Composite material for making sealing systems and method therefor

Abstract

 A method for making a composite material comprising a combination of biosoluble ceramics fibers and mineral fillers, for making sealing systems, comprising the steps of chemically pre-processing biosoluble ceramics fibers in an aqueous solution with vinyltriethoxysilane and mineral fillers with bis(triethoxysilyl-propyl)polysulfide or vice-versa and slowly mixing the processed biosoluble ceramics fibers and mineral fillers with an elastomeric solution as a process aid.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a composite material for making sealing systems and a method therefor.

[0002] In the thermal insulation field the use of ceramics fibers is well known owing to their optimum thermal and chemical resistance.

[0003] However, the use of conventional ceramics fibers is limited because of their suspected toxicity.

[0004] For the above reasons, biosoluble ceramics fibers being characterized as untoxic system have been developed.

[0005] In the present invention biosoluble ceramics fibers which will be hereinbelow referred to as "A" composite are exclusively used.

[0006] It is also known that mineral fillers have a sheet like microstructure and tend to overlap thereby providing structures which could be called "paling or palisade" constructions.

[0007] The above composite materials, which will be hereinbelow referred to as "B composites", comprise: muscovite and phlogophite mica, bentonite, montmorilonite, laponite, hydrotalcite, kaolin, lamellar structure silicates, phyllosilicates, thermally, ultrasonically and/or chemically foamed phlogophite mica.

[0008] Said B composites may also be used in any combinations and rates.

[0009] The A composite may be used as a fibrous reinforcement agent for composite materials, owing to its good mechanical and chemical properties; however, in the sealing or gasket system field it cannot be used per se, because of its poor sealing capability.

[0010] In turn, the B composites may be used in the sealing system field, since they provide good sealing capabilities, but cannot be used per se, because of their poor mechanical characteristics.

[0011] Moreover, a simple composite A and B mixture cannot be used since the individual composites thereof are incompatible with one another and do not form blended systems of continuous and homogeneous properties.

SUMMARY OF THE INVENTION

[0012] Thus, the aim of the present invention is to provide a combined composite material the A composite of which is chemically bound to the B composite, through an organosilane based chemical process.

[0013] Moreover, the end product appears as consisting of an uneven weave of biosoluble ceramics fibers operating as structural support for inorganic compounds having a layered lamellar structure.

[0014] The invention also relates to a method for making plates, films and sheets even coupled to other materials such as metal and non-metal fiber fabrics, smooth, perforated and/or diamond shaped metal laminates, which will be hereinbelow referred to as "supports".

[0015] The above aim and objects, as well as yet other objects which will become more apparent hereinafter, are achieved by a method for making a composite material, as well as the related composite material consisting of biosoluble ceramics fibers and mineral fillers, particularly for making sealing or tightness systems.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Further characteristics and advantages of the present invention will become more apparent hereinafter from the following disclosure of a preferred, though not exclusive, embodiment of the invention.

[0017] The method according to the present invention comprises the following method steps:

A step 1) of chemically pre-processing biosoluble ceramics fibers (A composite) in an aqueous solution with vinyltriethoxysilane and mineral fillers (B composite) with bis(triethoxysilylpropyl)polysulfide or vice-versa.

[0018] The B composite may comprise muscovite and phlogophite mica, bentonite, montmorilonite, laponite, hydrotalcite, kaolin, lamellar structure silicates, phyllosilicates, thermally, ultrasonically and/or chemically foamed phlogophite mica.

[0019] A step 2) of preferably slowly mixing the already processed A and B composites, with an elastomeric material solution as a process aid.

[0020] A step 3) of forming a plate and/or a coupling with the supports.

[0021] A step 4) of finally thermally curing the material from step 3).

[0022] A step 5) of preferably hot coating the material surface by an anti-adhering protective film having a thickness larger than 5 µm, based on high temperature silica and PET, by a vacuum heated calender.

[0023] In the step 1) the A composite is processed with vinyltriethoxysilane in an aqueous or organic solution and with a concentration from 0.1 to 30% by weight, in which vinyltriethoxysilane is present starting from a rate from 0.5% up to 30% by weight, based on the A composite.

[0024] The B composite is processed with bis(triethoxy-silylpropyl)polysulfide in an aqueous or organic solution at a concentration from 0.1 to 60% by weight, wherein said bis(triethoxysilylpropyl)polysulfide is present from a rate of 0.5% to 30% by weight based on the B composite.

[0025] The above processes are carried out separately for the A and B composites, in a closed vessel and under slow stirring, at a temperature from 25°C to 80°C for 24 hours.

[0026] In this first step, the following chemical reaction occurs:

a) a vinyltrietoxysilane hydrolysis and an ethanol evolution

a bis(triethoxysilylpropyl)polysulfide hydrolysis and an ethanol evolution

b) a condensation reaction of the A composite surface hydroxyls and the vinyltrihydroxysilane hydroxyls

[0027] A condensation reaction between the B composite surface hydroxyls and the bis(trihydroxysilylpropyl)polysulfide hydroxyls

[0028] In said step 2) the A and B composites, as preprocessed in said step 1), are mixed with a solution polymer based binding system such as: NBR, chloroprene, SBR, polyisoprene, polybutadiene, butyl, silicone, fluorurated and urethane rubbers.

[0029] Preferably, the following solvents are herein used: toluene, xylene, dimethylketone methylethylketone, saturated C6-C10 linear and cyclic hydrocarbons.

[0030] The solutions contain the polymer in a rate up to 30% by weight.

[0031] The preferred mixing system comprises a "Z branch" or a planetary system.

[0032] The mixing time is preferably from 30 to 45 minutes, depending on the desired end viscosity.

[0033] The A composite may be introduced into the mixture in a rate up to 80% by weight.

[0034] The B composite may be introduced into the mixture in a rate up to 90% by weight.

[0035] This difference will depend on the required technical performance.

[0036] The process aid is introduced into the mixture in a rate up to 7% by weight.

[0037] As the A composite amount increases, a viscous creeping reduction in the gasket made from the plate is detected.

[0038] As the B composite amount increases, a decrease of the fluid loss (leakage) rate through the gasket made from the plate is detected.

[0039] In said step 3) the mixture of step 2) may be processed through calendaring or spreading and optionally coupled to a support, if either plates or continuous films are to be achieved.

[0040] In said step 4), the half-finished articles of step 3) are subjected to a thermal cycle up to 250°C depending on the used process aid polymer and solvent, with a heating rate from 1°C/minute.

[0041] The main reaction herein occurring are:

a) a breaking of the polysulfide residue;

b) a cross-linking reaction.

Examples:

Formulation 1

[0042] 

1) Treating 10 kg of biosoluble fiber with 100 g vinyltriethoxysilane in ethanol at 5%, in a mixer for 12-24 hours, while processing 5 kg muscovite mica, with a particle size from 10 to 50 µm and 1 kg foamed phlogophite mica with a particle size from 200 to 500 µm, with 150 g bis(triethoxysilylpropyl)polysulfide in ethanol at 5% in a mixer for 12-24 hours.

2) Drying the processed A and B composites, in a dryer, with a solvent abatement system for 4 hours at 50°C, in steel basins or vats.

3) Mixing the dried A and B composites with 200 g NBR in a toluene solution at 20% and 1.8 kg deionized water, in a planetary mixer for a minimum time of 20 minutes.

4) Depositing the mixture of step 3) on a stainless steel 321 grid metal support, by a calendaring process.

5) Thermally processing in an oven at 180°C for 180 minutes.

6) Coating the sheet element by a PET and silica protective film with a thickness larger than 5 µm.

[0043] It has been found that the invention fully achieves the intended aim and objects.

[0044] In fact, the invention has provided a method of making a composite material, particularly suitable for making sealing systems, comprising a combination of biosoluble ceramics fibers and mineral filers.

[0045] The method according to the present invention provides an end product consisting of an uneven weave of biosoluble ceramics fibers, operating as a structural support for inorganic composites having a lamellar layered structure.

[0046] The sealing system composite material according to the present invention comprises a biosoluble fiber matrix having a thermal resistance up to 1000°C, with lamellar layered structure inorganic composites having a particle size from 1 µm.

[0047] The use of organosilanes in the subject method provides a mechanically continuous phase between the biosoluble fiber structure and the lamellar structure inorganic composites.

[0048] Moreover, the method according to the present invention provides semifinished sheets, plates, films or sheet elements coupled to other materials such as metal and non-metal fiber fabrics, smooth, perforated and/or diamond shaped metal laminates and other articles.

[0049] The composite material made by the present invention may be used at high temperatures up to 1,000°C, even in the presence of strongly oxidizing agents.

[0050] Moreover, the inventive composite material may also be used for high temperature sealing systems.

[0051] Furthermore, the inventive composite material may also be used as a protective film coated on surfaces of the sheet elements.

Claims

1. A method for making a composite material comprising a combination of biosoluble ceramics fibers and mineral fillers, for making sealing systems, characterized in that said method comprises the steps of:

chemically pre-processing biosoluble ceramics fibers in an aqueous solution with vinyltriethoxysilane and mineral fillers with bis(triethoxysilylpropyl)-polysulfide or vice versa;

slowly mixing the processed biosoluble ceramics fibers and mineral fillers with an elastomeric solution as a process aid.

2. A method, according to claim 1, characterized in that said mineral fillers comprise one or more of the following elements: mica, muscovite and phlogophite, bentonite, montmorilonite, laponite, hydrotalcite, kaolin, lamellar structure silicates, phyllosilicates, thermally, ultrasonically and/or chemically foamed phlogophite mica.

3. A method, according to claim 1, characterized in that said method comprises a further step of forming a plate and/or a laminate structure with the supports.

4. A method, according to claim 1, characterized in that said method comprises a further thermally curing end step.

5. A method, according to claim 1, characterized in that said method comprises a further step of hot coating a surface with an anti-adhering protective film having a thickness larger than 5µm, based on high temperature silica and PET, by a vacuum heated calendaring device.

6. A method, according to claim 1, characterized in that said method comprises processing the biosoluble ceramics fibers by vinyltriethoxysilane in an aqueous or organic solution at a concentration from 0.1 to 30% by weight, said vinyltriethoxysilane being present starting from an amount from 0.5% to 30% by weight based on the biosoluble ceramics fibers, and processing the mineral fillers by bis(triethoxysilyl-propyl)polysulfide in an aqueous or organic solution at a concentration from 0.1 to 60% by weight, said bis(triethoxysilylpropyl)polysulfide being present in an amount from 0.5% to 30% by weight with respect to said mineral fillers, said processing being carried out separately in a closed processing vessel and under a slow stirring at a temperature from 25°C to 80°C for 24 hours.

7. A method, according to claim 1, characterized in that said binding system is used with a process aid based on a solution polymer such as: NBR, chloroprene, SBR, polyisoprene, polybutadiene, butyl, silicone, fluorurated and urethane rubbers.

8. A method, according to claim 1, characterized in that in said method solvents selected from toluene, xylene, dimethylketone, methylethylketone, saturated C6-C10 linear and cyclic hydrocarbons are used.

9. A composite material for making sealing systems, characterized in that said composite material comprises a matrix consisting of an uneven weave of biosoluble fibers, operating as a support for lamellar layered structure inorganic composites.

10. A composite material, according to claim 9, characterized in that said biosoluble fiber matrix has a thermal resistance up to 1,000°C and said lamellar layered structure inorganic composites have a particle size from 1 µm.