1. The reclaimed material silicone rubber is characterized by comprising the following raw material components in parts by weight: 100 parts of methyl vinyl raw rubber, 30-60 parts of white carbon black, 1-60 parts of reclaimed materials, 0.3-4 parts of structure control agent, 0.1-0.3 part of silane coupling agent and 0.1-0.5 part of demolding auxiliary agent.

2. The reclaimed silicone rubber according to claim 1, wherein the specific surface area of the silica white is 175 square meters per gram.

3. The reclaimed silicone rubber according to claim 2, wherein the white carbon black is a white carbon black without surface treatment, and is selected from fumed silica and precipitated silica.

4. The reclaimed silicone rubber according to claim 1, wherein the reclaimed material is a silica sulfide powder obtained by physical crushing and grinding.

5. The reclaimed silicone rubber according to claim 4, wherein after grinding, the reclaimed material is passed through a 30-80 mesh screen.

6. The reclaimed silicone rubber according to claim 4, wherein the reclaimed material has a particle size of 0.1 to 1 mm.

7. The reclaimed silicone rubber of claim 1 wherein the methyl vinyl crude rubber has a molecular weight of 55 to 66 ten thousand.

8. The reclaimed silicone rubber according to claim 1, wherein the structure-controlling agent is a hydroxy silicone oil; the silane coupling agent is vinyl trimethoxy silane; the demolding assistant is at least one of zinc stearate, calcium stearate and barium stearate.

9. The recycled silicone rubber as claimed in any one of claims 1 to 8, wherein the recycled silicone rubber has physical properties of Shore A hardness of 22-58 degrees, elongation of 302-801%, tensile strength of 5.8MPa or more, and tear strength of 2.0 x 10⁴N/m or more.

10. The method for preparing reclaimed silicone rubber according to any one of claims 1 to 9, comprising the steps of:

putting methyl vinyl raw rubber and a demolding auxiliary agent into an internal mixer at one time, and mixing for 10-20 minutes at the temperature of below 80 ℃;

putting the white carbon black into an internal mixer for three times, putting the structure control agent and the white carbon black into the internal mixer, kneading for 1.5-2.5 hours at 90-130 ℃ after the white carbon black is completely mixed into a mass;

after the mixing is finished, putting the reclaimed materials into the internal mixer for 5-8 times, putting the silane coupling agent along with the reclaimed materials, and after the reclaimed materials are mixed and agglomerated, putting the mixture at 130-170 ℃ to-6 multiplied by 10^-2～-8×10^-2Vacuumizing under Mpa for 1.5-2.5 h;

and after the vacuum is finished, cooling to below 80 ℃, and discharging to obtain the reclaimed silica gel.

Background

With the deepening of the cognition of the characteristics of silica gel such as high temperature resistance, low temperature resistance, oil resistance, no toxicity, flame retardance, stable chemical property and the like, the silica gel is widely applied to various industries such as the aerospace field, the medical field, automobile accessories, articles for daily use and the like. However, the treatment of vulcanized silica gel (including the defective products and scraps of vulcanized silica gel) is an industrial problem. At present, DMC (dimethyl siloxane ring mixture) raw material is produced by cracking under high temperature condition by using strong alkali. However, the recovery process has high recovery cost and serious environmental pollution, and is easy to explode in pyrolysis, so that great potential safety hazard exists.

Disclosure of Invention

The invention provides a reclaimed silicone rubber and a preparation method thereof, which are characterized in that vulcanized silicone rubber is physically crushed and ground into particles with a certain particle size, and the particles are used as raw materials for producing the silicone rubber for recycling, so that the problems of high cost, high pollution and high risk in the process of recovering the vulcanized silicone rubber are effectively solved on the premise that the obtained silicone rubber meets the requirements of hardness, elasticity, heat resistance, tensile strength at break and the like.

In order to achieve the aim, the invention provides reclaimed silicone rubber which comprises the following raw materials in parts by weight: 100 parts of methyl vinyl raw rubber, 30-60 parts of white carbon black, 1-60 parts of reclaimed materials, 0.3-4 parts of structure control agent, 0.1-0.3 part of silane coupling agent and 0.1-0.5 part of demolding auxiliary agent.

According to the scheme, the raw materials such as methyl vinyl raw rubber and the demolding auxiliary agent are mixed, the reclaimed materials with certain proportion and certain particle size requirements are added on the premise that the mass ratio of white carbon black is not increased, and the obtained silicone rubber effectively solves the problems of high cost, high pollution and high risk in the process of reclaiming vulcanized silicone rubber on the premise that the requirements of hardness, elasticity, heat resistance, tensile strength at break and the like are met.

Preferably, the specific surface area of the white carbon black is 175 square meters per gram and 225 square meters per gram. It can be understood that the specific surface area of the white carbon black is limited by the scheme, and the purpose is that the white carbon black under the specific surface area can increase the reinforcing effect on the silicone rubber, so that the elastic strength and the tensile strength at break of the silicone rubber are improved.

Preferably, the white carbon black is white carbon black without surface treatment, and is selected from fumed white carbon black or precipitated white carbon black. It can be understood that the white carbon black selected in the scheme has good dispersibility and reinforcement in the silicone rubber, and the reinforcement effect of the white carbon black on the silicone rubber can be further improved.

Preferably, the reclaimed material is silica sulfide powder obtained by physical crushing and grinding. Preferably, after grinding, the recovered material is passed through a 30-80 mesh screen. Still more preferably, the reclaimed material has a particle size of 0.1 to 1 mm. It is understood that the particle size of the reclaimed material has a great influence on the properties of the final silicone rubber product, and if the particle size is too large, the reclaimed material is unevenly dispersed in the silicone rubber material, so that the usability of the rubber material is easily deteriorated, and the surface of the final product is not smooth.

Preferably, the methyl vinyl crude rubber has a molecular weight of 55 to 65 ten thousand. More preferably, the methyl vinyl crude rubber has a molecular weight of 58 to 62 ten thousand.

Preferably, the structure control agent is hydroxyl silicone oil; the silane coupling agent is vinyl trimethoxy silane; the demolding aid is at least one selected from zinc stearate, calcium stearate and barium stearate, and zinc stearate is preferred.

Preferably, the physical standard of the reclaimed silicone rubber is to achieve the Shore A hardness of 22-58 degrees, the elongation of 302-801 percent, the tensile strength of more than 5.8MPa and the tear strength of 2.0 x 10⁴N/m or more.

The invention also provides a preparation method of the reclaimed silicone rubber according to any one of the technical schemes, which comprises the following steps:

putting methyl vinyl raw rubber and a demolding auxiliary agent into an internal mixer at one time, and mixing for 10-20 minutes at the temperature of below 80 ℃;

putting the white carbon black into an internal mixer for three times, putting the structure control agent and the white carbon black into the internal mixer, kneading for 1.5-2.5 hours at 90-130 ℃ after the white carbon black is completely mixed into a mass;

after mixing, putting the reclaimed materials into the internal mixer for 5-8 times, putting the silane coupling agent along with the reclaimed materials, and after mixing and agglomerating, vacuumizing at the temperature of 130-170 ℃ for 1.5-2.5 hours;

and after the vacuum is finished, cooling to below 80 ℃, and discharging to obtain the reclaimed silica gel.

It can be understood that the heating and vacuumizing are to make the fumed silica subjected to surface treatment fully react with the raw materials, uniformly disperse in the methyl vinyl raw rubber, and remove low molecular substances and moisture in the rubber material, so as to improve the physical properties of the finished silicone rubber product.

In the scheme, the recycled materials are added after the white carbon black and methyl vinyl raw rubber are added for reaction reinforcement, the process scientificity is guaranteed, meanwhile, the silane coupling agent vinyl trimethoxy silane is added, the dispersibility of the recycled materials and the binding capacity with silica gel can be effectively improved, each batch of production process only needs 6-8 hours, and the silica gel recycling efficiency is improved. Compared with the prior recycled material, the recycled material needs to be recycled through strong alkali cracking at high temperature, and is safer, more environment-friendly and more effective. In addition, in above-mentioned scheme, the reclaimed materials is added in step when producing silica gel, utilizes the banbury mixer to the reclaimed materials and silica gel material misce bene, still can promote the recycle efficiency of silica gel by a wide margin, has avoided the waste and the environmental pollution of raw materials.

Compared with the prior art, the invention has the advantages and positive effects that:

the invention provides a reclaimed silica gel material and a preparation method thereof, which conform to the requirements of economic development and environmental protection. The method physically crushes and grinds vulcanized silica gel into particles with certain particle size, and then the particles are recycled as raw materials for producing the silica gel. The silicone rubber prepared by the method effectively solves the problems of high cost, high pollution and high risk when the vulcanized silicone rubber is recovered on the premise of meeting the requirements of hardness, elasticity, heat resistance, tensile strength at break and the like.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

The reclaimed silica gel comprises the following raw materials: 100 parts of methyl vinyl silica gel, 30 parts of white carbon black, 20 parts of reclaimed materials, 2 parts of hydroxyl silicone oil, 0.2 part of zinc stearate and 0.1 part of vinyl trimethoxy silane.

The preparation method comprises the following steps:

putting methyl vinyl raw rubber and zinc stearate into a vacuum internal mixer, and kneading for 20 minutes (the temperature is controlled below 80 ℃);

adding the white carbon black and the hydroxyl silicone oil for 3 times, adding the next white carbon black and the next hydroxyl silicone oil after each agglomeration, introducing steam into an internal mixer to heat to 110 +/-20 ℃ after all the white carbon black and the hydroxyl silicone oil are added and agglomerated, and keeping the temperature and mixing for 2 hours;

after mixing, adding vinyltrimethoxysilane and a reclaimed material for 5-8 times, adding the vinyltrimethoxysilane and the reclaimed material for the next time after each agglomeration, heating to 150 +/-20 ℃ after all agglomeration is finished, controlling the vacuum degree to be-0.07 +/-0.01 MPa, and keeping the temperature and vacuumizing for 2 hours;

and after the vacuum is finished, cooling to below 80 ℃, and discharging to obtain the reclaimed silica gel.

Example 2

The reclaimed silica gel comprises the following raw materials: 100 parts of methyl vinyl silica gel, 35 parts of white carbon black, 25 parts of reclaimed materials, 2.5 parts of hydroxyl silicone oil, 0.2 part of calcium stearate and 0.2 part of vinyl trimethoxy silane.

The preparation method is the same as example 1.

Example 3

The reclaimed silica gel comprises the following raw materials: 100 parts of methyl vinyl silica gel, 49 parts of white carbon black, 30 parts of reclaimed materials, 3.5 parts of hydroxyl silicone oil, 0.2 part of barium stearate and 0.2 part of vinyl trimethoxy silane.

The preparation method is the same as example 1.

Example 4

The reclaimed silica gel comprises the following raw materials: 100 parts of methyl vinyl silica gel, 55 parts of white carbon black, 45 parts of reclaimed materials, 4 parts of hydroxyl silicone oil, 0.5 part of barium stearate and 0.3 part of vinyl trimethoxy silane.

The preparation method is the same as example 1.

Example 5

The reclaimed silica gel comprises the following raw materials: 100 parts of methyl vinyl silica gel, 60 parts of white carbon black, 60 parts of reclaimed materials, 4 parts of hydroxyl silicone oil, 0.1 part of zinc stearate and 0.1 part of vinyl trimethoxy silane.

The preparation method is the same as example 1.

Comparative example 1

The recycled silica gel formulation components were the same as example 1 except that the recycled particle size was 1.5 mm.

Performance criteria

In order to better illustrate the effect of the reclaimed silicone rubber prepared by the embodiment of the invention, the performance standard and the performance test result of the reclaimed silicone rubber of each embodiment and comparative example are listed.

Table 1 example 1 performance criteria and test results

Table 2 example 2 performance criteria and test results

Performance test items	Performance test method	Performance criteria	Performance test data
				Hardness of	ASTM D-2240	35±2	36
Tensile strength	ASTM D-412	5MPa or more	6.5
				Elongation rate	ASTM D-412	Over 500A	551
Tear strength	ASTM D-624	1.8*104N/m or more	2.1*104
				Degree of plasticity	ASTM D-926	130±15	135
Surface smoothness		Visual inspection	Is smooth and smooth

Table 3 example 3 performance criteria and test results

Performance test items	Performance test method	Performance criteria	Performance test data
				Hardness of	ASTM D-2240	50±2	49
Tensile strength	ASTM D-412	6.5MPa or more	6.8
				Elongation rate	ASTM D-412	More than 450	470
Tear strength	ASTM D-624	2.0*104N/m or more	2.2*104
				Degree of plasticity	ASTM D-926	180±15	190
Surface smoothness		Visual inspection	Is smooth and smooth

Table 4 example 4 performance criteria and test results

Table 5 example 5 performance criteria and test results

Performance test items	Performance test method	Performance criteria	Performance test data
				Hardness of	ASTM D-2240	70±2	58
Tensile strength	ASTM D-412	5.5MPa or more	6.0
				Elongation rate	ASTM D-412	Over 250 of	302
Tear strength	ASTM D-624	1.8*104N/m or more	2.0*104
				Degree of plasticity	ASTM D-926	260±15	272
Surface smoothness		Visual inspection	Is smooth and smooth

Table 6 comparative example 1 performance standards and test results

Performance test items	Performance test method	Performance criteria	Performance test data
				Hardness of	ASTM D-2240	20±2	21
Tensile strength	ASTM D-412	5MPa or more	5.5
				Elongation rate	ASTM D-412	Above 700	767
Tear strength	ASTM D-624	1.4*104N/m or more	1.3*104
				Degree of plasticity	ASTM D-926	100±15	106
Surface smoothness		Visual inspection	Surface grainy, NG

Based on the data in the table, the reclaimed silicone rubber provided by the application meets the requirements of hardness, elasticity, heat resistance, tensile strength at break and the like after raw materials such as methyl vinyl raw rubber, a demolding auxiliary agent and the like are mixed and reclaimed materials with certain proportion and certain particle size requirement are added on the premise of not improving the mass ratio of white carbon black. The reclaimed silicone rubber obtained in comparative example 1 can basically meet the use requirements from the viewpoint of performance test data. However, the reclaimed silica gel obtained from the reclaimed material having a particle size of 1.5mm was found to have a granular feeling on the surface and poor surface smoothness by visual inspection due to the increase in the particle size of the reclaimed material.

In addition, the reclaimed material silicon rubber provided by the invention reasonably uses reclaimed materials to replace methyl vinyl raw rubber (the proportion of the reclaimed materials in the silica gel is 1-60%), so that the raw material cost of the silica gel is reduced, the cost is reduced by 20-40%, and the problem of environmental pollution caused by a strong alkali cracking process is also avoided. Furthermore, in the silica gel, the recycled silica gel material replaces part of the white carbon black, compared with the addition of the white carbon black, the internal mixing and agglomeration time is shorter, the production period of each batch is reduced to 6-8 hours from the original 8-10 hours, and the production efficiency is also greatly improved.