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
2000-10-25
2002-05-14
Acquah, Samuel A. (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...
C528S297000, C528S300000, C528S302000, C528S307000, C528S308000, C528S361000, C525S437000, C525S444000, C525S450000, C525S934000
Reexamination Certificate
active
06388024
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to carboxyl functional polyester resins, to a process for the preparation of the resins, to polyglycidylester resins obtainable by glycidating said carboxyl functional polyester resins, to coating compositions, and in particular powder coating compositions or liquid coating compositions comprising said carboxyl functional polyester resins or said polyglycidylester resins, and to cured products obtained by using the indicated coating compositions.
BACKGROUND OF THE INVENTION
Powder coating compositions based on the solid reaction products of 2,2-bis-(4-hydroxyphenyl)propane and epichlorohydrin are known already for a long time. The cured products prepared on the basis of these compositions are resistant against hydrolysis, however, they show a low ultraviolet resistance and are therefore not suitable for applications requiring a high degree of outdoor durability such as building parts or automotive topcoats.
Triglycidylesters which can be used in good quality outdoor durable coatings and in moulding compositions are disclosed in European Patent Application No. 447360A (EP-A-447,360). Due to the anhydride half ester nature of the terminal carboxyl functions present in the tricarboxylic acid adduct precursors, strong alkaline conditions should be avoided during glycidation of these tricarboxylic acid adducts to avoid hydrolysis of the glycidylester formed and/or hydrolysis of one or more ester groups in the resin backbone. As a result thereof the triglycidylester produced will contain a relatively high level of hydrolizable chlorine and/or will contain low molecular weight hydrolysis products which might cause toxicity problems, as may be derived from “Water based coatings with excellent saponification stability XIIIth Int. Conf. 1987, Athens, Greece, p. 175.
The high level of hydrolizable chlorine is reflected in example 2 of EP-A-447,360 which relates to the glycidation of the 2:1 adduct of hexahydrophthalic anhydride and dimethylolpropionic acid. The product obtained has a chlorine content of 1.5%. Such a high level of residual chlorine is generally undesirable in coating compositions. In addition, due to the fact that the triglycidylesters reported in EP-A-447,360 are liquid, they can not be applied in powder coating compositions.
In e.g. International Application WO 96/11238, it was taught to a person skilled in the art of this specific area of curable coatings, that epoxy resins containing cycloaliphatic nuclei had the disadvantage that they could only provide brittle coating films when cured. This brittleness made them unsuitable for coating applications, as brittleness often led to poor adhesion.
From European patent application No. 0634434A2 was known a process for the preparation of linear tertiary aliphatic carboxyl functional polyester resins, by reacting:
(a) at least one compound A′ comprising one mono-functional primary- or secondary hydroxyl group and/or at least one compound A″ comprising one primary- or secondary hydroxyl group and one tertiary aliphatic carboxyl group;
(b) at least one aromatic or cycloaliphatic dicarboxylic acid compound B comprising two aromatic- or secondary aliphatic carboxyl groups or the anhydride thereof;
(c) at least one diol compound C comprising two aliphatic hydroxyl groups, which may independently be a primary or a secondary hydroxyl group; and
(d) at least one dihydroxymonocarboxylic acid compound D comprising a tertiary aliphatic carboxyl group and two aliphatic hydroxyl groups, which may each independently be primary or secondary hydroxyl, the molar ratio of compounds A′:A″:B:C:D being
M:N:X+Y+1:X:Y
wherein M+N=2, X ranges from 2 to 8 and Y ranges from 2-N to 8, at a temperature of from 100 to 240° C., until essentially all the non-tertiary carboxyl groups as initially present in the reaction mixture have been reacted.
Moreover in this application were disclosed polyglycidylester resins obtainable by reacting said linear tertiary aliphatic carboxyl functional polyesters with an excess epihalohydrin in the presence of a suitable base and optional catalyst. Preferably, the polyesters were reacted with epichlorohydrin. Both the specified linear polyesters and the corresponding polyglycidylesters derived therefrom were used with a cross-linking agent for powder coating compositions.
From the European patent application No. 0720997A2, linear tertiary carboxyl functional polyesters and epoxy functional polyester resins were known. These polyester resins were obtainable by reaction of:
a) at least one aromatic and/or cycloaliphatic carboxylic acid compound A comprising two aromatic- and/or secondary aliphatic carboxyl groups or the anhydride thereof,
b) at least one hydroxyl compound B comprising two aliphatic hydroxyl groups, which groups each independently may be primary or secondary hydroxyl groups,
c) at least one hydroxyl substituted carboxylic acid compound C comprising at least one tertiary aliphatic carboxyl group and two aliphatic hydroxyl groups, which groups each independently may be primary or secondary hydroxyl groups, and
d) optionally one carboxylic acid compound D comprising one carboxyl group, the molar ratio of compounds A:B:C:D being
(X+Y−1):X:Y:Z,
wherein X ranges from 2 to 8, Y ranges from 2 to 8, and Z ranges from 0 to 2.
These polyester resins could be used together with a suitable curing agent for the production of powder coatings, or could be converted into the corresponding glycidylesters, which in combination with a suitable curing agent could be used for the production of powder coatings.
From WO 98/42768 have become known carboxyl functional polyester resins, epoxy functional polyester resins derived from them, and coating compositions comprising these polyester compounds.
The carboxyl functional polyester resins are obtainable by reaction of:
a) at least a compound of the formula:
wherein x≧1
wherein R
1
and R
2
each may represent an alkyl group having from 1 to 4 carbon atoms or wherein R
1
and R
2
may form together with the group ~CH—(CH
2
)
x
—CH~ a cycloalkyl group and preferably 1,4-cyclohexane dicarboxylic acid (A
1
), optionally mixed with minor amounts of a corresponding compound of formula I, wherein x=0 or anhydride thereof (A
2
),
b) at least one diol compound B comprising two aliphatic hydroxyl groups which may each independently be a primary or a secondary hydroxyl group;
c) optionally a dihydroxymonocarboxylic acid compound C, comprising a tertiary aliphatic carboxyl group and two aliphatic hydroxyl groups, which may each independently be primary or secondary hydroxyl; and
d) optionally a trihydroxyalkane (D
1
) or tetrahydroxyalkane (D2), the molar ratio of compounds (A
1
+A
2
):B:C:D1:D2 being X+Y+2Z+3Q+P:X:Y:Z:Q, wherein X ranges from 1 to 8, Y ranges from 0 to 8, Z ranges from 0 to 4 and Q ranges from 0 to 3 and wherein p ranges from 1 to 5, and preferably 1-3 and is most preferably equal to 1, at a temperature of from 100 to 240° C., and preferably from 180 to 210° C. if any compound C is present, until essentially all the hydroxyl groups as initially present in the reaction mixture have been reacted.
Although the linear tertiary aliphatic carboxyl functional polyester resins and the polyglycidylesters thereof enabled a certain progress as to the requirements of excellent outdoor durability (UV stability) and resistance against hydrolysis in the cured state, with reference to their use in modern economically applied powder coatings, there is still a need for further improvement of this combination of properties.
On the other hand novel powder coating binders for the exterior durable powder coating market derived from carboxylated polyester resins, cured with epoxy functional acrylate polymers, have been proposed during the Waterborne, Higher Solids and Powder Coatings Symposium, Feb. 5-7, 1997, New Orleans La., USA, T Agawa and E D Dumain, p. 342-353, “New Two-component Powder Coating Binders: Polyester acrylate hybrid as TGIC Cure Alternat
Kooijmans Petrus Gerardus
Van Gaalen Ronald Petrus Clemens
Van Noort Leo Wim
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