KR20040072356A - A thermosetting silicone rubber composition with storage stability and self-extinguishing property - Google Patents

Abstract

PURPOSE: Provided is a heat curable silicone rubber composition, which has excellent mechanical properties, self-extinguishing property and shelf stability, and thus does not cause crape hardening of an uncured compound with time. CONSTITUTION: The silicone rubber composition comprises: 100 parts by weight of crude silicone rubber; 1-100 parts by weight of a filler that is silica having a specific surface area of 100-300 m¬2/g and an average particle size of 7-16 nm; 0.0001-1 parts by weight of a platinum compound (in which Pt content in organic substances is 5%); 0.001-1 parts by weight of an azo compound; 0.01-3 parts by weight of a rare earth metal compound (in which the rare earth metal content in organic substances is 5%); 1-40 parts by weight of iron oxides (FeO, Fe2O3, Fe3O4); 1-20 parts by weight of titanium oxides; 1-40 parts by weight of calcium carbonate; 1-40 parts by weight of aluminum hydroxide or magnesium hydroxide; 1-60 parts by weight of an extender (diatomaceous earth or quartz powder having a particle size of 100 microns or less); 0.1-10 parts by weight of a processing aid; 0.001-1 parts by weight of an internal release agent comprising an organic fatty acid and a metal salt; 0.01-10 parts by weight of a titanate compound; and 0.5-3 parts by weight of an organic peroxide.

Description

Thermosetting silicone rubber composition with storage stability and self-extinguishing property

The present invention relates to a thermosetting silicone rubber composition having storage stability and self-extinguishing, and more particularly, silicone raw rubber, silica, extender, plasticizer, mold release agent, aluminum hydroxide, calcium carbonate, platinum compound, azo compound, metal compound, oxidation Properly containing titanium, titanate compounds and organic peroxides to produce silicone rubber compositions, excellent mechanical properties and self-extinguishing of the uncured compound provide excellent storage stability for easy curing process operations over long periods of time. The present invention relates to a thermosetting silicone rubber composition having improved properties.

Silicone rubber has excellent properties in various aspects such as release property, water repellency, cold resistance, heat resistance, weather resistance, and chemical stability. However, today's environmentally friendly requirements for fire safety in electrical and electronic applications require ever more stringent test standards.

In addition, the composition of the thermosetting silicone rubber having self-extinguishment has not used sufficient platinum compound because it does not exhibit sufficient self-extinguishing with silicone alone, which has the effect of raising the silicone rubber price. In order to reduce the amount of platinum compound used, a low-cost flame retardant and an extender were used together, but they did not show satisfactory effects in terms of self-extinguishing and storage stability.

For example, firstly, improper use of platinum compounds and extenders may not exhibit the satisfactory self-extinguishing properties required for electrical and electronic applications.

Secondly, when aerosol silica, extenders and other fillers are used together, crepe hardening occurs more severely over time as the uncured compound.

Accordingly, the present inventors have studied not only to improve the self-extinguishing property of the silicone rubber composition but also to improve mechanical properties including strength, and as a raw material used as a flame retardant based on the environmentally friendly aspect of silicon Or magnesium hydroxide, calcium carbonate, platinum compounds, azo compounds, iron oxide systems (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ), rare earth metal compounds, aerosol titanium oxide, processing aids, titanate compounds, mold release agents, raw rubbers and other The present invention has been completed by developing a thermosetting silicone rubber composition having excellent self-extinguishing (UL94V-0) by using an additive appropriately. In addition, by using an appropriate amount of the processing aid during the uncured compound manufacturing process to facilitate the dispersion of silica, the surface of the silanol groups on the surface of the silica using a titanate compound to form a chemical bond between the silica and the processing aid To generate physical bonds such as hydrogen bonds or van der Waals forces. This solves creep hardening caused by agglomeration of silicas or hydrogen bonding of silica and raw rubber, thereby providing mechanical properties and storage stability.

Accordingly, an object of the present invention is to provide a thermosetting silicone rubber composition having excellent mechanical properties and having storage stability and self-extinguishing property.

The present invention is 100 parts by weight of silicone raw rubber, 1 to 100 parts by weight of silica filler having a specific surface area of 100 to 300 m ² / g and an average particle size of 7 to 16 nanometers, platinum compound (platinum content in organic matter diluted to 5% ) 0.0001 to 1 part by weight, azo compound 0.001 to 1 part by weight, rare earth metal compound (dilution of rare earth metal in organic matter by 5%) 0.01 to 3 parts by weight, iron oxides (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ) 1 to 40 parts by weight, titanium oxide 1 to 20 parts by weight, calcium carbonate 1 to 40 parts by weight, aluminum hydroxide or magnesium hydroxide 1 to 40 parts by weight, extender (diatomaceous earth or quartz powder with a particle size of 100 microns) Storage stability consisting of 1 to 60 parts by weight, 0.1 to 10 parts by weight of a processing aid, 0.001 to 1 parts by weight of an internal release agent composed of an organic fatty acid and a metal salt, 0.01 to 10 parts by weight of a titanate compound, and 0.5 to 3 parts by weight of an organic peroxide. And self-extinguishing Paper is characterized by a heat-curable silicone rubber composition.

Referring to the present invention in more detail as follows.

The present invention is a raw material used as a flame retardant based on the environmentally friendly aspect of silicon as aluminum or magnesium hydroxide, calcium carbonate, platinum compound, azo compound, iron oxide system (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ) The present invention relates to a composition of a thermosetting silicone rubber having improved storage stability and self-extinguishing properties while improving mechanical properties such as tensile and tear strength by appropriately using contents of a rare earth metal compound, aerosol titanium oxide and other additives.

(1) silicone raw rubber (or vinyl gum)

Raw rubber is a linear organopolysiloxane having a molecular weight of hundreds of thousands (preferably 400,000 to 700,000) and a high degree of polymerization (2,000 to 5,000 siloxane units) of viscosity of several million centipoise or more, and may be represented by the following Chemical Formula 1.

R _a SiO _{(4-a) / 2}

In Formula 1, R is an aliphatic saturated hydrocarbon, unsaturated hydrocarbon or aromatic unsaturated hydrocarbon, and a is an integer of 1.90 to 2.05.

In particular, methylvinyl silicone raw rubber containing vinyl groups in the hem end and side chains has a vinyl group content of 0.05 to 0.4 mol%, preferably 0.05 to 0.2 mol%, and has a viscosity of at least 10 million centipoise at 25 ° C.

(2) silica filler

Amorphous silica used as a reinforcing filler is prepared by treating surface-treated wet silica and aerosol silica with organosilanes, organosiloxanes, organosilazanes, and organosilicon compounds, and then using an appropriate amount of processing aid during the uncured compound manufacturing process. After facilitating the dispersion of the silica, the surface of the silanol groups on the surface of the silica is partially treated using a titanate compound to form a chemical bond, and a physical bond such as hydrogen bond or van der Waals force is generated between the silica and the processing aid. . This solves creep hardening caused by agglomeration of silicas or hydrogen bonding of silica and raw rubber, thereby providing mechanical properties and storage stability. Preferably, the surface-treated fumed silica is treated with a processing aid and a titanate compound. These wet silicas and fumed silicas have a specific surface area (BET method) of 100 to 300 m ² / g and silica having an average particle size of 7 to 16 nanometers to reinforce the mechanical properties. 10-100 weight part is used with respect to 100 weight part of said (1) components, Preferably it is 20-60 weight part. If the amount is less than 10 parts by weight, the overall mechanical properties are deteriorated. If the amount is more than 100 parts by weight, dispersion is not easy due to agglomeration of silica and creep hardening occurs.

(3) extender

Diatomaceous earth or quartz powder is used, and the particle size is 100 microns or less, but preferably 30 microns or less.

The extender is a raw material used for the purpose of reducing the unit cost, and has a functional group capable of hydrogen bonding on some surfaces to promote creep hardening due to mutual coagulation.A process aid and a titanate compound are used to prevent mutual coagulation. The storage stability can be improved.

The usage-amount is 1-60 weight part with respect to 100 weight part of said (1) numbers, Preferably it is 20-60 weight part. If the amount is less than 1 part by weight, there is a problem in that it does not play a role of an extender for the purpose of cost reduction, and if it exceeds 60 parts by weight, mechanical properties such as strength are deteriorated.

(4) additives to impart self-extinguishing

(a) platinum compounds

Chloroplatinic acid or chloroplatinic acid compounds containing alcohols, ethers, aldehydes, vinylsilanes and phosphate-based platinum (Pt {P (OC ₆ H ₅ ) ₃ } ₄ , Pt {P (C ₆ H ₅ ) ₃ } ₄ , Pt { P (CH ₃ ) ₃ } ₄ , Pt {P (C ₄ H ₉ ) ₃ } ₄ , Pt {P (OCH ₃ ) ₃ } ₄ , Pt {P (OC ₆ H ₅ ) ₃ } ₃ , Pt {P ( C ₆ H ₅ ) ₃ } ₃ , Pt {P (C ₆ H ₅ ) (C ₂ H ₅ ) ₂ } ₄ , Pt {P (OC ₆ H ₅ ) (OC ₂ H ₅ ) ₂ } ₄ , Pt {P (C ₆ H ₅ ) ₂ (OC ₂ H ₅ )} ₄ , Pt {P (CH ₃ ) ₂ (OC ₄ H ₉ )} ₄ ), etc., in order to give the desired self-extinguishing property by making the dispersion force uniform. It is used by dispersing in organic solvents such as alcohol, isopropyl alcohol, benzene and xylene. Preferably, a platinum compound diluted with 5% platinum in isopropyl alcohol is used. The amount is preferably 0.0001 to 1 part by weight, preferably 0.001 to 0.5 part by weight in 100 parts by weight of (1). If the amount is less than 0.0001 parts by weight, there is a problem that can not be expected to improve the flame retardancy, if it exceeds 1 part by weight, there is a problem that the unit price increases and rather low flame retardancy.

(b) azo compounds

When the platinum compound alone or the azo compound alone is used, a satisfactory effect on self-extinguishing is not imparted, but a synergistic effect can be obtained by using together. Azo compounds used include azobisisobutyronitrile, azobisformamide, triazole compounds, and azodicarbonamides. Excessive use not only affects mechanical properties but also causes foaming during curing. . As for the usage-amount, 0.001-1 weight part is preferable with respect to 100 weight part of said (1) times.

(c) metal compounds

At least one metal or metal compound may be used to improve heat resistance and self-extinguishing, and may be mixed with an organic compound to increase dispersibility.

(c-1) Rare Earth Metal Compound

Cerium octoate, cerium acetate, cerium carbonate and the like are used as the rare earth group metal compound, and cerium octoate is preferable. In particular, it is preferable to dilute with a mineral spritz petroleum solvent so that the rare earth metal becomes 5%. The use amount is 0.01 to 3 parts by weight, preferably 0.05 to 1 parts by weight based on 100 parts by weight of (1). to be. If the amount is less than 0.01 parts by weight, there is a problem in that it does not play a role of a heat resistance improver, and if it exceeds 3 parts by weight, the elongation is increased but mechanical properties such as strength are deteriorated.

(c-2) Iron oxide system

Using _{FeO, Fe 2 O 3, Fe} 3 O 4 , and is used to pour from 1 to 40 parts by weight, preferably 10 to 30 parts by weight per 100 parts by weight of the (1). If the amount is less than 1 part by weight, there is a problem in that it does not act as a heat resistance improver and a pigment, and if it exceeds 40 parts by weight, there is a problem in that the overall mechanical properties are lowered.

(d) calcium carbonate

As an extender and also serves as a flame retardant, carbon dioxide gas is generated as it is burned, and serves to dilute the combustible gas. The particle size is 30 microns or less to prevent mechanical properties from deteriorating. 1-40 weight part with respect to 100 weight part of said (1) times, Preferably 10-30 weight part is used. If the amount is less than 1 part by weight, the effect of the increase and the flame retardance cannot be expected, and if it exceeds 40 parts by weight, the overall mechanical properties are lowered.

(e) aluminum hydroxide or magnesium hydroxide

Water vapor emitted from combustion forms a protective film surrounding the combusted film to exhibit self-extinguishing. 1-40 weight part with respect to 100 weight part of said (1) times, Preferably 10-30 weight part is used. If the amount is less than 1 part by weight, it is difficult to expect a flame retardant effect, and if it exceeds 40 parts by weight, the overall mechanical properties are poor.

(f) titanium oxide (coloring agent)

Aerosol titanium oxide is used as a flame retardant and a colorant, but when used together with other flame retardants, a synergistic effect of increasing the flame retardant effect is obtained.

As the fumed titanium oxide, rutile type or anatase type can be used, and 1 to 20 parts by weight, preferably 2 to 10 parts by weight, based on 100 parts by weight of (1) above. If the amount is less than 1 part by weight, there is a problem in that it does not function as a flame retardant and pigment, and if it exceeds 20 parts by weight, the overall mechanical properties are lowered.

(5) Processing aid

By increasing the dispersibility of the silica filler, it is intended to maintain uniform mechanical properties and to prevent creep hardening. Processing aids are low-viscosity silicone polymers with methyl or phenyl groups in the side chains, hydroxyl groups, alkoxy groups, and amine groups in the sock end, forming hydrogen bonds with silica, resulting in rough cracks on the surface of silica directly bonded to raw rubber. Prevents creep hardening. Preferably it has a hydroxyl group at a sock end, and has a viscosity of 25 centipoise or less at 25 degreeC, and 0.1-10 weight part is used with respect to 100 weight part of said (1) time. If the amount is less than 0.1 parts by weight, it is difficult to disperse the silica, and if it exceeds 10 parts by weight, mechanical properties such as strength are lowered.

(6) release agent

The internal mold release agent is composed of a salt of an organic fatty acid and a metal such as magnesium, calcium, zinc, etc., and 0.001 to 1 part by weight, preferably 0.01 to 0.3 part by weight based on 100 parts by weight of (1). If it is less than 0.001 parts by weight, it is difficult to act as a release agent, and if it exceeds 1 part by weight, mechanical properties such as strength are inferior.

(7) titanate compound

Titanate compounds, such as tetraethyl titanate, tetraisopropyl titanate, tetranormal butyl titanate and tetraethylhexyl titanate, are used as the surface treatment of the surface-treated reinforcing fillers, extenders and other fillers. In the reinforcing filler and other additives used above, a processing aid is used to sufficiently disperse the hydrogen bond between the silica and the processing aid, and then a titanate compound is used to form a chemical bond between the silica and the titanate compound. Treat some silanol groups on the surface. In addition, chemical bonds are generated between the titanate compound and the processing aid to exhibit excellent storage stability by inhibiting agglomeration generated between silica and direct hydrogen bonds generated between silica and raw rubber. If the titanate compound is used alone without using a processing agent which is a low viscosity silicone polymer, the workability is poor, the first plasticity is high, and the storage stability is not improved. 0.01-10 weight part with respect to 100 weight part of said (1) times, Preferably 0.01-5 weight part is used.

In particular, the present invention exhibits an excellent effect of storage stability by using such processing aids and titanate compounds together in the above process.

(8) organic peroxides

As an organic peroxide capable of generating radicals by thermal decomposition, a radical reaction proceeds to the vinyl group and starts to form a bridge. It can also be used in one or mixed form, and it is preferable to use 0.5-3 weight part with respect to 100 weight part of (1). If the amount is less than 0.5 parts by weight, there is a problem in that the uncured portion of the silicone rubber occurs, and if it exceeds 3 parts by weight, the overall mechanical properties are lowered due to over curing. The organic peroxides used may be alkyl or acyl based, preferably 2,5-dimethyl-2,5-t-butylhexane peroxide (45%), 2,4-dichlorobenzoyl peroxide (50 %), Benzoyl peroxide (50%), and the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Examples 1-3 and Comparative Examples 1-10

The following compounds and the contents shown in Table 1 to prepare a silicone compound in the following manner.

To prepare an uncured silicone compound, raw rubber, silica filler, processing aid, and release agent were added to a kneader (compound kneader) and kneaded for 1 hour. The silica filler was all dispersed through the divided addition, and then kneaded for 30 minutes by adding iron oxide, titanium oxide, and an extender, followed by surface treatment for 30 minutes by adding a titanate compound. Thereafter, an azo compound, a platinum compound, a rare earth metal compound, and the remaining additives were added to prepare an uncured silicone compound. At this time, the temperature of kneader was made into the temperature of 100-120 degreeC.

0.5 weight of organic peroxide (2,5-dimethyl-2,5-t-butylhexane peroxide (45%)) based on 100 parts by weight of the raw rubber after plasticizing (softening) the uncured silicone compound in a two-roll mill Part was added and dispersed. Thereafter, the roll spacing of the two-roll mill was adjusted and subjected to a defoaming process, and then pressurized for 10 minutes at 170 ° C. under 100 kgf / cm ² pressure in a molding molding to make a 1 mm thick and 2 mm sheet, and 4 to 6 at 200 ° C. Post-curing in a hot-air circulating oven for a period of time prevented the vulcanization return regression resulting in cleavage of the crosslinked chains due to decomposed organic peroxides.

Example Comparative example One 2 3 One 2 3 4 5 6 7 8 9 10 Silicone raw rubber 100 100 100 100 100 100 100 100 100 100 100 100 100 Silica Fillers ¹ 42 42 42 42 42 42 42 42 42 42 42 42 42 Platinum Compound ² 0.2 0.2 0.2 - 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Azo Compound ³ 0.4 0.4 0.4 0.4 - 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 Processing aid ⁴ (both ends OH-) 1.5 1.5 1.5 - 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 Release Agent ⁵ 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Rare Earth Group ⁶ 0.6 0.6 0.6 0.6 0.6 - 0.6 0.6 0.6 0.6 0.6 0.6 0.6 Iron oxide 23 23 23 - - - - 23 - 23 23 23 23 Titanium oxide 4.6 4.6 4.6 - - - - - 4.6 4.6 4.6 4.6 4.6 Extender ⁷ 20 20 20 36 36 36 36 36 36 36 20 20 20 Calcium carbonate 8 8 8 - - - - - - - 16 - 8 Aluminum hydroxide 8 8 8 - - - - - - - - 16 8 Titanate Compound ⁸ 0.5 One 4 - - - - - - - - - - 1. Silica filler: specific surface area 200 m ² / g, particle size about 12 nm 2. Platinum compound: Pt {P (OC ₆ H ₅ ) ₃ } ₄ (diluted with 5% platinum content) 3. Azo compound: Azobisisobutyronitrile 4. Processing aid: low viscosity silicone polymer having OH group at the sock end (viscosity of 100 cps or less) 5. Release Agent: Calcium Fatty Acid 6. Rare earth metal compounds: cerium octoate (dilute with 5% Ce content) 7. Extender: Quartz powder 8. Titanate Compound: Tetraisopropyl Titanate

Experimental Example

The mechanical properties, storage stability and self-extinguishing properties were measured using the specimens prepared according to the examples and the comparative examples.

<Mechanical Properties>

The mechanical property test was carried out with 2 mm specimens and measured plasticity (William plasticity), hardness, tensile strength, tear strength and elongation according to JIS K6249 and the results are shown in Table 2.

Example Comparative example One 2 3 One 2 3 4 5 6 7 8 9 10 Plasticity 233 245 260 278 213 225 218 225 228 230 222 232 225 Hardness 55 54 51 57 55 56 55 56 56 55 56 56 56 Tensile Strength (Kg / cm ² ) 80 79 70 72 77 79 78 75 76 76 78 77 78 Tear strength (Kg / cm) 23 23 22 22 23 23 23 22 22 22 22 22 22 % Elongation 400 420 500 350 460 430 450 420 400 400 370 380 370

Self-extinguishing

Flame retardant measurements were tested according to UL94V-0 with 1 mm specimens.

Each sample is burned for 10 seconds on a flame to measure the time to extinguish. When the flame of the specimen was turned off and burned again for 10 seconds, the average value of the combustion time measured was shown in Table 3 below (n = 5).

Example Comparative example One 2 3 One 2 3 4 5 6 7 8 9 10 Total burn time (seconds) 7 7 7 - 116 120 89 37 30 19 7 6 8 -: Not completely burned

<Storage stability>

The storage stability according to the change of plasticity was measured by Williams plasticity test for the first time, and after cooling at 25 ℃ and 45% relative humidity for the next period, it was measured for 5 minutes by the plasticity tester.

Example Comparative example One 2 3 One 2 3 4 5 6 7 8 9 10 First plasticity 233 245 260 278 213 225 218 225 228 230 222 232 225 1 day past 275 269 285 355 292 292 300 298 310 308 304 308 303 4 days 298 285 295 389 330 333 338 328 342 345 335 337 329 7 days past 310 290 302 401 344 358 352 344 359 360 352 353 348 10 days past 318 297 308 412 362 362 368 361 373 371 362 362 364

As shown in Tables 2 to 4, it was confirmed that the silicone rubber composition according to the present invention exhibits excellent storage stability while using a processing aid and a titanate compound, without degrading self-extinguishing and mechanical properties.

As described above, the silicone rubber composition according to the present invention has excellent mechanical properties and self-extinguishing properties while exhibiting excellent storage stability for the uncured compound to perform an easy curing process even after a long time.

Claims (2)

100 parts by weight of silicone raw rubber, 1 to 100 parts by weight of silica filler having a specific surface area of 100 to 300 m ² / g and an average particle size of 7 to 16 nanometers, platinum compound (platinum content diluted to 5% in organic matter) 0.0001 to 1 part by weight, azo compound 0.001 to 1 part by weight, rare earth metal compound (having a rare earth metal content of 5% diluted in organic matter) 0.01 to 3 parts by weight, iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ) 1 to 40 parts by weight, titanium oxide 1 to 20 parts by weight, calcium carbonate 1 to 40 parts by weight, aluminum hydroxide or magnesium hydroxide 1 to 40 parts by weight, extender (diatomaceous earth or quartz powder having a particle size of 100 microns or less) 1 to 60 parts by weight, 0.1 to 10 parts by weight of processing aids, 0.001 to 1 parts by weight of internal release agent composed of organic fatty acid and metal salt, 0.01 to 10 parts by weight of titanate compound, and 0.5 to 3 parts by weight of organic peroxide. Stability and magnetic A heat-curable silicone rubber composition having chemical properties. It is obtained by hardening | curing the composition of Claim 1, The silicone rubber characterized by the above-mentioned.