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United States Patent Office Patented Dec 3,225,017 United States Patent Office Patented Dec. 2, 1965 2 the necessity of separate shipping containers for the base 3,225,017 polymer and curing agent which complicates shipping IMOD FED POLYSULFEEDE (COMPOSITION problems and facilitates mixing errors through the use Irvin P. Seegman and Lester Morris, Encino, and Paei A. of the wrong ingredient or amount of ingredient. Ac Mallard, Woodland Hills, Calif., assignors to Products cordingly, the curing of liquid polysulfide polymers with Research Company, Burbank, Calif., a corporation of out the need of a separately compounded curing agent or California mixing immediately prior to application would be highly No Drawing. Fied Oct. 30, 1961, Ser. No. 148,757 desirable. 6 Claims. (C. 260-79.) Because of these problems, there have been many at In general, the present invention relates to liquid poly 10 tempts to develop more convenient methods of curing Sulfide polymer compositions and methods of treating said liquid polysulfide polymers. For example, the base poly compositions. More specifically, the present invention mer composition has been pre-mixed with the curing relates to one-part, stable, curable liquid polysulfide com agent under anhydrous conditions and then immediately position and method for treating same wherein initiation prior to use, water is added by mixing with such pre of curing by mixing with separate activating or curing 15 mixed composition. See, for example, Patrick 2,466,963 agents immediately before deposition in place is elimi and Gregory 2,787,608. Such procedure, of course, nated. avoids the problems involved in handling the curing agent Polysulfide polymers in general have been known for separately; however, such procedure still necessitates mix a number of years. See, for example, United States Pat ing immediately prior to application with its attendant ents Nos. 1,890, 191; 2,049,974; 2,100,351; and 2,216,044. 20 disadvantages already noted above. In general, the pre Likewise, liquid polysulfide polymers, although more re mixed compositions require mixing to incorporate water, cent, have also been known for several years. See, for additional reactants or both. Without such features, the example, United States Patents Nos. 2,466,963 and present pre-mixed compositions have impractically long 2,474,859. The liquid polymers are particularly useful curing times and at best can only be used for thin films. in a wide variety of applications because of the ease of 25 The present invention involves a one-part, stable liquid handling a liquid material and the fact that they are polysulfide polymer composition and method which can capable of being vulcanized even at room temperature to be completely cured without agitation immediately prior a rubber-like material having the desirable physical char to deposition. The composition of the present invention acteristics of the cured polysulfide rubber. Such desir may be deposited in place and then cured solely by con able characteristics are: excellent resistance to a wide 30 tact of its surface with surroundings containing essential range of solvents; low diffusion rate of gases; good re ly only moisture. Thus, the present invention eliminates sistance to oxidation, ozone, and weathering; adherence any mixing step immediately prior to use and consequent to metal; and a service temperature range from about ly eliminates air bubbles in the cured polysulfide rubber. -70 F. to 200 F. As a result, the liquid polymers Also, the composition of the present invention may be have been extensively used as sealants in pressurization 35 packaged in a single suitable container and applied di and air and gas duct applications, as protective linings rectly to the place where it is used. After deposition in in gasoline reservoirs and containers, as adhesives, and place, merely by contact with atmospheric air, even thick in many other useful applications. bodies of composition may be cured without the addition Despite the usefulness and demonstrated practical of separate curing agents. merit of the polysulfide liquid polymers, present tech 40 in general, an object of the present invention is a com niques of formulating and curing the polymers are not en position and method for providing one-part, stable liquid tirely satisfactory. Specifically, after suitable compound polysulfide polymers which can be cured without agita ing of the base polymer with fillers, reinforcing pigments tion solely by contact of its surface after deposition in and the like, cure is normally initiated just prior to use place with surroundings containing essentially only mois by adding a separately compounded curing agent such ture. as an oxidizing agent, e.g., lead dioxide or zinc peroxide. Another object of the present invention is to provide Since either the base polymer, or the curing agent or such compositions in completely pre-mixed form and suit both normally contain moisture, the curing agent and the ably packaged in a single cartridge so that the composi base polymer require extensive mixing immediately prior tion may be directly deposited in place without the need to use and cannot be pre-mixed. As a result, properties 50 of power mixers, stirrers or the like. of the product depend to a large extent on an accurate Still another object of the present invention is to pro proportioning and careful blending of the separate in vide a method whereby thick bodies of liquid polysulfide gredients, often unobtainable with the equipment available polymers may be cured and the presence of air bubbles in the field. virtually eliminated. The liquid polymers preferably employed are quite vis Other objects and advantages of the present invention cous, resembling a syrup or thick molasses so that proper will be apparent from the following disclosure of ex mixing is obtained only through the use of rotary beaters emplary embodiments and from the specific examples or other power mixers. Such equipment invariably in and tabular data enumerated therein which enables one corporates myriads of small air bubbles into the mix, skilled in the art to know how to practice the invention. rendering the applied composition undesirably porous; 60 In general, the present invention involes a one-part, during cure or later use at a high temperature, the en stable, hygroscopic liquid polymer composition compris trapped air bubbies frequently cause ruptures or the ing essentially a liquid polyalkylene polysulfide polymer. formation of blisters in the cured film or body, thereby The polymer has thoroughly dispersed therein a dormant shortening its useful life. Moreover, heat generation due curing agent for it which is activated by the presence of to the mixing tends to decrease the application life of moisture. Likewise, the polymer has thoroughly dis the curing polymer and to vary the desirable character persed therein a water-soluble deliquescent accelerating istics of the product. A further practical difficulty is agent adapted to attract and absorb moisture from the 3,225,017 3. 4. Surroundings and to hasten the curing of the polymer by pyrophosphate peroxide, sodium carbonate peroxide and the curing agent. The polymer may be initially dried to sodium perborate; the alkali earth metal peroxides such remove moisture or, preferably, the deliquescent accelerat as calcium peroxide and barium peroxide; and other metal ing agent may also be a desiccating agent to dry the peroxides such as zinc peroxide and manganese dioxide polymer. Alternatively, the polymer may have thor and oxidizing agents such as ammonium dichromate may oughly dispersed therein a single desiccating, deliquiescent, be used. dormant curing and accelerating agent which is adapted The deliquescent accelerating agent is preferably a des to dry the polymer, to attract and absorb moisture from iccant and must be water-soluble. It has been found that the Surroundings, to cure the polymer when activated by alkaline materials such as alkali metal and alkaline earth the presence of moisture and to hasten the curing of said 0 metal oxides, peroxides, hydroxides and salts of weak polymer. Such surroundings may include a body of water acids have such useful characteristics. Some specific ex or a body of gas containing essentially only moisture amples of such compounds which may be used are sodium Such as atmospheric air of normal humidity. oxide, sodium peroxide, potassium hydroxide, sodium hy The particular polysulfide polymers involved in this in droxide, sodium acetate, sodium carbonate, sodium phos vention are called "polyalkylene polysulfides' and may 5 pate, sodium molybdate, calcium oxide, barium oxide, be represented by the general formula: calcium peroxide, barium peroxide, calcium hydroxide, strontium hydroxide. In addition, it has been found that S barium oxide is unexpectedly unusually effective as a HSRSS... RSS... RSH desiccating, deliquescent accelerating agent. These polymers are composed essentially of the unit RSS 20 It should be noted that the alkali metal and alkaline and the molecular weight will vary with the number of earth metal peroxides, such as sodium peroxide, calcium these units in the molecule, and also with the specific peroxide and barium peroxide may be used as single des Structure of the organic radical R in the molecule. For iccating, deliquescent, curing and accelerating agents. convenience in describing these polymers, organic radical The amount of curing agent and desiccating, deli R may be defined as any polyvalent organic radical con 25 quescent accelerating agent mixed with the polyalklene taining at least the grouping -CH2-- which results from polysulfide polymer may vary substantially due to the the splitting off at least two carbon-attached negative inactive state of the curing agent when the composition Substituents from the organic compound initially contain is kept in dry surroundings. However, it is desirable that ing said constituents and said splitting being done by re the curing agent be present in at least a stoichiometric acting said compound with an alkali metal polysulfide. 30 amount so as to be sufficient to provide a satisfactory rate However, all of the polymers are characterized by poly of cure and complete vulcanization.
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