A low-formaldehyde binder consists essentially of PA0 (A) from 5 to 80% by weight of a water-soluble condensation product of carbonyl number 0-200 which has been prepared by alkaline condensation from 0.1 to 0.4 mole of an aliphatic or cycloaliphatic condensable ketone and 1 mole of formaldehyde, and PA0 (B) from 20 to 95% by weight of 4,5-dihydroxyimidazolidin-2-one and/or an unetherified, partially etherified or completely etherified condensation product thereof with an aliphatic monoaldehyde or dialdehyde.

The present invention relates to low-formaldehyde binders which consist 
essentially of 
(A) from 5 to 80% by weight of a water-soluble condensation product of 
carbonyl number 0-200 which has been prepared by alkaline condensation 
from 0.1 to 0.4 mole of an aliphatic or cycloaliphatic condensable ketone 
and 1 mole of formaldehyde, and 
(B) from 20 to 95% by weight of 4,5-dihydroxyimidazolidin-2-one and/or an 
unetherified, partially etherified or completely etherified condensation 
product thereof with one or more of the aldehydes formaldehyde, glyoxal or 
glutardialdehyde, 
and to the use thereof. 
Ketone-formaldehyde condensation products are known and described for 
example in Houben-Weyl, Methoden der organischen Chemie, volume XIV/2, 
1963, p. 416 ff. Depending on the molar ketone:formaldehyde ratio, the 
products are high molecular weight or high-methylol or cyclic acetals or 
ethers. 
The high-methylol ketone-formaldehyde condensation products can be combined 
with a wide range of compounds, such as amino or phenolic resins, which 
are condensable with formaldehyde. For instance, JP Laid-Open Application 
No. 85/18,551 describes a coating agent which is based on 
ketone-formaldehyde condensation products with methylolated and etherified 
melamine resins and which is cured by acid catalysis. These products have 
in some instances only a low solubility in water, which necessitates the 
use of organic solvents. 
JP Laid-Open Application No. 81/24,474 describes an adhesive which is based 
on an acetone-formaldehyde condensation product incorporating for example 
a urea-formaldehyde condensation product and which is cured under alkaline 
conditions. 
All these products have an undesirably high free formaldehyde content. If 
the coating agents are cured at elevated temperatures, undesirably large 
amounts of the built-in formaldehyde are split off. 
It is an object of the present invention to provide binders which are low 
not only in terms of free formaldehyde but also in terms of thermally 
detachable formaldehyde. In addition, they should be water-soluble and 
storable. 
We have found that this object is achieved with a binder which consists 
essentially of 
(A) from 5 to 80% by weight of a water-soluble condensation product of 
carbonyl number 0-200 which has been prepared by alkaline condensation 
from 0.1 to 0.4 mole of an aliphatic or cycloaliphatic condensable ketone 
and 1 mole of formaldehyde, and 
(B) from 20 to 95% by weight of 4,5-dihydroxyimidazolidin-2-one and/or an 
unetherified, partially etherified or completely etherified condensation 
product thereof with an aliphatic monoaldehyde or dialdehyde. 
Suitable for preparing component (A) are the low members of the homologous 
series of the dialkyl ketones, such as acetone, methyl ethyl ketone, 
diacetone alcohol and cyclohexanone. The use of higher molecular weight 
ketones is limited by the desire for the corresponding condensation 
products to be soluble in water. Particular preference is given to using 
acetone. 
Depending on the number of hydroxymethylatable acidic OH groups available, 
every ketone has a different optimum molar ketone:formaldehyde ratio. 
In the case of acetone, which has the highest possible number of reaction 
OH bonds (6), a molar ketone: form aldehyde ratio from 1:3.75 to 1:7.0, 
preferably from 1:4.0 to 1:6.0, is recommended. For ketones having 5 
reactive CH bonds the following ratios are applicable: from 1.3.0 to 
1:6.0, preferably from 1:3.5 to 1:5.0. If ketone and formaldehyde are used 
in the stated ratios, virtually all the formaldehyde is converted, so that 
the aqueous reaction solution contains less than 1.5% by weight of free 
formaldehyde, even as a rule less than 0.2% by weight. 
The alkaline condensation of the ketone with formaldehyde is preferably 
carried out in aqueous solution, possibly in the presence of alcohols, at 
from 20.degree. to 70.degree. C., preferably at from 30.degree. to 
60.degree. C., lower temperatures being preferred particularly toward the 
end of the reaction, ie. as low free formaldehyde contents. Preferably, 
the condensation is carried out at a pH from 8 to 12, in particular at pH 
10-11.5. 
To maximize the conversion of keto groups on the ketone resin, a high 
conversion being indicated by the low carbonyl number (mg of KOH/g of 
solid as, determined by the Heidbrink method of German Standard 
Specification DIN 53,189) from 0 to 200, preferably from 60 to 180, the 
condensation requires from 5 to 15% by weight of base, preferably from 6 
to 12% by weight thereof, based on condensate. The base is removed in the 
form of insoluble salts thereof. Owing to the large number of insoluble 
salts, the base used in a conventional manner is preferably calcium 
hydroxide, which is separated off in the form of its formates, oxalates, 
phosphates or sulfates. Other suitable bases are for example sodium 
hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and 
barium hydroxide. 
Condensation products (A) are colorless or slightly colored viscous 
substances. The ash content after removal of, for example, calcium formate 
is in general found to be from 0.1 to 0.3% by weight. The solids contents 
of the products can be raised to about 98% by weight. 
The solids content was determined in accordance with modified German 
Standard Specifications DIN 53,216 and DIN 53,189 (see page 6). 
Component (B) serves as a crosslinking agent for the ketone-formaldehyde 
condensation products. Component (B) comprises the cyclic urea 
4,5-dihydroxyimidazolidin-2-one and/or condensation products thereof with 
an aliphatic monoaldehyde or dialdehyde of up to 5 carbon atoms, for 
example formaldehyde, glyoxal or glutardialdehyde, even mixtures thereof 
being possible. For example, 1 mole of 4,5-dihydroxyimidazolidin-2-one may 
be reacted with two moles of formaldehyde to prepare 
1,3-dimethylol-4,5-dihydroxyimidazolidin-2-one which may be condensed with 
from 0.5 to 2 moles of glyoxal. 
The molar urea:aldehyde ratio used ranges in general from 0.1:1 to 10:1, 
preferably from 0.5:1 to 2:1, based on unsubstituted urea. 
It is also possible for alcohols, for example methanol, ethanol, 
n-propanol, n-butanol, methylglycol or mixtures thereof, to be present in 
the condensation reaction, in which case partially or completely 
etherified condensation products are formed. 
Condensation products based on cyclic ureas and glyoxal are described for 
example in U.S. Pat. Nos. 4,285,690 and 4,343,655. 
To prepare the binders according to the invention, from 5 to 80% by weight 
of component (A) are mixed with from 20 to 95% by weight of component (B). 
The preferred mixing ratio is 10-70% by weight of component (A): 30-90% by 
weight of component (B). In general, precondensation of the binder 
according to the invention from (A) and (B) is not necessary. If desired, 
in particular in the event of compatibility problems between the 
components or to effect partial etherification of the crosslinking agent, 
such a precondensation may be carried out at from 40.degree. to 70.degree. 
C. in the presence or absence of from 0.1 to 1.0% by weight of 
p-toluenesulfonic acid. 
The binders are treated with from 0.1 to 5% by weight, preferably from 1 to 
3% by weight, of a thermal curing catalyst and are diluted with water to 
from 10 to 25% by weight strength. 
Suitable catalysts are acids, or latent acids, and metal salts. Preference 
is given to p-toluenesulfonic acid, ammonium, chloride, ammonium 
hydrogenphosphate and the nitrates, chlorides and acetates of magnesium 
and calcium. The binders are cured on the substrates under conventional 
conditions, for example at from 120.degree. to 250.degree. C. in from 1 to 
30 minutes, a higher temperature corresponding to a shorter time and vice 
versa. 
The binders according to the invention are suitable for producing coating 
agents. 
The aqueous resin solutions are suitable in particular as coating, 
impregnating and binding or bonding agents for bonded fiber webs. The 
bonded fiber webs can consist of natural or synthetic organic fibers, for 
example polyamides, polyethylene terephthalate, polypolypropylene, 
cellulose and/or viscose, and also mineral fibers, for example rockwool or 
glass fibers, the fibers being of customary length and thickness. In the 
consolidation of webs the resin solutions produced according to the 
invention are generally used in a concentration from 10 to 25% by weight 
and applied by impregnating the webs by passing the webs for example 
through a bath of the impregnating resin and then squeezing off the 
impregnated web in a conventional manner. The webs can also be sprayed 
with the resin solutions or be treated with foamed resin solutions. The 
impregnated webs, which may have been dried at from 15.degree. to 
25.degree. C., are then conventionally heat-treated to cure the resins. 
The binders according to the invention have a long shelf life even in the 
presence of urea itself in amounts of 10% in aqueous solution with a free 
formaldehyde content from 0.1 to 1.0% by weight. The quantities of 
formaldehyde emitted in the course of curing, as measured by the method 
described in Melliand Textilber. 54 (1973), 415-418, 529-532 and 669-675, 
can be reduced down to values of 0.1%, based on solid resin. 
The webs coated with the binders according to the invention have good 
mechanical properties, such as high breaking strength and high elongation 
and a surprisingly high water resistance, as revealed by the excellent 
values for the boil wash loss in the Table. 
Preparation of Resin Components A 
A/I Acetone-formaldehyde condensation product having a molar 
acetone-formaldehyde ratio of 1:5 
31.75 g of technical grade calcium oxide were added at 40.degree. C. to 
131.25 g of acetone, 848.31 g of formalin (40% by weight strength aqueous 
solution), 961.0 g of water and 131.25 g of butanol and thoroughly stirred 
in. Once a free formaldehyde content of 0.28% by weight had been reached 
the reaction mixture was brought with formic acid to a pH of 6.5, and 
water was distilled off under reduced pressure at a temperature not higher 
than 70.degree. C. The residue was diluted with 817 g of methanol and 
filtered through a suction filter. Methanol was removed under reduced 
pressure at a temperature not above 70.degree. C. and the residue was 
diluted with 130 g of water. 
500 g were obtained of a slightly yellowish product whose solids content as 
measured by German Standard Specification DIN 53,216 (2 g sample kept at 
125.degree. C. for 2 hours) was found to be 70% by weight, the water 
content being 24.8% by weight. The solids content as measured by the 
Heidbrink*) flat weighing bottle method was 74.1% by weight, the ash 
content was 0.11% by weight, the free formaldehyde content was 0.55% by 
weight and the carbonyl number was 105.0 mg of KOH/g of Heidbrink solids. 
A/II Acetone-formaldehyde condensation product having a molar 
acetone:formaldehyde ratio of 1:4: 
33 g of technical grade calcium oxide were added at 40.degree. C. to 132.0 
g of acetone, 1203 g of formalin (40% strength by weight aqueous solution) 
and 180 g of methanol and thoroughly stirred in. Once a free formaldehyde 
content of 0.9% by weight had been reached the reaction mixture was 
acidified with formic acid to pH 6.5 and 
FNT (*)as defined in German Standard Specification DIN 53,189, 0.2 g sample of 
70% strength by weight aqueous solution, the test bottle being dried over 
P.sub.2 O.sub.5 at room temperature in a water pump vacuum for 2 hours 
with and without substance) worked up in the same way as product A/I using 
1400 g of methanol. The yield was 612.0 g. 
The solids content of the slightly colored product was 80.0% by weight, the 
Heidbrink*) solids content was 93.5% by weight, the ash content was 0.45% 
by weight, the free formaldehyde content was 0.85% by weight and the 
carbonyl number was 184 mg of KOH/g of Heidbrink*) solids. 
FNT (*)as defined in German Standard Specification DIN 53,189, 0.2 g sample of 
70% strength by weight aqueous solution, the test bottle being dried over 
P.sub.2 O.sub.5 at room temperature in a water pump vacuum for 2 hours 
with and without substance)

EXAMPLE 1 
A needled polyester spunbonded web of about 190 g/m.sup.2 was impregnated 
with a 12% strength by weight aqueous binder liquor, and the excess binder 
liquor was squeezed off. The squeeze pressure was adjusted in such a way 
that after the web had been dried at 170.degree. C. the binder content was 
about 20% by weight, based on the weight of fiber. The impregnated and 
dried web had a weight of about 230 g/m.sup.2. 
The binder liquor comprised 
50 g (as solid) of a resin as per method A/I 
50 g (as solid) of 1,3-dimethylol-4,5-dihydroxyimidazolidin-2-one 
1 g of ammonium chloride 
The breaking strength and washoff losses of the webs are summarized in the 
Table. 
EXAMPLE 2 
Using the method of Example 1 a needled polyester spunbonded web was 
impregnated with a 12% strength by weight binder liquor comprising 
50 g (as solid) of a resin as per method A/I 
50 g (as solid) of 1,3-dimethylol-4,5-dihydroxyimidazolidin-2-one 
3 g (as solid) of ammonium chloride and dried. 
EXAMPLE 3 
The method of Examples 1 and 2 was followed to impregnate with an 
approximately 12% strength by weight binder liquor comprising 
60 g (as solid) of a resin as per method A/I 
40 g (as solid) of 1,3-dimethylol-4,5-dihydroxyimidazolidin-2-one 
1 g (as solid) of ammonium chloride. 
EXAMPLE 4 
The method of Examples 1 and 2 was followed to impregnate with an 
approximately 12% strength by weight binder liquor comprising 
60 g (as solid) of a resin as per method A/I 
40 g (as solid) of 1,3-dimethylol-4,5-dihydroxyimidazolidin-2-one 
3 g (as solid) of ammonium chloride. 
TABLE 
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Breaking 
strength Elonga- Washoff 
[N/5 cm of tion loss 
width] [%] [%] 
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Web of Example 1 
637 62 0.8 
Web of Example 2 
644 60 1.3 
Web of Example 3 
641 62 0.9 
Web of Example 4 
624 61 1.3 
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