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
1997-11-25
2001-03-13
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S448000
Reexamination Certificate
active
06201073
ABSTRACT:
The present invention relates to linear, tertiary carboxyl functional polyester resins, to a process for the preparation of the resins, to polyglycidylester resins obtainable by glycidating said linear, tertiary carboxyl functional polyester resins, to coating compositions, especially powder coating compositions, comprising said linear, tertiary carboxyl functional polyester resins or said polyglycidylester resins and to cured products obtained by using the indicated coating compositions.
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 only show a low ultraviolet resistance and are therefore not suitable for applications requiring a high 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. 447360 (EP-A-447,360). Due to the secondary 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.
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.
The most commonly used system for outdoor durable powder coatings are polyester/triglycidylisocyanurate (TGIC). For health and safety reasons however the use of TGIC is viewed with suspicion. TGIC is relatively toxic (Rat Oral LD
50
of 0.4 g/kg) and there are indications that the compound is mutagenic according to the Ames Mutagenicity Test.
European patent application No. 0634434 describes a process for the preparation of linear tertiary aliphatic carboxyl functional polyester resins, by reacting:
(a) at least one compound A′ comprising one monofunctional primary- or secondary hydroxyl group and/or at least one compound A″ comprising one primaryor 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.
As preferred component (b) were described and exemplified hexahydrophthalic anhydride.
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 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.
The European patent application No. 0720997, describes a linear tertiary carboxyl functional polyester and epoxy functional polyester resins therefrom. These polyester resins were produced 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.
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.
Therefore, it is an object of the invention to provide linear, acid functional polyester resins in which the acid-functionality only comprises tertiary aliphatic carboxylic acid functionality, which can be readily glycidated so as to form a polyglycidylester resin. Such linear, tertiary carboxyl functional polyester resin and such polyglycidylester resin preferably show further improved properties when used in outdoor durable powder coating compositions, which are relatively environmentally friendly.
Accordingly, the present invention provides linear, tertiary carboxyl functional n polyester resins produced by reacting
(a) at least one 1,4-dicarboxylcyclohexane (A) optionally mixed with a minor weight fraction of an alkane dicarboxylic acid, containing in the range of from 8 to 16 carbons atoms (A′),
(b) at least one dihydroxymonocarboxylic acid compound (B), comprising a tertiary aliphatic carboxyl group and two aliphatic hydroxyl groups,
(c) optionally one diol compound (C) comprising two aliphatic hydroxyl groups, which may each independently be a primary or a secondary hydroxyl group, and
(d) optionally a compound (D′) comprising one monofunctional primary or secondary hydroxyl group and/or a compound (D″) comprising one primary or secondary hydroxyl group and one tertiary aliphatic carboxyl group, the molar ratio of the compounds (A+A′):B:C:D′:D″ being X+Y+1:Y:X:M:N wherein M+N is in the range of from 0 to 2, and preferably from 0.5 to 2, and more preferably from 1 to 2,
wherein X ranges from 2 to 8, and Y ranges from (2−(M+N)) to 8, at a temperature of from 100 to 225° C., until essentially all the non-tertiary carboxyl groups as initially present in the reaction mixture have been reacted.
The linear tertiary aliphatic carboxyl functional polyester resin thus produced is essentially free from non-tertiary carboxyl groups when it has an acid value which practically corresponds to the theoretical acid value calculated on the basis of the amount of tertiary carboxyl groups of the reactants as initially present in the reaction mixture. The term “practically” is used h
Kooijmans Petrus Gerardus
Van Gaalen Ronald Petrus Clemens
Van Noort Leo Wim
Sellers Robert E. L.
Shell Oil Company
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