阅读说明：本技术 一种低压力密封用阻燃硅橡胶及其制备方法 (Flame-retardant silicone rubber for low-pressure sealing and preparation method thereof ) 是由 潘鹤斌 谭政新 郭韵恬 于 2020-07-17 设计创作，主要内容包括：本发明涉及硅橡胶技术领域,具体涉及一种低压力密封用阻燃硅橡胶及其制备方法。包括如下重量份的原料：复合硅橡胶100-120份、增强剂18-22份、端羟基聚二甲基硅氧烷0.5-1.5份、硅烷偶联剂0.05-0.15份、复合阻燃剂45-55份。本发明的低压力密封用阻燃硅橡胶在低压力下能起到很好的密封阻燃作用,并具有较佳的拉伸强度、断裂伸长率、撕裂强度等性能,机械强度高,稳定性高。(The invention relates to the technical field of silicone rubber, and particularly relates to low-pressure sealing flame-retardant silicone rubber and a preparation method thereof. The feed comprises the following raw materials in parts by weight: 100-120 parts of composite silicon rubber, 18-22 parts of reinforcing agent, 0.5-1.5 parts of hydroxyl-terminated polydimethylsiloxane, 0.05-0.15 part of silane coupling agent and 45-55 parts of composite flame retardant. The low-pressure sealing flame-retardant silicone rubber can play a good role in sealing flame retardance under low pressure, has good performances such as tensile strength, elongation at break, tearing strength and the like, and is high in mechanical strength and stability.)

1. The flame-retardant silicone rubber for low-pressure sealing is characterized in that: the feed comprises the following raw materials in parts by weight:

2. the flame-retardant silicone rubber for low-pressure sealing according to claim 1, wherein: the composite silicon rubber is a mixture of methyl vinyl silicon rubber A and methyl vinyl silicon rubber B in a weight ratio of 50-70: 30-50; the methyl vinyl silicone rubber A has a vinyl content of 0.06-0.10% and a molecular weight of 55-65 ten thousand; the methyl vinyl silicone rubber B has a vinyl content of 0.13-0.20% and a molecular weight of 55-65 ten thousand.

3. The flame-retardant silicone rubber for low-pressure sealing according to claim 1, wherein: the reinforcing agent has a specific surface area of 200-300m²Precipitated silica in a/g ratio; the silane coupling agent is at least one of vinyl trimethoxy silane, propyl trimethoxy silane and vinyl triethoxy silane.

4. The flame-retardant silicone rubber for low-pressure sealing according to claim 1, wherein: the hydroxyl-terminated polydimethylsiloxane is a mixture of hydroxyl-terminated polydimethylsiloxane A with the hydrogen content of 3-5% and hydroxyl-terminated polydimethylsiloxane B with the hydrogen content of 6-10% in a weight ratio of 1: 1.

5. The flame-retardant silicone rubber for low-pressure sealing according to claim 1, wherein: each part of the composite flame retardant comprises 18-22 parts of aluminum hydroxide, 3-8 parts of melamine cyanuric acid, 20-30 parts of ammonium polyphosphate and 0.01-0.02 part of platinum flame retardant.

6. A method for preparing the flame-retardant silicone rubber for low-pressure sealing according to any one of claims 1 to 5, characterized in that: the method comprises the following steps:

s1: according to the parts by weight, preheating the composite flame retardant, stirring for the first time, then adding the silane coupling agent, and stirring for the second time to obtain composite powder;

s2: mixing the composite silicone rubber, one-third of the amount of the reinforcing agent and one-third of the amount of the hydroxyl-terminated polydimethylsiloxane, stirring and banburying, adding the rest two-thirds of the amount of the reinforcing agent and two-thirds of the amount of the hydroxyl-terminated polydimethylsiloxane twice, mixing into a mass, heating and mixing, adding the composite powder prepared in the step S1, and kneading the materials to prepare a kneaded material; then discharging the kneaded material, uniformly milling, rolling the roller, and standing for 1-5h to obtain a sizing material;

s3: and (5) uniformly milling the rubber prepared in the step S2, and filtering the rubber through a 180-mesh 220-mesh filter screen to prepare the flame-retardant silicone rubber for low-pressure sealing.

7. The preparation method of the flame-retardant silicone rubber for low-pressure sealing according to claim 6, characterized in that: in the step S1, the temperature is raised and preheated to 58-62 ℃, and the time length of the first stirring is 5-15 min; the time length of the second stirring is 15-25 min.

8. The preparation method of the flame-retardant silicone rubber for low-pressure sealing according to claim 6, characterized in that: in the step S2, the specific steps of heating rubber mixing and kneading materials are as follows: heating the mixed and agglomerated materials to 95-105 ℃, and carrying out primary vacuum-pumping treatment; and then adding the composite powder, kneading into a dough, and then carrying out secondary vacuum-pumping treatment to obtain the kneaded material.

9. The method for preparing the flame-retardant silicone rubber for low-pressure sealing according to claim 8, wherein the method comprises the following steps: the vacuum degree of the first vacuum pumping treatment is-0.08 MPa to-0.09 MPa, and the time of the vacuum pumping treatment is 50-70 min.

10. The method for preparing the flame-retardant silicone rubber for low-pressure sealing according to claim 8, wherein the method comprises the following steps: the vacuum degree of the second vacuum-pumping treatment is-0.08 MPa to-0.09 MPa, and the time of the vacuum-pumping treatment is 50-70 min.

Technical Field

The invention relates to the technical field of silicone rubber, and particularly relates to low-pressure sealing flame-retardant silicone rubber and a preparation method thereof.

Background

The silicone rubber has good aging resistance and stability and wide application range, is mostly applied to products such as silicone tubes, electric power coating materials, sealing materials and the like, but generally the silicone rubber is not flame-retardant and fireproof, and the problem of easy combustion in fire accidents is solved.

Disclosure of Invention

In order to overcome the defects and shortcomings in the prior art, the invention aims to provide the low-pressure sealing flame-retardant silicone rubber which can play a good sealing flame-retardant role under low pressure, has better performances such as tensile strength, elongation at break, tearing strength and the like, and is high in mechanical strength and stability.

The invention also aims to provide a preparation method of the low-pressure sealing flame-retardant silicone rubber, which has the advantages of convenient operation and control, stable quality, high production efficiency, low production cost, high flame retardance of the prepared silicone rubber, better mechanical strength and stability and capability of large-scale industrial production.

The purpose of the invention is realized by the following technical scheme: the flame-retardant silicone rubber for low-pressure sealing comprises the following raw materials in parts by weight:

according to the invention, the raw materials are adopted to prepare the silicone rubber, and the prepared silicone rubber can play a good role in sealing and flame retardance under low pressure, has good performances such as tensile strength, elongation at break, tearing strength and the like, and is high in mechanical strength and stability.

Wherein, the mechanical strength of the silicon rubber can be improved by adopting the reinforcing agent; the adopted hydroxyl-terminated polydimethylsiloxane can avoid the structural phenomena of hardening, low plasticity, low processing performance and the like of the silicon rubber in the storage and placement process, improve the stability of the silicon rubber, (if the structural silicon rubber occurs, the material mixing or heat treatment is needed again to improve the structural phenomenon, but the process cost is increased, the production efficiency and the quality are reduced), and meanwhile, the hydroxyl-terminated polydimethylsiloxane can react with Si-OH groups on the surface of an enhancer (precipitated white carbon black) to hydrophobize the silicon rubber, so that the dispersibility of the enhancer in a silicon rubber system is improved, and the structuring of the silicon rubber is inhibited; the prepared silicone rubber has better rebound resilience by strictly controlling the dosage of the hydroxyl-terminated polydimethylsiloxane, if the dosage of the hydroxyl-terminated polydimethylsiloxane is too much, the rebound resilience of the silicone rubber is reduced, the hardness is reduced, and if the dosage of the hydroxyl-terminated polydimethylsiloxane is too little, the adhesive bonding property among raw materials is reduced, and the structuralization phenomenon is easy to occur.

The adopted silane coupling agent can play a role in modification treatment, can improve the properties of the silicone rubber such as tensile strength, elongation at break, tearing strength and the like, improves the wettability and dispersibility of materials (such as a composite flame retardant) in a silicone rubber system, inhibits the hue change of the silicone rubber material in the vulcanization molding process, and ensures that the surface of the prepared silicone rubber has no adhesive feeling; the adopted composite flame retardant can improve the heat resistance and the flame retardance of the silicone rubber layer, isolate oxygen and achieve the flame retardant effect of heat insulation and oxygen isolation.

Preferably, the composite silicone rubber is a mixture of methyl vinyl silicone rubber A and methyl vinyl silicone rubber B in a weight ratio of 50-70: 30-50; the methyl vinyl silicone rubber A has a vinyl content of 0.06-0.10% and a molecular weight of 55-65 ten thousand; the methyl vinyl silicone rubber B has a vinyl content of 0.13-0.20% and a molecular weight of 55-65 ten thousand.

According to the invention, two methyl vinyl silicone rubbers with different vinyl contents and different molecular weights are compounded to form a composite silicone rubber component, the vinyl contents and the molecular weights of the two are strictly controlled, and the characteristics of high molecular weight and long main chain are utilized, so that the intermolecular acting force is large, and the prepared silicone rubber has better mechanical strength and processing formability, wherein if the vinyl contents of the adopted methyl vinyl silicone rubber A and the adopted methyl vinyl silicone rubber B are too small, the vulcanization effect of the silicone rubber is reduced, and if the vinyl contents of the methyl vinyl silicone rubber are too large, the heat resistance of the vulcanized silicone rubber is reduced; if the molecular weights of the methyl vinyl silicone rubber a and the methyl vinyl silicone rubber B are low, the mechanical strength and the processability of the silicone rubber finished product are reduced.

More preferably, the chemical formulas of the methyl vinyl silicone rubber a and the methyl vinyl silicone rubber B are as follows:

wherein n is 8770-8780, m is 1-10; the methyl vinyl silicone rubber B has n of 8050-8100 and m of 11-15.

More preferably, the compound rubber is subjected to the following modification treatment before banburying and use:

weighing 50-70 parts of methyl vinyl silicone rubber A, 30-50 parts of methyl vinyl silicone rubber B and 8-12 parts of chlorinated polyethylene, uniformly mixing, heating to 80-90 ℃, carrying out banburying stirring, then adding 3-8 parts of magnesium oxide, continuously heating to 95 ℃, carrying out banburying stirring, and discharging to obtain the modified composite rubber.

According to the invention, the modified composite rubber is prepared through the steps, and the chlorinated polyethylene is used for carrying out compatible chloride ions to mutually draw the front ends of the methyl vinyl silicone rubber A and the methyl vinyl silicone rubber B, so that the compatibility between the methyl vinyl silicone rubber A and the methyl vinyl silicone rubber B is improved, and the homogenization time between the methyl vinyl silicone rubber A and the methyl vinyl silicone rubber B is shortened; meanwhile, the introduced chlorinated polyethylene can ensure that the prepared composite rubber has better weather resistance, aging resistance and flame retardance, better toughness and better rebound resilience.

The activity of the magnesium oxide introduced in the process can improve the crosslinking density of the rubber, further enhance the mechanical properties such as tensile strength and the like of the rubber, and improve the flame retardance of the composite rubber.

Preferably, the reinforcing agent has a specific surface area of 200-300m²Precipitated silica in a/g ratio; the silane coupling agent is at least one of vinyl trimethoxy silane, propyl trimethoxy silane and vinyl triethoxy silane.

The invention adopts the precipitated white carbon black as a reinforcing agent, strictly controls the specific surface area and the pH value of the precipitated white carbon black, has small particle size, can fully disperse the precipitated white carbon black in a silicon rubber system, and effectively improves the mechanical strength of the silicon rubber layer.

By adopting the silane coupling agent, the invention can inhibit or reduce the hue change in the vulcanization process, so that the surface of the product has no adhesive feeling, obviously improves the performances of the silicon rubber system such as tensile strength, elongation at break, tearing strength and the like, improves the wettability and the dispersibility of the material in the silicon rubber system, and promotes the polymerization crosslinking of the silicon rubber material.

Preferably, the hydroxyl-terminated polydimethylsiloxane is a mixture of hydroxyl-terminated polydimethylsiloxane A with the hydrogen content of 3-5% and hydroxyl-terminated polydimethylsiloxane B with the hydrogen content of 6-10% in a weight ratio of 1: 1.

The invention adopts two terminal hydroxyl polydimethylsiloxane with different hydrogen content to be compounded for use, and the terminal hydroxyl polydimethylsiloxane can react with Si-OH groups on the surface of a reinforcing agent (precipitated white carbon black) to hydrophobize the reinforcing agent, improve the dispersibility of the reinforcing agent in a silicon rubber system, inhibit the structuring of the silicon rubber and enable the prepared silicon rubber to have the resilience of a foot rest.

Preferably, each part of the composite flame retardant comprises 18-22 parts of aluminum hydroxide, 3-8 parts of melamine cyanuric acid, 20-30 parts of ammonium polyphosphate and 0.01-0.02 part of platinum flame retardant.

According to the invention, the flame retardant of the above kind is compounded to serve as a composite flame retardant, so that the flame retardant property of the silicone rubber can be effectively improved, and the heat insulation and oxygen isolation effects are achieved; the aluminum hydroxide is an environment-friendly inorganic flame retardant additive, has stable performance in water, light and heat environments, is non-volatile, can prevent fuming, does not produce drops and toxic gas, and does not pollute the environment after combustion; when the adopted melamine cyanuric acid is burnt, the formed carbon foam layer plays a role in protecting the polymer, insulating heat and oxygen, and by introducing the melamine cyanuric acid, the smoke density and toxic gas of the silicon rubber polymer can be greatly reduced, and meanwhile, irritant hydrogen halide gas is not generated; the adopted ammonium polyphosphate belongs to coated white powder, and the expanded halogen-free flame retardant with the polymerization degree of more than 1500 forms a carbon foam layer during combustion, has good compatibility with silicon rubber components, does not precipitate and has good thermal stability; the adopted platinum flame retardant promotes oxidative degradation on the surface of the silicon rubber which is in contact with air to form a high cross-linking structure, so that organic groups on the surface are reduced, a siloxane film which is similar to non-combustible is formed, air is shielded, and flame can not spread into the silicon rubber and is self-extinguished any more.

The other purpose of the invention is realized by the following technical scheme: the preparation method of the flame-retardant silicone rubber for low-pressure sealing comprises the following steps:

s1: according to the parts by weight, preheating the composite flame retardant, stirring for the first time, then adding the silane coupling agent, and stirring for the second time to obtain composite powder;

s2: mixing the composite silicone rubber, one-third of the amount of the reinforcing agent and one-third of the amount of the hydroxyl-terminated polydimethylsiloxane, stirring and banburying, adding the rest two-thirds of the amount of the reinforcing agent and two-thirds of the amount of the hydroxyl-terminated polydimethylsiloxane twice, mixing into a mass, heating and mixing, adding the composite powder prepared in the step S1, and kneading the materials to prepare a kneaded material; then discharging the kneaded material, uniformly milling, rolling the roller, and standing for 1-5h to obtain a sizing material;

s3: and (5) uniformly milling the rubber prepared in the step S2, and filtering the rubber through a 180-mesh 220-mesh filter screen to prepare the flame-retardant silicone rubber for low-pressure sealing.

The preparation method has the advantages that the flame-retardant silicone rubber for low-pressure sealing is prepared by adopting the steps, the process is simple, the operation and the control are convenient, the quality is stable, the production efficiency is high, the production cost is low, the prepared flame-retardant silicone rubber for low-pressure sealing has the characteristics of high flame retardance, small open flame and the like, and the mechanical strength and the stability are good, so that the large-scale industrial production can be realized; the composite flame retardant is compounded with the silane coupling agent by strictly controlling the adding sequence and the processing parameters of other materials, so that the silane coupling agent is subjected to surface modification relative to the composite flame retardant, and the subsequent dispersibility and associativity of the composite flame retardant in the composite silicone rubber are promoted; the reinforcing agent and the hydroxyl-terminated polydimethylsiloxane are added into the composite silicone rubber in batches, so that the silicone rubber system can be gradually reinforced and structurally inhibited, the reinforcing agent and the hydroxyl-terminated polydimethylsiloxane are gradually mixed into the silicone rubber system, the mechanical strength and toughness of the silicone rubber can be gradually adjusted and improved, and if the reinforcing agent is added all at once, the flexibility and resilience of the silicone rubber can be reduced. And adding the composite powder in the mixed heating rubber mixing process, promoting the dispersibility of the composite flame retardant in a silicon rubber system under the action of a silane coupling agent, and promoting the crosslinking polymerization. And the subsequent processing vulcanization speed and stability of the silicon rubber are improved, the consumption of vulcanizing agents is reduced, the vulcanization time is shortened, the vulcanization temperature is reduced, and the mechanical property of the silicon rubber is effectively improved.

Preferably, in the step S1, the temperature is raised and preheated to 58-62 ℃, and the time length of the first stirring is 5-15 min; the time length of the second stirring is 15-25 min. By strictly controlling the temperature of temperature rise and preheating and the time length of two times of stirring, the dispersibility of the silane coupling agent in the composite flame retardant can be promoted, the surface modification of the composite flame retardant is promoted, and the subsequent dispersibility of the composite flame retardant in a silicone rubber system is improved.

Preferably, in step S2, the specific steps of heating rubber mixing and kneading the materials are as follows: heating the mixed and agglomerated materials to 95-105 ℃, and carrying out primary vacuum-pumping treatment; and then adding the composite powder, kneading into a dough, and then carrying out secondary vacuum-pumping treatment to obtain the kneaded material.

Preferably, the vacuum degree of the first vacuum-pumping treatment is-0.08 MPa to-0.09 MPa, and the time of the vacuum-pumping treatment is 50-70 min.

Preferably, the vacuum degree of the second vacuum-pumping treatment is-0.08 MPa to-0.09 MPa, and the time of the vacuum-pumping treatment is 50-70 min.

According to the invention, the materials are subjected to vacuum treatment after being heated, so that the intersolubility of the raw materials can be improved, the stability of a silicon rubber system is effectively improved, the subsequent vulcanization speed is improved, the kneading and agglomerating effect of the materials is improved, and the strength of the silicon rubber layer is improved. And the internal bonding polymerization of the silicone rubber can be improved by strictly controlling the time and the vacuum degree of vacuum treatment, the subsequent processes of rolling and pressing and the like are easy to carry out, the processing formability is good, and the silicone rubber has better mechanical strength such as tensile strength, elongation at break, tearing strength and the like.

The invention has the beneficial effects that: the low-pressure sealing flame-retardant silicone rubber can play a good role in sealing flame retardance under low pressure, has good performances such as tensile strength, elongation at break, tearing strength and the like, and is high in mechanical strength and stability.

The preparation method of the flame-retardant silicone rubber for low-pressure sealing has the advantages of convenient operation and control, stable quality, high production efficiency and low production cost, can ensure that the prepared silicone rubber has high flame retardance, has better mechanical strength and stability, and can realize large-scale industrial production.

Detailed Description

The present invention will be further described with reference to the following examples for facilitating understanding of those skilled in the art, and the description of the embodiments is not intended to limit the present invention.