KR100953871B1 - Method on Silicon Compound Recovery from Silicon Waste - Google Patents

Abstract

The present invention relates to a method for recovering a low molecular weight silicone compound from a silicon waste, and more particularly, to treat a silicon waste using mineral oil to recover a low molecular weight silicone compound from D3 to D7, thereby increasing the recovery rate and simultaneously included in the silicon waste. The present invention relates to a method capable of simultaneously recovering a filling.

By carrying out the method of recovering the silicon compound of the present invention, the recovery efficiency of the silicon compound from the silicon waste can be maximized, and the filler contained in the silicon waste can be recovered.

Silicon Waste, Mineral Oil, Low Molecular Silicon Compound, Silicon Monomer, Recovery, Filling

Description

Method for recovering low molecular weight silicon compound from silicon waste

The present invention relates to a method for recovering a low molecular weight silicone compound from a silicon waste, and more particularly, to treat a silicon waste using mineral oil to recover a low molecular weight silicone compound from D3 to D7, thereby increasing the recovery rate and simultaneously included in the silicon waste. The present invention relates to a method capable of simultaneously recovering a filling.

The problem of disposal of polymer materials discarded by consumers after use has become a global environmental problem. The main solution is to depolymerize these polymer wastes into monomers for reuse. Waste organosilicon compounds are no exception, so recycling and using them is a way to prevent environmental pollution. For this purpose the present invention therefore relates to a process for recovering industrially useful silicone containing compounds from said starting materials which are being disposed of.

The amount of silicon rubber waste has increased significantly in recent years. In addition, the molding of silicone rubber produces residues of vulcanized silicone rubber which contain relatively few other impurities than the filler. Silicone rubber has often been used to make or recycle molding, from which waste has been increased. In particular, among the silicone rubbers, in hydraulic liquid silicone rubber, which is used as a sealing material for construction or as an industrial adhesive, there are materials that are cured after opening the package without use or cured by masking tape. On the other hand, in addition to silicone rubbers, it is used as a curing medium or semi-cured product of heating medium or insulating oil, silicone grease to prevent air damage by salt damage or dust, silicone resin for electrical insulation or coating, etc. Wastes of poor quality silicone oil have been generated.

These rubbers include high molecular weight linear polyorganosiloxanes, vulcanizations thereof, crosslinked products, and the like, and further contain fillers such as silica. In the past, most of them have been disposed of as industrial waste.

The amount of silicon rubber waste is increasing markedly, and environmental pollution is becoming a social problem as well as waste plastic. The present invention is a technology that contributes to the prevention of environmental pollution by recycling and utilizing the waste organosilicon compounds discarded after use to solve this problem. To this end, the present invention relates to a process for recovering industrially useful silicon-containing compounds from the starting materials that are being disposed of.

The silicone rubber waste is composed of a crosslinked form of linear polydimethylsiloxane [poly (dimethylsiloxane) (PDMS)] and depolymerization of these to recover mainly the cyclosiloxane monomers hexamethylcyclotrisiloxane (D3) and octamethylcyclotetrasiloxane (D4). to be.

In the prior art, US Pat. No. 2,673,843 discloses a method of partially decomposing a silicone rubber by treating with anhydrous acid or the like at about room temperature. By this method, a mixture of volatile polysiloxane low molecular weight compounds (oligomers) can be obtained. However, before reusing it, a complicated step to remove the acid and the filling is required.

British Patent 716,024 discloses a method of partially hydrolyzing vulcanized silicone rubber using ultra-high temperature steam to regenerate vulcanized silicone rubber. However, in this method, the filler in the silicone rubber cannot be separated and only practical value can be recycled with the silicone rubber mixed with the silicone rubber which is not cured therein.

West German Patent 875,046 discloses a process for producing cyclic polydialkylsiloxanes by heating a hydrolyzed mixture of dialkylsiloxane units and monoalkylsiloxane units under oxygen free conditions. However, the use of vulcanized silicone rubber as well as the method of separating the packing from the product in this case is not described.

Japanese Patent Laid-Open No. 132590/1989 discloses that polyorganosiloxanes can be reacted with an alkoxysilane in the presence of a titanium compound such as tetrabutyl titanate to obtain an organic alkoxysilane different from the alkoxysilane used. Here too, the polyorganosiloxanes used are low molecular weight compounds or polyorganohydrogen siloxanes, and there is an advantage in that various organic alkoxysilanes can be arbitrarily obtained, such as those having Si-H bonds in the molecule. However, it is not economical to add alkoxysilanes and the use of high molecular weight polyorganosiloxanes as in the present invention, or even those containing cured products or fillers therefrom, is not disclosed.

Japanese Patent Laid-Open No. 271416/1993 discloses a pyrolysis method of condensing volatile siloxane produced by applying heat to a vulcanized product of silicone rubber. In this process, it is necessary to heat to a high temperature of 350 ° C. or higher, and only cyclic dialkylsiloxanes are obtained.

Huang et al. Reported a process using diethylamine and methanol in a double solution in Polymer 43 (2002) pp7239-7300 to decompose silicone rubber.

The method disclosed in Korean Patent Publication No. 10-0247162, filed by Japan Tama Chemicals Company, has the disadvantages of adding a low molecular weight alkoxysilane and sodium or tetramethyl ammonium alcoholate to decompose the waste polymer silicon compound and the resulting cost increase. There is no reliable way to recover the charge.

The first problem to be solved by the present invention relates to a method for recovering the low molecular weight silicon compound from the silicon waste using mineral oil as a solvent to maximize the recovery yield, and also recover the filler contained in the silicon waste.

The second problem to be solved by the present invention relates to a method for primary recovery of low molecular weight silicone compounds by cracking silicon waste with strong acids such as sulfuric acid using mineral oil as a solvent and distilling under vacuum atmosphere.

The third problem to be solved by the present invention is to use a mineral oil as a solvent to crack the silicon waste with strong acid such as sulfuric acid, distilled under vacuum atmosphere to recover the low molecular weight silicon compound primarily and to add a strong base such as KOH to the remaining residue in a vacuum atmosphere The second method relates to a method for recovering a low molecular weight silicone compound.

In order to achieve the technical problem to be achieved by the present invention, in the method for recovering the silicon compound from the silicon waste, (a) a mixture of silicon waste and mineral oil is produced by mixing the silicon waste and mineral oil cut or crushed into the reaction vessel by mixing Then heating the mixture; (b) adding a strong acid to the mixture and stirring the mixture; (c) recovering the low molecular weight silicone compound by distilling the low molecular weight silicone compound decomposed while heating the mixture in a vacuum atmosphere, wherein the mineral oil is any one component selected from aromatic, naphthalene and paraffin based Provided is a method for recovering a low molecular silicon compound from a silicon waste, which comprises the above.

The mineral oil preferably has a flash point of 112 ° C to 258 ° C.

The mineral oil has a viscosity of 2.25 cSt. To 43.9 cSt.

It is preferable that the said mineral oil mixed two or more mineral oils from which a flash point and a viscosity differ.

It is preferable that the said mineral oil is 0.1-40 weight part of naphthalene system, 0.2- 8.2 weight part of aromatics, and the remainder are paraffin type with respect to 100 weight part of mineral oils.

It is preferable that the said mineral oil is 0.1-40 weight part of naphthalene system, and the remainder are paraffin type with respect to 100 weight part of mineral oils.

When the silicon waste and the mineral oil is mixed in the step (a) to produce a mixture, the weight ratio of the silicon waste and the mineral oil is preferably 50 to 500 parts by weight based on 100 parts by weight of the silicon waste.

The strong acid is preferably sulfuric acid.

The amount of sulfuric acid is preferably 0.5 to 20 parts by weight based on 100 parts by weight of the silicon waste.

The step (a) is carried out in a vacuum atmosphere of 10mmHg to 100mmHg, at a temperature of 80 to 150 ℃, for 30 minutes to 180 minutes, the step (b) is a normal pressure atmosphere, at a temperature of 80 to 200 ℃, It is carried out for 30 to 120 minutes, the step (c) is preferably carried out for 90 minutes to 360 minutes, at a temperature of 130 to 200 ℃ in a vacuum atmosphere of 10mmHg to 100mmHg.

In order to achieve the technical problem to be achieved by the present invention, a mixture of silicon waste and mineral oil is heated, a strong acid is added and stirred to the heated mixture, the stirred mixture is distilled under a vacuum atmosphere to recover a low molecular silicon compound (D) adding a strong base to the residue and heating the remaining residue of the mixture; And (e) distilling the residue to recover a low molecular weight silicone compound, wherein the mineral oil preferably contains at least one component selected from aromatic, naphthalene and paraffin based.

The mineral oil has a flash point of 112 ° C. to 258 ° C., and the mineral oil has a viscosity of 2.25 cSt. It is preferred that the mineral oil is one kind of mineral oil having the same viscosity as the flash point or a mixture of two or more mineral oils having different flash points and the viscosity.

The mineral oil may be 0.1 to 40 parts by weight of naphthalene, 0.2 to 8.2 parts by weight of aromatic and paraffinic based on 100 parts by weight of mineral oil, or the mineral oil may be 0.1 to 40 parts by weight of naphthalene based on 100 parts by weight of mineral oil. It is preferable that 40 weight part and the remainder are paraffin type.

(F) between the step (d) and the step (e), (f) cooling the residue to 15 ℃ to 45 ℃ and agitated by adding a solvent, and maintaining the stirred residue for a predetermined time; includes (G) filtering the residue to recover a charge; (h) recovering the mineral oil from the filtered residue from which the charges have been recovered; And (i) recovering the solvent from the filtered residue from which the charge is recovered; It is preferable to further recover any one or more of the filler, mineral oil and solvent, further including any one or more of the above.

It is preferable that it is either selected from the aromatic solvent containing any one or more of the alkyl solvent of the said solvent C5-C8, benzene, and toluene.

The strong base is potassium hydroxide (KOH), the content of the potassium hydroxide (KOH) is preferably 1 to 22 parts by weight based on 100 parts by weight of the silicon waste.

The step (d) is carried out for 30 minutes to 180 minutes, at a temperature of 130 to 200 ℃ in the atmospheric pressure, the step (e) at a temperature of 130 to 200 ℃, in a vacuum atmosphere of 10mmHg to 100mmHg, It is preferably carried out for 90 to 360 minutes.

When the process of steps (a) to (e) proceeds, the flash point of the mineral oil is preferably higher than the temperature at which the steps (a) to (e) is carried out, but the process is carried out in a closed space, When the process with the cooling tower is in progress, the flash point of the mineral oil may not be higher than the temperature at which the steps (a) to (e) is carried out.

By carrying out the method of recovering the silicon compound of the present invention, it is possible to maximize the recovery efficiency of the silicon compound from the silicon waste, and also to recover the fillers contained in the silicon waste. In particular, mineral oil is stable during the cracking process of silicon waste using strong acid, and the difference between the low molecular weight silicon compound and the boiling point is high, and thus the distillation efficiency and cost are low.

On the other hand, solvents such as used mineral oil, C5-C8 alkyl solvent, aromatic solvent containing any one or more of benzene and toluene and the like can also be recovered and reused.

In addition, it is possible to protect the environment by reprocessing the discarded silicon waste, the recovered low-molecular silicon compound and recovered filler and the like can be recycled in various industries.

Hereinafter, it demonstrates in detail, referring drawings.

The method for recovering the silicon compound of the present invention consists of a first recovery step and a second recovery step.

A first recovery step will be described with reference to FIG. 1. The first recovery phase consists of three phases.

The first step is to mix silicon waste and mineral oil to form a mixture, and heat the mixture to remove moisture.

The silicon waste is a high-molecular weight waste silicon product, and more specifically, silicon rubber, silicone resin, silicone adhesive, silicone sealant, silicone grease, dielectric coolant of waste transformer, and the like. Naturally, the waste includes other silicon waste than those exemplified. The silicon waste is preferably cut or ground. The smaller the size of cutting or grinding is, the more advantageous it is, but it takes energy and time to reduce the size, so it is better to keep it at an appropriate size. The low molecular weight silicone compound recovered in the present invention is DMC or DMCS, and DMC / DMCS refers to dimethyl cyclosiloxane. Important DMC / DMCS in the present invention are D3, D4, D5, D6, D7, which are respectively D3 (Trimer): hexamethyl cyclotrisiloxane, D4 (Tetramer): octamethyl cyclotetrasiloxane, D5 (Pentamer): decamethyl cyclopentasiloxane, D6 (hexamer) : dodecamethyl cyclohexasiloxane, D7 (heptamer): tetramethly cycloheptasiloxane. Hereinafter, it is called DMC.

Mineral oil is obtained by refining crude oil, and has a structure composed of linear hydrocarbons. Swelling the pulverized silicon waste well (swelling), the separation of the boiling point with the DMC in the future recovery of the silicon waste is easy to be separated, especially because it is not easily decomposed by sulfuric acid, high recovery and reuse. The mineral oil is advantageous the lower the moisture content. BDG, dimethyl carbonate, ethylene glycol monobutyl ether, etc. may be considered instead of mineral oil. However, BDG is decomposed by sulfuric acid, which makes it difficult to separate the produced compound from DMC and reduces reusability. In particular, Dimethyl carbonate, ethylene glycol monobutyl ether, etc. are decomposed during the reaction, can not be recovered and reused after the reaction, there was a problem in low yield.

The content ratio of the silicon waste and the mineral oil is preferably 50 to 500 parts by weight of mineral oil, more preferably 70 to 200 parts by weight, and most preferably 100 to 150 parts by weight based on 100 parts by weight of silicon waste. If the content of the mineral oil is less than 50 parts by weight compared to the content of the silicon waste, there is a problem that the flowability of the mixture is poor, the transferability between processes, the swelling of the silicon waste is not good, the cracking of the silicon waste There is a problem in that stirring becomes difficult after cracking. On the other hand, when the content of the mineral oil exceeds 500 parts by weight compared to the content of the silicon waste, the reaction scale is increased, and the recovery process time and cost of mineral oil and the like increases. The specific ratio of the silicon waste and the mineral oil content ratio was found to be irrelevant. In other words, any kind of silicon waste, when mixed with the mineral oil in the above range showed a good yield.

The mineral oil used in the present invention has a viscosity of 2.25 cSt. To 43.9 cSt. Has a flash point of 112 ° C. to 258 ° C., a pour point of −55 ° C. to −7.5 ° C., and at least one component of an aromatic, naphthalene, and paraffin based components. It is preferable that this is included.

On the other hand, the experimental results showed that the viscosity of mineral oil was 2.25 cSt. To 43.9 cSt. It is preferable that it is a flash point of 112 degreeC-258 degreeC. If the flash point of the mineral oil is too low, the boiling point also tends to be proportionally low, there is a problem in raising the temperature at the time of cracking and distillation, there is a problem to be distilled together with the low molecular DMC, to separate the mineral oil and low molecular DMC again There is a problem that needs to be done. On the other hand, if the flash point of the mineral oil is too high, the viscosity tends to be high, and thus there is a problem that the fluidity of the reactants in the reactor is inferior. If the viscosity of the mineral oil is too low, the boiling point or flash point tends to be low. In this case, a problem arises in raising the temperature during cracking and distillation. On the other hand, if the viscosity of the mineral oil is too high may cause a problem of poor fluidity of the reactants in the reactor.

In addition, the mineral oil is preferably composed of no aromatics, 8.2%, naphthalene-based 0.1 to 40%, the balance is preferably composed of paraffinic. On the other hand, the specific gravity of mineral oil is preferably about 0.769 to 0.883. In addition, it is also possible to mix and use 2 or more types of mineral oil.

In the first step, the water is removed by heating. If the water is not removed, the DMC produced during the reaction is combined with water to extend linearly to polymerize to reduce the recovery yield of the low molecular weight DMC.

The first step is preferably carried out for 30 to 180 minutes at a temperature of 80 to 150 ℃ in a vacuum atmosphere of 10mmHg to 100mmHg. The reason to be carried out in a vacuum atmosphere is that the vacuum helps to remove moisture, and if the degree of vacuum is less than 10 mmHg, it is expensive to maintain a high degree of vacuum, and if the degree of vacuum exceeds 100 mmHg, There is a problem of low efficiency. The heating temperature is important for water removal, but if the temperature is less than 80 ℃ water evaporation efficiency is reduced, if the temperature exceeds 150 ℃ to help the water removal, but maintaining a high temperature compared to the increased water removal efficiency with increasing temperature There is a problem that costs more. The heating time is preferably about 30 minutes to 180 minutes, but a small time is required at high vacuum and high temperature, and a relatively long time is required at low vacuum and low temperature. At this time, if the heating time is less than 30 minutes, there is a high risk that the moisture removal is not sufficient, and if it exceeds 180 minutes, the additional moisture removal effect is insignificant even if heated.

After the first step, the water-free mixture is cooled to 100 ° C. or lower at atmospheric pressure. Atmospheric pressure is preferably atmospheric pressure, and may be about 700 mmHg to about 800 mmHg.

The second step is to add a strong acid to the mixture and to stir. The strong acid is preferably sulfuric acid. Industrial hydrochloric acid (35%) is largely impossible because it contains water, other strong acids such as nitric acid can be used in the practice of the present invention, but there is a problem of low economic efficiency. Sulfuric acid cracks the silicon waste. In the case of cracking after adding sulfuric acid to the mixture, sulfuric acid may be further added. In the present invention, since sulfuric acid plays a role of cracking silicon waste, the use of other strong acids to perform this role is not excluded unless there is a special side effect. The amount of sulfuric acid added is preferably 2 to 15 parts by weight, more preferably 3 to 10 parts by weight, and more preferably 5 to 10 parts by weight based on 100 parts by weight of the silicon waste. If the sulfuric acid content is less than 2 parts by weight, the sulfuric acid content is low, so that cracking of silicon waste is insufficient. If the sulfuric acid content is more than 15 parts by weight, corrosion of the reactor is not increased without increasing the cracking efficiency. It is more likely to happen.

The addition and stirring of sulfuric acid in the second step is carried out at atmospheric pressure, it is preferably carried out for 30 minutes to 120 minutes at a temperature of 130 to 200 ℃. Since there is no recovery of the DMC in the stirring step, it is not necessary to maintain a vacuum, and relatively high temperature is required for the cracking of the high molecular compound to a low molecule, and a sufficient time for the cracking process is required. However, if excessive cracking occurs, the transfer to the recovery step of the DMC in a later step is problematic, so the cracking should be managed at an appropriate level. If the temperature is less than 130 ℃ there is a problem that the cracking is not sufficient at the second stage level, if exceeding 200 ℃ there is a fear that excessive cracking at the second stage level occurs. The heating time requires a little time at high temperatures and a relatively long time at low temperatures. At this time, if the heating time is less than 30 minutes, the risk of not enough cracking is great, and if it exceeds 120 minutes, the possibility of excessive cracking is large. Cracking is important for proper temperature control. Higher temperatures tend to crack the silicon waste, but at the same time cracking produces DMCs, which polymerize to form linear polysiloxanes (resin states). A reversible reaction occurs between the DMC and the linear polysiloxane, and the DMC is distilled off while both reactions are in equilibrium. At this time, when the temperature is above a certain temperature, the production rate of the linear polysiloxane is faster than the production of DMC, resulting in a decrease in the recovery efficiency of the DMC.

There is no standardized method for measuring the degree of cracking, but if the appearance of the used silicon waste does not appear, it can be understood that cracking proceeds normally. The degree of cracking can also be determined by the color (dark gray or black) of the compound in the reactor. At this time, the factors influencing cracking are the type and size of silicon waste used, the amount of strong acid such as sulfuric acid, the cracking temperature, the type of mineral oil used, and the like.

The third step is to recover the low molecular weight silicone compound by first distilling the decomposed low molecular weight silicone compound while heating the mixture. Preferably, the first recovered silicon compound is recovered by distillation, and D3, D4, D5, D6, and D7 are recovered. Almost no compound above D8 is produced. The content ratio of silicon is different for each type of silicon waste, and the higher the content of silicon, the higher the recovery rate of DMC. In general, the quality standard of DMC is the content of D4, and it is very difficult to control the content ratio of D3 to D7 as a reaction variable, but the separated DMC may increase the content of D4 in the final product by using a fractional distillation column.

The third step is preferably carried out in a vacuum atmosphere of 10mmHg to 100mmHg, at a temperature of 130 to 200 ℃, 90 minutes to 360 minutes. The third step should be carried out in a vacuum atmosphere, because the boiling point of the low molecular weight silicon compound recovered by the primary distillation method is high, and the atmospheric pressure requires a significantly higher temperature and process time than the vacuum state. If the degree of vacuum is less than 10mmHg high vacuum, it is expensive to maintain a high degree of vacuum, and if the degree of vacuum is less than 100mmHg low vacuum, the DMC is not distilled or the distillation efficiency drops rapidly. . The heating temperature is lower than the recovery temperature of the low molecular weight silicone compound when the temperature is less than 130 ℃, the temperature above 200 ℃ is helpful for the recovery of the low molecular weight silicone compound, but compared to the recovery rate of the low molecular weight silicone compound increases with increasing temperature There is a problem that costs more to maintain a high temperature. The heating time is preferably about 90 minutes to 360 minutes, a small time is required at high vacuum and high temperature, and a relatively long time is required at low vacuum and low temperature. At this time, if the heating time is less than 90 minutes, there is a high risk that the recovery rate of the low molecular weight silicone compound drops, and if it exceeds 360 minutes, the additional recovery efficiency does not increase much even when heated.

On the other hand, when distilling in a vacuum atmosphere, the vacuum should not be suspended at a time, but very slowly. If the vacuum is strongly applied at a time, the reactions may rise to the distillation tube and block the distillation tube, and the distillation tank may bump. At this time, bubbles may occur depending on the mineral oil, and the generation of bubbles does not have much relation with the control of the reaction. On the other hand, when distilling in a vacuum atmosphere, the entire reactant in the reactor swells. At this moment, if the vacuum is momentarily strongly applied, the swollen liquid reactant is fixed to the reactor wall as resin-type siloxane. Not only are the materials required to participate in the secondary reaction reduced, but the cleanliness inside the reactor is not good and there are problems in reactor operation.

Next, the secondary recovery step will be described with reference to FIG. 2. The secondary recovery step is largely composed of two steps.

The first step of the second recovery step is to add a strong base to the residue after the first recovery step and to heat it. The strong base is preferably KOH. The strong base, in particular KOH, lowers the molecular weight of the linear silicone oil produced after the reaction with the cyclic compound. In addition to KOH, other strong bases such as NaOH may also be used, but the reaction time is long, so there is a problem of low economic feasibility, and the weak base has a problem of extremely low recovery yield. The content of the potassium hydroxide (KOH) is preferably 1 to 22 parts by weight, more preferably 3 to 15 parts by weight, and more preferably 5 to 8 parts by weight based on 100 parts by weight of the silicon waste. If the content of KOH is less than 1 part by weight, there is a problem that the low molecular weight of the silicone oil of the residue is low because the content of the KOH is less, and when the content of the KOH exceeds 22 parts by weight, the excess KOH is further lowered There is a problem that does not occur.

It is preferable that the first step of the second recovery step is carried out for 30 minutes to 180 minutes at a temperature of 130 to 200 ℃ in an atmospheric pressure atmosphere. In the first stage of the secondary recovery step, there is no secondary recovery of the DMC, so there is no need to maintain a vacuum. The linear silicone oil requires a relatively high temperature in order for the low molecular weight to proceed with the cyclic compound, and a sufficient time is required for the low molecular weight. If the temperature is less than 130 ℃ there is a problem that the low molecular weight is not enough, if the temperature exceeds 200 ℃ there is a problem in controlling the transfer time to the secondary recovery in the next step. The heating time requires a little time at high temperatures and a relatively long time at low temperatures. At this time, if the heating time is less than 30 minutes, the risk of not enough cracking is large, and if it exceeds 180 minutes, the possibility of excessive cracking is large.

Next, a second step in the second recovery step will be described.

After cooling the residue from the first step in the second recovery step to 15 ℃ to 45 ℃, stirring by adding an alkyl solvent of C5-C8 and an aromatic solvent such as benzene, toluene and stirred, the stirred residue is a predetermined time If maintained for a while, the residue becomes a slurry. 1) Filling recovery, 2) Mineral oil recovery, 3) Solvent recovery, 4) Low molecular silicon compound secondary recovery can be performed from the slurry residue. The C5-C8 alkyl solvent and aromatic solvents such as benzene and toluene facilitate the washing of DMC remaining in the reactor and separation of solid fillers (various fillers contained in silicon waste, etc.). The use amount of the C5-C8 alkyl solvent and aromatic solvent such as benzene and toluene is preferably 20 to 40 parts by weight based on 100 parts by weight of silicon waste. In order to recover the packing material, the slurry residue is filtered using a filtering device such as a bag filter to recover an inorganic packing such as silica. Mineral oil is recovered from the filtrate, and C5-C8 alkyl solvent and aromatic solvent such as benzene and toluene are recovered. The distillation method for the recovery of the C5-C8 alkyl solvent and aromatic solvents such as benzene and toluene can be carried out under normal pressure or vacuum, but is preferably carried out in consideration of economic aspects.

The key to the second stage of the secondary recovery step is to recover the low molecular weight silicone compound secondary from the residue. Recovering the low molecular weight silicone compound in the secondary recovery step is preferably carried out for 90 minutes to 360 minutes at a temperature of 130 to 200 ℃ in a vacuum atmosphere of 10mmHg to 100mmHg. The reason why the process of recovering the low molecular weight silicon compound of the secondary recovery step should be performed in a vacuum atmosphere is that the boiling point of the low molecular weight silicon compound recovered by the secondary distillation method is high, and in the case of normal pressure, the temperature and the process time are considerably higher than those of the vacuum state. It is necessary. If the degree of vacuum is less than 10mmHg high vacuum, it is expensive to maintain a high degree of vacuum, and if the degree of vacuum is less than 100mmHg low vacuum, DMC does not distill, or distillation efficiency drops sharply. have. The heating temperature is lower than the recovery temperature of the low molecular weight silicone compound when the temperature is less than 130 ℃, the temperature above 200 ℃ is helpful for the recovery of the low molecular weight silicone compound, but compared to the recovery rate of the low molecular weight silicone compound increases with increasing temperature There is a problem that costs more to maintain a high temperature. The heating time is preferably about 90 minutes to 360 minutes, a small time is required at high vacuum and high temperature, and a relatively long time is required at low vacuum and low temperature. At this time, if the heating time is less than 90 minutes, there is a high risk that the recovery rate of the low molecular weight silicone compound is lowered, and if it exceeds 360 minutes, the additional recovery efficiency does not increase much even when heated.

The residue in the form of a slurry is filtered above, and a packing material is collect | recovered first, and the C5-C8 alkyl solvent and aromatic solvent, such as benzene and toluene, are collect | recovered from a filtrate. Secondary recovery of the low molecular weight silicon compound is recovered by distillation and the remaining mineral oil is then drained from the reactor and reused immediately. This reusability is one of the advantages of mineral oil.

As the reaction reaches equilibrium in the DMC recovery process, no further reaction proceeds. Therefore, the DMC must be distilled out and removed in the reactor so that the low molecular weight reaction (the linear silicone compound is more polymeric than the cyclic silicone compound). .) Continues. On the other hand, when the DMC is distilled off, since the polymer-type linear silicone compound is further left, the viscosity becomes high. Therefore, a solvent is used at this time, in which case the DMC should not be distilled together at the temperature at which the DMC is distilled.

When the process of each step is in progress, the boiling point of the mineral oil is preferably higher than the temperature at which each step is carried out. However, when the process is carried out in an enclosed space, or when the process with the cooling tower is in progress, the boiling point of the mineral oil may not be higher than the temperature at which each step is carried out. This is because, in a closed space, even if the mineral oil is boiled, the space is sealed, so there is no loss of mineral oil. In particular, when there is a cooling tower, the boiled mineral oil can be condensed by the cooling tower again and recovered into the reactor.

3 is a schematic diagram of a low molecular silicon compound recovery apparatus of the present invention.

As a first step to recover the low molecular weight silicone compound, the mineral oil was metered from the storage tank 100 and introduced into the mixer reactor 101, and the waste polymer silicon products cut and crushed to a small size were added to the mixer reactor 101. And heat to remove water with a water distillation tank 102 at a light pressure. In the second step, the vacuum is removed and cooled to 100 ° C. or lower at normal pressure. Then, a strong acid is introduced into the mixer reactor 101, and the mixture is rapidly stirred under a weak vacuum. In the third step, the mixture is slowly heated to 170 ° C. at atmospheric pressure for 2 hours and 30 minutes, and the decomposed low molecular silicon compound is distilled from the reaction tank 103 to be recovered and stored in the storage tank 109.

In the first stage of the secondary recovery step, KOH is added to the reactor 103 in which most of the low molecular weight silicone compounds are distilled and recovered, and heated to 170 ° C. for 2 hours. In the second step of the second recovery step, the mixture is cooled to room temperature, an alkyl solvent of C5-C8 and an aromatic solvent such as benzene and toluene are added, stirred for 30 minutes, and left for 2 hours. The slurry mixture is filtered through a bag filter 104 to recover inorganic fillers such as silica, the filtrate is cooled, and an alkyl solvent of C5-C8, an aromatic solvent such as benzene and toluene, and a distillation tank 107. Then, the surplus low molecular weight silicone compound is distilled from the distillation tank 108 to be recovered and stored in the storage tank 105 and the solvent storage tank 106.

Next, it will be described once again with reference to the embodiment of the present invention.

[Test Example 1]

In the first step, 200g of small-sized cut and pulverized waste polymer silicon was added to a three neck 1 liter reactor equipped with a simple distillation apparatus, 300g of mineral oil was added, and heated to 125 ° C and maintained at 60mmHg pressure for 1 hour. Removed. The mineral oil used had physical properties of specific gravity 0.8834, viscosity 29.97, flash point 214 ° C, 0.6 parts by weight of aromatic, 34.0 parts by weight of naphthalene, and 65.4 parts by weight of paraffin.

In the second step, the vacuum was removed in the next step, cooled to 100 ° C. or less at normal pressure, and then 12 g of sulfuric acid was added and stirred for 1 hour. Again the mixture was stirred rapidly under mild vacuum. Be careful of bumping the contents. In a third step, the mixture was slowly heated to 170 ° C. under 60 mmHg pressure and maintained for 2 hours 30 minutes to distill off the degraded low molecular weight silicone compound. In the first step of the second recovery step, 11 g of KOH was added to the remaining solution in the reactor, and heated to 170 ° C. at atmospheric pressure, and maintained for 2 hours. After cooling to room temperature, the alkyl solvent of C5-C8 and the direction of benzene, toluene, etc. Foot solvent was added and stirred for 30 minutes and left for 2 hours. In the second step of the second recovery step, the slurry mixture is filtered to recover inorganic fillers such as silica, and the filtrate is distilled in a second way by heating to 170 ° C. under 60 mmHg pressure and maintaining for 2 hours and 30 minutes. The low molecular weight silicone compound was recovered.

The first recovered silicon compound was 77 g, and the second recovered silicon compound was 22 g. As a result, the total amount of recovered silicon was 99g, corresponding to 49.5% of the weight of used silicon waste, and 93g of recovered and reusable fillers, corresponding to 46.5% of the weight of silicon waste. The recovered silicon monomers were analyzed by GC at a temperature of 20 ° C./min, and analyzed from 100 ° C. to 320 ° C., and the components were identified using commercially available D3, D4, D5, D6, and D7 as standard materials. GC used model name 5890 manufactured by Hewlett Packard (HP).

[Test Examples 2 to 38]

Test Examples 2 to 40 were carried out by adjusting any one of Test Example 1, input elements, and process variables, and the characteristics and amount of silicon recovered compared to Test Example 1 are summarized in Table 1.

Test Example Difference from Test Example 1 Total recovered silicon Yield Remarks One Same as Test Example 1 99 g 49.5% 2 0.5g sulfuric acid 11 g 5.5% 3 Sulfuric acid 1g 25 g 12.5% 4 20g sulfuric acid 96 g 48% 5 30g sulfuric acid 98 g 49% 6 KOH 1g 80 g (= 77 + 3) 40% 7 KOH 2g 83g (= 77 + 6) 41.5% 8 KOH 10g 95 g (= 77 + 18) 47.5% 9 KOH 20g 98 g (= 77 + 21) 49% 10 KOH 40g 98 g (= 77 + 21) 49% 11 50 g mineral oil 82 g 41% 12 100 g of mineral oil 98 g 49% 13 Mineral oil 300g 99 g 49.5% 14 Mineral oil 500 g 99 g 49.5 15 Mineral oil 1000g 96g 48% 16 Atmospheric pressure in the water removal stage 32 g 16% 17 Atmospheric pressure treatment in the first recovery stage 88 g 44% 18 Atmospheric pressure treatment in the second recovery stage 77g (= 77 + 0) 38.5% 19 Moisture Removal Step Temperature 60 ℃ 20 g 10% 20 Water removal step temperature 200 ℃ 98 g 49.5% 21 Stirring step temperature 100 ℃ after adding sulfuric acid 85 g 42.5% 22 Agitation step temperature 250 ℃ after adding sulfuric acid 97 g 48.5% 23 1st recovery stage temperature 100 ℃ 67 g 33.5% 24 1st recovery stage temperature 250 ℃ 96g 48% 25 Stirring step temperature 100 ℃ after adding KOH 89 g (= 77 + 12) 44.5% 26 Stirring step 250 ℃ after adding KOH 97g (= 77 + 20) 48.5% 27 2nd recovery step temperature 100 ℃ 81 g (= 77 + 4) 40.5% 28 Secondary recovery stage temperature 250 ° C 99 g 49.5% 29 Dehydration step run time 10 minutes 30 g 15% 30 360 min for Dehydration Steps 98 g 49% 31 10 minutes of stirring step after adding sulfuric acid 60 g 30% 32 360 minutes of stirring step after adding sulfuric acid 96g 48% 33 45 minutes of first recovery phase 80 g 40% 34 720 min first payback time 97 g 48.5% 35 10 minutes of stirring step after adding KOH 85 g (= 77 + 8) 42.5% 36 240 minutes after the addition of KOH 99 g 49.5% 37 45 min of 2nd recovery phase run time 89 g (= 77 + 12) 44.5% 38 720 min recovery time 98 g 49.5%

(The figures in parentheses are for reference only to show how the final obtained silicon compound can be divided into primary and secondary recovery.)

Test Examples 2 to 5 relate to the content of sulfuric acid. As in Test Example 2, when the sulfuric acid content was 0.25 parts by weight relative to 100 parts by weight of silicon waste (the silicon waste used in the experiment was 200 g), the recovery was only 5.5%. This yield is of little economic value. If the sulfuric acid is 0.5 parts by weight, the yield was about 12.5%. In the case of 10 parts by weight of sulfuric acid shows a recovery of 48%, which is a recovery in the range not significantly different from the estimated error range when compared with Test Example 1. At this time, even if the content of sulfuric acid was increased by 50% more than in Test Example 3 as in Test Example 4, the improvement in yield remained at 1%. Therefore, there is no problem even if sulfuric acid is used in excess of 10 parts by weight, but the increase in efficiency compared to the cost seems to be insignificant.

Test Examples 6 to 10 relate to the content of potassium hydroxide. As in Example 6, when the content of potassium hydroxide was 0.5 parts by weight based on 100 parts by weight of silicon waste, the recovery rate was extremely low. Of the 80g recovered, 77g was obtained from the first recovery, so only 3g was obtained from the second recovery. There is little economy. When 1 part by weight of potassium hydroxide was recovered 6g, which was about 27.2% compared to Test Example 1. In the case of 5 parts by weight of potassium hydroxide as in Test Example 8, 18g was recovered in the second recovery, and in the case of 10 parts by weight as in Test Example 9, approximately 21g in the second recovery was recovered in close proximity to Test Example 1. On the other hand, even when the potassium hydroxide content was 20 parts by weight as in Test Example 10, there was almost no improvement in yield compared to Test Example 1. Test Example 9 and Test Example 10 were yields within Test Example 1 and the expected error range.

Test Examples 11 to 15 are related to the content of mineral oil. As in Test Example 11, when the content of mineral oil was 25 parts by weight based on 100 parts by weight of silicon waste, there was a relatively low recovery rate of 41%. This yield is economical, but mineral oil is recovered, so there will be no need to add too little at the expense of efficiency. In Test Example 12 to Test Example 15, the yield was not significantly different depending on the content of mineral oil. Therefore, injecting more than 500 parts by weight of mineral oil has a problem that the reaction scale is too large compared to the yield.

Test Examples 16-18 are related to vacuum processing among the process variables. Test Example 16 was subjected to atmospheric pressure in the water removal step, yield was 16%, this degree is quite economical. In the case of atmospheric pressure treatment, water removal was not good and yield was low. In the case of Test Example 17, when the atmospheric pressure treatment in the first recovery step, almost no recovery in the first recovery step, 88g was recovered in the second recovery step. It seems that the resulting low molecular weight silicon, which was not recovered in the first recovery step, was recovered in distillation in the second. As in the case of Test Example 18, there was almost no low molecular weight silicone compound recovered in the secondary distillation process when the process was performed at atmospheric pressure without vacuum treatment.

Test Examples 19-28 relate to temperature treatment among process variables. When the temperature in the water removal step as shown in Test Example 19 to a low temperature of about 60 ℃, the water removal is not complete, the yield was quite low as 10%. On the other hand, even if excessively high, such as 200 ℃ as in Test Example 20, almost no additional yield improvement. When the temperature of the stirring step after the addition of sulfuric acid to the low temperature as 100 ℃ as in Test Example 21, the cracking is not complete, the yield was relatively low as 42.5%, considering the energy cost of raising the temperature, yield compared to the cost It has been shown that it is more desirable to choose the direction in which to raise. On the other hand, even in the case of 250 ℃ as in Test Example 24, there was no additional yield improvement, there was a problem that only energy consumption increases. When the temperature of the first recovery step is relatively low, such as 100 ° C. as in Test Example 23, distillation is not smooth and the yield is 33.5%, which is about 32 g less than that in Test Example 1. On the other hand, even if the temperature of the 1st recovery step was raised to 250 degreeC like the test example 24, only the yield within the error range came out. As in Test Example 25, when the temperature of the stirring step was kept at 100 ° C. at low temperature after the addition of KOH, 10g was recovered less than in Test Example 1. On the other hand, even if maintained at an excessively high at 250 ℃ as in Test Example 26, the yield did not change significantly within the error range. When the temperature of the secondary recovery step was 100 ° C. as in Test Example 27, only 4 g which was too small as in Test Example 1 was recovered in the secondary recovery step. On the other hand, even if the temperature of the secondary recovery step was as high as 250 ° C as in Test Example 28, there was almost no difference in recovery.

Test Examples 29 to 38 summarize the recovery results of low molecular weight silicon while adjusting the time variable among the process variables. When the execution time of the water removal step is excessively short as 10 minutes as in Test Example 29, the water removal is not efficiently performed, the recovery rate is drastically decreased. As in Test Example 30, even when the water removal time was sufficiently large, such as 360 minutes, the yield improvement did not change. As shown in Test Example 31, when the execution time of the stirring step after adding sulfuric acid was short as 10 minutes, the yield was relatively very low. This suggests that even if the stirring time is kept long at an appropriate level, it is not expensive to maintain the process, and therefore, it is preferable to stir sufficiently. On the other hand, even if taking a sufficient amount of stirring step performance time, such as 360 minutes, as in Test Example 32, there was little change in yield improvement. As in Test Example 33, when the execution time of the first recovery step was taken as short as 45 minutes, there was a problem that the recovery was considerably less than in Test Example 1. As in Test Example 34, even if the first recovery step execution time was sufficient as about 720 minutes, there was little variation in the yield within the predictable error range. As in Test Example 35, if the execution time of the stirring step after adding KOH was shortened to about 10 minutes, there was a problem that the recovery was considerably less in the secondary recovery step than in Test Example 1. As in Test Example 36, even if the first recovery step execution time was sufficient as about 240 minutes, there was almost no change in yield within the predictable error range. As in Test Example 37, when the execution time of the second recovery step was shortened to about 45 minutes, there was a problem that the recovery was considerably less than in Test Example 1. Therefore, it would be an undesirable choice to make the second recovery time too short. As in Test Example 38, even if the execution time of the second recovery step was sufficient as about 720 minutes, there was almost no change in yield within the predictable error range.

As can be seen from the test example at all times, when the content of sulfuric acid is too small, the yield was significantly lowered, and when the KOH content was too small, there was a problem that the yield was significantly lowered. On the other hand, even when the sulfuric acid content is excessive or the KOH content is excessive, there was little effect on the increase in yield. On the other hand, when the atmospheric pressure treatment was performed at the stage where vacuum treatment is preferred in the pressure variable, the process in which water removal was not effective also had a low yield, but the atmospheric pressure treatment in the first and second recovery stages significantly reduced the recovery rate. This is thought to be related to the boiling point of the recovered low molecular weight silicone compound. And, when the temperature of the stirring step, the temperature of the recovery step is lower than the reference, the yield was significantly reduced, even if the temperature is excessively high in each step, there was no significant difference in the yield. On the other hand, if the time is excessively lower than the reference time, there was an effect on the yield, even if the excessively long time did not significantly increase the yield.

[Experimental Example by Type of Mineral Oil]

Subsequently, the experiment was carried out while replacing mineral oils with different components. The experimental method was as follows. Into a three neck 1 liter reactor equipped with a simple distillation apparatus, 100 g of cut and pulverized waste polymer silicon was put into a small size, and 360 g of mineral oil 1 was added thereto, heated to 125 ° C., and maintained at 60 ° C. for 1 hour to remove moisture. . The vacuum was removed in the next step, cooled to 100 ° C. or below at normal pressure, and then 10 g of sulfuric acid was added and stirred for 1 hour. Again the mixture was stirred rapidly under mild vacuum. At this time, care should be taken of the bumping of the contents. The mixture was slowly heated to 150 ° C. for 2 hours and 30 minutes to distill off the degraded low molecular weight silicone compound. This first recovered low molecular weight silicone compound was 38.5g and confirmed by GC. For secondary recovery of the low molecular weight silicone compound, 22 g of KOH was added to the remaining solution in the reactor, heated to 160 ° C., maintained for 2 hours, cooled to room temperature, added with nucleic acid, stirred for 30 minutes, and left for 2 hours. The slurry mixture was filtered to recover inorganic fillers such as silica, and the filtrate was distilled again to recover 11 g of a surplus low molecular weight silicone compound. As a result, the total amount of recovered silicon was 49.5g, which corresponds to 49.5% of the weight of used silicon waste, and the amount of recovered and reusable filler was 46.5g, which equals 46.5% of the weight of silicon waste. do. The waste polymer silicon used in this experiment was 51% volatile and 49% remaining as a result of TGA analysis. In the same way as the company's information, it reconfirmed that 51% of silicon raw materials except fillers were used. The recovered low molecular weight silicone compound was analyzed by gas chromatography (device name) to increase the temperature to 20 ℃ / min and analyzed from 100 ℃ to 320 ℃. Using commercially available D3, D4, D5, D6, and D7 as standard materials The ingredients were identified.

The same experiment was carried out by replacing mineral oils with different physical properties in the same way as above, and summarized the results.

Table 2 below relates to the physical property values of each mineral oil used in the experiment and the amount of the recovered low molecular silicon compound after using the mineral oil. (In this experiment, 100g of silicon waste was covered.)

Mineral oil number Specific gravity (g / ml) Viscosity (cSt) Flash point (℃) pour point (℃) Ingredients (A, N, P) Cracking degree Foam during vacuum DMC Recovery Primary Secondary Total quantity Mineral oil 1 0.88 29.97 214 -15 0.6,34.0,65.4 △ × 38.5 g 11 g 49.5 g Mineral oil 2 0.83 19.62 228 -20 0.2,17.7,82.1 △ △ 41 6 47 Mineral oil 3 0.84 28.72 232 -17.5 0.3,17.2,82.5 △ ○ 39 7 46 Mineral oil 4 0.87 8.196 158 -40 1.6,39.4,59.0 ○ △ 37 8 45 Mineral oil 5 0.83 13.42 202 -27.5 0.1,0.2,99.7 ○ △ 42 4 46 Mineral oil 6 0.83 8.841 152 -35 1.9,29.3,68.8 ○ × 40 One 41 Mineral oil 7 0.83 10.91 158 -20 0,33.1,66.9 ○ △ 44 6 50 Mineral oil 8 0.87 10.88 158 -20 8.2,38.3,53.5 ○ ○ 45 6 51 Mineral oil 9 0.76 2.25 112 7.5 0,0.1,99.9 △ ○ 46 3 49 Mineral oil 10 0.85 5.28 141 -28 0,28.5,71.5 △ × 22 0 22 Mineral oil 11 0.75 1.54 76 -10 0.12,0.1,99.78 × × 0 0 0 Mineral oil12 0.78 1.11 52.5 -55 0.03,070.0 × × 0 0 0 Mineral oil13 0.87 32 220 -15   0,0.1,99.9 △ ○ 45 4 49  Mineral oil14 0.84 43.89 258 -15 0.2,20.9,78.9 △ ○ 45 6 51

Note) Use 100g of silicon scrap. Component A is aromatic, N is naphthalene and P is paraffin. 은 is good, △ is normal, and 는 is not good in the degree of cracking and foaming under vacuum.

In the above experiment, it was found that mineral oils 1 to 9 and mineral oil 13 showed good silicon recovery.

In the case of mineral oil 1 to mineral oil 3, the first recovery rate was slightly lower due to the presence of a small amount of scrap without primary cracking. In the case of severe foaming during vacuum distillation, resin-type compounds adhered to the reactor wall, and thus, the first recovery rate tended to be lowered because they could not participate in the cracking reaction.

Foaming occurred quite often with mineral oil 6, but the recovery was good. The reason why mineral oil 7, 8 is different from mineral oil 10 is that foaming occurs during the first vacuum distillation, but after a certain time, foaming does not occur. Thus, the recovery rate is good.

In the case of mineral oil 10, foaming continued around 110 degrees during the first vacuum distillation, and thus it could no longer be heated up and distilled. 22 g is the amount vacuum-distilled to 110 degree | times. Thereafter, even in the subsequent secondary reaction, the same morphology was not able to carry out vacuum distillation. However, it was possible to recover the low molecular weight silicon compound of about 22g, and even higher recovery rates could be seen if bubble formation was prevented.

In the case of mineral oils 11 and 12, the cracking rate was very slow, but the recovery rate was elsewhere. Since the experiment did not perform fractional distillation through a distillation column, the difference in boiling point between DMC and mineral oil was not large during vacuum distillation. Thus, the distilled mixture was mixed with mineral oil and DMC. That is, in the case of mineral oils 11 and 12, there is a problem in that a fractional distillation is performed by setting up a distillation column, thereby increasing the silicon recovery cost.

It can be utilized in the silicon waste regeneration industry of the present invention, by implementing the method for recovering the silicon waste silicon compound of the present invention, it is possible to maximize the recovery efficiency of the silicon compound from the silicon waste, and also to the filler contained in the silicon waste It can be recovered.

On the other hand, the low molecular weight silicone compound can be recovered again with respect to the residue remaining after recovering the low molecular weight silicone compound primarily.

In addition, it is possible to protect the environment by reprocessing discarded silicon waste, which may be used in the environmental industry. On the other hand, the recovered low-molecular silicon compound and the recovered filler and the like can be recycled in a variety of industries, the industrial applicability of the present invention is various.

1 is a flow chart of a method for primary recovery of low molecular weight silicon compounds from waste silicon products in accordance with the present invention.

2 is a flow chart of a method for secondary recovery of low molecular weight silicone compounds from waste silicon products in accordance with the present invention.

3 is a view showing the configuration and process of a system for recovering a low molecular weight silicon compound from waste silicon products according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: mineral oil reservoir

101: Mixer reactor with mineral oil, silicon waste and sulfuric acid

102: water distillation tank

103: low molecular weight silicon compound recovery reactor

104: Bag filter

105: DMC reservoir

106: Alkyl solvent of solvent C5-C8 and aromatic solvent storage tank, such as benzene and toluene

107: Alkyl solvent of solvent C5-C8, aromatic solvent such as benzene, toluene, silicon distillation tank

108: silicone compound distillation tank

109: silicone reservoir

Claims (17)

In the method for recovering the silicon compound from the silicon waste, (a) mixing the cut or crushed silicon waste and mineral oil into a reactor to produce a mixture of silicon waste and mineral oil, and then heating the mixture; (b) adding a strong acid to the mixture and stirring the mixture; (c) recovering the low molecular weight silicone compound by distilling the decomposed low molecular weight silicone compound under vacuum atmosphere while heating the mixture; The mineral oil is one containing at least one component selected from aromatic, naphthalene and paraffin-based, The low molecular weight silicone compounds include hexamethyl cyclotrisiloxane, octamethyl cyclotetrasiloxane, decamethyl cyclopentasiloxane, dodecamethyl cyclohexasiloxane, and tetramethyl cycloheptasiloxane. A method for recovering low molecular weight silicon compounds from silicon waste, characterized in that at least one of siloxane (tetramethly cycloheptasiloxane). The method of claim 1, The mineral oil has a flash point of 112 ℃ to 258 ℃ low molecular weight silicon compound recovery method from the silicon waste, characterized in that. The method of claim 1, The mineral oil has a viscosity of 2.25 cSt. To 43.9 cSt. Low molecular weight silicon compound recovery method from silicon waste. The method of claim 1, The mineral oil is a low molecular silicon compound recovery method from the silicon waste, characterized in that a mixture of two or more mineral oils having different flash point and viscosity. The method of claim 1, Said mineral oil is 0.1-40 weight part of naphthalene system, 0.2- 8.2 weight part of aromatics, and the remainder are paraffin type with respect to 100 weight part of mineral oil, The low molecular silicon compound recovery method from the silicon waste characterized by the above-mentioned. The method of claim 1, Said mineral oil is 0.1-40 weight part of naphthalene system, and the remainder are paraffin type with respect to 100 weight part of mineral oils, The low molecular weight silicone compound recovery method from the silicon waste characterized by the above-mentioned. The method of claim 1, When the silicon waste and the mineral oil is mixed in the step (a) to produce a mixture, the weight ratio of the silicon waste and the mineral oil is 50 to 500 parts by weight of mineral oil based on 100 parts by weight of silicon waste. A process for recovering low molecular weight silicone compounds from the process. The method of claim 1, And said strong acid is sulfuric acid. The method of claim 8, The sulfuric acid content is 2 to 15 parts by weight based on 100 parts by weight of the silicon waste, characterized in that the low molecular silicon compound recovery from the silicon waste. The method of claim 1, The step (a) is carried out in a vacuum atmosphere of 10mmHg to 100mmHg, at a temperature of 80 to 150 ℃, 30 minutes to 180 minutes, Step (b) is to be carried out for 30 minutes to 120 minutes at a temperature of 130 to 200 ℃ in an atmospheric pressure atmosphere, The step (c) is a low molecular silicon compound recovery method from the silicon waste, characterized in that carried out in a vacuum atmosphere of 10mmHg to 100mmHg, at a temperature of 130 to 200 ℃ for 90 minutes to 360 minutes. For the mixture of silicon waste and mineral oil, the strong acid is added and stirred to the heated mixture, the stirred mixture is distilled under vacuum atmosphere to recover the low molecular weight silicone compound, (d) adding a strong base to the residue and heating it; And (e) distilling the residue to recover a low molecular weight silicone compound; The mineral oil is one containing at least one component selected from aromatic, naphthalene and paraffin series, The low molecular weight silicone compounds include hexamethyl cyclotrisiloxane, octamethyl cyclotetrasiloxane, decamethyl cyclopentasiloxane, dodecamethyl cyclohexasiloxane, and tetramethyl cycloheptasiloxane. A method for recovering low molecular weight silicon compounds from silicon waste, characterized in that at least one of siloxane (tetramethly cycloheptasiloxane). The method of claim 11, The mineral oil has a flash point of 112 ℃ to 258 ℃, The mineral oil has a viscosity of 2.25 cSt. To 43.89 cSt. The mineral oil is one kind of mineral oil having the same viscosity as the flash point, or a mixture of two or more mineral oils having the different flash point and viscosity, wherein the low molecular weight silicone compound is recovered from the silicon waste. The method of claim 11, The mineral oil is one of 0.1 to 40 parts by weight of naphthalene, 0.2 to 8.2 parts by weight of aromatics and the remainder of the paraffinic based on 100 parts by weight of mineral oil, Said mineral oil is 0.1-40 weight part of naphthalene system, and the remainder are paraffin type with respect to 100 weight part of mineral oils, The low molecular weight silicone compound recovery method from the silicon waste characterized by the above-mentioned. The method of claim 11, Between step (d) and step (e), (f) cooling the residue to 15 ° C. to 45 ° C., adding a solvent and stirring the mixture, and maintaining the stirred residue for a predetermined time; (g) filtering the residue to recover the charge; (h) recovering the mineral oil from the filtered residue from which the charges have been recovered; And (i) recovering the solvent from the filtered residue from which the charge is recovered; A method for recovering low molecular weight silicon compounds from silicon waste, further comprising any one or more of which further recover any one or more of filler, mineral oil and solvent. The method of claim 14, A low molecular weight silicone compound recovery method from a silicon waste, characterized in that any one selected from the aromatic solvent containing any one or more of the alkyl solvent of the solvent C5-C8, benzene and toluene. The method of claim 11, The strong base is potassium hydroxide (KOH), The content of the potassium hydroxide (KOH) is 1 to 22 parts by weight based on 100 parts by weight of the silicon waste, the low molecular weight silicon compound recovery method from the silicon waste. The method of claim 13, The step (d) is to be carried out for 30 minutes to 180 minutes at a temperature of 130 to 200 ℃ in an atmospheric pressure atmosphere, The step (e) is a low molecular weight silicon compound recovery method for recovering from silicon waste, characterized in that carried out for 90 minutes to 360 minutes, at a temperature of 130 to 200 ℃ in a vacuum atmosphere of 10mmHg to 100mmHg.

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