Resols, process for their production and use

Details Resols, process for their production and use Resols, process for their production and use

2000-07-17

2002-04-16

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From phenol, phenol ether, or inorganic phenolate

C528S129000, C528S137000, C528S140000, C528S158000

Reexamination Certificate

active

06372878

ABSTRACT:

The invention relates to bright-curing phenolic resins condensed in an alkaline medium.
STATE OF THE ART
Due to their good physical properties and excellent thermal resistance and chemical stability, phenolic resins are used in many fields of application. Unfortunately, they have the disadvantage of becoming discolored during storage and particularly during curing. This strongly restricts the fields in which they can be used particularly as coatings or in the field of varnishes and lacquers (cf. Ullmann's Encyclopedia of Industrial Chemistry, Fifth Edition, Vol. 18, 1991, Page 418).
It is possible to obtain brighter films (cf. Knop, Pilato: Phenolic Resins; Springer Verlag 1985, Page 248) by etherification of the resols. Etherified resols, however, have the disadvantage that they are not water-dilutable or only to a limited extent. In addition, they have longer curing times which means lower reactivity than non-etherified resols. The resins, furthermore, still contain solvents or, at elevated temperatures, their cleavage results in by-products, most often alcohols, used for the etherification.
It is known from EP-A 0 442 218 that color-stabilized phenolic resols catalyzed with an alkali metal hydroxide can be produced by adding ammonia salts or complexes and the addition of these salts stabilizes the color of the resins when curing them at temperatures up to 150° C. However, the brightening effect is insufficient, especially if these resols are cured at higher temperatures.
OBJECTS OF THE INVENTION
It is an object of the invention to provide resols with good water-dilutability properties, which are not discolored and which are bright-curing even at elevated temperatures without the chemical and physical properties of the cured products being degraded.
It is another object of the invention to expand the fields of application of phenolic resins.
These and other objects and advantages of the invention will become obvious from the following detailed description of the invention.
DESCRIPTION OF THE INVENTION
The resols of the invention are modified with at least one member selected from the group consisting of organic phosphonic acid, organic phosphinic acid and their alkali metal and alkaline earth metal salts. The resins are preferably used as binder for abrasive grain in grinding materials, particularly as size coat binder in coated abrasives or as binder for coatings, printing inks, adhesives, lacquers, molding materials, particularly bright molding materials, foams or formed fiber elements or for the production of laminates, particularly decorative laminates and as impregnation resins.
It has been found that resols modified with organic phosphonic acids and/or phosphinic acids or their alkali and or alkaline-earth metal salts are bright and transparent, that they remain bright even after relatively long storage periods and they do not become discolored even during curing at temperatures up to 150° C.
It is known from EP-A 14625 to make transparent polycarbonates produced from bisphenols, phosgene and a diester or an alkali metal hemiester of a phosphonic acid. However, this process cannot be applied in the case of resols as no brightening is attained through addition of phosphonic acids or salts of phosphonic acids to resols.
However, it has been found that bright resols are formed if, before the condensation reaction comprising phenolic compounds, aldehydes and alkaline condensation reagents, are added organic phosphonic acid(s) and/or phosphinic acid(s) or their alkali and/or alkaline-earth metal salts are added to the reaction mixture. The phenolic compound(s) and the organic phosphonic acid(s) and/or phosphinic acid(s) or their alkali or alkaline-earth metal salts are preferably mixed with one another before the addition of the alkaline catalyst. The organic phosphonic acids as well as the phosphinic acids or their salts react during the condensation reaction with one or several components of the reaction mixture whereby the bright resols modified with organic phosphonic acids and/or phosphinic acids are formed. The reaction has not been specified so far.
To carry out the akaline condensation reaction, phenolic compounds and aldehydes are used in a molar ratio of 1:0.3 to 1:6. As alkaline catalysts, all compounds known for the resol production, such as, for example, alkali and/or alkaline-earth metal hydroxides, ammonia or amines, alkali metal sulfites can be used and, specifically for the ortho-condensed resols, organic salts of bivalent metals such as, for example, zinc acetate (cf. Houben Weyl, Vol. E20 “Makromolekulare Stoffe”, part 3 (1987), page 1804). The amount of catalyst used is also within the range conventional in known phenolic resols syntheses. The condensation reaction takes place in a manner known per se by heating the reagents for several hours in aqueous alkaline solution.
Examples of the phenolic compounds are preferably phenol, but also aliphatically or aromatically substituted phenols, as well as multivalent phenols. Specific examples are cresols, xylenols, tert.butyl or octyl phenol, naphthols, p-phenyl phenol, bisphenols or resorcinol, but also natural substances, such as, for example, tannins, cardenol or cardol. The phenolic compounds can be used as single compounds or in any desired mixture with one another.
Examples of aldehydes which can be used are all compounds of the formula R—CHO where R is alkyl or cyclic for example. Specific examples are formaldehyde, acetaldehyde, propionaldehyde, n-butyric aldehyde or iso-butyric aldehyde, glyoxal or furfural. The preferred aldehyde is formaldehyde, which is used as such or in the form of a substance that cleaves off formaldehyde such as, for example, paraformaldehyde or trioxan. The preferred form of adding it is an aqueous solution with a formaldehyde content of more than 30% (formalin).
Organic phosphonic acids usable according to the invention are organic derivatives of phosphonic acids in which one or several of the groups —PO(OH)
2
are bound directly to a carbon atom, and the organic radical can be unsubstituted or substituted alkyl, cycloalkyl, aryl, aralkyl, hetero, heteroalkyl or heteraryl group. Accordingly, the compounds have one or several P—C bonds. Alkyl phosphonic acids are preferably used, in which a branched or unbranched alkyl chains of 2 to 20 carbon atoms is present, to which at least 2 —PO(OH)
2
groups are bound. Preferred are such alkyl phosphonic acids which are additionally substituted with one or several polar substituents such as —OH, —OR, —COOH, —COOR, halogen, ≡N, —NH
2
, —COR or —NO
2
. Also usable are nitrile derivatives, such as, for example, nitrilotris(alkylene phosphonic acids), particularly nitrilotris(methylene phosphonic acid). Usable salts of these phosphonic acids are the alkali metal and/or alkaline-earth metal salts with all or only a portion of the phosphonic acid groups being present as the salt.
Phosphinic acids are compounds having the formula R
1
R
2
P(O)OH, wherein R
1
and R
2
are organic residues and can be identical or different. The organic residues can be unsubstituted or substituted alkyl, cycloalkyl, aryl, arylalkyl, hetero, heteroalkyl or heteroaryl groups. Accordingly, the compounds have P—C bonds and preferably used are dialkyl phosphinic acids in which branched or unbranched alkyl chains of 2 to 20 carbon atoms are present to which at least 2 —PO(OH)
2
groups are bound. Particularly preferred are dialkyl phosphinic acids in which the alkyl chains are additionally substituted with one or several polar substitutents such as OH, —OR, —COOH, —COOR, halogen, ≡N, —NH
2
, —NR
2
, —COR or —NO
2
. Usable salts of these phosphinic acids are the alkali metal and/or alkaline-earth metal salts, with all or only a portion of the phosphinic acid groups being present as the salt.
The organic phosphonic acid or a mixture of organic phosphonic acids or, respectively, the phosphinic acid or a mixture of phosphinic acids, or a mixture of phosphonic and phosphinic acids, respectively, or their salts or mixtures of corresponding alkali metal or a

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