MX2008006871A - Fluoropolymer modified acrylic capstock - Google Patents

Abstract

The invention relates to the use of an impact-modified acrylic blend with a low level of fluoropolymer to achieve impact resistance and solvent resistance in a capstock formulation. Preferably the acrylic blend contains a methyl methacrylate- based acrylic polymer and polyvinylidene fluoride.

Description

FLUOROPOLIMERO MODIFIED ACRYLIC SURFACE LAYER FIELD OF THE INVENTION The present invention relates to the use of an impact modified acrylic blend with a low level of fluoropolymer to achieve impact resistance and solvent resistance in a surface layer formulation. Preferably, the acrylic mixture contains an acrylic polymer based on methyl methacrylate and polyvinylidene fluoride. BACKGROUND OF THE INVENTION Certain structural plastics, such as high impact polystyrene (HIPS), acrylonitrile / butadiene / styrene (ABS) resins, poly (vinyl chloride) (PVC) resins and the like, exhibit attractive mechanical properties when they are extruded, molded or formed into various articles of manufacture. Such items include, for example, tubs, shower benches, countertops, liners and housings for appliances, building materials, doors, windows, lining boards, floors, railings and shutters, lawn and garden applications, marine applications, pool and storage facilities. Although these structural plastics are strong, firm and relatively cheap, the properties of their exposed surfaces are less than ideal. That is, the surfaces of structural plastics are degraded by light; they can be easily scraped off, and can be eroded by common solvents. Accordingly, it has become a practice in the industry to apply other resinous materials on the structural plastic to protect the underlying structural material and provide a surface that can withstand abuse related to the environment of use. Said surface materials are called "surface layers". Generally, the surface layer is much thinner than the plastic structure, typically, it is about 5 to about 25% of the total thickness of the composite comprising the surface layer and the structural plastic layers. For example, the thickness of the surface layer can be about 0.1 to about 2.5 mm, since the thickness of the structural plastic layer can be about 1.0 to about 10 mm. As a class, acrylic polymers, known for their excellent optical characteristics, resistance to degradation by sunlight, hardness, water inertia and common chemicals, durability and firmness, are surface layers of choice for various structural plastics. Said acrylic surface layers are described in US Pat. No. 6,852,405, incorporated herein by reference. U.S. Patent 5,318,737 describes the use of the impact modified acrylic surface layer for use on PVC by coextrusion. Fluoropolymers are known for their excellent durability and weather resistance; however, they suffer from poor adhesion to most polymeric substrates. To overcome this deficiency, mixtures of fluoropolymer and acrylic polymers have been used to produce a good combination of adhesion to thermoplastic substrates, impact resistance and processing properties. Mixtures having 30 to 80 percent fluoropolymer have been described in US Patents 5,322,899 and 6,444,311. Surprisingly, it has been found that acrylic surface layers containing low levels of fluoropolymer exhibit excellent impact resistance and solvent resistance in a surface layer formulation.

SUMMARY OF THE INVENTION The invention relates to an impact modified acrylic composition for use as a surface layer comprising a mixture of: a) 5 to 89 weight percent acrylic polymer, and b) 1 to 25 weight percent fluoropolymer weight; and c) 10 to 70 weight percent of one or more impact modifiers. The invention further relates to a polymer composite comprising a structural polymer to which a surface layer of impact modified acrylic composite has been directly adhered comprising: a) 5 to 89 weight percent acrylic polymer, and b) 25 weight percent fluoropolymer; and c) 10 to 70 weight percent of one or more impact modifiers wherein the layer of impact modified acrylic composition has a thickness of 0.1 to 2.5 mm.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to the use of an impact modified acrylic blend with a low level of fluoropolymer to achieve impact resistance and solvent resistance in a surface layer formulation. The acrylic mixture contains 5 to 89 percent by weight, preferably 30 to 70 percent by weight, of at least one copolymer or acrylic polymer and 1 to 25 percent by weight, preferably 5 to 15 percent by weight per at least one fluoropolymer. By acrylic polymer, as used herein, includes homopolymers, copolymers and terpolymers formed of alkyl methacrylate and alkyl acrylate monomers and mixtures thereof. The alkyl methacrylate monomer is preferably methyl methacrylate, which may comprise from 60 to 100 of the monomer mixture. 0 to 40 percent of other acrylate and methacrylate monomers may also be present in the monomer mixture. Other acrylate and methacrylate monomers useful in the monomer mixture include, but are not limited to monomers of methyl acrylate, ethyl acrylate and ethyl methacrylate, butyl acrylate and butyl methacrylate, methacrylate and isooctyl acrylate, lauryl acrylate and lauryl methacrylate, stearyl acrylate and stearyl methacrylate, isobornyl acrylate and methacrylate, ethyl acrylate and methacrylate methoxy, acrylate and 2-ethoxy ethyl methacrylate, acrylate monomers and ethyl methacrylate dimethylamine. The (meth) alkyl acrylic acids, such as (meth) acrylic acid and acrylic acid may be useful for the monomer mixture. Small levels of multifunctional monomers can also be used as crosslinking agents. Suitable crosslinking monomers include; however, they are not limited to, for example, allyl methacrylate, allyl acrylate, divinylbenzene, dimethacrylate and ethylene glycol diacrylate, ethylene glycol triacrylate and trimethacrylate, butylene glycol dimethacrylate, glycidyl methacrylate, triallyl isocyanurate, N-hydroxymethyl acrylamide, N, N-methylene diacrylamide and dimethacrylamide, triallyl citrate, trimethylolpropane triacylate, trimethylolpropane trimethacrylate and divinyl diethylene glycol ether. A preferred acrylic polymer is a copolymer of methyl methacrylate and 2-16 percent of one or more C? - of acrylates. The fluoropolymer blended with the acrylic polymer to form the polymer matrix is a polymer made primarily of fluoride monomers. The term "fluoride monomers" as used in accordance with the present invention means an olefinically unsaturated and fluorinated monomer capable of being subjected to the free radical polymerization reaction. Exemplary fluoride monomers suitable for use in accordance with the invention include, but are not limited to, vinylidene fluoride, vinyl fluoride, trifluoroethylene, tetrafluoroethylene (TFE), and hexafluoropropylene (HFP) and their respective copolymers. The term "fluoropolymer" refers to polymers and copolymers (including polymers having two or more different monomers, including terpolymers for example) containing at least 50 percent moles of fluoride monomer units. A preferred fluoropolymer is polyvinylidene fluoride. The acrylic matrix includes from 10 to 70 weight percent, and preferably from 30 to 60 weight percent of one or more modifiers per impact. Preferred impact modifiers and core layer multiple polymers and block copolymers having at least one hard block and one soft block. The impact modifiers (multiple layer) of core crust could have a hard and a soft crust (rubber or elastomer), a hard core covered with a layer of soft elastomer, and a hard crust, of another core crust morphology known in the technique. The rubber layers are composed of low glass transition (Tg) polymers that include, but are not limited to, butyl acrylate (BA), ethylexyl acrylate (EHA), butadiene (BD), BD / styrene, butylacrylate / styrene, and many other combinations. In addition to the impact modifiers, the impact modified acrylic composition of the invention will contain at least one percent, and up to 15 weight percent of other common additives, such as antioxidants, UV absorbers, lubricants, colorants and dyes. The surface layer composition can be applied to a structural plastic in various and different ways. For example, sheets or preformed films of the structural plastic and the surface layer can be laminated together, by thermal fusion, by pressure lamination or by lamination by a suitable adhesive or by a mutually compatible polymer interleave. The adhesion of the layer of the surface layer to the substrate can be improved by the use of a link layer. The impact grade acrylic fluoropolymer mixture can be used as a surface layer (protective layer) on structural plastics including but not limited to ABS, PVC, polycarbonate, polycarbonate / ABS blend, ABS / nylon blend, polycarbonate / nylon mix, glass reinforced polyester thermosets, and other resins to provide good appearance, gloss, surface hardness, and weather resistance for sheets and formed parts. In one embodiment, the structural plastic is polyvinyl chloride (PVC), which includes polyvinyl chloride and foamy PVC compounds. The structural plastic can, optionally, be modified by impact.

It has been found that gloss reduction, gloss retention, and gloss control can be achieved by using the acrylic composition of the invention. Other methods of lamination, such as co-extrusion or bi-extrusion or even dispersion casting or solution, can be used to laminate the structural plastics and an acrylic surface layer. Alternatively, in suitable cases, the structural plastic and an acrylic surface layer can be co-extruded, and this is often a method of choice due to cost and ease of manufacture. The resin compositions of this invention can also be extruded or injection molded into monolithic sheets, pellets, profiles and virgin film using conventional methods well known in the art. The film can then be used in applications such as insert molding. The impact modified acrylic blend of the invention provides an ideal balance of impact strength and solvent resistance (such as isopropyl alcohol), hardness and weather resistance. The mixture provides colors highly resistant to the weather, useful in many applications. Such items include, for example, tubs, shower benches, countertops, liners and housing for appliances, building materials, such as doors, windows and shutters, floors, lining boards, guardrails and storage facilities.

EXAMPLES The following PMMA compositions contain 49 weight percent polymeric acrylic impact modifier together with 1 and 3 weight percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The pallets were dried overnight in an air circulation oven, then injection molded into flat plates for testing. Samples of the plates were tested for impact resistance by a rapid drop movement procedure following ASTM procedure D 3763. The results are shown in Table 1.

TABLE 1 The following PMMA compositions contain 47% polymeric acrylic impact modifier along with 1 and 3 percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with water bath, and then pelletized. The pallets were dried overnight in an air circulation oven, then injection molded into flat plates for testing. Samples of the plates were tested for impact resistance by a rapid drop movement procedure following ASTM procedure D 3763. The results are shown in Table 2.

TABLE 2 The following PMMA compositions contain 47% polymeric acrylic impact modifier along with 1 and 3 percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The pallets were dried overnight in an air circulation oven, then injection molded into flat plates for testing. An Izod notch impact following the ASTM D 256 procedure tested the plate samples for impact resistance. The results are shown in Table 3. TABLE 3 The following PMMA compositions contain 45% polymeric acrylic impact modifier along with 1 and 3 percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The pallets were dried overnight in an air circulation oven, then co-extruded on a polyvinyl chloride or PVC plastic substrate to produce a multiple layer sheet for the impact test. Samples of the plates were tested for impact resistance by rapid drop movement procedure following ASTM procedure D 3763. The results are shown in Table 4..

TABLE 4 The following PMMA compositions contain 50% polymeric acrylic impact modifier along with 1 and 3 percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The samples of the plates were cut into one inch wide specimens and then tested for resistance to 70% isopropyl alcohol solvent by constant deformation procedure. Time was recorded for the specimens to crack in minutes; The average of 10 specimens is recorded below. The test ended after 30 minutes with uncracked specimens after 30 minutes classified as NC (no crack). The results are shown in Table 5. Note: a longer time to crack indicates better chemical resistance. TABLE 5 The following PMMA compositions contain 40% polymeric acrylic impact modifier along with 1 and 3 percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The samples of the plates were cut into one inch wide specimens and then tested for resistance to 70% isopropyl alcohol solvent by constant deformation procedure. Time was recorded for the specimens to crack in minutes. The average of 10 specimens is recorded below. The test is finished after 30 minutes with uncracked specimens after 30 minutes classified as NC (no crack). The results are shown in Table 5. Note: a longer time to crack indicates better chemical resistance. TABLE 6 EXAMPLE The following PMMA compositions contain 49% by weight polymeric acrylic impact modifier together with 1 and 3 weight percent non-polymeric additives. The previously mixed materials were melted by double-helix extrusion at temperatures between 150 ° C and 300 ° C, cooled with a water bath, and then pelletized. The balls were dried overnight in an air circulation oven, then injection molded into flat plates for testing. Samples of the plates were tested for solvent resistance by measuring brightness as molded and then exposed to 70% IPA for 30 minutes. The results are shown in Table 7. A higher percentage of specular brightness after solvent exposure indicates better chemical resistance. TABLE 7

Claims (12)

1. NOVELTY OF THE INVENTION
2. Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property:
3. CLAIMS 1.- An impact modified acrylic composition for use as a surface layer, characterized in that it comprises a mixture of: a) 5 to 89 weight percent acrylic polymer, and b) 1 to 25 weight percent fluoropolymer; and c) 10 to 70 weight percent of one or more impact modifiers. 2. The impact modified acrylic composition according to claim 1, characterized in that said impact-modified acrylic composition comprises from 30 to 70 weight percent acrylic polymer, and 5 to 15 weight percent fluoropolymer. 3. The impact modified acrylic composition according to claim 1, characterized in that said acrylic polymer comprises a polymethacrylate polymer comprising at least 60 weight percent of methyl methacrylate units.
4. 4. The impact-modified acrylic composition according to claim 1, characterized in that said acrylic polymer comprises a polymethacrylate polymer comprising at least 80 weight percent of methyl methacrylate units, the remaining is of C? _4 of alkyl acrylate units.
5. 5. The impact modified acrylic composition according to claim 1, characterized in that said fluoropolymer is polyvinylidene fluoride.
6. 6. The impact modified acrylic composition according to claim 1, characterized in that it comprises from 30 to 70 weight percent of one or more impact modifiers.
7. 7. The impact modified acrylic composition according to claim 1, characterized in that it also comprises at least 1.0 weight percent of one or more additives selected from the group consisting of antioxidants, UV absorbers, lubricants, colorants and dyes. .
8. 8. A polymer composite comprising a structural polymer having a surface layer of impact-modified acrylic composition adhered directly thereto, characterized in that it comprises a mixture of: a) 5 to 89 weight percent acrylic polymer, and b) 1 to 25 weight percent fluoropolymer; and c) 10 to 70 weight percent of one or more impact modifiers, wherein the layer of impact modified acrylic composition has a thickness of 0.1 to 2.5 mm.
9. 9. The polymer composite according to claim 8, characterized in that said structural polymer comprises ABS, polyvinyl chloride, polycarbonate, polycarbonate / ABS blend, ABS / nylon blend, glass reinforced polyester thermosets, or a mixture of polycarbonate / nylon.
10. 10. The polymer compound according to claim 9, characterized in that said polyvinyl chloride polymer is selected from a non-foaming polyvinyl chloride, a chlorinated polyvinyl chloride, a foamed polyvinyl chloride, a polyvinyl chloride modified by impact, and a polyvinyl chloride compound.
11. 11. A method of reducing gloss in an acrylic composition characterized in that it comprises adding from 1 to 25 weight percent of one or more fluoropolymers to the acrylic composition.
12. 12. - The method according to claim 11, characterized in that said weight percentage of fluoropolymers is in the range of 5 to 15 weight percent.