JPH08120235A - Interlaminar adhesive for paperboard or the like - Google Patents

Abstract

PURPOSE: To obtain an interlaminar adhesive which can bind with a pulp slurry as a paperstock at good efficiency, scarcely escapes from the system, and can promote the penetration of the size into among paper layers in drying to improve the peeling strength and strength in the z axis of the paper. CONSTITUTION: This adhesive is one added to a paperstock when the paperstock is made into paper, used to bond sheets of e.g. paperboard to each other and comprising a starch derivative obtained by acetylating starch with a slightly lowered molecular weight or by esterifying the starch with a 4-22 C dicarboxylic acid anhydride selected from the group consisting of aliphatic, aromatic, alicyclic and bicyclic aliphatic dicarboxylic acid anhydrides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified starch which is used as a sizing agent when making a sheet such as a paperboard having a multi-layer structure, and its purpose is to form an effective adhesive layer and to accompany it. It is an object of the present invention to provide an excellent sizing agent which has a stable adhesive strength, an improved strength in the Z-axis direction of a paperboard, and an improved yield of starch in the paper layer, which is less likely to flow into the drainage system.

[0002]

2. Description of the Related Art Conventionally, many starches used as sizing agents in this field are low-priced raw starches, but urea phosphate esterified starches (special Kaihei 3-90695), etherified starch,
The use of modified starch such as cationized starch (Japanese Patent Publication No. 51-46852) and acetylated starch (Japanese Patent Publication No. 62-279) has been proposed and some are actually used. Even if these modified starches are used in the form of slurries, the gelatinization temperature is lowered by various modifications, so the starch granules sprayed and applied in the combining step during papermaking tend to become paste during the drying step. Since it is easier to obtain a stable adhesive ability than raw starch, it is increasingly used.

[0003]

In a high-speed paper machine having a high paper-making speed, starch as an interlayer adhesive used when forming a sheet such as paperboard in order to pass through a drying process in an extremely short time is described above. So that it is evenly distributed in the combining layer,
It needs to be distributed, and it is required to gelatinize quickly in the drying process. Further, in recent years, waste paper is frequently collected and reused, and a paper strength improver is added in a large amount due to the decrease in strength of paper resulting from the shortening of pulp, and
Water-soluble starch or a starch solution pre-gelatinized is used during papermaking to improve the strength of the paper in the Z-axis direction.

Since the starch used in these is relatively inexpensive in price, it can be used sufficiently as a sizing agent even if the effect on the amount added is not particularly emphasized, and it has been widely used until now. However, when a large amount of starch is used, a large amount of water is used in the papermaking process for sheet-like products such as paperboard, so the starch used as a sizing agent in the drainage flows out without sufficient yield. However, particularly water-soluble starch, gelatinized starch solution, or modified starch having a large amount of water-soluble components may pollute the wastewater and increase the load of the wastewater treatment. Furthermore, depending on the modification method, eutrophication components such as phosphoric acid and urea flow out, and the wastewater pollutes rivers and lakes. In order to avoid such problems, it is possible to use cationized starch that is easy to retain in pulp and the like, but when the obtained sheet is used as a food container or food packaging material, it is originally cationized and not suitable for food. There is concern about the danger of a part of starch being dissolved in the contents. In addition, dicarboxylic acid ester starch has been proposed as a method for solving these problems (Japanese Patent Laid-Open No. Hei 5-
106192). The dicarboxylic acid ester starch certainly has a low gelatinization temperature, has a good yield between the layers, and improves the interlayer adhesive strength. However, since the permeability is poor, the effect of improving the strength of the paper in the Z-axis direction cannot be expected in recent years when the amount of recovered waste paper pulp used is large. Further, there is a drawback that the chemicals used in producing the dicarboxylic acid ester starch are generally expensive.

[0005]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors in consideration of these situations, the starch is subjected to a process for lowering the molecular weight thereof, and at the same time, an acetylation process and a dicarboxylic acid esterification process are used in combination. The inventors have found that the starch derivative thus obtained is suitable for achieving this purpose, and completed the present invention.

[0006] That is, the present invention is an adhesive for use between the layers of sheets such as paperboard that are laminated together at the time of papermaking, wherein the degree of total substitution is 0.005 to a starch having a low molecular weight.
1.0 acetylation and aliphatic, aromatic, alicyclic,
Alternatively, an interlayer of paperboard or the like characterized by comprising a starch derivative obtained by subjecting a dicarboxylic anhydride having 4 to 22 carbon atoms selected from the group consisting of a bicyclic aliphatic dicarboxylic acid anhydride to an esterification reaction. It is an adhesive.

The purpose of slightly lowering the molecular weight of starch is Z
This is because the permeability in the axial direction is improved and the strength is enhanced. In the case of a dicarboxylic acid ester starch having a low gelatinization temperature, when it is used between the layers of a sheet such as a paperboard that is made up at the time of papermaking, the gelatinization is sufficient with a small amount of heat in the drying process, but the molecular weight is not low. Almost no penetration of the paper in the Z-axis direction is observed. Not only that, but especially in the case of starch species having large starch molecules, the gelatinized starch does not spread over the entire pulp fibers, resulting in a state close to point adhesion, and as a result, the interlaminar adhesive strength itself may decrease. When this phenomenon is prevented and the penetration of the paper in the Z-axis direction is taken into consideration, a slight reduction in molecular weight is essential.

As a method for slightly reducing the molecular weight of starch, conventional methods such as oxidation with hypochlorite and persulfate, acid treatment with mineral acids such as hydrochloric acid and sulfuric acid, α-amylase, There is an enzyme treatment with β-amylase or the like, a roasting method of treating at high temperature, etc., but there is no particular limitation for achieving the object of the present invention, and one of either method,
Alternatively, two or more may be used in combination. Further, the present invention is characterized in that the water-soluble content at room temperature is 20% or less with respect to the original starch. Penetration becomes a little excessive if the water-soluble content is lower than 20%,
There is a possibility that the interlayer adhesion strength will be slightly reduced and that drainage will be adversely affected. In addition, when gelatinized and solubilized in water, the yield to pulp is slightly improved because it is not a low molecular weight starch,
Even in this case, most of the water is washed away in white water, and the load on the drainage is large.

The starch as a raw material is not particularly limited, and any of corn starch, glutinous corn starch, high amylose corn starch, potato starch, tapioca starch, wheat starch, rice starch, glutinous rice starch and the like can be used. It can be used and there is no particular limitation for achieving the object of the present invention, and one of them or a combination of two or more may be used.

The advantages of the combined use of acetylation and dicarboxylic acid esterification in the present invention are described below. That is,
Both reactions have the effect of lowering the gelatinization temperature, and dicarboxylic acid esterification is particularly effective, and has the following preferable properties as an interlayer adhesive. In other words, in the papermaking process, aluminum sulfate is usually added to improve drainage and promote the fixing of the additive chemicals, but positively charged aluminum ions are quickly adsorbed by the negatively charged pulp fibers. Dicarboxylic esterified starch having a carboxyl group that does not participate in the binding easily binds to the aluminum ions fixed to the pulp fiber in this way, and thus has a good affinity with the pulp fiber in the paper making process. It is considered that starch as these adhesives functions in a highly desirable state.
Also in the case of paper making process without adding aluminum sulfate,
At the present time when the use of waste paper pulp is increasing, calcium ions and the like from fillers and the like in waste paper are always present in the pulp, so it is considered that the same effect as in the case of the aluminum ion can be obtained.

On the other hand, there is a fatal drawback in industry that the reagent used for the esterification reaction is relatively expensive. On the other hand, since the reagent used for acetylation is cheaper than the dicarboxylic acid anhydride used for esterification, the combined use of two types of reactions does not impair the above-mentioned effects, and the added dicarboxylic acid anhydride Therefore, it is possible to exert an industrially advantageous value in that the amount of can be reduced. Further, an increase in the molecular weight of starch due to dicarboxylic acid esterification can be suppressed by substituting a part thereof with an acetyl group, and desired properties such as permeability can be secured.

In the acetylation, acetic anhydride, vinyl acetate, acetyl chloride and the like are usually used, and there is no particular limitation to achieve the object of the present invention. One of these methods, or Two or more may be used in combination. Acetylation and esterification are usually carried out at the same time, but it is also possible to carry out either one and then the other. The ratio of the degree of acetylation and the degree of esterification can be arbitrarily adjusted according to the purpose,

The dicarboxylic acid anhydride used for esterification in the present invention has 4 to 4 carbon atoms selected from the group consisting of aliphatic, aromatic, alicyclic or bicyclic aliphatic dicarboxylic acid anhydrides. An anhydride of 22 dicarboxylic acids is used. Examples of carboxylic acids of these acid anhydrides include maleic acid, phthalic acid, trimellitic acid, pyromellitic acid, endomethylenetetrahydrophthalic acid,
Chlorendic acid, methylendomethylenetetrahydrophthalic acid, tetrahydroxyphthalic acid, diphenic acid, citraconic acid, glutaconic acid, glutaric acid, succinic acid, hexaisobutenylsuccinic acid, nonylsuccinic acid, n-octylsuccinic acid, 2-ethyl 2 -Methylsuccinic acid, dimethylbenzylsuccinic acid, octenylsuccinic acid, hexenylsuccinic acid, decynylglutaric acid, dodecenylsuccinic acid, itaconic acid and the like can be mentioned, and succinic acids such as octenylsuccinic acid are particularly preferable. In terms of safety, when used as a food container or food packaging material, succinic acid esterified starch is recognized as a modified starch for food according to US FDA standards, and there is no problem. These dicarboxylic acids may be used as their respective acid anhydrides in the esterification reaction with starch. If the number of carbon atoms of the dicarboxylic acid is 3 or less, the gelatinization temperature will not decrease unless the degree of esterification is increased, and if the number of carbon atoms is 23 or more, the esterification will not be sufficiently performed and the esterification of the desired property will proceed. Since it is difficult to do so, the number of carbon atoms was set in the above range.

In the present invention, the total substitution degree of the acetyl group and the dicarboxylic acid ester is 0.005-1.
It is 0, preferably 0.01 to 0.1. The degree of substitution is 0.
If it is 005 or less, the low gelatinization temperature which is the object of the present invention cannot be obtained, and if it exceeds 1.0, a solubilized portion is produced during the reaction, which not only deteriorates the yield of the reaction but also gelatinizes it in the drying step for production. This may cause troubles, and the amount of starch discharged in the wastewater during papermaking increases, resulting in a result that is contrary to the object of the present invention.

In the present invention, acetylation with a total degree of substitution of 0.005 to 1.0, and aliphatic, aromatic, alicyclic, or bicyclic aliphatic dicarboxylic acid anhydride are added to the starch having a low molecular weight. 4 to 2 carbon atoms selected from the group consisting of
The starch derivative obtained by subjecting the dicarboxylic acid anhydride of 2 to the esterification reaction is generally used in the same manner as the adhesive used in this type of field. That is, for example, it can be used by a method of suspending starch in water to form a slurry, spray-coating with a spray nozzle or the like, and then heating in a drying step. The heating in the drying step can be performed under the heating conditions conventionally used for papermaking, and good gelatinization and adhesive strength, and improvement of the strength of the paper in the Z-axis direction can be achieved.

[0016]

EXAMPLES The present invention will be described below with reference to examples, but the gist of the present invention is not limited thereto.
In the following examples, parts indicate parts by weight.

I. Preparation of Test Starch Example 1 Corn starch 100 parts Water 280 parts 36% HCl 1.1 parts The above is charged in a reaction vessel and subjected to acid treatment at 30 ° C. for 2 hours with stirring, and then succinic anhydride 3 parts vinyl acetate 1 (3 parts) and the pH is maintained at 9.0 with 10% NaOH and reacted for 1 hour. After adjusting the pH to neutral, filtration and washing with water are repeated 3 times, and the water content is adjusted to around 10% with a hot air dryer,
Acetyl succinic acid ester corn starch having a total degree of substitution of 0.05 and a gelatinization starting temperature of 47 ° C. was obtained.

Example 2 Water 180 parts Tapioca starch 100 parts Sodium hypochlorite with an effective chlorine concentration of 5% 4.5 parts The above is charged in a reaction vessel and the pH is maintained at 6.0 with 3% NaOH while stirring, and 1 React on time. After that, 2.0 parts of vinyl acetate and 2.0 parts of succinic anhydride were added, and the pH was maintained at 9.0 with 3% NaOH.
React on time. After adjusting the pH to neutral, filtration and washing with water are repeated 3 times to adjust the water content to about 10% with a hot air dryer to obtain acetylsuccinic acid tapioca starch with a total degree of substitution of 0.06 and a gelatinization starting temperature of 43 ° C. Obtained.

Example 3 Potato starch 100 parts Water 180 parts Clistase PA ^* 0.05 parts ( ^* Amylase: Daiwa Kasei Co., Ltd.) The above was charged into a reaction vessel and the pH was adjusted to 6.0 with 3% NaOH while stirring. Combine and treat at a temperature of 50 ° C. for 2 hours. Then, cool to room temperature, inactivate the enzyme with a small amount of sodium hypochlorite, add 1.00 parts of succinic anhydride, 4.00 parts of vinyl acetate, and keep the pH at 9.0 with 3% NaOH. 1
React on time. After adjusting the pH to neutral, filtration and washing with water are repeated 3 times to adjust the water content to about 10% with a hot air drier, and acetylsuccinate potato starch with a total degree of substitution of 0.08 and a gelatinization starting temperature of 40 ° C. is added. Obtained.

Example 4 Sticky corn starch 100 parts Water 180 parts Sodium hypochlorite with an effective chlorine concentration of 5% 6.0 parts The above was charged in a reaction vessel and the pH was maintained at 6.0 with 3% NaOH while stirring. React for 1 hour. Thereafter, 2.0 parts of acetic anhydride and 2.0 parts of maleic anhydride are added, and the mixture is further reacted with 3% NaOH at pH 9.0 for 1 hour. After adjusting the pH to neutral, filter and wash with water 3
Repeatedly adjust the water content to around 10% with a hot air dryer,
Acetyl succinic acid ester glutinous corn starch having a total degree of substitution of 0.06 and a gelatinization starting temperature of 48 ° C. was obtained.

Comparative Example 1 Corn starch 100 parts Urea 4 parts Phosphoric acid 3 parts Sodium pyrophosphate decahydrate 5 parts After thoroughly stirring and kneading the above, once with a hot air drier 65 ° C.
After preliminarily drying while maintaining the temperature below, it was treated in a vacuum heating oven at 120 ° C. for 2 hours. Urea phosphate ester corn starch containing a water-soluble content of 24% was obtained.

COMPARATIVE EXAMPLE 2 Wheat starch 100 parts Succinic anhydride 6 parts Water 200 parts The above was charged in a reaction vessel and stirred for 3 hours while keeping the pH at 9.0 with 3% NaOH. After the reaction, the pH was adjusted to 6. The water content was adjusted to 0, and the filtration and washing were repeated 3 times to adjust the water content to about 10% with a hot air dryer to obtain an esterification degree of 0.0.
7. Succinate wheat starch having a gelatinization starting temperature of 42 ° C. was obtained.

Comparative Example 3 Potato Starch 100 parts Vinyl Acetate 2.5 parts Water 200 parts The above was charged in a reaction vessel and stirred with 10% Na ₂ C.
Keeping the pH at 9.0 with an O ₃ aqueous solution, reacting for 1 hour, after the reaction, adjusting the pH to 6.0, repeating filtration and washing with water 3 times to adjust the water content to about 10% with a hot air dryer, An acetylated potato starch having a degree of acetylation of 0.03 and a gelatinization starting temperature of 46 ° C. was obtained.

II. Physical Properties and Performance of Test Starch Test Method 1 T-Peeling Test. Sample: 2-layer paper with the following structure 1st layer LBKP / NBKP / cardboard waste paper = 2/5 /
3 Freeness 400mlc.sf 2nd layer NBKP alone Freeness 400mlc.sf
sf Both the above two layers have a basis weight of 100 g / m ² . Spraying of starch slurry: After hand-making the first layer with a sheet machine, 1.0 g / m ^{2 of} the starch slurry is sprayed, the second layer is superposed, and dried by a rotary dryer at 60 ° C. for 60 seconds.

Test method 2 IGT printing suitability test. Sample: 2 layers of paper with the following constitution: 1 and 2 layers NBKP freeness 400 mlc.sf basis weight 40 g / m ² . Spraying starch slurry: After hand-making the first layer with a sheet machine, 1.0 g / m ^{2 of} the starch slurry is sprayed, the second layer is overlaid, and dried at 75 ° C. for 60 seconds with a rotary dryer. IGT conditions: ink used: TV25, amount of applied ink: × 2, spring A used

Test Method 3 Water-Soluble Component. Operation: 50 g of 2% sample starch (anhydrous equivalent) slurry
After stirring for 2 hours in a beaker, it was filtered with a commercially available No. 5 filter paper or a membrane filter and dried. It is calculated from the starch weight difference before and after the treatment.

Test Method 4 Permeability Test. Sample: Commercial No. 2 filter paper. Operation: Two pieces of filter paper in a wet state after being soaked in water are overlapped, 50 μl of a sample starch slurry having a concentration of 10% is appropriately put on it, sandwiched between aluminum foils, and pressed with a hot press at 80 ° C. for 60 seconds. : Evaluation: The iodine solution was sprayed onto the second lower filter paper to color the permeated starch, and the colored area was evaluated on a 5-point scale.

Test Method 5 Starch Yield. Paper material: NBKP, freeness 400 mlc.sf, sulfuric acid band 0.5% added, pH 6.3. Papermaking method: Pour the agitated paper material into a filter having a 100 mesh wire and let it stand for 2 minutes, then add 1% of starch slurry to pulp, squeeze water under reduced pressure, and make paper. ． Quantification of starch: The sheet obtained above was cut into pieces, and the starch in the paper layer was subjected to enzymatic decomposition treatment and then quantified by the phenol-sulfuric acid method.
Calculate by comparing with the added amount.

[0029]

[Table 1] Note: Comparative examples use unprocessed corn starch, unprocessed potato starch, and unprocessed tapioca starch.

Table 1 shows a list of the test results. From the results in this table, it is clear that the modified starch of the present invention shows the peel strength indicating the interlayer adhesion strength of paper, the IGT printability test result which is an index of the paper strength in the Z-axis direction, the permeability in the Z-axis direction, It can be seen that not only is the starch yield superior to various raw starches in all respects, but it is also superior in all performances to the starch obtained by other chemical modification methods. The water-soluble component also had a high starch yield due to the synergistic effect of being 20% or less in comparison with Comparative Example 1 and the fixability to the pulp due to the dicarboxylic acid ester, and the molecular weight was slightly reduced. The effect is permeability, and the result of the IGT printability test is good.

[0031]

As described above, when the mild low-molecular-weight acetyl dicarboxylic acid ester starch of the present invention is used as an interlayer adhesive during sheet making of paperboard or the like, starch is efficiently bound to the pulp slurry which is a raw material for papermaking. There is almost no flow out of the system to the outside of the system, and during drying, the sizing agent permeates between the paper layers to improve not only the peel strength but also the strength of the paperboard in the Z-axis direction. Therefore, it is possible to reduce the amount of starch added, and in some cases, it becomes unnecessary to use other sizing agents, synthetic sizing agents, etc. to enhance the paper strength, and it is possible to expect a remarkable improvement in economic effect, Since the loss of starch to the system is suppressed, the load of organic matter in the wastewater is reduced, and compared to other chemical treatment methods, the lost components do not contain nutrient components, which is extremely favorable for environmental conservation. Has a number of advantages, including high safety and the fact that no special organic chemicals are used.

Claims (3)

[Claims] 1. An adhesive for use between layers of sheets such as paperboard to be made at the time of papermaking, which is a starch having a low molecular weight and acetylation with a total substitution degree of 0.005 to 1.0. And starch obtained by subjecting a dicarboxylic acid anhydride having 4 to 22 carbon atoms selected from the group consisting of aliphatic, aromatic, alicyclic, or bicyclic aliphatic dicarboxylic acid anhydrides to an esterification reaction An interlayer adhesive such as paperboard characterized by comprising a derivative. 2. A starch having a low molecular weight so that the water-soluble content at room temperature is 20% or less, a total degree of substitution of 0.
005-1.0 acetylation and aliphatic, aromatic,
A starch derivative obtained by subjecting a dicarboxylic acid anhydride having 4 to 22 carbon atoms selected from the group consisting of alicyclic or bicyclic aliphatic dicarboxylic acid anhydrides to an esterification reaction. The adhesive according to claim 1. 3. The adhesive according to claim 1, wherein the dicarboxylic acid anhydride used in the esterification reaction is succinic anhydride.