Lamination speed enhancer and method for enhancing it

Abstract

To provide a sticking speed improver used for a starch adhesive for corrugated cardboard.SOLUTION: The present invention provides a sticking speed improver used for a starch adhesive for corrugated cardboard, containing a phenolic resin.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a lamination speed enhancer for use in a starch-based adhesive for corrugated cardboard, a starch-based adhesive for corrugated cardboard, a method for producing a corrugated cardboard sheet, a method for producing a starch-based adhesive for corrugated cardboard, and a method for improving the lamination speed in the production of a corrugated cardboard sheet. [Background technology]

[0002] The production volume of general-purpose corrugated cardboard sheets used for cardboard boxes used for parcel delivery and packing moving luggage has been increasing rapidly in recent years due to the rapid spread of internet shopping and the increase in the volume of parcel delivery services.

[0003] There is a strong demand for faster lamination speeds in the production of such general corrugated cardboard sheets. Furthermore, in recent years, growing interest in environmental issues such as CO2 reduction has led to a demand for methods to improve lamination speeds and produce larger quantities of corrugated cardboard sheets using less energy.

[0004] To improve lamination speed, methods that have been used so far include increasing the amount of alkali (caustic soda) added to starch-based adhesives for corrugated board to lower the gelatinization temperature, or increasing the starch concentration to reduce the drying load. However, when increasing the alkali to lower the gelatinization temperature, if the amount of alkali is increased too much, the viscosity of the adhesive in the storage tank increases, making it difficult to control the amount of glue applied and to transport the adhesive within the process, and the viscosity stability of the adhesive decreases, making stable production difficult due to increased viscosity over time.

[0005] Furthermore, even in the case of the method of increasing the starch concentration, if the concentration is increased too much, the viscosity in the storage tank increases, causing the above-mentioned problems, and in addition, there is a problem that sufficient moisture cannot be obtained for gelatinization, which in turn reduces the adhesive strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2007-284568 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a lamination speed improver for use in a starch-based adhesive for corrugated cardboard, a starch-based adhesive for corrugated cardboard, a method for producing a corrugated cardboard sheet, a method for producing a starch-based adhesive for corrugated cardboard, and a method for improving the lamination speed in the production of a corrugated cardboard sheet.

[0008] As a result of extensive research in light of the above-mentioned problems, the present inventors have found that by incorporating a phenolic resin into a starch-based adhesive for corrugated board, the viscosity decreases within the storage temperature range of the storage tank, and no problems occur even when the amount of alkali added or the starch concentration is increased, and the viscosity quickly increases within the temperature range used for heating and drying in the lamination process, and initial adhesive strength is achieved, thereby completing the present invention.

[0009] The present invention includes the following aspects.

[0010] Item 1, a lamination speed improver for use in starch-based adhesives for corrugated board, containing a phenolic resin.

[0011] Item 2. The lamination speed improver according to Item 1, wherein the phenolic resin is a resol type phenolic resin or a novolac type phenolic resin.

[0012] Item 3. A starch-based adhesive for corrugated board, comprising the lamination speed improver according to Item 1 or 2.

[0013] Item 4. The starch-based adhesive for corrugated cardboard according to Item 3, wherein the solid content of the phenolic resin is 0.5 to 50 parts by mass per 100 parts by mass of the total solid content of the starch in the starch-based adhesive.

[0014] Item 5. The starch-based adhesive for corrugated cardboard according to Item 3 or 4, further comprising a ketone resin, wherein the solid content of the ketone resin is 75 parts by mass or less per 100 parts by mass of the solid content of the phenolic resin.

[0015] Item 6. A method for producing a cardboard sheet, comprising laminating a core and a liner using a starch-based adhesive for cardboard containing the laminating speed improver according to Item 1 or 2.

[0016] Item 7. A method for producing a starch-based adhesive for corrugated cardboard, comprising adding the laminating speed improver according to Item 1 or 2 to a starch-based adhesive for corrugated cardboard.

[0017] Item 8. A method for producing a starch-based adhesive for corrugated board according to Item 7, wherein the viscosity of the starch-based adhesive for corrugated board to which a laminating speed improver has been added is 200 RVU or more, as measured using a Rapid Visco Analyzer (RVA) at a temperature rise rate of 5.5°C / min and a rotation speed of 160 rpm, at a temperature at which the starch-based adhesive for corrugated board before adding the laminating speed improver reaches 100 RVU (Rapid Visco Analyzer Units).

[0018] Item 9. A method for manufacturing a corrugated board adhesive according to Item 7 or 8, wherein the heating and cooling block of a Rapid Visco Analyzer (RVA) is programmed to maintain a constant temperature of 90°C from immediately after the start of measurement until the end of measurement, the RVA is preheated to 90°C, 30 g of the sample is placed in an aluminum RVA standard can, and the can is attached to the RVA together with a standard RVA paddle, and the RVA is programmed to stir at a paddle rotation speed of 500 rpm from immediately after the start of measurement until the end of measurement, and under these conditions when viscosity measurement is started, the time from the start of viscosity measurement until a viscosity of 150 RVU (Rapid Visco Analyzer Units) begins to rise is 50 seconds or less.

[0019] Item 10. A method for improving the lamination speed in the production of cardboard sheets, comprising adding the lamination speed improver according to item 1 or 2 to a starch-based adhesive paste for cardboard. [Effects of the Invention]

[0020] The present invention provides a lamination speed enhancer for use in a starch-based adhesive for corrugated cardboard, a starch-based adhesive for corrugated cardboard, a method for producing a corrugated cardboard sheet, a method for producing a starch-based adhesive for corrugated cardboard, and a method for improving the lamination speed in the production of a corrugated cardboard sheet. In particular, by using a phenolic resin as a lamination speed enhancer, the starch-based adhesive for corrugated cardboard exhibits excellent functionality in both the storage temperature range of the storage tank and the temperature range during heat drying in the lamination process, thereby enabling the production of corrugated cardboard sheets at a high lamination speed. [Brief explanation of the drawings]

[0021] [Figure 1] The relationship between compression time and initial adhesive strength is shown. [Figure 2] The method for evaluating water repellency is shown schematically. [Figure 3] Viscosity increase at 90°C. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention will be described in detail below.

[0023] The present invention relates to a lamination speed enhancer for use in starch-based adhesives for corrugating cardboard.

[0024] In this specification, the term "a lamination speed improver for use in a starch-based adhesive for corrugated cardboard" refers to an agent that is added to a starch-based adhesive for corrugated cardboard to produce corrugated cardboard sheets at a faster lamination speed. It is preferable that the increase in lamination speed be achieved without impairing the quality of the corrugated cardboard sheets (for example, the yield excluding defective products in which the core and liner are separated).

[0025] In this specification, "starch-based adhesive" refers to an adhesive that is primarily made of starch and has adhesive functions that utilize the water absorption, swelling, and gelatinization properties of starch that are manifested by heating the adhesive. "Starch-based adhesive for corrugated cardboard" refers to a starch-based adhesive used, for example, to bond corrugated core base paper and liner base paper together. "Adhesive" can also be referred to as "glue," and the terms are used interchangeably in this specification.

[0026] The starch-based adhesive in which the laminating speed enhancer of the present invention is used can be used in the production of any corrugated board sheet. In one preferred embodiment of the present invention, the starch-based adhesive in which the laminating speed enhancer is used is used in the production of general-purpose corrugated board or water-repellent corrugated board.

[0027] Here, water-resistant corrugated board refers to "water-resistant corrugated board" as defined in the corrugated board industry standard "Waterproof Corrugated Board" M0002:2000 (Japan Corrugated Box Association), i.e., "corrugated board that has been processed so that it does not lose much strength even when submerged for a long time." "Water-repellent corrugated board" refers to "corrugated board whose surface has been treated to repel water and turn it into droplets, preventing water penetration, even when water is splashed on it for a short time," as defined in the corrugated board industry standard M0002:2000. Water-resistant corrugated board and water-repellent corrugated board are collectively referred to as "waterproof corrugated board." "General-purpose corrugated board" refers to corrugated board other than waterproof corrugated board that has not been given so-called water resistance and / or water repellency.

[0028] The lamination speed enhancer of the present invention contains a phenolic resin (phenol-formaldehyde resin, phenol-formaldehyde condensate) as an active ingredient. Here, the active ingredient means a component essential for the lamination speed enhancer of the present invention to exhibit its effect. In the present invention, the phenolic resin is a resin obtained by condensing a phenol with formaldehyde.

[0029] Phenolic resins have been known to be used as components for imparting water resistance (water-resistant agents), but their use as lamination speed enhancers has not been known. Furthermore, their effectiveness as water-resistant agents has tended to be inferior to that of other water-resistant agents.

[0030] The phenolic resin contained in the lamination speed improving agent of the present invention may be either a resol type phenolic resin obtained by reacting raw material compounds in the presence of a basic catalyst, or a novolac type phenolic resin obtained by reacting raw material compounds in the presence of an acidic catalyst.

[0031] Phenols, which are raw material compounds in the production of phenolic resins, include phenol, cresol, amylphenol, bisphenol A, butylphenol, octylphenol, nonylphenol, dodecylphenol, etc. The phenols can be used alone or in combination of two or more.

[0032] Phenolic resins can be produced by reacting a phenol with formaldehyde in the presence of a basic or acidic catalyst.

[0033] The molecular weight of the phenolic resin is not particularly limited as long as it can improve the lamination speed and does not inhibit the adhesive function of the starch-based adhesive.

[0034] The lamination speed enhancer of the present invention containing a phenolic resin may be the solid content of the phenolic resin itself, or a solution or dispersion (slurry) of the phenolic resin. When it is a solution or dispersion, the medium is an aqueous medium mainly composed of water. The aqueous medium may contain a water-soluble organic solvent (e.g., alcohols such as methanol and ethanol) in addition to the main component water. From the viewpoint of ease of mixing with the starch-based adhesive, resol-type phenol supplied in the form of a solution or dispersion is more preferred. From the viewpoint of ease of adding the lamination speed enhancer to a starch-based adhesive for corrugated board, resol-type phenol using water as the solvent is even more preferred. In another embodiment, water-soluble phenolic resins that have traditionally been used as water-resistant agents for starch-based adhesives for corrugated board can also be suitably used.

[0035] The laminating speed improver of the present invention is intended to be added to a starch-based adhesive for corrugated board to produce corrugated board sheets at a higher laminating speed. The starch-based adhesive for corrugated board will be described below.

[0036] The starch in the starch-based adhesive for corrugated board contains a main starch consisting of ungelatinized raw starch and a carrier starch, which is a modified starch that has been completely gelatinized with alkali and heat. The starch-based adhesive for corrugated board is a dispersion of starch in an aqueous medium mainly composed of water.

[0037] A typical example of the composition of a starch-based adhesive for corrugated board includes water, a main starch, a carrier starch, an alkali, and a boron compound.

[0038] The starch used in the present invention can be any starch that has been used in conventional starch-based adhesives for corrugated cardboard. For example, corn starch, high-amylose corn starch, tapioca starch, wheat starch, potato starch, sweet potato starch, etc., as well as starches obtained by oxidizing, acid-treating, esterifying, or etherifying these starches, can be used. One or more types of starch can be used in combination.

[0039] In the starch-based adhesive of the present invention, the water fold ratio is usually about 1.9 to 4.5. By setting the water fold ratio to 1.9 or more, sufficient water is supplied for the gelatinization of the main starch, resulting in good adhesion. Furthermore, by setting the water fold ratio to 4.5 or less, the solids concentration of the adhesive can be maintained at a predetermined level or higher, resulting in good initial adhesion. In this specification, the "water fold ratio" refers to the mass ratio of (total water amount / total starch amount) in the starch-based adhesive.

[0040] Furthermore, in the starch-based adhesive of the present invention, the carrier ratio is preferably generally about 5 to 30% by mass. By setting the carrier ratio to 5% or more, good water retention and initial adhesive strength can be achieved. Furthermore, setting the carrier ratio to 30% or less is preferred from the viewpoint of obtaining appropriate viscosity and storage stability as an adhesive for corrugated cardboard.

[0041] In one preferred embodiment of the present invention, the starch-based adhesive contains high-amylose starch as a carrier starch. As used herein, "high-amylose starch" refers to starch with an amylose content of 50% or more. Examples of high-amylose starch include high-amylose cornstarch.

[0042] When high amylose starch is used as the carrier starch, the carrier starch may consist of only high amylose starch or may be combined with one or more other starches. From the viewpoint of improving the initial adhesion rate, the carrier starch may further contain rhizome starch in addition to high amylose starch. Examples of rhizome starch include tapioca starch, potato starch, and sweet potato starch.

[0043] When the carrier starch contains high-amylose starch and rhizome starch, the blending ratio of the high-amylose starch and rhizome starch can usually be about 30:70 to 99:1.

[0044] The starch-based adhesive of the present invention may further contain an alkali. The alkali used in the present invention may be any of those conventionally used in starch-based adhesives for corrugated board, such as sodium hydroxide (caustic soda) and potassium hydroxide. Alkalis may be used alone or in combination of two or more. The alkali is preferably sodium hydroxide (caustic soda). The caustic content of the adhesive of the present invention may be determined according to the glue-making conditions in order to obtain an appropriate gelatinization temperature. Generally, the amount of alkali added is preferably in the range of 0.5 to 1.5 mass% in terms of caustic content. In this specification, "caustic content" refers to the mass ratio of (caustic content / total glue liquid volume) in the starch-based adhesive.

[0045] The starch-based adhesive of the present invention contains the above-mentioned application speed enhancer (phenolic resin). The content of the application speed enhancer is not particularly limited, but is preferably 0.5 to 50 parts by mass, more preferably 1 to 20 parts by mass, per 100 parts by mass of the total solid content of starch. By setting the content within this range, a high effect of improving the application speed can be achieved.

[0046] In one preferred embodiment, the starch-based adhesive of the present invention may contain, as a component for imparting water resistance (water-resistant agent), thermosetting resins such as ketone resins (ketone-formaldehyde resins, ketone-melamine resins) and melamine resins, epoxy resins, thermoplastic elastomers such as styrene-butadiene rubber (SBR), etc. However, in this specification, phenolic resins are not included in the thermosetting resins used as water-resistant agents. Examples of epoxy resins include epoxy compounds such as polyamide epichlorohydrin, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol polyglycidyl ether. The content of the water-resistant agent can usually be 1 to 20% by mass, preferably 3 to 10% by mass, based on the total solid mass of the starch.

[0047] When the starch-based adhesive of the present invention contains a ketone resin as a water-resistant agent, the solid content of the ketone resin is preferably 75 parts by mass or less per 100 parts by mass of the solid content of the phenolic resin, from the viewpoint of achieving a higher effect of improving the lamination speed.

[0048] In another preferred embodiment, the adhesive of the present invention does not contain a water-resistant agent.

[0049] The starch-based adhesive of the present invention may further contain a boron compound. The boron compound is thought to induce pseudo-crosslinking of gelatinized starch, thereby enhancing initial adhesive strength. The content of the boron compound, calculated as borax, is typically about 1.5% to 3.3% by mass, preferably about 1.6 to 3.3% by mass, more preferably about 1.6 to 3.0% by mass, and particularly preferably about 0.7 to 2.7% by mass, based on the total solids mass of the starch. By ensuring that the content is equal to or greater than the above-mentioned lower limit, sufficient improvement in initial adhesive strength can be achieved. Furthermore, by ensuring that the content is equal to or less than the above-mentioned upper limit, gelation and / or high viscosity caused by the reaction between borax and starch can be suppressed.

[0050] The starch-based adhesive of the present invention may further contain a hydrous inosilicate mineral. Examples of hydrous inosilicate minerals include hydrous magnesium inosilicate and hydrous aluminum-magnesium inosilicate. Hydrous inosilicate minerals are included in clay minerals that contain hydrous inosilicate minerals as their main component. Examples of clay minerals that contain hydrous inosilicate minerals as their main component include those commonly known as "sepiolite," "attapulgite," and "palygorskite," and these can be used in the present invention.

[0051] There are two methods for producing clay minerals whose main component is hydrous inosilicate mineral: dry grinding and wet grinding. Clay minerals whose main component is hydrous inosilicate mineral produced by either grinding method can be used in the present invention. However, wet grinding is preferred because it has a high ability to defibrate / disperse the fine fiber structure of the clay mineral and can bring out the functions of the hydrous inosilicate mineral.

[0052] In the present invention, the content of the hydrous inosilicate mineral is usually about 0.1 to 15% by mass, preferably about 1 to 10% by mass, based on the total mass of the solids content of the starch. By ensuring that the content of the hydrous inosilicate mineral is equal to or greater than the above-mentioned lower limit, a sufficient effect of containing the hydrous inosilicate mineral is observed. Having the content of the hydrous inosilicate mineral equal to or greater than the above-mentioned lower limit is preferred from the standpoint of economy and from the standpoint of achieving good adhesive properties without imparting strong thixotropy, which is one of the properties of the hydrous inosilicate mineral.

[0053] The starch-based adhesive of the present invention can be prepared by a one-tank Stainhole system, a two-tank Stainhole system, a premix system, a no-carrier system, or the like.

[0054] The one-tank carrier method is a sizing method in which a starch slurry is prepared in one tank, alkali is added to gelatinize the starch, water is added to dilute the alkaline paste, the main starch (ungelatinized starch) is added to the diluted alkaline paste, and borax is added as needed and mixed. When using the one-tank carrier method, the processing temperature is preferably 30 to 45°C from the viewpoint of stabilizing the final viscosity of the adhesive and viscosity over time. Furthermore, the stirring speed during sizing is preferably 1000 rpm or higher, more preferably 1500 to 5000 rpm, from the viewpoint of loosening and dispersing the fibers of the hydrous inosilicate mineral, such as sepiolite, which is optionally contained. Examples of devices capable of stirring at a speed of 1000 rpm or higher include a sizing device manufactured by Sarco, a sizing device manufactured by Mitsubishi Heavy Industries, Ltd. (MREX), and a sizing device manufactured by Kakida Manufacturing Co., Ltd.

[0055] A preferred preparation method using the one-tank carrier system involves, for example, placing 30 to 45°C hot water in one tank, stirring with a homogenizer at 3000 to 5000 rpm, adding starch, and optionally adding a hydrated inosilicate mineral. After dissolving and dispersing, an alkali is added and the mixture is stirred for 10 to 15 minutes, followed by adding 30 to 45°C hot water, followed by adding the main starch (ungelatinized starch), and optionally adding borax and a waterproofing agent, and stirring for 10 to 15 minutes to produce a starch-based adhesive for corrugated board.

[0056] The timing of adding the laminating speed enhancer of the present invention is not particularly limited. For example, the laminating speed enhancer can be added while stirring during the production process of a starch-based adhesive for corrugated board. As a specific example, the laminating speed enhancer can be added after adding starch, an alkali, and a boron compound to water and stirring. In another embodiment, the laminating speed enhancer can be added to water and stirring, and then the starch, alkali, and a boron compound can be added to the water to which the laminating speed enhancer has been added (dissolved or dispersed). In yet another embodiment, the laminating speed enhancer can be added to a tank capable of stirring the adhesive, such as a storage tank that supplies adhesive to a corrugator, during the corrugated board sheet production process. The laminating speed enhancer can also be added multiple times during the production process of a starch-based adhesive for corrugated board.

[0057] In a preferred embodiment of the method for producing a starch-based adhesive for corrugating board of the present invention, the viscosity of the starch-based adhesive for corrugating board to which a laminating speed improver has been added is 200 RVU or more, as measured using a Rapid Visco Analyzer (RVA) at a temperature rise rate of 5.5°C / min and a rotation speed of 160 rpm, at a temperature at which the starch-based adhesive for corrugating board before adding the laminating speed improver reaches 100 RVU (Rapid Visco Analyzer Units).

[0058] For the measurement, 30.0 g of the sample starch-based adhesive for corrugated board is placed in an aluminum RVA measurement can (manufactured by Perten, inner diameter approximately 36 mm, height approximately 65 mm) using an RVA standard aluminum can and paddle (manufactured by NSP Perten), and the measurement is performed. The starch-based adhesive for corrugated board before the addition of the laminating speed enhancer contains, for example, the above-mentioned water, main starch, carrier starch, alkali, boron compound, etc., but does not contain the phenolic resin that is the laminating speed enhancer.

[0059] In another preferred embodiment of the method for producing a starch-based adhesive for corrugated board of the present invention, the heating and cooling block of the RVA is programmed to maintain a constant temperature of 90°C from immediately after the start of measurement to the end of measurement, 30 g of the sample is preheated to 90°C, and the sample is placed in an aluminum standard RVA can and attached to the RVA together with a standard RVA paddle. The can is programmed to stir at a paddle rotation speed of 500 rpm from immediately after the start of measurement to the end of measurement, and under these conditions when starting viscosity measurement, the time from the start of viscosity measurement until a viscosity of 150 RVU is reached is 50 seconds or less.

[0060] Viscosity measurements using a Rapid Visco Analyzer (RVA) can be performed in accordance with standard tests such as AACC (American Association for Clinical Chemistry)-22-08 and ICC (International Color Consortium) Standard No. 162.

[0061] When measuring the viscosity using RVA, the temperature of the starch-based adhesive for corrugated cardboard is about 30 to 40°C before heating.

[0062] The viscosity of the starch-based adhesive for corrugated board of the present invention at the completion of the glue production (immediately after glue production) is not particularly limited. The viscosity can be appropriately set depending on the required operating conditions, such as the amount of adhesion to the linerboard and the lamination speed. From the standpoint of ease of adjusting the amount of adhesion to the linerboard (for example, adjustment so that the amount of adhesion to the linerboard does not become too great) and viscosity stability, the viscosity of the starch-based adhesive for corrugated board of the present invention immediately after glue production (measured with a Brookfield viscometer) is preferably 700 mPa·S or less, more preferably 600 mPa·S or less, and even more preferably 500 mPa·S or less. Furthermore, from the viewpoint of ease of adjusting the amount of the starch-based adhesive for corrugated board adhered to the linerboard (for example, adjustment can be made so that the amount adhered to the linerboard does not become too small), and from the viewpoint of suppressing excessive penetration into the linerboard and achieving a desired strength, the viscosity of the starch-based adhesive for corrugated board of the present invention immediately after glue production (measured with a Brookfield viscometer) is preferably 100 mPa·S or more, and more preferably 150 mPa·S or more.

[0063] In this specification, "the time when glue production is completed" refers to the time when all the components of the starch-based adhesive for corrugated board, including the laminating speed improver of the present invention, are blended and thoroughly stirred. Stirring can generally be carried out for about 5 to 30 minutes, preferably about 10 to 20 minutes, and more preferably about 15 minutes. The "time when glue production is completed" can be within about 15 minutes after the end of stirring.

[0064] The present invention also provides a method for producing a corrugated cardboard sheet with an improved lamination speed. The method of the present invention produces a corrugated cardboard sheet using a starch-based adhesive containing the lamination speed enhancer of the present invention, and includes a step of laminating a core and a liner using the starch-based adhesive containing the lamination speed enhancer of the present invention.

[0065] The corrugating medium and liner used in the method for producing a corrugated board sheet of the present invention are not particularly limited. In one preferred embodiment of the present invention, the corrugating medium and liner used in the production of general-purpose corrugated board or water-repellent corrugated board can be used. This is because the starch-based adhesive for corrugated board quickly penetrates the liner, making it easier to form a deep "glue foot" and achieving high adhesive strength.

[0066] The liners used in water-resistant corrugated cardboard have relatively strong water-repellent properties on the adhesive surface with the core, whereas liners used in general-purpose corrugated cardboard do not have water-repellent properties, and water-repellent corrugated cardboard does not have as strong water-repellent properties as water-resistant cardboard.

[0067] The preferred water repellency of the adhesive surface between the corrugated fiberboard and the liner used in the manufacturing method of the cardboard sheet of the present invention can be determined by the time required for the height of a droplet to reach 0.50 mm or less when a 0.020 g to 0.040 g droplet of "Wet Tension Test Mixture" No. 48.0 (a liquid with a wet tension of 48.0 mN / m) specified in JIS K6768 is dropped using a Pasteur pipette or the like from a position 5.0 to 7.0 mm above the liner (see Figure 2). The time required for the droplet height to reach 0.50 mm or less is preferably 10 seconds or less, more preferably 5 seconds or less, and even more preferably 2 seconds or less.

[0068] The method for producing the corrugated cardboard sheet of the present invention can be carried out using a commonly used corrugator. That is, for example, a corrugated cardboard sheet can be produced by a method comprising the steps of: using a corrugator having at least a glue roll and a means for applying the starch-based adhesive for corrugated cardboard of the present invention to the glue roll, bringing the top edge of a corrugated core paper into contact with the glue roll and applying the starch-based adhesive for corrugated cardboard of the present invention to the top edge; and laminating liner paper to one or both sides of the core coated with the starch-based adhesive for corrugated cardboard of the present invention. For example, a corrugated cardboard sheet can be produced using the starch-based adhesive of the present invention using a corrugator equipped with a gravure roll.

[0069] A corrugated board gluing machine consists of an applicator roll and a doctor roll. Applicator rolls (gluing rolls) come in three types: metering rolls, satin rolls, and gravure rolls. Metering rolls and satin rolls have smooth surfaces, while gravure rolls have numerous indentations (cells) on their surface. The roll, immersed in a glue vat, picks up the adhesive adhering to its surface as it rotates, and the doctor roll scrapes off any excess adhesive adhering to the roll surface. With a smooth surface, adhesive with reduced viscosity cannot be adequately picked up by the roll, resulting in uneven application of the adhesive and patchy application, which affects adhesive performance. On the other hand, with a gravure roll, the adhesive penetrates the indentations (cells) engraved on the roll surface, making it easy to pick up even adhesive with reduced viscosity, enabling uniform application of the adhesive.

[0070] In the manufacture of corrugated cardboard, it is believed that heating after laminating the core and liner completes the bonding process through the following steps: (1) swelling of ungelatinized starch, (2) thickening of the adhesive, (3) gelatinization of the ungelatinized starch, and (4) drying of the adhesive. Heating is usually performed using a hot plate or similar. If bonding is insufficient, the core and liner may peel off due to pressure on the adhesive joint during cutting or slitting. Therefore, to ensure sufficient bonding, the lamination speed (line speed) is adjusted to adjust the heating time using a hot plate or similar.

[0071] Although the mechanism is unclear, by incorporating the laminating speed enhancer of the present invention into a starch-based adhesive for corrugated board, the viscosity is appropriately reduced within the storage temperature range of a storage tank (for example, 45°C or lower), so that problems do not occur when alkali is added or the starch content is increased, and the viscosity is quickly increased and initial adhesive strength is achieved within the temperature range of the heat drying step in the laminating process (for example, a heating step at an equipment temperature of 160°C or higher, more preferably 180°C or higher, in which case the sheet temperature is 60°C or higher, more preferably 65°C or higher). Therefore, by adding the laminating speed enhancer to a starch-based adhesive for corrugated board, the laminating speed in the production of corrugated board sheets can be improved.

[0072] Therefore, the present invention also provides a method for increasing the laminating speed in the production of corrugated cardboard sheets, which comprises the step of adding a laminating speed enhancer to a starch-based corrugating adhesive. The starch-based corrugating adhesive before the addition of the laminating speed enhancer contains, for example, the above-mentioned water, main starch, carrier starch, alkali, boron compound, etc., but does not contain the phenolic resin that is the laminating speed enhancer.

[0073] The method for improving lamination speed is applicable to any production method of corrugated board sheets, including, but not limited to, the production of general-purpose corrugated board, the production of water-repellent corrugated board, and the production of water-repellent corrugated board using a starch-based adhesive containing a water-resistant agent other than phenolic resin. [Example]

[0074] <Example> Example 1 <Preparation of carrier part> 600 g of water was placed in a 1 L stainless steel mug and heated to 60°C using a water bath, and 72 g of commercially available cornstarch for starch-based adhesives for corrugated cardboard (manufactured by Oji Cornstarch Co., Ltd.) was added, followed by dispersion using a Robomix mixer (4500 rpm) manufactured by Tokushu Kika Kogyo Co., Ltd. to prepare a starch slurry. While stirring, 50 g of a 25% caustic soda solution was added to this starch slurry, and the mixture was stirred for 15 minutes to produce a carrier starch for a starch-based adhesive for corrugated cardboard.

[0075] <Preparation of the main part> 840 g of water was placed in a 3 L stainless steel mug and heated to 35°C using a water bath. 485 g of commercially available cornstarch (manufactured by Oji Cornstarch Co., Ltd.) was added and dispersed using a Robomix mixer (4500 rpm) manufactured by Tokushu Kika Kogyo Co., Ltd. to prepare the main starch.

[0076] <Preparation of starch-based adhesive for corrugated cardboard> While stirring the obtained main starch with the stirrer (4000 rpm), the carrier starch was added at a rate of 120 g / min using a tube pump. The addition took 6 minutes.

[0077] Borax pentahydrate was added with continued stirring.

[0078] Furthermore, while continuing to stir, phenol resin (PX-24 manufactured by Aica Kogyo Co., Ltd.) was added in the amount shown in Table 1, and the mixture was stirred for 15 minutes.

[0079] The viscosity of the resulting adhesive was 280 mPa·S (measured with a Brookfield viscometer).

[0080] 30 g of the resulting adhesive was placed in an aluminum cup for measuring an RVA (Rapid Visco Analyzer, manufactured by Newport Scientific), and a temperature-viscosity curve was obtained using the measuring instrument at a heating rate of 5.5°C and a rotation speed of 160 rpm up to the point where 500 RVU was reached. The temperature at which 100 RVU was reached was measured from the obtained curve.

[0081] <Initial adhesive strength> 50mm x 85mm general-purpose single-faced corrugated cardboard (liner basis weight: 280g / core basis weight: 180g) with bone dry weight of 5g / m 2The adhesive for corrugated board was applied to the board and set in a pin tester equipped with a load cell. A liner (basis weight: 280 g) was placed on top of the adhesive and pressed with a hot plate (180°C) weighing 1 kg. The pressing time was 2, 3, or 5 seconds. In each case, the liner and single-faced corrugated board were immediately peeled off after pressing, and the strength at that time was measured with a load cell as the initial adhesive strength.

[0082] Examples 2 to 5 and Comparative Example The initial adhesive strength was measured in the same manner as in Example 1, except that the amounts of the phenolic resin and the ketone resin (water-resistant agent A (Oji Cornstarch Co., Ltd.) added were as shown in Table 1. The ketone resin was added immediately after the addition of the phenolic resin while stirring the cardboard adhesive, just like the phenolic resin.

[0083] The results are shown in Table 1 and FIG.

[0084] Comparative Example 2 <Manufacturing starch-based adhesives for corrugated cardboard using a one-tank system> 1010 g of water was placed in a 3 L stainless steel mug and heated to 35 °C in a water bath. 99 g of commercially available cornstarch for starch-based adhesives for corrugated cardboard (OHP-C153, manufactured by Oji Cornstarch Co., Ltd.) was added. While stirring with a Robomix mixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) at 4500 rpm, 55 g of a 25% caustic soda solution was added to the starch slurry and stirred for 15 minutes. While continuing to stir, 700 g of water, 545 g of commercially available cornstarch (manufactured by Oji Cornstarch Co., Ltd.), and 8.5 g of borax decahydrate were added and stirred for 15 minutes to produce a starch-based corrugated cardboard adhesive. The viscosity of the resulting adhesive was 240 mPa·s (measured with a Brookfield viscometer). The resulting adhesive was stored while stirring at 600 rpm using a Three-One motor, and the RVA and initial bond strength measurements described below were performed.

[0085] <Initial adhesive strength> 50mm x 85mm general-purpose single-faced corrugated cardboard (liner basis weight: 280g / core basis weight: 180g) with bone dry weight of 5g / m2 The corrugated cardboard adhesive was applied and set on a pin tester equipped with a load cell. A liner (basis weight: 280 g) was placed on it, and it was heat-pressed with a hot plate (180 °C) weighing 1 kg. The heat-pressing time was 3 seconds, 5 seconds, or 7 seconds. In each case, immediately after heat-pressing, the liner and the single-sided corrugated cardboard were peeled off, and the strength at that time was measured by a load cell as the initial adhesion strength.

[0086] <Viscosity increase at 90 °C using RVA> The heating and cooling block of an RVA (Rapid Visco Analyzer, manufactured by Newport Scientific) was programmed to be constant at 90 °C from immediately after the start of measurement to the end of measurement, and it was preheated to 90 °C. 30 g of the adhesive obtained above was collected in an RVA standard can (aluminum, manufactured by Perten), and it was attached to the RVA together with an RVA standard paddle, and it was programmed to stir at a paddle rotation speed of 500 r.p.m. from immediately after the start of measurement to the end of measurement.

[0087] Then, the measurement was started, and a time-RVA viscosity curve was obtained. This measurement was carried out 30 minutes and 150 minutes after the addition of borax decahydrate, which is the chemical added last in the process of preparing the starch-based adhesive for corrugated cardboard.

[0088] Example 7 A starch-based adhesive was prepared in a one-tank system in the same manner as in Comparative Example 2. And 5 minutes after the addition of borax decahydrate, 32.2 g of a resol-type water-soluble phenolic resin, trade name PR-967 (non-volatile content concentration 40%, manufactured by Sumitomo Bakelite Co., Ltd.), as it was, was added. This is an amount that is 5% by mass based on the total amount of starch (the total amount of carrier starch and main starch). The viscosity at the time when the stirring for 15 minutes after the addition of borax ended was 230 mPa·S. Then, the initial adhesion strength was measured in the same manner as in Comparative Example 2. Also, the viscosity increase at 90 °C was measured in the same manner as in Comparative Example 2. Incidentally, this measurement was carried out 30 minutes and 150 minutes after the addition of the phenolic resin, which is the chemical added last when manufacturing the corrugated cardboard adhesive of Example 7.

[0089] Example 8 Except for changing the amount of resol-type water-soluble phenolic resin added to 64.4 g (10% of the total starch amount), a starch-based adhesive was produced and the initial adhesive strength and RVA were measured in the same manner as in Example 7. The viscosity was 210 mPa·S after 15 minutes of stirring after the addition of borax.

[0090] The results obtained are shown in Table 2 and in the graph of FIG.

[0091] Starch-based adhesives for corrugated board containing the laminating speed enhancer of the present invention tended to have a short viscosity increase start time. It is presumed that the short viscosity increase start time improves the initial adhesive strength and enables an improvement in the laminating speed. Furthermore, starch-based adhesives for corrugated board containing the laminating speed enhancer of the present invention also tended to have a small decrease in initial adhesive strength even after the passage of time from the production of the glue. Because the decrease in initial adhesive strength is small, a longer pot life can be expected.

[0092] [Table 1]

[0093] [Table 2]

Claims

1. A method for increasing the lamination speed in the production of corrugated cardboard sheets, comprising a step of adding a lamination speed improver for use in a starch-based adhesive for corrugated cardboard, the lamination speed improver comprising a phenolic resin, to the starch-based adhesive for corrugated cardboard, the solid content of the phenolic resin in the starch-based adhesive for corrugated cardboard is 0.5 to 4.8 parts by mass per 100 parts by mass of the total solid content of the starch; A method for improving lamination speed, wherein the starch-based adhesive for corrugated cardboard does not contain any water-resistant agent other than the phenolic resin (provided that the phenolic resin is a cationic phenolic resol resin emulsion (A) obtained by condensation polymerization of phenols and aldehydes in the presence of a water-soluble or water-dispersible thermosetting resin (a) obtained by reacting a polyamide-based resin having substantially a secondary amino group with an epihalohydrin, and a water-soluble polymer (b) in the presence of the water-soluble or water-dispersible thermosetting resin (a) obtained by reacting a polyamide-based resin having a secondary amino group with an epihalohydrin).

2. 2. The method for improving a lamination speed according to claim 1, wherein the phenolic resin is a resol type phenolic resin or a novolac type phenolic resin.

Images