U., aging will be high and fluidity will be lost, which is not preferable. When the viscosity is lower than 50 B.U., although aging is reduced, the starch becomes amylodextrin, whitens, becomes brittle when dried, has weak adhesive strength, and has poor moisture resistance. ((Esterification/Etherification)) As mentioned above, high amylose corn starch contains a lot of amylose, a linear molecule.
Generally speaking, starch is extremely susceptible to rearrangement of linear molecules, that is, retrogradation. This aging depends on concentration and temperature, so even if high-amylose corn starch is treated with acid to reduce its viscosity for the purpose of making a high-concentration size liquid adhesive like the one of the present invention, aging will be large and the size liquid life will be very short. There is a disadvantage. The present inventors esterified or etherified acid-treated high amylose corn starch,
We have discovered that by introducing a substituent, it is possible to moderately suppress the aging of acid-treated high amylose corn starch, and to produce a starch-based adhesive that has a long glue life and excellent setting properties that allow for long open times. Ta. The starch used in the present invention has a viscosity of 50B according to a specified measurement method.
Esters obtained by reacting acid-treated high amylose corn starch of U. to 2000 B.U. (BU stands for Brabender Unit) with organic acids such as acetic acid, propionic acid, butyric acid, succinic acid, maleic acid, and phthalic acid. Hydroxymethyl, hydroxyethyl, hydroxypropyl, carboxymethyl, carboxyethyl, 2-
These are etherified starches such as aminoethyl ether, primary amine ether, tertiary aminoalkyl ether, and quaternary ammonium alkyl ether.
Furthermore, acid-treated high amylose corn starch crosslinked with a crosslinking agent such as trimetaphosphoric acid or epichlorohydrin can also be used. These starches preferably have a concentration of 20 to 50% by weight and a paste viscosity of 50 to 2000 B.U., preferably 100 to 1000 B.U., at a temperature of 85°C.
U. Esterified/etherified starch with a degree of substitution of 0.01 to 0.7. When the degree of substitution is 0.01 or less, the number of substituents introduced is small and is not sufficient to suppress aging. Also 0.7
If the content is higher than that, the substitution becomes highly substituted, presumably to prevent entanglement of linear molecules, but aging is suppressed too much, resulting in poor setting properties. ((Preparation of Adhesive)) The method for preparing the starch-based adhesive of the present invention involves dispersing the esterified or etherified starch of the acid-treated high amylose corn starch in water to obtain a starch concentration of 20 to 50% by weight. any method of heating the suspension;
For example, glue can be cooked using a direct heating method using steam blowing, such as in a jet cooker, or an indirect heating method using a jacket, such as a high-pressure cooker.
The viscosity at a starch concentration of 20-50% by weight and a temperature of 85℃ is
A high temperature, high concentration paste solution of 50 B.U. to 2000 B.U., preferably 100 to 1000 B.U. is prepared. In the present invention, if necessary, an alkali such as caustic soda may be added to adjust the pH in order to further strengthen the adhesive properties of starch.
However, if the pH is higher than 11.0, the alkali will cause deterioration, so care must be taken. Furthermore, gelation accelerators such as borax and boric acid can also be used together. In addition, to reduce glue costs, clay,
Fillers such as bentonite, calcium carbonate, etc. can also be added. ((Concentration and Viscosity of Adhesive)) The starch concentration in the starch adhesive of the present invention is preferably 20 to 50% by weight. This is because this adhesive applies a homogeneous paste liquid that has been steamed to a paste onto the bonding surface and adheres without heating, so water dissipation and instantaneous solidification are essential conditions. This is because a highly concentrated paste solution is required. When gluing the single facer side of corrugated board, the nip pressure from the corrugating rolls and press rolls works effectively, so a glue concentration of 20% by weight can be sufficient for bonding, but when gluing the double facer side Since there is no pressing effect and the starch concentration is increased, water dissipation and solidification are faster, so the lamination speed can be increased, which is advantageous in production. However, if the concentration exceeds 50% by weight, the viscosity has an upper limit and the starch must be further reduced in molecular weight, resulting in brittleness when dried, weak adhesive strength, and poor moisture resistance. As described above, the starch concentration of the adhesive of the present invention is adjusted to 20 to 50% by weight as necessary. The viscosity of the produced adhesive is adjusted to have a Brabender viscosity of 50 to 2000 B.U., preferably 100 to 1000 B.U., at a measurement temperature of 85°C. Naturally, the adhesive viscosity has a relative relationship with the starch concentration during cooking, acid treatment, and ether esterification, and in order to obtain the designed adhesive viscosity, various conditions for production may be appropriately selected. (How to use the adhesive) With this adhesive, the adhesive is maintained at a specified temperature and applied to the bonding surface of the cardboard, and the liner and core base paper are completely bonded by natural cooling and concentration of the size liquid. By this cooling and concentration, the starch paste solution rapidly solidifies and produces strong adhesive strength. Furthermore, the coating temperature is
In order to improve wetting and permeability and to maintain the usable viscosity, the temperature is preferably 70°C to 95°C in consideration of workability. In addition, when laminating, the moisture content of the base paper used also affects lamination suitability, and the lamination speed and setting properties can be improved by keeping the moisture content of the base paper low and using the adhesive of the present invention, as a synergistic effect appears. However, the present invention is further improved. Preferably, the moisture content of the base paper is 4% or less. (Examples) In order to make the present invention easier to understand, Examples and Comparative Examples will be shown and specifically explained below, but the following Examples do not limit the present invention in any way. Example 1 Acid-treated high amylose corn starch (starch concentration 30% by weight (adjusted to PH12) Brabender viscosity 220 B.U. at 1.5°C/min temperature increase at 95°C) 450 kg at 25°C
Dispersed in 680 g of water, adjusted to pH 8.0 with 3% caustic soda, added 190 kg of acetic anhydride, continued stirring for 1 hour, then neutralized to pH 5.0 with hydrochloric acid, dehydrated, washed with water, dried and replaced. Starch acetate with a degree (DS) of 0.4 was obtained. This acetic acid starch is dispersed in water to determine the starch concentration.
A 35% by weight suspension was prepared, and this suspension was heated at 140°C in an indirect heating continuous gelatinization device to obtain an adhesive with a total solid content of 35% by weight. The viscosity of this adhesive is Brabender viscosity of 250B at a temperature of 85℃.
It was U. Example of use 1 Use this adhesive to attach single-sided corrugated cardboard (B-220
×SCP125) and liner (B-220) were bonded together to produce double-sided corrugated board, and the bonding was possible at a speed of 130 m/min. Example 2 The acid-treated high amylose corn starch of Example 1 is dispersed in water to prepare a 38% by weight suspension. Add to this suspension 4% sodium chloride to starch and 0.85% caustic soda to starch (in a 3% aqueous solution).
was added, and propylene oxide with a ratio of 12% to starch was added, and the mixture was reacted for 5 hours in a closed reaction vessel at a reaction temperature of 45°C. After neutralization to pH 6.0 with concentrated hydrochloric acid, washing with water, dehydration,
After drying, hydroxypropyl starch with a degree of substitution of 0.25 was obtained. This hydroxypropyl starch was boiled into a paste using an indirect heating continuous gelatinization device in the same manner as in Example 1, and the percentage was reduced to 25%.
Adjusted to pH 8.5 with caustic soda, total solids content 35% by weight, Brabender viscosity 240 B.U. at 85°C.
of adhesive was obtained. Usage example 2 In the same way as usage example 1, double-sided cardboard was manufactured using a double facer that does not allow any heat to pass through.
Lamination was possible at a speed of m/min. Control Example 1 The acid-treated high amylose corn starch of Example 1 was cooked in an indirect heating continuous gelatinizer and adjusted to pH 8.8 with 25% caustic soda, and the total solid content was 35% by weight.
An adhesive with a Brabender viscosity of 280 B.U. was obtained at a temperature of 85°C. Using this adhesive, a double-sided corrugated board was produced using a double facer in the same manner as in Use Example 1, but the size solution gelled and could not be bonded. These results are shown in Table-1. Control example 2 450 kg of high amylose corn starch (amylose content 70%) was dissolved in 40°C warm water 650, and while adjusting the pH to 11.0 with a 3% aqueous solution of caustic soda, added sodium hypochlorite 135 with 13% available chlorine. and continue stirring at 40℃ for 4 hours, then adjust the pH with hydrochloric acid.
After neutralizing to 5.0, oxidized high amylose corn starch was obtained by washing with water, dehydrating, and drying. This oxidized high amylose corn starch was cooked in an indirect heating continuous gelatinization device in the same manner as in Example 1, with a pH of 8.0, a solid content of 34% by weight, and a Brabender viscosity.
Obtained 210 B.U. of adhesive. Example of using this adhesive 1
Double-sided corrugated cardboard was produced using double facer in the same manner as above. Lamination was possible at a speed of 90 m/min, and if the speed was increased beyond this, peeling occurred at the cutter tip. These results are shown in Table-1.

[Table] Example 3 Using the hydroxypropyl starch of Example 2, 23 parts by weight of starch, 22 parts by weight of clay, 55 parts by weight of water, borax
A suspension having a composition of 0.46 parts by weight was prepared in the same manner as in Example 1, and the pH was adjusted to 9.9 with a 30% aqueous solution of caustic soda.The total solid content was approximately 45% by weight, and the Brabender viscosity was adjusted to 9.9.
Obtained 620B.U. of adhesive. Usage Example 3 Using this adhesive, double-sided corrugated cardboard was manufactured using a double facer that does not transmit any heat in the same manner as in Usage Example 1, and the adhesive could be bonded at a speed of 135 m/min. Example 4 A suspension of the hydroxypropyl starch of Example 2 with a concentration of 33% by weight was prepared, borax was added thereto at a concentration of 2% by weight of the starch, and the paste was cooked in the same manner as in Example 1.
The pH was adjusted to 10.0 with a 25% by weight aqueous solution of caustic soda to obtain an adhesive with a total solids content of about 31% by weight and a Brabender viscosity of 340 B.U. at 85°C. Usage Example 4 When double-sided corrugated board was manufactured using this adhesive in the same manner as in Example 1, it was possible to bond the sheets together at a speed of 130 m/min.

[Table] (Effects of the Invention) The starch-based adhesive of the present invention could be laminated without heating operations, a lamination speed that was practical could be obtained, and adhesive strength was sufficient. Furthermore, due to no heating and high solidification of the size liquid, high quality corrugated cardboard sheets can be produced without the problem of warping caused by heat and water.

Claims (1)

[Claims] 1. An aqueous suspension having an amylose content of 35% by weight or more, a starch concentration of 30% by weight, and a pH of 12 at 95°C.
An adhesive whose active ingredient is a processed starch obtained by etherifying or esterifying acid-treated corn starch and having a viscosity of 50 to 2000 Brabender Units at a temperature of 20 to 50% by weight. A cold-set adhesive for corrugated board manufacturing, which has a viscosity of 50 to 2000 Brabender units at 85°C, solidifies at room temperature, and does not contain ungelatinized starch. 2 Degree of substitution for esterification or etherification is 0.01
The adhesive according to claim 1, which has a molecular weight of ˜0.7.