Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-12-11
2004-02-03
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S451000, C524S493000, C524S513000, C524S514000, C524S560000, C524S590000, C524S600000, C524S601000, C524S602000, C524S604000, C524S612000
Reexamination Certificate
active
06686412
ABSTRACT:
The invention relates to preparations of flatting and texturing agents for incorporation in coating compounds, more particularly in low-emission, high-solids coating compounds, and to the coating compounds containing the flatting and texturing agent preparations. The coating compounds are used preferably in vehicle and vehicle part lacquering.
For certain applications in vehicle and industrial lacquering it is necessary to prepare lacquers which result in surfaces with reduced gloss and/or textured surfaces. For example, lacquered commercial vehicle bodies should have matt surfaces and plastics parts, e.g., external trim parts on vehicles such as bumpers should receive dull and/or textured surfaces. In order to obtain the matt and/or textured surfaces, flatting agents or texture additives are added to the coating compounds. When the applied lacquer film dries, the flatting agent particles produce a microrough surface texture. As a result, the incident light is reflected in a diffuse manner and gives the observer the impression of a matt surface. The flatting agent particles must be distributed homogeneously in the dry lacquer film. The flatting agents and/or texture additives may be incorporated as material in powder or paste form. Conventional flatting agent pastes generally contain, apart from the flatting agents, binders, solvents and optionally additives.
Examples of binders which may be used in flatting agent pastes include alkyd, aldehyde, acrylic, polyester resins and/or cellulose esters.
EP-A-700 408 describes a matt paste suitable for the production of textured coatings on plastics surfaces, which paste is incorporated in coating compounds based on hydroxy-functional binders and polyisocyanate crosslinking agents. The matt paste contains hydroxy-functional polyesters, hydroxy-functional polyacrylates and optionally cellulose esters as binder. Texturing agents are added in powder form to the coating compound.
Often, with the above-mentioned binders which may be used in flatting agent pastes, the surfaces obtained after application of the lacquer are still too glossy, i.e. the flatting effect is still insufficient.
If the coating compounds which are to result in matt/textured surfaces are prepared by means of a mixed lacquer system of the kind used directly in situ on the user's premises, for example, in vehicle refinishing usually to provide a plurality of different hues, such a mixed lacquer system generally contains so-called additional mixed lacquers as well as the coloured mixed lacquers, for example, those for obtaining desired textures or degrees of gloss. The components of such a mixed lacquer system may be present as finished lacquers or semi-finished products.
For ecological reasons, low-emission, high-solids lacquers are also increasingly being used in mixed lacquer systems. Adequate flowability is a prerequisite for problem-free handling and good meterability of the mixed lacquers. It is difficult to achieve good flowability with the above-mentioned additional mixed lacquers containing flatting agents and/or texture additives and in high-solids lacquers because in order to obtain predetermined texture effects or degrees of gloss and due to the high solids content required of the lacquers to be processed, the additional mixed lacquers must contain such large proportions of texturing and/or flatting agents that the products are pasty and no longer free-flowing, making acceptable processing impossible. This disadvantage is not solved by the matt pastes described in EP-A-700 408 either.
Moreover, the preparations containing flatting and/or texturing agents generally have the problem that partially dried particles of said preparations or of the coating agents containing them fall from the edge of the can of the lacquer container in question back into the lacquer and may thus lead to pinholing. It is not possible to screen these particles from the lacquer prior to application since the texturing agent would then be removed too. Lacquers containing flatting agents often do not result in a uniform spray pattern. Unsightly patches form, particularly on fairly large surfaces to be lacquered.
The object of the invention was, therefore, to provide flatting agent and/or texturing agent preparations, more particularly for low-emission, high-solids coating agents in paste form which, whilst giving a very good flatting effect and texture, have good flowability and guarantee problem-free meterability. The preparations in paste form should be easy to process. Partially dried particles of said preparations or of the coating agents containing them should be substantially crumb-free and should remain adhering to the can edge of the lacquer containers in question in order to prevent pinholing and consequent lacquer defects. Moreover, the preparations in paste form should be stable in storage and exhibit no settling even after prolonged storage. The lacquers containing the pastes should result in a uniform spray pattern, particularly on relatively large surfaces.
The object is achieved by preparations of flatting agents and/or texture additives in paste form, hereinafter known as flatting agent pastes, containing
A) 5 to 30 wt. %, preferably 7 to 25 wt. % of one or more thixotropic (meth)acrylic copolymers and/or of one or more thixotropic polyesters,
B) 15 to 45 wt. %, preferably 20 to 35 wt. % of one or more flatting and/or texturing agents,
C) 30 to 65 wt. %, preferably 35 to 55 wt. % of one or more organic solvents and optionally wetting and dispersing agents, rheology modifiers, catalysts and optionally further additives and auxiliaries, wherein the proportions of components A), B) and C) add up to 100 wt. % and the weight ratio of thixotropic (meth)acrylic copolymer and/or thixotropic polyester: flatting and/or texturing agents is 1:6 to 1:0.8.
Surprisingly, it was found that the object according to the invention may be achieved by using thixotropic (meth)acrylic copolymers and/or thixotropic polyesters in the flatting agent paste. It could not have been expected that the thixotropic resins used which, in their form of application, are generally present as compact substances, may be filled with the required amounts of flatting and/or texturing agents and result in free-flowing pastes.
Thixotropic (meth)acrylic copolymers and/or thixotropic polyesters (component A) are contained as binders in the flatting agent paste according to the invention. The term thixotropic resins means, for example, resins modified by adding thixotropic agents which exhibit a decrease in viscosity under shear stress and after the shear stress regain their original viscosity in the resting state, albeit with a time lag. The thixotropic behaviour of the resins may be achieved by various methods, which will be discussed in more detail below.
The thixotropic resins to be used according to the invention are those based on (meth)acrylic copolymers and/or polyesters, preferably those based on hydroxy-functional (meth)acrylic copolymers and/or hydroxy-functional polyesters.
(Meth)acrylic copolymers which may be used in component A preferably have a hydroxyl value from 25 to 200, particularly preferably from 40 to 150 and an acid value from 0 to 50. The (meth)acrylic copolymers have a number-average molecular weight (Mn) from 1500 to 30,000 g/mole, preferably from 2000 to 15,000 g/mole.
The preparation of the (meth)acrylic resins may be carried out by polymerisation according to conventional methods, e.g., bulk, solution or suspension polymerisation. The various polymerisation processes are known to the skilled person. The solution polymerisation process is preferred for the preparation of (meth)acrylic resins. The solvent is generally charged to the reaction vessel, heated to boiling point and the monomer/initiator mixture fed in continuously over a certain period. Polymerisation may be carried out preferably at temperatures from 100° C. to 160° C.
Suitable initiators are per- and azo compounds. An amount from 0.2 to 8 wt. % of initiators, based on the initial weight of monomers, is used in preference.
Berschel Günter
Hellmann Udo
Stephan Werner
Stricker Wolfgang
E. I. du Pont de Nemours and Company
Lerman Bart E.
Reddick Judy M.
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