US2143929A - Lacquer - Google Patents

Description

Patented Jan. 17, 1939 UNITED STATES PATENT OFFICE LACQUER N 0 Drawing.

Application June 26, 1936,

Serial No. 87,329

1 Claim.

This invention relates to lacquers and is concerned particularly with lacquer for coating wood and the like. The invention contemplates a lacquer containing nitrostarch as a film forming ingredient.

Wood lacquers are applied customarily by spraying. The viscosity of the lacquer must, therefore, be comparatively low. It has been a problem in the heretofore customary art of lacquer manufacture to produce a so-called Wood lacquer having a high content of non-volatile ingredients without increasing the viscosity of the lacquer to a point at which it can not be satisfactorily applied by spraying.

In the heretofore customary art of wood lacquer manufacture, satisfactory lacquers for spray application have not contained much more than 27% of non-volatile ingredients. One spray coat of such a lacquer does not produce a film of sufiicient thickness for most commercial purposes. Consequently, it has been necessary heretofore to apply two or more spray coats of this type of lacquer to wood in order to produce a film of sufficient thickness.

The greater the number of spray coats which must be applied to wood, the greater is the cost of the finishing operation. For example, if furniture is being spray coated with a lacquer containing about 27% of nonvolatile ingredients it is necessary to provide ample storage space for the furniture so that it may be dried between coats. If two coats have to be dried, the amount of storage space for the furniture is of course greater than the storage space required if only one coat has to be dried on the furniture. The storage space provided must be relatively dust proof and well ventilated. Consequently, it is expensive to provide this type of storage space. Furthermore, an increase in the number of coats which must be applied to the furniture results in an increase in the value of the inventory of furniture in process and consequently increases capital investment.

Moreover, if two spray coats are necessary to produce a lacquer film of satisfactory thickness, the labor involved is approximately doubled. This labor includes the work of operating the spray and also the work of handling the furniture, or other Wooden objects, to and from the storage space in which the lacquer is dried.

A further disadvantage of furniture lacquers containing, say 27% or less of non-volatile ingredients is the large consumption of solvents for producing a coat of any given thickness. For purposes of illustration, a lacquer containing 10% of non-volatile matter will produce in a single application a film approximately one-half as thick as a lacquer containing 20% of non-volatile matter, but the amount of solvents lost in both cases will be approximately the same. In other words, two applications of the 10% lacquer will be required to produce a coat obtained with one application of the 20% lacquer, so the use of the 10% lacquer approximately doubles solvent consumption. Consequently, the higher the percentage of non-volatile matter and the lower the percentage of solvents in a lacquer the greater is the economy in application of the lacquer. It should be noted that, especially in the case of furniture finishing, all solvents in a lacquer are completely lost, because it is generally uneconomical to apply lacquer to furniture under such conditions that the evaporating solvent can be recovered.

From the foregoing it will be seen that any successful efforts to increase the proportion of non-volatile matter in wood lacquer suitable for spray application will inevitably result in economies in the application of the lacquer.

I appreciate that it has been proposed heretofore to use nitrostarch as an ingredient in lacquer. However, in the case of lacquers in general and wood lacquers in particular, such prior proposals have not led to successful commercial practice. This I believe has been due to the fact that the successful use of nitrostarch requires a careful control of the proportions of resins and plasticizers which accompany the nitrostarch and modify its action in the lacquer.

As a result of my investigations I have dis covered that furniture lacquers containing a very high proportion of non-volatile matter and a correspondingly low proportion of solvent or volatile matter may be obtained when nitrostarch is used as the principal base for the lacquer. However, I have also discovered that in order to employ nitrostarch in the manufacture of commercially satisfactory wood lacquers it is necessary to control the proportion of accompanying resins and plasticizers Within definite limits.

My invention will be more completely understood in the light of the following detailed description taken in conjunction with the specific formulae for lacquers of my invention, which are set forth hereinafter.

I use the term resin to describe those amorphous substances, both natural and artificial, which have inherent film forming characteristics. Examples of such resins are dammar gum, copal, ester gum and unmodified alkyd resin produced by the use of a synthetic polybasic acid of terpene origin, such as the mono ethylene glycol ester of the condensation product of terpinene-maleic anhydride (Petrex 5).

I- use the term plasticizer to describe those ingredients in lacquer which are true solvents for nitrostarch and which are added to impart flexibility to the final dried film and to overcome brittleness therein. The plasticizer remains in the lacquer film upon drying, but does not itself have film forming characteristics. Examples of such plasticizers are dibutyl phthalate, tricresyl phosphate and triacetin. As used here the term plasticizer does not include castor oil and the like which are not true solvents for nitrostarch and are classed as softeners in the art.

By non-volatile ingredients I mean nitrostarch, resin and plasticizer. These three ingredients remain fixed to the lacquered surface when the lacquer film is dried under ordinary commercial conditions, i. e., at temperatures that do not greatly exceed '7 C.

The term solvent is used here to mean a readily volatile liquid which will dissolve nitrostarch or a resin, or both, and which will evaporate from a lacquer film at room temperature leaving the non-volatile ingredients. The solvent may comprise a single liquid substance or a mixture of two or more liquid substances.

The term solvent mixture is used to include true solvents for nitrostarch or for a resin or for both, together with liquid diluents and latent solvents which by themselves will not dissolve nitrostarch or a resin, but when added to a solution of nitrostarch or of resin or of both in limited amount will dilute the solution without causing precipitation of the nitrostarch or the resin.

I have found that in order to make nitrostarch wood lacquers it is necessary to employ certain proportions of resin and plasticizer as well. Thus, in a lacquer containing nitrostarch in relatively large amount I have discovered that it is necessary to employ resin in amount ranging from 60 to 120% of the weight of the nitrostarch and a plasticizer in amount ranging from 22 to 33% of the weight of the nitrostarch. If less than 60% by weight of resin based on the nitrostarch is employed, the resulting film of lacquer will be unsatisfactory. The film will crack or check. If more than 120% by weight of the resin based on the nitrostarch is employed the resulting dried lacquer film tends to wrinkle.

If less than 22% by weight of plasticizer (based on the weight of the nitrostarch) is employed the final dried lacquer film tends to check and crack. On the other hand, if more than 33% of the plasticizer (based on the weight of the nitrostarch) is employed the final lacquer film tends to be too soft, and will print.

I have found that, in accordance with the foregoing principles, it is possible to produce a lacquer which may be sprayed and which will contain from 35 to 50% of non-volatile ingredients, i. e. 35 to 50% 0f the combined nitrostarch, resins and plasticizers.

As hereinbefore indicated nitrocellulose wood lacquers at the present time contain not greatly in excess of 27% by weight of non-volatile ingredients, providing of course that such lacquer is amenable to spray application. Consequently, the fact that I am able to include from 35 to 50% of non-volatile constituents in the wood lacquer of my invention represents a marked improvement and permits a satisfactory film of sufficient thickness to be applied to wood in a single spraying operation.-

The following examples represent specific formulae which have been compounded in accordance with the foregoing rules of formulation and which have proved to be superior to the wood lacquers of the heretofore customary art. In all the examples the non-volatile ingredients and the solvent mixture are set forth separately.

Example I Composition of non-volatile ingredient:

Per cent by weight Nitrostarch, (13.2% nitrogen) 50.7 Resin, Petrex 35.4 Plasticizer, dibutyl phthalate 13.9

Total 100 Ratio of nitrostarch content to resin content,

Ratio of nitrostarch content to plasticizer content, 100 to 27 Composition of the solvent mixture:

Per cent by weight Denatured ethyl alcohol 6 Toluol 46 Butyl acetate 16 Butyl cellosolve (mono-butyl ether of ethylene glycol) l6 Amyl acetate 16 Total- 100 Composition of the lacquer, total non-volatile ingredients and total solvent mixture:

Per cent by weight Non-volatile ingredients 36.3 Solvent mixture 63.7

Total 100 In commercial operation the lacquer ingredients are combined as follows:

The nitrostarch is received Wetted with the denatured ethyl alcohol. A proper amount of nitrostarch is then dissolved in a portion of the solvent mixture to give a solution containing Example II Composition of the non-volatile constituents in the lacquer:

Per cent by weight Nitrostarch (13.2% nitrogen) 52.7 Resin (made up of 15.8% dewaxed dammar gum, and 15.7% ester gum) 31.5 Plasticizer (made up of 9% dibutyl) phthalate and 6.8% tricresyl phosphate) 15.8

Total 100 Ratio of nitrostarch content to resin content,

Ratio of nitrostarch content to plasticizer content, 100 to 30. 7

Composition of the solvent mixture:

.Per cent by weight Denatured ethyl alcohol 6 Toluol 46 Butyl alcohol 16 Amyl acetate 16 Butyl cellosolve (mono-butyl ether of ethylene glycol) 16 Total 100 Composition of the lacquer, total non-volatile ingredients and total solvent mixture:

Per cent by weight Non-volatile ingredients 44.4 Solvent mixture 55.6

Total 100 The ingredients are combined as in Example I.

Example III Non-volatile ingredients in the lacquer:

Per cent by weight Nitrostarch (13.2% nitrogen) 40.9 Resin, copal 48.9 Plasticizer,tricresyl phosphate 10.2

Total 100 Ratio of nitrostarch content to resin content, 100 to 100-120.

Ratio of nitrostarch content to plasticizer content, 100 to 25.

Composition of the solvent mixture:

Per cent by weight Denatured ethyl alcohol 6 Toluol 46 Butyl alcohol 16 Amyl acetate 16 Butyl cellosolve (mono-butyl ether of ethylene glycol) 16 Total 100 Composition of the lacquer, total non-volatile ingredients and total solvent mixture:

Per cent by weight Non-volatile ingredient 42.2 Solvent mixture 57.8

Total 100 The procedure in making the lacquer is substantially the same as outlined in Example I.

It should be noted that copal is a resin which is not compatible with nitrocellulose. I have found, however, that copal resin may be used with nitrostarch and produces a very satisfactory lacquer.

Certain resins have proved to be most satisfactory for the manufacture of the wood lacquer of my invention. These include Petrex 5, dewaxed dammar gum, ester gum, copal, and maleic anhydride-modified ester gum.

Certain plasticizers are particularly desirable in the practice of the invention. These include dibutyl phthalate, tricresyl phosphate, the glycerol ester of acetic acid, methyl-ortho-benzoyl benzoate, and ethyl-ortho-benzoyl benzoate. All of these plasticizers have proved satisfactory in the manufacture of wood lacquer according to the foregoing rules of formulation.

Softeners, in particular castor oil, are not suitable ingredients for the wood lacquers of my invention, because they tend to produce an excessively soft film and also tend to sweat out of the dried film.

I have found that in the preparation of lacquers according to the principles hereinbefore enunciated, it is desirable that the solvent mixture employed contain at least 50% by weight of one or more liquids which have boiling points in excess of 100 C. I attribute the improved results which I have obtained in using these liquid constituents in a solvent mixture to the fact that they evaporate slowly and keep the lacquer film in a plastic condition so that all air bubbles may escape from the film during drying and allow the film to dry in an even glossy state and. reduce orange peel effects to a minimum.

The lacquer of my invention is particularly adapted to spray application and will have a viscosity of 100 centipoises or less at 25 C. even when the lacquer contains as much as 35 to 50% of non-volatile matter. Satisfactory lacquers made in accordance with my invention may be produced with a viscosity as low as 60 centipoises at 25 C. even with a non-volatile content of 44%. Commercial wood lacquers of such low-viscosity containing such a high content of non-volatile matter have not been produced heretofore.

The application of the lacquer of my invention to wood is conducted in the customary manner. The wood is prepared in the usual way and stained or filled if necessary. Thereafter the lacquer is sprayed on the prepared surface of the wood.

If lacquer which will produce a dull finish on Wood is desired, an insoluble metallic soap may be incorporated into the lacquer. In general, about 10% by weight of the soap (based on the weight of the total non-volatile ingredients in the lacquer) will be required. I have found that aluminum stearate is the most satisfactory agent for producing said dull finish, but zinc stearate may also be employed. The amount of the metallic soap to be added is largely dependent upon the degree of delustering required.

The lacquer of my invention is non-bridging. That is to say, it can be applied to intricately carved surfaces without pulling away from sharp angles or curves as the film dries. The tendency to bridge is a frequent defect of the wood lacquers of the heretofore customary art, and often has prevented their use in finishing furniture which has intricately carved or molded surfaces.

I have also noted that the nitrostarch of my invention is more resistant to the effect of actinic light and does not suffer the same degree of discoloration that occurs when nitrocellulose lacquers are exposed to sunlight.

Preferably the lacquer of my invention contains only four classes of ingredients, namely, nitrostarch, resins, plasticizers and solvent mixture, with or without a delusterin-g agent such as a metallic soap.

I claim:

A sprayable non-bridging actinic ray-resistant wood lacquer having aviscosity of less than about 100 centipoises at 25 C., and consisting of from 35 to 50% by weight of non-volatile ingredients consisting of nitrostarch, from 60 to by weight of the nitrostarch of resin and from 22