FR1464337A - Compatible blend of an epoxy resin and a copolymer of ethylenically unsaturated materials - Google Patents

Description

Compatible mixture of an epoxy resin and a copolymer of unsaturated materials
ethylenically.

The present invention relates to room temperature compatible blends of an epoxy resin with copolymers of polymerized ethylenically unsaturated materials, such blends being useful in cast compositions and coating compositions. The resin systems of the present invention are characterized by exceptional compatibility and exceptionally low viscosities which allow handling in the absence of solvent or in the presence of minimum proportions of solvent.

Although attempts have been made in the prior art to combine addition copolymers with an epoxy resin, these efforts have not been successful, for various reasons.

First, excessive proportions of organic solvent were always necessary to keep the addition copolymer in solution compatible with the epoxy resin. As a result, cast resins could not be prepared because solvent removal results in shrinkage, and the disadvantages of excessive amounts of solvent in solution coating compositions are too well known to require comment. In addition, a significant drawback of systems produced by blending pre-formed addition copolymers with epoxy resins is the cloudy gel structure commonly encountered after the loss of some solvent, due to the incompatibility of the compounds. resins that are combined in the solution.

Although there are completely compatible systems, the majority of systems exhibit this incompatible nature. This gel results in very slow solvent removal and a cheese-like texture instead of a tough homogeneous film. Many of the systems which previously seemed incompatible are compatible when the same materials are combined as described herein.

Researchers have already tried to incorporate the desired proportion of vinyl monomers into the epoxy resin as well, but these mixtures, when catalyzed for curing, lack stability at room temperature.

When the monomers are polymerized in situ, the viscosity increases too rapidly and, therefore, practical handling has required that the mixtures of vinyl monomers and epoxy resin be used quickly and be cured directly and completely in their final position.

According to the present invention, compatible mixtures are formed by maintaining the epoxy resin in the liquid phase and under conditions suitable to cause addition polymerization of ethylenically unsaturated materials, and adding in small amounts the ethylenically unsaturated material. at a low rate relative to the rate of polymerization in order to avoid any noticeable increase in the concentration of unreacted monomer.

It appears that the polymerization of the unsaturated monomers in a state of high dilution causes the polymerization reaction to be governed by the presence of the epoxy resin, causing the polymer chair to grow around and become entangled in a great measure with the epoxy molecule in a natural way, achieving a very intimate mixture. There is also the possibility of a telomerization action causing chain blockage.

On the contrary, when the proportion of unreacted unsaturated monomers in the epoxy resin system increases to a value of 3 to 5% or greater, at least part of the unsaturated monomers is protected.
against the dominant influence of the epoxy resin and polymerization leads to a rapid increase in viscosity and, in more severe cases, to the production of incompatible polymer fragments.

With respect more particularly to the process of the present invention, an epoxy resin, preferably an epoxy resin which is normally liquid at room temperature, is maintained in the liquid phase and under temperature conditions promoting addition polymerization. A mixture of ethylenically unsaturated polymerizable materials, preferably dissolved in a small amount of the epoxy resin to facilitate the addition, is added in small amounts to the epoxy resin and, in the presence of a free radical producing polymerization catalyst. , it is made to react quickly after the addition. The rapid reaction is ensured by an appropriate choice of catalyst, a high reaction temperature and a suitable concentration of the catalyst, and the rate of addition is chosen so as to minimize the accumulation of monomers due to the reaction rate which is obtained.

The monomers used have, in most cases, a very low viscosity, while the epoxy resin always has a higher viscosity.

The reason for mixing some of the epoxy resin with the monomers is to adjust and control the final viscosity by maintaining the proper conditions of concentration in the reaction zone. As more monomers are added, the epoxy resin present in the reaction zone is diluted with the growing vinyl or acrylic resin. The addition of epoxy resin during the reaction regulates this rate of dilution and affects the viscosity. The addition of the epoxy resin to the monomers to be introduced is not necessary, but constitutes a means of adjustment. The epoxy resin could be added separately, or it could be present entirely in the reaction zone from the start, depending on the desired end result.

The temperature of the epoxy resin should be maintained at a level leading to addition copolymerization of the unsaturated materials therebetween. These temperatures are very classic and we will not study them at length, temperatures of 80 to 120 ° C. being very common. In addition, in case of the presence of materials which are reactive - with the epoxy resin to cause its curing or crosslinking, the temperature should be kept below that which will cause a reaction with the oxirane functionality of the epoxy resin,
As specified above, the addition copolymerization reaction takes place in the presence of a polymerization catalyst which produces Vibres groups. This catalyst can be incorporated in any desired manner, for example
in epoxy resin, in the mixture of materials
polymerisables added to epoxy resin, or in
a separate stream when the materials polymerize
sands are added to the epoxy resin.

Polymerization catalysts producing
free radicals which are considered according to the
present invention are too well known to those skilled in the art to require discussion
push. Essentially, two types of such cat
lysers are of general use and are said to be the type
peroxide and the azo type. An example of
first type is benzoyl peroxide, and
azodiisobutyronitrile is an example of the second
type. In choosing a catalyst, its tempera
ture of activity is of primary interest.

Ethylenically unsaturated materials
polymerizable materials useful in the present invention
include a large class of materials,
and they are chosen according to the properties that we
desires for the final product. So we can choose
a single ethylenically unsaturated material
polymerizable or a mixture of such materials.

Also, we can use materials that have
a reactive functional group in addition to the
ethyienic group. This grouping functions
tional can be reactive with epoxy resin
to achieve thermosetting.

Ethylenically unsaturated materials which
preferred are monovinyl compounds,
such as styrene, vinyl-toluene, chloride
vinyl and vinyl acetate; compounds not
saturated such as esters of acrylic acids and
methacrylic, for example methyl acrylate,
ethyl acrylate, butyl acrylate, metha
methyl crylate, ethyl methacrylate, Ie
butyl methacrylate, etc., and esters of
maleic, fumaric and itaconic acids, as well
than the acids or anhydrides themselves.

To allow thermosetting of
resin systems of the present invention,
it is advantageous to include in the copolymer
ethylenically unsaturated materials which
also have Uls- reactive functional group with
the oxirane group of the epoxy resin. Of
examples of this group of materials are alcohols
ethylenically unsaturated such as ally alcohol
lic, 2-hydroxy-ethyl methacrylate,
cyclol and methylol-amides such as methylol
acrylamide. Preferably, these materials are
used in small proportions and the
reaction are such that they favor copoly
addition merization while avoiding the reaction
of the functional group with the epoxy resin.

In addition, and although the resin system of the
present invention is mainly envisaged
to be used and hardened internally, various
other resinous materials can be mixed
with him to modify the properties and Ion perform
a curing reaction between the copolymer
and epoxy resin. Thus, we could include
urea-formaldehyde resins or melamine formaldehyde resins as a hardener, but this is not essentially contemplated.

The epoxy resin which is used in the present invention should be maintained in a liquid phase at the time of addition in small amounts of the ethylenically unsaturated polymerizable material. The epoxy resins primarily contemplated are those which are normally liquid at room temperature, but the invention includes the use of normally solid epoxy resins which are liquid at the temperatures used for the addition copolymerization reaction. These epoxy resins preferably have a 1,2-epoxy equivalence of greater than 1.2, especially greater than 1.4, and preferably about 2.0. An example of the epaxy resins useful in the present invention is bisphenol A 2,2'-bis (hydroxyphenylpropane) substantially diglycidyl ether having a molecular weight of about 360 and an epoxy equivalent weight of about 175.

Also, and although the invention relates to resin mixtures having a solids content of 100%, low levels of an organic or other solvent may be included if desired.

The materials of the present invention are very useful as casting materials when 100% solids resins are essential to minimize shrinkage. These materials are also useful as coatings and can be pigmented and applied with little or no solvent at all, providing thicker or more continuous films without the problems associated with solvent coatings. Even when a solvent is present, the fact that only minimal amounts of solvent need to be evaporated allows the application of thicker coatings and minimizes solvent costs. The problems of fire hazard and noxious vapors which are associated to a greater or lesser extent with any solvent use are also minimized. These systems are also useful in special missile and spacecraft applications, possessing excellent thermal control properties as a binder in ablation susceptible coatings and the like.

The following non-limiting examples will clearly show how the present invention can be implemented.

Example 1. - In a round-bottomed glass flask, with a capacity of 3 liters, and with 3 nozzles, equipped with a thermometer, a stirrer, a heater, a reflux condenser 333 g of the normally liquid diglycidyl ether of bisphenol A having an average molecular weight of about 350 and an epoxy equivalent weight of 175 approx. While bubbling an inert gas, the ether is heated to a temperature of 107 ° C. and a solution comprising 375 g of butyl methacrylate is added dropwise to the heated ether. 125 g of butyl acrylate, 167 g of the diglycidyl ether of bisphenol A and 5 g of benzoyl peroxide, the addition being carried out over a period of 30 min.

Once the addition is complete, the temperature is brought to 116 ° C. and this temperature is maintained for 45 to 60 minutes. The mixture is cooled and filtered. The final product contains 50% by weight of epoxy resin and 50% by weight of polymerized ethylenically unsaturated material.

Example 2. - In a round-bottomed glass flask, with a capacity of 3 liters, and with 3 nozzles, equipped with a thermometer, a stirrer, a heater, a reflux condenser , a device for regulating the admission of monomers and a feed tube for an inert gas, 333 g of the diglycidyl ether of 1,4-butanediol, having an average molecular mass, are poured in of about 268 and an epoxy equivalent weight of about 134. While bubbling an inert gas, the ether is heated to a temperature of 107 ° C. and a solution comprising 200 g of butyl acrylate, 150 g of methyl methacrylate, 100 g of 100 g of sodium is added dropwise to the heated ether. styrene, 50 g of maleic anhydride, 7.5 g of benzoyl peroxide and 167 g of the diglycidyl ether of 1,4-butanediol, the addition being carried out over a period of 30 min. Once the addition is complete, the temperature is brought to 116 ° C. and this temperature is maintained for 30 min. The mixture is cooled and filtered. The final product contains 50% by weight of epoxy resin and 50% by weight of the copolymer formed by the non-saturated materials.

The above examples are given by way of illustration, but the invention is in no way limited by them. Thus, and according to the invention, one could use different copolymerizable ethylenically unsaturated materials, different epoxy resins or mixtures of such resins, and different reaction temperatures.

Also, the free radical producing polymerization catalyst could be included in the epoxy resin rather than in the solution added in small amounts as described in the examples. In addition, the proportions by weight of epoxy resin to ethylenically unsaturated polymerized material are not limited to those shown in the examples.

Thus, the percentages by weight of epoxy resin and of copolymerized ethylenically unsaturated material could range from 95% to 5% and from 5% to 95% by weight, relative to the weight of the non-volatile solids, depending on what. It is desired, but preferably amounts of 10 to 80 parts by weight of ethylenically unsaturated material are combined with 90 to 20 parts by weight of the epoxy resin and, in particular,
Preferably, 40 to 70 parts of ethylenically unsaturated monomers are combined with 60 to 3 parts of epoxy resin.

Although the polymerization reaction is substantially complete after the addition of the reactive materials to the epoxy resin, the reaction period is advantageously extended to that necessary and beyond that necessary to add the polymerizable materials to the epoxy resin in order to to ensure the completion of the reaction.

ABSTRACT
The invention relates in particular to
1 "A process for forming at room temperature a compatible mixture of an epoxy resin with a copolymer of polymerized ethylenically unsaturated materials which, if formed in advance, would be poorly compatible with the epoxy resin, which consists of 9 maintaining the epoxy resin in the liquid phase at an elevated temperature and in the presence of a polymerization catalyst producing free radicals, and adding in small quantities to the epoxy resin thus maintained polymerizable ethylenically unsaturated materials at a rate avoiding a noticeable increase in the concentration of unreacted ethylenically unsaturated material.

20 Embodiments of this method having the following features, taken separately or according to the various possible combinations
at. The ethylenically unsaturated materials consist essentially of monoethylenic monomers selected from vinyl compounds and compounds containing an alpha-beta-ethylenic group;
b. The epoxy resin is a normally liquid polyglycidyl ether;
vs. The epoxy resin is a normally liquid diglycidyl ether of a bisphenol;
d. 10 to 80 parts by weight of ethylenically unsaturated material is combined with 90 to 20 parts by weight of epoxy resin;
e. 40 to 70 parts by weight of the monomers are combined with 60 to 30 parts by weight of epoxy resin;
t. A portion of the ethylenically unsaturated material comprises a functional group reactive with the oxirane group;
g. The vinyl compounds are added to the epoxy resin as a solution in the epoxy resin;
h. Epoxy resin is normally liquid and is maintained at a temperature between 80 and 120 OC.

3o The normally liquid reaction product of paragraph 10.

** ATTENTION ** end of DESC field can contain start of CLMS **.

Claims (1)

** ATTENTION ** start of field CLMS can contain end of DESC **. Preferably, 40 to 70 parts of ethylenically unsaturated monomers are combined with 60 to 3 parts of epoxy resin. Although the polymerization reaction is substantially complete after the addition of the reactive materials to the epoxy resin, the reaction period is advantageously extended to that necessary and beyond that necessary to add the polymerizable materials to the epoxy resin in order to to ensure the completion of the reaction. SUMMARY The invention relates in particular to 1. A process for forming at room temperature a compatible mixture of an epoxy resin with a copolymer of polymerized ethylenically unsaturated materials which, if formed in advance, would be poorly compatible with. epoxy resin, which consists in maintaining the epoxy resin in the liquid phase at an elevated temperature and in the presence of a polymerization catalyst which produces free radicals, and in adding in small quantities to the epoxy resin thus maintained ethylenically non- saturated polymerisables at a rate which avoids a substantial increase in the concentration of unreacted ethylenically unsaturated material. 20 Embodiments of this method having the following features, taken separately or according to the various possible combinations at. The ethylenically unsaturated materials consist essentially of monoethylenic monomers selected from vinyl compounds and compounds containing an alpha-beta-ethylenic group; b. The epoxy resin is a normally liquid polyglycidyl ether; vs. The epoxy resin is a normally liquid diglycidyl ether of a bisphenol; d. 10 to 80 parts by weight of ethylenically unsaturated material is combined with 90 to 20 parts by weight of epoxy resin; e. 40 to 70 parts by weight of the monomers are combined with 60 to 30 parts by weight of epoxy resin; t. A portion of the ethylenically unsaturated material comprises a functional group reactive with the oxirane group; g. The vinyl compounds are added to the epoxy resin as a solution in the epoxy resin; h. Epoxy resin is normally liquid and is maintained at a temperature between 80 and 120 OC. 3o The normally liquid reaction product of paragraph 10.