Resin composition

A resin composition useful as a binder is provided comprising a mixture of a formaldehyde-based resin with a resin substitute comprising the reaction product of an amine derivative chosen from melamine, glycolurile or their mixtures with 1 to 2 moles of a C.sub.1 to C.sub.8 dialkoxyethanal, the reaction product is mixed, preferably reacted, with a polyol.

BACKGROUND OF THE INVENTION 
A low formaldehyde alternative to phenolic, melamine, and urea resins, 
which are based on formaldehyde, has been desired because of regulatory 
and health concerns regarding formaldehyde. Due to the high performance, 
strength and rigidity of these thermosetting formaldehyde-based resins in 
industrial applications, replacement products maintaining suitable 
performance have been difficult to find. This invention discloses a resin 
substitute which can be used to substitute for a portion of the 
phenol-formaldehyde, urea-formaldehyde, resorcinol-formaldehyde and 
melamine-formaldehyde resins in many applications, but contains no phenol 
or formaldehyde and provides the additional benefit of scavenging free 
formaldehyde from the resin composition mixture. These are thermosetting, 
film-forming resin compositions which offer tensile strength, rigidity and 
water-resistance comparable to the phenol-formaldehyde, 
melamine-formaldehyde and urea-formaldehyde resins now in use. 
French Patent Application number 94-10186 filed Aug. 22, 1994 by Societe 
Francaise Hoechst discloses a novel aminoplast resin comprising the 
reaction product of an amine derivative such as melamine, glycolurile or 
their mixtures with an aldehyde of the formula R--CHO in which R 
represents a dialkoxy methyl group, 1,3-dioxolan-2-yl possibly substituted 
up to 4 and/or 5 times by one or more alkyl groups (preferably up to 
C.sub.4 alkyl), or a 1,3-dioxan-2-yl group possibly substituted up to 4, 5 
and/or 6 times by one or more alkyl groups (preferably up to C.sub.4 
alkyl); in mixtures possibly with glyoxal. However, these aminoplast 
resins do not self-condense satisfactorily, forming films which are weak, 
brittle and water-sensitive. Attempts to hydrolyze the acetal groups of 
these resins in order to increase their reactivity resulted in degradation 
of the melamine ring. 
Thus it is an object of this invention to improve the aminoplast resins as 
disclosed by French Patent Application No. 94-10186 to provide a resin 
which can be used as a substitute for a portion of a formaldehyde-based 
resin providing a low formaldehyde alternative, which upon crosslinking 
provides films which are strong, hard, tough and water resistant. It is a 
further object of this invention to provide a resin substitute composition 
which not only reduces formaldehyde emissions by replacing a portion of 
the formaldehyde based resin, but also scavenges formaldehyde while 
maintaining physical properties. Applications for such improved resins 
include uses as binders for non-woven substrates such as glass, polyester 
and nylon fibers used in building materials, air filters or scrub pads, as 
well as for cellulose substrates such as automotive filters. 
SUMMARY OF THE INVENTION 
Briefly, the subject invention provides a resin composition comprising a 
mixture of a formaldehyde-based resin with a resin substitute comprising 
the reaction product of 1 to 2 moles of a C.sub.1 to C.sub.8 
dialkoxyethanal with an amine derivative chosen from the group consisting 
of melamine, glycolurile or their mixtures, the reaction product is then 
mixed with a polyol having 2 or more hydroxyl groups. Optionally the amine 
derivative and dialkoxyethanal are also reacted with a dialdehyde, 
preferably glyoxal. In a preferred embodiment the polyol is reacted with 
the reaction product.

DETAILED DESCRIPTION 
The resin composition comprises a mixture of a formaldehyde-based resin 
with a resin substitute. The resin substitute comprises a reaction product 
mixed with a polyol. The formaldehyde-based resin, includes but is not 
limited to phenolic resins, melamine resins, resorcinol resins and urea 
resins. The resin substitute reaction product is the addition product of 
an amine derivative with dialkoxyethanal. The amine derivative is either 
melamine, glycolurile or a mixture thereof, with melamine preferred 
because the products provide stronger and tougher films. 
The C.sub.1 -C.sub.8 dialkoxyethanal is reacted with the amine derivative 
generally at a molar ratio of about 1 to 2 equivalents of dialkoxyethanal 
to melamine and about 1 to 2 equivalents for glycolurile, preferably about 
1.5 to 1.75 equivalents of dialkoxyethanal to the amine derivative. In 
addition a dialdehyde, preferably glyoxal, can also be inchdeal in the 
reaction product in order to provide branching points in the molecular 
structure, and to promote a higher molecular weight. The dialdehyde is 
added generally at a level of 0.05 to 1.5 preferably 0.5 to 1, molar 
equivalents of aldehyde to the amine derivative. 
The C.sub.1 to C.sub.8 dialkoxyethanal generally has the following formula: 
##STR1## 
wherein R.sub.1 and R.sub.2 are C.sub.1 -C.sub.8 alkyl or R.sub.1 and 
R.sub.2 are joined to form a cyclic dioxolano or a dioxano substituent. 
The C.sub.1 to C.sub.8 dialkoxyethanol can also be described as a glyoxal 
monaceacetal which the acetal is comprised of linear substituents or is a 
cyclic aceml. Preferably R.sub.1 and R.sub.2 are a C.sub.1 -C.sub.4 alkyl 
group, preferably the same group and preferably a methyl group, i.e. 
dimethoxyethanal (DME), as this is the most economical derivative which is 
commercially available, manufactured by Societe Francaise Hoechst and sold 
under the trademark Highlink DM.TM.. 
A particular stoichiometry of diaibxyethanal and the amine derivative, in 
particular dimethoxyethanal (DME) and melamine forms a resin substitute 
that enhances the performance of a formaldehyde-based resin such as 
phenolic resin, and reduces the formaldehyde emissions significantly more 
than expected by merely removing some of the phenolic resin. A melamine 
resin containing up to about 2 moles, preferably about 1.5 to 1.75 moles, 
of DME per mole of melamine forms a stable solution when prepared with 
polyols. A DME-melamine resin of this stoichiometry without the polyols is 
not stable. However, this DME-deficient resin does not have the tensile 
strength of a more fully substituted resin, i.e. a resin containing 2.75 
to 3.0 equivalents of DME per mole of melamine plus polyol. It would be 
expected that such a DME-deficient resin would be an inferior candidate 
for a phenolic replacement or extender because it forms weak, water 
sensitive and brittle films. It was unexpectedly found that this DME 
deficient resin caused improved performance when mixed with a 
formaldehyde-based resin, such as phenolic resin. It also caused an 
unexpected increased reduction in formaldehyde emissions measured at 
elevated temperatures, when compared to more fully substituted DME 
melamine resins used at a comparable level. 
It is theorized, but this invention is not limited thereto, that the 
polyols react with the DME substituted melamine resin through either the 
hydroxyl group or a methoxy group and improve the stability and solubility 
of the DME deficient resin. This affords a stable solution of a melamine 
species having an average of at least one free NH.sub.2 group. A mixture 
of species is present in solution having either 1 or 2 free NH.sub.2 
groups, with only a minor insignificant amount of trisubstituted material. 
These free NH.sub.2 groups react readily with the methylol groups of the 
phenolic resin and also with the free formaldehyde present. This 
cross-links the phenolic resin and scavenges the formaldehyde. The 
scavenged formaldehyde remains substantially bound even at temperatures up 
to 200.degree. C. 
In addition to the reaction product a polyol having 2 or more hydroxyl 
groups is mixed in to form the resin substitute. Suitable polyols include 
dialkylene glycol, polyalkylene glycol, glycerin, alkoxylated glycerin, 
polyvinyl alcohol, dextrose (and dextrose oligomers and derivatives such 
as corn syrup), starch, starch derivatives, polyglycidol or 
polysaccharrides (and derivatives). Preferred polyols are dipropylene 
glycol, triethoxylated glycerin, polyvinyl alcohol and mixtures thereof. 
The polyol is added at a level of at least 0.05 molar equivalents of 
polyol to the reaction product, preferably at least 0.1 molar equivalents. 
Generally the resin substitute comprises an amount of about 1% to 99%, 
with 15-50% preferred of polyol by weight (dry basis) of the resin 
composition. Through the addition of a polyol to the DME-deficient 
reaction product a stable resin substitute is provided which is capped and 
is inhibited from disproportionating to soluble, trisubstituted melamine 
derivatives and insoluble monosubstituted melamine derivatives. 
In a preferred embodiment in the resin substitute the polyol is reacted 
with the reaction product. The resultant resin composition containing the 
resin substitute has been shown to have significantly improved properties, 
namely improvement in stability, ambient tensile and hot wet tensile for a 
textile product using the resin composition as a binder where the polyol 
is reacted with the reaction product verses being mixed with the reaction 
product. Generally the polyol is reacted with the reaction product under 
the following conditions: 75.degree. to 110.degree. C., or at reflux; at a 
pH of 4-7, preferably 5.5 to 6.5; and for a time period of 0.5 to 5 hours, 
preferably 2-3 hours. 
Generally, the resin composition comprises from 20 to 99%, preferably 50 to 
85% (by dry weight) of the formaldehyde-based resin and 80 to 1%, 
preferably 50 to 15% (by dry weight) of the resin substitute (e.g. 
DME/melamine/polyol). With the use of the resin substitute as a partial 
replacement for the formaldehyde based resin increased dry and hot wet 
tensile strength and reduced free formaldehyde levels were observed. 
The addition of an acid catalyst to the resin composition is also 
desirable. Suitable catalysts are sulfuric acid, hydrochloric acid, 
phosphoric acid, p-toluene sulfonic acid, methane sulfonic acid, aluminum 
salts such as aluminum hydroxychloride and aluminum chloride, magnesium 
chloride, zirconium sulfate and zinc chloride and the like. These 
catalysts facilitate the reaction(s) which effects the crosslinking and 
scavenging. The acid catalyst is generally added in an amount of 0.1% to 
15% preferably, 1% to 10% based on the weight (dry basis) of the reaction 
product. 
This resin composition is useful as a binder for cellulosic automotive oil 
filters, or for fiberglass in such uses as fiberglass, textiles or 
insulation. The resin composition can be added to a hydroxyl containing 
polymer (e.g. polyvinyl alcohol wherein the resin composition is used to 
crosslink the polymer. The performance of the formaldehyde-based resin 
binder can be maintained, while formaldehyde emissions are greatly 
reduced. 
EXAMPLE 1 
Resin substitute formulations were prepared having DME/melamine molar 
ratios of 1.0:1.0, 1.25:1.0, 1.5:1.0, and 1.75:1.0 with proportionately 
increased amounts of polyols present. These formulations are shown in 
Table 1. Reactants were loaded, pH adjusted to around 6.0, then heated to 
reflux for 2 hours. 
The melamine in samples A and B did not fully dissolve and remained as a 
precipitant. Samples C and D were clear amber solutions in which the 
melamine totally dissolved and did not precipitate upon cooling. Samples C 
and D were stable and preferred for use, thus establishing a lower 
preferred limit for the composition of between 1.25 and 1.5 moles of DME 
per mole of melamine for a stable product. 
TABLE 1 
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A B C D 
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DME/melamine molar ratio 
1:1 1.25:1 1.5:1 
1.75:1 
DME, 60% 175 220 260 303 
Melamine 126 126 126 126 
dipropylene glycol 
30 37 43 50 
glycerin triethoxylate 
20 25 30 35 
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EXAMPLE 2 
Alternatively, a resin substitute may be prepared by a 2-stage process. To 
a 1 liter flask fitted with a condenser, stirrer and thermocouple 
temperature controller was added 303.3 grams of 60% dimethoxyethanal (1.75 
moles) and 126 grams of melamine (1.0 mole). The pH was 5.9. This was 
heated to reflux (103.degree. C.) for 1 hour. While still at this 
temperature, 50 grams of glycerin triethoxylate (0.2 moles) and 35 grams 
of dipropylene glycol (0.26 moles) were added. Reflux was continued for 1 
hour. The reaction was diluted with 140 grams of water and allowed to 
cool. This afforded a resin similar in performance to sample D above. 
EXAMPLE 3 
Resin substitutes may also be prepared by reacting the DME and melamine at 
pH 9.0-9.5 at 60.degree. C. for 2 hours, then adding the polyols, 
adjusting the pH to 6.0-6.5 and refluxing for 2 hours. Results are 
comparable. 
EXAMPLE 4 
Using either of the procedures in Examples 1-3 above, a Lewis acid catalyst 
may be added with the polyols to facilitate transetherification between 
the polyol hydroxyls and the DME acetat methyl ethers. Results are 
similar, but viscosity is 200-500 cps higher. Suitable catalysts are 
magnesium chloride, aluminum chloride, zinc chloride and the like. 
EXAMPLE 5 
A comparative resin was prepared by charging to a 1 liter flask 477 grams 
of 60% DME (2.75 moles) and 126 grams (1.0 mole) of melamine. The pH of 
the slurry was 5.8. This was heated to reflux for 1 hour. At this time, 
106.2 grams of glycerin triethoxylate (0.47 mole) 70.8 grams dipropylene 
glycol (0.52 mole) and 7.5 grams of a 32% solution of magnesium chloride 
were added and refluxed 2 more hours. The reaction was then cooled to 
afford a dark amber solution. 
EXAMPLE 6 
The resin substitute of Example 1 and the comparative resin of Example 5 
were used at a level of 25% (by dry weight) to extend an aqueous phenolic 
resin (molar ratio of 3 formaldehydes per phenol) used commercially for 
automotive oil filter media. This aqueous phenolic resin had a pH of 8.8, 
solids of 50.1%, and a free formaldehyde content of 4.4% as measured by a 
cold sulfite method. A vacuum oven with a series of impingers was used to 
capture formaldehyde emissions at elevated temperatures. The 0.1 gram 
sample of either the pure phenolic resin or an extended phenolic resin was 
placed into the oven after the oven was equilibrated at the desired 
temperature. Air was drawn through the oven for 20 minutes and captured in 
a buffered solution of 0.2% hydrazine sulfate. The impinger solutions were 
combined, diluted to volume and analyzed by polarography. The formaldehyde 
detected was reported as "%" or "ppm" as appropriate. Samples were tested 
at 95.degree. C. and 200.degree. C. Air blanks were drawn between samples. 
By substituting 25% of the phenolic resin, it would be expected to reduce 
evolved formaldehyde by around 25%. The comparative resin of Example 5 did 
slightly better than this. It is believed to be a mixture of mostly 
trisubstituted melamine products, but also a minor amount of less 
substituted melamine products which could also scavenge free formaldehyde. 
The resin substitute of Example 1 did significantly better than this. It 
is believed to be mostly mono- and di-substituted melamine products having 
free NH.sub.2 groups to react with formaldehyde, with very little 
trisubstituted product. Results are shown in Table 2. 
TABLE 2 
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RESIN Temp, 
A B C D .degree.C. 
______________________________________ 
phenolic 100 75 75 99 
Ex 1 24 
Ex 5 24 
MgCl.sub.2 1 1 1 
Calculated % CH.sub.2 O 
0.38 0.28 0.28 0.38 95.degree. C. 
Measured % CH.sub.2 O 
0.38 0.12 0.22 0.38 
Calculated % CH.sub.2 O 
2.9 2.2 2.2 2.9 200.degree. C. 
Measured % CH.sub.2 O 
2.9 1.6 2.0 2.9 
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EXAMPLE 7 
While the dry and hot wet tensile strength of a DME-deficient resin 
substitute is significantly less than that of a phenolic resin, the 
mixture of this resin substitute and a phenolic resin is observed to be 
equal to or better than either component. Formulations shown in Table 3 
were padded onto Whatman paper, then dried and cured at 325.degree. F. for 
5 minutes. Samples were tested for ambient tensile and hot wet tensile 
strength. 
TABLE 3 
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RESIN 
A B C 
______________________________________ 
phenolic 100 74 -- 
EX 1 -- 24 97 
MgCl.sub.2 2 3 
% add-on 20.3 20.7 23.0 
Dry tensile, Kg 
7.7 8.2 4.7 
Hot wet tensile, Kg 
5.83 5.82 3.36 
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The resin substitute exhibits a unique ability to scavenge formaldehyde and 
maintain or improve the physical properties of the phenolic resin. This 
would allow lasers of phenolic resins to blend these products with their 
resin and lower formaldehyde emissions to improve air quality without 
sacrificing performance. The synergy that exists between these 
DME/melamine resins which perform poorly by themselves, yet enhance the 
performance of the phenolic resins is quite unexpected. The blend of the 
phenolic resin and these DME-deficient resins performs better than either 
product alone. This synergy is not observed between phenolic resins and 
fully substituted DME/melamine resins. The resin substitute is also 
suitable for extending melamine-formaldehyde or urea formaldehyde resins 
to improve performance and scavenge formaldehyde.