Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1995-05-12
2003-07-08
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06590037
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to acrylate copolymer blends and in particular to ethylene methylacrylate copolymer/ethylene butylacrylate copolymer blends and their use as a layer or interlayer which is bonded to mineral (e.g., glass) or polymer substrates for the manufacture of bilayer or multiple layer laminates. In particular, these films are useful between two or more transparent layers made of glass or polymer materials for use as safety glass for automotive and architectural applications.
2. Technology Review
For over three decades significant efforts have been made to find an interlayer film which performs as well as polyvinylbutyral (PVB) without its inherent drawbacks. A number of polymers and formulations based on them have been used to produce transparent interlayer films for bilayer and multiple layer mineral (e.g., glass) or polymer sheets, particularly for flat glass products in automotive and architectural safety glass applications. The major glass laminate manufacturers for the most part have still found that for their cost polyvinylbutyral (PVB) compositions provide the best overall performance and therefore these have been the interlayer of choice for laminated glass applications.
The performance of the interlayer films is based on film characteristics such as tensile strength, elongation at break, softening point and glass adhesion strength and laminate properties such as luminous transmittance, boil test stability, humidity test stability, light stability and impact and penetration resistance. While conventional PVB interlayers perform well, they do suffer from several drawbacks.
The major drawback of PVB is its moisture sensitivity.
This is important because during storage and use under what would be considered typical conditions in a flat glass manufacturing environment there is the potential for significant increases in moisture content. The increased moisture in interlayer films results in increased haze and may cause bubble formation in the final laminated flat glass products which is unacceptable to both the manufacturers and their customers. Therefore, special precautions have to be taken to keep the moisture content of the PVB film and ulitmately the haze of the laminated flat glass products to an optimum. These special precautions may include reducing storage times of the PVB film to a minimum, refrigeration of the PVB film prior to lamination, pre-drying of the PVB film and/or the use of dehumidifiers in the clean rooms used for preparing the laminates. This both increases the cost and the difficulty in manufacturing laminates made with a polyvinyl butyral interlayer. Even then when the edges of the laminated glass are exposed to moisture, haze will develop.
Another drawback of PVB is the need for a plasticizer in film for bonding the PVB to the glass. The plasticizer tends to migrate over time leading to changes in the properties of the laminate and in particular delamination will begin to occur at the edges of the laminated glass due to loss of the plasticizer.
The other polymers and formulations which have been used or tried include those based on polyurethane (PU) polyvinylchloride (PVC), ethylene copolymers such as ethylenevinylacetate (EVA), polymeric fat acid polyamide (PAM), polyester resins such as polyethyleneterephtalate (PET), silicone elastomers (SEL), epoxy resins (ER) or polycarbonates such as elastomeric polycarbonates (PC and EPC). While many of these polymers and formulations do not have as relatively significant a moisture absorption problem as PVB, they do lack the overall performance of the PVB films at comparable costs. Further, some of these polymers and formulations require enhanced processing such as irradiation or the use of additional chemical components such as plasticizers which affect the cost and properties of the film and the flat glass products made using the film. For example, plasticizers will tend to migrate over time further affecting the properties of both the film and the products made using the film.
An object of this invention is to produce a polymer film which has a tensile strength, moisture absorption, elongation at break, softening point and a glass adhesion strength which are comparible or superior to PVB, and which can be incorporated in laminated glass products such as windshield and architectural safety glass that have a luminous transmittance, boil test stability, humidity test stability, light stability and impact and penetration resistance comparible or superior to those made with PVB.
A further object of this invention is to produce an ethylene acrylate copolymer blend and film which is useful as a component of optical laminates.
A further object of this invention is to produce an ethylene acrylate copolymer blend and film which can be processed into an interlayer under conditions similar to those used for processing PVB.
SUMMARY OF THE INVENTION
The present invention comprises a film formed from an acrylate blend. The preferred blend comprising components (a) and (b), component (a) being an ethylene butyl acrylate copolymer (EBAC) which is less than about 95 percent percent by weight of a total weight of components (a) and (b), wherein the EBAC has a content of acrylate groups from about 8 to about 36 percent by weight of the total weight of the EBAC; and component (b) being an ethylene methyl acrylate copolymer (EMAC) which is greater than about 5 percent by weight of the total weight of components (a) and (b), wherein the EMAC has a content of acrylate groups from about 8 to about 42 percent by weight of the total weight of the EMAC.
The invention further includes a process for manufacturing this film comprising the steps of mixing the melt of thermoplastic polymer resins to form an ethylene butyl acrylate/ethylene methyl acrylate blend and forming the ethylene butyl acrylate/ethylene methyl acrylate blend of thermoplastic resins into a film. The invention still further includes a laminate comprising at least a first layer which is typically transparent and at least one layer comprised of the film described above. The invention still further includes a laminate comprising an acrylate film laminated between two lamina wherein the film and the laminate have properties similar to PVB and laminates made with PVB, respectively.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is a film which has particular utility in glass laminates. The film comprises a blend of two or more acrylates. Examples of these acrylates include ethylene butyl acrylate, ethylene methyl acrylate, isobutylacrylate, and ethylene propyl acrylate. These examples are; however, given by way of illustration and not by way of limitation. The film, preferably, comprises a blend of two components. These being component (a) which is an ethylene butyl acrylate copolymer and component (b) which is an ethylene methyl acrylate copolymer.
The ethylene butyl acrylate (EBAC) of component (a) has a content of acrylate groups from about 8 to about 36 percent, preferably from about 16 to about 26 percent by weight and more preferably from about 18 to about 22 percent by weight of the total weight of the ethylene butyl acrylate (EBAC).
The ethylene methyl acrylate of component (b) has a content of acrylate groups from about 8 to about 42 percent, preferably from about 20 to about 32 percent, and more preferably from about 22 to about 27 percent by weight of the total weight of the ethylene methyl acrylate (EMAC).
The melt flow rate of the ethylene butyl acrylate copoylmer (EBAC) used as component (a) of the film as measured by ASTM Test Method D-1238 is preferably from about 0.5 to about 20.0 grams/10 minutes, more preferably is from about 0.5 to about 10 grams/10 minutes, and most preferably is from about 0.5 to about 6.0 grams/10 minutes.
The melt flow rate of the ethylene methyl acrylate copoylmer (EMAC) used as component (b) of the film as measured by ASTM Test Method D-1238 is preferably from about 0.5 to about 100.0 grams/10 minutes, more preferably is from about 0.5 to about 20 gra
Friedman Michael
Laucirica Louis
Crosby Mike W.
Nutter Nathan M.
Saint-Gobain Performance Plastics Corporation
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