JP2019214716A - Sticking speed improver and method for improving - Google Patents

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

  The present invention relates to a bonding speed improver for use in a starch-based adhesive for cardboard, a starch-based adhesive for cardboard, a method for producing a cardboard sheet, a method for producing a starch-based adhesive for cardboard, and a bonding method for producing a cardboard sheet. It relates to a speed improvement method.

  In recent years, the production volume of general corrugated cardboard sheets used for cardboard boxes used for delivery of courier services and packing of moving luggage has increased rapidly due to the increase in the handling of courier services due to the rapid spread of Internet mail order. are doing.

There is a strong demand for improving the laminating speed in the production of such general corrugated cardboard sheets. In recent years, interest in environmental issues such as CO ₂ reduction has been increasing. There is a need for a method for producing.

  In order to improve the laminating speed, increasing the amount of alkali (caustic soda) added to the starch-based adhesive for corrugated cardboard to lower the gelatinization start temperature, and increasing the starch concentration to reduce the drying load And other methods have been adopted. However, in the method in which the gelatinization start temperature is lowered by increasing the alkali, if the amount of the alkali is excessively increased, the viscosity of the adhesive in the storage tank increases, so that the amount of the adhesive applied is controlled and the adhesive in the process is controlled. There are problems that it becomes difficult to flow, that the viscosity stability of the adhesive decreases, and that the viscosity increases with time, and that stable production becomes difficult.

  Further, even in the method of increasing the concentration of starch, if the concentration is too high, the viscosity in the storage tank increases, so that the above-described problem occurs, and furthermore, sufficient water for gelatinization cannot be obtained, and conversely, the adhesive strength decreases. There's a problem.

JP 2007-284568 A

  The present invention relates to a bonding speed improver for use in a starch-based adhesive for cardboard, a starch-based adhesive for cardboard, a method for producing a cardboard sheet, a method for producing a starch-based adhesive for cardboard, and a bonding method for producing a cardboard sheet. It is an object to provide a speed improvement method.

  As a result of repeated studies in view of the above problems, the present inventor has found that, by adding a phenolic resin to a starch-based adhesive for cardboard, the viscosity decreases in the storage temperature range of the storage tank, and the amount of added alkali and the starch concentration are reduced. It was found that no trouble occurred even if the temperature was increased, and that the viscosity was rapidly increased in the temperature range of the heating and drying in the laminating step, and the initial adhesive strength was developed, and the present invention was completed.

  The present invention includes the following embodiments.

  Item 1. A laminating speed improver containing a phenolic resin and used for a starch-based adhesive for cardboard.

  Item 2. The bonding speed improver according to Item 1, wherein the phenol resin is a resol-type phenol resin or a novolak-type phenol resin.

  Item 3. A starch-based adhesive for cardboard, comprising the laminating speed improver according to Item 3, 1 or 2.

  Item 4. The starch adhesive for cardboard according to Item 3, wherein the solid content of the phenolic resin is 0.5 to 50 parts by mass based on 100 parts by mass of the total solids of the starch of the starch adhesive. .

  Item 5. The starch-based adhesive for 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 based on 100 parts by mass of the solid content of the phenol resin. Agent.

  Item 10. A method for producing a corrugated cardboard sheet, comprising a step of adhering a core and a liner using a starch-based adhesive for cardboard containing the adhering speed improver according to item 6, 1 or 2.

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

  Item 8. Using a Rapid Visco Analyzer (RVA), a heating rate of 5.5 ° C./min and a rotation speed of 160 rpm. p. m. Of the starch-based adhesive for corrugated cardboard before adding the laminating speed improver was measured at a temperature at which the laminating speed improver reaches 100 RVU (Rapid Visco Analyzer Units). Item 8. The method for producing a starch-based adhesive for cardboard according to Item 7, wherein the viscosity of the agent is 200 RVU or more.

  Item 9, The heating and cooling block of the Rapid Visco Analyzer (RVA) is programmed to be constant at 90 ° C. from the start of measurement to the end of measurement, preheated to 90 ° C., and placed in an aluminum RVA standard can. A 30 g sample was taken, attached to the RVA together with the RVA standard paddle, and the paddle rotation speed was 500 r. p. m. Item 7 is a time period from the start of the viscosity measurement to the time when the viscosity reaches 150 RVU (Rapid Visco Analyzer Units) viscosity is 50 seconds or less under the condition that the stirring is started at the speed of the viscosity measurement. Or the method for producing a corrugated cardboard adhesive according to item 8.

  Item 10. A method for improving a bonding speed in the production of a cardboard sheet, comprising a step of adding the bonding speed enhancer according to Item 10, 1 or 2 to a starch-based adhesive for corrugated cardboard.

  According to the present invention, a laminating speed improver for use in a starch-based adhesive for corrugated board, a starch-based adhesive for corrugated board, a method for producing a corrugated cardboard sheet, a method for producing a starch-based adhesive for corrugated board, and a laminating method for producing a corrugated cardboard sheet A speed enhancement method is provided. In particular, by using a phenolic resin as a laminating speed improver, the starch-based adhesive for corrugated cardboard exhibits excellent functions in each of the storage temperature range of the storage tank and the temperature range in the heating and drying in the laminating step, and is thus high. It becomes possible to manufacture a corrugated cardboard sheet at a bonding speed.

The relation between the pressure bonding time and the initial adhesive strength is shown. An evaluation method of water repellency is schematically shown. It shows an increase in viscosity at 90 ° C.

  Hereinafter, the present invention will be described in detail.

  The present invention relates to a laminating speed improver for use in a starch-based adhesive for cardboard.

  In the present specification, "laminating speed improver for use in a starch-based adhesive for corrugated cardboard" means to produce a corrugated cardboard sheet at a faster laminating speed by adding to a starch-based adhesive for corrugated cardboard. A thing. In this case, it is preferable that the increase in the bonding speed is achieved without impairing the quality of the product corrugated cardboard sheet (for example, the yield excluding defective products in which the core and the liner are separated).

  As used herein, the term "starch-based adhesive" refers to an adhesive mainly composed of starch, and is an adhesive which utilizes the properties of starch, which is manifested by heating the adhesive, such as water absorption, swelling, and gelatinization. It means a functional adhesive. The “starch-based adhesive for cardboard” is, for example, a starch-based adhesive used for bonding a corrugated core base paper and a liner base paper. "Adhesive" can also be referred to as "glue" and is used interchangeably herein.

  The starch-based adhesive in which the laminating speed improver of the present invention is used can be used for producing a cardboard sheet without limitation. In one preferred embodiment of the present invention, the starch-based adhesive in which the laminating speed improver is used is used for producing general-purpose cardboard or water-repellent cardboard.

  Here, the waterproof corrugated cardboard means "waterproof corrugated cardboard" defined in the corrugated cardboard industry standard "Waterproof corrugated cardboard" M0002: 2000 (National Federation of Corrugated Cardboard Industries). Corrugated cardboard ". The term “water-repellent cardboard” refers to “corrugated cardboard that has been subjected to a surface treatment so as to repel water to form water droplets and prevent water from penetrating even if water is applied for a short period of time” specified in the corrugated cardboard industry standard M0002: 2000. Water-resistant corrugated cardboard and water-repellent cardboard are collectively referred to as “waterproof corrugated cardboard”. The “general-purpose cardboard” refers to a cardboard not provided with so-called water resistance and / or water repellency other than waterproof cardboard.

  The bonding speed improver of the present invention contains a phenol resin (phenol formaldehyde resin, phenol formaldehyde condensate) as an active ingredient. Here, the active ingredient means a component essential for the laminating speed improver of the present invention to exhibit its effect. In the present invention, the phenol resin is a resin obtained by condensing phenols and formaldehyde.

  The use of phenolic resins as a component for imparting water resistance (waterproofing agent) has been known, but the use as a laminating speed improver has not been known. In addition, the effect as a water-proofing agent tends to be inferior to other water-proofing agents.

  The phenolic resin contained in the laminating speed improver of the present invention is a resol-type phenolic resin obtained by reacting a raw material compound in the presence of a basic catalyst, or a novolak-type phenolic resin obtained by reacting a raw material compound in the presence of an acidic catalyst. Any of them may be used.

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

  Phenol resins can be produced by reacting phenols with formaldehyde in the presence of a basic or acidic catalyst.

  The molecular weight of the phenolic resin is not particularly limited as long as the improvement of the bonding speed is exhibited and the adhesive function of the starch-based adhesive is not hindered.

  The laminating speed improver of the present invention containing a phenol resin may be the solid content of the phenol resin itself, or a solution or dispersion (slurry) of the phenol resin. In the case of a solution or a dispersion, the medium is an aqueous medium mainly composed of water. The aqueous medium may contain a water-soluble organic solvent (eg, alcohols such as methanol and ethanol) in addition to the main component water. From the viewpoint that mixing with a starch-based adhesive is easy, resol-type phenol supplied as a solution or dispersion is more preferable. From the viewpoint of easiness of adding the laminating speed improver to the starch-based adhesive for cardboard, resol-type phenol using water as a solvent is more preferable. In another embodiment, a water-soluble phenol resin which has been conventionally used as a waterproofing agent for a starch-based adhesive for corrugated board can also be suitably used.

  The laminating speed improver of the present invention is for producing a corrugated cardboard sheet at a higher laminating speed by adding it to a starch-based adhesive for corrugated board. Hereinafter, the starch-based adhesive for cardboard will be described.

  The starch in the starch-based adhesive for cardboard includes a main starch composed of ungelatinized raw starch and a carrier starch obtained by completely gelatinizing modified starch by alkali and heat. The starch-based adhesive for cardboard is a dispersion in which starch is dispersed in an aqueous medium mainly composed of water.

  Examples of the constitution of a typical starch-based adhesive for cardboard include those containing water, a main starch, a carrier starch, an alkali, and a boron compound.

  The starch used in the present invention may be the starch conventionally used in starch-based adhesives for cardboard. For example, corn starch, high amylose corn starch, tapioca starch, wheat starch, potato starch, sweet potato starch, and the like, and starch obtained by oxidizing, acid-treating, esterifying, or etherifying these starches can be used. Starch can be used alone or in combination of two or more.

  In the starch-based adhesive of the present invention, the water doubling rate is usually about 1.9 to 4.5. By setting the water doubling rate to 1.9 or more, sufficient water is supplied to gelatinize the main starch, and good adhesion is obtained. Further, by setting the water ratio to 4.5 or less, the solid content concentration of the adhesive can be maintained at a predetermined value or more, and good initial adhesion can be achieved. In the present specification, the “fold water ratio” means the mass ratio of (total water amount / total starch amount) in the starch-based adhesive.

  In the starch-based adhesive of the present invention, the carrier ratio is preferably usually 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. Further, setting the carrier ratio to 30% or less is preferable from the viewpoint of obtaining appropriate viscosity and storage stability as an adhesive for cardboard.

  In one preferred embodiment of the present invention, the starch-based adhesive comprises high amylose starch as a carrier starch. In the present specification, "high amylose starch" means starch having an amylose content of 50% or more. Examples of high amylose starch include high amylose corn starch.

  When high amylose starch is contained as the carrier starch, the carrier starch may be composed of only one type of high amylose starch or may be combined with another type of starch (one or more types). From the viewpoint of improving the initial adhesion rate, the carrier starch may further include a rhizome starch in addition to the high amylose starch. Examples of the rhizome starch include tapioca starch, potato starch, and sweet potato starch.

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

  The starch-based adhesive of the present invention may further include an alkali. As the alkali used in the present invention, there can be used those conventionally used in starch-based adhesives for cardboard, such as sodium hydroxide (caustic soda) and potassium hydroxide. The alkali can be used alone or in combination of two or more. The alkali is preferably sodium hydroxide (caustic soda). The causticity of the adhesive of the present invention may be determined according to the size-making conditions in order to obtain an appropriate gelatinization temperature. In general, the amount of alkali added is preferably in the range of 0.5 to 1.5% by mass as a caustic factor. In the present specification, the “caustic rate” means a mass ratio of (amount of caustic / amount of total paste liquid) in the starch-based adhesive.

  The starch-based adhesive of the present invention contains the above laminating speed improver (phenolic resin). The content of the laminating speed improver is not particularly limited, but is preferably from 0.5 to 50 parts by mass, more preferably from 1 to 50 parts by mass, based on 100 parts by mass of the total solids of the starch with respect to the mass of the total solids of the starch. 20 parts by mass. By setting such a numerical value range, a high bonding speed improvement effect is achieved.

  In one preferred embodiment, the starch-based adhesive of the present invention is a thermosetting resin such as a ketone resin (ketone-formaldehyde resin, ketone-melamine resin) or a melamine resin as a component (waterproofing agent) for imparting water resistance. Resin, epoxy resin, thermoplastic elastomer such as styrene-butadiene rubber (SBR), and the like. However, in the present specification, the phenol resin is not included in the thermosetting resin as the water-proofing agent. Examples of the epoxy resin include epoxy compounds such as polyamide epichlorohydrin, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol polyglycidyl ether. The content of the water-proofing agent can be usually 1 to 20% by mass, and preferably 3 to 10% by mass, based on the total solid content of the starch.

  When the starch-based adhesive of the present invention contains a ketone resin as a water-proofing agent, its solid content is 100 parts by mass of the phenolic resin solid content from the viewpoint of exhibiting a higher bonding speed improving effect. Is preferably not more than 75 parts by mass.

  In another preferred embodiment, the adhesive of the present invention does not contain a waterproofing agent.

  The starch-based adhesive of the present invention can further contain a boron compound. It is considered that the boron compound develops initial adhesive strength by pseudo-crosslinking gelatinized starch. The content of the boron compound is usually about 1.5% to 3.3% by weight, preferably about 1.6% to 3.3% by weight, and preferably about 1.6% to 3.3% by weight, based on the total solid content of the starch, in terms of borax. Preferably it can be about 1.6 to 3.0% by mass, particularly preferably about 0.7 to 2.7% by mass. By setting the lower limit or more, a sufficient improvement in the initial adhesive strength is achieved. Further, when the content is not more than the above upper limit, it is possible to suppress the progress of the reaction between the borax and the starch and the occurrence of gelation and / or high viscosity.

  The starch-based adhesive of the present invention can further contain a hydrous inosilicate mineral. Examples of the hydrous inosilicate mineral include hydrous inosilicate magnesium and hydrous aluminum and magnesium inosilicate. The hydrous inosilicate mineral is included in clay minerals mainly composed of the hydrous inosilicate mineral. Examples of the clay mineral mainly containing a hydrous inosilicate mineral include so-called “sepiolite”, “attapulgite”, and “palygorskite”, and these can be used in the present invention.

  There are two methods for producing a clay mineral containing a hydrous inosilicate mineral as a main component, a dry pulverization method and a wet pulverization method. In the present invention, a hydrous inosilicate mineral produced by any of the pulverization methods is used as a main component. However, the wet pulverization method is preferred because it has a high ability to defibrate / disperse the fine fiber structure of the clay mineral and can bring out the function of the hydrous inosilicate mineral.

  In the present invention, the content of the hydrous inosilicate mineral is usually about 0.1 to 15% by mass, and preferably about 1 to 10% by mass, based on the total solid content of the starch. When the content of the hydrous inosilicate mineral is equal to or more than the lower limit, a sufficient effect of including the hydrous inosilicate mineral is recognized. When the content of the hydrated inosilicate mineral is equal to or more than the lower limit, the thixotropic property, which is one of the properties of the hydrated inosilicate mineral, is not strongly imparted, and the physical properties of the good adhesive are not improved. It is preferable from the viewpoint that it is achieved.

  The starch-based adhesive of the present invention can be prepared by a one-tank stain hole method, a two-tank stain hole method, a premix method, a no-carrier method, or the like.

  In the one-tank carrier method, a starch slurry is prepared in one tank, alkali is added to alkali-gelatinize the starch, and then water is added to dilute the alkali size, and the main starch (ungelatinized starch) is added to the diluted alkali size. ) Is added, and if necessary, borax is added and mixed. When the one-tank carrier method is adopted, the treatment temperature is preferably 30 to 45 ° C. from the viewpoint of stabilizing the finished viscosity of the adhesive and the viscosity over time, and if necessary, contains a hydrous inosilicate such as sepiolite. From the viewpoint of disintegrating and dispersing the fibers of the acid salt mineral, the number of rotations of the stirring during the gluing is preferably 1000 rpm. p. m. Above, more preferably from 1500 to 5000 r. p. m. It is. 1000r. p. m. Examples of the apparatus capable of stirring at the above rotation speed include a gluing apparatus manufactured by Circo, a gluing apparatus MREX manufactured by Mitsubishi Heavy Industries, and a gluing apparatus manufactured by Kakita Manufacturing Co., Ltd.

  As a preferable preparation method by the one-tank carrier method, for example, warm water of 30 to 45 ° C. is taken in one tank, and 3000 to 5000 r. p. m. Then, starch is added thereto, and if necessary, a hydrous inosilicate mineral is further added. After dispersing and dissolving, an alkali is added, and the mixture is stirred for 10 to 15 minutes. Then, warm water of 30 to 45 ° C is added. A method of adding starch (ungelatinized starch), and if necessary, adding borax and a water-proofing agent, and stirring for 10 to 15 minutes to produce a starch-based adhesive for corrugated cardboard.

  The timing for adding the laminating speed improver of the present invention is not particularly limited. For example, in the process of producing a starch-based adhesive for cardboard, a laminating speed improver can be added while stirring. As a specific example, after adding a starch, an alkali and a boron compound to water and stirring, a laminating speed improver can be added. In another embodiment, the starch, alkali and boron compound can be added to water to which the laminating speed improver has been added (dissolved or dispersed) after the laminating speed improver has been added to water and stirred. As still another embodiment, in the corrugated sheet manufacturing process, the adhesive can be added to a tank capable of stirring the adhesive, for example, a storage tank for supplying the adhesive to the corrugator. The laminating speed improver can be added a plurality of times during the production process of the starch-based adhesive for cardboard.

  In a preferred embodiment of the method for producing a starch-based adhesive for cardboard according to the present invention, the temperature is raised at a rate of 5.5 ° C./min and a rotational speed of 160 rpm by using a Rapid Visco Analyzer (RVA). p. m. Of the starch-based adhesive for corrugated cardboard before adding the laminating speed improver was measured at a temperature at which the laminating speed improver reaches 100 RVU (Rapid Visco Analyzer Units). The viscosity of the agent is 200 RVU or more.

  At the time of measurement, a starch-based adhesive for corrugated cardboard was used as an aluminum RVA measurement can (Perten, inner diameter) using an RVA standard can (made of aluminum) and a paddle (RVA standard Can and Paddle, manufactured by NSP Perten). 30.0 g is collected at about 36 mm and height at about 65 mm) for measurement. The starch-based adhesive for corrugated board before adding the laminating speed improver contains, for example, the above-mentioned water, main starch, carrier starch, alkali, boron compound and the like, and does not contain a phenol resin which is a laminating speed improver.

  In another preferred embodiment of the method for producing a starch-based adhesive for cardboard according to the present invention, the heating and cooling block of the RVA is programmed to be constant at 90 ° C. from immediately after the start of measurement to the end of measurement, and is preheated to 90 ° C. 30 g was sampled into a RVA standard can, and attached to the RVA together with the RVA standard paddle. p. m. Is programmed to be stirred at a speed of の, and under the conditions for starting the viscosity measurement, the time from the start of the viscosity measurement to the attainment of the 150 RVU viscosity is a viscosity rise start time of 50 seconds or less.

  Viscosity measurement using a Rapid Visco Analyzer (RVA) is performed according to standard tests such as AACC (American Association for Clinical Chemistry) -22-08 and ICC (International Color Consortium) standard No. 162. be able to.

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

  The viscosity of the starch-based adhesive for cardboard according to the present invention at the time of completion of the paste-making (immediately after the paste-making) of the starch-based adhesive for cardboard is not particularly limited. The viscosity can be appropriately set in accordance with the required operating conditions such as the amount of adhesion to the cardboard base paper and the bonding speed. The starch-based adhesive for corrugated cardboard according to the present invention, from the viewpoint of easy adjustment of the amount of adhesion to corrugated cardboard (for example, it can be adjusted so that the amount of adhesion to corrugated cardboard is not too large), and the viewpoint of viscosity stability. Is preferably 700 mPa · S or less, more preferably 600 mPa · S or less, even more preferably 500 mPa · S or less. Also, from the viewpoint of easy adjustment of the amount of the starch-based adhesive for cardboard to the cardboard base paper (for example, it can be adjusted so that the amount of adhesion to the cardboard base paper does not become too small), excessive penetration into the base paper. From the viewpoint of suppressing the viscosity and obtaining a desired strength, the viscosity (measured by a B-type viscometer) of the starch-based adhesive for corrugated cardboard immediately after making the paste is preferably 100 mPa · S or more, More preferably, it is 150 mPa · S or more.

  In the present specification, “the time point at which the paste is completed” means a time point at which all the components of the starch-based adhesive for corrugated boards, including the laminating speed improver of the present invention, are blended and sufficiently stirred. The stirring can be generally performed for about 5 to 30 minutes, preferably for about 10 to 20 minutes, and more preferably for about 15 minutes. The time within about 15 minutes after the completion of the stirring can be regarded as “the time point at which the paste is completed”.

  The present invention also provides a method for producing a corrugated cardboard sheet having an improved laminating speed. The production method of the present invention is a method for producing a corrugated cardboard sheet using a starch-based adhesive containing the above-mentioned laminating speed improver of the present invention. And bonding the core to the liner.

  The core and liner used in the method for producing a cardboard sheet of the present invention are not particularly limited. In one preferred embodiment of the present invention, a core and a liner used for producing general-purpose cardboard or water-repellent cardboard can be used. This is from the viewpoint that the starch-based adhesive for corrugated cardboard quickly penetrates into the liner, so that the so-called "glue feet" tend to be deep and high adhesive strength is exhibited.

  The liner used for water-resistant corrugated cardboard has a relatively strong water repellency on the adhesive surface with the core. On the other hand, the liner used for general cardboard is not provided with water repellency, and the water repellent cardboard is not provided with water repellency as strong as water resistant cardboard.

  The preferable water repellency of the adhesive surface between the core and the liner used in the method for producing a corrugated cardboard sheet of the present invention is the "mixture for wetting tension test" No. 1 specified in JIS K6768. 48.0 (liquid having a wet tension of 48.0 mN / m) was dropped from a position at a height of 5.0 to 7.0 mm from the liner as a droplet of 0.020 g to 0.040 g using a Pasteur pipette or the like. At this time, the time required for the droplet height to become 0.50 mm or less can be used as a guide (see FIG. 2). The time required for the droplet height to be 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.

  The method for producing a corrugated cardboard sheet of the present invention can be performed using a commonly used corrugator. That is, for example, using a corrugator having at least a means for adhering the starch-based adhesive for cardboard to the glue roll and the glue roll, the top edge of the corrugated core paper is brought into contact with the glue roll. A step of applying a starch-based adhesive for cardboard of the present invention to the top edge, and a step of laminating liner paper on one or both sides of the core coated with the starch-based adhesive for cardboard of the present invention It can be manufactured by a sheet manufacturing method. For example, using the starch adhesive of the present invention, a corrugated cardboard sheet can be produced by a corrugator equipped with a gravure roll.

  The gluing machine for corrugated cardboard sheets is composed of an applicator roll and a doctor roll. Applicator rolls (glue rolls) include various types of metering rolls, satin finish rolls, and gravure rolls. The metering roll and the satin finish roll are gluing rolls having a smooth roll surface, and the gravure roll is a gluing roll having a large number of recesses (cells) provided on the roll surface. The adhesive adhering to the roll surface is picked up by rotation on the roll dipped in the glue vat, and excess adhesive adhering to the roll surface is scraped off by the doctor roll. In the case of a roll having a smooth surface, the adhesive whose viscosity has been reduced is not sufficiently picked up on the roll, and the application of the adhesive becomes uneven, so that the adhesive is applied to the spots and affects the adhesive performance. On the other hand, in the case of a gravure roll, the adhesive enters into the dents (cells) cut in the roll surface, so that even the adhesive whose viscosity has been reduced can be easily picked up, and a uniform adhesive can be applied.

  In the production of corrugated cardboard, heating after laminating the core and the liner causes (1) swelling of ungelatinized starch, (2) thickening of adhesive, and (3) gelatinization of ungelatinized starch (4). It is considered that the bonding is completed through steps such as drying of the adhesive. Heating is usually performed using a hot plate or the like. If the bonding is insufficient, the core and the liner may peel off due to the pressure on the bonding portion during cutting such as cutting or slitting. Therefore, in order to make the bonding sufficient, the laminating speed (line speed) is adjusted to adjust the heating time by a hot plate or the like.

  Although the principle is not clear, by blending the laminating speed improver of the present invention with a starch-based adhesive for corrugated cardboard, the viscosity is appropriately reduced in a storage tank storage temperature range (for example, 45 ° C. or lower). No trouble occurs when adding an alkali or increasing the starch content, and heating and drying in the bonding step (for example, a heating step at an apparatus temperature of 160 ° C. or higher, more preferably 180 ° C. or higher, In the temperature range of the step (sheet temperature is 60 ° C. or more, more preferably 65 ° C. or more), the viscosity is rapidly increased and the initial adhesive strength is exhibited. Therefore, by adding the laminating speed improver to the starch-based adhesive for corrugated cardboard, the laminating speed in the production of a corrugated cardboard sheet can be improved.

  Accordingly, the present invention also provides a method for improving the bonding speed in the production of a corrugated cardboard sheet, which comprises a step of adding a laminating speed improver to a starch-based adhesive for corrugated cardboard. The starch-based adhesive for corrugated board before adding the laminating speed improver contains, for example, the above-mentioned water, main starch, carrier starch, alkali, boron compound and the like, and does not contain a phenol resin which is a laminating speed improver.

  The production of a corrugated cardboard sheet which is not limited is an object of the laminating speed improving method. Specifically, the production of cardboard for general use, the production of water-repellent cardboard, and the production of water-repellent cardboard using a starch-based adhesive containing a water-proofing agent other than the phenolic resin are targeted.

<Example>
Example 1
<Preparation of carrier part>
600 g of water is placed in a 1 L stainless steel mug, heated to 60 ° C. using a water bath, and 72 g of commercially available starch-based adhesive for starch-based adhesive for cardboard (Oji Corn Starch Co., Ltd.) is added. Was dispersed with a stirrer Robomix (4500 rpm) manufactured by Co., Ltd. to prepare a starch slurry. 50 g of a 25% sodium hydroxide solution was added to the starch slurry with stirring, and the mixture was stirred for 15 minutes to produce a carrier starch as a starch-based adhesive for cardboard.

<Preparation of main part>
Take 840 g of water in a 3 L stainless steel mug, heat to 35 ° C. using a water bath, add 485 g of commercially available cornstarch (manufactured by Oji Cornstarch Co., Ltd.), and stirrer Robomix manufactured by Tokushu Kika Kogyo Co., Ltd. (4500 rpm) to prepare a main starch.

<Preparation of starch adhesive for cardboard>
While stirring the obtained main starch with the stirrer (4000 rpm), the carrier starch was charged at a rate of 120 g / min using a tube pump. The time required for introduction was 6 minutes.

  While continuing stirring, pentahydrate borax was added.

  Further, a phenol resin (PX-24, manufactured by Aika Kogyo Co., Ltd.) was added to the mixture in the amount shown in Table 1 while stirring was continued, followed by stirring for 15 minutes.

  The viscosity of the obtained adhesive was 280 mPa · S (measured with a B-type viscometer).

  In addition, 30 g of the obtained adhesive was collected in an aluminum cup for measuring RVA (Rapid Visco Analyzer, manufactured by NEWPORT SCIENTIFIC), and the temperature was raised at a rate of 5.5 ° C. and the number of rotations was 160 r. p. m. And a temperature-viscosity curve until 500 RVU was obtained. From the obtained curve, 100 RVU attained temperature was measured.

<Initial adhesive strength>
A 5 g / m ² absolutely dry cardboard adhesive is applied to a 50 mm × 85 mm single-sided cardboard for general use (liner basis weight, 280 g / core basis weight: 180 g), and applied to a pin tester with a load cell. I set it. A liner (basis weight: 280 g) was placed thereon, and pressed with a hot plate (180 ° C.) having a weight of 1 kg. The pressure bonding time was 2 seconds, 3 seconds or 5 seconds. In each case, the liner and the single-sided cardboard were immediately peeled off after the pressure bonding, and the strength at that time was measured as an initial adhesive strength by a load cell.

Examples 2 to 5 and Comparative Example Initial adhesion strength was the same as in Example 1 except that the addition amount of the phenolic resin and the addition amount of the ketone resin (waterproofing agent A (manufactured by Oji Cornstarch Co., Ltd.)) were as shown in Table 1. Immediately after the addition of the phenol resin, the ketone resin was added while stirring the cardboard adhesive similarly to the phenol resin.

  The results are shown in Table 1 and FIG.

Comparative Example 2
<Manufacture of one-tank type starch adhesive for corrugated board>
Take 1010 g of water in a 3 L stainless steel mug, heat to 35 ° C. using a water bath, add 99 g of corn starch for starch-based adhesive for cardboard (OHP-C153 manufactured by Oji Corn Starch Co., Ltd.), and specialize. 55 g of a 25% strength sodium hydroxide solution was added to the starch slurry while stirring with a stirrer Robomix (4500 rpm) manufactured by Kogyo Co., Ltd., and the mixture was stirred for 15 minutes. While continuing stirring, 700 g of water was added, 545 g of commercially available corn starch (manufactured by Oji Corn Starch Co., Ltd.) was added, 8.5 g of borax decahydrate was added, and the mixture was stirred for 15 minutes for starch-based cardboard. An adhesive was produced. The viscosity of the obtained adhesive was 240 mPa · s (measured with a B-type viscometer). The obtained adhesive was subjected to 600 r. p. m. The mixture was stored while stirring, and RVA measurement and measurement of the initial adhesive strength described later were performed.

<Initial adhesive strength>
A 5 g / m ² absolutely dry cardboard adhesive is applied to a 50 mm × 85 mm single-sided cardboard for general use (liner basis weight, 280 g / core basis weight: 180 g), and applied to a pin tester with a load cell. I set it. A liner (basis weight: 280 g) was placed thereon, and pressed with a hot plate (180 ° C.) having a weight of 1 kg. The pressure bonding time was 3 seconds, 5 seconds or 7 seconds. In each case, the liner and the single-sided cardboard were immediately peeled off after the pressure bonding, and the strength at that time was measured as the initial adhesive strength by a load cell.

<Increase in viscosity at 90 ° C. using RVA>
The heating / cooling block of 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 was preheated to 90 ° C. 30 g of the adhesive obtained above was sampled into an RVA standard can (aluminum, Perten) and mounted on the RVA together with the RVA standard paddle. p. m. It was programmed to stir at a speed of.

  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 the last added chemical, decahydrate borax, in the process of preparing the starch-based adhesive for cardboard.

Example 7
A starch-based adhesive was prepared in the same manner as in Comparative Example 2 by a one-tank method. Five minutes after the addition of the borosilicate of decahydrate, 32.2 g of resol-type water-soluble phenol resin (trade name: PR-967 (non-volatile content: 40%, manufactured by Sumitomo Bakelite Co., Ltd.)) was added in the form. This amount is 5% by mass based on the total starch amount (the total amount of the carrier starch and the main starch). The viscosity at the time when the stirring for 15 minutes was completed after adding the borax was 230 mPa · S. Thereafter, the initial adhesive strength was measured in the same manner as in Comparative Example 2. The increase in viscosity at 90 ° C. was measured in the same manner as in Comparative Example 2. In addition, this measurement was performed 30 minutes and 150 minutes after adding the phenol resin which is a chemical added last when manufacturing the adhesive for cardboards of Example 7.

Example 8
Except that the amount of the resol-type water-soluble phenol resin was changed to 64.4 g (10% based on the total starch amount), a starch-based adhesive was produced, the initial adhesive strength was measured, and RVA measurements were made. The viscosity at the time when the stirring for 15 minutes was completed after adding the borax was 210 mPa · S.

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

  The starch-based adhesive for cardboard containing the laminating speed improver of the present invention tended to have a short viscosity increase start time. It is presumed that the initial adhesive strength is improved and the laminating speed can be improved due to the short time at which the viscosity rise starts. In addition, the starch-based adhesive for corrugated cardboard containing the laminating speed improver of the present invention also showed a tendency that the decrease in the initial adhesive strength was small even after a lapse of time from the gluing. Since the decrease in the initial adhesive strength is small, the pot life can be expected to be long.

Claims (10)

  A laminating speed improver containing a phenolic resin for use in a starch adhesive for cardboard.   The laminating speed improver according to claim 1, wherein the phenol resin is a resol type phenol resin or a novolak type phenol resin.   A starch-based adhesive for cardboard, comprising the laminating speed improver according to claim 1.   The starch adhesive for cardboard according to claim 3, wherein the phenolic resin has a solid content of 0.5 to 50 parts by mass with respect to 100 parts by mass of the total solids of the starch of the starch adhesive.   The starch adhesive for cardboard according to claim 3 or 4, further comprising a ketone resin, wherein the solid content of the ketone resin is 75 parts by mass or less based on 100 parts by mass of the solid content of the phenol resin.   A method for producing a corrugated cardboard sheet, comprising a step of laminating a core and a liner using the starch adhesive for corrugated cardboard, comprising the laminating speed improver according to claim 1 or 2.   A method for producing a starch-based adhesive for cardboard, comprising a step of adding the laminating speed improver according to claim 1 to a starch-based adhesive for cardboard.   Using a rapid visco analyzer (Rapid Visco Analyzer: RVA), the temperature was raised at a rate of 5.5 ° C./min, and the number of revolutions was 160 rpm. p. m. Of the starch-based adhesive for corrugated cardboard before adding the laminating speed improver was measured at a temperature at which the laminating speed improver reaches 100 RVU (Rapid Visco Analyzer Units). The method for producing a starch-based adhesive for cardboard according to claim 7, wherein the viscosity of the agent is 200 RVU or more.   The heating and cooling block of the Rapid Visco Analyzer (RVA) is programmed to be constant at 90 ° C. immediately after the start of the measurement to the end of the measurement, preheated to 90 ° C., and 30 g is sampled in an aluminum RVA standard can. , And RVA standard paddle, and attached to the RVA. p. m. The time from the start of viscosity measurement to the arrival of 150 RVU (Rapid Visco Analyzer Units) viscosity is a viscosity rise start time of 50 seconds or less under a condition programmed to be stirred at a speed of and starting viscosity measurement. 9. The method for producing a cardboard adhesive according to 7 or 8.   A method for improving a laminating speed in the production of a corrugated cardboard sheet, comprising a step of adding the laminating speed improver according to claim 1 or 2 to a starch-based adhesive for corrugated cardboard.