Flow-and-leveling agents for powder coatings

Details Flow-and-leveling agents for powder coatings Flow-and-leveling agents for powder coatings

2002-02-25

2003-11-04

Pezzuto, Helen L. (Department: 1713)

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

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C526S320000, C526S328500, C526S333000

Reexamination Certificate

active

06642335

ABSTRACT:

TECHNICAL FIELD TO WHICH THE INVENTION BELONGS
The present invention relates to novel acryl silicone base flow-and-leveling agents for powder coatings which can provide the coating surfaces with a flow-and-leveling property by adding them to powder coatings in small amounts.
PRIOR ART
In general powder coatings are inferior in a flow-and-leveling property on the coating surfaces, and therefore it has tended to be difficult to use them for applications in which high appearance is required. In recent years, however, it has been tried to use powder coatings in place of solvent base coatings for the purpose of environmental pollution measures. For example, it is investigated to use them for top coating for automobiles. This has required flow-and-leveling agents for powder coatings having high functions. Acryl base polymers, modified silicone oils and organic waxes have so far been used as flow-and-leveling agents in compliance with this requirement. Powdery flow-and-leveling agents of a hybrid type making use of acryl base polymers and organic waxes are proposed in, for example, Japanese Patent Publication No. 21977/1986.
The Problems to be Solved by the Invention
However, a satisfactory flow-and-leveling property are not necessarily obtained with these conventional techniques in the fields requiring a high appearance such as uses for automobiles which are researched in recent years, and when large amounts of flow-and-leveling agents are added in order to obtain a good appearance, adverse effects are exerted on a layer-to-layer adhesion in recoating or adverse effects such as roughening of the recoated films are often observed.
Accordingly, an object of the present invention is to provide flow-and-leveling agents capable of being utilized for uses requiring a high appearance which has not been obtained with conventional flow-and-leveling agents for powder coatings.
Means for Solving the Problems
Various investigations repeated by the present inventors have resulted in finding that a flow-and-leveling property which is so good as has never been can be provided onto the coating surface by blending powder coatings with flow-and-leveling agents of (1), (2), (3) and (4) described below and that adverse effects are not exerted on the recoating property.
(1) A flow-and-leveling agent for a powder coating comprising a trimethylsilyl group-containing copolymer obtained by copolymerizing a reactive monomer (A) having a trimethylsilyl group represented by a structural formula:
—Si(CH
3
)
3
in a molecular structure and/or a reactive monomer (B) having a trimethylsilyl group in the form of a tris(trimethylsiloxy)silyl group represented by a structural formula:
—Si[OSi(CH
3
)
3
]
3
in a molecular structure with a (meth)acrylic acid ester (C) represented by a formula:
[wherein R
1
represents a hydrogen atom or methyl, and R
2
represents an alkyl group or alkenyl group having 1 to 18 carbon atoms] and/or a (meth)acrylic acid ester (D) represented by a formula:
[wherein R
3
represents a hydrogen atom or methyl; R
4
represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms; n represents an integer of 2, 3 or 4, and m represents an integer of 1 to 50], wherein the above trimethylsilyl group-containing polymer contains a trimethylsilyl group originating in the monomers (A) and/or (B) in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight and has a number average molecular weight of 1000 to 60000, preferably 2000 to 30000.
(2) A flow-and-leveling agent for a powder coating comprising a trimethylsilyl group-containing copolymer obtained by reacting a copolymer of a multifunctional monomer into which a trimethylsilyl group or a tris(trimethylsiloxy)silyl group can be introduced and the (meth)acrylic acid esters (C) and/or (D) described in the above item (1) with a trimethylsilyl group-containing compound and/or a tris(trimethylsiloxy)silyl group-containing compound, wherein the above trimethylsilyl group-containing polymer contains a trimethylsilyl group in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight and has a number average molecular weight of 1000 to 60000, preferably 2000 to 30000.
(3) A flow-and-leveling agent for a powder coating comprising a trimethylsilyl group-containing copolymer obtained by copolymerizing the monomer (A) and/or (B) described in the above item (1) and the (meth)acrylic acid esters (C) and/or (D) described in the above item (1) with a reactive monomer (E) which can be copolymerized with them, wherein the above copolymer contains a trimethylsilyl group originating in the monomers (A) and/or (B) in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight and a copolymerization unit originating in the monomer (E) in a proportion of not exceeding 50% by weight and has a number average molecular weight of 1000 to 60000, preferably 2000 to 30000.
(4) A flow-and-leveling agent for a powder coating comprising a trimethylsilyl group-containing copolymer obtained by reacting a copolymer of the multifunctional monomer described in the above item (2), the (meth)acrylic acid esters (C) and/or (D) described in the above item (1) and the reactive monomer described in the above item (3) with a trimethylsilyl group-containing compound and/or a tris(trimethylsiloxy)silyl group-containing compound, wherein the above trimethylsilyl group-containing copolymer contains a trimethylsilyl group in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight and a copolymerization unit originating in the monomer (E) in a proportion of not exceeding 50% by weight and has a number average molecular weight of 1000 to 60000, preferably 2000 to 30000.
If a proportion of a trimethylsilyl group originating in the monomers (A) and/or (B) based on the copolymer is smaller than 2% by weight, the satisfactory flow-and-leveling property is not obtained. On the other hand, if it is more than 65% by weight, adverse effects are more likely to be exerted in recoating a coating film. When both the monomers (A) and (B) are used in combination, a proportion of the respective amounts thereof is optional, and they can be used in combination so that a proportion of a trimethylsilyl group based on the copolymer is 2 to 65% by weight.
The (meth)acrylic acid esters of the formulas (C) and/or (D) are copolymerized in order to provide an effect of obtaining a good flow-and-leveling property, and the satisfactory flow-and-leveling property can not be obtained with monomers other than them. When the number (m) of alkylene glycol units contained in the (meth)acrylic acid ester (D) exceeds 50, not only the satisfactory flow-and-leveling property can not be obtained, but also there is the concern that adverse effects in terms of the physical properties are exerted on the coating film. When both the monomers (C) and (D) are used in combination, a proportion of the respective amounts thereof is optional, and they can be used in combination so that a proportion of a trimethylsilyl group originating in the monomers (A) and/or (B) based on the copolymer is 2 to 65% by weight.
The copolymer of the (meth)acrylic acid esters (C) and/or (D) with the multifunctional monomer is subjected to addition reaction or condensation reaction with a trimethylsilyl group-condaining compound and/or a tris(trimethylsiloxy)silyl group-containing compound whereby a trimethylsilyl group can be introduced into the above copolymer. The copolymer obtained by this method provides as well the effect of endowing the coating surface with a good flow-and-leveling property if the trimethylsilyl group is introduced into the copolymer in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight.
If the trimethylsilyl group is contained in the copolymer in a proportion of 2 to 65% by weight, preferably 5 to 40% by weight, an acryl silicone copolymer containing copolymerization units originating in the other reactive monomer (E) in a range in which the proportion based on the copolymer does not exceed 50% by weight provides as well the effect of endowing the coating

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