NO128615B - - Google Patents

Description

Process for the production of phenolic resin foam.

The present invention relates to a method for the production of foamed phenolic resins, which method exhibits great advantages over the known methods and enables the production of products with better properties than the known foamed phenolic resins.

The invention relates to a method for the production of phenolic resin foam, starting from a phenolic resin which is formed by condensation of phenol and formaldehyde in an alkaline medium, possibly in the presence of a copolymerizable substance, for example carbamide or mélamiri, and mixing in the phenolic resin a surface-active substance and a propellant, after which the mixture is foamed by activating the drive Kfr. at 39b<5->37/20 the agent, the method being characterized in that the phenolic resin is in the form of a water solution, that the surfactant is a silicone oil of the silicone glycol copolymer type which is soluble in water and stable in solution, and that the propellant is selected from among the aliphatic hydrocarbons or their halogen derivatives individually or in mixture which are insoluble in water and which are liquid at normal temperature.

The silicone oils used can be copolymeric silicone glycols, which are water-soluble and stable in solution.

It has been found that the use of these silicone oils makes it possible to obtain uniform foaming and consequently foam products with practically uniform-sized cavities, and with uniform distribution in the foam mass.

According to another feature of the invention, a propellant is used which is not soluble in water and which is liquid sweat at ordinary temperature, but which has a low boiling point, producing an evaporation in the mixture by raising the temperature of the mixture, which causes the resin to harden .

The propellant is preferably chosen from among aliphatic hydrocarbons or their halogen derivatives, especially "Freon 11" or CCl^F, "Freon 113" or CC^F-CCIF^, petroleum ether, pentane, these propellants being used alone or in a mixture.

According to another feature of the invention, curing of the resin and evaporation of the propellant is achieved by means of a curing agent consisting of a mineral acid or an organic acid, especially HC1, H^PO^, H^SOjj, toluenesulfonic acid, methanenitrobenzenesulfonic acid. This hardener must produce an exothermic polymerization in the resin, the heat given off being sufficient to evaporate the propellant.

A polymerization catalyst and a mineral additive can also be used.

The polymerization catalyst can have amino groups, and be of the type urea, ammonium chloride, triethylenediamine.

The mineral additive in powder form can be chosen from the substances silicon dioxide, talc, mica, kieselguhr, asbestos, sawdust, glass microspheres, crushed glass fibres, carbon black, etc.

One can e.g. use the resins below for the production of foams according to the invention.

These resins are produced by condensing the phenol under basic catalysis with the formaldehyde in aqueous solution or in trimer form, possibly copolymerized with urea, melamine or other copolymerisable substances.

The neutralized aqueous resins are concentrated to 75% » if they do not already have this concentration.

Resins produced by condensation with an acid catalyst between phenol and formaldehyde have very low curing rates, which is not suitable for the method.

The foaming of the resins can be carried out in the presence of the above-mentioned components in the following proportions: Water-soluble silicone oils 0.5 - 5%, preferably 2%. Catalyst: varying, preferably approx. 0.5 Mineral filler: 5-30%, preferably 10-20%. Propellant: depending on the desired specific weight for pro duct, usually between 5 and 40 Hardener: Usually between 5 and 25%.

Hydrochloric acid is used pure, i.e. in a 35% solution with a specific gravity of 1.19. The sulfuric acid is preferably present in an aqueous solution of 50% strength. The organic acids are dissolved in water until saturation of the solution.

Listed below are examples of implementation of the method of the invention. The recipe is based on 100 kg of resin.

Example 1

Example 2 Example 3 Example 4 Example 5

Example 6

Example 6 (continued) Example 7

The individual components in the above compositions are mixed in the order listed. The acid is added separately or together with the additive.

The method according to the invention can be carried out continuously or discontinuously.

If the procedure is carried out discontinuously, one can proceed

as follows:

A fast mixer with a motor of approx. 10 horsepower and with a stirrer of approx. 135 mm diameter is very suitable. The phenolic resin is introduced into a plastic container. Silicone oil, additive, catalyst and <H>Freon" are added. An excess of the latter is necessary to compensate very carefully for the evaporation loss during stirring.

The acid is then added to the mixture. The mixture of the emulsion falls rather strongly, which facilitates the homogenization. The dispersion of the acid must be very even to avoid a heterogeneous composition.

You get a whitish slightly frothy cream-like mixture. At the end of the stirring, the liquid is quickly poured into a pre-prepared mould. The liquid fills the bottom of the mold where it immediately begins to expand. The expansion lasts for one or two minutes. The foam eventually fills the open mold space and takes on a curved surface due to the central pressure in the foam, which is greater in relation to the braking effect along the walls of the mold. A fine surface skin forms after complete expansion during initial hardening. After 10 to 15 minutes, the foam is sufficiently stiff to be removed from the mold and cut mechanically.

The walls of the mold are made non-stick by applying a coating of wax, varnish or polyethylene foil, and are again ready for filling.

In the manner described above. you get blocks of 100 liter foam volume.

In the case of a continuous process, one can proceed as described below: Two containers, one of which contains the resin mixture, the silicone oil and the propellant, and the other contains the acid, are connected by a mixing chamber. An air turbine-driven stirrer ensures stirring of the components in the chamber.

The introduction of specific quantities of the components is provided by dosing pumps. After mixing, the produced viscous liquid is poured into a mold for the production of blocks, or on a moving web to produce a continuous foam web in this way.

The method according to the invention makes it possible, with the resins whose composition is mentioned above, to arrive at cell-shaped rigid materials with a finished specific weight of approx. 25 kg/m "5.

In the above examples, it is possible to vary the specific gravity of the product by adding more or less "Freon'1 for example:

The foamed polymer does not acquire its final properties until after drying or maturing for 24 hours at 100°C. The dried foam mass exhibits a fine cell structure that is completely uniform throughout the foam mass. The content of closed cells is greater than in normal foam types, as it is at least 75%•

Listed below are particularly valuable properties for products manufactured in accordance with the invention.

Durability when temperature increases.

The resistance to elevated temperature is greater than for all other known cellular plastic materials. This property is further improved if the resin is modified by adding urea or melamine.

With a phenol formaldehyde foam, you get a temperature resistance of up to 150°C, which is characterized by the fact that there are no changes in colour, dimension or significant weight loss. With a foam resin of phenol formaldehyde urea, the product is temperature resistant up to 200°C.

Refractoriness

The product produced according to the invention is highly flammable. Refractoriness is further increased by adding flame retardants such as e.g. antimony oxide in the presence of a chlorinated compound, or chlorinated paraffins.

Corrosion resistance

The content of free acid after drying or heat treatment is very small (70 mg HCl/dm^ foam). This means that the foam mass does not attack the materials it is attached to or brought into contact with.

Coating ability

The products stick to paper, coated kraft paper, wooden materials, plaster, laminated polyester.

You can coat plastic materials, e.g. (when gluing) to improve properties such as waterproofing or stiffness.

Mechanical properties

The mechanical strength of the rigid material is quite significant even with a low specific weight. The values below apply to phenol-formaldehyde resin produced as in the first example. a) Compression resistance (measured at 10% compression in the test apparatus):

1.3 kg/cm 2 for a specific weight of 30 kg/irr^

1.6 kg/cm 2 for a specific weight of 41 kg/no<3>

2.5 kg/cm 2 for a specific weight of 68 kg/m<3>

b) Bending resistance:

A load of 3 kg is required to break a foam rod with specific weight 52 kg/m^, distance between storage points 100 ml. Insulation properties: Products manufactured according to the invention are good sound insulators and heat insulators.

Heat conduction coefficient X in kcal/m.hour.°C measured at 24°C.

In addition to the advantageous properties stated above, the method also has the following advantages: the production is quick and can be carried out at room temperature, as there is no need for heated rooms for the foaming and no pre-heated molds either. The method can be carried out by directly using the resins from the condensation, and as the resins are used in aqueous solution, the molecules are more strongly condensed than when working in an alcoholic environment.

Foam resins with the desired specific gravity can be produced with

simple regulation of the propellant addition. The silicone oil and even

tuelt mineral addition helps to give very fine and even cells.

Claims (5)

1. Process for the production of phenolic resin foam, wherein starts from a phenolic resin which is formed by condensation of phenol and formaldehyde in an alkaline medium, possibly in the presence of a copolymerizable substance, for example carbamide_or melamine, and in the phenolic resin mixes a surfactant and a propellant after which the mixture is foamed by activation of the propellant, characterized in that the phenolic resin is in the form of a water solution, that the surfactant is a silicone oil of the silicone-glycol copolymer type that is soluble in water and stable in solution, and that the propellant is selected from among the aliphatic hydrocarbons or their halogen derivatives individually or in mixture which is insoluble in water and which is liquid at normal temperature. 2. Method as stated in claim 1, characterized by using a propellant with a low boiling point, whereby the propellant evaporates in the mixture by raising the temperature of the mixture, which causes the resin to harden. 3. Method as set forth in claim 1 or 2, characterized in that the propellant consists of the following products separately or in a mixture: trichlorofluoromethane, trichlorofluoroethane, petroleum ether, pentane. 4. Method as stated in claims 1-3, characterized in that the curing of the resin and evaporation of the propellant is induced by means of a curing agent consisting of a mineral or organic acid, especially hydrochloric acid, phosphoric acid, sulfuric acid, toluenesulfonic acid or methanenitrobenzenesulfonic acid. 5. Method as specified in claims 1-4, characterized in that the foaming of the resin takes place in the presence of the substances below in the following proportions: water-soluble silicone oil: 0.5 - 5%, preferably 2% polymerization catalyst of the type urea, ammonium chloride, triethylenediamine 0.5% mineral filler of the type silicon dioxide, talc, mica, diatomaceous earth, asbestos, sawdust, glass microspheres, crushed glass fibers, carbon black: 5 - 30%, preferably 10-20% propellant 5 - 40% hardener 5 - 25 SS.