NO771970L - AMIN RESIN PRODUCT AND PRODUCTS FOR PRODUCING THEREOF - Google Patents

Description

The invention relates to amino resin products containing urea/formaldehyde, melamine/formaldehyde, phenol/formaldehyde and/or mixtures thereof. The products have characteristic features which make them advantageous for use for a number of purposes.

In accordance with the invention, an amino resin product is provided which comprises an unreacted or partially reacted mixture of at least one amino resin and formose. An unreacted mixture is simply a mixture of the amino resin(s) and formose, while a partially reacted mixture additionally contains some additional amino resin formed as a result of reaction between the amino resin(s) and formose during the preparation of the mixture.

The amino resin products according to the invention preferably comprise:

5-50% (by weight of total solids) of formose solids

50-95. % (by weight of total solids) of amino resin solids.

The products will normally be in the form of aqueous solutions with a solids content of 40-80% by weight.

More preferably, the products comprise:

10-30% formose solids by weight of the total solids. 70-90% of amino resin solids by weight of the total solids.

The molar ratio between formaldehyde and amino groups in the amino resin components is preferably in the range 0.6:1 to 1.5:1, more preferably between 0.7:1 and 1:1.

(For example is for a urea/formaldehyde condensate

the molar ratios between formaldehyde and urea from 1.2:1 to 3:1, preferably 1.4:1 to 2:1). The formaldehyde in

the amino resin component naturally does not include that which has already been converted to formose.

The amino resin products according to the invention can be produced by reacting or mixing an amino resin with

a solution of formose.. The formose solution can e.g. is prepared by heating formalin with a base, especially CatOH^; this reaction is self-catalytic and can be accelerated in the initial stages by the addition of a small amount of preformed formose or a saccharide, e.g. sucrose, glucose or dextrose. It can also be produced by treating paraformaldehyde with dilute alkali.

Formose is a complex mixture of hexoses, pentoses and other carbohydrates. It is racemic and not easily fermentable with yeast. It is normally obtained in aqueous solution and can be concentrated into a syrup.

The amino resin component can e.g. produced by aqueous condensation of formaldehyde with urea and/or melamine. Preparation of an amino resin usually comprises the steps: (a) Mixing urea and/or melamine and formalin, and reacting (usually with heating) at a pH value of about 7.0. (b) Condensation of the mixture by heating at a pH value of approx. 4-6 during or after which further additions of urea and/or melamine can be made.

Formosa solution or syrup can be added at any stage. However, it is practical to add it at the beginning, before step (a), so that reaction can occur between formose and the other components, and so that the build-up of the characteristics of the amino resin product can be monitored as the reaction progresses.

A variety of amino resin products with varying properties can be produced. More particularly, amino resin products with either high water solubility or low water solubility can be prepared.

Highly soluble amino resin products are prepared with relatively high formose contents (e.g., 15% by weight or more) and/or with higher formaldehyde:amino group ratios (e.g., above about 0.75:1). Limiting the degree of condensation of the amino resin favors

also the solubility in water.

Amino resin products with low solubility are favored by lower formose content, lower formaldehyde:urea ratios and higher condensation rates.

Water-miscible amino resin products show a lack of syneresis during gelation and curing and are particularly resistant to cracking when cured and dried as castings or coatings. They are useful in the production of foam, e.g. for insulation of cavities in walls, as a surface coating, especially when used together with such fillers as sand, plaster or clay, and as modifiers and coatings for plaster products.

due to their water-miscibility, they are also useful as paper, board and textile additives, e.g. for achieving improved wet strength in paper and cardboard products.

A feature of these amino resin products is that if a fire occurs, the cured amino resin product undergoes swelling, i.e. the formation of an expanded, charred mass which can isolate other material from the effects of the fire. Use in swelling coatings is therefore suggested.

The less soluble amino resin products do not show syneresis during gelation and curing and are less resistant to cracking during curing. However, they can be modified so that these are prevented, e.g. by adding latex and/or sodium silicate, or they can be used as adhesives for wood products, e.g. chipboards. In any case, the useful property with regard to swelling is maintained when exposed to burning.

The amino resin products can be hardened by adding an acid and/or by heating (preferably below 100°C) if necessary. The amino resin products tend to harden more slowly than conventional resins, and therefore the use of strong acids is recommended.

EXAMPLES

1. Preparation of fprmose solution

1440 mL formalin (36% HCHO, 5.6% methanol), 456 mL

water, 82 g Ca (OH)^°94 g dextrose were gently heated in a flask fitted with a reflux condenser. At a temperature of 55°C the heating was stopped and an exotherm occurred causing the mixture to rise rapidly to 94°C. The formose solution thus obtained was cooled, neutralized with 340 ml

of 25% w/v Na 2 SO 3 solution and filtered. The filtrate was concentrated by evaporation under vacuum at 37-40°C so that a formose solution of approximately 37% concentration was obtained. Analy-

se showed a Ca content of 1250 ppm and a free formaldehyde content of 0.735 wt/vol%. 2. One premix of urea and formalin, with a formaldehyde:urea ratio of 2:1, was prepared from 432 ml of formalin (36.4%) and 171.5 g of urea. 250 ml formose solution from example 1 was added, and the pH value was adjusted to 7.0 by adding NaOH solution. The mixture was refluxed for 30 minutes, and then the pH value was reduced to 5.0 by the addition of formic acid solution. The mixture was refluxed for 145 minutes. The pH was then raised to 5.8. (NaOH solution was used), cooled, and further NaOH solution was added, so that the pH value was brought to 7.8. The mixture was concentrated by vacuum evaporation at 40°C, so that a resin product with the following characteristics was obtained:

Solids content 68%

Specific gravity 1.255

Water tolerance (at 25°C) 3000%

Formose content 22% based on solids

Viscosity 1.8 poise.

A portion of the resin product was gelled by adding 10% of a 30% phosphoric acid solution. It gelled within 45 minutes without syneresis, and long-term drying and curing gave a hard material without cracking. When burned, the material showed swelling.

3. As in example 2 with the exception that 423 ml of formalin was used

193 g of urea

in the molar ratio of 1.75:1. The acid condensation step was carried out at pH 5.0 for 66 1/2 minutes. The properties of the resin product were-.

Solids content 72%

Specific gravity 1.281

Viscosity 5.3 poise

Water tolerance 500%

Formosa content 22%

. A sample was gelled as indicated in Example 2 and gave gelation within 40 minutes without syneresis and without cracking after a long time.

4. As in example 2, with the exception that 423 ml of formalin was used

220.5 g of urea

in the molar ratio 1.55:1. The acid condensation was carried out at pH 5.0

for 46 minutes. The properties of the resin product were:

Solids content 70%

Specific gravity 1.281

Viscosity 3.6 poise

Water tolerance 180%

Formosa content 22%

Samples, gelled which previously showed syneresis and a tendency to crack when aging at 50°C. The material showed distinct swelling when fired.

5. A formose solution was prepared as described in example 1, and this was concentrated to 40% formose. 250

parts of this solution were added to a mixture of 460 parts formalin (36.5% formaldehyde, 6.5% methanol) and 193 parts urea (mbl ratio formaldehyde:urea 1.75:1, formose content 20%). The mixture was refluxed for 15 minutes, adjusted to pH 4.85 (by addition of formic acid solution) and further refluxed for 68 minutes. The solution was adjusted to pH 5.5 (by addition of NaOH solution), cooled to 40°C and further adjusted to pH 7.5. The resin was concentrated by vacuum evaporation at 42-48°C so that a resin with a viscosity of 11 poise was obtained.

6. A portion of the resin prepared in Example 5 was concentrated by further vacuum evaporation to a viscosity of 35 poise, and it was mixed with equal parts of a conventional UF resin of the same viscosity to obtain a resin as in -held 10% formose. The resin used for mixing,. was prepared by a conventional process (namely by neutral reaction followed by acid condensation and then evaporation) and had a formaldehyde:urea ratio of 1.95:1. 7. A formose solution was prepared as described in example 1, and this was concentrated to 50% formose. 300 parts of this solution was added to a mixture of 220.5 parts urea and 460 parts formalin (as used in Example 5). The mixture was adjusted to pH 7, refluxed for 15 minutes and then acidified to pH 4.85 ( by adding formic acid solution) and boiled under reflux for a further 55 minutes. The mixture was then partially neutralized, cooled and brought to pH 7.5. It was then vacuum evaporated at 48 to 50°C to give a resin with a viscosity of 100 poise. The formose content of the resin was 30%, based on the total solids.

Claims (13)

1. Amino resin product, characterized in that it comprises an unreacted or partially reacted mixture of at least one amino resin and formose. 2. Amino resin product as stated in claim 1, characterized in that it contains 5-50% formose solids and 50-95% amino resins, by weight of the total solids. 3. Resin product as stated in claim 2, characterized in that it contains 10-30% formose solids and 70-90% amino resins, by weight of the total solids. 4. product as stated in any of claims 1 to 3, characterized in that the molar ratio between formaldehyde and amino groups in the amino resin component(s) is in the range 0.6:1 to 1.5:1. 5. product as stated in claim 4, characterized in that the molar ratio between formaldehyde and amino groups in the amino resin component (e) is in the range 0.7:1 to 1:1. 6. Product as stated in any of the preceding claims, characterized in that it is in the form of an aqueous solution with a solids content of 40-80% by weight. 7. Amino resin product, substantially as herein described. 8. Process for the production of an amino resin product, characterized by the steps comprising reacting an aqueous solution of formaldehyde or paraformaldehyde under alkaline conditions to produce a formose solution, and the step comprising mixing or partially reacting the formose solution (a) with further aqueous solution of formaldehyde or paraformaldehyde and at least one compound capable of forming an amino resin with formaldehyde, and/or (b) with such an amino resin, to form a product containing formose and an amino resin. 9. Method as stated in claim 8, characterized in that the formose solution is neutralized before the mixture or the step comprising partial reaction. 10. Method as stated in claim 8 or 9, characterized in that the formose solution is mixed or partially reacted with the further aqueous solution of formaldehyde or paraformaldehyde and the compound which is capable of forming an amino resin with formaldehyde, and/or with such an amino resin, under acidic conditions. 11. Method as stated in claim 10, characterized in that the mixture or the partial reaction is carried out in the presence of formic acid. 12. Method as stated in claim 10 or 11, characterized in that the resulting product containing formose and an amino resin essentially neutralizes res by the addition of eh alkaline substance. 13. Method as set forth in any one of claims 8 to 12, characterized in that the resulting product containing formose and an amino resin is concentrated by evaporation.