Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1994-08-10
1997-02-25
Bleutge, John C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525482, 525523, 525533, 525934, 428413, 428418, C08F28300, C08G 828, C08L 6100
Patent
active
056059850
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to powder coatings, in particular for internal coating of packaging containers, based on epoxy resins and phenolic hardeners.
The present invention moreover relates to a process for internal coating of packaging containers, and to the use of the powder coatings.
Packaging containers, such as, for example, preserve cans, two- and three-component drinks cans and the like, are provided with a coating on the inside, on the one hand to protect the contents from deterioration due to constituents of the sheet metal being dissolved out, and on the other hand to avoid corrosion of the sheet metal by aggressive contents.
In practice, packaging containers are coated in this way mainly by means of organically dissolved coatings. However, this results in an increased pollution of the environment by solvents during drying of the coating films. Attempts are therefore increasingly being made to replace these coatings by low-solvent or solvent-free coatings. Thus, for example, thermoplastic powder coatings are often already used for covering can weld seams. These products are produced from the corresponding thermoplastics by expensive cold grinding.
Thermosetting powder coatings for covering the weld seams of metal containers employed for holding foodstuffs or drinks are known from EP-B-119164. These thermosetting powder coatings comprise, as a binder, a mixture of an aromatic epoxy resin having on average not more than 2 epoxide groups per molecule and an aromatic epoxy resin having on average more than 2 epoxide groups per molecule. The condensation product of the diglycidyl ether of bisphenol A with bisphenol A, having an equivalent weight, based on phenolic hydroxyl groups, of 220 to 280 or an acid polyester or a mixture thereof is employed as the hardener.
These powder coatings are employed only for covering the weld seams of packaging containers. EP-B-119164 contains neither indications of also employing these powder coatings for internal coating of packaging containers, nor indications of how these powder coatings are to be modified for use as internal protective coatings. In particular, EP-B-119 164 contains no information on particle sizes and particle size distributions of the powder coatings. However, the use of these powder coatings of EP-B-119 164 with a particle size distribution customary for powder coatings leads to coatings which have too high a porosity at the low coating thicknesses of .ltoreq.15 .mu.m customary for internal coating finishes.
Thermosetting solvent-containing and solvent-free coating agents for coating car bodies, machinery, plant and containers, comprising an epoxy resin having more than one 1,2-epoxide group per molecule and a polyol having more than one phenolic OH group per molecule as well as other customary auxiliaries and additives furthermore are known from DE Patent 23 12 409.
For the production of automobile top coatings, according to DE Patent 23 12 409 a powder coating having a particle size of not more than 0.044 mm is applied in a dry-film thickness of 25 .mu.m. Neither the particle size nor the particle size distribution of the powder coating particles is reported for powder coatings which are suitable for the production of internal coatings on packaging containers. Nor does DE Patent 23 12 409 contain any indication that the particle size and particle size distribution are to be adjusted specifically according to the intended use of the powder coatings. However, powder coatings having a maximum particle size of 44 .mu.m and a conventional particle size distribution are unsuitable for the production of internal coatings for packaging containers in the conventional low coating thickness of .ltoreq.15 .mu.m, since the resulting coatings have too high a porosity.
Powder coatings for internal coating of cans comprising an epoxy resin and a hardener furthermore are disclosed by U.S. Pat. No. 3,962,486. Catalytic hardeners, aromatic amines, epoxy-amine adducts and acid anhydrides are mentioned as typical hardeners in U.S. Pat. No. 3,962,486, while ph
REFERENCES:
patent: 3970621 (1976-07-01), Kondo et al.
patent: 4169187 (1979-09-01), Glazar
patent: 4183974 (1980-01-01), Coucher et al.
patent: 4251426 (1981-02-01), McClure et al.
patent: 4734468 (1988-03-01), Marx
patent: 5049596 (1991-09-01), Fujimoto et al.
patent: 5319001 (1994-06-01), Morgan et al.
Encyclopedia of Science and Technology, vol. 6, 1986, pp. 350-351.
Holderegger, "Epoxy Resin Powder Coating Composition", Apr. 9, 1987, pp. 1-43.
Lessmeister Peter
Rademacher Josef
Reiter Udo
BASF Lacke & Farben AG
Bleutge John C.
Gulakowski Randy
LandOfFree
Powder coating and its use for internal coating of packaging con does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Powder coating and its use for internal coating of packaging con, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Powder coating and its use for internal coating of packaging con will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1974664