NO132483B - - Google Patents

Description

The invention relates to a method for the production of phenolic resin foam which, when stored at temperatures between 30 and 80°C, only slightly shrinks during production, and which, compared to known phenolic resin foam, has little weight loss when stored for longer periods in a normal climate.

Phenolic resin foams, which are produced by foaming liquid hardeners and surfactant-containing phenol resole resins in open or closed vessels in the presence of a solid or liquid propellant, have the disadvantage that they undergo a shrinkage that increases with increasing temperature. This shrinkage means that when insulating large surfaces, e.g. ceilings with phenolic resin foam boards, occurs

openings between these plates, so that thermal bridges form between the individual plates.

Furthermore, the phenolic resin foams produced according to the known methods have the disadvantage that the volatile substances contained therein, predominantly water and propellant residues, partially evaporate during longer storage at room temperature or at elevated temperature. Thereby, water vapor blisters are formed under the casing material when casing phenolic resin foam with strongly water vapour-tight, soft, expandable materials, which often leads to solution or for bulging of the casing material.

The invention relates to a method for the production of phenol resole resin foams with a reduced tendency to shrink when foaming in open or closed forms of mixtures consisting of liquid phenol resole resins produced by condensation of phenols and aldehyde in a molar ratio of 1:1 to 3 as well as solid or liquid propellants, liquid or solid hardeners , smaller quantities of surface-active substances and calcium sulphatej in that the method is characterized by adding 5-50% by weight, preferably 10-30% by weight, of CaSO^ to this mixture before foaming in powdered form. J H 2 O, referred to the solids portion of the phenol aldehyde resin.

The addition according to the invention of calcium sulphate clearly lowers the shrinkage of newly produced phenolic resin foams during storage at an elevated temperature. Similarly, the weight loss is reduced during storage under normal conditions (2 3°C and 50% relative humidity). Thereby, it surprisingly turned out that even with the addition of 30 wt# of CaSO|j j H20, the fluidity of the mixture to be foamed was so good that it could be processed in double belt presses into phenolic resin foam sheets. With a correspondingly high addition of hitherto known finely powdered fillers to the starting materials for the phenolic resin foams, this good processability was not present.

It was surprising that by adding CaSO^ .

There is no obstruction of the foam formation or non-structural formation of the foam as expected, at such large "amounts"

of a finely powdered, specifically heavier filler and as was already observed. by a very high addition of e.g. finely powdered Na2S02|, ZuC^, kaolin eels mica.

When the phenolic resin foams produced according to the invention are produced using solid, powdered acids for curing, there is also an increase in the compressive strength at the same foam density.

The calcium sulphate used can contain up to 5% other calcium salts or also sulphates of alkali and alkaline earth metals, as well as zinc and aluminum sulphate. The addition of alkali carbonates, bicarbonates and chlorides in the same order of magnitude is also possible without the properties of the phenolic resin foam produced according to

the invention deteriorates.

The size of the calcium sulphate particles can be varied within relatively wide areas. Even calcium sulfate grains with a diameter of 5 mm can be used. However, it pays to use a grain size below 1 mm, preferably below *0.001 mm.

The production of the foams usually takes place by mixing a phenolic resin well with liquid or solid hardener, surfactants, a propellant and calcium sulphate and allowing it to foam and harden in open or closed vessels.

Phenolic resol resins which are suitable for the production of. the phenolic resin foams according to the invention are obtained. e.g. by condensation of one mole of a phenol with 1 to 3 moles of aldehyde in an alkaline medium, followed by distillation in a vacuum and possibly setting the pH value to values higher than 4. As phenols, both hydroxybenzene and its homologues can be used such as cresol and resorcinol, xylenol or mixtures of these compounds. The aldehydes that react with the phenols include formaldehyde, to formaldehyde

degradable compounds, such as paraformaldehyde or trioxane, acetaldehyde and the like as well as mixtures of these compounds.

The condensation is carried out in an aqueous alkaline medium.

The compounds used as propellants also include solid compounds of which heat releases inert gases, preferably carbon dioxide, as well as low-boiling organic solvents. The solid propellants e.g. ammonium carbonate or ammonium bicarbonate should, as completely as possible, give off gases or leave a residue that is odorless and does not attack the foam, such as e.g. alkali carbonates and bicarbonates.

Furthermore, both inorganic and organic peroxides can be used, as well as azo compounds such as e.g. a,a-azodi-isobutyric acid nitri1. Liquid propellants include low-boiling organic solvents such as chloroform, carbon tetrachloride, chlorofluoromethane, n-pentane, n-butyl ether, petroleum ether, ethylene dichloride.

The solid propellants are used in amounts from 0.3 to 10% by weight, referred to phenolic resin resol. The addition of the liquid propellants takes place in quantities between 1.0 and 20.0 by weight, referred to the phenol resol resin.

Both liquid and powdered acids can be used as hardeners. The required quantities partly depend on the propellant used. If this consists of a solid gas-evolving salt, part of the acid is used to release the gas. When using low-boiling solvents as a propellant, the amount of hardener is correspondingly lower. As water-soluble acids are suitable next to it

of mineral acids (HC1, HgSO'^) especially well dissolves soluble sulphonic acids, where the sulphonic acid group is connected directly with an aromatic ring which may optionally be substituted. Examples of this are: benzenesulphonic acid, p-toluenesulphonic acid, chlorobenzene-3,5-disulphonic acid,

bromobenzene-4-sulfonic acid, the o-m- and p-cresolsulfonic acids or amino-2,5-disulfonic acid. The sulfonic acid group can also be connected to a polynuclear aromatic residue, such as e.g. by the haften sulfonic acids or the naphthylamine sulfonic acids. But also aliphatic sulphonic acids can be used as hardeners, such as e.g. butylsulfonic acid, propylsulfonic acid or hexylsulfonic acid.

The aqueous solution of these acids, e.g. p-toluenesulfonic acids, can also be used in powdered form, as a hardener. The amount of hardener used is between 1.0 and 15.0 by weight)8, calculated as 100% acid, referred to the weight of the phenol resole resin.

The surface-active agents are used in amounts of 0.M - 10% by weight, preferably 1.5% by weight, referred to the phenol resole resin.

Suitable surfactants are, for example: Polyethylene ether of a long-chain monofatty acid ester of sorbitol, e.g. of polyethylene ether of monolaurin sorbitol ester and of polyethylene ether of mdnoolein sorbitol ester and water-insoluble ethoxylated castor oil.

The foaming of the phenolic resin takes place after the individual components have been mixed together. Thereby, the propellant changes to a gaseous state. Depending on the composition of the mixture to be foamed, the foaming takes place at temperatures between 0 and 100°C, preferably at 15 to 60°C. The resin can be foamed in both open and closed forms, and then foam moldings are obtained depending on whether open or closed forms are chosen.

It is also possible to carry out the foaming continuously in a double belt press. Thereby, the components are dosed using known automatic dosing or mixing devices and the mixture is continuous using a charging device on the belts of a double belt press. The mixture is then passed between rollers and a possibly roller-shaped substrate formed by a gap of selected thickness.

The rollers can thereby possibly be preheated. With this method, plates of the desired thickness are obtained.

Curing is usually controlled in such a way that - as soon as the desired foam volume is achieved - the foam structure is fixed to such an extent that no overlap occurs.

Known fillers and/or pigments, such as air-containing or porous powdered inorganic or organic substances and titanium dioxide, can also be added to the phenol resole resin before foaming.

It is also possible to use modified phenol resol resins for the production of the phenol resin foams according to the invention. Examples of modifiers include: ■ furfurol, furfuryl alcohol, unsaturated hydrocarbons, saturated and unsaturated esters and polyesters, ketones e.g. acetone and similar agents.

The solid resin content of the phenol resole resin is determined on

the following way:

2 g of the resole is heated at 150°C for 90 minutes in an iron bowl, then the residue is weighed.

Examples.

Two Fendl resin resoles A and B were prepared in the manner described below, which were well mixed, each time with different amounts of propellant and calcium sulfate. \H20.

H arpiks A.

143 parts by weight of phenol are condensed with 228 parts by weight of

a 30% solution of formaldehyde in water with the addition of 0.715 parts by weight of sodium hydroxide in aqueous solution at 100°C for 70 min. The resulting reaction mixture is then distilled off in

vacuum to a fixed resin content of 72 to 7856. As a surface-active compound for cell resp. pore regulation is added 3 weight/6, referred to the phenolic resin resole of a castor oil made water-soluble by ethoxylation with an average degree of ethoxylation of 40. The resin thus produced has a viscosity of from 4000 to 7000 cP at 20°C according to Hopplerv

Ha rpik's B.

143 parts by weight of phenol are condensed with 243 parts by weight of a 3056-ig aqueous formaldehyde solution while adding 4.3 parts by weight of sodium hydroxide in aqueous solution at 100°C for 50 min. The resulting reaction mixture is distilled off using vacuum to a solid resin content of 70 to 7556' and is then mixed with 3 wt. of the cell regulator referred to under "resin A". The resin then present has a viscosity of 3000 to 5000 at room temperature

cP according to Hoppler.

The phenol resol resins are mixed with the quantities mentioned in table 1 of a hardener mentioned below, n-pentane as a propellant and calcium sulphate. 1^0. The foaming takes place in examples 1-6 so that the good mixture of the components was filled in box forms open at the top with a base surface of 50 cm x 50 cm and a height of 100 cm. The foaming took place during simultaneous increasing hardening at 40-70°C during 30 to 90 min. After approximately 120 min. could the hardened foam blocks be removed from the mold. They were cut into slabs after complete cooling.

For the continuous production of phenolic resin foam sheets (examples 7-13), the components were dosed using the known automatic dosing and mixing devices and mixed and the mixture held continuously between them until approx. 50°C heated belts of a double belt press., After a residence time of approx. 12 min. between the bands that moved, the foamable mixture fills the prescribed volume. The endless sheet path that leaves the double-belt press is terminated by means of a cross-cutting device into individual sheets.

The following hardeners were used in the experiments.

Hardener I: 100 parts by weight glycol,

100 parts by weight of hydrochloric acid (37#-ig).

Hardener II: p-toluenesulfonic acid, dissolved in dilute, aqueous

sulfuric acid.

Hardener III: finely powdered p-toluenesulfonic acid.

Hardener IV: mixture of 10.0 parts by weight of p-toluenesulfonic acid, finely powdered,

20.0 parts by weight boric acid, finely powdered, 0.2 parts by weight silicon dioxide.

The foam lids produced according to the individual examples resp. foam boards had the properties mentioned in table 2.

A phenol resol resin corresponding to the resin in trial number 9 was foamed while adding 20 parts by weight of CaSO 4 . 2 H20 (instead of 20 parts by weight of CaSO^ . J H20) and stored a total of 28 days at 50°C. The weight loss was already 15% after 8 days and increased up to 28 days' to 1Q%. The loss reached after 8 days Q, h5% and after 28 days 0.55%.

Claims (1)

Process for the production of phenol resole resin foams with a reduced tendency to shrink by foaming in open or closed forms of mixtures consisting of liquid phenol resole resins produced by condensation of phenols and aldehyde in a molar ratio of 1:1 to 3 as well as solid or liquid propellants, liquid or solid hardeners, smaller amounts of surfactants and calcium sulphate, characterized in that 5~50 wt#, preferably 10-30 wt? CaSOjj . H 2 O, referred to the solid part of the phenol aldehyde resin.