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
1999-03-19
2003-07-01
Egwim, Kelechi (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...
C524S501000, C524S523000, C525S124000, C525S125000, C525S194000, C525S220000, C525S221000, C525S223000
Reexamination Certificate
active
06586521
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to aqueous copolymer dispersions, which can be cured by various crosslinking resins, to a method of producing these dispersions and to their use in binders.
2. Description of the Prior Art
It is known from a various publications that dispersions based on copolymers can be used in water-thinnable lacquers and coating compositions. For example, EP-A-225,612 and DE-A-3,543,361 describe physically drying polymer dispersions which are produced by a two-stage polymerization process, wherein monomers containing carboxyl groups are used in only one of the two polymerization stages.
So that coatings produced from these dispersions exhibit good resistance to water, ammonia is used in the production thereof. Additions of other neutralizing agents impair the water resistance of coatings and films prepared therefrom. Monomers containing hydroxyl groups are not used, since they can have an unfavorable effect on the resistance to water.
Methods of producing multi-layer coatings are described, e.g., in EP-A-363,723, DE-A-4,009,858, DE-A-4,009,931, EP-A-521,919, DE-A-4,009,932 and EP-A-365,775. A base coat is first applied from which a polymer film is formed. A top coat is then applied and the base coat is then applied and the base coat and top coat are subsequently stoved together. Copolymer dispersions which are produced by a two-stage production process, optionally in combination with aminoplast resins, may be used for the base coat or top coat. Higher coating thicknesses and good visual properties of the films can be obtained by the use of these special copolymer dispersions. A disadvantage of all these dispersions, however, is the high proportion of carboxyl-functional monomers in the hydrophilic copolymer constituent.
JP-A-80/82 166 describes polyacrylate dispersions which are produced by a two-stage process. Starting materials containing carboxyl groups are used in both stages of their production. This results in dispersions with relatively low solids contents. The resulting coatings exhibit a reduced resistance to water.
U.S. Pat. No. 4,151,143 describes polyacrylate dispersions which are produced by a two-stage process, wherein the first stage is produced in organic solution, is subsequently dispersed, and an emulsion polymerization is effected as the second stage in the presence of the first stage. The resulting products have high molecular weights, but exhibit unsatisfactory film formation when used in coating compositions, and overall exhibit properties which differ from those of customary secondary dispersions.
EP-A-557,844 describes aqueous two-component polyurethane coatings which are stabilized by the addition of external emulsifiers and which are based on hydrophilic polyisocyanates and emulsion copolymers which are practically free from carboxylate groups. Due to the high molecular weights of the polymers and the permanent hydrophilic properties of the emulsifiers added, these coating compositions are still deficient with regard to their resistance to water, pigment wetting and film appearance for some applications.
EP-A-358,975 describes aqueous two-component polyurethane compositions which exhibit good properties. For some applications, however, an improvement in their solids content, resistance to water, processing time or reliability of application is needed.
DE-A 4,439,669, DE-A 4,322,242 and JP-A 04001254 describe aqueous two-component polyurethane compositions which are based on copolymers containing special monomers and can be produced by a two-stage process. These special monomers are claimed to impart improved properties to coatings produced therefrom, but result in products which are considerably more costly so that the possibilities of using them economically are limited.
From the multitude of patent applications in the field of polymer dispersions, it is apparent that there is a continuing need for improved products in order to satisfy the increasing demands being made on lacquers or coatings. In particular, dispersions are required which are capable, due to reactive groups, of being cured by suitable crosslinking agents at low temperatures, preferably at room temperature, to form high-quality coatings.
Dispersions which are advantageous from an economic and application technology point of view are those which have a high solids content and excellent stability on storage, both as a dispersion and in a lacquer. A very good capacity for pigmentation, for example, is necessary for systems such as these, and this has a considerable effect on the excellent film appearance which is required. The lacquer films must exhibit very good resistance to solvents, water and environmental effects.
It is an object of the present invention to provide aqueous dispersions that can be used in as many application areas as possible and that exhibit good compatibility with as many commercially available crosslinking agents as possible. It is an additional object to provide a simple and economical production method for the dispersions, i.e., a production method which does not involve a costly, time-consuming distillation stage and which does not involve the use of further components that have to be produced separately. It is another object of the present invention to provide dispersions that have solvent contents of less than 12% and can obtain the desired properties when prepared from raw materials which are readily available and which are as inexpensive as possible.
Surprisingly, these objects may be achieved with the specially selected copolymers of the present invention and the process for their production which are described hereinafter.
SUMMARY OF THE INVENTION
The present invention relates to aqueous solutions or dispersions of copolymers A) containing
I) a hydroxy-functional, hydrophobic copolymer containing
Ia) 30 to 85% by weight of (meth)acrylic acid esters having C
1
to C
18
hydrocarbon radicals in the alcohol portion, aromatic vinyl compounds and/or vinyl esters and
Ib) 5 to 45% by weight of hydroxy-functional monomers,
II) a hydroxy- and carboxy-functional, hydrophilic-hydrophobic copolymer containing
IIa) 4 to 20% by weight of (meth)acrylic acid esters having C
1
to C
18
hydrocarbon radicals in the alcohol portion, aromatic vinyl compounds and/or vinyl esters,
IIb) 4 to 15% by weight of hydroxy-functional monomers and
IIc) 0.8 to 3.0% by weight of acid-functional monomers, and
III) optionally a hydroxy-functional hydrophobic copolymer containing
IIIa) 0 to 16% by weight of hydroxy- and/or non-functional (meth)acrylic acid esters or aromatic vinyl compounds,
wherein
i) the preceding percentages are based on the total weight of components I), II) and III,
ii) the sum of Ia), Ib), IIa), IIb) IIc) and IIIa) is 100%, based on the weight of these components,
iii) copolymer A) has an acid number, based on solids, of 10 to 28 mg KOH/g substance,
iv) the weight percent of monomers IIc) in monomer II) is less than 25% by weight and
v) the weight percent of hydroxy-functional monomers IIb) in copolymer II) is higher than the weight percent of hydroxy-functional monomers Ib) in copolymer I).
The present invention also relates to a method of preparing aqueous dispersions or solutions of copolymers A) by
a) free radically copolymerizing in a 70 to 95% organic solution a mixture of 30 to 85% by weight of monomers Ia) and 5 to 45% by weight of monomers Ib) to form a hydrophobic, hydroxy-functional copolymer I) which is essentially free from carboxyl groups,
b) subsequently free radically copolymerizing 4 to 20% by weight of monomers IIa), 4 to 15% by weight of monomers IIb) and 0.8 to 3.0% by weight of monomers IIc) to form a hydrophilic-hydrophobic, hydroxy- and carboxy-functional copolymer II)
c) optionally subsequently free radically copolymerizing 0 to 16% by weight of monomers IIIa) to form a hydroxy-functional, hydrophobic copolymer III),
d) neutralizing 70 to 130% of the carboxyl groups and
e) dissolving or dispersing the copolymer A) in water,
wherein the percentages of the monomers are select
Blum Harald
Hovestadt Wieland
Noble Karl Ludwig
Bayer Aktiengesellschaft
Egwim Kelechi
Gil Joseph C.
Roy Thomas W.
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