KR101466011B1 - Preparation of acrylic resin and alumina from waste-scagliola by low-temperature pyrolysis under oxygen atmosphere - Google Patents

Abstract

The present invention relates to a method for producing high white aluminum hydroxide and high purity alumina by collecting an acrylic resin from waste scagliola. The acrylic resin can be collected from waste scagliola at a high yield using aerobic low temperature pyrolysis. Moreover, high white aluminum hydroxide is obtained from residues through amorphous pseudo-boehmite in order to be recycled as a raw ingredient for scagliola or calcined so that high purity alumina can be produced. Accordingly, the method of the present invention is an environmentally-friendly resource circulation-type technique.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acrylic resin and an alumina, and more particularly, to an acrylic resin and an alumina. 2. The acrylic resin and alumina according to claim 1,

More particularly, the present invention relates to a method for recovering an acrylic resin from a crude marble and producing a high-purity aluminum hydroxide and high purity alumina.

Artificial marble is a polymethyl methacrylate (PMMA), methyl methacrylate (MMA), such as acrylic resin, about 30 to 45 inorganic filler of about 45-65% by weight, such as aluminum hydroxide in the weight% as testimony color containing and TiO ₂ , SiO _2, and the like. Mixing ratios are somewhat different for each manufacturer.

Most of the crude marbles generated after the use of such artificial marble are treated as waste in the workplace and are simply landfilled. As of 2012, about 25,000 tons of crude marble has been generated in Korea, causing economic, environmental and social problems not only in Korea but also overseas.

Accordingly, some companies have developed a method for producing alumina by recovering an acrylic resin through a pyrolysis technique and heat-treating the residue (see Korean Patent No. 10-0891378). Since the conventional pyrolysis technique is carried out without introduction of air, the pyrolysis temperature has to be maintained at 500 ° C or higher.

However, when the pyrolysis temperature is higher than 500 ° C, flame is generated in the kiln due to ignition of gas during pyrolysis of crude marble, resulting in loss of acrylic resin to be recovered. Also, when pyrolysis proceeds at a temperature of 500 ° C. or higher, pyrolysis of aluminum hydroxide used as a mixture filler rapidly proceeds, resulting in phase transformation from gibbsite to gamma-alumina (γ-Al ₂ O ₃ ) .

In addition, according to the conventional method, alumina produced from marble-treated marble contains a considerable amount of impurities and is not suitable for use as general alumina, and the process itself is also limited in commercialization.

Korean Registered Patent No. 10-0891378 (A & I Co., Ltd.) 2009.04.02.

Accordingly, it is an object of the present invention to provide an efficient method for producing an acrylic resin and high purity alumina from a closed marble.

(A) recovering an acrylic resin and an amorphous pseudo-boehmite from aerobic crude marble using aerobic low-temperature pyrolysis; (b) dissolving the amorphous pseudo-boehmite in caustic soda to prepare a sodium aluminate solution; (c) removing the impurities of the sodium aluminate solution and precipitating to produce a whitening aluminum hydroxide; And (d) high temperature calcination of the high-purity aluminum hydroxide to obtain high purity alumina. The present invention also provides a method for producing an acrylic resin and alumina from a crude marble.

According to the present invention, the acrylic resin can be recovered at a high yield by using an aerobic low-temperature pyrolysis reaction from the crude marble. In addition, it is an eco-friendly resource recycling technology since aluminized aluminum hydroxide is obtained from the residue through amorphous pseudo-boehmite to recycle it as a raw material for artificial marble or high-temperature calcination to produce alumina of high purity.

FIG. 1 illustrates a method for recovering acrylic resin from crude marble and producing high-purity aluminum hydroxide and high purity alumina according to an example of the present invention.
Fig. 2 schematically shows an example of the construction of a continuous rotary kiln used for aerobic low-temperature pyrolysis.
Figure 3 shows the internal temperature and air influx of the continuous rotary kiln used for aerobic low temperature pyrolysis in step 1 of example 1.
FIG. 4 shows X-ray diffraction (XRD) analysis results of the phase transition characteristics depending on the pyrolysis temperature of the waste marble and recovered pseudo-boehmite.

Hereinafter, a method of treating the marble of the present invention according to the present invention will be described step by step with reference to FIG.

Low-temperature pyrolysis step of aerobic parts of crude marble (acrylic resin and amorphous pseudo-boehmite recovery)

The crude marble used as the starting material is not only sludge and scrap generated in the process of polishing and cutting in the manufacturing process of the artificial marble used as building material but also the crude marble collected as industrial waste after use.

The crude marble is subjected to aerobic low-temperature pyrolysis, in which gaseous acrylic resin and solid amorphous pseudo-boehmite are recovered.

According to the present invention, by keeping the aerobic atmosphere during pyrolysis, combustion by ignition can be prevented and thermal decomposition can be performed even at a relatively low temperature. Accordingly, the amorphous pseudo-boehmite (AlOOH) can be recovered by separating and recovering the acrylic resin at a high recovery rate while preventing carbonization, and at the same time decomposing only a few crystals through low-temperature thermal decomposition of aluminum hydroxide mixed as a filler.

The aerobic low-temperature pyrolysis is performed at a temperature of less than 500 ° C, for example, at a temperature of 200 ° C to less than 500 ° C, and more specifically, at a temperature of 350 to 450 ° C. When the temperature at the time of pyrolysis is 500 ° C or more, the thermal decomposition of the aluminum hydroxide used as the mixture filler rapidly proceeds, and the phase transition from gibbsite to gamma-alumina (γ-Al ₂ O ₃ ) In the process, the dissolution reaction of aluminum by caustic soda is very low and the yield may be greatly reduced.

Further, the inflow amount of air at the time of thermal decomposition can be controlled to 1 to 10 m ³ / min, preferably 3 to 5 m ³ / min. If excessive oxygen is introduced, carbonization proceeds and not only the recovery of acryl but also the recovery of amorphous pseudo-boehmite may not be possible.

The supply amount of crude marble as a waste at the time of pyrolysis can be 50 to 150 kg / hr, for example, 80 to 120 kg / hr.

The amount of feedstock and the amount of air inflow can be appropriately adjusted according to the change of the other process conditions.

The aerobic low-temperature pyrolysis can be carried out using a continuous rotary kiln. An example of the structure of a continuous rotary kiln usable in the present invention is shown in Fig.

The continuous rotary kiln preferably has at least three heat treatment zones, and may have, for example, three to five zones. In addition, the continuous rotary kiln is configured to be capable of controlling the inflow of air and the flow rate of each section, so that low-temperature pyrolysis can be performed by continuously supplying oxygen or air in an appropriate amount for each section.

As an example, the continuous rotary kiln may be configured to sequentially pass through (i) a preheating section in a temperature range of 100 to 300 ° C, (ii) a reaction section in a temperature range of 300 to 450 ° C, and (iii) At this time, an appropriate amount of oxygen or air can be continuously supplied into the preheating section and the reaction section (see FIG. 3).

The continuous rotary kiln can maintain the inside thereof at an appropriate temperature by indirectly transferring heat from the outside (resistance heating method).

The acrylic resin pyrolyzed through the continuous rotary kiln can be sucked in and discharged out as a gaseous state, and the amorphous pseudo-boehmite contained in the remaining filler can be recovered in a solid powder state.

The acrylic resin recovered in the gaseous state through the aerobic low temperature heat treatment can be regenerated with an acrylic resin (PMMA, MMA, etc.) which can be recycled through the condensation process.

The amorphous pseudo-boehmite recovered in the solid state is a phase-transformed material in which aluminum hydroxide used as a filler of artificial marble is partially removed by volatilization and elimination of some crystals in the pyrolysis process, and major impurities other than alumina, namely TiO ₂ , SiO ₂ , Na ₂ O, CaO, Fe ₂ O ₃ , and the like. According to the present invention, the purity of the amorphous pseudo-boehmite recovered through the aerobic low-temperature heat treatment can be 97.5% or more.

Dissolution step of amorphous pseudo-boehmite (preparation of sodium aluminate solution)

The solid amorphous pseudo-boehmite recovered in the previous step is dissolved in caustic soda (NaOH) and made into a sodium aluminate solution.

At this time, the concentration of the caustic soda may be 200 to 250 g / L, and more preferably 210 to 230 g / L. Further, the temperature of the dissolution reaction may be from 150 to 200 캜, more preferably from 160 to 180 캜. In addition, the molar ratio of dissolution (the molar ratio of pseudo-boehmite to caustic soda) may be 0.50 to 0.70, and more preferably 0.55 to 0.65.

The dissolution process can be performed by adding caustic soda and amorphous pseudo-boehmite to the high-pressure reactor or the dissolution tank.

The impurity removal and precipitation step of the sodium aluminate solution

The sodium aluminate solution prepared in the previous step is subjected to impurity removal, filtration and precipitation processes to produce a high-color aluminum hydroxide.

First, slaked lime (Ca (OH) ₂ ) is added to the sodium aluminate solution to remove impurities. The impurities include the removal and un-dissolved residues of organics which subsequently affect the color of the alumina. The addition of the slaked lime causes reaction adsorption of the organic material and organic impurities can be removed through filtration.

The added amount of the slaked lime may be 5 to 15 g / L, and more preferably 8 to 12 g / L. The reaction temperature at the time of removing the impurities may be from 50 to 100 캜, and more preferably from 70 to 90 캜. The reaction time for removing the impurities may be 30 to 120 minutes, more preferably 50 to 70 minutes. The filtration can be carried out using a belt filter, a granular filtration filter, a press filter, a centrifuge or the like.

From the purified sodium aluminate solution, temperature difference and seed input amount are adjusted to precipitate a whitish-colored aluminum hydroxide. Since nucleation, nucleation and agglomeration are carried out through the precipitation process, the purity, average particle size, distribution, color, etc. of aluminum hydroxide obtained depending on the temperature, time, and amount of seed are introduced. For example, the amount of seed introduced in the seawater can be 10 to 40 g / L, and the precipitation temperature can range from 45 to 85 ° C. In general, the higher the initial precipitation temperature and the smaller seed input, the larger the average particle size. The lower the initial precipitation temperature and the larger the seed loading, the smaller the average particle size. Thus, the particle size of the coarse- Quality control is possible.

The obtained aluminum hydroxide slurry can be made into a whitish-colored aluminum hydroxide powder through a filtration / drying process. The high-brightness aluminum hydroxide produced in this step may have an average particle size of 10 to 100 mu m. In addition, the whiteness degree of the produced high-brightness aluminum hydroxide may be 97.5% or more, and may be 98.0% or more. In addition, the purity of the produced high-purity aluminum hydroxide may be 99.8% or more. The whitening aluminum hydroxide may be recycled as a filler of artificial marble.

High temperature calcination of aluminum hydroxide (high purity alumina production)

The high-purity aluminum hydroxide obtained in the previous step can be made into high purity alumina through high-temperature firing.

The high-temperature firing may be performed starting at about 200 ° C and raising the temperature to about 1300 ° C. At this time, the aluminum hydroxide is phase-changed into various forms as the crystal water is decomposed, and a loss on ignition (LOI) of about 34.5% occurs. Through the high-temperature firing, aluminum hydroxide finally undergoes phase transformation to α-alumina through phase transition to pseudo-boehmite, γ-alumina and θ-alumina. Fig. 4 shows the phase transition results (XRD analysis) of aluminum hydroxide according to the pyrolysis temperature.

The high-temperature firing process may be performed using a continuous rotary kiln. The continuous rotary kiln may have at least three heat treatment zones, and a dam is preferably formed between the heat treatment zones to increase the residence time. Especially, in order to cope with the sudden increase of specific surface area and change of physical properties in the heat treatment zone of 200 ~ 600 ℃, dam is formed at 200 ~ 600 ℃ heat treatment zone, As shown in FIG.

The purity of the final alumina (a-alumina) obtained through high-temperature firing may be higher than 99.8%.

Hereinafter, the present invention will be described in more detail by way of examples. The following examples are illustrative of the present invention, but the present invention is not limited to the following examples.

Example 1

Step 1) Low-temperature pyrolysis of aerobic lower marble

The aerobic low temperature pyrolysis process of the crude marble was carried out using a continuous rotary kiln having the constitution of FIG. As shown in FIG. 3, the rotary kiln has a chamber shape divided into three sections, and the inflow and flow of air are controlled for each section. The amount of the marble was 100 kg / hr, and the internal air temperature was maintained at 350 to 450 ° C., and the supply flow rate of the air was controlled at 3 to 5 m ³ / min.

Acrylic resin (PMMA, MMA, etc.) and amorphous pseudo-boehmite (AlOOH) were recovered through pyrolysis.

The chemical composition of the recovered pseudo-boehmite (AlOOH) was analyzed and shown in Table 1.

division Containing components of amorphous pseudo-boehmite AlOOH TiO ₂ SiO ₂ Na ₂ O Fe ₂ O ₃ CaO content 97.5% 1.5% 0.6% 0.3% 0.07% 0.08%

As shown in Table 1, amorphous pseudo-boehmite recovered through aerobic low-temperature pyrolysis showed a high purity of 97.5%.

Step 2) Melting process of amorphous pseudo-boehmite

The amorphous pseudo-boehmite obtained in the above step 1 was dissolved in a caustic soda solution using an autoclave. The autoclave used was a stainless steel capacity of 10 L capacity capable of controlling the stirring speed and capable of raising the temperature up to 200 ° C. The conditions of the dissolving process were set at a melting temperature of 150 to 180 ° C, a caustic soda (NaOH) concentration of 200 to 220 g / L, and a molar ratio of molar ratio (pseudo-boehmite to caustic soda) of 0.60 to 0.65. The dissolution time was 60 minutes and the stirring rate was fixed at 200 rpm. After dissolution, the dissolution rate (%) was calculated from the amount of undissolved amorphous pseudo-boehmite, and the results are shown in Table 2 below.

Melting temperature Caustic soda
density Dissolution rate (Molar ratio of dissolution = 0.60) (Molar ratio of dissolution = 0.65) 150 ℃ 200g / L 52% 52% 220g / L 55% 54% 160 ° C 200g / L 78% 75% 220g / L 92% 90% 170 ℃ 200g / L 95% 90% 220g / L 100% 100% 180 DEG C 200g / L 100% 100% 220g / L 100% 100%

As shown in Table 2, the dissolution rate of amorphous pseudo-boehmite increased with increasing reaction temperature and caustic soda concentration. In particular, it can be seen that the most efficient dissolution was carried out when the dissolution conditions were a reaction temperature of 170 DEG C, a caustic soda concentration of 220 g / L and a molar ratio of molar ratio of 0.60 to 0.65.

Step 3) Production of high-brightness aluminum hydroxide by impurity removal and precipitation

In step 2, slaked lime was added to the sodium aluminate solution prepared under the conditions of a melting temperature of 170 ° C, a caustic soda concentration of 220 g / L and a molar molar ratio of 0.65 to remove impurities. At this time, impurities were removed at 80 ° C for 60 minutes at an amount of 5-15 g / L added to the slaked lime. After the reaction, the sodium aluminate solution was removed by using a GF / C filter to remove the additive and the non-dissolved residue. Subsequently, precipitation reaction was carried out in purified sodium aluminate solution for 48 hours to obtain aluminum hydroxide. The whiteness and average particle size of the obtained aluminum hydroxide were measured.

Table 3 shows changes in whiteness of aluminum hydroxide depending on the amount of slaked lime added at the time of removing the impurities.

Amount of slaked lime added Aluminum hydroxide whiteness 0g / L 87.5% 5g / L 93.4% 10 g / L 97.5% 15g / L 98.0%

As shown in Table 3, the whiteness of aluminum hydroxide was particularly excellent when the amount of slaked lime was about 10 g / L or more.

Table 4 shows changes in the average particle size of aluminum hydroxide depending on the initial precipitation temperature and seed input.

Precipitation temperature Aluminum hydroxide average particle size by seed input 10 g / L 20g / L 30g / L 40g / L 85 ~ 65 ℃ 88 탆 72 탆 50 탆 40 탆 70 ~ 50 ℃ 76 탆 63 탆 35 탆 28 탆 60 to 45 ° C 52 탆 45 탆 25 m 18 탆

As shown in Table 4, the average particle size was increased as the initial precipitation temperature was higher and the seeding amount was smaller. As the initial precipitation temperature was lower and the seeding amount was larger, the average particle size was sharply decreased. Therefore, it can be seen that quality control can be made for the particle size of the high-brightness aluminum hydroxide by use or demand.

Table 5 shows the chemical composition of aluminum hydroxide obtained by analysis.

division Containing component of aluminum hydroxide Al (OH) ₃ Fe ₂ O ₃ Na ₂ O SiO ₂ CaO TiO ₂ content 99.8% 0.007% 0.10% 0.007% 0.004% 0.003%

As shown in Table 5, the precipitated aluminum hydroxide had excellent purity.

Step 4) Production of high purity alumina by high temperature calcination

The aluminum hydroxide prepared in the step 3 was calcined at a high temperature using a rotary kiln at a temperature of about 200 ° C and a temperature of about 1300 ° C. At this time, a dam was formed inside the kiln in the range of 200 to 600 ° C.

XRD was measured according to the sintering temperature interval of aluminum hydroxide and is shown in Fig. As can be seen from FIG. 4, as the firing temperature of the aluminum hydroxide is increased, it is formed into alumina through the phase transition. The average particle size of the alumina finally obtained was 23.5 mu m. The components of the obtained alumina were analyzed and are shown in Table 6 below.

division Alumina Containing Component Al ₂ O ₃ Fe ₂ O ₃ Na ₂ O SiO ₂ CaO TiO ₂ content 99.8% 0.01% 0.15% 0.01% 0.006% 0.004%

As shown in Table 6, the purity of alumina obtained after firing was excellent.

<Calculation of yield rate of recycled raw materials from marine marine vessels>

In Step 1 of Example 1, 360 kg of crude marble as a raw material was charged, and the raw material was composed of 162 kg of acrylic resin, which accounts for 45% of the raw material, and 198 kg of aluminum hydroxide, which accounts for 55%.

In step 1 of Example 1, about 36 L and 6 L of gaseous acrylic resin were present in the main tank and the exit collection tank, respectively, to give a total of 42 L of gaseous acrylic resin, which was converted to a specific gravity of 0.956 g / L ) Was calculated to be 40 kg, which was about 25% as compared with the 162 kg acrylic resin in the crude marble of the raw material. In addition, when the acrylic resin (4L) contained in 2% of 183L of condensed water obtained in the subsequent step is included, the yield can be calculated to be about 27%. 94 kg of the acrylic resin not obtained was judged to be released to the atmosphere during the dust collecting treatment and 24 kg was judged to be contained in the piping line and the raw material.

In step 4 of Example 1, about 125 kg of Al ₂ O ₃ powder (purity of about 99.8%) was collected and moisture (35%) and dust (3.5 kg) were removed from 198 kg of aluminum hydroxide present in the crude marble of the raw material. The calculated yield was about 95% except for the Al ₂ O ₃ escaping to the reactor.

In addition, a total of 183 L of condensate was collected over the steps 1 to 4 of Example 1, and the moisture obtained from the actual raw material was found to be about 71 L, excluding about 60% corresponding to the moisture absorbed from the outside air , And about 19.5% of the total weight of the raw marble (360 kg) of the raw material, including 2% of the acrylic resin.

In conclusion, when 360kg of marble is put in, the final amount collected from it is as follows:

- Acrylic resin: 40kg

- Purity 99.8% Al ₂ O ₃ powder: 125 kg

- Condensate: 71kg

Thus, a total of 165 kg of recycled raw material (acrylic resin and Al ₂ O ₃ powder) was obtained from the waste marble (360 kg) and the yield was calculated to be about 45.8%.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It is to be understood that the invention may be practiced within the scope of the appended claims.

Claims (11)

(a) From the marble of the clerk Recovering an acrylic resin and an amorphous pseudo-boehmite using aerobic low-temperature pyrolysis;
(b) dissolving the amorphous pseudo-boehmite in caustic soda to prepare a sodium aluminate solution;
(c) removing the impurities of the sodium aluminate solution and precipitating to produce a whitening aluminum hydroxide; And
(d) high-temperature firing the high-purity aluminum hydroxide to obtain high purity alumina.
The method according to claim 1,
Characterized in that, in step (a), said aerobic low temperature pyrolysis is carried out at a temperature of from 350 to 450 DEG C with an air inflow of from 3 to 5 m &lt; ³ &gt; / min.
The method according to claim 1,
Wherein in step (a), the aerobic low temperature pyrolysis is carried out using a continuous rotary kiln.
The method of claim 3,
Wherein the continuous rotary kiln has at least three heat treatment zones and is configured to control the inflow of air and the flow rate of each zone.
The method according to claim 1,
In step (b), the dissolution is carried out using caustic soda at a concentration of 200 to 250 g / L at a temperature of 150 to 200 DEG C under a molar ratio of molar ratio (molar ratio of pseudo-boehmite to caustic soda) of 0.50 to 0.70 &Lt; RTI ID = 0.0 &gt; 1, &lt; / RTI &gt;
The method according to claim 1,
Wherein in step (c), the impurity removal is to remove the organic impurities by adding slaked lime to the sodium aluminate solution.
The method according to claim 6,
Wherein the impurity removal is carried out under the conditions of a slaked amount of 5 to 15 g / L, a reaction temperature of 50 to 100 ° C, and a reaction time of 30 to 120 minutes.
The method according to claim 1,
A method for producing an acrylic resin and alumina from a waste marble, wherein in step (c), the precipitation is carried out at a seed input amount of 10 to 40 g / L and a reaction temperature of 45 to 85 캜.
The method according to claim 1,
Wherein in step (c), the whiteness of the aluminum hydroxide is 97.5% or more.
The method according to claim 1,
In step (d), the high-temperature calcination is carried out at 200 ° C to 1300 ° C using a continuous rotary kiln, the continuous rotary kiln has at least three heat treatment sections, and the residence time is increased between the heat treatment sections Wherein the dam is formed on the outer surface of the molten marble.
The method according to claim 1,
Wherein in step (d) the purity of said alumina is at least 99.8%.

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