JPS6131154B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an adhesive for manufacturing corrugated board. More specifically, the present invention relates to an adhesive that does not require heating when bonding base paper for corrugated board. (Prior art) Starch-based adhesives that are generally used in the production of corrugated board are manufactured by a glue manufacturing method called the stain hole method, which consists of an alkali gelatinized starch paste called a carrier part and an ungelatinized starch paste called a main part. It consists of a mixture with a suspension of gelatinized 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 by heating, water is evaporated. The purpose is to complete strong adhesion by drying. 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 called double facer, in order to heat the glue applied to the top of one tier, it must be passed through the liner, so a huge amount of heat is spent just heating the liner, and the added heat is Only a small amount of the starch serves to gelatinize the main starch. In addition, when manufacturing multi-sided corrugated board,
Furthermore, since heating is performed through one stage, heat loss becomes significant. Therefore, with such adhesives, the heat conduction rate is reduced due to indirect heating through the medium, and the lamination speed is also slow, and the production speed of corrugated board is limited to 1/2 to 2/3 of the maximum machine speed. has been done. 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 following 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 a cold corrugation system, in which a corrugated corrugated board is formed without using heat, and a starch-based adhesive that does not require heating during the lamination process (US 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 at a high temperature and low viscosity to the corrugated top of the corrugated core paper at room temperature, and then dry it at the same time as the adhesive increases in viscosity due to forced cooling or natural cooling. The process involves bonding and fixing the liner base paper. Therefore, if this starch-based adhesive is used for manufacturing corrugated board, heating can be completely omitted in the corrugated board bonding process. However, this adhesive has a very slow setting speed, making it impossible to obtain a sufficient lamination speed, and when laminating the double facer side, the adhesive force cannot withstand the impact of passing through a slitter scorer. However, it has peeled off and has not yet reached the stage of practical use. (Purpose of the Invention) The present inventors have aimed to overcome the current state of adhesives for manufacturing corrugated board as described above, and to significantly reduce the amount of heat required in the manufacturing process of corrugated board and improve the bonding properties of double facer. As a result of extensive research, we have found that the presence of metaborates in adhesives significantly improves the adhesive's setting properties based on its tackiness, significantly increases its resistance to sudden impact forces, and reduces lifting of ruled lines and slitters. It has been discovered that an adhesive for manufacturing corrugated board can be obtained which has significantly improved peeling and is fully satisfactory in terms of lamination speed and corrugated sheet quality, and has completed the present invention based on this knowledge. (Structure of the Invention) The present invention provides the following features: (1) At least one compound selected from the group consisting of orthoboric acid, borax, and metaborate is added to starch with a reduced viscosity or modified starch with a reduced viscosity at a rate of 0.1% per starch. or 4% by weight
The mixture is then boiled and the pH is adjusted to 9.5 to 11.0 with sodium hydroxide or potassium hydroxide, and the amount of metaborate present is adjusted to 0.01 to 0.65 mol/Kg starch. (2) A corrugated board manufacturing adhesive having the property of solidifying at room temperature and containing no ungelatinized starch; and (2) a starch or modified starch selected from the group consisting of orthoboric acid, borax and metaborate. At least one boron compound is added in an amount of 0.1 to 4% by weight based on starch and an oxidizing agent or acid treatment agent, and the mixture is boiled and then boiled with sodium hydroxide or potassium hydroxide.
Adjust the pH to 9.5 to 11.0, and at this time, the amount of metaborate present is 0.01 to 0.65 mol/
This is an adhesive for manufacturing corrugated board that has the property of solidifying at room temperature and does not contain ungelatinized starch, and is adjusted to give Kg starch. Components of the present invention will be explained in detail below. <Starch> The starches used in the present invention include ground starches such as corn starch, wheat starch, and rice starch, and potato starch.
These are underground starches such as tapioca starch and sweet potato starch, high amylose starch, and processed starches thereof. Starch is composed of a linear molecule called amylose and a branched molecule called amylopectin, but amylose has the property of being extremely susceptible to aging due to molecular rearrangement in the paste due to its molecular structure. However, due to its branched structure, amylopectin has the property of being extremely resistant to aging. Therefore, ordinary starch with an amylose content of about 20 to 27% contains a large amount of branched molecules (amylopectin), and therefore has the drawbacks of poor retrogradability and low setting properties. Furthermore, as the viscosity-lowering treatment progresses, high amylose starch with a high amylose content also becomes amylodextrin, resulting in a decrease in setting properties. In particular, when laminating the double facer side in the corrugated board manufacturing process, it passes through a slitter scorer.
Settability plays a very important role. Furthermore, in the manufacturing process of corrugated board, starch-based adhesives that do not require heating operations play an important role in setting properties based on the aging of starch.
The setting property based on the tack (stickiness) of starch also plays an important role and cannot be ignored. In particular, in cases where the aging resistance is poor, the setting performance by tack is largely relied upon. However, the adhesiveness of starch paste liquid is very weak, and it is not in a condition to adhere corrugated cardboard base paper at a practical lamination speed. Therefore, for adhesives with low aging properties, strengthening the adhesive strength greatly improves the setting. Furthermore, even in adhesives that use high amylose starch containing a large amount of amylose and modified starches that are highly resistant to aging, strengthening the adhesive strength further greatly improves the setting properties. <Need for lower viscosity> The purpose of the present invention is to develop a starch-based adhesive that adheres a corrugated core and a liner without applying heating during corrugated board manufacturing. In addition to being required to have a high concentration in order to reduce the burden of water dissipation, it is also required to cause rapid settling after application to the surface to be bonded to the corrugated board. In order to satisfy these requirements, the sizing liquid must have fluidity to achieve uniform sizing, and since there is an upper limit to the viscosity that can be used, the starch must be treated to reduce its viscosity and increase its concentration. The present invention includes a method for obtaining a high-temperature size liquid starch-based adhesive by pre-processing starch to lower its viscosity and then cooking the starch, and a method for obtaining a high-temperature size liquid starch-based adhesive by adding an oxidizing agent and an acid treatment agent at the time of starch cooking. There is a way to get it. Even if starch that has been subjected to viscosity reduction treatment is used or an oxidizing agent or acid treatment agent is added during steaming to reduce the viscosity, the effect of the present invention will not change at all, and either method can be selected as appropriate. . <Starch Concentration> The starch concentration in the high-temperature size liquid 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, so it is highly concentrated. It is required to be a paste. When gluing the single facer side of corrugated board, the nip pressure from the corrugating rolls and press rolls works effectively, so a 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 higher, 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 starch must be made to have a lower molecular weight, which causes the starch to become brittle when dried, resulting in weak adhesive strength and poor moisture resistance. As mentioned above, the starch concentration of the adhesive of this invention is 20 to 20% as necessary.
Adjust to 50% by weight. The effect will be even better if you use not only regular starch, but also high amylose starch, which has excellent setting properties. <Viscosity of Adhesive> The viscosity of the adhesive of the present invention is adjusted to a Brabender viscosity of 50 to 2000 B.U (abbreviation of Brabender Unit), preferably 100 to 1000 B.U, at a measurement temperature of 85°C. Naturally, the adhesive viscosity is in a relative relationship with the starch concentration during glue cooking, the amount of orthoboric acid, borax, and metaborate added, and the pH.In order to obtain the designed adhesive viscosity, various manufacturing conditions must be met. should be selected appropriately. <Effect of metaborate> Orthoboric acid and borax are generally used as tackifiers for starch, but these tackifiers are thought to chemically react with starch to form a crosslinked structure and develop tackiness. ing. However, according to the findings of the present inventors, the tackifying effect of orthoboric acid and borax on starch-based adhesives with poor aging properties is very weak, and they improve the tackiness of the size liquid and improve the setting property. I didn't have time to do that. However, if sodium hydroxide, potassium hydroxide, etc. are added to the size solution containing orthoboric acid and borax to adjust the pH to 9.5 or higher, the adhesive strength is significantly improved and the setting property is improved. Furthermore, it has been found that even in adhesives that use high amylose starches with a high amylose content and modified starches that are highly susceptible to aging, the setting properties can be greatly improved by strengthening the adhesive strength. It is assumed that orthoboric acid and sodium hydroxide produce sodium metaborate as shown in equation (1) below, and that borax and sodium hydroxide produce sodium metaborate as shown in equation (2) below. Ru. (1) H ₃ BO ₃ +NaOH→NaBO ₂ +2H ₂ O (2) Na ₂ B ₄ O ₇ +2NaOH→4NaBO ₂ +H ₂ O And because the above metaborate forms a complex with starch and takes a cross-linked structure It is believed that this significantly improves the adhesiveness of the glue. The amount of orthoboric acid and borax added is 0.1 to starch.
4% by weight, preferably 0.5-3% by weight is suitable. Furthermore, when the pH was adjusted to 9.5-11.0 with sodium hydroxide, potassium hydroxide, etc., the amount of metaborate present was 0.01-0.65 mol/Kg-starch, especially
A range of 0.05 to 0.5 mol/Kg of starch seems preferred. When the amount of orthoboric acid or borax added exceeds 4% by weight, the adhesive becomes strong and stringiness becomes strong, and when the size solution is transferred to the bonding surface, spider web-like threads are pulled. However, the workability is deteriorated and the amount of adhesive consumed is increased, which is economically disadvantageous. Therefore, it is preferably 3% by weight or less. Furthermore, if the amount added is less than 0.1% by weight, there is a drawback that the effect is not sufficiently exhibited. As mentioned above, when the pH is below 9.5, the adhesive strength is not sufficiently developed. Furthermore, if the pH exceeds 11.0, not only will starch deteriorate due to browning, but it will also lead to excessive alkali content and the crosslinked structure created by the metaborate complex will be destroyed.
This is undesirable because borates such as Na ₂ HBO ₃ and Na ₃ BO ₃ are likely to be formed, resulting in a decrease in adhesive strength and viscosity. In addition, the present invention also provides PH
Since the amount of metaborate produced can be controlled by adjusting , the tackiness can also be controlled. That is, it can be controlled by creating a coexisting system of orthoboric acid, borax, and metaborate. Metaborate PH9.5-11.0, 0.01-0.65 mol/
It may be added within the kg-starch range. Furthermore, orthoboric acid, borax, and metaboric acid may be used in combination so as to satisfy the above-mentioned conditions. Further, orthoboric acid, borax, and metaborate may be added before or after addition. As is clear from Table 1 and Comparative Example 2, even though borax is added and the pH is alkaline at 8.5, adhesive strength will not develop unless metaborate is generated. This is insufficient, and the lamination speed is extremely reduced compared to other examples. <Optional Components> In the present invention, fillers such as clay, bentonite, and calcium carbonate may be added as fillers as necessary. (How to use the adhesive) The starch-based adhesive of the present invention is produced by applying the adhesive maintained at a predetermined temperature to the bonding surface of corrugated cardboard, and the adhesive strength rapidly increases due to natural cooling and concentration of the adhesive. This completes the adhesion of the raised liner and core base paper. Further, the coating temperature is preferably 70° C. to 90° C. in order to improve wetting and permeability to the paper surface and maintain the usable viscosity, and in consideration of workability. When laminating, the moisture content of the base paper used also affects lamination suitability. The lamination setting property is further improved by using the starch-based adhesive of the present invention while keeping the moisture content of the base paper low, as a synergistic effect appears and the lamination strength is improved. Preferably, the moisture content of the base paper is 4% or less. (Examples) In order to make it easier to understand the present invention, Examples and Comparative Examples will be shown and specifically explained below, but the following Examples are not intended to limit the present invention in any way. Example 1 A cornstarch slurry with a concentration of 35% was prepared,
Sodium hypochlorite was added as available chlorine at 7% relative to starch, the pH was adjusted to 10.7, and the reaction was carried out at 40°C for 5 hours. This was washed with water, dehydrated, and dried to obtain oxidized starch. This oxidized starch was dispersed in water, and 2% borax was added to the starch to prepare a suspension having a concentration of 37%. This suspension was gelatinized at 140°C using an indirect heating continuous gelatinization device, and the pH of this paste was adjusted using caustic soda at a concentration of 25%.
9.8 to obtain an adhesive with a total solid content of 37% by weight. The viscosity of this adhesive was a Brabender viscosity of 340 B.U at a temperature of 85°C. Usage example 1 Using this adhesive, one-sided cardboard <B-220× with an actual double facer that does not allow steam to pass through
SCP-125> and liner (B-220) were bonded together to produce a double-sided corrugated board, and the bonding was possible at a speed of 110 m/min. Example 2 The same process as in Example 1 was carried out except that potato starch was used instead of the cornstarch in Example 1 and the pH was adjusted to 10.2. Got the glue. Usage example 2: Using this adhesive to manufacture double-sided corrugated board with a double facer in the same way as usage example 1, the length of 100m/
I was able to attach it in minutes. Example 3 Hydroxypropyl starch (degree of substitution 0.10) was dispersed in water to prepare a 35% suspension, and 35% hydrochloric acid was added at a ratio of 8% to the starch and reacted at 53°C for 7 hours. This was neutralized, washed with water, dehydrated, and dried to obtain acid-treated hydroxypropyl starch. Disperse this starch in water,
Add 2% orthoboric acid to starch to prepare a suspension with a concentration of 30% by weight, and then process in the same manner as in Example 1.
An adhesive with a pH of 10.0, a total solid content of 30% by weight, and a Brabender viscosity of 200 B.U at a temperature of 85°C was obtained. Usage Example 3 Using this adhesive, double-sided corrugated cardboard was manufactured using a double facer in the same way as Usage Example 1.130
Lamination was possible at a speed of m/min. Example 4 450 kg of high amylose corn starch (amylose content 70%) was dissolved in 650 kg of warm water at 40°C, the pH was adjusted to 11.0 with a 3% aqueous solution of caustic soda, and 140 kg of a sodium hypochlorite aqueous solution containing 13% available chlorine was added. and continued stirring at a temperature of 40°C for 4 hours, then diluted with hydrochloric acid.
After neutralizing to pH 5.0, the mixture was washed with water, dehydrated, and dried to obtain oxidized high amylose corn starch. The viscosity of this oxidized high amylose corn starch is 95°C at a temperature increase rate of 1.5°C/min from 25°C at a starch concentration of 30% by weight (adjusted to PH12 with 25% caustic soda aqueous solution).
The Brabender viscosity was 350 B.U. This oxidized high-amylose corn starch was dispersed in water to prepare a suspension with a starch concentration of 33% by weight, and borax was added at a starch concentration of 2% by weight, and this suspension was heated in an indirect heating continuous gelatinization device. Gelatinize at 140℃, and PHize the paste with a 25% caustic soda aqueous solution.
was adjusted to 10.5 to obtain an adhesive with a total solid content of 32% by weight and a Brabender viscosity of 330 B.U at a temperature of 85°C. Usage Example 4 Using this adhesive, double-sided corrugated cardboard was manufactured using a double facer in the same way as Usage Example 1.
Lamination was possible at a speed of m/min. Example 5 The same process as in Example 4 was carried out except that 0.5% by weight of starch was added with sodium metaborate instead of the borax used in Example 4, and the total solid content was 32.5% by weight and the Brabender viscosity at a temperature of 85°C was 250B. Got U glue. Usage example 5 When double-sided corrugated board was manufactured using double facer using this adhesive in the same manner as usage example 1, 135
Lamination was possible at a speed of m/min. Example 6 The acid-treated hydroxypropyl starch of Example 3 was treated in the same manner as in Example 3, except that 3% by weight of sodium metaborate was added, and the total solid content was 30% by weight and Brabender viscosity at a temperature of 85°C. but,
Obtained 260B.U of adhesive. Usage example 6 Using this adhesive, double-sided corrugated cardboard was manufactured using a double facer in the same way as usage example 1.135
Lamination was possible at a speed of m/min. Example 7 Oxalic acid was added to a cornstarch suspension with a concentration of 35% by weight at a ratio of 0.2% to starch, and the mixture was gelatinized at 1550°C in a direct heating continuous gelatinization device using steam injection, simultaneously lowering the viscosity, and then continuing. Borax was added in an amount of 2% by weight relative to starch, and then sodium hydroxide was added to adjust the pH to 9.8 to obtain an adhesive with a total solid content of 30%. The viscosity of this adhesive was Brabender viscosity 560 B.U at a temperature of 85°C. Usage Example 7 Using the adhesive of Example 7, as in Usage Example 1,
When double-sided corrugated cardboard was manufactured using a double facer, it was possible to bond the sheets together at a speed of 100 m/min. The results of this usage example are as follows. Paste concentration 31% Viscosity 560B.U. Lamination speed 100m/min Adhesive strength 25Kg/40cm ^2Glue amount 9.1g/m ^2Metaboric acid 0.1mol/Kg-starch PH 9.8 Control example 1 Except for the borax of Example 1 Except for the above, the same treatment as in Example 1 was carried out, and the same operations as in Use Example 1 were performed. Control Example 2 The same treatment as in Example 1 was carried out, and the same operations as in Use Example 1 were performed, except that the pH of Example 1 was adjusted to 8.5. These results are specified in Table 1.

[Table] (Effects of the Invention) According to the present invention, there is no need for heating in the corrugated board manufacturing process, which not only saves energy, but also allows the lamination speed to be sufficiently fast, resulting in improved productivity. Further, due to no heating and high solidification, high quality corrugated cardboard sheets can be produced without the problem of warping caused by heat and water.

Claims (1)

[Scope of Claims] 1 Addition of at least one compound selected from the group consisting of orthoboric acid, borax, and metaborate to starch with reduced viscosity or modified starch with reduced viscosity in an amount of 0.1 to 4% by weight based on the starch. The mixture is then boiled and the pH is adjusted to 9.5 to 11.0 with sodium hydroxide or potassium hydroxide.
and furthermore, at this time, the amount of metaborate present is adjusted to be 0.01 to 0.65 mol/Kg starch.For the production of corrugated board, which has the property of solidifying at room temperature and does not contain ungelatinized starch. glue. 2 At least one boron compound selected from the group consisting of orthoboric acid, borax and metaborate is added to starch or modified starch in an amount of 0.1 to 4% by weight based on the starch, and an oxidizing agent or acid treatment agent is added, and the mixture is Room temperature, which is characterized by steaming, then adjusting the pH to 9.5 to 11.0 with sodium hydroxide or potassium hydroxide, and adjusting the amount of metaborate at this time to 0.01 to 0.65 mol/Kg starch. An adhesive for manufacturing corrugated board that has the property of solidifying with water and does not contain ungelatinized starch.