Amino-acrylate polymers and method

An amino-acrylate polymer is prepared by the reaction of an aliphatic hydroxyl polyacrylate monomer, like pentaerythritol triacrylate, with a polyamine like a hexyldiamine to provide a rigid fast gelling and curing polymer, which polymer may be modified with resin modifiers. The amino-acrylate polymer may be used in the preparation of composite structures with fibers and filler materials.

BACKGROUND OF THE INVENTION 
Acrylate monomers have been widely used with peroxide and radiation curing 
systems to provide acrylate polymers. In particular, di-functional methyl 
methacrylate monomers, alone or with mono-functional reactive diluent 
acrylate monomers, have been used with benzoyl peroxide to provide hard 
acrylate polymers used for flooring and casting applications. However, 
typically the curing time is 10 to 30 minutes, depending on the polymer 
thickness, and often such polymers are brittle and are associate with a 
residual odor. 
Acrylate monomers and acrylate oligomers, such as epoxy, urethane and 
elastomeric acrylate oligomers, when used with photo initiators, will cure 
rapidly in the presence of ultra violet (UV) light. However, while curing 
times are often quite fast, high-intensity UV light is required, and the 
thickness of the films produced and the colors of the resulting cured 
polymers often cause acceptance problems. 
It is desirable to provide hard, transparent, high-impact acrylate polymers 
with fast gel and cure times and which are easily prepared and 
particularly useful in composite structures. 
SUMMARY OF THE INVENTION 
The invention relates to a method of preparing acrylate polymers with fast 
gel and curing times, and which acrylate polymers may be prepared as 
transparent, hard, high-impact or modified acrylate polymers. In 
particular, the acrylate polymers of the invention are prepared from high 
functional acrylate monomers and polyamines in a rapid, simple, fast, 
non-catalyzed reaction method. 
The invention comprises a method of producing acrylate polymers by 
reacting, in a liquid reaction mixture, an aliphatic acrylate monomer 
having three or more, such as four or five, acrylate ester groups, and 
which acrylate monomer has at least one reactive hydroxyl group with an 
alkyl-substituted aliphatic polyamine. 
Typically, the high functionality-OH acrylate monomer comprises a liquid 
which is reacted at room temperature, 15.degree.-25.degree. C., in 
approximate stoichiometric amounts, with a liquid polyamine, without the 
need for catalyst or curing agents or systems. The components of the 
reaction mixture may be modified by varying the polyamine quantities and 
compounds to control the resulting gel and cure times and to provide 
acrylate polymers of selected and controlled hardness; for example, but 
not to be limited to, Shore D hardness of about 70 to 90 in 1 to 3 
minutes. 
The method of preparation merely requires the admixture of the acrylate 
monomer and the polyamine, alone or in the presence of a liquid, reactive 
or nonreactive diluent. The method provides for gel and cure times of less 
than about 5 minutes, and more typically, less than about 1 or 2 minutes, 
to a gel condition or a tack-free surface condition. 
The reaction mixture may be used to produce a non-brittle, 
clear-transparent acrylate polymer or used with varying amounts of filler 
materials; e.g. up to 50 percent by weight of the composition, such as 0 
to 35 percent by weight, as desired. The filler materials may include 
particulate materials, alone or in combination, such as: fiber, like 
chopped glass fibers, in a spray operation, or other reinforcing fibers; 
or with inert fillers, like calcium carbonate; metal oxides, like titanium 
dioxide; pigments; coloring agents; mica; as well as granite, marble or 
stone chips or dust, for example, to produce sinks and counter tops with 
higher gloss, toughness, chemical resistance and UV stability than 
comparable polyester resin sinks and counter tops. The acrylate polymers 
may be used alone or with the employment of various unsaturated polyester 
resins. Other fillers include, but are not limited to: flame and scratch 
retardants, like aluminum trihydrate and halogenated compounds; 
plasticizers; resins; waxes; and other polymers and resins. 
The reaction mixture may be used as a gel coat in composite structures, and 
applied in a film, spray, cast, coated or molded application, e.g. RIM 
application. It has been found that the high-functional amino-acrylate 
polymer produced is not brittle, is UV stable and suitable for outdoor 
application, and has good wet out characteristics when combined with glass 
fibers, such as sprayed in a two-component machine which includes a 
fiberglass chopper. Further, unlike methyl methacrylate polymers, the 
acrylate polymers are not inherently brittle and have a high-impact 
strength similar to polyurethanes or polycarbonates. 
The hydroxyl high functional polyacrylate-hydroxy monomer may comprise 
pentaerythritol triacrylate as one preferred compound; however, 
pentaerythritol tetracrylate and dipentaerythritol pentacrylate may also 
be used with fast reaction times. Other polyacrylate polyhydroxy monomers 
include alkoxylated tri-, treta- and pentamonomers, like ethoxylated 
pentaerythritol tetracrylate. The method requires that the acrylate 
monomer be a tri- or higher-functional acrylate with at least one reactive 
hydroxy group, since related compounds, such as trimethyl propyl 
triacrylate provides no reaction with the polyamine. When 
hydroxyl-containing lower functional acrylates were used in the reaction, 
such as hydroxyethyl diacrylate and hydroxypropyl diacrylate, they were 
not found suitable. These diacrylate monomers provided an exothermic 
reaction, but the resulting polymers did not cure in 24 hours, which 
indicates the hydroxyl groups are reacting but much higher functionality 
is required. 
It has been found that the acrylate polymer may be modified by the use of 
additional hydroxyl-containing compounds to control gel and cure times and 
particular polymer hardness, such as the use of diol and triol 
caprolactones to provide a faster reaction time. 
The alkyl-substituted aliphatic polyamine used in the method comprises a 
methyl-substituted aliphatic (e.g., hexyl) polyamine, like a diamine, and 
more particularly and preferred, a methylcyclohexyl diamine, such as 
3-aminomethyl-3,5,5-trimethylcyclohexylamine (known as VESTAMIN.RTM. IPD 
isophorone diamine, a trademark of Huls AG). The IPD provides for a hard, 
clear acrylate polymer with the pentaerythritol triacrylate (PETA). 
Trimethyl hexamethylene diamine (known as VESTAMIN.RTM. TMD, a branched 
aliphatic diamine, a trademark of Huls AG) may also be used as the 
aliphatic (hexyl) polyamine, alone or in combination with the IPD. The TMD 
acrylate polymer has less hardness than the IPD polymer and thus may be 
combined with the IPD as a hardener monomer modifier. 
Other suitable polyamines for use in the reaction mixture include an 
alkyl-substituted benzyl diamine, like meta-xylylenediamine. The reactive 
polyamines reacted with the high functionality polyacrylate-hydroxyl 
monomers may be used alone or in combination to provide a polymer of 
selected gel and cure times, hardness and other properties. Other 
aliphatic diamines and triamines, like the Jeffamines, were tried; 
however, the reaction times were too long. 
Further, it has been found that the use of water in the reaction mixture 
results in accelerated gel and cure times of typically to less than 1 
minute; e.g., less than 10 to 15 seconds, by, for example, the use of 
about 0.5 to about 5.0 percent of water with the PETA and IPD reaction 
mixture. 
Also, it has been discovered that the employment of modifying resins in the 
reaction mixture provides modified resin-acrylate polymers of desireable 
properties. In particular, modifying amounts, for example 0 to 50 percent 
by weight, such as 5 to 25 percent by weight, may be incorporated in the 
reaction mixture. Suitable thermosetting resins include, but are not 
limited to: melamine-formaldehyde; urea-formaldehyde; phenol-formaldehyde; 
phenol-furfural; as well as various epoxy resins, alone or in selected 
combinations. For example, 5 to 15 percent of melamine-formaldehyde resin 
in a PETRA-IPD or TMD mixture results in a flexible polymer, while the 
addition of epoxy resins provides excellent resin-acrylate polymeric films 
and often accelerates cure times of the reaction mixture. 
Thus, the method in one preferred embodiment is the reaction of PETA with 
IPD, and optionally, as required, with modifying amounts for 0 to 50 
present by weight, e.g. 5 to 25 percent, of caprolactones or hexyl 
polyamines to provide softer acrylate polymers.