Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1998-11-25
2001-04-24
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S098000, C521S134000, C521S140000
Reexamination Certificate
active
06221928
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to foamed articles including a polyolefinic polymer and maleic anhydride.
Generally, polymer materials can be used to produce a variety of articles including foamed articles. Foamed polymeric materials have a variety of uses. For example, natural rubber latex foamed articles provide soft materials for body contact and the application of cosmetics. Polyvinyl chloride (PVC) plastisol foamed articles can have a soft, durable feel that simulates leather to the touch. Open cell foamed articles based on polyurethanes have been made suitable for many applications, such as cushions for packaging, automotive applications, home bedding, filters (e.g., for air conditioners), applicators (e.g., for shoe polish), or sound attenuating panels (e.g., for rooms or acoustic speakers).
A variety of polyolefinic polymers may generally be used for each application. However, a polymer which may be desirable for one property, such as cost, may provide a lower quality end product, such as a foamed article with significant voiding.
For example ethylene-propylene diene monomer terpolymer (EPDM) is a desirable material, due to its superior temperature resistance, weather resistance, crosslinking, and non-corrosive properties. However, foamed products utilizing significant quantities of ethylene-propylene diene monomer terpolymer can exhibit poor physical characteristics, such as tackiness or incomplete cell formation, rendering them unsuitable for certain applications. Other polymers, such as high vinyl acetate content ethylene-vinyl acetate (EVA) and ethylene-acrylic elastomers, can be unsuitable for use in certain applications. Ethylene-acrylic elastomers, for example, can provide a soft hand and excellent temperature properties, but the polymeric mixture generally exhibits sticking and blocking, and as such can be difficult to process.
Further, during production, significant amounts of polymer material are frequently cut or removed from the end product. This material can be known as reclaim. It can be difficult to incorporate reclaim materials, such as crosslinked reclaim, into foamed products.
SUMMARY OF THE INVENTION
In one aspect, the invention features a foamed polymer article including a mixture including a maleic anhydride-grafted component and a first polyolefinic polymer.
The maleic anhydride can be grafted to the first polyolefinic polymer.
The maleic anhydride content of the grafted polyolefinic polymer can be between about 0.01 weight percent and about 10 weight percent, e.g., between about 0.4 weight percent and about 2.0 weight percent. The foamed article can include between about 1 weight percent and about 90 weight percent, e.g., between about 5 weight percent and about 30 weight percent, of the maleic anhydride-grafted polyolefinic polymer.
In another aspect, the invention features a method of making a foamed article. A mixture including a first polyolefinic polymer and maleic anhydride is provided. The maleic anhydride is grafted to a portion of the mixture. The mixture is cross-linked sufficiently to form a flexible polymer article having low tackiness and expanded to form a foamed article. The method can include the step of grafting maleic anhydride to the first polyolefinic polymer.
The first polyolefinic polymer can be selected from the group consisting of a low density polyethylene, a very low density polyethylene, a linear low density polyethylene, a single-site initiated polyolefin, (e.g., a single-site initiated polyethylene, a single-site initiated ethylene-propylene diene monomer terpolymer, or a single-site initiated ethylene-propylene rubber), an ethylene-propylene diene monomer terpolymer, an ethylene-propylene rubber, and an ethylene-acrylic elastomer.
The mixture can include an oil, such as a mineral oil or a silicon oil. The mixture can include greater than 25 weight percent of an oil, e.g., between 30 weight percent and 40 weight percent of an oil.
The mixture can further include a second polyolefinic polymer, such as reclaim, a ethylene-propylene diene monomer terpolymer, a ethylene-vinyl acetate, or an ethylene-acrylic elastomer.
The mixture can include between 5 weight percent and 50 weight percent, e.g., between 10 weight percent and 30 weight percent, of an ethylene-propylene diene monomer terpolymer. The mixture can include between 10 weight percent and 50 weight percent ethylene-acrylic elastomer.
The mixture can be cross-linked with a silane, with radiation, or with a peroxide, such as, for example, dicumyl peroxide.
The mixture can include between 10 weight percent and 50 weight percent reclaim, e.g., between 20 weight percent and 30 weight percent reclaim.
The expansion of the mixture can include free expansion, or compression molding of the mixture. The compression molding can include pressing the mixture using a high tonnage press at a temperature of between 240 and 480° F., e.g., between 275 and 320° F., and a pressure of between 50 and 5000 psi, e.g., between 250 and 2500 psi, for between 20 and 90 minutes followed by heating the polymer mixture at a temperature between 300 and 380° F.
The method can produce a closed cell foamed article or an open cell foam. The method can include the step of crushing the foamed article after the expanding step to form an open cell foamed article.
The method can include the step of applying a coating, an adhesive, or a laminated layer to a surface of the article. The method can include the step of dipping the article to form a layer on a surface of the article.
The foamed article can have a Shore A durometer greater than 30. The foamed article can have a foam density between about 1.5 pounds per cubic foot and 50 pounds per cubic foot. The foamed article can have a 25 percent compression deflection of less than 3 pounds per square inch.
The foamed article can be a bead or particulate foam.
In a another aspect, the invention features a polymer article including a mixture including an ethylene-acrylic polymer and maleic anhydride grafted to a component of the mixture.
The polymer article can further include a first polyolefinic polymer with the maleic anhydride grafted to the first polyolefinic polymer. The first polyolefinic polymer can be a very low density polyethylene. The first polyolefinic polymer content of the polymer article can be between about 1 weight percent and about 90 weight percent. The maleic anhydride content of the first polyolefinic polymer can be between about 0.01 weight percent and about 10 weight percent.
An open cell foamed article is a foam where there is an interconnection between cells in the foam. There can be greater than about 10 percent open cells (e.g., between 10 and 50 percent) in an open cell foamed article, preferably greater than 40 percent, more preferably greater than 80 percent, and most preferably greater than 90 percent. The amount of open cells in a foamed article can be increased by crushing the foam. A crushed open cell foamed article can have between 50 and about 98 percent open cells.
A closed cell foamed article has a predominance of closed cells. For example, a preferred closed cell foamed article can have 70 percent or greater closed cells.
The open cell content of a foamed article can be determined by measuring the amount of water that is absorbed into the foamed article when the foamed article is immersed in water. Another method is a gas-volume method using a pycnometer, such as a Quantachrome Model 1000 pycnometer, which measures the percentage of open cells according to method ASTM D-2858.
Ethylene-propylene diene monomer terpolymer (EPDM) is a terpolymer of ethylene, propylene, and a diene monomer. EPDM provides, for example, superior temperature resistance, weather resistance, crosslinking, and non-corrosive properties.
An ethylene-acrylic elastomer is a copolymer of ethylene and methyl acrylate. Ethylene-acrylic elastomers provide improved heat resistance, oil resistance, ozone resistance, weather resistance, and low temperature flexibility. Ethylene-acrylic elastomers are generally non-corrosive, and are blendab
Bambara John D.
Hurley Robert F.
Kozma Matthew L.
Smith Scott C.
Fish & Richardson P.C.
Foelak Morton
Sentinel Products Corp.
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