KR102453138B1 - Method for producing polycarboxylates using lignin, polycarboxylate prepared thereby and concrete admixture containing the prepared polycarboxylate - Google Patents

Abstract

The present invention provides a method for preparing polycarboxylate using lignin, comprising the steps of: preparing lignin; and reacting the lignin with hydrogen peroxide and acetic acid to produce a reactant including polycarboxylate.

Description

Method for producing polycarboxylate using lignin, and concrete admixture comprising polycarboxylate and polycarboxylate prepared thereby

The present invention relates to a method for producing a polycarboxylate using lignin, and to a polycarboxylate prepared thereby and a concrete admixture comprising the prepared polycarboxylate.

In the pulping process, wood chips are pulped to produce pulp, and in this process, black liquor is generated as a by-product.

In general, black liquor is processed by burning in a boiler after concentration for recovery of drugs (NaOH and Na ₂ S). Thermal energy generated through boiler combustion is used to produce high-temperature and high-pressure steam, but considering that a large amount of energy is consumed for the concentration of black liquor, the energy conversion efficiency is not good.

Black liquor contains various substances such as lignin and hemicellulose, and among them, lignin is attracting attention as a raw material for new chemical materials. Therefore, if a high-value-added material can be manufactured using lignin, it is expected that the economic feasibility of the black liquor treatment will be significantly improved.

Registered Patent Publication No. 10-1153283

It is an object of the present invention to provide a method for preparing polycarboxylate of high added value from lignin.

Another object of the present invention is to provide a new concrete admixture capable of improving cement fluidity compared to conventional concrete admixtures using the prepared polycarboxylate.

On the other hand, other objects not specified in the present invention will be further considered within the range that can be easily inferred from the following detailed description and effects thereof.

In order to achieve the above object, the present invention proposes a method for preparing polycarboxylate from lignin. The method for preparing polycarboxylate using lignin according to an embodiment of the present invention is a method for preparing polycarboxylate using lignin. After performing the step of generating the reactant comprising the step of generating a reactant containing characterized in that

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In an example, the separating step may be characterized in that the polycarboxylate of the receiving portion and the polycarboxylate of the insoluble portion are separated from each other by centrifugation.

In an example, the method may further comprise a step of dialysis of the separated polycarboxylate in the receiving part to remove a low molecular weight reaction product.

In one example, the generating of the reactant may be characterized in that the reaction is performed at a temperature of 30 °C to 70 °C for 40 minutes to 80 minutes.

In one example, the ratio of lignin, hydrogen peroxide, and acetic acid in the step of generating the reactant may be 1 g: 5 to 7 ml: 1.25 to 1.75 ml.

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The polycarboxylate of another example of the present invention is a polycarboxylate prepared using lignin and dissolved in water, and has a charge density of -1.9 meq/g or less.

Another example of the concrete admixture of the present invention includes polycarboxylate prepared by using lignin and dissolved in water.

In another example, the charge density of the polycarboxylate dissolved in water may be characterized in that -1.9 meq/g or less.

In another example, the dough diameter of the result of the mortar table test performed by mixing 600 g of cement, 159.7 g of water, and 0.3 g of the concrete admixture may be characterized in that it is 200 mm or more.

The method for producing polycarboxylate according to an embodiment of the present invention has an advantage in that it can produce high value-added polycarboxylate from lignin that has been treated and treated as a conventional waste.

In particular, the polycarboxylate prepared by the method for producing a polycarboxylate according to an embodiment of the present invention has a charge density of -1.9 meq/g or less, and when this polycarboxylate is used as a concrete admixture, mortar compared to the prior art It has the advantage of significantly improving the liquidity of

On the other hand, even if it is an effect not explicitly mentioned herein, it is added that the effects described in the following specification expected by the technical features of the present invention and their potential effects are treated as described in the specification of the present invention.

1 is a schematic flowchart of a method for producing polycarboxylate according to an embodiment of the present invention.
2 is a graph measuring the content of hydroxyl groups of each type of polycarboxylate in the insoluble portion according to the reaction time and reaction temperature of a reaction performed by adding hydrogen peroxide and acetic acid to lignin.
3 is a graph comparing FT-IR spectra of kraft lignin and polycarboxylate of the receptor.
4 is a ¹³ C-NMR spectrum of kraft lignin and polycarboxylate of the receptor.
5 is a graph showing the analysis content of each element of kraft lignin and polycarboxylate of the accommodation part.
6 is a graph showing the result of measuring the charge density of kraft lignin and polycarboxylate of the accommodation part.
It is revealed that the accompanying drawings are exemplified as a reference for understanding the technical idea of the present invention, and the scope of the present invention is not limited thereby.

Hereinafter, the configuration of the present invention guided by various embodiments of the present invention and effects resulting from the configuration will be described with reference to the drawings. In the description of the present invention, if it is determined that the subject matter of the present invention may be unnecessarily obscured as it is obvious to those skilled in the art with respect to related known functions, the detailed description thereof will be omitted.

1 is a schematic flowchart of a method for producing polycarboxylate according to an embodiment of the present invention.

Hereinafter, a method for producing a polycarboxylate according to an embodiment of the present invention will be described with reference to FIG. 1 .

First, the step of preparing lignin is performed.

There are two main methods for preparing lignin. The first method utilizes by-products from the pulping process, and the second method selectively hydrolyzes polysaccharides and produces lignin as a solid residue of the process leaving some condensed state. Such lignin is prepared from kraft lignin, sulfite lignin, organic solvent lignin, steam explosion lignin, and the like through various pretreatment processes.

In the present invention, the experiment was conducted using kraft lignin, but the present invention is not limited thereto, and other types of lignin may be used.

The kraft process is a process that occupies about 90% of the pulp production process, and a large amount of lignin is contained in the black liquor generated in the process of cooking wood at about 150-180 ° C in sodium hydroxide and sodium sulfide aqueous solution. Kraft lignin can be obtained by recovering the used chemicals from the black liquor and removing the moisture.

In the step of preparing the lignin, a fine powdering process is performed through freeze milling in order to increase the reactivity of the prepared lignin.

After performing the step of preparing the lignin, the step of adding hydrogen peroxide and acetic acid together to the prepared lignin and reacting it to produce a reactant including polycarboxylate is performed.

At this time, the ratio of lignin, hydrogen peroxide, and acetic acid is preferably 1 g: 5 to 7 ml: 1.25 to 1.75 ml in order to improve the reaction efficiency.

Lignin has an aromatic skeleton, and one of the methods for producing polycarboxylate is that a part of the ring structure of the aromatic skeleton is ring-opened and a carboxyl group is introduced. The ring opening of the aromatic ring structure of lignin and the introduction of a carboxyl group can be performed using peracetic acid, but when peracetic acid is separately prepared and reacted with lignin, the reaction is excessive and a sufficient amount of polycarboxylate is not produced.

Accordingly, in the present invention, sufficient production of polycarboxylate was induced by adding hydrogen peroxide and acetic acid together to lignin to induce a slower reaction compared to the case where peracetic acid was separately prepared and added. In addition, in the step of generating the reactant, the amount of carboxyl groups introduced while the aromatic skeleton of lignin is ring-opened may be increased by performing the reaction at a temperature of 30 to 70° C. for 40 to 80 minutes.

When the step of generating the reactant is completed, a step of adding an excess of water to the reactant is performed. Addition of excess water to the reaction results in a sharp change in pH. Depending on the pH change, the polycarboxylate of the insoluble part and the polycarboxylate of the water soluble part are separated. That is, the polycarboxylate of the insoluble part is precipitated.

Next, a step of separating the polycarboxylate in the insoluble portion and the polycarboxylate in the accommodation portion through centrifugation is performed. The insoluble part means precipitated without being dissolved in water, and the accommodating part means dissolved in water.

The polycarboxylate of the insoluble part can be obtained in a solid phase through a freeze-drying process, and the polycarboxylate of the aqueous part removes unreacted reagents, low molecular weight reaction products, and polycarboxylate through dialysis.

The polycarboxylate in the insoluble part can be used as an adsorbent for adsorption of positively charged substances, and the polycarboxylate in the receiving part can be used as a concrete admixture to improve the fluidity of concrete.

Since the polycarboxylate prepared by the method for preparing a polycarboxylate of an example of the present invention described above has a large amount of carboxyl groups introduced while the aromatic skeleton of ligrin is ring-opened, the prepared polycarboxylate of the insoluble portion is used as an adsorbent. Adsorption performance is improved when used as a concrete admixture, and when the prepared polycarboxylate of the receiving part is used as a concrete admixture, the fluidity of concrete is higher than that of conventional commercially available concrete admixtures.

Let's look at the method for producing a polycarboxylate of an example of the present invention and the characteristics of the prepared polycarboxylate through the examples below.

Example 1

As the kraft lignin used in the present invention, kraft lignin provided by Moorim P&P was used. Kraft lignin was finely powdered through freeze milling. In addition, in the present invention, the ratio of lignin, hydrogen peroxide, and acetic acid was 2 g: 12 ml: 3 ml so as to satisfy the mixing ratio of hydrogen peroxide:acetic acid 1:4 in which hydrogen peroxide and acetic acid react to produce the most peracetic acid.

On the other hand, in order to examine the effect of reaction time and reaction temperature, the ratio of lignin, hydrogen peroxide, and acetic acid was 2 g: 12 ml: 3 ml, and the reaction temperature was 20 ° C., 40 ° C., 60 ° C., and the reaction time After reacting for 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, and 120 minutes, excess water was poured to obtain an insoluble portion, and the content of hydroxyl groups in the insoluble portion was compared by type.

Table 1 below shows the content of each type of hydroxyl group in kraft lignin, and FIG. 2 shows the result of measuring the content of each type of hydroxyl group according to the reaction time and reaction temperature of the reaction performed by adding hydrogen peroxide and acetic acid to lignin.

Aliphatic OH
(mmol/g) Syringyl OH
(mmol/g) Guaiacyl OH
(mmol/g) COOH
(mmol/g) kraft lignin 0.64 2.59 1.25 0.25

Compared with kraft lignin, the carboxyl group content increased in all conditions after the reaction. This is a result showing that even when hydrogen peroxide and acetic acid are added to lignin without separately preparing peracetic acid, the aromatic ring structure of lignin is cleaved and a carboxyl group is introduced.

However, when the reaction temperature is 20 ° C, the content of carboxyl groups introduced is low even when the reaction time is increased, and when the reaction time is 180 minutes, about 0.5 mmol/g of carboxyl groups are introduced, resulting in a very long production time. have.

On the other hand, when the reaction temperature is 40 ℃, 0.5 mmol/g or more of carboxyl groups are introduced when the reaction time is 40 minutes or more, and even if the reaction time exceeds 80 minutes, the amount of carboxyl groups introduced does not increase significantly or rather decreases. it can be seen that

This tendency is the same even when the reaction temperature is 60°C. That is, until the reaction time is 80 minutes, the content of carboxyl groups increases, and thereafter, it tends to decrease. The decrease in the carboxyl group content is due to the severe reaction conditions, and since an additional reaction occurred in the carboxyl functional group, the carboxyl group content tends to decrease. As described above, when peracetic acid is separately prepared and reacted with lignin, it is seen that the amount of polycarboxylate produced is reduced for the same reason.

Considering the results of Table 1 and FIG. 2, in the step of generating a reactant, the reaction is preferably performed at a temperature of 30°C to 70°C for 40 minutes to 80 minutes. More preferably, when the reaction is carried out under the conditions of a reaction temperature of 60° C. and a reaction time of 80 minutes, a maximum of carboxyl groups can be introduced into the insoluble portion. From these results, since the reaction takes place in the same kraft lignin, it is obvious that the carboxyl group will be introduced to the maximum if the reaction is carried out under the conditions of a reaction temperature of 60 ° C. and a reaction time of 80 minutes in the aqueous portion produced together with the insoluble portion.

Table 2 below is the result of measuring the yield of the insoluble portion according to the reaction temperature and reaction conditions.

20℃ 40℃ 60℃ 80℃ 100℃ 120℃ 180℃ 20 minutes 72.41% 71.83% 70.95% 69.67% 68.67% 66.61% 64.85% 40 minutes 74.9% 70.57% 66.91% 64.63% 61.7% 57.22% 51.3% 60 minutes 65.97% 52.16% 38.1% 29.07% 21.83% 15.62% 10.05%

Referring to Table 2, by adjusting the reaction temperature and reaction time, the yield of the insoluble portion or the yield of the receiving portion can be adjusted. That is, while reacting the lignin, the amount of the insoluble part and the accommodating part to be produced can be selected as needed.

Example 2

A reaction for preparing polycarboxylate was performed with the same composition, reaction time, and reaction temperature as in Example 1, and the change in molecular weight of the insoluble part was confirmed through Gel Permeation Chromatograph (GPC) analysis.

The number average molecular weight (Mn) and polydispersity (PDI) analysis results of kraft lignin are shown in Table 3. It was.

M _n PDI kraft lignin 1242 3.10

20 minutes 40 minutes 60 minutes 80 minutes 100 minutes 120 minutes 180 minutes 20 ℃ M _n 1168 1175 1206 1196 1247 1284 1370 PDI 3.31 3.40 3.46 3.47 3.63 5.13 6.00 40 ℃ M _n 1218 1280 1297 1417 1590 1480 1607 PDI 3.45 3.57 3.89 4.55 5.49 4.90 7.15 60 ℃ M _n 1517 1780 PDI 4.97 32.49

Referring to Tables 3 and 4, as the reaction time and reaction temperature increased, the molecular weight of the insoluble portion showed a tendency to increase. Various metal ions exist in kraft lignin, and some ions capable of radicalizing hydrogen peroxide, such as iron ions, exist. The hydroxyl radical generated from hydrogen peroxide in the presence of a specific metal ion radicalizes lignin and can cause both a decomposition reaction and a condensation reaction at the same time. As the reaction conditions become more severe, the molecular weight increases through the condensation reaction.

In addition, it can be seen that the PDI tends to increase as the reaction time and reaction temperature increase. An increase in PDI means that substances of various molecular weights exist. This is to disprove the existence of a product with a higher degree of condensation because the condensation reaction of kraft lignin was violently caused by the hydroxyl radical generated from hydrogen peroxide.

When the reaction temperature was 60 °C, the PDI showed a tendency to rapidly increase at the reaction time of 40 minutes. Also, under the condition that the reaction time was longer than 60 minutes, measurement was impossible because the sample was not dissolved in the solvent used for molecular weight analysis. This is because a large number of lignins, which were changed insoluble in organic solvents as a number of carboxyl groups were introduced, and whose molecular weight increased rapidly due to a condensation reaction by hydroxyl radicals, were present.

Example 3

In order to perform the analysis on the receptor, in Example 1, a reaction temperature of 70° C. and a reaction time of 80 minutes, which are the reaction conditions for maximally introducing a carboxyl group, lignin: hydrogen peroxide: acetic acid in a ratio of 2 g: 12 ml: 3 ml. The reaction was carried out by fixing. After the reaction, an excess of water was added to obtain an aqueous part, and the water-insoluble part and the aqueous part were separated by centrifugation. A dialysis process was performed for 24 hours to remove unreacted reagents and low molecular weight reaction products in the receiver.

First, organic solvent GPC and water-soluble GPC were used to measure the molecular weight of the kraft lignin and the water-soluble portion, respectively. In the case of kraft lignin, an organic solvent GPC analysis was performed after performing an acetylation reaction to measure the molecular weight, and a water-soluble GPC analysis was performed for the analysis of the receptor part.

Table 5 is a table showing the Mn and PDI results of the receptors (before and after dialysis) after the reaction with kraft lignin and peracetic acid.

M _n PDI kraft lignin 1242 3.10 Receptor (before dialysis) 1634 1.41 Receptor (after dialysis) 2898 1.66

When M _n and PDI of kraft lignin were compared, M _n increased and PDI decreased after peracetic acid reaction followed by dialysis. This is because M _n increases and PDI decreases because low molecular weight reaction products are removed during dialysis.

Next, FT-IR spectroscopy was performed to compare the functional groups of the kraft lignin and the receptor.

3 is a graph comparing FT-IR spectra of kraft lignin and polycarboxylate of the receptor.

In the FT-IR spectrum, the peaks of 1715 and 1172 cm ^-1 are peaks shown by C = O stretching and CO stretching of the carboxyl group, respectively. It was confirmed that these two peaks appeared in the rate spectrum.

In particular, a distinct peak intensity increased at 1715 cm ^-1 , which has been reported as a characteristic peak of a carboxyl group, and is a result of the introduction of a carboxyl group after the peracetic acid reaction. In addition, peak intensity was decreased in the spectrum of polycarboxylate of the receptor compared to kraft lignin in the 1400-1600 cm ^-1 region. The peaks in this region are reported as peaks generated by the aromatic ring structure, and since the carboxyl group is introduced through the cleavage reaction of the aromatic ring structure through the peracetic acid reaction, it can be judged that the peak disappears from the polycarboxylate spectrum of the receptor. can

Next, ¹³ C NMR analysis was performed to analyze the binding pattern between the functional groups and carbon atoms of the polycarboxylate of the kraft lignin and the acceptor part. 4 is a ¹³ C NMR spectrum of kraft lignin and receptors.

Both samples of kraft lignin and polycarboxylate of the receptor part showed peaks near the 180 ppm peak, which means that a carboxyl group exists in the polycarboxylate structure of the kraft lignin and the receptor part. In the case of polycarboxylate of the receptor, an additional peak appeared in a chemical shift different from that of kraft lignin. This is because the carboxyl group was introduced, but the chemical environment such as the surrounding functional groups or element arrangement structure is different from the carboxyl group present in the kraft lignin. It is considered to have been seen

In addition, when compared with kraft lignin, the peak intensity was decreased around 148 ppm of polycarboxylate in the receptor. ^{In 13} C NMR, the peak around 148 ppm is a carbon atom peak in the aromatic ring structure, and it is seen that the intensity of the peak around 148 ppm is reduced due to the reduction of functional groups due to the cleavage reaction of the benzene ring during the peracetic acid reaction. Additionally, a peak around 126 ppm is generated in the ¹³ C NMR spectrum of the polycarboxylate of the acceptor after the peracetic acid reaction. This peak has been reported to be a peak generated by a carbon-carbon double bond, and according to the peracetic acid reaction mechanism, the benzene ring is broken and a carbon-carbon double bond and a carboxyl group are generated together.

Also, the intensity of the peak at 55-57.5 ppm decreased after the reaction. This is the peak intensity corresponding to the carbon atom of the methoxyl group, and in the carboxylation reaction by peracetic acid, the peak intensity in this chemical shift is decreased because oxidation reaction starts at the methoxyl group and carboxylic acid is introduced.

Next, elemental analysis was performed to analyze the change in the proportion of constituent elements after the peracetic acid reaction. 5 is a graph showing the analysis content of each element of kraft lignin and polycarboxylate of the accommodation part.

In the case of kraft lignin, the contents of C, O, H, N, and S are 59.51, 31.70, 5.87, 0.01, and 2.91%, respectively, and in the case of polycarboxylate in the water receiving part, the content of each element is 49.78, 45.26, 4.19, 0.13 and 1.25%. After the peracetic acid reaction, the oxygen element ratio in the receptor structure was increased by 13.56% compared to the kraft lignin, which is due to the carboxylation reaction of the syringyl unit and the guaiacyl unit in the kraft lignin. In addition, since the sulfur content in the polycarboxylate structure of the receiving part is reduced by 1.66% compared to kraft lignin, the desulfurization reaction also occurs during the peracetic acid reaction.

Finally, the charge density after the peracetic acid reaction of kraft lignin was measured using a particle charge detector (PCD). 6 is a graph showing the result of measuring the charge density of kraft lignin and polycarboxylate of the accommodation part. The charge density of kraft lignin was 0.00 meq/g, and the charge density of polycarboxylate in the receptor was -1.94 meq/g. The charge density was increased in the negative direction by the carboxyl group introduced through the peracetic acid oxidation reaction. That is, the charge density is closely related to the amount of introduced carboxyl groups.

Table 6 below is the result of measuring the charge density of LS (Lignosulfonate) and PCE (Polycarboxylate ether), which are products sold as concrete admixtures in the industry.

kraft lignin LS PCE Example 3 Charge density (meq/g) 0 -0.08 -1.19 -1.94

Referring to Table 6, it can be seen that Example 3 prepared by the manufacturing method of the present invention has a very low charge density compared to commercial products such as LS or PCE. In light of previous studies that the higher the charge density of the concrete admixture in the negative direction, the greater the fluidity of the cement, the polycarboxylate prepared by the manufacturing method of the present invention, especially the polycarboxylate dissolved in water, has improved fluidity. It is expected to have great significance as a concrete admixture for improvement. In particular, the difference in charge density between PCE and Example 3 is due to the difference in the amount of carboxyl groups introduced. In PCE, a carboxyl group is attached only to the terminal portion of the molecular structure, but in Example 3 of the present invention, a larger amount of carboxyl group was introduced, resulting in a difference in charge density.

Example 4

In order to evaluate the performance of the polycarbonate prepared by the method of the present invention as a concrete admixture, a cement fluidity measurement test was performed. The cement fluidity measurement test was conducted with a mortar table test according to KS L 5111.

For the concrete composition, 600 g of cement, 159.7 g of water, and 0.3 g of a concrete admixture were mixed slowly for 1 minute and rapidly for 3 minutes. As concrete admixtures, kraft lignin, LS, PCE, and polycarboxylate of the receiving part of Example 3 were used, respectively.

Table 7 below is the measurement result of the cement dough diameter according to the mortar table test results.

kraft lignin LS PCE Example 3 Cement dough diameter (mm) 177 (±1.73) 189.33 (±4.16) 199.67 (±1.53) 206.11 (±1.36)

As can be seen from Table 7, in the case of Example 3 of the present invention, it was confirmed that the higher performance, that is, the cement dough diameter was 200 mm or more compared to the product used in the field.

The protection scope of the present invention is not limited to the description and expression of the embodiments explicitly described above. In addition, it is added once again that the protection scope of the present invention cannot be limited due to obvious changes or substitutions in the technical field to which the present invention pertains.

Claims (11)

As a method for producing polycarboxylate using lignin,
reacting the lignin with hydrogen peroxide and acetic acid to produce a reactant containing polycarboxylate; and
After performing the step of generating the reactant, adding excess water to the reactant to separate the polycarboxylate in the insoluble part and the polycarboxylate in the receiving part; Poly using lignin, characterized in that it is carried out including Method for producing carboxylate.
According to claim 1,
The separating step is a method for producing polycarboxylate using lignin, characterized in that the polycarboxylate of the receiving portion and the polycarboxylate of the insoluble portion are separated from each other by centrifugation.
3. The method of claim 2,
The method for producing polycarboxylate using lignin, characterized in that it further comprises; dialysis of the separated polycarboxylate in the receiving part to remove a low molecular weight reaction product.
According to claim 1,
The step of generating the reactant is a method for producing polycarboxylate using lignin, characterized in that the reaction is performed at a temperature of 30 ° C. to 70 ° C. for 40 minutes to 80 minutes.
According to claim 1,
The method for producing polycarboxylate using lignin, characterized in that the ratio of lignin, hydrogen peroxide, and acetic acid in the step of generating the reactant is 1 g: 5 to 7 ml: 1.25 to 1.75 ml.
The method of claim 1,
The method for producing polycarboxylate using lignin, characterized in that the lignin is kraft lignin.
A polycarboxylate prepared using lignin and dissolved in water, characterized in that the charge density is -1.9 meq/g or less.
Concrete admixture comprising polycarboxylate prepared using lignin and dissolved in water.
9. The method of claim 8,
Concrete admixture, characterized in that the charge density of polycarboxylate dissolved in water is -1.9 meq/g or less.
9. The method of claim 8,
Concrete admixture, characterized in that the dough diameter of the mortar table test performed by mixing 600 g of cement, 159.7 g of water, and 0.3 g of the concrete admixture is 200 mm or more. delete

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