Coating processes – With post-treatment of coating or coating material – Plural film forming coatings wherein one coating contains a...
Patent
1996-11-06
1999-02-09
Cameron, Erma
Coating processes
With post-treatment of coating or coating material
Plural film forming coatings wherein one coating contains a...
427340, 427314, 4274073, 427426, B05D 102, B05D 134, B05D 136, B05D 302
Patent
active
058691421
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for improving the mechanical properties of a glass-fiber mat obtained by applying a binder containing an aqueous phenolic condensation resin to the mat and hardening the binder.
2. Discussion of the Related Technology
Glass-fiber mats are used mainly as thermal insulating material. The binder is supposed to bind the fibers firmly together to obtain a coherent structure. The binder is at the same time supposed to ensure sufficient elasticity of the insulating material and high recovery thereof after compression so that the insulating material can be stored, transported and deformed for use at the final location.
U.S. Pat. No. 4,663,419 discloses using for a glass-fiber mat a binder containing a condensation product from phenol, formaldehyde and urea condensed in the presence of a basic catalyst, and additional urea and further additives, namely silane, mineral oil, ammonia and ammonium sulfate. The binder is sprayed as an aqueous solution on the raw mat that is then pressed and put in the desired form for the insulating material, for example a panel or a pipe, after which it is fed to a curing oven where the binder is hardened.
U.S. Pat No. 4,176,105 discloses a binder for a glass-fiber mat which is obtained by reaction of a phenol-formaldehyde-urea condensation resin with boric acid and urea. Per 100 parts by weight of phenol-formaldehyde-urea condensation resin 12 to 16 parts by weight of boric acid are added. When the resin hardens a boric acid complex is formed. This is intended to increase the resistance of the binder to punking at high temperatures.
However, known binders leave something to be desired with respect to the mechanical strength of the glass-fiber mat, in particular the tensile strength and the recovery after compression of the mat, especially after it has been stored for some time.
SUMMARY OF THE INVENTION
The invention is therefore based on the problem of improving the mechanical properties of a glass-fiber mat.
This is obtained according to the invention by adding a weak acid with a pK value of more than 4, in particular more than 5, to the glass-fiber mat before hardening the binder.
The pK value is defined as the negative decadic logarithm of the acid dissociation constant at 25.degree. C.
DETAILED DESCRIPTION OF THE INVENTION
The weak acid is preferably added in an amount of 0.5 to 10 percent by weight, in particular 1 to 5 percent by weight, based on the solids content of the phenolic condensation resin of the binder. When the acid is added in an amount of less than 0.5 percent by weight no improvement of the mechanical properties is observed. On the other hand, no further improvement occurs, but actually a reduction of the mechanical properties, when the amount of weak acid exceeds 10 percent by weight.
The amount of binder, including the additives and the weak acid, after hardening is 3 to 7, preferably 4 to 6, percent by weight based on the total weight of the mat. The amount of weak acid after hardening of the binder is 0.05 to 1, preferably 0.08 to 0.6, percent by weight based on the total weight of the mat.
Suitable weak acids are in particular boric acid and carboxylic acids with a pK value of more than 4, in particular more than 5.
The carboxylic acid can be a monobasic or polybasic carboxylic acid with or without hydroxyl groups, for example citric acid or a fatty acid. Fatty acids with more than 8 carbon atoms, such as lauric, palmitic, stearic or oleic acid, have proven particularly suitable, in particular fatty acids with one or more C.dbd.C double bonds such as oleic acid.
The phenolic condensation resin of the binder is preferably a water-soluble condensation product from phenol and formaldehyde or from phenol, formaldehyde and urea, the condensation being performed in the presence of a basic catalyst, in particular an alkaline or alkaline-earth metal hydroxide, for example sodium, potassium, calcium or barium hydroxide. The phenolic condensation resin can be produced for exa
REFERENCES:
patent: 4176105 (1979-11-01), Miedaner
patent: 4255485 (1981-03-01), Yau
patent: 4663419 (1987-05-01), Fugier et al.
Joachim Jacky
Lericque Bernard
Cameron Erma
Isover Saint-Gobain
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