KR20150033412A - Method for preparing modified starch with low viscosity, modified starch with low viscosity prepared thereby, composition comprising the modified starch for paper surface sizing, and paper having a surface treated with the composition - Google Patents

Abstract

The present invention relates to a method for preparing modified starch with low viscosity by continuously modifying starch using an oxidizing agent and an esterifying agent, the modified starch with low viscosity prepared thereby, a composition containing the modified starch for paper surface sizing, and paper having a surface treated with the composition. The modified starch manufactured according to the present invention has excellent liquidity after cooking, superior viscosity stability with the passage of time, and markedly low viscosity compared to the existing oxidized starch which has been used in a surface sizing process during the manufacture of paper, thereby being able to increase the solid content in the composition (in other words, starch concentration) if using the modified starch as an active component for a liquid composition for paper surface sizing, and thus the amount of moisture which has to be evaporated when coating an equal amount of starch on the paper surface can be drastically decreased, thereby being able to reduce energy requirement when drying the paper.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low viscosity modified starch, a low viscosity modified starch prepared by the same, a composition for paper surface sizing including the modified starch and a paper surface- PREPARED THEREBY, COMPOSITION COMPRISING THE MODIFIED STARCH FOR PAPER SURFACE SIZING, AND PAPER HAVING A SURFACE TREATED WITH THE COMPOSITION}

The present invention relates to a method for producing a low viscosity modified starch by continuously modifying starch using an oxidizing agent and an esterifying agent, a low viscosity modified starch prepared by the method, a composition for paper surface sizing including the modified starch, The modified starch prepared according to the present invention has excellent fluidity and viscosity stability over time after cooking as compared with the conventional oxidized starch used in the surface sizing process in paper production, It is possible to increase the solids content (i.e., starch concentration) of the composition when it is used as an active ingredient in a liquid composition for paper surface sizing, and thus to significantly reduce the amount of water that must be evaporated upon application of the same amount of starch to the paper surface Which can reduce the energy requirement when drying the paper.

The paper surface sizing process is a process of applying a surface sizing solution to a dried paper to improve the surface and strength of the paper and is widely used in the field of paper including industrial paper (for example, cardboard, have. The most commonly used material in the paper surface sizing process is starch, and the surface sizing solution using starch is applied using a size press after the paper drying process. The amount of surface sizing starch applied to the paper is about 2 to 5% of the total dry weight of the paper, which is the largest amount of filler in the additive excluding pulp fibers at the time of papermaking.

The most commonly used starch-based surface sizing solutions are modified starches. Since starch is insoluble in cold water, starch is converted into a liquid phase by applying heat to the starch slurry to be used for surface sizing. The unmodified starch is a polymer substance having a polymerization degree of 800 or higher. The viscosity of the lecithin is high, It is difficult to use it in the surface sizing process, so it is necessary to use modified starch such as reducing the molecular weight.

Oxidation reactions have mainly been used in the denaturation treatment to reduce the molecular weight of starch. Oxidized starch is advantageous in that it can be easily handled, has superior stability in stability, and increases the internal bond strength. However, it has a disadvantage in that the opacity decreases greatly and the risk of occurrence of the fingers is high because the starch solution penetrates deeply into the paper.

When the solid content of the starch hydrolyzate used for the surface sizing solution is increased, the penetration of starch in the paper paper is reduced, and the amount of starch remaining on the surface of the paper is increased to increase the porosity, thereby increasing the opacity. However, when the solid content of oxidized starch solution is increased, the viscosity of the solution increases, so that it is difficult to control the whole volume to be applied with the paper, and aging occurs easily, and the viscosity of the sizing solution increases due to deterioration of the stability with time.

Korean Patent Registration No. 10-0204288 discloses a method for preparing starch by mixing a starch with persulfate, calcium hypochlorite, sodium hypochlorite, hydrogen peroxide or benzoyl peroxide in combination and irradiating the mixture with radiation to maintain excellent viscosity stability, There is disclosed a method for producing modified starch having an excellent coloring degree and / or a low foaming amount. However, in order to produce modified starch by this method, wet reaction and dry reaction are both required, a dry reaction facility including irradiation in addition to a wet reaction facility must be added in order to perform this, which causes considerable equipment cost.

On the other hand, a drying process is further required for the paper with increased water content due to the application of the starch-like solution for surface sizing. Drying is usually carried out using steam in a paper machine drying process. At this time, if the concentration of the liquor (that is, the solid content) can be increased under the same application amount condition, the amount of water to be evaporated can be reduced and accordingly the consumption amount of energy necessary for evaporating water (that is, . For example, if 50 g of a 10% solids solution is used to apply 5 g of starch, 45 g of water will be applied to the paper, but if the solids content is increased to 15%, the total amount of the applied solution will be about 33.3 g And thus the amount of water to be evaporated is reduced to about 28.3 grams, so that the energy required to evaporate about 16.7 grams of water can be saved. That is, one-third of dry energy can be saved when 10% solids content solution is used.

Korean Patent Laid-Open Publication No. 10-2013-0046279 discloses a method for producing oxidized starch by continuously treating a starch solution with sodium hypochlorite (first oxidizing agent) and persulfate (second oxidizing agent) The hydrolyzate of the oxidized starch has a lower viscosity than the conventional oxidized starch hydrolyzate and can increase the solid content. However, in this method, the solid content that can be obtained while maintaining the same viscosity as that of the existing starch hydrolyzate has a limit of only about 13% at maximum.

Therefore, it is required to develop a new technology capable of producing modified starch suitable for use in paper surface sizing because it can exhibit low viscosity and excellent stability even when the solid content of the starch solution is increased to a large extent.

Disclosure of the Invention The present invention has been made to solve the problems of the prior art as described above, and it is an object of the present invention to provide a starch-modified starch composition which has a low viscosity and a good stability over time, A method for producing the same, a composition for paper surface sizing comprising the same, and a paper surface-treated with the composition.

In order to accomplish the above object, the present invention provides a method for producing starch, comprising: (1) preparing a starch solution by mixing starch and water; (2) oxidizing the starch by adding an oxidizing agent to the starch solution; (3) adding an esterifying agent to the resultant solution of step (2) to further modify the oxidized starch; And (4) removing water from the resultant solution of the step (3).

According to another aspect of the present invention, there is provided a low viscosity modified starch which is produced by the modified starch preparation method of the present invention and has a viscosity (50 캜) of the hosue of 30 cps or less based on 15% by weight of solid concentration.

According to another aspect of the present invention, there is provided a composition for paper surface sizing comprising the modified starch produced by the modified starch preparation method of the present invention.

According to another aspect of the present invention, there is provided a paper characterized by being surface-treated with the composition for paper-surface sizing of the present invention.

The modified starch prepared according to the present invention is superior in stability to the fluidity and viscosity over time after cooking and has a remarkably low viscosity compared to the existing oxidized starch used in the surface sizing process in paper production, It is possible to remarkably increase the solid content (i.e., starch concentration) of the composition when it is used as an active ingredient in a liquid composition for disposal, and thus to significantly reduce the amount of water to be evaporated upon application of the same amount of starch to the paper surface, The energy demand can be reduced.

Hereinafter, the present invention will be described in more detail.

The method for producing modified starch according to the present invention comprises the steps of: (1) preparing a starch solution by mixing starch and water; (2) oxidizing the starch by adding an oxidizing agent to the starch solution; (3) adding an esterifying agent to the resultant solution of step (2) to further modify the oxidized starch; And (4) removing moisture from the resultant solution of the step (3).

Examples of the starch used in step (1) of the modified starch preparation method of the present invention include starches such as common starch such as corn, waxy corn, tapioca, potato, sweet potato, rice, and wheat. More specifically, the starch may be selected from the group consisting of corn starch, waxy corn starch, tapioca starch, potato starch, potato starch, sweet potato starch, rice starch, wheat starch, and mixtures thereof. There is no particular limitation on the concentration of the starch in the starch solution. For example, it may be appropriately selected within a concentration range of 10 to 50% by weight.

In the modified starch preparation method of the present invention, an oxidizing agent is added to the starch solution prepared in the step (1) to oxidize the starch (step (2)). As the oxidizing agent, an oxidizing agent usually used for the oxidation of starch can be used. More specifically, the oxidizing agent may be selected from the group consisting of sodium hypochlorite, hydrogen peroxide, and mixtures thereof, more preferably sodium hypochlorite. The oxidizing agent is preferably used in an amount of 1 to 6% by weight, more preferably 1 to 6% by weight, based on 100% by weight of the starch solids in the starch used, based on the weight of the effective element (oxidizing agent for sodium hypochlorite and oxygen for hydrogen peroxide) By weight, more preferably 2 to 4% by weight, and still more preferably 2.5 to 3.5% by weight. If the amount of the oxidizing agent used is less than 1 wt% based on the above-mentioned criteria, the viscosity of the surface sizing liquid may be increased during the gelatinization of the oxidized starch, so that it may be difficult to apply to the paper manufacturing process. The COD (chemical oxygen demand) of the generated wastewater increases, resulting in a problem that the production efficiency is lowered and the wastewater treatment cost is increased.

The oxidation reaction of the starch by the oxidizing agent is not particularly limited, but specifically, it is carried out under reaction conditions of 30 to 50 DEG C and pH 8 to 12 for 1 to 6 hours, preferably 2 to 4 hours . Maintaining the pH of the oxidation reaction at 8 to 12 is preferable in terms of reaction efficiency and stability. In the case of the oxidation reaction time, there is no problem in completing the normal reaction even if it is longer than the above, but there may be a disadvantage that the process time is lengthened.

In the modified starch preparation method of the present invention, an esterifying agent is added to the solution resulting from the oxidation reaction of the starch in the step (2) to further modify the oxidized starch [Step (3)]. As the esterifying agent, it is preferable to use one selected from the group consisting of acetic acid, acrylic acid, maleic anhydride, fumaric acid, itaconic acid, vinyl acetate and mixtures thereof, more preferably maleic anhydride, vinyl acetate and mixtures thereof Can be used. The esterifying agent is preferably used in an amount of 0.01 to 2% by weight, more preferably 0.05 to 1.5% by weight, still more preferably 0.1 to 1.5% by weight, most preferably 0.1 to 1.5% by weight, based on 100% by weight of the starch solids in the starch used. May be used in an amount of 0.3 to 1% by weight. If the amount of the esterifying agent used is less than 0.01% by weight based on the above-mentioned criteria, the aging of the starch after the gelatinization proceeds rapidly and the viscosity stability of the starch may deteriorate over time. If the amount is more than 2% by weight, not.

The denaturation reaction of the oxidized starch by the esterifying agent is not particularly limited, but specifically, the reaction is carried out for 10 minutes to 3 hours under the reaction conditions of 30 ° C to 50 ° C, pH 8 to 12 (more preferably pH 7 to 10) , Preferably 30 minutes to 1 hour. The esterification reaction may be carried out under the same or different conditions within the above-described range of the oxidation reaction carried out. If the temperature during the esterification reaction is less than 30 ° C, the reaction does not occur well and the reaction efficiency may be lowered. If the temperature is higher than 50 ° C, starch hydrolysis in the slurry may occur, resulting in increased viscosity and poor dehydration. On the other hand, maintaining the pH of the esterification reaction at 7 to 10 is preferable in terms of reaction efficiency and stability, and even if the esterification reaction time is longer than that, there is no problem in completing the normal reaction, Can be.

In a preferred embodiment of the method for producing modified starch according to the present invention, an oxidizing starch is further added by adding an esterifying agent to the resultant solution of step (2) continuously, following the oxidation process of starch in step (2) The esterification step of step (3) is carried out. Here, the 'oxidation process of the (2) step and the esterification process of the (3) step are carried out continuously' means that the oxidant and the esterifying agent are not added to the starch solution at the same time, Does not mean that the process and the esterification process must be carried out without interruption in time.

In the modified starch preparation method of the present invention, water is removed from the solution resulting from the esterification reaction in the step (3) (step (4)). At this time, the refining process may be optionally performed on the resultant solution of the step (3) before the step (4) after the step (3). Removal of moisture in step (4) can be carried out through a dehydration and / or drying process. For the dehydration process, a general method such as vacuum dehydration, centrifugal dehydration, compression dehydration and the like can be used, and preferably vacuum dehydration or centrifugal dehydration can be used, but the present invention is not limited thereto. As the drying step, a general method such as hot air drying, cold air drying, drum drying, vacuum drying, infrared drying, vacuum drying, high frequency drying and ultrasonic drying can be used, and preferably hot air drying can be used. no. In order to remove moisture, either the dehydration process or the drying process may be performed, or both processes may be performed. Whether or not each process is performed and specific means may be appropriately selected for effective moisture removal.

The water removal step is preferably carried out until the moisture content in the final product (i.e., the oxidized and esterified modified starch product) is within the range of 5 to 20% by weight. This moisture content level is generally the level of content used in the art. If the moisture content in the final product is more than 20% by weight, aggregation may occur during storage. If the moisture content is less than 5% by weight, drying cost may be increased and dust generation may be increased.

The modified starch hydrolyzate prepared according to the method for producing modified starch of the present invention exhibits a lower viscosity at the same concentration as compared with the conventional oxidized starch (obtained by treating raw starch with only 100% oxidizing agent) This means that it is possible to increase the solids content more than the existing oxidized starch sol at the same viscosity. Therefore, when the modified starch prepared according to the present invention is applied to a composition for paper surface sizing during the papermaking process, it is possible to further increase the content of starch solids contained in the composition while maintaining the viscosity of the conventional composition for sizing, The strength can be improved and the effect of reducing the amount of energy required for drying the paper in the paper making process can be obtained.

This effect is consistent with the main purpose of increasing the concentration of the surface sizing fluid in the papermaking process. That is, if the concentration of the surface sizing liquid (i.e., the modified starch solids content) is increased, the amount of water re-absorbed by the paper when the same amount of starch is applied to the paper can be reduced, Not only does it reduce the cause of fingerprints, but also reduces the amount of steam used to dry the paper, which has the benefit of greater energy savings. For example, in order to apply 40 kg of starch per ton of paper product, the total amount of the surface sizing liquid transferred to paper is 333.3 kg when the conventional oxidized starch (lyophilic concentration: 12%) is used, whereas the modified starch (Which can be up to 16%), the total amount of surface sizing solution transferred to the paper is 250.0 kg. Therefore, when the modified starch of the present invention is used, it is possible to evaporate about 83.3 kg of water, which is the difference between the total amount of the surface sizing liquid, to an excellent effect of reducing the drying energy required for the drying process after the size press by about 7% , Which is particularly desirable in that it can greatly reduce energy in the paper industry, an energy consuming industry.

Therefore, according to another aspect of the present invention, there is provided a low viscosity modified starch produced by the method for producing modified starch of the present invention. The low viscosity modified starch according to a particularly preferred embodiment of the present invention has a viscosity (50 캜) of the hosue of 30 cps or less (for example, 10 cps to 30 cps), more preferably 28 cps or less , And even more preferably 25 cps or less.

Preferably, the low viscosity modified starch of the present invention has a viscosity (50 DEG C) of 10 mass% or less (e.g., 1 cps to 10 cps), more preferably 8 cps or less, And even more preferably 7 cps or less.

In the present invention, the viscosity of the supernatant was determined by diluting the starch with water to have a solid content of the starch, heating the mixture at 95 ° C for 30 minutes, heating the supernatant at 50 ° C using Brookfield low shear viscometer (Brookfield Engineering Inc. Florida) .

According to still another aspect of the present invention, there is provided a paper for surface sizing comprising a modified starch prepared by the method for producing modified starch of the present invention, and a paper characterized by being surface-treated with the paper surface sizing composition. The modified starch content of the present invention contained in the paper surface sizing composition of the present invention is preferably 10 to 16% by weight, more preferably 12 to 16% by weight, still more preferably 14 to 20% by weight, 16% by weight.

Hereinafter, the present invention will be described in more detail with reference to examples. However, these embodiments are only for illustrating the present invention, and the scope of the present invention should not be construed as being limited by these embodiments.

[ Example ]

Oxidized starch  Manufacture of A0 and A1

Sodium hypochlorite, which is an oxidizing agent, was added to general corn starch solution (Samyang Genex Co., Ltd., concentration of 40% by weight) in the amount shown in Table 1 and oxidized in a wet process at a reaction temperature of 45 ° C, a reaction pH of 10, and a reaction time of 3 hours After the reaction, the starch solution was dehydrated as a result of the wet oxidation reaction and hot-air dried to prepare oxidized starches A0 and A1 having a water content of 10% by weight.

Preparation of Modified Starches A2 to A5

Sodium hypochlorite, which is an oxidizing agent, was added to general corn starch solution (Samyang Genex Co., Ltd., concentration of 40% by weight) in the amount shown in Table 1 and oxidized in a wet process at a reaction temperature of 45 ° C, a reaction pH of 10, and a reaction time of 3 hours The reaction was carried out. After the completion of the oxidation reaction, a 3 wt% caustic soda solution was added to the resultant solution to adjust the pH to 9.0, and the esterifying agent of the type and amount shown in Table 1 was continuously added to the resultant solution, For 30 minutes to perform an esterification reaction to denature oxidized starch. After the denaturation reaction, the resulting solution was dehydrated in vacuo and dried in a hot air drier at 50 占 폚 for 24 hours to prepare modified starches A2 to A5 having a water content of 5 to 10% by weight.

The viscosity of the starches A0 to A5 prepared as described above was measured by the following method. The prepared starch was diluted with water to a solids content of 10% by weight or 15% by weight and heated at 95 캜 for 30 minutes to prepare a supernatant. The resulting supernatant was subjected to a Brookfield low shear viscometer Florida) was used to measure the viscosity. The viscosity measurement results are shown in Table 1 below.

As can be seen in Table 1, the amount of oxidizing agent was reduced and the viscosity of A2 to A5 using the esterifying agent was lower than that of A0 which used 3.5 wt% of sodium hypochlorite alone. In particular, A2 and A4 showed lower viscosity than Al using 7.0% by weight of sodium hypochlorite.

On the other hand, the following test was carried out to investigate the viscosity change of the prepared starch with time. The oxidized starches A0 and A1 applied only with conventional sodium hypochlorite and the modified starches A2 and A4 subjected to the continuous esterification reaction after the oxidation reaction according to the present invention were each diluted to a concentration of 15% After the gelation, the change in viscosity of the starch with time at 50 ° C was measured using a low shear viscometer (Brookfield Engineering Inc. Florida). The measurement results are shown in Table 2 below.

As can be seen from the above Table 2, the modified starches A2 and A4 prepared according to the present invention, compared with the oxidized starches A0 and A1 applied only with sodium hypochlorite, exhibit remarkably high viscosity Low. That is, the initial viscosity of the modified starch according to the present invention was significantly lower than that of the conventional oxidized starch, and the viscosity stability with time was also excellent. In particular, the viscosity of the modified starch according to the present invention was remarkably low and the viscosity stability with time was also excellent even when compared with the case of A1 in which the amount of sodium hypochlorite was increased twice as much as the A0.

On the other hand, the following test was conducted to examine the drying efficiency after the sizing solution containing the prepared starch was applied on the paper surface. The oxidized starch A0 applied only with conventional sodium hypochlorite and the modified starch A4 subjected to the continuous esterification reaction after the oxidation reaction according to the present invention were diluted to the solid concentration shown in the following Table 3, , the basis weight 200g / m and then the amount of pick-up (pick-up) on the liner support surface of the ^second coating to be 5g / m ^2, the water meter (aND MX-50, Japan) with a water content of the paper surface to the liner using a 5 wt. %, And the drying efficiency of the coated starch on the surface of the liner paper was measured. The measurement results are shown in Table 3 below.

As can be seen from Table 3, the modified starch A4 according to the present invention shows a decrease in the drying time by increasing the concentration of starch solids from 10 wt% to 16 wt%. In the case of oxidized starch AO, the drying time was reduced by increasing the solid concentration from 10 wt% to 12 wt%. However, when the solid content was increased to 14 wt% or more, the viscosity of the starch solution could be increased, And the drying time according to the concentration of starch could not be measured. Thus, when the composition for paper surface sizing is prepared using the modified starch prepared according to the present invention, the solid concentration thereof is increased by 4% by weight or more relative to the maximum concentration (12% level) % Or more, thereby shortening the drying time of the paper. Therefore, it is possible to reduce the amount of steam used for drying energy at a general paper production site. Therefore, it is possible to obtain an effect of reducing the energy required for drying after paper surface sizing using starch in the papermaking process.

Claims (9)

(1) preparing a starch solution by mixing starch and water;
(2) oxidizing the starch by adding an oxidizing agent to the starch solution;
(3) adding an esterifying agent to the resultant solution of step (2) to further modify the oxidized starch; And
(4) removing moisture from the resultant solution of step (3)
Modified starch. The method according to claim 1, wherein the starch is selected from the group consisting of corn starch, waxy corn starch, tapioca starch, potato starch, potato starch, sweet potato starch, rice starch, wheat starch, ≪ / RTI > The process according to claim 1, wherein the oxidizing agent is selected from the group consisting of sodium hypochlorite, hydrogen peroxide, and mixtures thereof. The process for producing modified starch according to claim 1, wherein the esterifying agent is selected from the group consisting of acetic acid, acrylic acid, maleic anhydride, fumaric acid, itaconic acid, vinyl acetate, and mixtures thereof. The method according to claim 1, wherein the esterification step of step (3) is carried out continuously following the oxidation step of step (2). 6. A low viscosity modified starch prepared by the method of any one of claims 1 to 5 and having a viscosity (50 DEG C) of the hosiemy of 30 cps or less based on 15% by weight of solids concentration. A composition for paper surface sizing comprising modified starch prepared by the method of any one of claims 1 to 5. The composition for paper surface sizing according to claim 7, wherein the content of the modified starch is 10 to 16% by weight based on the total weight of the composition. Characterized in that it is surface-treated with the paper surface sizing composition of claim 7.