Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2002-05-31
2003-04-22
Pezzuto, Helen L. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S318400, C526S320000, C526S323100, C526S325000, C526S347000
Reexamination Certificate
active
06552147
ABSTRACT:
Acrylic polymers have many useful properties such as durability, flexibility in composition and glass transition temperature (“Tg”), weather resistance, adhesion to polar substrates, and compatibility with many polar polymers and inoganic components. While each of the properties may be desirable, it is difficult to obtain all of them in one polymer. One often needs to sacrifice one property to gain another because the properties of the polymer depend on the polymer's composition, molecular weight, and Tg. For example, a low Tg may be desirable for a polymer composition which would be useful in adhesive applications, but the low Tg polymer may not provide good durability.
In addition, because acrylic polymers are generally amorphous, they are not effective in all applications where crystallinity is desired. They do not adhere well to most non-polar substrates such as polyolefins. Amorphous acrylic polymers also are inferior in terms of water resistance and durability as compared with polyolefins. Therefore, there is a need for low cost polymer compositions which provide durability, flexibility in composition and Tg, weather resistance, adhesion to polar and non-polar substrates, compatibility with polar polymers and inoganic components, and water resistance.
Previous methods to achieve a combination of desired properties of acrylic polymers and olefin polymers in “one” polymer included physically mixing an acrylic polymer and an olefin polymer or copolymerizing an olefin monomer and an acrylic monomer. These methods have not been successful. Physical mixing of acrylic polymers and polyolefins does not usually yield useful compositions because the two polymers are incompatibile. Copolymerizing an olefin monomer and an acrylic monomer is difficult because there is poor reactivity between the two monomers. In addition, copolymerization of two monomers usually results in a composition with an average of the combined properties of each homopolymer rather than enhanced properties.
U.S. Pat. No. 5,387,450 ('450) tries to solve the problem. This patent discloses polymer compositions which contain as polymerized units crystallizable side chain monomers and are useful as adhesives. Below the melting temperature of the crystallizable side chain, the polymer is non-tacky. Above the melting temperature of the crystallizable side chain, the polymer turns into a tacky adhesive. The compositions are required to contain at least 50 weight percent of a crystallizable side chain monomer. The crystallizable side chain monomers are acrylates or methacrylates with 14 to 22 carbon atoms as side chains. Even though this patent provides a route to achieve some of the properties discussed above, there are still several problems unresolved by the patent. The crystallizable side chain monomers of the patent have lower melting points and are more soluble in organic solvents than crystallizable side chain monomers with more carbon atoms in the side chains. Therefore, one problem is that the patent does not address how to process crystallizable side chain monomers with more carbon atoms in the side chains, which require higher temperatures to melt and are less soluble in organic solvents. Another problem is that crystallizable side chain monomers are relatively new and due to their special structure are estimated to cost several times more than the other monomeric components. For these reasons, it is desirable to minimize the amount of crystallizable side chain monomer in one polymer and still achieve the properties described above. Despite the disclosure of '450, there is still a need for low cost polymer compositions which provide durability, flexibility in composition and Tg, weather resistance, adhesion to polar and non-polar substrates, compatibility with polar polymers and inoganic components, and water resistance.
To provide the desired polymer compositions, the inventors have prepared polymers containing an acrylic backbone with less than 50 percent by weight synthetic wax monomer (“SWM”). The SWM contains crystalline polyethylene side chains and therefore is a crystallizable side chain monomer. One benefit from the copolymers of this invention is that one may achieve physical crosslinking through the association of one polymer component. This association can be crystallization or simply phase separation. The physical crosslinks that form are not permanent and can be “decrosslinked” by heating. Through such physical crosslinking, the backbone polymer matrix forms a network like structure, yet it can be fully decrosslinked when the polymer is heated above the melting temperature of the association blocks. Formation of a network structure helps to prevent loss of the physical properties when one has to reduce the molecular weight or Tg of the backbone polymer for processing or flexibility reasons.
In a first aspect, the present invention provides a polymer including as polymerized units:
A) from 1 to less than 50 percent by weight of a synthetic wax monomer of formula I:
wherein
R
1
is selected from H and CH
3
,
R
2
is selected from H and C
1
-C
5
alkyl,
R
3
is selected from H and CH
3
,
n=9-115, preferably 12-90, more preferably 15-50, and
m=0-1370, preferably 0-65, more preferably 0-50; and
B) from 50 to 99 percent by weight of at least one second monomer.
Previously, it has been difficult to prepare the polymer compositions described above. For example, the '450 patent described above utilized a one shot solution polymerization reaction to polymerize the monomers. For a solution process, it is desirable to be able to gradually add the SWM to the polymerization kettle because it is believed that the SWM will be more evenly incorporated into the polymer. Emulsion and suspension processes are desirable because they allow for a reduction of or elimination of organic solvents. The '450 patent did not address these concerns. Consequently, there is a continuing need for processes to prepare polymers containing SWMs.
The inventors have provided several approaches to preparing polymers containing SWMs. In one approach, a SWM slurry is prepared prior to polymerization of the SWM. The slurry may be used to prepare solution or suspension polymers. For a solution process, the slurry may be combined with additional monomers or organic solvent and co-fed to a reactor with an initiator. For a suspension process, the slurry is combined with an initiator and an aqueous solution and polymerized.
In a second aspect, the present invention provides a method of preparing a polymer from a slurry by: 1) forming a slurry by cooling a solution containing a synthetic wax monomer and a solvent; 2) forming a reaction mixture by admixing at least one second monomer with the slurry; and 3) polymerizing the reaction mixture in the presence of an initiator.
In a third aspect, the present invention provides a method of preparing a polymer from an emulsion by dissolving a synthetic wax monomer in at least one second monomer to form a solution, admixing water and at least one surfactant to provide a second solution, forming a monomer emulsion by admixing the first and second solutions, providing a reactor with heated water, and polymerizing the monomer emulsion by adding the monomer emulsion and at least one initiator to the reactor.
In a fourth aspect, the present invention provides a method of coating including applying a composition containing the polymer of the invention to a substrate.
As used throughout this specification, by the term (meth)acrylic acid is meant both acrylic acid and methacrylic acid. Likewise, as used throughout this specification, by the term (meth)acrylate is meant both acrylate and methacrylate esters.
The SWMs of this invention are C
24
to C
80
, preferably C
30
to C
50
ethylenically unsaturated (meth)acrylate monomers or ethoxylates thereof and are formed from C
24
to C
80
synthetic wax alcohols. Generally, the SWMs are formed by reacting a C
24
to C
80
synthetic wax alcohol or ethoxylate thereof with an alkyl (meth)acrylate in the presence of a zirconium c
Fu Zhenwen
Gore Robert Howard
Harbaugh Wolfersberger Martha Alice
Ibbitson Scott Alan
Merritt Richard Foster
Pezzuto Helen L.
Rohm and Haas Company
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