Polymeric magnet compound

This invention relates to a polymeric composition having ultraviolet light and heat resistance that can be molded into rubbery articles that can be magnetized. For instance, the rubbery compositions of this invention can be molded into magnetic seals for refrigerator or freezer doors. In such applications, the magnetic composition acts as a combination airtight gasket and magnetic closure device for the refrigerator or freezer. These polymeric magnetic compositions offer the advantage of being thermoplastic materials rather than thermosets. By virtue of being thermoplastics, they can be injection-molded into the desired form without the need for a curing step. Thus, rubbery magnetic compositions can be manufactured by a simpler, less costly process by utilizing the compositions of this invention. This invention more specifically discloses a polymeric magnet composition which is comprised of (1) from 5 to 19 parts by weight of a rubbery polymer which is comprised of repeat units which are comprised of (a) butyl acrylate, (b) at least one member selected from the group consisting of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) acrylonitrile, (d) styrene, (e) a crosslinking agent; (2) from 80 to 90 parts by weight of a magnetic powder; and (3) from 1 to 10 parts by weight of an internal lubricant.

BACKGROUND OF THE INVENTION 
Magnetic compositions that are semiflexible or rubbery in nature are used 
in a wide variety of applications. For instance, such materials are widely 
used as a combination airtight gasket and magnetic closure for 
refrigerator and freezer doors. They are also used in decorative magnets 
that will stick to a wide variety of metal (steel) objects. In any case, 
such semiflexible or rubbery magnets are typically comprised of a blend of 
a rubbery polymer and a magnetic powder which is formed into the desired 
shape and then cured. Such rubbery magnetic compositions also typically 
lack heat, ultraviolet light and outdoor weather resistance. 
Heat and light stabilizers can be employed to improve the heat and 
ultraviolet light aging characteristics of conventional blends of rubber 
with magnetic powder. However, the degree to which the aging 
characteristics of such blends can be improved by the addition of 
additives is limited. In fact, there is a demand for performance 
characteristics in such applications which heretofore has not been 
realized by the utilization of heat and light stabilizers. For instance, 
it would be highly desirable for rubbery magnets used in refrigerator and 
freezer doors to have a higher level of resistance to discoloration and 
cracking under conditions of heat and exposure to ultraviolet light 
experienced throughout the life of the refrigerator or freezer. Resistance 
to ultraviolet light is particularly important in out door applications, 
such as automotive seals and seals for metal framed doors and windows. 
U.S. Pat. No. 5,674,933 and U.S. Pat. No. 5,767,173 disclose a rubbery 
polymer which can be blended with polyvinyl chloride to make leathery 
compositions having good heat and ultraviolet light resistance, said 
rubbery polymer being comprised of repeat units which are comprised of (a) 
butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl 
acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) at 
least one member selected from the group consisting of methyl 
methacrylate, ethyl methacrylate, methyl acrylate and ethyl acrylate, (c) 
acrylonitrile, (d) styrene, (e) a surfactant selected from the group 
consisting of sulfonates and sulfate derivatives, (f) a dispersant 
selected from the group consisting of aromatic formaldehyde condensation 
products and polycarboxylates and (g) a crosslinking agent. U.S. Pat. No. 
5,380,785 discloses a similar type of rubbery polymer and U.S. Pat. No. 
5,616,651 discloses a technique for making a low odor version of the 
rubbery polymer by adding an aminoalcohol to the emulsion thereof. 
SUMMARY OF THE INVENTION 
The present invention relates to a polymeric composition having ultraviolet 
light and heat resistance that can be molded into rubbery articles that 
can be magnetized. For instance, the rubbery compositions of this 
invention can be molded into magnetic seals for refrigerator or freezer 
doors. In such applications, the magnetic composition acts as a 
combination airtight gasket and magnetic closure device for the 
refrigerator or freezer. These polymeric magnetic compositions offer the 
advantage of being thermoplastic materials rather than thermosets. By 
virtue of being thermoplastics, they can be injection-molded into the 
desired form without the need for a curing step. Thus, rubbery magnetic 
compositions can be manufactured by a simpler, less costly process by 
utilizing the compositions of this invention. 
This invention more specifically discloses a polymeric magnet composition 
which is comprised of (1) from 5 to 19 parts by weight of a rubbery 
polymer which is comprised of repeat units which are comprised of (a) 
butyl acrylate, (b) at least one member selected from the group consisting 
of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl 
acrylate, (c) acrylonitrile, (d) styrene, (e) a crosslinking agent; (2) 
from 80 to 90 parts by weight of a magnetic powder; and (3) from 1 to 10 
parts by weight of a internal lubricant. The magnetic compositions of this 
invention provide a higher level of resistance to heat and ultraviolet 
light than those made utilizing conventional blends of rubber and magnet 
powder. They also offer the advantage of being capable of being 
injection-molded into the desired form without the need for a curing step. 
DETAILED DESCRIPTION OF THE INVENTION 
The rubbery polymers of this invention are synthesized utilizing a free 
radical emulsion polymerization technique, such as the technique described 
in U.S. Pat. No. 5,380,785, U.S. Pat. No. 5,616,651, U.S. Pat. No. 
5,674,933 or U.S. Pat. No. 5,767,173. The teachings of U.S. Pat. No. 
5,380,785, U.S. Pat. No. 5,616,651, U.S. Pat. No. 5,674,933 and U.S. Pat. 
No. 5,767,173 are incorporated herein by reference in their entirety. 
Rubbery polymers of this type are sold by The Goodyear Tire & Rubber 
Company as Sunigum.RTM. rubber. These rubbery polymers are comprised of 
repeat units which are derived from (a) butyl acrylate, or optionally a 
mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 
40 percent 2-ethylhexyl acrylate, (b) methyl methacrylate, ethyl 
methacrylate, methyl acrylate or ethyl acrylate, (c) acrylonitrile, (d) 
styrene, (e) a crosslinking agent. The crosslinking agent is typically a 
multi-functional acrylate, a multi-functional methacrylate or 
divinylbenzene. Some specific examples of crosslinking agents which can be 
used include ethylene glycol methacrylate, divinylbenzene and 
1,4-butanediol dimethacrylate. 
Technically, the rubbery polymers used in the magnet compositions of this 
invention contain repeat units (chain linkages) which are derived from (a) 
butyl acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl 
acrylate containing up to about 40 percent 2-ethylhexyl acrylate, (b) 
methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl 
acrylate, (c) acrylonitrile, (d) styrene, (e) a crosslinking agent. These 
repeat units differ from the monomers that they were derived from in that 
they contain one less carbon-to-carbon double bond than is present in the 
respective monomer. In other words, a carbon-to-carbon double bond is 
consumed during the polymerization of the monomer into a repeat unit in 
the rubbery polymer. Thus, in saying that the rubbery polymer contains 
various monomers, in actuality means that it contains repeat units which 
are derived from those monomers. 
The rubbery polymers used in the magnet compositions of this invention will 
normally contain (a) from about 40 weight percent to about 80 weight 
percent butyl acrylate, or optionally a mixture of butyl acrylate and 
2-ethylhexyl acrylate containing up to 40 weight percent 2-ethylhexyl 
acrylate, (b) from about 5 weight percent to about 35 weight percent 
methyl methacrylate, ethyl methacrylate, methyl acrylate or ethyl 
acrylate, (c) from about 4 weight percent to about 30 weight percent 
acrylonitrile, (d) from about 3 weight percent to about 25 weight percent 
styrene, (e) from about 0.1 weight percent to about 6 weight percent of a 
surfactant selected from the group consisting of sulfonates and sulfate 
derivatives, (f) from about 0.1 weight percent to about 6 weight percent 
of a dispersant selected from the group consisting of aromatic 
formaldehyde condensation products and polycarboxylates and (g) from about 
0.25 weight percent to about 8 weight percent of a crosslinking agent. 
Such rubbery polymers will preferably contain (a) from about 50 weight 
percent to about 80 weight percent butyl acrylate, or optionally a mixture 
of butyl acrylate and 2-ethylhexyl acrylate containing up to about 40 
percent 2-ethylhexyl acrylate, (b) from about 3 weight percent to about 25 
weight percent of at least one member selected from the group consisting 
of methyl methacrylate, ethyl methacrylate, methyl acrylate and ethyl 
acrylate, (c) from about 6 weight percent to about 30 weight percent 
acrylonitrile, (d) from about 5 weight percent to about 18 weight percent 
styrene, (e) from about 0.3 weight percent to about 5 weight percent of a 
surfactant selected from the group consisting of sulfonates and sulfate 
derivatives, (f) from about 0.3 weight percent to about 5 weight percent 
of a dispersant selected from the group consisting of aromatic 
formaldehyde condensation products and polycarboxylates and (g) from about 
0.5 weight percent to about 4 weight percent of a crosslinking agent. 
The rubbery polymers used in the magnet compositions of this invention will 
more preferably be comprised of repeat units which are derived (a) from 
about 55 weight percent to about 75 weight percent butyl acrylate, or 
optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate 
containing up to about 40 percent 2-ethylhexyl acrylate, (b) from about 5 
weight percent to about 20 weight percent of at least one member selected 
from the group consisting of methyl methacrylate, ethyl methacrylate, 
methyl acrylate and ethyl acrylate, (c) from about 10 weight percent to 
about 25 weight percent acrylonitrile, (d) from about 8 weight percent to 
about 14 weight percent styrene, (e) from about 0.5 weight percent to 
about 4 weight percent of a surfactant selected from the group consisting 
of sulfonates and sulfate derivatives, (f) from about 0.5 weight percent 
to about 4 weight percent of a dispersant selected from the group 
consisting of aromatic formaldehyde condensation products and 
polycarboxylates and (g) from about 1 weight percent to about 3 weight 
percent of a crosslinking agent. The percentages reported in this 
paragraph are based upon the total weight of the rubbery polymer. 
The rubbery polymers used in the magnet compositions of the present 
invention are synthesized in an aqueous reaction mixture by utilizing a 
free radical polymerization technique. The reaction mixture utilized in 
this polymerization technique is comprised of water, the appropriate 
monomers, a suitable free radical initiator, a crosslinking agent, a 
surfactant selected from the group consisting of sulfonates and sulfate 
derivatives and a dispersant selected from the group consisting of 
aromatic formaldehyde condensation products and polycarboxylates. The 
reaction mixture utilized in this polymerization technique will normally 
contain from about 10 weight percent to about 80 weight percent monomers, 
based upon the total weight of the reaction mixture. The reaction mixture 
will preferably contain from about 20 weight percent to about 70 weight 
percent monomers and will more preferably contain from about 40 weight 
percent to about 50 weight percent monomers. 
The reaction mixtures utilized in carrying out such polymerizations will 
typically contain from about 0.1 phm (parts per hundred parts of monomer 
by weight) to about 5 phm of at least one member selected from the group 
consisting of metal salts of alkyl sulfates and metal salts of alkyl 
sulfonates and from about 0.1 phm to about 5 phm of at least one 
dispersant selected from the group consisting of aromatic formaldehyde 
condensation products and polycarboxylates. It is generally preferred for 
the reaction mixture to contain from about 0.25 phm to about 4.25 phm of 
the metal salt of the alkyl sulfonate or the metal salt of the alkyl 
sulfate and from about 0.25 phm to about 4.25 phm of the dispersant 
selected from the group consisting of aromatic formaldehyde condensation 
products and polycarboxylates. It is normally more preferred for the 
reaction mixture to contain from about 0.4 phm to about 3.5 phm of the 
metal salt of the alkyl sulfonate or the metal salt of the alkyl sulfate 
and from about 0.4 phm to about 3.5 phm of the dispersant selected from 
the group consisting of aromatic formaldehyde condensation products and 
polycarboxylates. 
The free radical polymerization technique utilized in the synthesis of the 
rubbery polymer is normally initiated by including a free radical 
initiator in the reaction mixture. Virtually, any type of compound capable 
of generating free radicals can be utilized as the free radical initiator. 
The free radical generator is normally employed at a concentration within 
the range of about 0.01 phm to about 1 phm. The free radical initiators 
which are commonly used include the various peroxygen compounds, such as 
potassium persulfate, ammonium persulfate, benzoyl peroxide, hydrogen 
peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl 
peroxide, decanoyl peroxide, lauryl peroxide, cumene hydroperoxide, 
p-menthane hydroperoxide, t-butyl hydroperoxide, acetyl peroxide, methyl 
ethyl ketone peroxide, succinic acid peroxide, dicetyl peroxydicarbonate, 
t-butyl peroxyacetate, t-butyl peroxymaleic acid, t-butyl peroxybenzoate, 
acetyl cyclohexyl sulfonyl peroxide, and the like; the various azo 
compounds, such as 2-t-butylazo-2-cyanopropane, dimethyl azodiisobutyrate, 
azodiisobutylronitrile, 2-t-butylazo-1-cyanocyclohexane, 
1-t-amylazo-1-cyanocyclohexane, and the like; and the various alkyl 
perketals, such as 2,2-bis-(t-butyl-peroxy)butane, and the like. 
Water-soluble peroxygen-free radical initiators are especially useful in 
such aqueous polymerizations. 
The emulsion polymerization used in the synthesis of the rubbery polymer is 
typically carried out at the temperature ranging between about 60.degree. 
F. (20.degree. C.) and 190.degree. F. (88.degree. C.). At temperatures 
above about 88.degree. C., alkyl acrylate monomers, such as butyl 
acrylate, have a tendency to boil. Thus, a pressurized jacket would be 
required for heating such alkyl acrylate monomers to temperatures in 
excess of about 88.degree. C. On the other hand, at polymerization 
temperatures of less than about 55.degree. C., a redox initiator system is 
required to insure satisfactory polymerization rates. 
The sulfonates and sulfate derivatives that are useful as surfactants are 
commercially available from a wide variety of sources. For instance, 
DuPont sells sodium alkylarylsulfonate under the tradename Alkanol.TM., 
Browning Chemical Corporation sells sodium dodecylbenzene sulfonates under 
the tradename Ufaryl.TM. Dl-85 and Ruetgers-Nease Chemical Company sells 
sodium cumene sulfonate under the tradename Naxonate Hydrotrope.TM.. Some 
representative examples of sulfonate surfactants which can be used include 
sodium toluene-xylene sulfonate, sodium toluene sulfonate, sodium cumene 
sulfonates, sodium decyldiphenylether sulfonate, sodium 
dodecylbenzenesulfonate, sodium dodecyldiphenylether sulfonate, sodium 
1-octane sulfonate, sodium tetradecane sulfonate, sodium pentadecane 
sulfonate, sodium heptadecane sulfonate and potassium toluene sulfonate. 
Metal salts of alkylbenzene sulfonates are a highly preferred class of 
sulfonate surfactant. The metal will generally be sodium or potassium with 
sodium being preferred. Sodium salts of alkylbenzene sulfonates have the 
structural formula: 
##STR1## 
wherein R represents an alkyl group containing from 1 to about 20 carbon 
atoms. It is preferred for the alkyl group to contain from about 8 to 
about 14 carbon atoms. 
The sulfonate surfactant can be a mixture of (mono)dialkylate ether 
disulfonates. The advantage of the disulfonate structure is that it 
contains two ionic charges per molecule instead of one as is the case with 
conventional alkyl sulfonate surfactants. Mixtures of (mono)dialkylate 
ether disulfates which are useful in the practice of this invention are 
commercially available from a wide variety of sources. For instance, Dow 
Chemical sells Dowfax.TM. alkylated disulfonated diphenyl oxides which are 
of the structural formula: 
##STR2## 
wherein R is an alkyl group which is typically --C.sub.6 H.sub.13, 
--C.sub.10 H.sub.21, --C.sub.12 H.sub.25 or --C.sub.16 H.sub.33. Sodium 
mono- and di-dodecyldiphenyloxide disulfonates are sold by American 
Cyanamid as DPOS-45 surfactants. Alpha-olefin sulfonate surfactants which 
are suitable for utilization in this invention are commercially available 
from Witco and Hoechst AG. 
The sulfate surfactants which are useful include metal salts of 
alkylsulfates having the structural formula ROSO.sub.3 X and metal salts 
of alkylethersulfates having the structural formula RO(CH.sub.2 CH.sub.2 
O).sub.n SO.sub.3 X, wherein X represents a group Ia metal, such as sodium 
or potassium. Sodium lauryl sulfate, sodium ethanolamine lauryl sulfate 
and triethanolamine lauryl sulfate are representative examples of 
commercially available sulfate surfactants. 
The dispersants utilized in the polymerization are normally either aromatic 
formaldehyde condensation products or polycarboxylates. The aromatic 
formaldehyde condensation products are normally polysulfonates which are 
the reaction product of aromatic compounds and formaldehyde. Such aromatic 
formaldehyde condensation product soaps can be made by a relatively simple 
process. For example, in such a process, 200 parts of naphthalene is 
reacted with 200 parts of 98 percent sulfuric acid for 5 hours at a 
temperature of about 165.degree.. The solution made is then subsequently 
cooled and diluted with 90 parts of water. Then, 107 parts of a 30 percent 
formaldehyde solution is added and the mixture is stirred for 20 hours at 
a temperature of about 80.degree. C. Toward the end of this reaction 
period, the mixture is gradually heated to 100.degree. C. Neutralization 
is subsequently carried out at 20.degree. C. to 25.degree. C. with about 
165 to 180 parts of a 25 percent ammonia solution. The neutralization 
product is then filtered and, if necessary, dried in a vacuum drier. 
Numerous variations of this synthesis are possible, and a wide range of 
aromatic compounds and their derivatives can react with aldehydes, ketones 
and compounds that eliminate aldehyde groups. For example, (a) dispersants 
produced by condensation of aromatic sulfonic acids and benzyl chloride or 
benzoin; (b) dispersants produced by condensation of various 
alkylarylsulfonic acids with a halogen arylsulfonic acid; and (c) 
dispersants produced by condensation of sulfonated phenols or 2-naphthols 
with formaldehyde and various nitrogen compounds. 
Some representative examples of aromatic formaldehyde condensation products 
are shown below: 
__________________________________________________________________________ 
Production Constituents 
Structural Units 
__________________________________________________________________________ 
Naphthalene + H.sub.2 SO.sub.4 + formaldehyde 
1 #STR3## 
Naphthalene + cresol + H.sub.2 SO.sub.4 + formaldehyde 
2 #STR4## 
Diphenyl ether + H.sub.2 SO.sub.4 + formaldehyde 
3 #STR5## 
Toluene + H.sub.2 SO.sub.4 + formaldehyde 
4 #STR6## 
Isopropylbenzene + H.sub.2 SO.sub.4 + formaldehyde 
5 #STR7## 
Cresol + H.sub.2 SO.sub.4 + formaldehyde 
6 #STR8## 
Phenol + formaldehyde + sodium sulfite 
7 #STR9## 
Cyclohexanone + formaldehyde + sodium sulfite 
8 #STR10## 
Phenol + H.sub.2 SO.sub.4 = formaldehyde 
9 #STR11## 
__________________________________________________________________________ 
The carboxylate is also a water-soluble polymeric dispersing agent. For 
instance, methacrylic acid can be polymerized to yield water-soluble 
homopolymer which can be employed as a carboxylate dispersant. Copolymers 
with maleic acid, acrylic acid-maleic acid, maleic acid-methylvinyl ether 
and diisobutylene-maleic acid (DIBMA) are also very useful in the practice 
of this invention. Carboxylate dispersants are commercially available from 
a variety of sources. 
The free radical emulsion polymerization utilized in synthesizing the 
rubbery polymer is typically conducted at a temperature which is within 
the range of about 10.degree. C. to about 95.degree. C. In most cases, the 
polymerization temperature utilized will vary between about 20.degree. C. 
and about 80.degree. C. The polymerization is carried out as a two-step 
batch process. In the first step, a seed polymer containing latex is 
synthesized. This is done by polymerizing (a) butyl acrylate, or 
optionally a mixture of butyl acrylate and 2-ethylhexyl acrylate 
containing up to about 40 percent 2-ethylhexyl acrylate, (b) at least one 
member selected from the group consisting of methyl methacrylate, ethyl 
methacrylate, methyl acrylate and ethyl acrylate, (c) acrylonitrile and 
(d) a crosslinking agent. 
The seed polymer containing latex is typically prepared by the 
polymerization of a monomer mixture which contains about 40 to about 90 
weight percent butyl acrylate, or optionally a mixture of butyl acrylate 
and 2-ethylhexyl acrylate containing up to about 40 percent 2-ethylhexyl 
acrylate, from about 5 to about 35 weight percent methyl methacrylate, 
ethyl methacrylate, methyl acrylate or ethyl acrylate, from about 2 to 
about 30 weight percent acrylonitrile and from about 0.25 weight percent 
to 6 weight percent of the crosslinking agent. It is typically preferred 
for the monomeric component utilized in the first step to include about 50 
weight percent to about 85 weight percent butyl acrylate, or optionally a 
mixture of butyl acrylate and 2-ethylhexyl acrylate containing up to about 
40 percent 2-ethylhexyl acrylate, from about 5 weight percent to about 30 
weight percent ethyl acrylate, ethyl methacrylate, methyl acrylate or 
methyl methacrylate, from about 4 weight percent to about 28 weight 
percent acrylonitrile and from about 0.5 weight percent to about 4 weight 
percent of the crosslinking agent. It is generally more preferred for the 
monomer charge composition used in synthesizing the seed polymer latex to 
contain from about 60 weight percent to about 80 weight percent butyl 
acrylate, or optionally a mixture of butyl acrylate and 2-ethylhexyl 
acrylate containing up to about 40 percent 2-ethylhexyl acrylate, from 
about 5 weight percent to about 25 weight percent methyl methacrylate, 
ethyl methacrylate, methyl acrylate or ethyl acrylate, from about 5 weight 
percent to about 25 weight percent acrylonitrile and from about 1 to about 
3 weight percent crosslinking agent. 
After the seed polymer latex has been prepared, styrene monomer, additional 
acrylonitrile monomer and additional crosslinking agent is added to the 
seed polymer containing latex. As a general rule, from about 4 parts by 
weight to about 30 parts by weight of styrene, from about 1 part by weight 
to about 20 parts by weight of additional acrylonitrile and from about 
0.01 to 2 parts by weight of the crosslinking agent will be added. In this 
second stage of the polymerization, it is preferred to add from about 6 
parts by weight to about 22 parts by weight of styrene, from about 3 parts 
by weight to about 12 parts by weight of acrylonitrile and from about 0.05 
parts by weight to 1 part by weight of the crosslinking agent. It is 
typically more preferred for from about 10 parts by weight to about 17 
parts by weight of styrene, from about 4 parts by weight to about 8 parts 
by weight of acrylonitrile and from about 0.1 parts by weight to about 0.5 
parts by weight of the crosslinking agent to be added to the seed polymer 
latex to initiate the second phase of the polymerization. 
A wide variety of crosslinking agents can be utilized in carrying out the 
polymerizations used in the synthesis of the rubbery polymer. Some 
representative examples of crosslinking agents which can be utilized 
include difunctional acrylates, difunctional methacrylates, trifunctional 
acrylates, trifunctional methacrylates and divinylbenzene. A crosslinking 
agent that has proven to be particularly useful is 1,4-butanediol 
dimethacrylate. 
In most cases, the polymerization will be continued until a high monomer 
conversion has been attained. After the polymerization has been completed, 
it is normally desirable to add an aminoalcohol to the emulsion to 
deodorize the latex. The aminoalcohol will generally be of the structural 
formula HO--A--NH.sub.2, wherein A represents an alkylene group which 
contains from 2 to about 20 carbon atoms. It is normally preferred for the 
aminoalcohol to contain from 2 to about 10 carbon atoms with amino 
alcohols which contain from 2 to about 5 carbon atoms being most 
preferred. Ethanolamine (HO--CH.sub.2 --CH.sub.2 --NH.sub.2) which is also 
known as 2-aminoethanol and 2-hydroxyethylamine is a representative 
example of a highly preferred aminoalcohol. Some additional examples of 
preferred aminoalcohols include 3-aminopropanol, 4-aminobutanol, 
2-amino-2-methyl-1-propanol, 2-amino-2-ethyl-1,3-propanediol, 
N-methyl-2,2-iminoethanol and 5-aminopentanol. 
This deodorizing step will be carried out under conditions which allow for 
the aminoalcohol to react with residual n-butylacrylate and acrylonitrile 
which is present in the emulsion. This reaction will proceed over a broad 
temperature range and the deodorizing step can be conducted at any 
temperature which is within the range of about 5.degree. C. and about 
95.degree. C. However, for practical reasons, the deodorizing step will 
normally be carried out at a temperature which is within the range of 
about 20.degree. C. to about 70.degree. C. Since the reaction is faster at 
higher temperatures, the amount of reaction time needed will decrease with 
increasing temperature. For instance, at a temperature of about 20.degree. 
C., a residence time in the deodorizing step of one to three days may be 
required. On the other hand, at a temperature of about 65.degree. C., only 
about two hours of reaction time is normally required. 
The amount of time required for the aminoalcohol to react with the residual 
n-butylacrylate monomer and residual acrylonitrile monomer will also 
depend upon the level of aminoalcohol utilized. As a general rule, from 
about 0.05 weight percent to about 2 weight percent of the aminoalcohol 
will be added, based upon the total weight of the emulsion. More 
typically, from about 0.1 weight percent to about 1.5 weight percent of 
the aminoalcohol will be added. It is normally preferred to utilize from 
about 0.3 weight percent to about 1 weight percent of the aminoalcohol. 
The rubbery polymer made by the two-step batch polymerization process is 
recovered from the emulsion (latex) after the optional deodorizing step. 
This can be accomplished by utilizing standard coagulation techniques. For 
instance, coagulation can be accomplished by the addition of salts, acids 
or both to the latex. 
After the rubbery polymer is recovered by coagulation, it can be washed to 
further reduce odors. This can be accomplished by simply pouring or 
spraying water on the rubbery polymer. The rubbery polymer can also be 
washed by putting it in a water bath which will further reduce odor. After 
being washed, the rubbery polymer is generally dried. 
It is sometimes advantageous to convert the dry rubbery polymer into a 
powder to facilitate its usage. In this case, it will be beneficial to add 
a partitioning agent to the rubbery polymer. Some representative examples 
of partitioning agents which can be employed include calcium carbonate, 
emulsion polyvinyl chloride and silica. Calcium carbonate is a highly 
desirable partitioning agent which can be utilized in such applications. 
The rubbery polymer is then blended with a magnet powder and an internal 
lubricant to make the magnet compositions of this invention. These blends 
can be prepared by blending the rubbery polymer, the magnet powder and the 
internal lubricant utilizing standard mixing techniques. It is highly 
preferred for the rubbery polymer to be in powdered form when blended into 
the magnet powder and the internal lubricant to make the rubbery magnet 
compositions of this invention. 
The magnetic compositions of this invention will typically contain from 
about 5 parts by weight to about 19 parts by weight of the rubbery 
polymer, from about 80 parts by weight to about 90 parts by weight of the 
magnetic powder and from about 1 part by weight to about 10 parts by 
weight of the internal lubricant. The magnetic compositions of this 
invention will preferably contain from about 7 parts by weight to about 13 
parts by weight of the rubbery polymer, from about 85 parts by weight to 
about 89 parts by weight of the magnetic powder and from about 2 parts by 
weight to about 8 parts by weight of the internal lubricant. The magnetic 
compositions of this invention will most preferably contain from about 7 
parts by weight to about 10 parts by weight of the rubbery polymer, from 
about 87 parts by weight to about 88 parts by weight of the magnetic 
powder and from about 3 parts by weight to about 6 parts by weight of the 
internal lubricant. Various colorants and/or pigments can also be added to 
the composition to attain a desired color. 
The magnet powder can be selected from a wide variety of iron, nickel and 
cobalt compounds that have ferromagnetic capacity. For instance, most of 
the ferrites of the general formula MeO.Fe.sub.2 O.sub.3, in which Me is a 
metal, can be used as the magnet powder. Barium ferrite, BaO:6Fe.sub.2 
O.sub.3, is a variation of the basic magnetic iron-oxide magnetite which 
has a hexagonal crystalline form and is very useful as the magnet powder. 
Powdered barium ferrite can be magnetically aligned and then compacted and 
sintered. It also has a very high uniaxial magnetic anisotropy capable of 
producing high values of coercive force (Hc). For a permanent magnet to 
retain its magnetization without loss over a long period of time, the 
coercive force should be as high as possible. Powdered strontium ferrite 
is also useful as the magnet powder. Alloys of nickel and iron, known as 
permalloy, have a maximum saturation magnetization in cases where the 
alloy contains about 50 percent nickel and 50 percent iron and are useful 
in powdered form as the magnet powder. The magnet powder will typically 
have a particle size which is within the range of about 0.1 to about 10 
microns. The magnet powder will more typically have a particle size which 
is within the range of about 1 to about 5 microns. 
The internal lubricant can be any of a wide variety of materials. For 
instance, the internal lubricant can be a non-polymeric or a polymeric 
processing aid. Some representative examples of internal lubricants that 
can be used include paraffin wax, stearic acid, a metal salt of stearic 
acid, polyethylene glycol, polypropylene glycol, low molecular weight 
polyethylene, amorphous polypropylene, a processing oil, a phthalate-ester 
plasticizer, epoxidized soy oil and ethylene vinyl acetate or an ethylene 
methacrylate. Low molecular weight polyethylene is highly preferred as the 
internal lubricant.

This invention is illustrated by the following examples which are merely 
for the purpose of illustration and are not to be regarded as limiting the 
scope of this invention or the manner in which it can be practiced. Unless 
specifically indicated otherwise, all parts and percentages are given by 
weight. 
EXAMPLE 1 
In this experiment, a rubbery polymer suitable for use in the magnet 
compositions of this invention was synthesized. The polymerization was 
conducted in a reactor having a capacity of 100 liters. The reactor was 
equipped with an axially flow turbine agitator which was operated at 110 
rpm (revolutions per minute). 
The reactor was charged with 74.6 kg (kilograms) of water, 0.92 kg of a 
half ester maleate soap (made with C.sub.16 fatty alcohol), 0.31 kg of a 
50 percent aqueous potassium hydroxide solution, 0.062 kg of sodium 
dodecylbenzene sulfonate, 18.0 kg of n-butylacrylate, 2.6 kg of 
acrylonitrile, 5.1 kg of methylacrylate, 0.38 kg of 1,4-butane diol 
dimethacrylate, 0.078 kg of t-dodecylmercaptan and 0.058 kg of potassium 
persulfate. A temperature of about 60.degree. C. was maintained throughout 
the polymerization. When a total solids content of about 25 percent was 
achieved, 0.025 kg of additional potassium persulfate was added. This 
first stage of the polymerization was carried out for a period of about 
21/2 hours. This first stage polymerization resulted in the production of 
a seed polymer latex which was used in the second step of the 
polymerization. 
In the second step of the polymerization, 1.47 kg of acrylonitrile, 3.4 kg 
of styrene, 0.050 kg of divinylbenzene and 0.009 kg of t-dodecylmercaptan 
were charged into the reactor containing the seed polymer latex. The 
polymerization proceeded until a solids content of about 30 percent was 
attained. The latex produced was white in color, had a pH of about 6.5, 
had a Brookfield viscosity of about 6 centipoise (CPS), a surface tension 
of about 49 dyne per centimeter and a particle size of about 80 
nanometers. However, the latex had a residual acrylonitrile concentration 
of about 1480 ppm (parts per million), a residual n-butylacrylate 
concentration of about 325 ppm and had a strong odor. Residual monomer 
levels were determined by gas chromatography. 
The latex made was subsequently coagulated and a dry rubber was recovered. 
The dry rubber was determined by gas chromatography to contain 24 ppm of 
residual acrylonitrile and 300 ppm of n-butylacrylate. The dry rubber had 
an undesirable odor. 
The rubbery polymer made was also tested for fogging characteristics. In 
the procedure used, the condensate from a 10-gram sample maintained at 
100.degree. C. was captured for 16 hours on a cooled aluminum foil which 
was supported on a glass plate. After the 16 hour period, it was 
determined gravimetrically that about 4 mg of condensate had formed. 
EXAMPLE 2 
In this experiment, a rubbery polymer was synthesized utilizing a procedure 
similar to the procedure employed in Example 1. This polymerization was 
conducted in a reactor having a capacity of 100 liters. The reactor was 
equipped with an axially flow turbine agitator which was operated at 110 
rpm. The reactor was initially charged with 70.92 kg of water, 0.87 kg of 
dodecanol monomaleate, 0.40 kg of an aqueous 50 percent solution of 
potassium hydroxide, 0.06 kg of sodium dodecylbenzene sulfonate, 0.06 kg 
of sodium pyrophosphate, 0.05 kg of triethanol amine, 22.13 kg of n-butyl 
acrylate, 2.60 kg of acrylonitrile, 1.30 kg of methyl methacrylate, 0.65 
kg of 1,4-butanediol dimethacrylate, 0.08 kg of t-docecylmercaptan and 
1.56 kg of a 5 percent solution of potassium persulfate. A temperature of 
about 35.degree. C. was maintained throughout the polymerization. When a 
total solids content of about 24 percent was achieved, 0.52 kg of 
additional potassium persulfate solution was added. This first stage of 
the polymerization was carried out for a period of about 21/2 hours. This 
first stage polymerization resulted in the production of a seed polymer 
latex which was used in the second step of the polymerization. 
In the second step of the polymerization, 1.49 kg of acrylonitrile, 3.47 kg 
of styrene, 0.050 kg of divinylbenzene and 9.3 mg of t-dodecylmercaptan 
were charged into the reactor containing the seed polymer latex. The 
polymerization temperature was then raised to 70.degree. C. and the 
polymerization was allowed to continue. After the polymerization was 
completed, the latex made was coagulated and a dry rubber was recovered. 
EXAMPLE 3 
In this experiment, a rubbery polymer was made in a 2-liter glass reactor. 
In the procedure employed, 1126 g of water, 5.93 g of a 50 percent aqueous 
potassium hydroxide solution, 14.0 g of hexadecyl monomaleate, 1.0 g of a 
30 percent solution of sodium dodecylbenzene sulfonate, 1.0 g of sodium 
pyrophosphate, 231 g of n-butyl acrylate, 105 g of acrylonitrile, 42 g of 
2-ethylhexylacrylate, 42 g of methyl acrylate, 8.4 g of 1,4-butanediol 
dimethacrylate, 0.84 g of t-dodecylmethacrylate, 8.3 g of a 5 percent 
aqueous solution of triethanol amine and 24.9 g of a 5 percent aqueous 
solution of potassium persulfate were initially charged into the reactor. 
A temperature of about 35.degree. C. was maintained during the first stage 
of the polymerization. When a solids content of about 20 percent was 
reached, the reaction temperature was increased to about 60.degree. C. and 
24 g of additional acrylonitrile, 56 g of styrene, 0.96 g of 
divinylbenzene and 0.16 g of t-dodecylmercaptan were charged into the 
reactor. After the polymerization was completed, the latex made was 
coagulated and a rubber was recovered. 
EXAMPLE 4 
In this experiment, a rubbery polymer was made in a 2-liter glass reactor. 
In the procedure employed, 1126 g of water, 5.93 g of a 50 percent aqueous 
potassium hydroxide solution, 14.0 g of hexadecyl monomaleate, 1.0 g of a 
30 percent solution of sodium dodecylbenzene sulfonate, 1.0 g of sodium 
pyrophosphate, 168 g of n-butyl acrylate, 105 g of acrylonitrile, 105 g of 
2-ethylhexylacrylate, 42 g of methyl acrylate, 6.3 g of 1,4-butanediol 
dimethacrylate, 0.44 g of t-dodecylmethacrylate, 8.3 g of a 5 percent 
aqueous solution of triethanol amine and 24.9 g of a 5 percent aqueous 
solution of potassium persulfate were initially charged into the reactor. 
A temperature of about 35.degree. C. was maintained during the first stage 
of the polymerization. When a solids content of about 20 percent was 
reached, the reaction temperature was increased to about 60.degree. C. and 
24 g of additional acrylonitrile, 56 g of styrene, 0.96 g of 
divinylbenzene and 0.16 g of t-dodecylmercaptan were charged into the 
reactor. After the polymerization was completed, the latex made was 
coagulated and a rubber was recovered. 
EXAMPLE 5 
In this experiment, the latex made in Example 1 was deodorized before being 
coagulated. This was accomplished by adding 0.5 weight percent (based upon 
the total weight of the latex) of ethanolamine to the latex at room 
temperature (about 22.degree. C.). After one day, the level of residual 
acrylonitrile dropped from 1480 ppm to 51 ppm and the level of residual 
n-butylacrylate dropped from 325 ppm to 30 ppm. After three days, the 
level of residual n-butylacrylate became undetectable. 
The deodorized latex was subsequently coagulated and a dry rubber was 
recovered. Residual levels of acrylonitrile and n-butylacrylate were too 
low to be detectible by gas chromatography in the dry rubber. The dry 
rubber recovered did not have an undesirable odor. 
EXAMPLE 6 
In this experiment, the procedure described in Example 1 was repeated 
except that the 0.92 kg of half ester maleate soap was replaced with 0.612 
kg of an aromatic formaldehyde condensation product soap. The procedure 
employed in this experiment also differed from the procedure described in 
Example 1 in that the level of sodium dodecyl benzene sulfonate was 
increased to 0.3 kg. The aromatic formaldehyde condensation product soap 
utilized in this experiment was the sodium salt of the condensation 
product of naphthalene sulfonic acid and formaldehyde. It had a molecular 
weight which was within the range of about 1000 to about 5000 and can be 
represented by the structural formula: 
##STR12## 
The rubbery polymer made was then tested for fogging characteristics. In 
the procedure used, the condensate from a 10-gram sample maintained at 
100.degree. C. was captured for 16 hours on a cooled aluminum foil which 
was supported on a glass plate. After the 16 hour period, it was 
determined gravimetrically that 0.3 mg of condensate had formed. Thus, the 
fogging characteristics of the rubbery polymer made in this experiment 
were much better than the fogging characteristics of the rubbery polymer 
synthesized in Example 1 where 4.0 mg of condensate were collected in the 
fogging test. In other words, the rubbery polymer made in this experiment 
generated less than 10 percent of the amount of fog generated with the 
rubbery polymer of Example 1. 
EXAMPLE 7 
In this experiment, the procedure described in Example 1 was repeated 
except that the 0.92 kg of half ester maleate soap was replaced with 0.765 
kg of an Sokalan polycarboxylate soap. The procedure employed in this 
experiment also differed from the procedure described in Example 1 in that 
the level of sodium dodecyl benzene sulfonate was increased to 0.306 kg. 
The rubbery polymer made was then tested for fogging characteristics. In 
the procedure used, the condensate from a 10-gram sample maintained at 
100.degree. C. was captured for 16 hours on a cooled aluminum foil which 
was supported on a glass plate. After the 16 hour period, it was 
determined gravimetrically that 0.4 mg of condensate had formed. Thus, the 
fogging characteristics of the rubbery polymer made in this experiment 
were much better than the fogging characteristics of the rubbery polymer 
synthesized in Example 1. 
EXAMPLE 8 
In this experiment, a magnet composition was made by blending 11.5 parts of 
Sunigum rubber, 85 parts of strontium ferrite powder, 1.5 part of low 
molecular weight polyethylene and 2 part of ethylene methacrylate. The 
strontium ferrite powder had a specific gravity of 5.1 and a particle size 
of 1.5 microns. The low molecular weight polyethylene had a density of 
0.91, a softening point of 102.degree. C. and a viscosity at 140.degree. 
C. of 180 cps. The ethylene methacrylate copolymer had a melt index of 135 
g/10 min and contained 21.5 weight percent methyl acrylate. The blend was 
internally mixed at a temperature of 175.degree. C. at 50 rpm in a Haake 
Rheocord 90 laboratory size internal mixer for 5-10 minutes. The blend was 
then passed through a midget mill at 200.degree. C. and cut into 5 cm by 5 
cm pieces having a thickness of about 1 mm. 
One of the pieces was brought into contact with a strong magnet from a 
medical NMR device. The magnet composition became magnetized and the 
magnetic charge was strong enough for the square of magnetic composition 
to support its own weight by adhering to the bottom side of a metal 
heating/cooling duct. On retesting 2 months later, the piece of magnetic 
composition still maintained a magnetic charge which was strong enough to 
support its own weight by sticking to the bottom side of the metal 
heating/cooling duct. 
EXAMPLE 9 
In this experiment, a magnet composition was made by blending 8.8 parts of 
Sunigum rubber, 87.7 parts of strontium ferrite powder and 3.5 parts of 
low molecular weight polyethylene. The strontium ferrite powder had a 
specific gravity of 5.1 and a particle size of 1.5 microns and the low 
molecular weight polyethylene had a density of 0.91, a softening point of 
102.degree. C. and a viscosity at 140.degree. C. of 180 cps. The blend was 
internally mixed at a temperature of 175.degree. C. at 50 rpm in a Haake 
Rheocord 90 laboratory size internal mixer for 5-10 minutes. The blend was 
then passed through a midget mill at 200.degree. C. and cut into 5 cm by 5 
cm pieces having a thickness of about 1 mm. 
One of the pieces was brought into contact with a strong magnet from a 
medical NMR device. The magnet composition became magnetized and the 
magnetic charge was strong enough for the square of magnetic composition 
to support its own weight by adhering to the bottom side of a metal 
heating/cooling duct. On retesting 2 months later, the piece of magnetic 
composition still maintained a magnetic charge which was strong enough to 
support its own weight by sticking to the bottom side of the metal 
heating/cooling duct. The magnetic charge appeared to be stronger than the 
magnetic charge on the magnet made in Example 8. 
Comparative Example 10 
In this experiment, a magnet composition was made by blending 18 parts of 
Sunigum rubber, 80 parts of strontium ferrite powder, 1 part of low 
molecular weight polyethylene and 1 part of ethylene methacrylate. The 
strontium ferrite powder had a specific gravity of 5.1 and a particle size 
of 1.5 microns. The low molecular weight polyethylene had a density of 
0.91, a softening point of 102.degree. C. and a viscosity at 140.degree. 
C. of 180 cps. The ethylene methacrylate copolymer had a melt index of 135 
g/10 min and contained 21.5 weight percent methyl acrylate. The blend was 
internally mixed at a temperature of 175.degree. C. at 50 rpm in a Haake 
Rheocord 90 laboratory size internal mixer for 5-10 minutes. The blend was 
then passed through a midget mill at 200.degree. C. and cut into pieces 
which were about 5 cm by 5 cm having a thickness of about 1 mm. 
One of the pieces of magnet composition was brought into contact with a 
strong magnet from a medical NMR device. The magnet composition became 
slightly magnetized. However, the magnetic charge was not strong enough 
for the piece of magnet composition to stick to the bottom side of a 
heating/cooling duct. This example shows that a 80 percent loading of 
strontium ferrite powder is not high enough to attain good magnetic 
properties. 
While certain representative embodiments and details have been shown for 
the purpose of illustrating the subject invention, it will be apparent to 
those skilled in this art that various changes and modifications can be 
made therein without departing from the scope of the subject invention.