Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-09-11
2004-02-10
Sergent, Rabon (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S125000, C525S129000, C525S131000, C528S070000
Reexamination Certificate
active
06689839
ABSTRACT:
INDUSTRIAL FIELD OF APPLICATION
This invention concerns novel thermoset paint compositions. More precisely, the invention concerns thermoset paint compositions which are useful as top coat paints for automobile purposes which have excellent acid resistance, abrasion resistance, adhesion, staining resistance and water repelling properties.
PRIOR ART
In past years, the problem of paint film durability, especially rain spotting due to acid rain and abrasion due to rotating car-wash brushes and the sand and dust which is thrown up while driving, has arisen. Various means of providing improvements in respect of this problem have been suggested. For example, top coat paints which have excellent abrasion resistance and which contain alkoxymonomeric melamine resin, acrylic resin which has an open ring lactone chain, and fluorine containing resin, have been disclosed in Japanese Patent Kokai H3-288577. However, although a paint film which has excellent abrasion resistance is obtained with this technology, the bonds which are formed by the reaction of the alkoxy groups of the melamine resin and the polyol hydroxy groups are readily hydrolyzed by acids and so it is difficult to achieve good acid resisting performance. Furthermore, it is known that the alkoxy groups in a melamine resin form crosslinks quantitatively with hydroxy groups, and the effective crosslink density is dominated by the hydroxy group content. Consequently, in those cases where there are mol equivalents of hydroxy group and melamine resin alkoxy group, or where the alkoxy group is in excess, attachment to the base coat of a two-coat one-bake painting type paint film is poor and, moreover, recoat adhesion failure of a recoat painting paint film which has been obtained by means of the same painting process on a two-coat one-bake painting paint film can occur.
Paint compositions which have excellent abrasion resistance which include a fluorine containing copolymer, comprising hydroxy group containing long chain vinyl ether represented by the formula CH
2
═CHO(CH
2
)
n
OH (where n is 7 to 18) and fluoro-olefin, and a hardener which has functional groups which react with hydroxy groups, have been proposed in Japanese Patent Kokai H5-105840. Furthermore, catalyst free paint compositions which include copolymers obtained by reacting fluorine containing copolymers and polybasic acid anhydrides, and alkyl etherified melamine resin and isocyanate compound or blocked isocyanate compound, have been disclosed in Japanese Patent Kokai 61-200145.
However, although the abrasion resistance is certainly improved with the former technique, the acid resistance is unsatisfactory. Furthermore, although a paint film which has excellent acid resistance is obtained with the latter technique, the abrasion resistance is unsatisfactory. Moreover, although paint films which have excellent weather resistance and resistance to chemical attack are certainly obtained with these techniques because of the use of a fluorine resin, the glass transition temperature of the paint films obtained is not controlled and so, in those cases where the glass transition temperature is low, the molecular structure of the paint film is liable to be dominated by the external environment, the movement of atoms or molecules is facilitated, and this causes orientation of polar groups or non-polar groups at the paint film surface. Consequently, the water repelling properties and staining resistance which are the distinguishing features of a fluorine resin are not realized satisfactorily, and with such external physical and chemical changes it is difficult to maintain satisfactorily the features of the fluorine resin.
Problems to be Resolved by the Invention
The aim of this present invention is to provide thermoset paint compositions which resolve the problems of the conventional fluorine resin based paint films such as those described above, which can form paint films which have excellent acid resistance and abrasion resistance, and which also have excellent adhesion properties, staining resistance and water repelling properties.
Means of Resolving These Problems
As a result of thorough research carried out with a view to achieving the abovementioned aim, the inventors have discovered that the abovementioned aim can be achieved by means of blocked isocyanate compound, alkyl etherified melamine resin, (co)polymer which has terminal hydroxy groups at a position removed from the main chain and of which the solubility parameter and the hydroxy group value are within specified ranges, and fluorine containing copolymer of which the solubility parameter and the hydroxy group value are within specified ranges, and by providing material such that the glass transition temperature of the paint film after hardening is at least 50° C., and the invention is based upon this discovery.
That is to say, the present invention is a thermoset paint composition as indicated below.
(1) Thermoset paint composition, characterized in that it contains:
(a) from 20 to 80% by weight of fluorine containing copolymer, being a copolymer of fluoro-olefin, hydroxy group containing vinyl based monomer and other vinyl based monomer, of which the solubility parameter is from 9.0 to 10.5 and the hydroxy group value is within the range from 60 to 150 mgKOH/g.
(b) from 20-80% by weight of vinyl based (co)polymer, being a (co)polymer comprising vinyl based monomer which contains at least 10% by weight of monomer which can be represented by the general formula [1] indicated below, of which the solubility parameter is from 9.0 to 10.5 and the hydroxy group value is within the range from 60 to 150 mgKOH/g,
(c) from 5 to 40% by weight of alkyl etherified melamine resin, and
(d) from 2 to 40% by weight of blocked polyisocyanate compound, and in that the glass transition temperature of the paint film after hardening is at least 50° C. General Formula [1]
(R
1
to R
5
each independently represent H or methyl group, i is 0-2, j is 0 or 1. k is 0-3, m is 0-3 and n is 0-10.)
(2) Thermoset paint composition, according to (1) above, wherein the fluorine containing copolymer (a) contains at least 10% by weight of hydroxy group containing vinyl based monomer which has at least four elements between the vinyl group and the hydroxy group, and in which the hydroxy group is located terminally.
A hardened paint film obtained by means of the thermoset paint compositions of this invention has a high glass transition temperature and, since a fluorine containing copolymer (a) is used as a main resin and a combination in which blocked polyisocyanate compound (d) which can form urethane bonds which have excellent resistance to chemical attack is used conjointly as well as the alkyl etherified melamine resin (c) for the hardener, the permeability of the paint film to hydrophilic substances such as acid rain is low, and it has a stable paint film structure which is not liable to bonding failure with acidic materials. Because of its excellent acid resistance and staining resistance, its water repelling properties can be retained over a longer time than with the conventional fluorine based paint films. Moreover, the crosslink structure which the soft segments which have hydroxy groups at the ends of flexible atomic groups which are located remote from the main chain of the vinyl based (co)polymer (b) can form, and the cohesive force of the urethane bonds which the blocked polyisocyanate compound (d) can form, impart elasticity such that the paint film recovers properly and is not deformed and/or ruptured by a load resulting from rubbing the paint film, and paint films which have excellent abrasion resistance can be formed. Moreover, the paint compositions of this invention also have excellent flex resistance and adhesion on recoating.
Tetrafluoroethylene, chlorotrifluoroethylene, 1,1-difluoroethylene, hexafluoropropylene, vinyl fluoride, vinylidene fluoride and derivatives such as carboxylic acid containing fluoro-olefins, for example, can be used as the fluoro-olefin copolymer component of the fluorine containing
Hayakawa Takehi
Monma Yasuhiro
Shibato Kishio
BASF Coatings AG
Sergent Rabon
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