Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-01-10
2001-11-27
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S090000, C522S097000, C522S104000, C522S173000, C522S178000, C522S179000, C522S181000, C522S096000
Reexamination Certificate
active
06323254
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to UV-curable binders and their use for the preparation of high-gloss coatings which can be cured by free-radical polymerization initiated by UV light.
2. Description of the Prior Art
It is known that unsaturated polyester resins, in particular those dissolved in styrene, are suitable for the production of high-gloss coatings on rough or porous surfaces, such as wood. A distinction is made here between paraffin-containing, and air-drying (also called gloss polyesters) types (Glasurit-Handbuch Lacke und Farben. Curt R. Vincentz Verlag, Hannover, 11th edition, 1984). Paraffin-containing unsaturated polyesters are applied in thick layers of up to approx. 1 mm and after curing initiated with (hydro)peroxides and metal siccatives, are usually sanded and polished to a high gloss. Air-drying unsaturated polyesters can cure to a high gloss by themselves, but have a lower reactivity than the paraffin-containing products and usually cannot be readily polished. Air-drying unsaturated polyester resins can also be cured under UV light using photoinitiators. Although this increases the rate of curing, it is difficult to polish the resulting surfaces to a high loss or for repair purposes.
Substantially higher reactivities than with unsaturated polyesters can be achieved by curing unsaturated resins based on acrylate with ultraviolet radiation (according to Glasurit Handbuch Lacke und Farben, reactivity difference factor of 4 to 5. according to W. Fischer, I-Lack 61, 2, 1993, 54 to 58, reactivity difference factor of up to 35). However, compared with unsaturated polyesters, unsaturated acrylates have the disadvantage that it is difficult to cure them in a stress-free form in thicker layers and they cannot be sanded satisfactorily and above all have very poor polishability. Attempts have been made to improve the polishability of these coatings by addition of elastic resins. However, on absorbent or uneven substrates, such as wood, it has been observed that the coatings have very poor adhesion.
An object of the present invention is to provide UV-curable binders, which are suitable for the preparation of high-gloss coatings and do not have the disadvantages of the prior art.
This object can be achieved with the binders according to the invention, which are distinguished by a high reactivity during curing. Coatings produced therefrom have good polishability and stability and form high-gloss surfaces.
SUMMARY OF THE INVENTION
The present invention relates to binders, which can be cured by free-radical polymerization initiated by UV light, and contain
a) 10 to 90 parts by wt. of a polymer which contains, in chemically bound form, both ethylenically unsaturated groups and the reaction product of a resin containing abietic acid with not more than 50% of the OH groups of a polyfunctional alcohol having a molecular weight of less than 500.
b) 10 to 90 parts by wt. of one or more mono-, di- or oligoesters of (meth)acrylic acid having a molecular weight of less than 800 and
c) optionally 0.1 to 10 parts by wt. of a photoinitiator component for the free-radical polymerization
wherein the weights of a) and b) add Lip to 100.
The present invention also relates to coating compositions containing these binders which are suitable for the production high-gloss coatings.
DETAILED DESCRIPTION OF THE INVENTION
Suitable alcohols for reacting with the resin containing abietic acid include dihydric, trihydric or higher functional alcohols having a molecular weight of less than 500. Alcohols which are trihydric or more than trihydric are preferably used, more preferably trihydric alcohols. Examples of dihydric alcohols are those having 2 to 15 carbon atoms such as ethylene glycol, propane-1,2-diol, propane-3-diol, diethylene glycol, dipropylene glycol, the isomeric butanediols, neopentylglycol, hexane-1,6-diol, 2-ethylhexanediol and tripropylene glycol. Preferred dihydric alcohols include ethylene glycol, propane-1,2-diol, propane-3-diol, diethylene glycol and dipropylene glycol. Examples of trihydric alcohols are those having 3 to 20 carbon atoms such as glycerol, trimethylolpropane and alkoxylated derivatives thereof. Trimethylolpropane is particularly preferred. Examples of higher functional alcohols are those having 4 to 20 carbon atoms such as pentaerythritol, ditrimethylolpropane and alkoxylated derivatives thereof. Pentaerythritol is preferred.
Suitable resins containing abietic acid include colophony and its acid-containing derivatives, in particular balsam resins, root resins and tall resins: balsam resins are preferably used. The balsam resins are named according to their countries of origin, for example Portugal or USA, and with AA, Y, X, WW, WG, N, M, K, I or H, according to their brightness. Resins of high brightness, such as WG, WW or X. are preferred. Portuguese balsam resin WW is particularly preferred.
The product Tenex (manufacturer: Bergvik Kemi AB, Sandarne, Sweden), is an example of a suitable root resin. Suitable tall resins include products such as Beviros SG (manufacturer: Bergvik Kemi AB, Sandarne, Sweden), Acintol R-S (manufacturer: Bergvik Kemi AB, Sandarne. Sweden), Sacotan 85 (manufacturer: Krems Chemie, Krems, Austria), Oulo 331 (manufacturer: Veitsiluoto Oy, Oulu Finland), Petrosin 90 (manufacturer: Peterson A/S, Greaker, Norway), Unitol NCY (manufacturer: Union Camp Chemicals, Durham, UK) and Valke Tall Resin A (manufacturer: Valks Chemicals, Valkeakoski, Finland).
The reaction of the resin containing abietic acid with the polyfunctional alcohol is a condensation reaction. This reaction is preferably carried out at elevated temperatures of 100 to 250° C., preferably 140 to 220° C. Water of reaction is distilled off until the acid number of the reaction mixture is less than 15 mg, KOH/g, substance, preferably less than 10 mg KOH/g substance. It is also possible to distill off the water of reaction as an azeotrope with a suitable solvent. After the end of the reaction the solvent is preferably distilled off under reduced pressure. Suitable solvents include toluene, xylenes and aliphatic and cycloaliphatic hydrocarbons; toluene is preferred.
In one embodiment of the process, an esterification catalyst is also present. Suitable catalysts are known and include strong inorganic acids, such as sulfuric acid and phosphoric acid, and strong organic acids, such as p-toluenesulfonic acid and chloroformic acid. To prevent undesirable premature polymerization in the reaction and undesirable severe discoloration, it is preferred to add to the reaction mixture 0.01 to 0.3 wt. %, based on the total weight of the reactants, of known polymerization inhibitors or antioxidants. Examples are described, e.g., in “Methoden der organischen Chemie” (Houben-Weyl), 4th edition, volume XIV/
1
, p. 433 et seq., Georg Thieme Verlag, Stuttgart 1961.
In a preferred embodiment of the process an oxygen-free gas, preferably nitrogen, is passed over the reaction mixture in order to prevent undesirable reactions faith oxygen.
In addition to containing a resin based on the reaction product of abietic acid with a polyfunctional alcohol, polymers a) also contain ethylenically unsaturated groups. These polymers are known for radiation curing and contain OH-functional molecules as starting components. Suitable polymers are described, for example, in P. K. F.
Oldring (ed.), Chemistry & Technology of UV & EB Formulations For Coatings. Inks & Paints, vol. 2, 1991, SITA Technology, London, p. 31 to 235. Examples include urethane acrylates, polyester acrylates, polyether acrylates and unsaturated polyesters. Polyester acrylates and unsaturated polyesters are preferred, and unsaturated polyesters based on maleic acid and/or fumaric acid are particularly preferred.
The preparation of these polymers is modified for the process according to the invention by replacing 1 to 90 mole % (based on OH), preferably 5 to 50 mole % and more preferably 10 mole % of the OH components with the reaction product of a resin containing abietic acid with a polyfunctional
Fischer Wolfgang
Muller Manfred
Weikard Jan
Bayer Aktiengesellschaft
Berman Susan W.
Gil Joseph C.
Roy Thomas W.
LandOfFree
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