MXPA99001555A - Silicone resin compounds for pirorresistent applications and manufacturing method of mis - Google Patents

Abstract

A polymeric matrix comprising a matrix of a cured methylsilcosquioxane resin and a reinforcing material is described. The claimed compound has a low heat release rate, low smoke yield and low carbon monoxide generation when burned. After burning, the compound has high calcination performance and retains much of its initial tensile strength. The method for making the compound comprises applying a silanol-functional methylsilcosquisoxane resin comprising 70 to 90% mol of units of (CH3) SiO3 / 2) and 10 to 25% mol of units (CH3Si (0H) O2 / 2 ) to a reinforcing material and after that cure the resi

Description

SILICONE RESIN COMPOUNDS FOR PIRORRESISTENT APPLICATIONS AND METHOD OF MANUFACTURING THEM Description of the Invention This invention is concerned with compounds for use in flame retardancy applications. More particularly, it presents polymeric matrix compounds with ethylsilyoisquioxane resins as their matrix. These compounds have low heat release rates, low smoke and minimal CO generation when they are incinerated. Polymeric matrix compounds containing organic resins and reinforcing materials are known in the art for flame retardancy applications. For example, Kim et al. Ther al and Flammability Properties of Poly (p-phenilenebenzobisoxazole), Journal of Fire Sciences, vol. 11, pages 296-307 describes a compound of poly (p-phenylenebenzobisoxazole) (PBO) and carbon fibers. The compound has maximum heat release rates of 0 under a thermal flux of 50 k / m2; 100 under a thermal flow of 75 kW / m2; and 153 under a thermal flow of 100 kW / m2. However, the PBO begins to decompose thermally at a temperature of 660 ° C.

REF .: 29501 Reference of Sastri et al. Flammability characteristics of Phthalonitrile Co-posites, 42nd International SAMPE Symposium pages 1032-1038, 1997 discloses a compound comprising glass-reinforced phtloonitrile polymer. The compound has a maximum heat release rate of 106 kW / m2 when exposed to a thermal flow of 100 kW / m2. However, the calcining performance of the phthalonitrile resins was 65 to 70% in the pyrolysis at 1000 ° C. When the compounds with silicone resins are burned, they usually have a lower heat release rate and lower carbon monoxide and smoke yields than the compounds made with the organic polymers. For example, in Development of Silicone Resins for use in Fabricating Lo Flammability Co posite Materials, Proc. 42nd Int. SAMPE, vol. 42, page 1355, 1997; Chao et al. Discloses silicone resins consisting of the units PhSi03 / 2 and ViMe2SiO? / 2 or Me2SiO? / 2 and ViMe2SiO? / 2 (where Ph represents and hereinafter denotes a phenyl group, Vi represents and henceforth the present denotes a vinyl group and represents Me and henceforth denotes a methyl group). The compounds made from these resins and various fillers have lower smoke production and carbon monoxide yields compared to the compounds made with organic resins. However, these compounds still have unacceptably high heat release rates (up to 150 kW / m2) when exposed to an incident thermal flow of 50 kW / m2. SU-A 0 532 616 discloses a glass fiber reinforced press molding obtained from a polymethylsilyesquioxane, polydimethylmethylphenylsiloxane and a hybrid catalyst.

The molding resists thermal oxidation and has good physico-mechanical properties. U.S. Patent No. 5,552,466 claims a silicone compound with high temperature resistance. The compound is made from a mixture of at least one silsesquioxane polymer with a viscosity of at least 500.00 mPa-s at 25 ° C and at least one component of plioriorganosiloxane with a viscosity of 10 to 1000 mPa -s at 25 ° C. However, there are no known compounds in the art that utilize the unmixed methylsilyl schistoxane resin as the matrix. Accordingly, it is an object of this invention to provide a polymeric matrix composite with methylsilkisquioxane resin that has high calcination performance and retains much of its mechanical strength after burning. Another object of this invention is to provide a method for manufacturing the compound. A polymeric matrix compound with methylsilychioxane resin is described as the matrix. A method for making the compound is also provided. The compound produced is used in structural applications where fire is a concern, such as in interiors of airplanes, oil platforms far from the coast, cars, trains and various infrastructures. The compound has a low maximum heat release rate with low smoke production and low carbon monoxide yields when burned. However, the compound retains much of its tensile strength after high temperature exposures. The polymeric matrix composition of the present invention comprises: (a) a matrix comprising a methylsilcosquioxane resin; and (b) a reinforcing material. The amount of matrix in the compound is usually from 30 to 80, preferably from 40 to 50% by volume. The methylsilcosquioxane resin is obtained by the curing of a silanol-functional methylsilcosesquioxane resin. Silanol-functional methylsilyl squioxane resins are known in the art, for example, WO 97/07156 and 097/07164. These publications describe a silanol-functional methylsilyl squioxane resin and a method for its preparation and curing. The compound comprises the hydrolysis of a methyltrihalosilane of the formula MeSiX3, wherein X represents a halogen atom selected from Cl, F, Br and I; and subjecting the hydrolysis product to a two-phase condensation reaction with water and a compound selected from the group consisting of an organic solvent containing oxygen and an organic solvent containing oxygen mixed with less than 50% by volume of a solvent of hydrocarbon. Silanol-functional methylsilychosquioxane resins are commercially available. For example, Gelest ** 3M02, Wacker ™ MK and Shin Etsu ™ KR220L are suitable for the present invention. The silanol-functional methylsilychisquioxane resin used in this invention comprises units of the formula (CH3) SiO3 / 2 and CH3Si (OH) O2 / 2 - Normally, the resin contains 70 to 90% mol of units of (CH3) Si03 / 2, preferably 75 to 85% mol. The resin contains 10 to 30, preferably 15 to 25% by mole of CH3Si (OH) 02/2 units, wherein the amount of (CH3) Si? 3/2 and CH3Si (OH) O2 / 2 units in the resin is equal to 100% in mol. This resin has a number average molecular weight of 200 to 200,000, preferably 380 to 2,000. The resin is soluble in polar organic solvents. In addition, it does not contain units having organofunctional groups bonded to silicon with more than one carbon atoms, such as phenyl or vinyl group. The silanol-functional methylsilychosquioxane resins cure by the condensation reaction. The reaction can be uncatalyzed or catalyzed by acid, base or neutral catalyst. For example, zinc octolate, tin octoate and titanium butoxide are suitable herein as catalysts. The temperature of the condensation reaction is usually 100 to 250 ° C. The cured methylsilcosquioxane resin comprises (CH3) SiO3 / 2 units and up to 1% mol of CH3Si (OH) 02/2 units and residuals. The matrix of this compound can contain from 0.1 to 50% by volume of optional ingredients. For example, 0.1 to 50% by volume of an additive selected from the group consisting of flame retardants, ultraviolet light protectors, viscosity stabilizers and combinations thereof can be added to the matrix. Suitable flame retardants include silicas, such as powdered or sulfurized silica; layered silicates; Aluminum hydroxide compounds and haze compounds as a flame retardant. Another optional ingredient is a curing agent present in an amount of 0.1 to 20% by volume of the matrix. The hardening agents prevent the compound from becoming brittle when the silanol-functional methylsilcosesquioxane resin cures. The hardening agents are preferably rubber compounds. The amount of reinforcing material (b) in the composite will vary depending on the type and form of reinforcing material. However, the amount of the reinforcing material is usually from 20 to 70, preferably 50 to 65% by volume of the compound. The reinforcing material may be a filler, such as in particulate material exemplified by a silica powder. However, the reinforcing material is preferably a fiber. Suitable fibers include carbon / graphite; boron; quartz; aluminum oxide; organic compounds; ® Glass such as E glass, S glass, S-2 glass or C glass; and fibers of silicon carbide or silicon carbide containing titanium. Commercially available fibers that are suitable for the present invention include; organic fibers, such as KEVLAR MR, fibers containing aluminum oxide, such as NEXTEL M? L fibers of 3M; silicon carbide fibers, such as NICALON from Nippon Carbon; and titanium-containing silicon carbide fibers, such as TYRRANO® from Ube Industries. Carbon and glass fibers are preferred herein because of their low cost. When the reinforcing material is a fiber, is normally present at 20 to 70, preferably 50 to 65% by volume of the compound. The fibers can be prepared or not prepared. When the fibers are sizing, the sizing on the fibers usually consists of a layer of 100 to 200 nm thickness. When glass fibers are used, the size is for example a coupling agent, lubricating agent or antistatic agent. Fiber reinforcement can take several forms. There are continuous or discontinuous or combinations thereof. The continuous-strand wick is used for unidirectional or angular folding composite factories. The continuous-strand wick is also woven into fabric or cloth using different fabrics such as smooth, satin, gauze back, granulum and three-dimensional. Other forms of continuous fiber spares are exemplified by braids, woven fabrics and unidirectional tapes or fabrics. Discontinuous tapes suitable for this invention include ground fibers, metal oxide fibers, staple fibers and cut fiber mats. When the reinforcing material is discontinuous, it is usually added in an amount of 20 to 60, preferably 20 to 30% by volume of the compound. Examples of suitable discontinuous reinforcing materials include ground or cut fibers, such as glass and calcium silicate fibers. The preferred batch reinforcing material is a milled calcium silicate ® fibers (wollastonite; Nyad G Special). A combination of continuous and discontinuous fibers can also be used in the same compound. For example, a woven wick mat is a combination of a woven wick and a mat of cut strands and is appropriate herein. A hybrid comprising different types of fibers in this invention can also be used. For example, layers of different types of reinforcement can be used. In aircraft interiors, the reinforcement material comprises a fiber and a core, such as a NomexMR honeycomb core or a foam core made of polyurethane or polyvinylchloride. The compound may have a coating on its surface such as an acrylate material used to prevent degradation by ultraviolet light (e.g., due to sunlight) of the compound. This coating can also be resistant to abrasion or resistant chemical compounds. This invention is further concerned with a method for manufacturing a compound comprising the steps of: applying a matrix composition comprising a silanol-functional methylsilyl squioxane resin to a reinforcing material; and after that cure the resin. The method for applying the matrix composition to the reinforcing material is not critical. The matrix composition is applied by solvent-free processing or by solvent-assisted processing. Solventless processing is preferred. Solvent-free processing is carried out continuously or non-continuously. Continuous solvent-free processing is carried out by stretching a continuous fiber through a bath containing molten resin. A discontinuous fiber is molded into a sheet by placing the discontinuous fiber over a thin layer of molten resin on a release film and then another layer of release film placed thereon. Then the layers are moved through compression rollers to mix the resin without the fibers. Non-continuous solvent-free processing is exemplified by placing a reinforcement material in a mold and adding the resin to the mold. The resin can be added to an open mold or the resin can be injected into a closed mold. Alternatively, the method for applying the matrix composition to the reinforcing material can be aided by solvents. The silanol-functional methylsilychosquioxane resin can be dissolved in a solvent to form a solution and the solution dissolved in the methods described above. Suitable solvents are exemplified by acetone, methyl ethyl ketone, methyl isobutyl ketone, toluene and isopropyl alcohol. When a solvent is used, the solution contains 40 to 70, preferably 50 to 60% by weight of resin. When solvent-assisted processing is used, the solvent is separated before curing. The solvent is removed by heating the matrix composition at a temperature lower than the temperature required to cure the resin or by allowing the composition to remain or stand at room temperature for up to 24 hours. The amount of the solvent left after the removal step is usually 2 to 3% by weight of the matrix composition. Preferably, the solvent content is reduced to as low a level as possible. If the residual solvent content is greater than 3%, undesirable voids or voids can be formed when the resin cures. The silanol-functional ethylsilkisquioxane resin cures by a condensation reaction. Normally, the compound is cured by heating at a temperature of 200 to 250, preferably 220 to 232 ° C, at a pressure of 0.7 to 1 Mpa. The resin may optionally be post-cured by heating at a temperature of 250 to 275, preferably 250 to 260 ° C. Usually, post-curing is carried out by heating for 5 to 20 hours, preferably 12 to 16 hours. The silanol-functional methylsilychosquioxane resin of the present invention is suitable for use in methods known in the art for making compounds, such as pre-preg the fiber with the resin and subsequently autoclaving the pre-preg.; filament winding; pultrusion; corresponding mold molding; Resin transfer molding and vacuum-assisted resin transfer molding. The compounds prepared according to this invention typically have the following properties when exposed to an incident heat flow of 50 kW / m2: smoke yield (extinction coefficient) of less than 1 μm; CO yield less than 0.02%, preferably less than 0.01% by volume based on the volume of the exhaust gas; and maximum heat release speeds of less than 20, preferably less than 10 kW / pr. After burning, the compounds retain at least 46, preferably at least 78%, of their original tensile strength and have a calcination yield of 98% by weight or more, preferably 99% by weight or more. . The ASTM E 1354 standard was used to test the rates of heat release, carbon monoxide (CO) and smoke release in these examples. In general, the ASTM E 1354 method consists of placing a sample in a sample holder at room temperature. The sample is then burned in ambient air flow while it is subjected to an external heat flux of 50 kW / m2 of a radiantre conical electric heater. The samples are subjected to heat flow for 600 to 1,200 seconds, then the properties of the exhaust gas of the heater are measured. The amount of oxygen consumed is calculated based on the oxygen composition measured by a paramagnetic analyzer and the flow velocity of the outlet gas measured by an orifice meter. The rate of heat release is calculated (kW / m2) based on oxygen consumption over time. The maximum rate of heat release is the highest rate of heat release obtained at the time the sample is exposed to heat flow. The CO yield is obtained by measuring the CO content of the exhaust gas when using a carbon monoxide detector. The maximum CO yield is the highest CO performance measured when the sample is exposed to the heat flux. The smoke yield is expressed as the extinction coefficient (1 / m). The smoke yield is obtained by using a smoke dimming measurement system comprising a helium-neon laser, silicon photodiodes as the main beam and reference detectors and associated electronic components to determine the extinction coefficient. The maximum smoke yield is the highest smoke yield measured over time in which the sample is exposed to heat flow. The system is attached to the heater exhaust duct.

Comparative Example 1 Three silsesquioxane resins were burned in a cone calorimeter according to ASTM E 1354 method. Sample Cl-1 was a phenylsilsesquioxane resin, Gelest ™ 3P01. The Cl-1 sample was cured by heating at 200 ° C for 16 hours. Sample Cl-2 was an uncured phenylsilsesquioxane resin (Gelest MR 3P01). This resin has an average number-average molecular weight of 1161. The Cl-3 sample was an uncured methylsilcosquioxane resin with 81% by mol units ((CH3) SiO3 / 2) and 16% by mol units (CH3Si (OH) O2 / 2) • The resin has a number average molecular weight (Mn) of 3,900. Each sample was ground to a powder and placed in a cone calorimeter under ambient air conditions. Samples were burned by exposure to an external heat flow of 50 kW / m2 for 800 to 1,100 seconds. The oxygen concentration and the velocity of the exhaust gas flow were measured. Then the maximum heat release rate is calculated. The maximum heat release rates for each sample are shown in Table 1.

Example 1 The maximum heat release velocities of four samples of cured methylsilsesquioxane resin were measured according to the method of ASTM E 1354 as in Comparative Example 1 except that the samples were burned for 1,000 seconds. All samples were cured by heating at 200 ° C for 16 to 18 hours. Sample 1-4 was a metilsilsesquioxans cured with units of ((CH3) SÍO3 / 2) and (CH3Si (OH) O2 / 2) • Prior to curing, the resin had 81 mol% of "(CH3) Si03 units and 16% by mole of units of (CH3Si (OH) O2 / 2) and a number average molecular weight (Mn) was 3,900.The content of silanol after curing was less than 1 mol%. 5 consisted of Gelest ™ 3M02. Prior to curing, the resin had 75% mole units ((CH3) SiO3 / :) and 20% mole of (CH3Si (OH) 02 2) and Mn of 2859. Sample 1- 6 consisted of Wacker MR MK and had an MN of 3457 before curing.

Sample 1-7 consisted of Shin EtsuM "R" KR220L and had an MN of 2418 before curing. The maximum heat release rates for each sample are shown in Table 1.

Table 1: maximum heat release rates (kW / m2) for different resins The different cured ethylsilsquioxane resins had comparable heat release rates. However, the uncured methylsilcosquioxane resins and the cured and uncured phenylsilsesquioxane resins had unacceptably high maximum heat release rates.

Example 2 A sample of the compound is prepared by using as a matrix a resin cured with units of ((CHj) SiOj 2) and less than 1% by mole of units of (CH3Si (0H) 0; / 2.

The reinforcing material used consisted of ground calcium silicate fiber (or lastonite, Nyad G ® Special). The compound was prepared by the following method: 5.6 g of the uncured resin and 16 g of the milled fiber were mixed well by an agitator. The uncured resin had 85% mol of units of ((CH3) Si03 2) and 15% mol of units of (CH3Si (OH) 02/2) • The mixture was then cured by hot pressing in a 5 x 5 x 0.63 cm slot per frame at a temperature of 200 ° C for 30 minutes, followed by a post-cure at a temperature of 200 ° C for 15 hours. The sample was incinerated in a cone calorimeter according to the method of ASTM E 1354, under an incident heat flow of 50 μm *. "The maximum rate of heat release was 16.8 k /? Rr. incineration, the compound showed no cracking.

EXAMPLE 3 Two samples of compound were manufactured by using a silanol-functional methylsilychistoxane resin with 81-82% ^ in mol units of ((CH3) SiO3 / and 16-17% in mol of units of (CH3Si (OH) 02 / 2) and a number average molecular weight (Mn) of 3,900 before curing.The first sample, 3-1, was reinforced with glass cloth E style 7781, woven of satin hardness 8 heat treated (glass E is a commercially available electric grade fiber.) The fabric was obtained from Clark Schwebel Company and had the following properties: weight 303 g / m2; thickness of 0.23 m. The glass cloth was not prepared. The second sample, 3-2, was reinforced with silicon carbide fabric of satin fabric, hardness 8, thermally treated ceramic grade. The silicon carbide fabric had a weight of 380 g / m2. The silicon carbide fabric was initially prepared with polyvinylacetate and was thermally treated to remove the sizing prior to manufacturing the compound. Our products were manufactured by the following method: a pre-preg was prepared by immersing the fabric in a solution containing 60% by weight of resin in acetone and drying overnight in corrugated aluminum sheets in a hood fumes to environmental conditions. Sample 3-1 contained 40.5% resin by weight. Sample 3-2 contained 47.9 by weight resin.

Example 4 Sample 3-1 was cut into 24 pieces (22.9 cm x 11.5 cm). Sample 3-2 was cut into 20 pieces (22.9 cm x 12.7 cm). The pieces of each sample were stacked manually to form two folds. Each piece in the fold was arranged in such a way that the wrapping direction was parallel to that of the other pieces. After this, two folds, all the parallel wraps, were placed in the same vacuum bag side by side and cured in an autoclave at 232 ° C and 1 MPa for 6 hours using a combined cycle of deaeration and curing. Purge fabrics were used in the vacuum bag to separate the excess resin. The loosening and curing cycle was as follows: (a) heating at 132 ° C at 1 ° C / min. and maintained for 30 minutes. Pressure increase at 207 kPa. (b) heating at 121 ° C to 1 ° C / min. and maintained for 2 hours. (c) Pressure increase at 1 kPa and then heating at 232 ° C at 1 ° C / min. (d) retention at 1 Mpa and 232 ° C for 6 hours. (e) cooling and pressure reduction. Then the samples were postcured at a temperature of 260 ° C for 16 hours. The sample 4-1 2i it consisted of 24-fold glass / resin composite and was 0.5 cm thick and contained 56% fiber by volume. Sample 4-2 was the 20-fold silicon carbide / resin composite and was 0.71 cm and contained 42% fiber by volume.

Example 5 Each sample of Example 4 was cut into two pieces of 10 cm x 10 cm. The pieces reinforced with glass cloth were designated samples 5-1A and 5-1B. Parts reinforced with silicon carbide fibers were designated 5-2A and 5-2B. Samples 5-1A and 5-2A were weighed and then incinerated or burned in the cone calorimeter according to the method of ASTM E 1354. The compounds were burned by exposure to an external thermal flux of 50 kW / m2 for 600 to 1,200 seconds. The oxygen concentration and the flow velocity of the exhaust gas were measured. The maximum rate of heat release was calculated from the oxygen concentration and the exhaust gas flow velocity. The maximum CO yield and the maximum smoke yield were also measured. The samples were weighed after burning. Calcination performance was calculated based on the weight of the samples before and after burning. Calcination yields and maximum rates of heat release, maximum CO yields and maximum smoke yields are reported in Table 2. Samples 5-1B and 5-2B were not burned.

Table 2: Properties of Burned Compounds Example 6 The mechanical properties of the burned and unburned composite samples of Example 5 were tested. Each one of us was nominally 10 cm long and 1.27 cm wide. Used end tabs, 2.54 cm long, were attached to the samples with epoxy adhesive to result in a measurement length of 5.1 cm. These samples were subjected to stress tests in a warp or warp direction using an Instron test frame with a transverse velocity of 0.04 cm / min. Mechanical wedge action jaws with closed clamping faces were used. The test states are presented in Table 3 Table 3: Traction Resistance of Burned and Unburned Compounds It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (11)

CLAIMS Having described the invention as above, property is claimed as contained in the following:

1. A polymeric matrix compound characterized in that it comprises (a) 30 to 80% by volume of a matrix comprising a methylsilcosquioxane resin consisting essentially of (CH3) SiO3 / 2 units and up to 1% mol of units of (CH3Si ( OH) 02 2), and (b) 20 to 70% by volume of a reinforcing material.

2. The compound according to claim 1, characterized in that the matrix further comprises 0.1 to 50% by volume of an additive selected from the group consisting of ultraviolet light protective flame retardants, viscosity stabilizers and combinations thereof.

3. The compound according to claim 2, characterized in that the additive is a phosphating agent selected from the group consisting of particulate silica, sulfurized silica, layered silicates, aluminum hydroxide and brominated flame retardants.

4. The compound according to claim 1, characterized in that the matrix further comprises 0.1 to 20% by volume of a hardening agent.

5. A method for manufacturing a polymeric matrix composite characterized in that it comprises: i) applying to a reinforcing material, a matrix composition comprising a silanol-functional methylsilyl-squioxane resin comprising 70 to 90% by mol of (CH3) SiO3 2 units and 10 to 30% by mole of units CHjSi (OH) 0 ~, zi wherein the silanol-functional methylsilyl-squioxane resin has a number average molecular weight of 200 to 200,000; wherein the amount of (CH3) SiO2 and CH3Si (OH) 02/2 units in the resin is equal to 100 mol%; wherein the reinforcing material comprises 20 to 70% by volume of the compound; and ii) curing the silanol-functional methylsilychosquioxane resin.

6. The method according to claim 5, characterized in that the compound retains at least 46% of its initial tensile strength after burning -or incineration by exposure to an incident heat flow of 50 kW / m2 for 600 to 1,200 seconds. .

7. The method according to claim 5, characterized in that the composite has at least 98% calcining performance after burning by exposure to an external heat flow of 50 kW / m2 for 600 to 1,200 seconds.

8. The method according to claim 5, characterized in that the silanol-functional methylsilcosesquioxane resin cures during heating at a temperature of 200 to 250 ° C.

9. The method according to claim 8, characterized in that it further comprises curing the silanol-functional ethylsiloquanos at a pressure of 0.7 to 1 mPa.

10. The method according to claim 5, characterized in that it also comprises postcuring the compound by heating at a temperature of 250 to 275 ° C.

11. The method according to claim 10, characterized in that the postcuring of the compound is carried out for 5 to 20 hours.