Pigment dispersions containing ABC-block polymer dispersant

Details Pigment dispersions containing ABC-block polymer dispersant Pigment dispersions containing ABC-block polymer dispersant

1999-10-07

2002-07-02

Wu, David W. (Department: 1713)

Compositions: coating or plastic

Coating or plastic compositions

Marking

C106S031860, C106S499000, C524S529000, C524S531000, C524S533000, C524S535000, C524S555000, C525S244000, C525S294000, C525S296000, C525S297000, C525S299000, C525S303000, C525S308000, C525S309000, C525S312000

Reexamination Certificate

active

06413306

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to an improved pigment dispersion containing an ABC-block polymer dispersant.
BACKGROUND OF THE INVENTION
AB block polymer dispersants are known in the art and are used to form pigment dispersions that are used in a variety of coating compositions. U.S. Pat. No. 4,656,226 issued Apr. 7, 1987, to Hutchins et al shows an AB block polymer dispersant having polar groups such as acids or amines that attach to a pigment's surface and the other block of the polymer keeps the pigments stable in the dispersion or coating composition. U.S. Pat. No. 5,221,334 issued Jun. 22, 1994, to Ma et al also shows AB or BAB block polymers that are used in aqueous printing inks to keep pigments dispersed in the inks. ABC triblock polymers have been used in aqueous ink jet inks to disperse pigments in these inks as shown in U.S. Pat. No. 5,519,085 issued May 21, 1996 to Ma et al.
These block polymers are made by known “living” free radical polymerization techniques, also referred to as group transfer polymerization (GTP). In GTP, an initiator splits with one end going to the tail of an acrylic monomer unit and the other to the head. The group at the head transfers to the head of a second monomer unit as that unit is polymerized with the first. Such techniques are described in U.S. Pat. No. 4,417,034 issued Nov. 22, 1983, and U.S. Pat. No. 4,508,880 issued Apr. 2, 1985, to O. W. Webster and U.S. Pat. No. 4,414,372 issued Nov. 8, 1983, and U.S. Pat. No. 4,524,196 issued Jun. 18, 1985 to Farnham et al. The above patents are hereby incorporated by reference.
Conventional truck and automobile finishes comprise a clear coat applied over a pigmented base coat that is applied over a primer layer. The polymer dispersant used in the base coat must not only keep the pigment dispersed in the liquid coating composition but needs to contain a reactive group that will react with the crosslinking agent used in the coating composition which on curing makes the dispersant an integral part of the resulting finish. Polymer dispersants can cause intercoat adhesion failures and usually are used only in limited amounts. It is desirable that the polymer dispersant have reactive groups that will bond with the primer layer to improve intercoat adhesion of the base coat to the primer rather than cause intercoat adhesion problems and cause flaking and chipping of the resulting finish.
SUMMARY OF THE INVENTION
A pigment dispersion useful for forming coating compositions containing dispersed pigment, a non-aqueous carrier liquid and an ABC-block polymer dispersant (binder);
the ABC block polymer has a number average molecular weight of about 5,000-20,000 and contains a polymeric A segment, a polymeric B segment and a polymeric C segment; wherein
the polymeric A segment of the block polymer is of polymerized monomers selected from the following group: alkyl (meth)acrylate monomers having 1-12 carbon atoms in the alkyl group, aryl (meth)acrylate monomers, cycloalkyl (meth)acrylate monomers or mixtures of any of the above;
the polymeric B segment of the block polymer is of polymerized alkyl amino alkyl (meth)acrylate monomers having 1-4 carbon atoms in the alkyl group quaternized with an alkylating agent; and
the polymeric C segment of the block polymer is of polymerized monomers of hydroxy alkyl (meth)acrylate having 1-4 carbon atoms in the alkyl group and monomers selected from the following group: an alkyl (meth)acrylate having 1-12 carbon atoms in the alkyl group, an aryl (meth)acrylate, or a cycloalkyl (meth)acrylate and optionally contains polymerized monomers of glycidyl (meth)acrylate or polyalkylene glycol (meth)acrylate;
wherein the weight ratio of pigment to binder in the dispersion is about 1/100-200/100.
Pigment dispersions of a CBA block polymer where the C,B and A segments are as described above also are part of this invention.
DETAILED DESCRIPTION OF THE INVENTION
The term (meth)acrylate refers to both the acrylate and methacrylate esters.
The novel pigment dispersion is stable and in general is non-flocculated or agglomerated and is compatible with a variety of polymeric film forming binders that are conventionally used in coating compositions and in particular, compatible with polymers that are used in coating compositions. The ABC block polymer dispersant upon curing of the coating composition into which it has been incorporated, reacts with other film forming components of the coating composition such as the polyisocyanate crosslinking agent and becomes part of the film and does not cause deterioration of the film upon weathering as may occur if it remained an unreacted component of the film. Also, since the ABC block polymer is an excellent dispersant, the ratio of polymer to pigment or polymer being dispersed is less than used with conventional dispersants and a large variety of pigments and polymers can be dispersed thereby enlarging the number and types of pigment dispersions that can be formulated. The ABC block polymer has reactive groups that improve adhesion to a primer layer thereby reducing flaking and chipping of the coating composition.
It has been found that improved coating compositions are obtained by using these novel pigment dispersions. These coating compositions also contain a film forming binder usually an acrylic polymer and a curing agent such as a polyisocyanate or an alkylated melamine. Such compositions have the advantage of providing excellent coating properties desirable for automotive finishes. Base coats of conventional base coat/clear coat finishes currently used on automobiles and trucks colored with pigment dispersions of this invention have significantly improved depth of color in comparison to base coats colored with conventional pigment dispersions.
The ABC block polymer used to formulate the dispersion of this invention can be prepared by anionic polymerization, atom transfer polymerization or by GTP (Group Transfer Polymerization) techniques. Preferably, the polymer is prepared using GTP techniques as described in the aforementioned GTP patents (U.S. Pat. Nos. 4,417,034, 4,508,880, 4,414,372 and 4,524,196). These polymers have a number average molecular weight of 5,000-20,000 and preferably 7,500-12,000. The A segment of the polymer comprises 20-60% (preferably 32-42%) by weight of the polymer, the B segment of the polymer comprises 20-60% (preferably 15-40%) by weight of the polymer and the C segment of the polymer comprises 20-60% (preferably 35-45%) by weight of the polymer.
All molecular weights referred herein can be determined by GPC (gel permeation chromatography) using a polymethylmethacrylate standard.
The A segment of the ABC block polymer is relatively nonpolar in comparison to the B and C segments and provides steric stabilization of the pigment dispersion. The B segment is polar and contains groups that bind to the pigment particles through polar-polar interactions. The C segment contains mostly polymerized nonpolar monomers and contains functional hydroxyl groups, amino groups and other functional groups such as glycidyl groups, amino groups, and alkylene glycol groups. These groups provide co-valent bonding with film forming components of the coating composition to which the dispersion has been added.
The ABC block polymer preferably is prepared by using GTP techniques. In an inert atmosphere such as nitrogen, solvent such as THF (tetrahydrofuran), toluene, propylene glycol methyl ether acetate, tetraglyme or mixtures of such solvents, a catalyst such as tetrabutyl ammonium m-chlorobenzoate and initiator such as 1-methoxy-1-trimethylsiloxy-2-methyl propene are charged into a polymerization vessel. Then the A segment monomers are added. Typical reaction temperatures used are room temperature to 70° C. for 45-90 minutes. When at least 95% of the monomers have been polymerized, the monomers for the B segment of the polymer are added. Typical reaction temperature is about 30-70° C. and reaction times are about 30-100 minutes or until at least 95% of the monomers have been polymerized. The monomers of segment C are

Affiliated with

Also associated with

Rating

Pigment dispersions containing ABC-block polymer dispersant does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pigment dispersions containing ABC-block polymer dispersant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pigment dispersions containing ABC-block polymer dispersant will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2906533