US1727964A - Method of heat treating plastic and other material - Google Patents

Description

Spt. 10, 1929.

R. E. COLEMAN METHOD OF HEAT TREATING PLASTIC AND OTHER MATERIAL Filed April 15, 1923 WJJ Patented Sept. 10, 1929.

UNITED STATES-PATENT OFFICE.

BOY E. COLEMAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO ECONOMY FUSE & MANUFAC- TURING 00., OF CHICAGO, ILLINOIS, A CORPORATION OF NEW YORK.

METHOD OF HEAT TREATING PLASTIC AND OTHER MATERIAL.

Application filed April 13, 1923. Serial No. 631,866.

This invention relates to methods of heat An object of the present invention is to p treating plastic and other material and refers provide a method of heat treating materials particularly, although not exclusively, to 1mby which the period of time required for comprovements in heat treating articles contalnplete treatment is materially reduced and a 5 ing organic and volatile ingredients and better product is obtained. which are heated for the purpose of effectlng A further object is to provide a method of acuring operation by which certain-chemical heat treatment which will combine the adc ilnges re l vantages of uniformity of temperature with My invention is especially useful in curing perfect control of the atmosphere in which 10 molded electrical insulating material comthe treatment is carried on.

posed of such ingredients as asbestos for a A further object is to provide a method of base, gilsonite, pitch or other similar material heat treatment by which the temperatures refor a binder, oils which under the effect of quired for perfect treatment may be maheat will combine chemically with sulphur terially reduced.

15 or other hardening agent, or will themselves A further object is to provide a method of polymerize under heat to give the material heat treating materials containing volatile hardness, and a volatile oil to give the mass constituents which will facilitate the removal plasticity while molding. The volatile oils of said volatile constituents. may be relatively heavy, such as coil tar oil A further object is to provide an improved 20 or parafiin oils which are driven off during the methodof heat treatment of materials conheating or curing operation, or may be relataining oxidizable constituents which will pertively light oils, such as naphtha, gasoline, or mit expeditious treatment without danger benzol, which evaporate to a large extent from oxidation or burning. even during the process of mixing and mold- A further object is to provide a method of 25 ing the various ingredients. heat treatment according to which the propor- It has been customary heretofore to cure tions of the various constituents of the treatthe molded material of the character deing atmosphere may be readily controlled. "scribed by placing it in a furnace orfoven A further object is to provide a method ofwhere it is subjected to a relatively high heatcuring molding material by which curing 3'0 from an external source, such as gas burners, may be accomplished expeditiously Without while at the same time air is allowed to cirdanger of premature surface curing. culate through the oven to assist in withdraw- A further object is to provide a method ing the volatilized fumes therefrom. of rapidly curing molded material in which I have found that by using the process as the risk of fire is minimized. V 35 above described there are many disad- Ihave discovered that greatly improved revantages. On account of the presence of air sults may be obtained in the curing of molded at a, high temperature,,th e surfaces ofz'the material of the character mentioned 'by inmolded articles become covered with a layer troducing into the heating chamber or oven of oxidized oils and other material and predry or superheated steam, so that the curing 40 vent the escape of the Volatile ingredients in operation is carried out without the presence 9 the interior of the article. In order to drive of air. By providing for a rapid and free off" these volatile ingredients through the circulation of dry steam throughout the heatoxidized surface excessive heat is required, ing chamber, the heat within the same is kept which causes an overcuring of the surface evenly distributed, while at the same time 46 and results in lack of uniformity throughout oxidation of the surface of the material being 5 the body of the material. Moreover, the excured is prevented. The result of the latter tent to which the temperature can be inis that the volatile oils have an opportunity creased is distinctly limited, as with the into readily escape, and, in fact. their distillacrease of temperature, the danger of injuring tion is greatly facilitated by the. presence of 50 the material by fire also increases. the steam itself, particularly in the case of obtained, while all danger of fire is eliminated.

be mentioned the drying of certain varnishes,

I have found by actual experience that the time required for curing has been reduced by more than fifty per cent, not only resulting in great economy of operation, but also a much improved product.

My method of treatmentjs also applicable to a wide varietyof uses, among which may paints, enamels, apans and similar materials i applied to the surface of any suitable article.

In this case the'volatile constituents of the varnish are rapidly driven off in the presence of dry steam. In the case of drying these materials it is advisable to effect a slight oxidation, and this is controlled to exactly the desired extent by admitting a definite proportion of air, which is mixed with the steam to give the desired result.

In the accompanying claims the term flowability conferring agent is intended to be inclusive of volatile oils for conferring plasticity to insulating material and for conferring fluidity to varnish and the like.

In certain instances it is also possible to use other non-oxidizing gases besides steam, such as carbon dioxide or the like, but in cases in which it is desired to drive off heavy oils I have found that this is effected particularly advantageously by dry or superheated steam.

The accompanying drawings illustrate an oven in which my improved method of heat treatment may be used. In the drawings' Figure 1 is a front elevation, partly in section, illustrating an oven which may be used in carrying out the present invention; and

Figure 2 is a sectional view taken on the line 2'-2 of Figure 1.

The oven 1 comprises the outer shell or casing 2 and the inner shell or casing 3. The shells or casings 2 and 3 are sealed together at their uppermost portions, the inner casing 3 preferably being spaced from the outer casing 2 whereby to provide a chamber 4 surrounding said casing 3. Thechamber 4 may communicate by means of pipes 55 with the outlet main 6. The casing 3 may have the dome-shaped top portion 7 provided with the outlet fine 8.

Mounted in the lower portion of the outer casing 2 is the fuel inlet pipe 9, which communicates with the series of burners 1010, which may be elongated pipes extending from one side of the oven to the other side thereof, as clearly shown in Figure 2. The gas flames from burners 10-10 play upon the under side of the casing 3 to maintain a predetermined temperature within the casing 3,

which temperature should be 100 degrees C. or higher for the purpose of maintaining the steam therein in' a dry or superheated condition. The supply of fuel to the pipe 9 may be controlled by the valve 11. Though the oven has been illustrated with heating means comprising burners, it will be clear that any other preferred heating means may be einployed, such, for instance, as electric heaters, heating coils which may contain oil or hot air, or any other type of heater. The type of oven and type of heater constitute no part of the present invention;

Communicating with the lower portion of the inner casing 3 is the pipe 12, which may be controlled by means of the valve 13. Said pipe 12, in the practice of the present invention, may conduct steam to the interior of casing 3 for a purpose whichwill be referred to hereinafter. Also communicating with the lower portion of easing 3 is the pipe 14, which pipe 14 may also have communication with the super-heater 15. Steam may be admitted to the casing 3 by way of superheater 15 and pipe 14, the supply of superheated steam being controlled by the Valve 16. Pipes 12 and 14 may be extended into the casing 3 to distribute the fiow from said pipes 12 and 14 uniformly through said casing 3. A perforated false bottom 17 may be provided near the bottom of the casing 3 to improve the uniformity of the distribution of the steam from the pipes 12 and 14 through the casing 3. An inlet pipe 18 may be provided communicating with the bottom part of easing 3 below the false bottom 17 for admitting air, oxygen, or other active gas to said casing 3. Said inlet 18 will be provided with the valve 19 for controlling the flow of gas therethrough. The pipes 12 and 14 and the inlet 18 will preferably each be provided with flow meters 20 for the purpose of indicating the flow through their respective pipes. By noting the indications of the flow meters an operator may control to a nicety the relative I supplies of inert gas and active gas.

According to the present invention the material is treated in an atmosphere of inert gas, preferably dry steam, said steam being maintained at or above the boiling point of water by any preferred means.- In the oven illustrated, the steam entering the casing 3 through pipe 12 is maintained above the boiling point of water by means of the burners 10-10. If preferred, the steam may be superheated before entering the oven, the steam then being introduced through pipe 14 after passing through the superheater 15. In any event, the steam is kept hot and dry. The temperatures of volatilization of the volatile constituents of the material being treated are materially lower in an atmosphere of steam than in an atmosphere of air, and a large proportion of said volatile constituents may be volatilize'd in an atmosphere of steam at a temperature much lower than is necessary inatmospheric air. The reasonwhy a large proportion of the volatile constituents may be volatilized in an atmosphere of steam at a temperature lower than is necessary in atmospheric air is that in the case of heat treatment in air the flowability conferring agents polymerize excessively, resulting in a rise in temperature due to such polymerization which is very diflicult to control. By treating in a flowing inert atmosphere or in an atmosphere containng a regulated amount of air or the like, the polymerization necessary to give hardness is accomplished without undue rise in temperature, any tendency to excessive temperature being minimized due to the flowing inert atmosphere, which acts merely as a vehicle and not as a supply of fuel to unduly promote polymerization. By reason of the lower temperature required, premature surface curing is avoided. Furthermore, by reason of the fact that in an atmosphere of steam there is a minimum, if any, oxidation, a stronger circulation and more even distribution of heat may be provided than is feasible with atmospheric air, and also the volatile constituents of the material being cured may thus be more rapidly carried off. By reason of the fact that remature surface curing is avoided, the lia ility of warping, cracking and blistering, which are common in air treatment, is mimmized.

In certain heat treatments of materials,

, such. as the drying of certain varnishes,

paints, enamels, japans and similar materials, there is a decided advantage in supplying a limited amount of air to the materials being treated. Difficulty is encountered, however, if the suppl of air is merely throttled, due to the fact t at a relatively rapid flow of gases is required through the oven to pro vide the necessary circulation, distribution of heat, and carrying oif of volatile products coming from the material being treated. 'According to the .present invention, the relative supplies of'dry steam and air, or other active material, are controlled by the valves 13, 16 and 19. The dry admitted through the steam acts as a carrier for the desired limit amount of air or other active gas, wherebyv a rapid circulation of gasesis maintained through the oven, while any excess of air or other active gas isavoided;

The characteristics of the product resulting from the'use of roved method may be controlled by varym t e amount of steam or other at t e different stages of the process, or by varying the temperatures used, or by va' both the amount of steam or other gas and t e temperature. Furthermore, the chemical composition and the shape and size of the articles being treated will be factors in the determination of thes ecific procedure followed, this being determ nable occur to those skilled in the art. It is intended in this patent to cover all such modifications that fall within the scope of the invention as defined by the appended claims.

I claim:

1. The method of treating material having as important constituent-s thereof a base an a flowability conferring agent, the latter of which includes a volatile oil, which consists in heat treating said material in flowing inert atmosphere maintained in dry condition, said inert atmosphere being maintained at a temperature sufficient for curing said material, the rate' of flow being sufficient to hold down the polymerizing effects of said flowability conferring agent to prevent such polymerization from causing an undue rise in temperature.

2. The method of treating material having as important constituents thereof a base and a flowability conferring agent, the latter'of which includes a volatile oil, which consists in heat treating said material in an atmosphere of flowing steam maintained in dry condition at a temperature sufficient for ouring said material, the rate of flow being sufficient to hold down the polymerizing elfects of said flowability conferring agent to prevent such polymerization from causing an undue rise in temperature.

3. The methodof treating material having as important constituents thereof a base and afiowability conferring agent, the latter of which includes a volatile oil, which con,-

sists in heat treating said material in a flowof April, 1923.

ROY COLEMAN.

by simple experimentation in individual cases.

It will be clear-that many. modifications of the exact method whichI have described. will

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