US2385125A

US2385125A - Nitrocellulose lacquer compositions

Info

Publication number: US2385125A
Application number: US470907A
Authority: US
Inventors: Gerald R Barrett
Original assignee: Monsanto Chemicals Ltd
Current assignee: Monsanto Chemicals Ltd; Monsanto Chemical Co
Priority date: 1942-12-31
Filing date: 1942-12-31
Publication date: 1945-09-18
Anticipated expiration: 1962-09-18

Description

, Patented Sept. 18, 1945 mrnocsLLULosn LACQUER comosrrioss Gerald R. Barrett, Winchester, Mass, assignor to Monsanto Chemical Company, St. Louis, Mo., a

corporation of Delaware Application December 31, 1942,

Serial No. 470,901 9 Claims. (01.106481) aration oi nitrocellulose lacquer compositions having a markedly decreased tendency to gel.

It is well known that nitrocellulose lacquers containing as pigments certain metal constitue v ents, such as, bronze, aluminum-bronze, goldbronze or other copper-containing powders or pastes, are subject to rapid gelation or livering Moreover, these lacquers tend to become gelled or gelatinized in the presence oi. lead powders or pastes, andveven in the" absence of metal powders, when they are packaged in lead-lined or lead containers, such as collapsible tubes or lead toll.

It is accordingly a primary object of the present invention to provide inhibiting agents, which when added to nitrocellulose lacquers in small quantities will markedly reduce or completely prevent any tendency toward gel formation.

A further object the invention is to provide an, inhibiting agent or the type described which is more effective than most, if not all previously known inhibiting agents.

Still further objects and advantages oi the invention will appear from the tollowing description and appended claims. Before explainingin detail the present invention, however, it is to be understood that the invention is not limited in its application to the details described herein, since ,the invention is capable of other embodiments and of being practiced or carried out in various ways;

The invention is carried out in general by incorporating in the usual lacquer formulations; either containing bronze or other similar powders or intended to be" packaged in lead lined or like containers, small amounts of a certain polycarboxylic organic acid. Although malic, citric, tartaric and other polycarboxylic organic acids have been used previously for this purpose, these acids are not as efl'ective as the particular acid which is the subject of this invention.

According to this invention the most suitable polyca'rboxylic organic acid for obtaining maximum prevention or reduction in gelation is melonic acid. This acid is so effective that it ma sometimes be used in amounts as small as 0.01% by weight based onthe weight of the clear or pigmented lacquer being treated. In general, however, it is preferable to employ amounts of the acid varying from 0.05 to 1% based on the lacquer solution, either pigmented or otherwise. In some cases, it is desirable to use amounts oi acid as large as 5%. but in most instances concentrations as large as this are to be avoided, as these larger amounts have a tendency to crystallize from the lacquer film and they also decrease the water'resistance oi the film.

In general the presence of copper or lead is the chief cause of gelation in nitrocellulose lacquers, that is bronzes or other metal powders high in copper or lead are most apt to cause gelation. For this reason, relatively large amounts of the malonic acid are usually required in the case of lacquers containing powders or pigments which are high in copper or lead. Only relativelysmall amounts of the malonic acid are required, on the other hand, in the case of clear lacquers which are subjected to the undesired action of metals merely by being packaged in metal containers, due to the considerably smaller surface area to which the lacquer. is exposed in such instances.

A further understanding of the invention will be obtained from the following examples,

Bramble I A clear lacquer base 01' the following 0 mp0- sition was first prepared:

Percent by weight Cellulose nitrate (/2 second viscosity) 25 Butyl acetate 31 Toluene L.-- 30,6 Denatured alcohol 13 Malonic acid; 0.4

Twelve parts of gold bronze. were added to parts of the above clear lacquer. Upon packag ing samples of the clear lacquer and the bronzecontainlng lacquer, as well as samples of the above clear lacquer with the malonic acid omitted, in lead containers, it was found that the lacquers containing the malonic acid, either with or without addition 01' the gold bronze, were more resistant to gelation than similar lacquers which i were free oi malonic acid.

' Example II Aclear lacquer base of theri'ollowing composition was first prepared:

Per cent by weight Celluloid scraps Acetone 36 Petroleumlacquer diluent 14 Denatured. alcohol.- 35

sition resisted gelation for two months, while gelation set in alter only three days when an equal quantity of malic acid was employed. In the absence of the lead paste, but with the compositlon ltored in a lead lined container the above amount of malonic acid appeared adequate to prevent gelation indefinitely,

Example II! To 100 parts of a clear lacquer base having the following composition:

Per cent by weight were added 5 parts of copper lining powder. In the absence of inhibitor the above lacquer composition gelled in a few hours. Upon adding 0.1 part of malonic acid to an equal amount of the above powder-containing lacquer, the composition remained fluid after three months, while the addition of 0.1 part of malic acid to an equal amount of powder-containing lacquer only delayed gelation for three days.

Similar tests on a lacquer composition similar to the above but with lead paste substituted for the copper lining powder also indicated that malonic acid is superior to malic acid as an effective inhibitor of gelation.

Emmple IV To a clear lacquer base having the following composition:

Per cent by weight Nitrocellulose (15 seconds viscosity) 8 Ethyl acetate l Butyl acetate 20 Butyl alcohol 10 Ethyl alcohol 10 Toluene 34 Ester g Dibutyl phthalate 3 were added 13 parts of fine copper bronze. In the absence of inhibitor the resulting composition gelled in a few hours. Upon adding 0.4% of malonic acid (based on the clear lacquer) to the composition, it remained fluid after aging it for a month, while a similar test with malic acid substituted for the malonic acid showed partial gelation at the end of one month.

Although the examples refer solely to the treatment and testing of clear lacquers and lacquers containing various metal powders or pastes, the methods of this invention are also applicable to lacquers containing other forms of pigment, whether packaged in lead or lead-lined containers or otherwise. In general, the most difficult problems of gelation occur with lacquers containing copper-containing or lead-containing powders or pastes of the type referred to in the examples, but the advantages of the invention are also applicable to other types of lacquers, particularly when they are packaged in lead or lead-lined containers.

Where reference is made herein and in the appended claims to bronze powder, it is to be understood that this includes metal powder or flake of such materials as brass, aluminum, lead or copper, and the usual copper-tin or copper-zinc alloys. In some instances, reference is made to metal pastes. These are merely mixtures of metal, i. e. bronze powder with suitable organic solvents, and in some instances, with a polishing or leaflng agent, such as stearic acid.

Although the reason for the beneficial action of malonic acid upon lacquers of the type described is not definitely known, it is believed the malonic acid functions as a preventive of gelation by causing the formation of a thin protective film of insoluble metal malonate on the surface of the metal in contact with the lacquer. This film stifies further corrosion and prevents the building up of a concentration of dissolved metal ions capable of reacting with the nitrocellulose to form the material causing gelation. For example, dissolved lead salts, such as lead naphthenate, react instantly with a nitrocellulose solution to form a gel. Copper salts, on the other hand, do not so react, but instead require the presence of metal powder to cause gelation. Whatever the cause of gelation, however, it is believed the malonic acid functions by virtue of its ability to form a metal malonate which is insoluble in the lacquer solution.

What I claim is: g

A substantially non-gelling nitrocellulose lacquer containing from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in the absence of said acid.

2. A substantially non-gelling nitrocellulose lacquer containing from 0.05 to 1% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in'the absence of said acid.

3. A substantially non-gelling nitrocellulose lacquer containing nitrocellulose, a solvent mixture, metal powder, and from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in the absence of said acid.

4. A substantially non-gelling nitrocellulose lacquer containing nitrocellulose, a solvent mixture, metal paste, and from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in the absence of said acid. Y

5. A substantially non-gelling nitrocellulose lacquer containing nitrocellulose, a solvent mixture, a. bronze powder, and from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in the absence of said acid. a

6. A substantially non-gelling nitrocellulose lacquer containing nitrocellulose, a solvent mixture, lead paste, and from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer prior to the addition of said acid, said lacquer having a tendency to gel in the absence of said acid.

'7. The method of preventing orreducing gelation in a nitrocellulose lacquer containing a metal powder of the type tending to cause gelation which comprises addingto said lacquer from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer.

8. The method of preventing or reducing gelation in a nitrocellulose lacquer containing a metal paste of the type tending to cause gelation which comprises adding to said lacquer from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer.

9. The method of preventing or reducing gelation in a nitrocellulose lacquer which is packaged in a lead or lead-lined container which comprises adding to said lacquer from 0.01 to 5% by weight of malonic acid based on the total weight of the lacquer.

GERALD R. BARRETT.