CN1220578C - Method of making multilayer article having fluoroplastic layer and elastomer layer - Google Patents

Abstract

A method for enhancing the bond strength between a VDF-containing fluoroplastic layer and an elastomer layer of a multi-layer article. A VDF-containing fluoroplastic composition is applied to the surface of a precursor article that includes a curable elastomer layer to form a fluoroplastic layer. Prior to application of the fluoroplastic composition, the curable elastomer layer is thermally insulated to prevent it from undergoing substantial heating. Following application, the fluoroplastic layer is heated and the curable elastomer layer is cured (e.g., thermally cured). Preferably, the elastomer cure occurs separately from and subsequent to heating the fluoroplastic layer. The combination of thermally insulating the curable elastomer layer prior to application of the fluoroplastic composition and heating the fluoroplastic layer following application of the fluoroplastic composition results in formation of a strong bond between the fluoroplastic and elastomer layers upon cure.

Description

Method of making multilayer article having fluoroplastic layer and elastomer layer

technical field

The present invention relates to the preparation of multilayer articles having a fluoroplastic layer and an elastomeric layer.

Background of the invention

Fluoropolymers are an industrially useful class of materials. Fluoropolymers include, for example, crosslinked fluoroelastomers and semicrystalline or glassy fluoroplastics. Fluoroplastics generally have high thermal stability and are especially useful at high temperatures. They are extremely tough and flexible even at very low temperatures. Many of these fluoroplastics are almost completely insoluble in many solvents and are often chemical resistant. Some have extremely low dielectric loss and high dielectric strength, and can be uniquely non-adhesive and low-friction. See, for example, F.W. Billmeyer, Textbook of Polymer Science, 3d ed., pp. 398-403, John Wiley & Sons, New York (1984).

Fluoroelastomers, especially copolymers of vinylidene fluoride and other ethylenically unsaturated halogenated monomers such as hexafluoropropylene, find particular application in high temperature applications such as seals, gaskets and linings. See, for example, RA Brullo, "Fluoroelastomer Rubber for Vehicles," Automotive Elastomer & Design, June 1985; "Prospects for Applications of Fluoroelastomers for Vehicle Sealing," Materials Engineering, October 1988, and WMGrootaert et al., " Fluorocarbon Elastomers"; Kirk-Othmer, Encyclopedia of Chemical Technology, vol. 8, pp. 990-1005 (4 ^th ed., John Wiley & Sons, 1993).

Multilayer structures containing fluoropolymers have a wide range of industrial applications. For example, use of such structures can be found in fuel hoses and related containers and hoses or gaskets in the chemical processing field. Increased attention to evaporative fuel standards has led to increased requirements for fuel system components, requiring improved barrier properties to prevent fuel or fuel vapor from vehicular components such as filler pipes, fuel supply pipes, fuel tanks and other engine fuel or fuel vapor recovery systems Part penetration is minimal. Various types of tubes have been proposed to address these concerns.

Depending on the use of the final article, the adhesion between the layers of the multilayer article should meet various performance criteria. However, when one of the layers is a fluoropolymer, it is often difficult to form a high bond strength. Various methods have been proposed to deal with this problem. One approach is to use an adhesive or adhesion promoting layer between the fluoropolymer layer and the second polymer layer. Surface treatments of the fluoropolymer layer including solvent etching and corona discharge can also be used to improve adhesion. When the fluoropolymer contains copolymerized units formed from vinylidene fluoride, the fluoropolymer has been placed in a dehydrofluorination reagent such as a base, and a polyamine reagent can also be applied to the surface of the fluoropolymer or added to the fluorine-containing in the polymer itself.

Contents of the invention

One method of the present invention is to provide a method of making a multilayer article, the method comprising: (a) providing a precursor article comprising a curable elastomer layer, said article having an exposed surface that can be used to apply a fluoroplastic layer; ( b) before applying the above-mentioned fluoroplastic layer, thermally insulate the above-mentioned curable elastomer layer; (c) apply a fluoroplastic composition containing copolymerized vinylidene fluoride units to the above-mentioned exposed surface of the above-mentioned precursor product to form a fluoroplastic layer; (d) heating the above fluoroplastic layer; (e) curing the above curable elastomer layer to form a multilayer product comprising the fluoroplastic layer and the elastomer layer.

In a preferred technical solution, the method of the present invention includes applying the above-mentioned fluoroplastic composition in molten state. In a more preferred technical solution, the method of the present invention comprises extrusion coating the above-mentioned fluoroplastic composition onto the above-mentioned exposed surface of the above-mentioned precursor product through a right-angle die to apply the above-mentioned fluoroplastic composition. In a most preferred technical solution, the above-mentioned die head includes a die head body for receiving the above-mentioned fluoroplastic composition, an upstream opening for receiving the above-mentioned precursor product, a downstream opening, and at least part of the above-mentioned opening for receiving the above-mentioned precursor product. product and insulate the sleeve in the die upstream opening of the above curable elastomeric layer prior to application of the above fluoroplastic composition.

In other preferred technical solutions, the method of the present invention further includes cooling the above-mentioned multi-layer product after heating the above-mentioned fluoroplastic layer. The method of the present invention comprises thermally curing the curable elastomeric layer described above. The method of the present invention comprises curing the above-mentioned curable elastomer layer after heating the above-mentioned fluoroplastic layer. The method of the present invention comprises providing a precursor article by extruding the curable elastomeric composition through a die to form the precursor article described above. The aforementioned curable elastomeric layer has an exposed surface available for application of the aforementioned fluoroplastic composition, and the aforementioned fluoroplastic composition is directly applied to the exposed surface of the aforementioned curable elastomeric layer. The aforementioned elastomer includes a fluorinated elastomer or a non-fluorinated elastomer. The melting temperature of the above-mentioned fluoroplastic is about 100 to 330°C, more preferably 150 to 270°C. The above-mentioned fluoroplastics contain copolymerized units formed by tetrafluoroethylene, vinylidene fluoride and monomers selected from hexafluoropropylene, perfluoroalkoxy vinyl ether, perfluoroalkyl vinyl ether, olefins and their mixtures, wherein The amount of vinyl fluoride units is at least 3% by weight, but less than 20% by weight, preferably 10-15% by weight. The method of the present invention also includes bonding a polymer layer to the above-mentioned fluoroplastic layer to form a multilayer article comprising the above-mentioned fluoroplastic layer interposed between the above-mentioned elastomer layer and the above-mentioned polymer layer, preferably the above-mentioned polymer layer directly Bonded to the above-mentioned fluoroplastic layer. The aforementioned polymer contains an elastomer, preferably an elastomer containing nitrile rubber. The method of the present invention also includes placing a polymer layer on the above-mentioned fluoroplastic layer prior to curing. The curing includes a first stage at a first temperature and a second stage at a second temperature, the first temperature being lower than the second temperature. The aforementioned polymers contain elastomers. The multilayer article described above has a tubular shape. The bonding strength between the above-mentioned fluoroplastic layer and the elastomer layer is at least 15 N/cm. The bonding strength between the above-mentioned fluoroplastic layer and the polymer layer is at least 15 N/cm. The method of the present invention also includes cooling the aforementioned curable elastomeric layer prior to applying the aforementioned fluoroplastic composition.

Another aspect of the present invention provides a method of making a multilayer article, the method comprising: (a) providing a precursor article comprising a layer of curable elastomer having a layer of fluoroplastic that can be used to apply exposed surface; (b) applying a melted fluoroplastic composition containing copolyvinylidene fluoride units to the exposed surface of the curable elastomer layer to form the fluoroplastic layer through a right-angle die comprising a The die head body of the above-mentioned fluoroplastic composition, the upstream opening for receiving the above-mentioned precursor article, the downstream opening and at least partly located above the above-mentioned for receiving the above-mentioned precursor article and thermally insulating the above-mentioned curable elastomer before applying the above-mentioned fluoroplastic composition. (c) heating the above-mentioned fluoroplastic layer; (d) thermally curing the above-mentioned curable elastomer layer after heating the above-mentioned fluoroplastic layer to form a multi-layer composite comprising a fluoroplastic layer and an elastomer layer layered products.

Another aspect of the present invention provides a method of making a multilayer article, the method comprising: (a) providing a precursor article comprising a layer of curable elastomer having a layer of fluoroplastic that can be used to apply Exposing the surface; (b) applying a melted fluoroplastic composition containing copolyvinylidene fluoride units to the exposed surface of the curable elastomeric thin layer to form the fluoroplastic layer through a right-angle die comprising a A die body receiving the above-mentioned fluoroplastic composition, an upstream opening for receiving the above-mentioned precursor article, a downstream opening, and at least partially located above the above-mentioned for receiving the above-mentioned precursor article and thermally insulating the above-mentioned curable mold before applying the above-mentioned fluoroplastic composition. sleeve in the die upstream opening of the elastomeric layer; (c) placing the polymeric layer on top of the fluoroplastic layer; (d) heat curing in a first stage at a first temperature and a second stage at a second temperature The aforementioned elastomeric layer and polymeric layer, wherein the aforementioned first temperature is lower than the aforementioned second temperature, form a multilayer article comprising a fluoroplastic layer, an elastomeric layer, and a polymeric layer.

The present invention relates to a method of increasing the bond strength between a fluoroplastic layer and an elastomeric layer of a multilayer article. The elastomer may be a fluoroelastomer or a non-fluorinated elastomer. According to the method, a fluoroplastic composition comprising copolymerized units formed from vinylidene fluoride (DVF) can be applied to the surface of a precursor article comprising a curable elastomeric layer, preferably extruded in molten form through a right angle die The composition is applied to form a fluoroplastic layer. Suitably, the composition is applied directly to the surface of the elastomeric layer. The curable elastomeric layer is insulated to prevent it from being subjected to significant heating prior to application of the fluoroplastic composition. In one embodiment, when the molten fluoroplastic composition is applied by extrusion through a right-angle die, thermal insulation is achieved by installing a sleeve over the die that is at least partially within the upstream end of the die, before applying the fluoroplastic composition. Previously received layers of curable elastomer and insulated.

After application, the fluoroplastic layer is heated and cures, preferably thermally curing, the curable elastomer layer. The curing of the elastomer is preferably carried out separately and after heating the fluoroplastic layer. Combined method of thermally insulating a curable elastomer layer before applying the fluoroplastic composition and heating said fluoroplastic layer after applying the fluoroplastic composition, even without adhesive aids such as surface treatment, a separate adhesive layer, etc. It is also possible to form a strong bond between the fluoroplastic layer and the elastomer layer by curing. For example, bond strengths of at least 15 N/cm can be achieved.

Multilayer articles produced by the methods of the present invention can be provided in a variety of shapes, including sheets, films, containers, hoses, conduits, and the like. The articles are especially useful where chemical resistance and/or barrier properties are required. Examples of specific uses for the articles include their use in rigid and flexible retroreflective sheeting, adhesive articles such as tapes, paint change films, drag reducing films, fuel lines and filler hoses, exhaust hoses, fuel tanks, etc. use. The articles are also useful in chemical handling and processing applications, and as wire and cable coatings or jackets.

The details of one or more implementations of the invention are set forth in the accompanying drawings and the description below. The features, objects and advantages of the present invention will be apparent from the specification, drawings and claims.

Description of drawings

Fig. 1 is a schematic diagram of the process of manufacturing a multi-layer product according to the present invention.

The same reference numerals in the various figures represent the same components.

Detailed ways

Referring to FIG. 1 , one embodiment of a method of making a multilayer article featuring a fluoroplastic layer bonded to an elastomeric layer is illustrated. Extruder 20 extrudes the curable elastomeric composition through die 21 to form a length of tube 22 having a curable elastomeric layer. A second extruder 23 is installed downstream of the extruder 20 and equipped with a right angle die 25 to apply a layer of molten fluoroplastic to the surface of the curable elastomer layer. A plastic (or other insulating material) sleeve 24, such as a tetrafluoroethylene sleeve, is partially inserted into the upstream opening of the die 25 to receive the tube 22 and insulate it prior to extrusion coating, thereby preventing significant thermal degradation prior to application of the fluoroplastic. The elastomeric layer can be cured by heating. The lack of significant heating prior to application of the fluoroplastic facilitates the formation of a strong bond between the fluoroplastic layer and the elastomeric layer after curing. It is also desirable to cool the curable elastomer prior to applying the fluoroplastic. This can be achieved, for example, by treating the curable elastomer layer with a solvent which can then be removed by evaporation.

After extrusion coating, the resulting multilayer article 27 featuring fluoroplastic coated on a curable elastomer layer enters tubular heater 28, which heats said fluoroplastic layer. An example of a useful tubular heater is a radiant heater. During heating, heat is transferred from the heater 28 to the fluoroplastic layer, and then from the fluoroplastic layer to the curable elastomer layer. This heating step is believed to facilitate the formation of a strong bond between the fluoroplastic layer and the elastomeric layer after curing. After the heating operation, the multilayer article can be cooled, for example by immersion in a cooling bath 29 .

The elastomeric layer can be cured in a separate step in the heater 28 or preferably under pressure and higher temperature, before or after immersion in the cooling bath 29 . For example, it may be advantageous to cool the article in bath 29, cut it into appropriately sized segments, and then heat the segments in a pressurized, eg, autoclave, to cure the thin layer of curable elastomer.

The fluoroplastic is preferably an extrusion-coatable material. Such fluoroplastics generally have a melting temperature of about 100-330°C, more preferably about 150-270°C. The fluoroplastic includes copolymerization units formed from VDF, and may further contain copolymerization units formed from other fluorine-containing monomers, non-fluorine-containing monomers, or mixtures thereof. Examples of suitable fluoromonomers include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), 3-chloropentafluoropropylene, perfluoroethylene ether (e.g., perfluoroalkoxy Vinyl ethers such as CF ₃ OCF ₂ CF ₂ CF ₂ OCF=CF ₂ and perfluoroalkyl vinyl ethers such as CF ₃ OCH=CF ₂ and CF ₃ CF ₂ CF ₂ OCF=CF ₂ ), and fluorinated dienes such as perfluoro Diallyl ether and perfluoro-1,3-butadiene. Examples of suitable fluorine-free monomers include olefin monomers such as ethylene, propylene, and the like.

Emulsion polymerization techniques may be used to prepare VDF-containing fluoroplastics as described in U.S. 4,338,237 to Sulzbach et al., incorporated herein by reference. Useful commercially available VDF-containing fluoroplastics include, for example, THV200, THV400, THV500G, THV610X fluoropolymer (available from Dyneon LLC, St. Paul, MN), KYNAR 740 fluoropolymer (available from Atochem North America, Philadelphia, PA), HYLAR 700 (available from Ausimont USA, Inc., Morristown, NJ), and FLUOREL FC-2178 (available from Dyneon LLC).

Particularly useful fluoroplastics comprise interpolymerized units formed from at least TFE and VDF in an amount of VDF of at least 0.1 wt. % but less than 20 wt. %. The amount of VDF is preferably 3 to 15% by weight, more preferably 10 to 15% by weight.

The curable elastomer can be a fluoroelastomer or a non-fluorinated elastomer. Examples of suitable fluoroelastomers include VDF-HFP copolymers, VDF-HFP-TFE terpolymers, TFE-propylene copolymers, and the like. Examples of suitable non-fluorinated elastomers include acrylonitrile-butadiene (NBR), butadiene rubber, chlorinated and chlorosulfonated polyethylene, chloroprene, ethylene-propylene monomer (EPM) rubber, ethylene- Propylene-diene monomer (EPDM) rubber, epichlorohydrin (ECO) rubber, polyisobutylene, polyisoprene, polysulfide, polyurethane, silicone rubber, blends of polyvinyl chloride and NBR, styrene- Butadiene (SBR) rubber, ethylene-acrylate copolymer rubber, and ethylene-vinyl acetate rubber. Commercially available elastomers include Nipol ^™ 1052NBR (Zeon Chemical, Louisville, KY), Hydrin ^™ C2000 epichlorohydrin-ethylene oxide rubber (Zeon Chemical, Louisville, KY), Hypalon ^™ 48 chlorosulfonated polyethylene rubber (EI DuPont de Nemours & Co., Wilmington, DE), Nordel ^™ EPDM (RTVanderbilt Co., Inc., Norwalk, CT), Vamac ^™ ethylene-acrylate elastomer (EI DuPont de Nemours & Co., Wilmington, DE), Krynac ^™ NBR (Bayer Corp., Pittsburgh, PA), Perbunan ^TM NBR/PVC blends (Bayer Corp., Pittsburgh, PA), Therban ^TM hydrogenated NBR (Bayer Corp., Pittsburgh, PA), Zetpol ^TM hydrogenated NBR (Zeon Chemical, louisville, KY), Santoprene™ thermoplastic elastomer (Advanced Elastomer Systems, Akron, OH), and Keltan ^™ EPDM (DSM Elastomers Americas, Addis, LA).

A curing agent is preferably incorporated into the curable elastomer to aid in curing. Examples of useful curing agents include imidazolines, diamines, inner salts of diamines, thioureas, and polyphenol curing agents, as described by reference in U.S. 4,287,322 (Worm), incorporated herein by reference. This reagent is especially useful for epichlorohydrin compositions. Other examples, especially for curing nitrile rubber-containing compositions, include peroxides and sulfur-containing compounds.

For curable fluoroelastomers, examples of useful curing agents include polyols mixed with organic onium salts (eg, organic ammonium, organic phosphonium, and organic sulfonium salts). Specific examples are described, for example, in Fukushi, U.S. 5,658,671 "Fluoroelastomer Coating Composition," incorporated herein by reference. Diamines and peroxides can also be used.

The multilayer article may also contain additional polymer layers. Examples of suitable polymer layers include non-fluorinated polymers such as polyamides, polyimides, polyurethanes, polyolefins, polystyrenes, polyesters, polycarbonates, polyketones, poly Ureas, polyacrylates and polymethylmethacrylates. The fluorothermoplastic layer, the fluoroelastomer layer and the elastic Adhesion between body layers.

A construction that is particularly useful for fuel oil applications is characterized by bonding one side of a relatively thin layer of fluoroplastic that acts as a barrier layer to a relatively thick layer of non-fluorinated polymer that acts as a cover glue, and the opposite side One side is bonded to a relatively thin layer of sealing elastomer (eg, fluoroelastomer or non-fluorinated elastomer). The cover gum provides structural integrity to the article. In order to further increase the structural integrity, reinforcing aids such as fibres, wire meshes and/or wire meshes can be added to the multilayer article, for example as a separate layer or as part of a known layer.

Any or all of the layers of the multilayer article may also include one or more additives. Examples of useful additives include pigments, plasticizers, tackifiers, fillers, conductive materials (e.g., of the type described in U.S. 5,552,199), insulating materials, stabilizers, antioxidants, lubricants, processing aids, impact modifiers additives, viscosity modifiers and their mixtures. For example, in the case of the multilayer articles for fuel oil described above, it is common to use the innermost layer of the conductive structure.

In some cases, it may be desirable to further increase the bond strength between the layers of the multilayer article. For example, additional heat, pressure, or heat and pressure can be applied to the article after curing.

Another method of increasing the bond strength between the layers is to treat the surface of one or more of the layers prior to forming the multilayer article. This surface treatment may consist of a solution treatment using a solvent. If the solvent contains a base, such as 1,8-diaza[5.4.0]bicyclo-7-undecene (DBU), treatment of the fluoropolymer will result in some degree of dehydrofluorination. This dehydrofluorination reaction advantageously promotes adhesion to subsequently applied materials. This is especially the case when the subsequently applied material contains any reagents that are reactive towards unsaturated sites.

Examples of other surface treatments include charge atmosphere treatments such as corona discharge treatment or plasma treatment. Electron beam processing can also be used.

The use of eg aliphatic diamines or polyamines can also improve interlayer adhesion. The amines may be of any molecular weight and, when used, enhance the cohesive bond strength between the layers of the multilayer article. A particularly useful polyamine may be polyallylamine having a molecular weight greater than about 1,000 as determined by gel permeation chromatography. An example of a useful commercially available polyamine is polyallylamine having a molecular weight of about 3,000, commercially available from Nitto Boseki Co., Ltd.

The amine may be added to one or more of the layers of the multilayer article prior to forming the article using conventional methods such as melt mixing. Alternatively, the amine may be applied to the surface of one or more of the layers using conventional coating methods such as spray coating, curtain coating, immersion coating, dipping, and the like.

The present invention will be further illustrated by examples below.

Example

The following examples illustrate the preparation of various multilayer articles featuring fluoroplastics bonded to elastomeric layers. In various examples, the elastomer was a fluoroelastomer prepared by mixing the following ingredients: 100 parts Dyneon FE-5830Q fluoroelastomer (commercially available from Dyneon LLC, St. Paul, MN), 13 parts N-762 carbon black (available from Cabot Corp., Alpharetta, GA), 6 parts of calcium hydroxide HP (available from CPHall, Chicago, IL), 3 parts of magnesium oxide (trade name "Elastomag ^™ 170, Available from Morton International, Danvers, MA) and 6 parts of Calcium Oxide HP (available from CP Hall, Danvers, MA). The composition was extruded in the shape of a tube having an outer diameter of 12 mm and a wall thickness of 0.33 mm to form Fluoroelastomer.

Example 1

The molten fluoroplastic composition was coated onto the surface of the fluoroelastomer tubing using a right-angle die fitted with a polytetrafluoroethylene (PTFE) sleeve. The fluoroplastic is a TFE-HFP-VDF terpolymer containing 76% by weight of TFE, 11% by weight of HFP and 13% by weight of VDF. Fluoroplastics have a melt flow index of 7 and a melting point of 233°C. The PTFE sleeve prevents heating of the fluoroelastomer surface prior to application of the fluoroplastic.

After application of the fluoroplastic composition, the resulting multilayer article was heated by passing the article through a 15.2 cm long tubular heater set at 220°C (the surface temperature of the fluoroplastic was 140°C) before cooling. Once cooled, the articles were cut into smaller samples and then placed on steel mandrels and thermally cured in an autoclave using steam at a temperature of 160° C. and a pressure of 0.4 MPa for 60 minutes. After solidification, the samples were removed from the autoclave and cooled at room temperature.

Adhesion test sheets were provided to evaluate the peel adhesion of the cured samples by separating a 7 mm wide strip of the fluoroplastic outer layer from the fluoroelastomer core by notching in each sample to provide an adhesion test. The thickness of the fluoroplastic layer is 0.3 mm. An ^Instron® 1125 testing machine available from Instron Corp. with a crosshead speed set at 100 mm/min was used as the testing apparatus. The peel strength of the fluoroplastic and fluoroelastomer layers was measured according to ASTM D 1876 (T-peel test), except that the peel angle was 90°. The results of the two samples were averaged. And record the average value in Table 1.

Example 2

The procedure of Example 1 was followed except that the fluoroplastic was a TFE-HFP-VDF terpolymer commercially available from Dyneon LLC, St. Paul, MN under the trade designation "THV-500". The results of the peel adhesion test are listed in Table 1.

Comparative example C-1

The procedure of Example 1 was followed except that the PTFE sleeve was not used. The results of the peel adhesion test are listed in Table 1.

Comparative example C-2

The procedure of Example 1 was followed except that no heater was used. The results of the peel adhesion test are listed in Table 1.

Comparative example C-3

The procedure of Example 1 was followed except that the PTPE sleeve and heater were not used. The results of the peel adhesion test are listed in Table 1.

Table 1 Example number sleeve heater Peel strength (N/cm) 1 have have 25.6 2 have have 25.8 C-1 none have 14.1 C-2 have none 8.0 C-3 none none 4.9

The results in Table 1 demonstrate that insulating the curable elastomer layer prior to applying the fluoroplastic composition and heating the fluoroplastic after applying the fluoroplastic composition to the curable elastomer layer The layer can provide improved interlayer adhesion of the multilayer article after curing.

In another set of embodiments, the multilayer tube comprises an inner fluoroelastomer layer, an intermediate layer of fluorothermoplastic barrier layer and an outer layer of elastomer or rubber or thermoplastic elastomer.

Example 3

In Example 3, THV-500 was coated onto extruded fluoroelastomer tubing having an outer diameter of 16 mm and a wall thickness of 1 mm using a right angle die fitted with a PTFE sleeve. The sleeve prevents heating of the fluoroelastomer surface. In Table 2 are listed the formulations of the fluoroelastomer compounds from which the tubes were made.

Table 2 ingredients (suppliers) FKM compound phr* Dyneon FE-5830Q(FKM)(Dyneon) 100 N-990 (Carbon Black) (Cancarb) 12 Vulcan XC072 (conductive carbon black) (Cabot) 10 Calcium Hydroxide HP (CPHall) 5 Elastomag ^™ 170 (magnesia) (Morton International) 3 Calcium Oxide HP (CPHall) 6 Dibutyl sebacate (DBS) (Aldrich Chemical) 5

*All amounts refer to parts per 100 parts by weight rubber, abbreviated as "phr."

After application of the fluoroplastic composition, the resulting multilayer article was passed through a 15.2 cm long tubular heater set at 220°C (fluoroplastic surface temperature of 140°C) to heat the article before cooling. Fluoroelastomer tubes coated with fluoroplastics were cooled, and then the tubes were coated with ethylene-epichlorohydrin (ECO) rubber with a wall thickness of 2 mm. The articles were cut into cured samples. The samples were cured by steam in an autoclave with a steel mandrel at 143°C and 0.28 MPa for 30 minutes and then at 154°C and 0.41 MPa for 30 minutes. After solidification, the samples were removed from the autoclave and allowed to cool at room temperature.

The fluoroplastic layer was separated from the fluoroelastomer by making an incision and a 25.4 mm wide strip of the ECO layer was separated from the fluoroplastic, providing a sheet for testing interlayer adhesion by a peel test. The thickness of the fluoroplastic layer is 0.3 mm. An ^Instron® 1125 testing machine available from Instron Corp. with a crosshead speed set at 100 mm/min was used as the testing apparatus. Peel strength or adhesion was measured on two tapes according to ASTM D 1876 (T-peel test). The results of the two samples were averaged. And record the average value in Table 3.

Example 4

In Example 4, the sample was prepared and tested as in Example 3, except that the first curing condition was 30 minutes at 146° C. and 0.3 MPa. The test results are summarized in Table 3.

Comparative example C-4

In Comparative Example C-4, the sample was prepared and tested as in Example 3, except that the sample was cured at 143° C. and 0.28 MPa for 60 minutes without applying the second curing condition. The test results are summarized in Table 3.

Comparative example C-5

In Comparative Example C-5, the sample was prepared and tested as in Example 3, except that the sample was cured at 154° C. and 0.41 MPa for 30 minutes without applying the second curing condition. The test results are summarized in Table 3.

table 3 Example curing conditions Peel strength (N/cm) 1st curing 2nd curing Pressure (MPa) temperature(℃) time (minutes) Pressure (MPa) temperature(℃) time (minutes) FKM/THV THV/ECO 3 0.28 143 30 0.41 154 30 42 38 4 0.30 146 30 0.41 154 30 38 33 C-4 0.28 143 60 -- -- -- 30 0.5 C-5 0.41 154 30 -- -- -- 0.3 40

The data in Table 3 demonstrate that the curing step method can significantly increase the peel strength between the FKM/THV layer and the THV/ECO layer in the article compared to the peel strength of the article prepared without the curing step.

Some embodiments of the invention have been described herein. However, it should be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.

For example, while the method shown in Figure 1 illustrates the preparation of a tubular multilayer article, other shapes can also be prepared. Also, while FIG. 1 illustrates the use of an extruder to prepare the curable elastomeric and fluoroplastic layers, other polymer processing techniques may also be used. For example, a curable elastomer and fluoroplastic composition in the form of a sheet can be prepared and then laminated together as long as measures are taken to thermally insulate the curable elastomer before applying the fluoroplastic. Furthermore, while FIG. 1 illustrates the use of a tubular heater for heating the fluoroplastic layer using radiation, other heating methods may also be used. For example, induction heating may be used when heating a fluoroplastic layer containing eg metal particles.

Claims (29)

1. A method for preparing a multilayer product, the method comprising: (a) providing a precursor article comprising a curable elastomeric layer, the article having an exposed surface useful for applying a fluoroplastic layer; (b) thermally insulating said curable elastomer layer prior to applying said fluoroplastic layer; (c) applying a fluoroplastic composition comprising copolymerized vinylidene fluoride units to said exposed surface of said precursor article to form a fluoroplastic layer; (d) heating the fluoroplastic layer; (e) Curing the above curable elastomer layer to form a multilayer article comprising a fluoroplastic layer and an elastomer layer. 2. The method of claim 1, characterized in that the method comprises applying the fluoroplastic composition in molten state. 3. The method of claim 2, characterized in that the method comprises applying the fluoroplastic by extrusion coating the fluoroplastic composition onto the exposed surface of the precursor article through a right angle die combination. 4. The method of claim 3, wherein the die comprises a die body for receiving the fluoroplastic composition, an upstream opening for receiving the precursor article, a downstream opening and at least partially located A sleeve within an opening upstream of the die for receiving the precursor article and insulating the curable elastomeric layer prior to application of the fluoroplastic composition. 5. The method of claim 1, further comprising cooling the multilayer article after heating the fluoroplastic layer. 6. The method of claim 1, wherein the method includes thermally curing the curable elastomeric layer. 7. The method of claim 1, characterized in that the method comprises curing the curable elastomer layer after heating the fluoroplastic layer. 8. The method of claim 1, wherein said method comprises extruding a curable elastomeric composition through a die to form said precursor article to provide a precursor article. 9. The method of claim 1, wherein said curable elastomeric layer has an exposed surface available for application of said fluoroplastic composition, and said fluoroplastic composition is applied directly to said curable elastomeric layer. Cured on the exposed surface of the elastomer layer. 10. The method of claim 1, wherein the elastomer comprises a fluoroelastomer. 11. The method of claim 1, wherein the elastomer comprises a non-fluorinated elastomer. 12. The method of claim 1, characterized in that the melting temperature of the fluoroplastic is about 100-330°C. 13. The method of claim 1, characterized in that the melting temperature of the fluoroplastic is about 150-270°C. 14. The method according to claim 1, characterized in that the fluoroplastic contains tetrafluoroethylene, vinylidene fluoride and selected from hexafluoropropylene, perfluoroalkoxy vinyl ether, perfluoroalkyl vinyl ether, olefin and copolymerized units formed from monomers of their mixtures. 15. The method according to claim 14, characterized in that the amount of vinylidene fluoride units is at least 3% by weight but lower than 20% by weight. 16. The method of claim 14, characterized in that the amount of vinylidene fluoride units is 10-15% by weight. 17. The method of claim 1, further comprising bonding a polymer layer to said fluoroplastic layer to form a polymer layer containing said elastomer layer interposed between said polymer layer and said polymer layer. A multilayer product with a fluoroplastic layer. 18. The method of claim 17, characterized in that the method comprises bonding the polymer layer directly to the fluoroplastic layer. 19. The method of claim 17, wherein the polymer comprises an elastomer. 20. The method of claim 19, wherein the elastomer comprises nitrile rubber. 21. The method of claim 1, further comprising placing a polymer layer on the fluoroplastic layer prior to curing. 22. The method of claim 21, wherein said curing comprises a first stage at a first temperature and a second stage at a second temperature, said first temperature being lower than said second temperature. 23. The method of claim 22, wherein the polymer comprises an elastomer. 24. The method of claim 1, wherein the multilayer article is in the form of a tube. 25. The method of claim 1, wherein the bond strength between the fluoroplastic layer and the elastomeric layer is at least 15 N/cm. 26. The method of claim 22, wherein the bond strength between the fluoroplastic layer and the polymer layer is at least 15 N/cm. 27. The method of claim 1, further comprising cooling the curable elastomeric layer prior to applying the fluoroplastic composition. 28. A method of making a multilayer article, the method comprising: (a) providing a precursor article comprising a curable elastomeric layer having an exposed surface useful for applying a fluoroplastic layer; (b) applying a molten fluoroplastic composition comprising copolymerized vinylidene fluoride units to the exposed surface of said curable elastomeric layer through a right angle die to form a fluoroplastic layer, The die includes a die body for receiving the fluoroplastic composition, an upstream opening for receiving the precursor article, a downstream opening, and an opening at least partially located on the mouth for receiving the precursor article and thermally insulating a sleeve within the opening of the die upstream of the curable elastomeric layer prior to applying the fluoroplastic composition; (c) heating the fluoroplastic layer; (d) thermally curing the curable elastomer layer after heating the fluoroplastic layer to form a multilayer article comprising a fluoroplastic layer and an elastomer layer. 29. A method of making a multilayer article, the method comprising: (a) providing a precursor article comprising a curable elastomeric layer having an exposed surface useful for applying a fluoroplastic layer; (b) applying a molten fluoroplastic composition comprising copolyvinylidene fluoride units to the exposed surface of said curable elastomeric thin layer through a right angle die to form a fluoroplastic layer, The die includes a die body for receiving the fluoroplastic composition, an upstream opening for receiving the precursor article, a downstream opening, and an opening at least partially located on the mouth for receiving the precursor article and thermally insulating a sleeve within the opening of the die upstream of the curable elastomeric layer prior to applying the fluoroplastic composition; (c) placing a polymer layer on said fluoroplastic layer; (d) thermally curing the elastomer layer and the polymer layer in a first stage at a first temperature and a second stage at a second temperature, wherein the first temperature is lower than the second temperature, forming a Layer, elastomer layer and polymer layer multilayer article.

Images