DE2549441A1 - HARDER FOAMABLE MIXTURES - Google Patents

Description

IiIS-GFKrYAG. Cr- ': ÜC:'. · :. -.- ί

Car-e 3-964fc'MIiL 227 / +

Germany

HARDER CONTAINING SCF ^ EUi-IBARE MISCHlRiGEN

The present invention relates to foamable mixtures containing phenol-formaldehyde-Re so Ie and Hardener, and also a process for the production of foams using such mixtures.

Manufactured from phenol-formaldehyde resoles Foams are well known. They are made by mixing the resole, optionally in the presence of a surface-active substance, with a blowing agent (blowing agent "i and an acidic hardener, which on the one hand hardens the resin and on the other hand either generates enough heat to volatilize the blowing agent or react with the blowing agent to release a gas. Many of the Problems which have been shown in the commercial production of phenol-formaldehyde foams caused by the difficulty of the speeds

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to coordinate the hardening of the resin and the generation of steam. If too much heat is generated during the reaction between the resin and hardener, the blowing agent will evaporate very quickly or generate gas and the resin will harden quickly, producing a foam with a few, very large cells. On the other hand, if too little heat is generated to cause adequate volatilization or gas formation, the resin will cure without expanding in any substantial part. Gradations can be achieved between these two extremes, with either satisfactory or unsatisfactory foams.

An ideal combination of resin and hardener would generate heat in an even, controlled manner with the formation of a foam with consistently uniform cell size, preferably small, closed ones Cells.

We have now found that this requirement can at least largely be met using of various phenol-formaldehyde res oils, if the The hardener is an aqueous solution containing resorcinol formaldehyde novolak and a strong acid. Such hardeners are known from British Patent No. 1,248,756 for use in curing methylolated products

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in the 'production of molds and coil cores. We have found that solutions can be made with a viscosity of the same order of magnitude such as the viscosity of the phenolic resoles used; the mixture of these solutions with the phenolic resole therefore results in no problems and homogeneous mixing can be easily obtained. The reaction between resole and hardener solution results in a uniform, regulated reaction Heat is generated and a foam with very small cells is created. By modifying the nature of the surface active Substance and the acid, the cells can be produced predominantly open or closed, depending on the requirements. Such a foam usually has a higher compressive strength than a foam with a usual acidic Has been made harder and usually also has better fire resistance, especially when the cells are are closed.

The resorcinol-formaldehyde novolak acts as a crosslinker for the resol, which is why less acid is required than when using a conventional hardener. The foam therefore has little residual acidity and is therefore less corrosive to metals, which are thus in Get in touch. The novolak also reacts with all of the free formaldehyde in the resole, which is why the foam

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does not have the characteristic pungent odor of formaldehyde, which is present in a foam is made using a common hardener became. A wide variety of resols can be used successfully with the solutions of the present invention be foamed, even those which are normally considered to be too unreactive or not very viscous to be foamed with conventional means.

Accordingly, the present invention relates to a self-expanding, self-setting composition for the production of foams through a homogeneous mixture

(a) a phenol-formaldehyde resole,

(b) an aqueous solution containing a resorcinol-formaldehyde novolak and an acid whose pK -, - value is 2.2 or less, and

(c) a blowing agent,

and also foams, manufactured

represents from such a crowd.

For the sake of simplicity, acids with a pK value of 2.2 or less are referred to below as "strong acids" designated.

Another object of the present invention is a method for producing a synthetic

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Resin foam, characterized by homogeneous mixing of a phenol-formaldehyde resole with an aqueous solution containing a resorcinol-formaldehyde novolak and a strong acid, and with a blowing agent and by Schaurneη and hardening of the mixture,

as well as according to this procedure -— —-— ~ - · ——. — ... "..,

manufactured foams.

The phenol-formaldehyde resoles used in the present invention are known compounds and are conventionally prepared by heating a monohydric phenol such as a cresol or a Xylenol, but preferably of phenol itself with aqueous formaldehyde solution, the molar ratio Phenol: formaldehyde 1: 1.2 to 1: 3, usually in the presence of an alkali such as sodium hydroxide or Ammonia.

The resorcinol-formaldehyde novolaks used in the present invention are also known compounds and are usually produced by reacting resorcinol with aqueous formaldehyde solution in a molar ratio Resorcinol: formaldehyde 1: 0.5 to 1: 0.95. The reaction is preferably carried out in the presence of a trace Acid carried out at temperatures between 50 and 100 ° C.

Any strong acid can be used because of

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easy handling and easy accessibility, however, preference is given to using hydrochloric acid, phosphoric acid or an aromatic sulfonic acid, usually in aqueous solution, such as benzenesulfonic acid, ortho- or Para-phenolsulfonic acid and toluene-para-sulfonic acid, where the latter is particularly preferred.

The aqueous solutions used in the present invention preferably contain 5 to 60% by weight Resorcinol formaldehyde novolak, 30 to 80% strength by weight Acid and 5 to 40% by weight water. Particularly preferred solutions contain 10 to 40 wt.% Novolak, 40 to 70% by weight strong acid and 10 to 30% by weight water.

The amount of the solution used for hardening depends, apart from other influences, on it Nature and that of the resin and blowing agent. In general, 10 to 50 parts by weight of the aqueous Solution (b), based on 100 parts by weight of resole, is used, 15 to 35 parts by weight are preferred.

Blowing agents suitable for the production of foams according to the present invention can be solid or be liquid. The choice of blowing agent depends on the nature of the resin used and on the Type of hardener and also the desired properties of the end product. Preferred blowing agents are inert ones, with

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Water, however, "immiscible liquids which boil at Atmosphiirendruck between 30 and 100 ⁰ C. Outside this range boiling solvents are also useful. The amount ratio of the blowing agent is dependent on the density of the foam desired, higher weight ratios naturally foams result of lower density. The appropriate weight ratio can easily be found through routine experimentation, it is usually about 10 to 25% by weight based on the resole (a).

Examples of preferred blowing agents are paraffins such as n-pentane and polyhalogenated saturated fluorocarbons such as 1,1,2-trichloro-1,2,2-trifluoroethane. Compounds which decompose at the curing temperature and develop a gas can also be used, such as 2,2'-azobis (2-methylproprionitrile), ρ, ρ ¹ -oxybis- (benzenesulfonyl hydrazide), azodicarbonamide and dinitrosopentamethylenetetramine. Suitable blowing agents are also compounds which react with the acid to form gas, such as sodium and ammonium hydrogen carbonate. The latter type, which is generally solid, is not preferred because it cannot be evenly distributed as easily as immiscible liquids which are in the mixture

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can be emulsified.

The foams can also contain fillers such as talc or gravel, silicone oils and nonionics surface-active substances such as ethylene oxide addition products. As shown in Example 2 below, the surfactant type has one significant influence on the amount of closed cells, on the cell size and on the distribution of the Cell size. The larger the hydrophobic chain in the surface-active Normally, the smaller the cell size in the foam, the smaller the fabric. The relationship between the chemical nature of the surfactant and the contents of the closed cells is not clear, though it has already been said that the compatibility of the surfactant with the blowing agent is one A suitable surfactant (or mixture of such agents) to form a Foam with the desired cell size and with a desired ratio of closed cells can can also be found using routine test methods.

Foams produced according to the present invention can be used in individual batches or else are produced continuously and are suitable for insulation against noise and heat, as casting molds

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and as an energy-absorbing structure.

The following examples illustrate the invention. All parts and percentages are based on weight and the temperatures are given in degrees Celsius.

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example 1

Resorcinol (19.5 parts) was suspended in water (2.76 parts), heated to 60 °, and a 65% aqueous solution of toluene parasulfonic acid (0.04 part) was added. The mixture was heated to 95 °, a clear solution formed, and an aqueous formaldehyde solution (38.3% CH ₂ O; 11.1 parts) was added over the course of 1 1/2 to 2 hours, while maintaining a temperature of 95 °. A solution of a resorcinol / formaldehyde novolak resulted with a resorcinol / formaldehyde molar ratio of 1: 0.8.

This novolak solution was cooled to 50 ° and with a 65% solution of toluene-para-sulfonic acid (66.6 parts) offset. The resulting mixture was concentrated in vacuo at 35 to 40 ° to such an extent that the concentrate became one Has a water content of 20%. This residue had a viscosity of 720 mPas (MilliPascal seconds) at 25 ° and an acidity of 3.25 equivalents per kg. A phenol-formaldehyde resole with a molar ratio Phenol: formaldehyde of 1: 1.6 (100 parts), 1,1,1-trichloro-2,2,2-trifluoroethane (15 parts) and a poly (oxyethylene) nonylphenol adduct (1 part, made from ethylene oxide and nonylphenol in a molar ratio of 9: 1) were mixed together, resulting in a homogeneous mixture at 25 °.

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For this purpose (20 parts) the novolac-toluene-para-sulfonic acid mixture described above given and vigorously stirred until an even emulsion was created. After 25 seconds the mixture started to foam and when the foam was done it had

3
a density of 34.4 kg / m. The residual acidity of this foam was 0.03 equivalents per kg and the average

3 Average cell size was less than 0.003 mm.

Example 2

To test the effects of various surfactants on the nature of the foam, Example 1 was repeated using 25 parts of trichlorotrifluoroethane and 1 part of various surfactants. The results are shown in Table 1 below.

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Table 1

Received
3
Density (kg / πι)
- ' r foam
7th
/O
closed
Cells j Whether he is flat active connection 28.6 78.4 Polyoxyethylene phenol 33.4 87.0 j Polyoxyethylene alkylaryl ether 43.8 4.1 Polyoxyethylene castor oil 54.9 O Polyoxyethylene sorbitol mono-
palmitate
. '. ■■. ■ ■' ■

Example 3

10 parts of a resorcinol-formaldehyde novolak, similar to that used in Example 1 was mixed with 60 parts of a 65% solution of toluene-p-sulfonic acid and in vacuo concentrated at 35 to 40 ° to a water content of 20%. The viscosity was 68 mPas and the acidity was 3.9 Equivalents per kg.

The processing described in Example 1 was repeated using 100 parts of phenol-formaldehyde resole, 25 parts of 1,1,1-trichloro-l, 1,1-trifluoroethane, 1 part of ethylene oxide-nonylphenol adduct and 16.5 parts the novolac acid mixture described above.

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After 25 seconds the mixture began to foam and gave

3 a foam with a density of 29.9 kg / m, a residual acidity of 0.05 equivalents per kg, a through-

average cell size below 0.003 mm and one Closed cell content of 67.7%.

Example 4

A resorcinol-formaldehyde novolak, similar to that used in Example 1, was mixed with the same amount of a 65% solution of toluene-p-sulfonic acid and ^{concentrated in vacuo at 35 to 40 ° C.} until the water content was 20%. The viscosity was 800 mPas and the acidity was 2.66 equivalents per kg.

The further processing took place as in Example 3, whereby the novolak acid mixture of Example 3 by 33 parts the novolak-acid mixture described above became.

After 20 seconds the mixture began to foam and

3 gave a foam with a density of 28.9 kg / m 2, a residual acidity of 0.032 equivalents per kg, one

average! Cell sizes below 0.003 mm and a closed cell content of 83.5%.

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Example 5

20.24 parts of resorcinol were suspended in 9.22 parts of water and 0.04 parts of a commercial mixture of o- and p-phenolsulfonic acid added. The mixture was mixed at 95 ° within 1 1/2 to 2 hours with 10.74 parts of a 38.3% formaldehyde solution. the The resulting solution of a resorcinol-formaldehyde novolak had a molar ratio of resorcinol: formaldehyde of 1: 0.75. After cooling to 50 °, 59.76 parts of phenolsulfonic acid were added. The mixture was in vacuo concentrated at 35 to 40 ° until the water content was 10%. The concentrate had a viscosity of 1C50 mPas and an acidity of 3.5 equivalents per kg. The procedure was then as in Example 3, the Novolak acid mixture of Example 3 by 20 parts the Novclak acid mixture described above. After 20 seconds the mixture began to foam

and resulted in a foam with a density of 28 kg / m 2, a residual acidity of 0.03 equivalents per kg, one average cell size below 0.003 mm and a closed cell content of 4%.

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Example 6

13.04 parts of resorcinol were suspended in 1.66 parts of water and mixed with 0.04 part of toluene-p-sulfonic acid. 7.47 parts of a 38.3% aqueous formaldehyde solution were obtained at 95 ° in the course of 11/2 to 2 hours admitted. The resulting solution of a resorcinol-formaldehyde novolak would have a molar ratio of resorcinol: formaldehyde of 1: 0.8.

44.44 parts of a 65% toluene-p-sulfonic acid and 33.34 parts of 85% phosphoric acid were added to this solution at 50 °. The water content was adjusted to 15% by concentration in vacuo at 35 to 40 °, so that the acidity was 7.46 equivalents per kg. Processing was then carried out as in Example 3, the novolak-acid mixture from Example 3 being replaced by 20 parts of the mixture described above. After 40 seconds, the mixture began to foam and gave a foam with a density of 30.0 kg / m, a residual acidity of O ₅ 67 equivalents per kg, a thorough-

3 average cell size of 0.01 mm and a content on closed cells of 2%.

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Claims (16)

Claims 1. A self-expanding, self-curing composition for making foams, featured through a homogeneous mixture (a) a phenol-formaldehyde resoil, (b) an aqueous solution containing a resorcinol-formaldehyde novolak and an acid with a pK, value of 2.2 or less and (c) a blowing agent. 2. A composition according to claim 1, wherein the solution (b) 5 to 60 wt .-% novolak, 30 to 80 Contains wt .-% acid and 5 to 40 wt .-% water. 3. A composition according to claim 2, wherein the solution (b) 10 to 40% by weight of novolak, 40 to 70% by weight Contains acid and 10 to 30% by weight of water. 4. A composition according to claims 1 to 3, wherein the novolak used was produced by the implementation of resorζin with aqueous formaldehyde solution in a molar ratio of resorcinol: formaldehyde 1: 0.5 to 0.95. 609 ^ 20/1026 5. A composition according to claims 1 to 4, wherein the acid used is hydrochloric acid, phosphoric acid, benzenesulfonic acid, o-phenolsulfonic acid, is p-phenolsulfonic acid or toluene-p-sulfonic acid. 6. A composition according to claims 1 to 5, wherein the phenol-formaldehyde resole from phenol itself is made. 7. A composition according to claims 1 to 6, wherein the resol used was prepared by Reaction of a phenol with aqueous formaldehyde in a molar ratio of phenol: formaldehyde 1: 1.2 to 3. 8. A composition according to claims 1 to 7, containing 10 to 50 parts by weight of the aqueous solution, based on 100 parts by weight of resol. 9. A composition according to claim 8, containing 15 to 35 parts by weight of the aqueous solution, based on 100 parts by weight of resol. 10. A composition according to claims 1 to 9, wherein the blowing agent is an inert, water-immiscible 609820/1026 bare liquid boiling at 30 to 100 °. 11. A composition according to claim 1, im essential as described therein. 12. A composition according to claim 8, essentially as described in one of the examples. 13. Method of making a synthetic Resin foam, characterized by the formation a composition as described in the preceding claims and subsequent foaming and hardening the composition. 14. The method according to claim 13, essentially as described therein. 15. The method according to claim 14, essentially as described in the examples. 16. Foams, characterized by the production according to one of the claims 13 to 15 claimed Procedure. 60 9820/1026