TW574305B - The composition of elastomeric insulating materials for solid propellant rocket motors - Google Patents

Abstract

Non-asbestos elastomeric insulating materials for solid propellant rocket motors are disclosed. The insulating materials are composed of EPDM rubber polyaramide fiber, liquid EPDM rubber, magnesium hydroxide or aluminum hydroxide, silicon dioxide, halogenated flame retardant compound and zinc hydroxystannate. The char forming organic fiber is used to substitute asbestos added in traditionally insulating materials that in believed to cause serious environmental problems. These fillers in the formulation, which when combined, have a synergistic effect that reduces ablation rate significantly. Also, use of zinc hydroxystannate, instead of Sb2O3, may further reduce both density of the insulator and smoke density and smoke toxicity of the rocket motor exhausted gas.

Description

574305 A7

574305 V. Description of the invention (2) In the atmosphere, it directly causes great health hazards to all relevant staff ’and also has permanent adverse effects on environmental protection. U.S. patents 450 1 84 1 (1 985) and 487843 1 (1989) both use aromatic polyamine fiber (fiber) and inorganic fillers, instead of asbestos fibers, are used in rubber formulations to make flame-retardant film. However, the specific gravity of the flame retardant layer rubber is relatively large, about 1.4gr / cm3 ~ 15gr / cm3, which will reduce the load energy of the rocket engine. U.S. Patent No. 582 1 284 (1998) emphasizes the use of ammonium sulfate and antimony trioxide in the formulation of EPDM compounds containing aromatic polyamide fibers. Synergistic effect can effectively improve the ablation resistance of the flame retardant layer. Although the proportion of the rubber material can be reduced to i.Ugr / cmS, the Sb203 used in the formulation is in the flame retardant layer ablation process. The gas produced in the process is toxic, which is easy to cause harm to the environment. Moreover, the formula (NH4 ^ s04) is a water-soluble inorganic salt. After being made into a flame-retardant layer, it exists in the flame-retardant layer sheet. (NH4) 2S04 on the surface of the rubber material is exposed to the air, and in a humid atmosphere, it is easy to deliquesce due to absorption of moisture, making the flame retardant layer unable to continue to use and must be discarded. US Patent No. 5498649 (1996) The flame retardant layer made of polyamine polymer and maleic anhydride EpDM rubber claims to reduce the proportion of the material, but it does not include any ablation resistance data in the full text, which cannot be judged. Ablation resistance of the produced flame retardant material Basically, the invention of this patent is a thermoplastic plastic material. ^ The paper size is applicable to the Zhongguanjia Standard (CNS) M specification (21GX2 公 7)-Dress --------- Order · — (Please read first Note on the back, please fill out the columns on this page again) 574305 V. Inventive (3) The flame retardant material of (thermal plastic) and the thermosetting rubber material described in the present invention belong to different application mechanisms. [Overview of the invention The object of the present invention is to provide a flame retardant layer for a rocket engine for missiles, which has a low specific gravity, and the effect of the gas generated after ablation is to effectively reduce the smoke toxicity. Another object of the present invention is to provide a rocket engine resistance for missiles. The “burning layer” completely eliminates the use of asbestos fibers that are prone to carcinogenesis. The invention provides a rocket engine flame retardant material with a low specific gravity and a non-toxic rubber material after ablation. The main composition is epdm rubber and Kevlar fiber, and is made of hydroxide Aluminum (A1 (〇H) 3), magnesium hydroxide (Mg (〇H) 2), stannous acid (ZnSn (〇H) 6), stone dioxide, and compounds containing 1¾ prime are burn-resistant Fillers. Aromatic polyamide fibers with organic components are used to replace the asbestos fibers of the traditional rocket flame-retardant layer, which can be completely carbonized after ablation, which can prevent the use of asbestos to pollute the environment. The invention does not use liquid EPDM rubber to adjust the rubber material. The softness makes the finished product have considerable softness. It can be applied to the inner wall of the rocket engine by manual cutting or blow-molding and expansion method, which eliminates the need for ordinary flame-retardant rubber materials containing a large amount of Kevlar fibers ( 301 ^ to 70 〇 0, so that the hardness of the finished product is high, and expensive and precise processing equipment is required. The invention adopts zinc hydroxystannate as a paper standard meaning _ house mark: ^ TCNS) A4 specification ⑵ 574305 A7 --------- B7 V. Description of the invention (4) Rubber material The scorch-resistant filler replaces the traditional antimony trioxide (Sb203), which greatly reduces the toxicity of the gas generated after the flame retardant layer is burned. Other fillers, such as oxychloride, magnesium hydroxide, and absorptive fillers containing _Sui Cai, form a synergistic effect. In addition to reducing the specific gravity of the flame retardant layer, it can effectively improve the flame retardant layer. Money burning resistance. After curing, the flame-retardant layer has the characteristics of low specific gravity, low thermal conductivity, moderate hardness, and excellent ablation resistance. After being ablated to carbon, its gas toxicity is small, and the carbon layer can effectively prevent the propellant from burning. Its temperature is from 2400 to 3 700 ° C, which protects the shell of the rocket engine from melting and ensures flight safety. [Detailed description of the present invention] The rocket flame retardant layer of the present invention uses aromatic polyaramide fiber to replace traditional asbestos fiber, and aluminum hydroxide (Α1 (ΟΗ) 3) or magnesium hydroxide ( Mg (〇H) 2), halogen ablation resistant agent and zinc hydroxystannate (ZnSn (OH) 6) are the ablation resistant fillers of the flame retardant layer material. These solid materials are made of ethylene-propylene ternary rubber rubber, which are processed by agile processing. The reason for using epdm rubber is its low specific gravity, excellent aging resistance, and good softness at low temperatures. Liquid EPDM is added to the formula to adjust the softness of the flame retardant film, which is suitable for the processing conditions of the inner wall of the rocket engine casing. The flame retardant layer of the present invention has a low specific gravity (determined according to G-GTS 1 763 method, 7 > paper size & using China National Standard (CNS) A4 specification (210X297 mm). (Please read the precautions on the back before (Fill in the columns on this page) --------- Order --------- I · 574305 A7 B7 V. Description of the invention (5) 1.140gr / cm3 ~ 1.21〇gr / cm3), hardness Moderate (Shore A 82 ± 7), low thermal conductivity (measured according to ASTM D-581, $ 0.245 Kcal / mh ° C) and excellent ablation resistance (measured according to aSTM E-285, $ 0 · 0 8 5 mm / sec), good aging resistance, good softness at low temperature (-50 ° C), low toxicity after ablation, no environmental concerns, and fully meet the material requirements of the flame retardant layer of the rocket engine of the new generation missile. The flame retardant layer of the present invention uses EPDM rubber as a basic rubber material and sulfur as a rubber curing agent, so that it can be adapted to the limitation of heating and curing of the flame retardant layer paste processing equipment below 1 300 t. The sulfur used in the present invention is colloidal sulfur, and the amount is from 0.001 to 5 phr of the EPDM rubber weight in the formula, and 0.5 to 2.5 phr is the most suitable. The present invention also uses a maturation accelerator N-tert-butyl-2-benzothiazole sulfenamide, the amount of which is from 0.01 phr to 3 phr of EPDM rubber weight, and preferably from 0.05 phr to 2phr, and 4,4, dithiodimorpholine (4,4, dithio dimorpholine), the amount of which is from 0 to 1phr to 3 phr of EPDM rubber weight, of which from 0 to 0 5phr to 2 phr. The aromatic polyamide fiber used in the present invention is preferably in the form of a pulp, and the ratio of its length to the diameter is about $ ⑽. The physical properties of suitable aromatic polyamide fibers are as follows: ^ --------- Order -------- (Please read the precautions on the back before filling in the blocks on this page) 8 574305 A7 B7 V. Description of the invention (6)

Table 1. Physical properties of aromatic polyamide fibers. Tensile strength (kg / cm2) 30,000 ~ 40,000 Tensile strength (kg / cm2) 7.6 × 108 ～ lxlO10 Elongation (%) 3 ~ 5 Density (gm / cm3) 1.4 ～ 1_5 Fiber diameter (// m) 10 ~ 14 Decomposition temperature (° c) 400 ~ 600 Thermal expansion coefficient-2x10V ° C The length of pulp-like aromatic polyamide fiber used in the present invention should be 0.5 to 4 1 mm to 3 mm is the most suitable, and the amount used is 10 phr to 100 phr, and 15 phr to 7 5 phr is the best. Liquid EPDM rubber is used in the formulation of the flame retardant layer to adjust the softness of the raw film of the flame retardant layer, and it is used as the adhesion of various solid fillers and aromatic polyamide fibers to solid EPDM rubber, and mixed evenly. The basic chemical composition of liquid EPDM rubber and solid EpdM rubber is the same, but the molecular weights are different and they are completely compatible. Liquid EPDM rubber is used in the formulation of the flame retardant layer. As a plasticizer in the flame retardant raw rubber, it has the effect of adjusting the softness of the raw film. When the flame retardant layer is heated and matures, the liquid EPDM rubber and the solid EPDM are simultaneously cured by sulfur and sulfur. The sulphur-containing accelerator catalyzes the co-aging reaction. Therefore, after maturation of the rubber flame retarding layer using liquid EPDM rubber as a plasticizer, the flame retardant layer does not cause plasticizer migration during missile storage. Liquid EPDM rubber exists in the flame retardant rubber compound and has the effect of tack, which can improve the self-adhesion between the flame retardant raw film layer and the layer. If used in combination with a tackifier, the viscosity will be increased. The effect is better. The present invention uses a synthetic polyterpene resin as a tackifier. It is a standard (CNS) A4 specification (21GX2997)-'~~ ---- (Please read the precautions on the back before filling in the columns on this page). ---- Order -------- Line-. 5. Description of the invention (7) The amount is from 1 to 10 phr, preferably 4 to 8 phr, which is the weight of the EPDM rubber. Ablation resistance, the present invention uses aluminum hydroxide (A1 (0H) 3), magnesium hydroxide (Mg (0H) 2), stone dioxide (Si02), element compounds and hydroxystannite (ZnSn ( 〇H) 6) is an ablation-resistant filler of the rubber material formula, in which if A1 (〇H) 3 or Mg (〇H) 2 is used alone ', it will be decomposed separately after the heat is burned to release water molecules, which will be released. The water molecules produced can effectively cool the material surface layer of the burned flame retardant layer, extend the ablation resistance time of the flame retardant layer, and improve its ablation resistance. In the formulation of the flame retardant layer, stannous acid and aluminum hydroxide, hydroxide hydroxide, and compounds containing _ are used as fillers, which can form a synergistic effect, which greatly improves the burn resistance when each filler is used alone. Eclipse capability. At the same time, the gas generated by the ablation decomposition of zinc hydroxystannate is non-toxic, far better than the traditional antimony trioxide (Sb203), and has a lower specific gravity (3.3gr / cm3 compared to 5.6gr / cm3) , Can effectively reduce the proportion of the flame retardant layer, that is, reduce the dead weight of the engine and increase the missile range. The properties of tribasic acid are shown in the following table: Table II. Properties of hydroxystannoic acid Chemical structure ZnSn (OH) 6 Appearance White powder Analytical value ~ 41% Sn; ~ 23% Zn Specific gravity 3.3gr / cm3 Decomposition temperature> 180 ° C Oral Toxicity (LD5G, rats) > 5gr / kg 10 This paper size is applicable to China National Standard (CNS) A4 (210X297 mm) (Please read the precautions on the back before filling in the columns on this page) Pack- ------- Order ---- Line! 574305 Feeding order: Rubber plastic scouring, aromatic polyamide fiber, fire-resistant agent, inorganic filler, organic filler, sulfur and accelerator A7 B7. 5. Description of the invention (9) stannin and 188 grams (35phr) 1, 2, 3 , 4,7,8,9,10,13,13,14, 14-Twelve Gas-1,4,4 &, 5,6,6 &, 7,10,1 (^, 11,12,123 -Dodecyl-1,4,7,10-difluorenyldiphenyl (ae) cyclooctene (commonly known as Dechlorane

Plus), mix thoroughly for 30 seconds, then add 5.4 grams (1phr) of substituted diphenol antioxidant and 32.3 grams (6phr) of synthetic polyterpene resin tackifier and 53.8 grams (10phr) of vaporized wax, mix thoroughly for 30 seconds After 2 minutes, add 2 69 g (5ph0 oxidation mixture and knead for 20 seconds. After removing the rubber material, add 10.7g (2phr) sulfur and 5.38g (lph〇4,4, ~ disulfide) to the two-roller machine. The furoline vulcanization accelerator is thoroughly mixed for 2 minutes. In this way, the rubber flame-retardant layer rubber material with excellent properties of the present invention can be obtained. Examples 2 to 5 The operation steps of Example 1 are repeated. The mixing procedure is generally referred to Table 2 but The composition is changed to the formulation examples 2 to 5 as shown in Table 4. Also, the rubber flame retardant layer composition with different composition ratios of the present invention is obtained. Table II · Mixing operation procedures of Examples 2 to 5 Seconds) 20 40 30 30 30 120 (Please read the notes on the back before filling in this page.) •-· * Install --------- Order ---- Line! 574305 A7 B7 V. Invention Explanation (10) Table 4 lists specific formulations of the flame retardant layers of Examples 2 to 5 of the present invention. Table 4. Examples 2 to 5 of the flame retardant layer of the present invention Examination formula example Formula ingredients 2 3 4 5 EPDM rubber a 60 60 60 60 Liquid EPDM rubber b 40 40 40 40 Zinc oxide 5 5 5 5 Stearic acid 1 1 1 1 Anti-aging agent e 1 1 1 1 Aromatic polyfluorene Amine fiber d30 30 30 30 Aluminum hydroxide 20 20 20 Magnesium hydroxide 1 — 20 Silicon dioxide e 20 20 20 20 Halogen flame retardant f 35 35 35 35 Zinc hydroxystannate g 1 5 5 Tackifier h 6 6 6 6 Antimony trioxide 10 10 Wax chloride 10 10 10 10

a. Sumitomo 505A b. Trilene 65 c. Naugard 445 d. Kevlar pulp

e. Hi-Sie 233T f. Dechloran Plus 25 g. Zinc Hgdroxylstannate h. Wingtack 95 Test Examples 1 to 5 The finished products of Examples 1 to 5 of the above examples were processed with a rubber calender to calender the tablets, and polyethylene The film is an isolation substrate, which is collected in rolls, which can be transported and stored for future use, and can also be cut and pasted. After expansion and curing, it can be made into a flame retardant layer for rockets. In the formulations of Examples 1 to 5, the relevant physical properties of the finished product of the flame retardant layer are shown in Table 13. The paper size is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) (Please read the precautions on the back before filling in the columns on this page) -Packing --------- Order ----- 丨 1 ,, 574305 A7 B7 V. Description of the invention (11) V, in which the aromatic polyamide fiber in the rubber material is rolled when the sheet is rolled out The shear force of the calender roller acts in the forward direction of the sheet. Therefore, the flame retardant material of the sheet after the sheet has completely different physical properties related to the parallel and vertical directions of the fiber. Very obvious. According to the physical property data in Table 5, the film of the flame-retardant layer material of the present invention is soft and suitable for stacking the flame-retardant layer on a rubber-made airbag by an inflatable mandrel technique, and pressurizing from the inside of the airbag. The swelling causes the flame retardant layer to closely adhere to the inner wall of the missile shell. At the same time, since the flame retardant layer has sufficient strength, it can be suitable for different flame retardant layer processing techniques such as manual internal sticking method, tape sticking method or pellet winding method. (Please read the precautions on the back before filling in this page.) Table 5 · Physical properties of the flame retardant layer of Examples 1 to 5 of the present invention 1 2 3 4 5 Tensile strength of raw rubber properties (kg / cm2 ) Parallel 9.92 11.59 13.28 16.13 16.37 Vertical 4.29 6.02 2.38 5.76 13.72 Elongation (%) Parallel 23.14 9.70 8.75 17.48 9.22 Vertical 21.89 24.23 31.41 26.83 16.58 Properties of curing properties 120 ° C / 2hr / 3kg / cm ") Tensile strength ( kg / cm2) Parallel 143.99 124.14 137.09 106.68 85.29 Vertical 125.55 108.16 68.95 112.21 50.99 Elongation (%) Parallel 20.98 21.77 20.11 24.51 24.86 Vertical 20.40 22.72 51.06 25.13 45.74 Hardness (Shore A) 86 87 88 88 84 Specific gravity (gr / cm3) 1. 1.18 1.19 1.23 1.18 Thermal conductivity 0.227 0.231 0.237 0.243 0.238 (Kcal / mh ° C) 14 This paper size applies to China National Standard (CNS) A4 (210X297 mm) Order -------- 574305 A7 B7 V. Description of the invention (12) Test examples 6 to 10 The finished products of the above examples 1 to 5 were pressed into a flat mold with an oil press at 120 C, 2 hours, and 3 kg / cm2, and then pressed to a thickness of 6 bandits. Cooked film 'According to ASTM E_285 standard test method, the flame of acetylene and oxygen (0xygen) mixed gas (acetylene flow rate 1.7ft3 / min, oxygen flow rate 2.4ft3 / min) is vertically upward from 2 5.4mm below the sample Erosion, the ability of the flame retardant film to withstand flame erosion was measured until the sample burned through. The results are shown in Table 6. --- Feng Liu · The burning resistance of the non-asbestos flame retardant layer of the EPDM rubber of the present invention, the ablation resistance and the rBq solution are divided into ί ec) (Please read the precautions on the back before filling in the columns on this page) Pack 2 3 4 5

2 7 8 6 7 6 8 3 5 5 2.0.2.1.2. 11 11 lx 1X 9 2 17 0 7 9 8 8 8 ο ο ο 0.0 0.0 · 0 · 0 · 0 · The invented rubber flame retardant layer can exhibit excellent ablation resistance, has characteristics of sintering into carbon, and good heat insulation, and can be used as a heat insulation material for the inner wall of the rocket engine shell used for tactical missiles. Test example 1 1 to 1 3 Among the above-mentioned examples 1 to 5, the formulas 1, 2 and 3 were selected for the smoke concentration measurement. The method was based on the method specified in ASTM E_662, and the smoke generated when the test sample was burned with the NBS Smoke Box amount. Density, with __15_____ This paper size applies Chinese National Standard (CNS) A4 (210X297mm) > * f ----- Order i ------ '0 line! 574305 A7 B7 V. Description of the invention (13) Compare the difference in smoke between the samples. Table VII. Determination of the smoke concentration of the samples of Examples 1, 2 and 3 of the present invention Example 1 2 3 Formulation content (phr) ZHS Sb2 03 ai (oh) 3 5 20 20 10 20 Smoke volume (Dm) * 167 199 219 * Flame burning, unit-free test results show that using a certain amount of ai (oh) 3 in each formulation, the smoke suppressing effect of hydroxystannin is far longer than the results of S b 2 〇 3 and without these fillers Is excellent. Test Example 1 4 to 16 Among the formulations of Examples 1 to 5 above, formulas 1, 2 and 3 were selected for the smoke toxicity determination. The method was based on the method specified in ASTM E-1 687, and the test samples were burned with the NIBS Combustion Toxicity Apparatus. The toxicity of smoke is generated to compare the toxicity difference of smoke emitted when each sample is burnt. _Table 8 · Smoke toxicity determination of the samples of Examples 1, 2 and 3 of the present invention — Example 1 2 3 Formulation content (phr) ZHS 5 — —

Sb2〇3 — — 10

Al (OH) 3 20 20 20 16 This paper size applies to Chinese National Standard (CNS) A4 (210X297 mm) " (Please read the precautions on the back before filling in the columns on this page). ------ --- Order -------- 丨% 574305 A7 B7 V. Description of the invention (14) The test results show that a certain amount of A1 (〇H) 3 is used in each formulation of the flame-retardant layer of the present invention. Compared with the toxicity of the smoke after ablation, the effect of using stannous acid to suppress the smoke is far superior to that of Sb203 and the absence of these fillers. It should be noted that the above is merely an embodiment, and is not limited to the embodiment. For example, those who do not depart from the basic structure of the present invention should be the scope of rights claimed by the patent, and the scope of the patent application shall prevail. x (Please read the notes on the back before filling in the columns on this page)

• · Γ * m ^^ 1 —Hi n · ϋ —ϋ tl · I 1 ^ 1 n i ^ i ^^ 1 ai i ^ i 17

Claims (1)

574305 one one 1; j] two 丨 factory one ------- Dibu 'know ^ ;, shouting pain; 丨 f ling said edge reverse page six, the scope of patent application 1. a rocket flame retardant rubber composition, It mainly includes: (a) 55 phr to 80 phr solid methyl ethyl ternary rubber (EpDM rubber); (b) 20 phr to 45 phr liquid methyl ethyl ternary rubber; (c) 5 phr to 50 phr aromatic polyfluorene Amine fibers; (d) sulfur and vulcanization accelerators in the range of 1 to 5 phr, wherein the vulcanization accelerator is selected from the group consisting of 4,4′-dimorphine sigmaine and n-third butyl-2-benzothiazolyl At least one of the sulfonamide groups; and (e) hydroxystannin from 1 to 20 phr. 2. The composition of item 1 in the scope of patent application, further comprising: (〇2 01) 111 'to 50? 111' selected from the group consisting of 1,2,3,4,7,8,9,10,13 , 13, 14, 14—twelve gas-i, 4, 4a, 5, 6, 6a, 7, 10, 10a, ii, 12, 12a—dodecahydro-1, 4, 7, 1 —Dimethyldiphenyl 0 ′)% organic halide of the octene group and at least one of the ten burn-up filler groups. 3. The composition according to item 2 of the scope of patent application, which further includes: (g) 20phr to 120phr inorganic filler, the inorganic filler is selected from at least one selected from the group consisting of silicon dioxide, aluminum hydroxide and magnesium hydroxide. By. 4. If the composition in the second item of the patent application scope, it further comprises 4 to 8 phr of polyboxene resin as a tackifier. 5. The composition according to item 2 of the patent application scope, which contains 30 to 40 phr of the organic function ablation-resistant filler. _ 18 This paper size is applicable to the Chinese Family Standard (CNS) A4 specification (21〇297297) ------ -I installed · ------- ^-order, ------- --line! (Please read the precautions on the back before filling in the blocks on this page.) 574305 VI A8 B8 C8 D8 Patent Application Scope 6. If the composition of the patent application item 1 contains 10-40phr of the aromatic polyamide fiber. 7. The composition according to item 6 of the patent application scope, which contains 1-10 phr of the zinc hydroxystannate. (Please read the precautions on the back before filling out the columns on this page.) Install --------- Order -------- ^ " Line | 19 This paper size applies to China National Standards (CNS) A4 specifications (210X297 mm)