JPH07331202A - Paste-making method for starch adhesive for corrugated board - Google Patents

Abstract

PURPOSE:To obtain a starch adhesive for corrugated boards simplified in the paste-making process therefor, improved in both fluidity and initial adhesion also suitable for high-speed laminating. CONSTITUTION:An excess amount of an alkali is added to an aqueous suspension of starch to bring the starch to a partially swollen state followed by addition of boric acid (and borax) to stop the swelling to obtain an adhesive for corrugated boards having a moderate viscosity. In this paste-making method with noncarrier technique including the above process, both the partial swelling and its termination processes are conducted while applying shear force by an agitating means having a circumferential speed of >=500m/min. In this method, a starch composition blended with a small amount of a kind of subordinate starch with the gelatinization beginning temperature determined by alkali amylograph >=5 deg.C lower than raw starch is preferably used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for making a starch-based adhesive paste used for producing corrugated board. More specifically, the present invention relates to a paste making method for a starch adhesive for corrugated board, which is characterized in that a strong stirring means accompanied by mechanical shearing force is used in the paste making of no carrier method.

[0002]

2. Description of the Related Art Conventionally, a starch adhesive used in the manufacture of corrugated board is generally composed of a mixture of an alkali gelatinized starch paste solution called a carrier part and a suspension of ungelatinized starch called a main part. This adhesive is manufactured by a sizing method called a stain hole method. In this pasting method, the main part and the carrier part are prepared separately, and the method of mixing both is adopted, so the manufacturing process is complicated, and the viscosity of the adhesive itself tends to vary, and a stable adhesive is obtained. There is a drawback that it requires skill.

In order to eliminate such complicated operations and obtain an adhesive having stable quality, a gluing method called a no carrier method has been proposed. The no-carrier method is a method in which the entire starch is partially swollen with an alkali to give it an appropriate viscosity.Comparing with the stain-hole method, the paste making is easier and it is more resistant to mechanical shearing and temperature change. It is also superior to the stain hole method in viscosity stability,
There are problems in water retention and fluidity, and initial adhesiveness and suitability for high-speed laminating are not enough.

As an improved method of the no-carrier method, cold water-soluble pregelatinized starch is premixed with raw starch, and an alkali is added to this to dissolve the pregelatinized starch while the raw starch is dissolved. A method of partially swelling is known. The starch obtained by this improvement method has a good balance of viscosity stability and fluidity. Also, the initial adhesiveness is considerably improved as compared with the normal no-carrier method. However, depending on the solubility of the pregelatinized starch, there are problems such that the viscosity stability is deteriorated, and mamako tends to occur when the starch is dissolved.

For the purpose of solving these problems of the no-carrier method, an improved method for producing pregelatinized starch has been proposed (for example, JP-A-3-12470, JP-A-3-17175, JP-A-5-155901). Such). However, even in these improved methods, it may be necessary to set the particle size of pregelatinized starch and mix it with additives (borate, sulfate, urea, saccharide, etc.), and it takes time to dissolve starch in water. In many cases, it is not possible to completely suppress the occurrence of mamako even if the work is done with great care.

[0006] As described above, the conventional corrugated board adhesives have been attempted to be improved in order to solve the complication of the paste making process and the problems when the starch is dissolved, and to enhance the suitability for high-speed bonding. Not yet satisfied.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the problems associated with the conventional corrugated board adhesives of the no-carrier system, such as the complexity of the paste-making paste and the problem of starch dissolution, and to improve the fluidity of the adhesives. An object of the present invention is to provide an adhesive for corrugated board which has improved initial adhesiveness and is also suitable for high-speed bonding.

[0008]

As a result of various studies to solve the above problems, the present inventors have found that in a method for producing a carrier-free adhesive for corrugated board, strong stirring that imparts high mechanical shearing force. It has been found that the above-mentioned problems can be solved by adopting a combination of sizing means, and the present invention has been completed.

That is, according to the present invention, an excessive amount of alkali is added to an aqueous suspension of starch to partially swell the whole starch, and then boric acid or boric acid and borax are added to stop the swelling and to give an appropriate viscosity. In a paste making method by a no-carrier method including a step of obtaining an adhesive for corrugated board, the partial swelling and the swelling stop are performed while shearing with a powerful stirring means having a peripheral speed of 500 m / min or more. This is a method for making a starch adhesive for corrugated board.

The method for making the starch adhesive for corrugated board of the present invention will be described in detail below. The starch used in the present invention may be a starch used in a normal no-carrier method, and is not particularly limited, but raw corn starch (including high amylose corn starch and waxy corn starch), potato, tapioca, wheat, starch such as sweet potato Alternatively, a combination of these is generally used.

In order to enhance the effect of the present invention,
A starch (hereinafter referred to as a subordinate starch) having a gelatinization initiation temperature in an alkaline amylograph lower than that of the above-mentioned main raw starch by 5 ° C. or more, more preferably by 10 ° C. or more is used in combination with the raw starch. The subordinate starch may be a processed starch whose gelatinization start temperature is lowered by etherification, esterification, grafting or a combination thereof according to a conventional method, or an unprocessed starch whose gelatinization start temperature is 5 ° C. or more lower than that of the main starch. Starch can be used. Here, the alkali amylograph is an amylograph in which 30 g of starch is made into an aqueous suspension of 450 g and 50 ml of 4.9 wt% caustic soda is added, and the temperature at the time of passing 100 BU is the gelatinization start temperature. To do. Further, these subordinate starches may be subjected to a treatment for lowering viscosity such as oxidation, acid treatment, and dextrinization.

Mixing ratio of these starches and double water ratio of water to starch composition (multiple of water to starch on a weight basis)
Should be appropriately set in consideration of the initial adhesive strength, the normal adhesive strength, and the fluidity of the adhesive. The blending ratio (weight ratio) of the subordinate starch to the main starch is 1 to 30% by weight, more preferably 3 to 20% by weight. The double water ratio is preferably in the range of 2 to 4.

In the pasting method of the present invention, pasting is performed while applying a shearing force with a strong stirring means. The strong stirring means may be any one capable of imparting a strong mechanical shearing force, and examples thereof include a disperser type, a mixer type, a homogenizer type, and a mill type stirrer. A stirrer of the type that can always maintain the fluid state is used. In addition, a low-speed stirrer may be used as an auxiliary in order to fluidize the entire suspension.

The strong stirring means is used at a peripheral speed of 500 m / min or more, depending on the type of stirring means and the type of starch used. When the peripheral speed of the stirring means is less than 500 m / min, the difference in effect from the case of using a normal low stirring device is not remarkable, and the object of the present invention is not achieved. The upper limit of the peripheral speed is not particularly limited, but is generally limited by the heat generated by the shearing of the stirring device, and therefore the upper limit of the peripheral speed is generally about 3,000 to 4,000 m / min.

In the paste making method of the present invention, an excessive amount of alkali is added to an aqueous suspension of starch to partially swell the whole starch, and then boric acid or boric acid and borax are added to stop the swelling to an appropriate degree. The step of obtaining a starch adhesive having a sufficient viscosity can be performed in the same manner as in the pasting method by the conventional no carrier method, except that a strong shearing force is applied.

An alkali metal hydroxide such as caustic soda is used as an alkali as a starch swelling agent, and boric acid is added as a starch swelling stopper and an adhesive strength aid. In addition, borax may be further added if necessary. The amount of these added is the glue making time, the viscosity of the adhesive,
It is set in consideration of the gelatinization temperature and the adhesive strength of the adhesive itself, but the amount of alkali added is 2 to 5% by weight of starch, and the amount of boric acid added is 0.5 to 3% by weight of starch. The amount of borax added is preferably in the range of 1 to 3% by weight of starch. Further, the temperature of the suspension during gluing is determined in consideration of the gluing time and the gelatinization temperature of the adhesive, but is preferably in the range of 20 to 45 ° C. In addition, if necessary, the adhesive may be water resistant, defoaming agent,
Preservatives and the like may be added.

[0017]

The method for producing a starch adhesive for corrugated board using the carrierless method of the present invention has the following advantages over the conventional methods. (B) Mamako is not generated, and the dissolution of starch in the tank becomes very easy. (B) With strong stirring, the alkali can be added at a high concentration in a shorter time. (C) Since strong stirring (strong shearing) is applied, the starch swollen by alkali and heat is dispersed, and the fluidity is improved. In particular, this effect is remarkable in the subordinate starch having a low gelatinization starting temperature, and the starch having advanced dispersion functions as a carrier portion of the stain hole system.

(D) Since the secondary starch is further dispersed, the entanglement with the cardboard base paper is improved, and the initial adhesiveness is improved. (E) By appropriately selecting the subordinate starch, it becomes possible to make a paste with a low water doubling ratio, which was difficult with the conventional no-carrier method. (F) If this adhesive for corrugated board is used for high-speed bonding, stable corrugated board can be manufactured with less occurrence of adhesion failure.

[0019]

EXAMPLES The effects of the present invention will be described below with reference to examples. The characteristics used in the above description and examples were measured and evaluated by the following methods. (1) Flowability The flowability of the adhesive is judged by the flow of the adhesive when it flows out of the beaker. Excellent (long adhesive, good flowability of the whole adhesive), good (very good) Long adhesive), △ Normal, × Poor (short adhesive, sloppy adhesive).

(2) Initial adhesive strength A predetermined amount of adhesive glue liquid after being glued on a glass plate and stored at 39 ° C. for 60 minutes is applied, and corrugated cardboard of A-stage (K220 × 12)
Glue to the top of 5). Immediately attach it to a liner (K220, 12 × 13 cm) heated to 110 ° C.,
Strength (stress) when immediately peeled after pressure bonding for 5 seconds with a device that combines a pin tester and an auto recorder
To measure. (3) Normal-state adhesive strength A predetermined amount of an adhesive paste solution, which has been glued on a glass plate and stored at 39 ° C. for 60 minutes, is applied and glued to the top of the A-tier (K280 × 180). This is placed on a liner (K280, 5 × 8 cm) heated to 120 ° C. and pressure-bonded for 5 seconds to obtain a sample. This is conditioned under the conditions of 20 ° C. and 65 RH% for 3 days, and then measured according to JIS.

Example 1 225 g of unprocessed corn starch was dissolved in hot water using a Corless type high-speed agitator having a strong shearing force (Coleth type blade, diameter 70 mm), and paste was prepared by the method shown in FIG. It was In addition, storage after completion of the paste preparation was performed using a low-speed stirrer (3 propeller blades, 2 stages, diameter: 70 mm, 400 rpm) in a constant temperature bath at 39 ° C. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 25% caustic soda Boric acid Double water Peripheral speed m / min (rotation speed rpm) 1-a 25.40 2.93 3.3 660 (3000) Boric acid + borax 1-b 25.40 2.28 + 1.0 3.3 660 (3000)

Comparative Example 1 Ordinary low agitation device (3 propeller blades 2 stages 70 mm
(Diameter) is used to dissolve 200 g of raw corn starch in warm water and paste is prepared by the method shown in FIG. The storage is the same as in the example. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 5.2% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 105 2.60 3.3 98.9 (450)

Example 2 225 g of raw tapioca starch was dissolved in warm water to prepare Example 1
A paste was prepared in the same manner as in. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 24.12 2.93 3.3 660 (3000)

Comparative Example 2 200 g of raw tapioca starch was dissolved in warm water to prepare Comparative Example 1
Paste was prepared in the same manner as in. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 4.75% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 105 2.60 3.3 98.9 (450)

Example 3 Quaternary positive starch (tapioca base, gelatinization starting temperature 45.0)
4.5 g) and raw corn starch (gelatinization start temperature 5
The raw corn starch used at 2.0 ° C. and below is the same. ) 220.5 g was compounded (compounding ratio 2: 9
8) Then, it was dissolved in warm water and glue was prepared in the same manner as in Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 25.15 2.93 3.3 660 (3000)

Comparative Example 3 Quaternary positive starch (tapioca base, gelatinization starting temperature 45 ° C.)
4 g and 196 g of unprocessed corn starch were blended (blending ratio 2:98), dissolved in warm water, and glued in the same manner as in Comparative Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 5.2% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 105 2.60 3.3 98.9 (450)

Example 4 Quaternary positive starch (horse starch base, gelatinization starting temperature 34.5 ° C.)
13.5 g and 211.5 g of unprocessed corn starch were blended (blending ratio 6:94), dissolved in warm water, and a 3.3 times water paste was prepared in the same manner as in Example 1 (4-a). . Also,
15 g of the above positive starch and 235 g of unprocessed corn starch were mixed (mixing ratio 6:94) and dissolved in warm water, and 2.5 times water was used for sizing in the same manner as in Example 1 (4-b). The weight (g), double water ratio, and rotation condition of each additive chemical are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 4-a 25.15 2.93 3.3 660 (3000) 4-b 25.25 3.25 2.5 660 (3000)

Comparative Example 4 Quaternary positive starch (horse starch base, gelatinization starting temperature 34.5 ° C.)
12 g and 188 g of unprocessed corn starch were blended (blending ratio 6:94), dissolved in warm water, and glued in the same manner as in Comparative Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 5.2% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 105 2.60 3.3 98.9 (450)

Example 5 Amphoteric starch (tapioca base, gelatinization starting temperature 42.6 ° C.)
13.5 g and 211.5 g of unprocessed corn starch were blended (blending ratio 6:94), dissolved in warm water, and glued in the same manner as in Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 26.04 2.93 3.3 660 (3000)

Example 6 Urea phosphorylated starch (cons base, gelatinization starting temperature 35.5)
(° C) 13.5 g and raw corn starch 211.5 g were blended (blending ratio 6:94), dissolved in warm water, and glued in the same manner as in Example 1. Weight of each additive chemical (g),
The double water ratio and rotation conditions are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 26.13 2.93 3.3 660 (3000)

Example 7 15 g of a low viscosity quaternary positive starch (tapioca base, gelatinization starting temperature 44.5 ° C.) and 235 g of unprocessed corn starch were mixed (mixing ratio 6:94) and dissolved in warm water. Gluing was performed in the same manner as in 1. Weight of each additive chemical (g),
The water doubling ratio and the rotation conditions at the time of paste making are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 23.91 3.25 2.5 660 (3000)

Example 8 Low-viscosity urea-phosphorylated starch (cons base gelatinization starting temperature 3
2.3 ° C.) 37.5 g and raw corn starch 212.
5 g was blended (blending ratio 15:85), dissolved in warm water, and glued in the same manner as in Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 25% caustic soda Boric acid Double water ratio Peripheral speed m / min (rotation speed rpm) 25.27 3.25 2.5 660 (3000)

Example 9 Quaternary positive starch (tapioca base, gelatinization starting temperature 45 ° C.)
A blend (500 kg) of corn starch and unprocessed corn starch was blended at a compounding ratio of 2:98, and subjected to an actual machine test. For stirring, a conventional low stirrer and a high speed stirrer having strong shearing force (toothed disc type blade, diameter 170 mm, peripheral speed of 1900 m / min) were used together. As the paste making method, the rotation number of the stirrer was 3550 rpm and the concentration of caustic soda was 9.1 w / w.
The procedure was almost as shown in Fig. 1 except that the percentage was changed. 9.1% caustic soda Boric acid Borax Double water ratio Peripheral speed m / min (rotation speed rpm) 165kg 6.0kg 2.0kg 3.3 280 (300) 1900 (3550)

Comparative Example 5 A mixture of quaternary positive starch (tapioca base, gelatinization starting temperature 45 ° C.) and unprocessed corn starch in the paste making apparatus used in Example 9 at a compounding ratio of 2:98 (500
g) was subjected to an actual machine test using only a low stirrer.

Comparative Example 6 12 g of alferized starch (tapioca base) and 188 g of unprocessed corn starch were mixed (mixing ratio 6:94), and paste was prepared by the method shown in FIG. The pasting device and the storage method are the same as in Comparative Example 1. The weight (g) of each additive chemical, the water doubling ratio, and the rotation conditions during paste making are as follows. 5.2% caustic soda Boric acid Double water ratio Peripheral speed m / min (rpm) 105 2.60 3.3 98.9 (450)

The results obtained in each Example and Comparative Example are shown in Table 1.

[Table 1]

As shown in Table 1, according to the pasting method of the present invention, the pasting method is much easier than the conventional pasting method with the same raw material and the same composition, and the obtained adhesive paste is obtained. The liquid has substantially improved fluidity and initial adhesiveness, while maintaining the normal adhesiveness to be equal to that of the conventional adhesive paste liquid. By properly selecting the compounding ratio and raw materials, we were able to achieve low water doubling. From these facts, it is understood that the adhesive glue solution according to the present invention can sufficiently cope with high-speed bonding.

[Brief description of drawings]

FIG. 1 shows an example of a sizing method of the present invention.

FIG. 2 shows an example of a conventional pasting method.

FIG. 3 shows another example of a conventional pasting method.

Claims (2)

[Claims] 1. A corrugated board having an appropriate viscosity by adding an excessive amount of alkali to an aqueous starch suspension to partially swell the whole starch and then adding boric acid or boric acid and borax to stop the swelling. In a no-carrier type sizing method including a step of obtaining an adhesive, 500 m / mi
A method for making a starch adhesive for corrugated board, which comprises performing the partial swelling and the swelling stop while applying shearing with a strong stirring means having a peripheral speed of n or more. 2. The starch according to claim 1, wherein a starch prepared by blending 1 to 30% by weight of a processed starch with a gelatinization start temperature in an alkaline amylograph lower than that of the unprocessed starch by 5 ° C. or more is used. Glue method.