TECHNICAL FIELD

The present invention relates to a dry strength chemical developed for increasing paper strength and the production method thereof.

PRIOR ART

Starch is the dry strength chemical which is mostly used in paper industry. Since there is no product in the market which is alternative for starch or since there is no commercially successful product, a new study is needed in this field. Since starch is in powder form, it cannot be directly used. Starch shall be cooked at high temperature. Moreover, if starch is not cooked well, its performance is not sufficient and therefore, the need for starch usage increases. As the starch usage amount increases, operational costs increase. Moreover, cooked starch shall be immediately used. The product may deteriorate when it is not used immediately and this leads to an additional cost for the plant. Besides, starch can have a specific charge thereon. The reason of limited amount of this charge amount is that starch has a complex structure.

Since the shelf life of starch solution is short and since starch cannot be used without cooking and since the charge density on starch is delimited, it is considered that synthesizing a product, of which the shelf life is long and which can be provided in liquid form and where the charge density thereon can be adjusted as desired, will bring a solution to the sector.

As a result, because of all of the abovementioned problems, an improvement is required in the related technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a dry strength chemical for increasing paper strength and the production method thereof, for eliminating the above mentioned disadvantages and for bringing new advantages to the related technical field. An object of the present invention is to provide a production method developed for obtaining a dry strength chemical with different viscosity values.

Another object of the present invention is to provide a dry strength chemical of which the shelf life is increased.

In order to realize all of the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a dry strength chemical production method developed for increasing paper strength. Accordingly, said invention is characterized by comprising primarily the following steps for obtaining reaction final product with the desired viscosity;

i) Modifying starch with at least one type of organic and/or inorganic acid and realizing the hydrolysis thereof

ii) Adding at least one vinyl monomer and at least one cationic monomer to the hydrolysis solution in step (i)

iii) Adding at least one polymerizing agent, at least one biocide and at least one type of base, which adjusts the PH value of the reaction solution to the predetermined level, into the solution obtained after step (ii).

In a preferred embodiment of the present invention, the starch used in step (i) is natural starch which is at least one of or mixture of corn starch, wheat starch, potato starch, rice starch, tapioca starch.

In a preferred embodiment of the present invention, organic or inorganic acid used in step (i) is at least one of or mixtures of hydrochloric acid, sulfuric acid, methane-sulfonic acid, nitric acid, formic acid, phosphoric acid and acetic acid.

In a preferred embodiment of the present invention, step (i) comprises the sub-steps of:

x) Dispersing starch in deionized water in a reactor with stirring property

y) Adding at least one type of organic and/or inorganic acid into the reaction solution after step (x) and reducing starch to predetermined molecular weight.

In a preferred embodiment of the present invention, in step (x), the amount of starch in the aqueous reaction solution is between 12-25% by weight. In a preferred embodiment of the present invention, in step (y), the amount of acid used in step (y) in the solution formed by starch and deionized water is between 0.07 and 0.1% by weight.

In a preferred embodiment of the present invention, in step (i), the temperature of the reaction solution is 72°C at most.

In a preferred embodiment of the present invention, the vinyl monomer in step (ii) comprises at least one of or mixtures of acryl-amide, meth-acryl-amide, ethyl-acryl-amide, croton-amide, N-methyl acryl-amide, N-butyl acryl-amide or N-ethyl meth-acryl-amide vinyl monomers.

In a preferred embodiment of the present invention, the cationic monomer in step (ii) is at least one of or mixtures of 2-vinyl-pyridine, 2-vinyl-N-methyl-pyridinium chloride, (p-vinyl- phenyl)trimethyl ammonium chloride, diallyl-dimethyl-ammonium chloride, 2-(dimethyl- amino)ethyl acrylate, trimethyl p-vinyl-benzyl)ammonium chloride, p-dimethyl-amino-ethyl- styrene, dimethyl-amino-propyl acryl-amide, 2-methyl-acroyloxy-ethyl-trimethyl ammonium methyl-sulfate or 3-acryl-amido-3-methyl-butyl trimethyl ammonium chloride.

In a preferred embodiment of the present invention, the amount of cationic monomer used in step (ii) is between 5% and 30% of the total reaction solution by weight.

In a preferred embodiment of the present invention, in step (iii), as the polymerization starter, at least one of or mixtures of peroxide derivatives, azo components, potassium per-sulfate and ammonium per-sulfate are used.

In a preferred embodiment of the present invention, as the base in step (iii), at least one of or mixtures of alkali metal hydroxides, carbonates, bicarbonates, earth alkaline metal hydroxides, tri-alkyl-amines, tetra-acryl-ammonium hydroxides, ammonia, organic amines, alkali metal sulfides, earth alkaline sulfides, alkali metal alkoxides, earth alkaline alkoxides and alkali metal phosphates are used.

In a preferred embodiment of the present invention, in step (iii), sodium hydroxide is used as base.

In a preferred embodiment of the present invention, the following steps are provided respectively:

a) Dispersing natural starch in deionized water in a stirrer reactor b) Adding aqueous acryl-amide solution, comprising acryl-amide, and diallyl- dimethyl-ammonium chloride to the reaction solution

c) Heating the reactor solution to the temperature between 85°C and 100°C in the reactor and stirring at this temperature between 1 -4 hours

d) Keeping the reaction solution temperature between 65°C and 100°C

e) Adding potassium per-sulfate aqueous solution to the reaction solution

f) Adding aqueous acryl-amide solution comprising acryl-amide between 10-60% by weight and stirring the reaction solution at 75°C-80°C between 45 minutes-90 minutes

g) Adding polymerization starter aqueous solution to the reaction solution and mixing thereof

h) Adding alkali metal hydroxide into the reaction solution.

In a preferred embodiment of the present invention, between steps (g) and (h), predetermined amount of deionized water is added to the reaction solution.

In a preferred embodiment of the present invention, in step (b), the acryl-amide aqueous solution, added to the reaction solution, is between 10%-60% of the prepared total aqueous acryl-amide solution by weight.

In a preferred embodiment of the present invention, in step (f), the acryl-amide aqueous solution, added to the reaction solution, is between 70%-80% of the prepared total aqueous acryl-amide solution by weight.

In order to realize all of the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a dry strength chemical which is obtained by means of the method given in any of the preceding claims. Accordingly, at least one natural starch; at least one vinyl monomer; at least one cationic monomer; at least one organic or inorganic acid which reduces natural starch to the desired dimension; at least one base for regulating the pH value of the dry strength chemical; at least one polymerization agent; at least one biocide are provided.

In a preferred embodiment of the present invention, said organic or inorganic acid is at least one of or mixtures of hydrochloric acid, sulfuric acid, methane-sulfonic acid, nitric acid, formic acid, phosphoric acid and acetic acid. In a preferred embodiment of the present invention, said organic or inorganic acid is sulfuric acid.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is the chemical structure of cationic starch modified polymers.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, the subject matter dry strength chemical and the production method thereof are explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

Surprisingly, it is observed that the strength of paper increases by means of obtaining cationic starch modified polymers, comprising vinyl components and various monomers, by using the subject matter method.

The subject matter method essentially comprises 3 steps as given below respectively.

a) Hydrolyzing of starch

b) Preparing monomers and adding monomers to the reactor

c) Adding chemicals

Hydrolyzing of Starch

In the subject matter method, as the starch, natural starch is used which is selected from corn starch, wheat starch, potato starch, rice starch and tapioca starch. The used starches can be mixed with the predetermined proportions or can be used as a single type. In the preferred application of the invention, corn starch is used as starch.

The medium where cationic starch modified polymer solution is prepared will be hereafter called reaction solution in the specification. During the process, the addition and ingredient of the additives in the reaction solution change and they increase in volume and in weight. The solution obtained by completing the whole process is the reaction final solution.

Before starting polymerization in the reaction solution, the hydrolysis of the starch is realized. For hydrolysis, first of all, starch is dispersed in deionized water. Thus, reaction solution is obtained. The amount of starch used in the aqueous reaction solution is between 12% and 25% by weight. In the preferred application, the amount of starch in the aqueous reaction solution is between 15-20% by weight.

For the hydrolysis, deionized water is taken into a stirrer reactor and starch is added into the water mixed in the reactor. Afterwards, a suitable organic or inorganic acid is added to the reaction solution in order to bring the starch into predetermined dimensions. At least one of or mixtures of hydrochloric acid (HCI), sulfuric acid (H2SO4), methane-sulfonic acid (CH3SO3H), nitric acid (HNO3), formic acid (HCO2H), phosphoric acid (H3PO4) and acetic acid (C2H4O2) may be used as organic or inorganic acid. Preferably sulfuric acid (H2SO4) is added. The amount of sulfuric acid used is an important criterion in the subject matter method. The amount of used sulfuric acid in the reaction solution formed by starch + deionized water is between 0.07% and 0.1% by weight. In the preferred application, the amount of used sulfuric acid in the reaction solution formed by starch + deionized water is between 0.08% and 0.09%. The purity of the used sulfuric acid is 98%.

Heat is applied to the reaction solution during dispersing of starch in the sulfuric acid and in deionized water. The temperature of reaction solution is 70±2°C. It is preferred that the temperature does not exceed 72°C. Above this temperature value, the viscosity of the reaction solution increases. Since the viscosity increases, the proportion of chemicals to be added to the reaction solution changes. The stirring process changes between 45 minutes and 90 minutes. In the preferred application, the stirring process is 60 minutes.

According to the desired viscosity value in the reaction final solution, the range of molecular weight where starch is in situ and hydrolytically fragmented and reduced can be changed. The other parameters which affect the viscosity of the reaction final solution are the applied temperature, the liquid amount and the stirring duration. By means of changing the temperature applied during the process, stirring duration and the amount of acid used, reaction final solution can be produced with separate viscosity for each different requirement.

Preparing monomers and adding monomers to the reactor

At least one of or mixture of acryl-amide, meth-acryl-amide, ethyl-acryl-amide, croton-amide, N-methyl acryl-amide, N-butyl acryl-amide or N-ethyl meth-acryl-amide vinyl monomers are added to deionized water heated to the range of 30°C and 60°C in a separate stirrer and they are stirred. In case of application of a temperature which is above this temperature, acryl amide may become polymerized. After stirring of the acryl-amide solution is completed, at least one cationic monomer together with the acryl-amide solution is added onto the reaction solution comprising starch hydrolyzed in the reactor. The amount of acryl-amide solution added onto the reaction solution is between 20% and 30% of the total prepared acryl-amide solution by weight. In the preferred application, the amount of acryl-amide solution added onto the reaction solution is between 23% and 27% of the prepared total acryl-amide solution by weight. The used cationic monomer amount is between 5% and 30% of the reaction solution comprising hydrolyzed starch. In the preferred application, the amount of used cationic monomer is between 9% and 25% of the reaction solution comprising hydrolyzed starch.

As the cationic monomer, at least one of or mixture of 2-vinyl-pyridine, 2-vinyl-N-methyl- pyridinium chloride, (p-vinyl-phenyl)trimethyl ammonium chloride, diallyl-dimethyl-ammonium chloride, 2-(dimethyl-amino)ethyl acrylate, trimethyl p-vinyl-benzyl)ammonium chloride, p- dimethyl-amino-ethyl-styrene, dimethyl-amino-propyl acryl-amide, 2-methyl-acroyl-oxyethyl- trimethyl ammonium methyl-sulfate, or 3-acrylamido-3-methylbutyl trimethyl ammonium chloride may be used. In a preferred application of the present invention, diallyl-dimethyl- ammonium chloride (hereafter it will be called DADMAC in the specification) is used.

The reaction solution is heated to temperature range between 85°C and 100°C in the reactor for cooking the starch and the reaction solution is stirred for 1 -4 hours in this temperature. Preferably, the reaction solution is heated to the temperature range of 90°C and 95°C in the reactor after the addition of monomers. It is important that the temperature does not exceed 97°C. At temperatures lower than 85°C, it becomes difficult to cook, fragment and downsize starch to the desired molecule dimension. After the stirring process, the reactor is kept within temperatures between 65°C and 100°C.

Adding chemicals

Deionized water is heated to the temperature range of 40°C and 60°C in a separate stirrer and polymerizing agent is added therein. At least one of or mixtures of various peroxides, azo components, potassium per-sulfate and ammonium per-sulfate may be used as the polymerizing agent. In the preferred application, potassium per-sulfate is used.

The amount of potassium per-sulfate in deionized water is between 7% and 10%. In the preferred application, this value is between 8% and 9%. 95-97% of the prepared potassium per-sulfate solution is added to the reaction solution. After the addition of potassium per sulfate, the temperature of the reaction solution shall be between 75°C and 80°C. In case the temperature exceeds 80°C, the reactor shall be cooled. By means of potassium per-sulfate solution addition, reaction is continued for 1 hour between 75°C and 80°C. The amount of potassium per-sulfate within the reaction solution is between 0.60% and 0.80%.

After addition of potassium per-sulfate, the remaining part of the acryl-amide solution is fed to the reaction solution for 1 hour at predetermined proportions. After addition of acryl-amide, the remaining 3-5% of the potassium per-sulfate solution is added to the reaction solution and the reaction is continued by stirring for 1 hour more between 75°C and 80°C. After this process is completed, deionized water may be added to the reaction solution between 75°C and 80°C optionally according to the desired final product viscosity.

In the continuing process, the reaction solution is left for cooling in medium temperature until it reaches between 35°C and 40°C. After the cooling process, base is added to the reaction solution where the amount of added base is equal to 0.20%-0.25% of the total weight of the reaction solution. As the base, at least one of or mixtures of alkali metal hydroxides, carbonates, bicarbonates, earth alkaline metal hydroxides, tri-alkyl-amines, tetra-acryl- ammonium hydroxides, ammonia, organic amines, alkali metal sulfides, earth alkaline sulfides, alkali metal alkoxides, earth alkaline alkoxides and alkali metal phosphates like sodium phosphate and potassium phosphate can be used. Preferably, as the base, alkali metal hydroxides like lithium hydroxide, sodium hydroxide and potassium hydroxide are used or alkali metal carbonates like sodium carbonate and potassium carbonate are used. More preferably, sodium hydroxide (NaOH) is used as base.

10% NaOH solution is added to the reaction solution and afterwards, biocide is added at an amount of 0.20%-0.25% of the total weight obtained. After addition of biocide, the reaction solution is stirred for 30-45 minutes more and the reaction is completed. The viscosity of the reaction final solution, which is the final product, is between 100cp and 50000cp at 22°C. In the preferred application, the viscosity of the reaction final solution is between 500cp and 10OOOcp at 22°C. More preferably, the viscosity of reaction final solution is between 1000 cp and 5000 cp at 22°C.

The probable chemical structure of the reaction final solution is given in Figure 1. It enters into electrostatic interaction with anionic cellulose by means of the cationic charges carried thereon. It forms hydrogen bond with cellulose by means of the -OH groups carried thereon. Since its molecular weight is great, its adhesion to cellulose is strong.

The exemplary studies obtained by means of the above mentioned method are described below. 1

500 kg corn starch is dispersed in 2400 kg deionized water inside a stirrer reactor. 98% sulfuric acid between 2.5 kg - 2.55 kg is added into this reaction solution which has been obtained and stirred at 60±2°C for 1 hour.

350±10 kg of the 50% acryl-amide aqueous solution prepared in a separate stirrer and 360 kg DADMAC have been added to the reaction solution. The obtained reaction solution is heated to 92°C-95°C and it is stirred for 1.5 hours at this temperature. After completion of the stirring process, the reactor is cooled down to 75°C. 580 kg of the solution, prepared by adding 50 kg potassium per-sulfate in 550 kg deionized water at 45°C in a separate stirrer, is added into the reaction solution. Afterwards, by means of a specific flow rate, 1 100 kg acryl amide aqueous solution is fed to the reactor for 1 hour. During this duration, it shall be taken care that the temperature of the reaction solution inside the reactor shall not exceed 80°C. As the 1 hour feeding is completed, 1400 kg deionized water is added to the reaction solution. The reaction solution is left for cooling, and as the temperature reaches 35°C, 15 kg 10% NaOH solution is added therein. Thus, the pH value of the mixture is adjusted to be 3. Finally, 8 kg KATHON 886 WT is added as biocide and it is stirred for 30-45 minutes more and the reaction final solution is obtained.

Example 2

95 kg corn starch is dispersed in 470 kg deionized water inside a stirrer reactor. 98% sulfuric acid between 0.30 kg - 0.35 kg is added into this reaction solution which has been obtained and stirred at 60±2°C for 1 hour.

60 kg of the 50% acryl-amide aqueous solution prepared in a separate stirrer and 79 kg DADMAC have been added to the reaction solution. The obtained reaction solution is heated to 78°C-80°C and it is stirred for 1 hour at this temperature. After completion of the stirring process, the reactor is cooled down to 75°C. 80 kg of the solution, prepared by adding 9.7 kg potassium per-sulfate in 75 kg deionized water heated to 55°C in a separate stirrer, is added into the reaction solution. Afterwards, by means of a specific flow rate, 222 kg 50% acryl amide aqueous solution is fed to the reactor for 1 hour. Feeding is realized preferably at the speed of 3.7 kg/minute. During this duration, it shall be taken care that the temperature of the reaction solution inside the reactor shall not exceed 80°C. After the 1 hour feeding is completed, the reaction is continued for 2 hours between 78°C-80°C. Afterwards, the remaining 4.7 kg potassium per-sulfate solution is added to the reaction solution and stirring process is applied for 1 hour more between 78°C-80°C and the reaction solution is left for cooling, and as the temperature reaches 40°C, 5 kg 10% NaOH solution is added therein for reducing pH value of the reaction solution. Thus, the pH value of the mixture is adjusted to be 3. The reaction solution is cooled to 25°C-35°C, and finally 0.5 kg KATHON 886 WT is added as biocide and it is stirred for 30-45 minutes more and the reaction final solution is obtained.

Example 3

85 kg corn starch is dispersed in 470 kg deionized water inside a stirrer reactor. 98% sulfuric acid between 0.12 kg - 0.17 kg is added into this reaction solution which has been obtained and stirred at 60±2°C for 1 hour.

60 kg of the 50% acryl-amide aqueous solution prepared in a separate stirrer and 60 kg DADMAC have been added to the reaction solution. The obtained reaction solution is heated to 78°C-80°C and it is stirred for 1 hour at this temperature. After completion of the stirring process, the reactor is cooled down to 75°C. 80 kg of the solution, prepared by adding 9.7 kg potassium per-sulfate in 75 kg deionized water heated to 55°C in a separate stirrer, is added into the reaction solution. Afterwards, by means of a specific flow rate, 222 kg 50% acryl amide aqueous solution is fed to the reactor for 1 hour. Feeding is realized preferably at the speed of 3.7 kg/minute. During this duration, it shall be taken care that the temperature of the reaction solution inside the reactor shall not exceed 80°C. After the 1 hour feeding is completed, the reaction is continued for 2 hours between 78°C-80°C. Afterwards, the remaining 4.7 kg potassium per-sulfate solution is added to the reaction solution and stirring process is applied for 1 hour more between 78°C-80°C and the reaction solution is left for cooling, and as the temperature reaches 40°C, 5 kg 10% NaOH solution is added therein for reducing pH value of the reaction solution. Thus, the pH value of the mixture is adjusted to be 3. The reaction solution is cooled to 25°C-30°C, and finally 0.5 kg KATHON 886 WT is added as biocide and it is stirred for 30-45 minutes more and the reaction final solution is obtained.

Example 4

65 kg corn starch is dispersed in 550 kg deionized water inside a stirrer reactor. 98% sulfuric acid between 0.12 kg - 0.17 kg is added into this reaction solution which has been obtained and stirred at 60±2°C for 1 hour.

60 kg of the 50% acryl-amide aqueous solution prepared in a separate stirrer and 60 kg DADMAC have been added to the reaction solution. The obtained reaction solution is heated to 78°C-80°C and it is stirred for 1 hour at this temperature. After completion of the stirring process, the reactor is cooled down to 75°C. 60 kg of the solution, prepared by adding 2 kg potassium per-sulfate in 75 kg deionized water heated to 55°C in a separate stirrer, is added into the reaction solution. Afterwards, by means of a specific flow rate, 222 kg 50% acryl amide aqueous solution is fed to the reactor for 1 hour. Feeding is realized preferably at the speed of 3.7 kg/minute. During this duration, it shall be taken care that the temperature of the reaction solution inside the reactor shall not exceed 80°C. After the 1 hour feeding is completed, the reaction is continued for 2 hours between 78°C-80°C. Afterwards, the remaining 4.7 kg potassium per-sulfate solution is added to the reaction solution and stirring process is applied for 1 hour more between 78°C-80°C and the reaction solution is left for cooling, and as the temperature reaches 40°C, 5 kg 10% NaOH solution is added therein for reducing pH value of the reaction solution. Thus, the pH value of the mixture is adjusted to be 3. The reaction solution is cooled to 25°C-30°C, and finally 0.5 kg KATHON 886 WT is added as biocide and it is stirred for 30-45 minutes more and the reaction final solution is obtained.

Example 5

65 kg corn starch is dispersed in 550 kg deionized water inside a stirrer reactor. 98% sulfuric acid between 0.12 kg - 0.17 kg is added into this reaction solution which has been obtained and stirred at 60±2°C for 1 hour.

120 kg of the 10-60% acryl-amide aqueous solution prepared in a separate stirrer and 60 kg DADMAC have been added to the reaction solution. The obtained reaction solution is heated to 78°C-80°C and it is stirred for 1 hour at this temperature. After completion of the stirring process, the reactor is cooled down to 75°C. 60 kg of the solution, prepared by adding 2 kg potassium per-sulfate in 75 kg deionized water heated to 55°C in a separate stirrer, is added into the reaction solution. Afterwards, by means of a specific flow rate, 201 kg 50% acryl amide aqueous solution is fed to the reactor for 1 hour. Feeding is realized preferably at the speed of 3.7 kg/minute. During this duration, it shall be taken care that the temperature of the reaction solution inside the reactor shall not exceed 80°C. After 1 hour feeding is completed, the reaction is continued for 2 hours between 78°C-80°C. Afterwards, the remaining 4.7 kg potassium per-sulfate solution is added to the reaction solution and stirring process is applied for 1 hour more between 78°C-80°C and the reaction solution is left for cooling, and as the temperature reaches 40°C, 5 kg 10% NaOH solution is added therein for reducing pH value of the reaction solution. Thus, the pH value of the mixture is adjusted to be 3. The reaction solution is cooled to 25°C-30°C, and finally 0.5 kg KATHON 886 WT is added as biocide and it is stirred for 30-45 minutes more and the reaction final solution is obtained. Thanks to the production of cationic starch modified polymer by means of the abovementioned method, costs are reduced by using any cheaper natural starch instead of fragmented ready-made starch which can be obtained commercially and the molecular weight of starch can be adjusted during the process. Moreover, said method provides advantages in controlling the characteristics of the final product, in other words, the characteristics of the reaction final solution.

In the abovementioned method, by means of the proportions of the chemicals used, the fluidity of the final product and thus, the performance parameters can be controlled. Thanks to this, a customized product can be obtained instead of a standard product.

The active substance percent in the cationic starch modified polymer solution, in other words, in the reaction final solution is between 5% and 40%. Preferably, the active substance percent in the cationic starch modified polymer solution is between 10% and 30%. More preferably, the active substance percent in the cationic starch modified polymer solution is between 20% and 30%.

The protection scope of the present invention is set forth in the annexed claims and cannot be restricted to the illustrative disclosures given above, under the detailed description. It is because a person skilled in the relevant art can obviously produce similar embodiments under the light of the foregoing disclosures, without departing from the main principles of the present invention.