USRE23753E

USRE23753E - Coated plastic products

Info

Publication number: USRE23753E
Authority: US
Priority date: 1947-02-21
Publication date: 1953-12-15
Also published as: FR961065A; BE480439A; GB676765A; US2578665A; NL73376C; CH297418A

Description

Reissuecl Dec. 15, 1953 Re,

UNITED STATES PATENT OFFICE COATED PLASTIC PRODUCTS Johan Bjorksten, Madison, Wis., Stuart 0. Fledler, Cleveland, Ohio, and Luther L. Yaeger, Madison, Wis., assignors to Nash-Kelvinator Corporation, Kenosha, Wis., a corporation of Maryland No Drawing. Original No. 2,578,665, dated December 18, 1951, Serial No. 730,192, February 21, 1947. Application for reissue December 17,

1952, Serial No. 326,615

12 Claims. (01. 260-17) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to articles made of polystyrene and more specifically to such articles, covered with a surface coating which imparts to them a greatly enhanced resistance to abrasives,

solvents and to other destructive influences; and parency. also to modes of preparing and applying such The present invention has for an object to surface coating materials for polystyrene. overcome the disadvantages just mentioned, An-

Polystyrene is a widely employed construction other object is to provide a novel coating for material. For example, it is being used in repolystyrenes which forms an integral bond therefr geration equipment and also in automotive and m with, and which imparts to polystyrene enhanced aircraft industries for structural as Well as decresistance to scratching, reduced electrostatic orative purposes. However, the utility of polysensitivity, and greatly enhanced resistance to styrene is greatly restricted by certain undesircleaning fluids. A further object is a polystyrene able properties, namely: 1. Very high electroarticle protected by such coating. A still further static charges which cause excessive attraction object is a process of applying to the polystyrene for dust. 2. High susceptibility to scratching. articles a protective coating integrally bonded (This does not bear a direct relation to the hardthereto. Further objects will become apparent as ness of the article, inasmuch as the optical effects the following detailed description proceeds. of scratching are more pronounced with poly- By integral bond We mean that the coating styrene than with certain other materials which applied to all practical purposes forms a unity actually have a lower hardness, such as, for exwith the material beneath it, so that it cannot ample, acrylates.) 3. Clouding or dissolving of I be peeled off or loosened as a layer, for example, the styrene surface by commonly used cleaning by scratching with a sharp instrument. fluids. F We have now succeeded in providing acrylate Any one of the reasons is sufficient to greatly coatings which adhere firmly to polystyrene, reduce the applicability of polystyrene as a mawithout disturbing its clarity or appearance. terial for many articles where it would. otherwise Our products and procedures are based on the be desirable by virtue of its excellent physical and discoveries: mechanical properties and its relatively low price. (a) that if the active solvent in which acrylate In the past, it has been attempted to apply to 30 resins are prepared, and furnished commercially, polystyrene various kinds of coating for added is distilled off to a large degree, it is then possible surface protection and to improve its properties. to formulate suitable coating compositions for These attempts have all been unsuccessful. Coatdepositing acrylate coatings on polystyrene withings of shellac, while soluble in solvents which do out etching the polystyrene surface: not attack the polystyrene, are not sufiiciently (b) that the etching effect of active solvents tenacious to give the protection desired. Further can be largely checked by the inclusion of cellumore, they are soluble in alcoholic cleaning fluids. lose esters: Ethyl Cellulose coatings f th po y yrenes and (c) that by careful balancing of solvent comof their derivatives have also been tried, and while positions, it is possible to provide a combination these possess a considerable resistance to many 40 solvent which dissolves and deposits acrylates, yet solvents and to electrostatic influences, they are is non-etching to styrene: not very scratch resisting, and, above all, they (d) that cellulose esters, which otherwise do fail to bond to the polystyrene. It can be said not adhere to polystyrene, can be brought to adgenerally that those coatings ofprior art which here firmly by the addition of even a minor perbond to the polystyrene so as not to become decentage of acrylates, such as from 1% to 40%. tached therefrom are soluble only in solvents In accordance with this invention, we employ which are also solvents for polystyrene, and which as the principal protective ingredient, an acrylate therefore etch and cloud it, and that coatings of or a methacrylate polymer. prior art reasonably suitable in other regards fail For t e ke of brevity, We shall hereafter in,- to adhere to polystyrene. clude the film-forming acrylate and methacry- Attempts made in the past to coat polystyrene with acrylate or methacrylate type polymers failed, because the solvents necessary to dissolve these etched the styrene so as to destroy its trans- Among the numerous types of acrylate employed for the purpose of the invention, the preferred type is:

Ethyl and methyl methacrylate co-polymer made by the E. I. du Pont de Nemours at C0.

Somewhat less favorable film characteristics were obtained with the following type of acrylate:

Ethyl methacrylate polymer made by the Guth Products Company.

The following typesalso gave a coating, but were not preferred because of resistance less favorable than the preferred types of acrylates stated above:

"Butyl methacrylate polymerized to form a solid thermoplastic powder made by the E. I. du Pont de Nemours 8: Co.

Methyl methacrylate polymer.

One acrylate, which gave the best results, was, however, furnished, by the manufacturer, dissolved in ethyleneglycol monoethylether acetate, in which solvent this resin was prepared. This solvent interfered with the proper application of the coating, by etching polystyrene. This neces sitated correction, which could be accomplished:

(a) by removing a large portion of this solvent by distillation;

(b) by carrying out the manufacture of a resin in a different solvent less active on styrene, e. g., ethyleneglycol monomethyl ether;

( c) by compounding with a different film form'- ing body, which has a tendency to repress solvent action on styrene, e. g., a cellulose ester.

This problem, and the three remedies listed, apply to any acrylate resin prepared and furnished in a solution of an active styrene solvent. When an injection molding type acrylate is employed, this problem does not exist; however, the viscosities of such resins are so high as to preclude spraying as the application method, unless an unusually thin coating (less than about .001") is desired. Such solutions can be applied by dipping the object to be coated, or by brushing.

Specific embodiments of the invention are illustrated by the following examples:

Example 1 30% ethyl acrylate was polymerized by refluxing with of benzoyl peroxide in 69 ethyleneglycolmonomethylether, until a sample on drying formed a film having 9. mar resistance at least 10% higher than that of polystyrene by the A. S. T. M. Procedure D 673-421 (falling carborundum grit). of the product thus obtained was dissolved in 80% of a solvent consisting of methyl ethyl ketone, 25% ethanol, and diethylene glycol mono ethyl ether.

The resultant product was brushed on to a polystyrene object, and dried in a forced draft cabinet at 63 C. The resultant coating had a substantially enhanced mar and solvent resistance.

Example 2 25% ethyl methacrylate monomer was polymerized by refluxing in the solvent consisting of equal parts of ethyleneglycolmonomethylether, methyl ethyl ketone, and ethanol. A pressure was maintained so as to permit maintenance of a reaction temperature of 180 C. The reaction was continued until a sample removed and allowed to dry to a. film, gave 9, mar resistance at least 10% higher than that of polystyrene by the A. S. T. M. Procedure D 673-42T.

The resultant product was then sprayed on to a polystyrene object and dried at 70 C. It was found to have a substantially enhanced mar and solvent resistance.

Example 3 Percent by weight Methyl methacrylate polymer 10 The acrylate powder was dissolved in the acetone and esters. When uniform, the remaining solvents were blended into the mixture with agitation. A polystyrene panel was dipped into the lacquer and dried at 55 C. A clear, tenacious coating was deposited on the plastic. This coating had '9. mar resistance substantially higher than polystyrene and was firmly bonded thereto.

The present invention provides an article of manufacture comprising a polystyrene surface having integrally bonded thereto an acrylate coating. In a more specific aspect it provides the combination of a polystyrene surface having integrally bonded thereto a coating comprising an acrylate and a cellulose ester. A coating comprising to 1% of an acrylate and from 0 to 99% of a cellulose ester may be used. Suitable cellulose esters are cellulose aceto butyrate and cellulose aceto propionate.

In the formulas given, the percentage of solids is not critical, as a variation in this factor will only affect the thickness of the resultant coating, and not its qualities.

We may employ any other cellulose ester which is capable of forming a hard tenacious film, for example, cellulose acetate, cellulose acetate propionate, cellulose propionate, and the like. Therein a. similar connection of cellulose acetate hydrogen phthalate is disclosed and claimed in our co-pending application Serial No. 730,193 filed February 21, 1947.

With reference to the solvent combinations stated, instead of methyl ethyl ketone, we may employ any other ketone, ester, toluene or nitro aliphatic substance excepting nitro methane, which has-a boiling range below about C., or combinations thereof. Instead of ethyl alcohol. we canuse nitro methane, or any other aliphatic alcohol, or lactate, having less than 6 carbon atoms. We can also use Butyl Cellosolve" and any other glycol ether having a comparable or higher degree of volatility, diacetone alcohol and the like.

It is possible to work into the formulations even other solvents, plasticizers, pigments, dyestuffs. perfumes and the like as well as other resins and to co-polymerize these or their components with the acrylates disclosed. The term acrylate we understand to include such products, having the essential characteristics herein described in relation to polystyrenes. When thus modifying the compositions, the balance between polystyrene solvents and polystyrene nons'olvents must be maintained. This is done in the following manner: If the coating composition is turbid, the percentage of ketone type solvent or of glycol ether ester should be increased, and likewise if the bond of the coating to the polystyrene is poor. If, on the other hand, the polystyrene surface is etched by the coating composition, then the percentage of these solvents just mentioned should be reduced, in favor of nitro methane, lower aliphaic alcohols, lactates and ethyleneglycolmonomethyl ester, or hydrocarbon nonsolvents such as aliphatic petroleum fractions e. g., kerosene,

or of combinations of these, or other solvents having similar solvent and volatility characteristics.

Suggested ranges of percentage for these groups of solvents are as follows:

Aliphatic ketones and esters, toluene and nitro-aliphatic substances other than nitro- ,methane having a boiling range below 120 0.,

preferred 3 to 25%; usable 1 to 35%.

Nitromethane, aliphatic alcohols and lactates having less than 6 carbon atoms, preferred 5 to the skilled chemist to establish the proper balance for the purposes of this invention, for any particular solvents he may desire to employ.

While reference has been made throughout this application to polystyrene, it is fully understood that this term includes such co-polymers or modified products as are commercially known under the generic term, styrene type resins. This includes copolymers between styrenes and acrylates, polymers with acrylonitrile and like materials known as being suitably co-polymerizable with styrene. The di-vinyl benzenes and their polymers and co-polymers are also included in the generic terms polystyrenes.

It is thus seen that this invention is broad in scope. The specific ranges and examples have been given to illustrate only, and not to restrict the invention in any manner; The invention is to be limited only by the claims in which we intend to cover all novelty inherent in the invention as broadly as possible, in view of prior art.

Having thus disclosed our invention, we claim:

1. An article of manufacture comprising a polystyrene surface, having integrally bonded thereto a coating comprising a substance selected from the group consisting of polyethyl acrylate, polyethyl methacrylate, polymerized butyl methacryldte, ethyl and methyl methacrylate co-polymer and polymethyl methacrylate, said coating being deposited from a composition containing from 1 to 35% of a solvent selected from the group consisting of aliphatic ketones and esters, toluene and nitro aliphatic substances other than nitro methane, having a boiling range below 120 C.; from 2 to 45% of a solvent selected from the group consisting of nitromethane, aliphatic althan nitromethane having a boiling range below 120 C.; 5 to 35% of a solvent selected from the class consisting of nitromethane, aliphatic alcohols, and lactates having 1 to 5 carbon atoms; and to 40% of a substance selected from the group consisting of diacetone alcohol, glycol ethers and esters.

3. A coating composition comprising a substance selected from the group consisting of polyethyl acrylate, polyethyl methacrylate, polymerz'zed butyl methacrylate, ethyl and methyl methacrylate co-polymer and polymethyl methacrylate and a cellulose ester, dissolved in a solvent composition comprising from 3 to of a solvent selected from the group consisting of aliphatic ketones and esters,toluene, and nitroaliphatic substances other than nitromethane having a boiling range below 120 C.; 5 to of a solvent selected from the class consisting of nitromethane aliphatic alcohols, and lactates having 1 to 5 carbon atoms; and 20 to 01' a substance selected from the group consisting of diacetone alcohol, glycol ethers and esters.

4. As claim 3, the cellulose ester being cellulose aceto butyrate.

5. As claim 3, the cellulose ester being cellulose aceto propionate.

6. A coating composition comprising a substance selected from the group consisting of polyethyl acrylate, polyethyl methacrylate, polymerz'zed butyl methacrylate, ethyl and methyl methacrylate co-polymer and polymethyl methacrylate, and a film forming cellulose ester, dissolved in a solvent comprising from 1 to 35% of a solvent selected from the group consisting of aliphatic ketones and esters, toluene and nitro aliphatic substances other than nitro methane, having a boiling range below 120 C.; from 2 to of a solvent selected from the group consisting of nitromethane, aliphatic alcohols and lactates having 1 to 5 carbon atoms; and from 14 to of a solvent selected from the group consisting of diacetone alcohol, glycol ethers and esters.

7. The article of claim 1, further characterized by said coating additionally comprising a cellulose ester.

8. The article of claim 1, further characterized by said coating additionally comprising cellulose acetobutyrate.

9. The article of claim 1, further characterized by said coating additionally comprising cellulose acetopropionate.

10. In a process for enhancing the surface properties of polystyrene by utilizing the high specific adhesivity therefor of certain, synthetic resins, which depends on applying to a polystyrene surface synthetic resinous material having superior surface properties, dissolved in a solvent which does not dissolve or attack polystyrene, the step of applying to a polystyrene surface the composition of claim 2,

resins, which depends on applying to a polystyrene surface synthetic resinous material hav ing superior surface properties, dissolved in a solvent whichdoes not dissolve or attack poly styrene, the step of applying to a polystyrene surface the composition of claim 6.

I JOHAN BJORKSTEN.

STUART O. FIEDLER. LUTHER L. YAEGER.

References Cited in the file of this patent or the original lpaten't UNITED STATES PATENTS Number Name Date 2,071,419 1Moss Feb. 23, 1937 2,034,415 Strain June 22, 1937 2,238,694 Graves Apr. 15, 1941 2,254,904 Moss Sept. 2, 1941 2 ,292,393 Mitchell Aug. 11, 1942 2,332,461 Muskat et a1 M Oct. 19, 1943