CN116355008A - A kind of treatment process of recycling silicone rubber - Google Patents

Abstract

The invention relates to a treatment process for recycling silicon rubber, and belongs to the technical field of silicon rubber. The invention provides a treatment process for recycling silicon rubber, which realizes effective recycling of waste silicon rubber by a cracking process taking methanol, diethylamine and hexane as filler recycling agents, tetramethylammonium hydroxide as a catalyst and n-octadecanol as a solvent and a filler recycling method; the invention uses the solvent cracking process to treat the waste silicone rubber, reduces the carbonization probability of the siloxane chain units, and is beneficial to improving the generation rate of cyclosiloxane to a certain extent; the invention uses the tetramethyl ammonium hydroxide as the catalyst, and the tetramethyl ammonium hydroxide as the catalyst overcomes the problem that KOH catalyst remains in dimethyl siloxane so as to not meet the production requirement of high-quality silicon rubber, improves the yield of the ring body, and effectively separates the filler; after the polydimethylsiloxane is cracked to reach an equilibrium stage, buffer solution potassium dihydrogen phosphate is added to promote the polydimethylsiloxane to form a ring structure.

Description

A kind of treatment process of recycling silicone rubber

technical field

The invention belongs to the technical field of silicone rubber, and in particular relates to a treatment process for recycling silicone rubber.

Background technique

With the development of industrial production, transportation, urban construction and the increase of population density, the problems of noise pollution, air pollution, water pollution and solid waste discharge have become increasingly serious, and have been listed as the four major pollutions in the world. Silicone rubber is a synthetic rubber with silicon-oxygen bonds as the main chain. It has properties such as high and low temperature resistance, radiation resistance, high pressure resistance, physiological inertia, ozone aging resistance, weather resistance, and high air permeability. Exhibits excellent chemical inertness. The production and consumption of silicone rubber have experienced rapid growth in recent years. In 2013, the consumption of heat vulcanized silicone rubber in my country has reached 328kt, and the average annual growth rate is 7%-8%. What follows is that the amount of waste silicone rubber raw rubber produced in production, silicone rubber waste and scraps formed in vulcanization molding processing, and waste silicone rubber products formed in the application process has increased rapidly. According to the annual elimination rate of 10%, the amount of waste silicone rubber products produced will exceed 30kt, which is a problem that cannot be ignored. Organosilicon compounds cannot be decomposed naturally, so landfills cannot decompose waste silicone rubber. The process of converting waste silicone rubber into white carbon black by burning consumes a lot of energy. The price of silicone rubber raw materials is relatively high, and the production and accumulation of waste silicone rubber will not only occupy a large number of factories and pollute the environment, but also lead to an increase in costs, causing great economic pressure on enterprises. Therefore, recycling waste silicone rubber is of great significance to reduce environmental pollution and improve economic benefits.

At present, the main methods of recycling waste silicone rubber are physical method, chemical method and biological method. Among them, physical methods mainly include crushing, crushing, and hot pressing to convert waste silicone rubber into reusable powder or granules. However, because this method cannot change the molecular structure and performance of waste silicone rubber, it can only be used as a filler or inferior raw material. It is no longer applicable after the silicone rubber is gradually oxidized after repeated use, and it will cause energy consumption and equipment loss. Chemical methods mainly include solvent method, catalytic cracking method and other methods to decompose waste silicone rubber into organic silicon monomer or other low molecular weight substances.

In addition, some disproportionation side reactions also occur in the reaction to generate cross-linked polymers, which also affect the formation of cyclic dimethylcyclosiloxane to a certain extent. Monomethyltrichlorosilane easily forms trifunctional groups in the hydrolysis link. The hydrolyzate is excessively cross-linked and produces a large number of silanol groups, the hydroxyl group is hydrophilic, and the molecular skeleton is hydrophobic, resulting in hydrolytic cementation, resulting in an increase in the viscosity of the hydrolyzate, increasing the difficulty of separating chloride ions in the hydrolyzate, and even the occurrence of hydrolyzate Adhesive hydrolysis equipment. At the same time, when the trifunctional hydrolyzate is brought to pyrolysis, the material is easy to cement, it is difficult to force dry during intermittent pyrolysis in a single tank, and the amount of wet residue is large, which will easily cause octamethylcyclotetrasiloxane in dimethylcyclosiloxane (DMC) The content of alkane (D4) is reduced; and the high-viscosity hydrolyzate will cause the high content of impurities such as acid value, terminal chlorine, and trifunctional connection in the hydrolyzate, which cannot meet the production requirements of high-quality silicone rubber.

Contents of the invention

The invention provides a treatment process for recovering silicone rubber, which uses methanol, diethylamine, and hexane as filler recovery agents, tetramethylammonium hydroxide as a catalyst, and n-stearyl alcohol as a solvent cracking process + filler recovery method , realizing the effective recycling of waste silicone rubber; the present invention uses a solvent cracking process to process waste silicone rubber, which reduces the carbonization probability of siloxane chain links, and is conducive to improving the generation rate of cyclosiloxane to a certain extent; The invention uses tetramethylammonium hydroxide as a catalyst, which overcomes the problem that the KOH catalyst remains in dimethylsiloxane and cannot meet the production requirements of high-quality silicone rubber, and improves the ring body yield. efficiency, and the filler is effectively separated; in the present invention, after polydimethylsiloxane cleavage reaches an equilibrium stage, buffer solution potassium dihydrogen phosphate is added to promote its formation of a ring structure.

The purpose of the present invention can be achieved through the following technical solutions:

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break the waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add methanol, diethylamine, hexane and tetramethylammonium hydroxide to the reaction kettle, stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: add n-stearyl alcohol to the reactor, and heat up to react;

Step 5: add potassium dihydrogen phosphate buffer solution into the reaction kettle, continue to heat up the reaction, collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

As a preferred solution of the present invention, the dosage ratio of the silicone rubber powder, methanol, diethylamine and tetramethylammonium hydroxide described in step 2 is 5g: 3mL-5mL: 2.5-10mL: 0.4-0.6g.

As a preferred version of the present invention, the volume ratio of the amount of hexane added to the diethylamine in step 4 is 1:1.

As a preferred version of the present invention, the ratio of the volume of n-stearyl alcohol added in step 4 to the volume of the reactor is 1:20-25.

As a preferred solution of the present invention, in step 4, the temperature of the reactor is controlled at 120-130° C. after the temperature rise, and the pressure of the reactor is controlled at 5-10 kPa.

As a preferred version of the present invention, the molar ratio of potassium dihydrogen phosphate described in step 5 to tetramethylammonium hydroxide described in step 2 is 0.8-1:1.

As a preferred solution of the present invention, the temperature after the temperature rise in Step 5 is 180°C.

As a preferred version of the present invention, the reaction time in step 5 is 90-120min.

Beneficial effects of the present invention:

1. The present invention provides a treatment process for reclaiming silicone rubber, through using methanol, diethylamine, hexane as filler recovery agent, tetramethylammonium hydroxide as catalyst, n-stearyl alcohol as solvent cracking process+filler recovery The method realizes the effective recycling of waste silicone rubber, and the recovered dimethylsiloxane has a high content of rings.

2. In the treatment process for reclaiming silicone rubber provided by the present invention, the waste silicone rubber is treated using a solvent cracking process. The solvent is n-octadecyl alcohol, which is a kind of inert substance. It has the advantages of high boiling point, low viscosity and strong heat transfer ability. Reduce the cracking side reaction and the occurrence of carbon-silicon bond and carbon-hydrogen bond breakage in the siloxane chain to generate C and H ₂ reactions, reduce the carbonization probability of the siloxane chain, and to a certain extent help to improve the formation of cyclosiloxane rate.

3. In the treatment process of reclaiming silicone rubber provided by the present invention, use tetramethylammonium hydroxide as a catalyst, tetramethylammonium hydroxide exists stably at a temperature not exceeding the decomposition point, and decomposes into trimethylammonium rapidly when exceeding the decomposition point Amines and Methanol. When the catalysis is finished, it is easy to remove without leaving any residue. It is non-polluting to silicone products, so it is also called "temporary catalyst". Tetramethylammonium hydroxide as a catalyst overcomes the problem that the traditional strong base KOH catalyzes and remains in dimethylsiloxane, which cannot meet the production requirements of high-quality silicone rubber.

4. In the present invention, diethylamine and methanol can effectively swell silicone rubber, so that the separation of fillers and polydimethylsiloxane chains, the mixture of diethylamine, methanol and hexane, not only very effectively promotes the Depolymerization of silica and alumina-silica rubber, and complete separation of fillers by filtration prior to removal of monomers and solvents. Higher levels of cyclosiloxane can be obtained in distillation after solvent removal. At the same time, the use of tetramethylammonium hydroxide instead of KOH not only improves the yield of cyclosiloxane, but also effectively separates the filler.

5. In the present invention, after polydimethylsiloxane cracking reaches the equilibrium stage, buffer solution potassium dihydrogen phosphate is gradually added to neutralize excessive disiliconate, and it is converted into monosiliconate, thereby reducing the amount caused by one or more The smaller number of potassium silanolates composed of two Si-O units facilitates their formation into a ring structure.

6. The present invention effectively recycles the waste silicone rubber filler in the process, realizes the recycling of waste materials, avoids waste of resources, and is environmentally friendly.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of diethylamine, 2.5L of hexane, and 0.4kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the volume ratio of n-stearyl alcohol to the volume of the reactor is 1:20, heat up to 120°C for reaction, and control the pressure of the reactor at 5kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 90 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.8:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

Example 2

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3.5L of methanol, 4.5L of diethylamine, 4.5L of hexane, and 0.45kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a mixed solution;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:21, heat up to 122°C for reaction, and control the pressure of the reactor at 6kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 97 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.85:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

Example 3

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 4L of methanol, 6.8L of diethylamine, 6.8L of hexane, and 0.5kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:23, heat up to 125°C for reaction, and control the pressure of the reactor at 7kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 105 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.9:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

Example 4

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of diethylamine, 2.5L of hexane, and 0.4kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a mixed solution;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:24, heat up to 127°C for reaction, and control the pressure of the reactor at 8kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 112 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.95:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

Example 5

A treatment process for reclaiming silicone rubber, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of diethylamine, 2.5L of hexane, and 0.4kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the volume ratio of n-stearyl alcohol to the volume of the reactor is 1:25, heat up to 130°C for reaction, and control the pressure of the reactor at 10kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 120 minutes, control the molar ratio of potassium dihydrogen phosphate to tetramethylammonium hydroxide described in step 2 to 1:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

Comparative example 1

A treatment process for reclaiming silicone rubber, compared with Example 1, does not add ethylenediamine, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of hexane, and 0.4kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the volume ratio of n-stearyl alcohol to the volume of the reactor is 1:20, heat up to 120°C for reaction, and control the pressure of the reactor at 5kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 90 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.8:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

All the other steps are the same as in Example 1.

Comparative example 2

A treatment process for reclaiming silicone rubber, compared with Example 2, does not add hexane, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3.5L of methanol, 4.5L of diethylamine, and 0.45kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a mixed solution;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:21, heat up to 122°C for reaction, and control the pressure of the reactor at 6kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 97 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.85:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

All the other steps are the same as in Example 2.

Comparative example 3

A kind of treatment process of reclaiming silicone rubber, compared with embodiment 3, does not add diethylamine+hexane, comprises the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 4L of methanol and 0.5kg of tetramethylammonium hydroxide to the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:23, heat up to 125°C for reaction, and control the pressure of the reactor at 7kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 105 minutes, control the molar ratio of potassium dihydrogen phosphate and tetramethylammonium hydroxide described in step 2 to 0.9:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

All the other steps are the same as in Example 3.

Comparative example 4

A treatment process for reclaiming silicone rubber, compared with Example 4, does not add potassium dihydrogen phosphate buffer, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of diethylamine, 2.5L of hexane, and 0.4kg of tetramethylammonium hydroxide into the reaction kettle, and stir at room temperature to obtain a mixed solution;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the ratio of the volume of n-stearyl alcohol to the volume of the reactor is 1:24, heat up to 127°C for reaction, and control the pressure of the reactor at 8kPa;

Step 5: heat up the reaction kettle for another 112 minutes, control the temperature after the temperature rise to 180°C, collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

All the other steps are the same as in Example 4.

Comparative example 5

A treatment process for reclaiming silicone rubber, compared with embodiment 5, replaces tetramethylammonium hydroxide with KOH, comprising the following steps:

Step 1: Break 5kg of waste silicone rubber into powder and put it into the reaction kettle;

Step 2: Add 3L of methanol, 2.5L of diethylamine, 2.5L of hexane, and 0.4kg of KOH into the reaction kettle, and stir at room temperature to obtain a suspension;

Step 3: filtering the suspension to separate the solid;

Step 4: Add n-stearyl alcohol to the reactor, the volume ratio of n-stearyl alcohol to the volume of the reactor is 1:25, heat up to 130°C for reaction, and control the pressure of the reactor at 10kPa;

Step 5: Add potassium dihydrogen phosphate buffer solution to the reaction kettle to raise the temperature and react for 120 minutes, control the molar ratio of potassium dihydrogen phosphate to tetramethylammonium hydroxide described in step 2 to 1:1, and control the temperature after heating to 180°C , collect the condensate, and dry it with anhydrous sodium sulfate to obtain dimethylsiloxane;

Step 6: Treat the solid recovered in Step 3 with a mixture of diethylamine and hexane to obtain a filler.

All the other steps are the same as in Example 5.

The recovery rates of fillers and dimethylcyclosiloxane in Examples 1-5 and Comparative Examples 1-5 are shown in Table 1.

Table 1

It can be obtained from Table 1 that a kind of treatment process for reclaiming silicone rubber provided by Examples 1-5 has good filler recovery and dimethylsiloxane recovery, and the reclaimed silicone rubber provided by Comparative Examples 1-4 The treatment process has different degrees of reduction in the recovery rate of the filler and the recovery rate of dimethylsiloxane. A kind of treatment process for reclaiming silicone rubber provided by Examples 1-5 and the reclaimed silicone rubber provided by Comparative Example 5 The recovery rate of the filler obtained by the treatment process is equivalent to the recovery rate result of dimethylsiloxane.

In the description of the specification, descriptions referring to the terms "one embodiment", "example", "specific example" and the like mean that specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one of the present invention. Examples or examples. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above content is only an example and description of the present invention. Those skilled in the art will make various modifications or supplements to the described specific embodiments or replace them in similar ways, as long as they do not deviate from the invention or exceed the rights of the present invention. The scope defined in the claims should all belong to the protection scope of the present invention.

Claims (8)

1. A treatment process for recycling silicon rubber is characterized by comprising the following steps: the treatment process comprises the following steps:

step one: crushing waste silicone rubber into powder, and placing the powder into a reaction kettle;

step two: adding methanol, diethylamine, hexane and tetramethylammonium hydroxide into a reaction kettle, and stirring at room temperature to obtain a suspension;

step three: filtering the suspension to separate out solid;

step four: adding n-octadecanol into a reaction kettle, and heating for reaction;

step five: adding potassium dihydrogen phosphate buffer solution into a reaction kettle, continuing to perform heating reaction, collecting condensate, and drying with anhydrous sodium sulfate to obtain dimethyl siloxane;

step six: the solid recovered in step three was treated with a mixture of diethylamine and hexane to give a filler.

2. The process for treating recycled silicone rubber according to claim 1, wherein: in the second step, the dosage ratio of the silicon rubber powder, the methanol, the diethylamine and the tetramethylammonium hydroxide is 5g to 3mL-5mL to 2.5-10mL to 0.4-0.6g.

3. The process for treating recycled silicone rubber according to claim 1, wherein: and in the second step, the volume ratio of the addition amount of the hexane to the diethylamine is 1:1.

4. The process for treating recycled silicone rubber according to claim 1, wherein: and in the fourth step, the ratio of the added volume of the n-octadecanol to the volume of the reaction kettle is 1:20-25.

5. The process for treating recycled silicone rubber according to claim 1, wherein: in the fourth step, the temperature of the reaction kettle after temperature rise is controlled to be 120-130 ℃, and the pressure of the reaction kettle is controlled to be 5-10kPa.

6. The process for treating recycled silicone rubber according to claim 1, wherein: and in the fifth step, the molar ratio of the potassium dihydrogen phosphate to the tetramethylammonium hydroxide in the second step is 0.8-1:1.

7. The process for treating recycled silicone rubber according to claim 1, wherein: and step five, the temperature after the temperature rise is 180 ℃.

8. The process for treating recycled silicone rubber according to claim 1, wherein: and step five, the reaction time is 90-120min.