SUGGESTED CITATION

E. J. Termine R. W. Atwell, H. A. Hodgen and N. A. Favstritsky United States Patent No. 5,380,802.
Available at: http://termine.com/archives/582

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to flame-retarded fibers, and more particularly to flame-retarded, polyolefin-based fibers. The inventive flame-retarded fibers are comprised of a thermoplastic polyolefin and a ring halogenated vinyl aromatic grafted onto a polyolefin, and may also include a halogenated bisphenol derivative.

2. Description of the Prior Art

Polyolefin fibers–predominantly polyethylene and polypropylene–are high volume/low cost synthetics that are remarkable for their stain and abrasion resistance. As with all plastics, certain uses have required that the flammability of the polymer be reduced. When decreased flammability has been required, it has generally not been provided by the fiber itself, but has instead been provided by one of the other components in the fabricated article. In carpeting, for example, enough fire retardant can be loaded into the latex binder to provide a measure of protection for the polyolefin face fiber.

One reason why the fiber itself has not been formulated to contain fire retarding agents is that no fire retarding agent has been found which leaves the fiber with an acceptable balance of normal polyolefin properties. In addition, the presence of an additive often adversely affects the melt spinning operation. For example, hexabromocyclododecane (“HBCD”) can be compounded into polypropylene and the blend melt extruded into fibers. To be economical, however, the fiber must be produced at as high a rate as possible. This requires that melt viscosity be reduced by raising the die temperature. Unfortunately, normal processing temperatures for polypropylene cause degradation of HBCD and impart an unacceptable brown color to the fiber.

Many attempts have been made to produce acceptable ignition resistant polyolefin fibers and fabrics. Much of this work has focused on topical applications in which flame retarding agents were coated onto the surface of fibers after the fibers had been produced. Permanence was not always assured, as often the active ingredient was merely dispersed in a polymeric binder which was “painted” onto the polyolefin fiber. The quality of the binder determined the longevity of the treatment.

More sophisticated topical methods utilized phosphorus- or halogen-based monomers which were applied to the fiber and crosslinked in place. While providing ignition resistance, these approaches change the feel or “hand” of the fabric and reduce a key property of the polyolefins–soil resistance.

An important limitation of topical applications is that they are restricted to use with spun fiber, or more commonly, with constructed fabrics. They cannot be applied to the resin prior to–or what would be the most efficient, during –the fiber spinning operation. Topical applications therefore require an additional and costly step in the production process.

Other attempts to provide flame retardancy employ an “additive” approach. Almost any non-volatile compound containing bromine or chlorine may be mixed into polyolefins to provide some measure of ignition resistance. None has been successfully commercialized due to problems with the strength, color, odor or toxicity of the fiber.

One problem with known flame retardant additives is the difficulty of effectively dispersing them into the molten polyolefin. Additives are generally powders which do not dry blend evenly with plastic pellets. Because this mixture is fed directly from the melt extruder to the spinning die, localized concentrations of undispersed flame retardant will occur. This will cause plugging of the spinnerette and filament breakage, requiring a shutdown of tile process. One solution is to pre-disperse the additives in a suitable thermoplastic resin to form concentrated plastic pellets containing the modifiers. This solution, of course, requires additional and costly steps in the production process.

To avoid the problems associated with additives, attempts have been made to chemically bond modifiers to the polyolefin molecule to provide ignition resistant fibers. In one process, elemental chlorine and bromine are attached to the surface molecules of polyolefin fibers and films to provide self-extinguishing behavior. Similarly, the grafting of vinylchloride or vinylidene chloride to the surface of polyolefin fibers in order to obtain diminished flammability is known. As with the topical applications, these grafting approaches suffered from the limitation that they could only be applied as post-treatments, requiring additional steps in the production process.

Polyolefin fibers containing non-halogenated styrene grafted to polypropylene have also been manufactured. In one method, polypropylene-g-styrene is co-spun with polypropylene to produce a highly crimped fiber with good tensile strength. Similarly, the grafting of styrene onto pre-formed polypropylene fibers is known. In one method, a halo styrene in the form of chloromethylstyrene is grafted to polypropylene fiber to produce a material with improved sticking temperature, color fastness, water retention, antistatic behavior and wool-like hand with uniform dyeability. None of these methods provides adequate flame retardancy while retaining reasonable textile properties. Also, these approaches are generally limited to post-treatment of the fiber and therefore include the previously-discussed disadvantages incumbent therewith.

Concerning bromostyrene graft copolymers specifically, U.S. Pat. No. 5,077,337 to Atwell et al. discloses graft copolymers represented by the formula: ##STR4## in which n is an integer >1; P is a polyolefin; and S is a side chain grafted to the polypropylene and having monomeric units of the formula: ##STR5## in which x=1 to 4; R.sub.1 is H or CH.sub.3 ; and R.sub.2 is H or a C.sub.1-4 alkyl, and notes that such graft copolymers would be an improvement over inert additives in the production of flame retardant spun fibers because clogging of spinnerettes and equipment wear would be avoided.

A need therefore exists for a polyolefin fiber which melts into the base polyolefin under normal spinning conditions leaving no solid particles to plug spinnerettes. A need also exists for a polyolefin fiber which is thermally stable, non-topical, non-blooming, non-volatile, UV stable, dry blendable and spinnable into 2 to 3 dpf microfibers without extra compounding steps. Also, a need exists for such a fiber which further does not impart objectionable odors to the spun fiber or constructed fabrics made thereof, and which has essentially the same texture or hand as nonflame-retarded fibers. Finally, a need exists for such a fiber which is further insoluble in water and is evenly distributed throughout the fiber to make it extremely resistant to removal by normal laundering conditions. The present invention addresses these needs.

SUMMARY OF THE INVENTION

Briefly describing the present invention, there is provided a flame-retarded polyolefin fiber made of a thermoplastic polyolefin and a graft copolymer composition represented by the formula: ##STR6## wherein n is >1, PP is polypropylene, and S is a grafted side chain having halogenated monomeric units of the formula: ##STR7## wherein x=1 to 4; R.sub.8 is H or CH.sub.3 ; R.sub.9 is H or a C.sub.1-4 alkyl group; and R.sub.10 is Br or Cl. In an alternate embodiment the flame-retarded polyolefin fiber further includes a halogenated bisphenol derivative represented by the formula: ##STR8## wherein R.sub.1 to R.sub.4 are H, CH.sub.3 or halogen; R.sub.5 is H, dihaloethyl, dihalopropyl or dihalobutyl; arid A is a single bond, O, CO, S, SO.sub.2 or C(R.sub.6)(R.sub.7), where R.sub.6 and R.sub.7 are H or a C.sub.1-4 alkyl.

One object of the present invention is to provide a flame-retarded polyolefin fiber which displays minimal or no bloom of the incorporated flame retarding agents.

A further object of the present invention is to provide flame-retarded polyolefin fabrics which are useful in home, institutional and industrial settings, and which generally exhibit the desirable properties of unmodified fabrics.

A further object of the present invention is to provide flame-retarded polyolefin fibers having very fine denier without resorting to extraordinary mixing procedures.

Further objects and advantages of the present invention will be apparent from the following description
_____________________________________________________________________

DOWNLOAD FULL TEXT

Bromine production is based on the direct feed of brine rich in bromine ions, chlorine, and steam into the reaction tower. The following block flow diagram illustrates the concept of a bromine production process.

Bromine-generating Step

Hot brine rich in bromine ion is input to the reaction tower from above, while chlorine gas and water are introduced from the bottom of the reaction tower. In the reaction tower an oxidation-reduction reaction takes place, generating bromine:

2Br-(aq) + Cl2(g) → Br2(g) + 2Cl-(aq)

It is necessary to heat the system to prevent the bromine from remaining in solution. Heating is provided by steam, which actually serves two purposes:

1. Heating of the reaction tower above 100°C (100°C –120°C).
2. Removal of the bromine from the solution (the steam carries the bromine vapors with it).

The gas mixture containing the bromine vapors, residual chlorine and steam rises to the top of the tower, while the liquid brine accumulates at the bottom of the tower. The tower is packed with suitable filling materials (rings or disks made from resistant materials) to increase the contact area and the reaction time between the gases and the solution.

Bromine Separation Steps

A mixture of hot gases containing bromine, chlorine and water vapor leaves the top of the tower. This mixture undergoes a number of work-up steps.

1. Condensation

The first step is to cool the gas mixture. The hot gas mixture arrives in the condenser, which has a temperature at which bromine, but not chlorine, condenses. At the temperature conditions in the condenser, the chlorine gas is separated from the liquid and after leaving the bromine and water-rich condenser it is returned to the reaction tower. The liquid phase containing chlorine and water-containing bromine is transferred t0 a separator.

2. Separation

Two layers are formed in the separator. The heavy, lower layer is the bromine. The lighter, upper layer is the aqueous layer. The aqueous layer contains bromine and chlorine, which are slightly soluble in water. After separation, this layer is recycled to the reaction tower. The bromine layer, which contains chlorine and water as impurities, is further purified as necessary.

3. Purification and Drying

Bromine obtained after the separation step is not completely pure and contains chlorine and water. The chlorine and most of the water are separated by distillation and recycled to the reaction tower. Residual water is removed by a drying process, such as by treatment of wet bromine with concentrated sulfuric acid.

Process Improvements

Today, bromine manufacturing process has evolved into the use of vacuum recovery of bromine, and the steps for generating and distilling bromine have merged into one unit operation.

SUGGESTED CITATION

Smoke Suppressed Flame Retardant Unsaturated Polyester Resin Compositions. E. J. Termine, N. A. Favstritsky and K. G. Taylor, United States Patent No. 5,346,938.
Available at: http://termine.com/archives/531

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to thermoset polymers and specifically to additives which provide smoke suppression to unsaturated polyester (“UPE”) and other thermoset resin compositions and enhance the effect of flame retardant agents incorporated therewith.

2. Description of the Prior Art

It is known in the art that the flammability of thermoset resins such as unsaturated polyesters can be reduced by incorporation of a flame retardant agent. Typical flame retardant agents include reactive or additive halogenated organic compounds, inorganic fillers, and special formulations based on phosphorous and ammonium salts.

Although efficient in suppressing the rate of combustion in a resin system, most flame retardants tend to affect adversely one or more key properties of the resin. For example, many flame retardant additives are ineffective at producing low smoke (“smoke suppressed”) formulations.

Recent public awareness about risk and hazard assessment during fire situations, and technical limitations of conventional flame retardant additives warrant a need for improved flame retardant thermoset compositions. In particular, a need exists for a thermoset composition that passes flammability standards with low smoke and combustion by-product formation, and does not detract from overall polymer performance.

Many prior art references describe the use of a variety of smoke additives in unsaturated polyesters. Modern Plastics Encyclopedia, Vol. 63, No. 10A, McGraw-Hill, Inc., pp. 179-180 (1986). However, the selection of a suitable smoke suppressant for thermoset resins is not predictable. Selection is particularly difficult when flame retardants are employed, exacerbated by the complex interaction between the polymer and the flame retardant agent.

Hechenbleikner, et al. describe in U.S. Pat. No. 3,293,327 the production of bicyclic phosphites, phosphonates, thiophosphates, and selenophosphates. These compositions are said to be stabilizers for vinyl halide resins. They are alleged to be useful as heat stabilizers for vinyl chloride resin, and as antioxidants for fats and oils. The Hechenbleikner patent does not specify the use of bicyclic phosphates to achieve low smoke thermoset resin compositions, nor does it disclose that cyclic phosphates of the present invention could be used with flame retardant agents to produce smoke suppressed flame retardant thermoset compositions.

British Patent No. 999,793 describes a process for producing organic phosphates by subjecting organic phosphites to reaction with peracetic acid. This patent shows a method for producing the most preferred bicyclic phosphate of the present invention, 2,6,7-trioxa-1-phosphobicyclo[2.2.2]-octane-4-methanol -1-oxide and teaches the use of acetal ring-containing phosphates as plasticizers or functional fluids. The British patent, however, does not disclose the present invention. It does not mention bicyclic phosphates as being useful for flame retardant thermoset resins, nor that the most preferred bicyclic phosphate of the present invention can be used with flame retardant additives to yield improved thermoset compositions.

Hills, et al. describe in U.S. Pat. No. 3,873,496 a flame retardant polyester composition which contains 5 to 25 percent of a hydroxymethyl bicyclic phosphate compound as a flame retardant additive. Hills did not observe the ability for bicyclic phosphates to act as smoke suppressors for thermoset resin compositions which employ other compounds as the primary flame retardant additive.

Halpern, et al. describe in U.S. Pat. No. 4,341,694 a composition comprising 2,6,7-trioxa-1-phosphobicyclo[2.2.2]-octane-4-methanol-1-oxide and a nitrogen-containing co-additive, which are intumescent and are adaptable to flame retard polyolefins, polyvinylaromatic resins, polycarbonates, PVC and blends thereof. Halpern did not observe any smoke suppression of the present invention. Further, the present invention is not directed to providing intumescence, and operates in the absence of nitrogen compounds required by Halpern, namely compounds which are effective with the phosphates to provide intumescence, comprising ammonium compounds and derivatives of ammonia including amines, ureas, guanidines, guanamines, s-triazines such as melamine and ammeline, amino acids and peptides, as well as salts and derivatives thereof.

Parr, et al. describe in U.S. Pat. No. 4,801,625 a flame resistant composition having (1) an organic polymeric substance in intimate contact with (2) a bicyclic phosphorous compound, and (3) a gas producing compound. Parr is silent on the use of bicyclic compounds to attain smoke suppressed flame retardant thermoset compositions.

Accordingly, a primary object of this invention is to provide smoke suppressed flame retardant thermoset resin compositions.

A related object is to provide flame retardant unsaturated polyester resin compositions with a reduced tendency to smoke under burning conditions. A further object is to provide unsaturated polyester resin compositions incorporating bicyclic phosphate compound and flame retardant agents.

SUMMARY OF THE INVENTION

The foregoing and other objects, advantages and features of the present invention may be achievable with smoke suppressed thermoset resin compositions incorporating an additive mixture comprising a flame retardant agent and a smoke suppressant bicyclic phosphate compound of the the following Formula (I): ##STR1## where X is OH, OR’, or OC(O)R’; R is H or a saturated or unsaturated straight-chain or branched-chain C.sub.1 -C.sub.17 alkyl; and R’ is a saturated or unsaturated straight-chain or branched-chain C.sub.1 -C.sub.17 alkyl. The present invention is particularly useful with isophthalic unsaturated polyesters, orthophthalic unsaturated polyesters, vinylester resins, and epoxy resins. Compositions in accordance with this invention exhibit a reduced tendency to smoke under burning conditions.
_________________________________________________________________________________________________

Download Full Text

SUGGESTED CITATION

Polymers of Brominated Styrene. E. J. Termine R. W. Atwell, H. A. Hodgen, W. R. Fielding and N. A. Favstritsky, United States Patent No. 5,304,618.
Available at: http://termine.com/archives/525

FIELD OF THE INVENTION

The present invention relates generally to polymers of brominated styrene, and more particularly to methods for the solventless bulk polymerization of brominated styrenes.

BACKGROUND OF THE INVENTION

A variety of polymers of brominated styrene are known to the art. These brominated polystyrenes are commonly used as flame retardant additives, and are produced by one of two basic methods–the bromination of polystyrene or the polymerization of bromostyrene monomers.

In general, the materials made by the two production methods are not equivalent. For example, bromination of polystyrene will result in undesirable side chain halogenation, causing a reduction in thermal stability or requiring expensive treatment to remove the more labile bromine atoms. Polymers prepared by the polymerization of bromostyrene do not have undesirable side chain halogenation, and are preferred for their relatively greater thermal stability.

Not only do the two methods of preparing brominated polystyrenes provide different end products, there are also numerous disadvantages inherent to the bromination of polystyrene approach. First, such methods require that the polymer be solubilized, necessitating isolation and purification procedures that may add significantly to production costs. Also, because the product is recovered from solution, the final product will be a dusty powder unless some type of compaction step is included at additional cost. Similarly, unless a post-production compounding step is used, the introduction of co-additives is limited to dry blending with other powders.

A more significant disadvantage of the bromination of polystyrene method is that the brominated polystyrenes produced are limited to copolymer compositions and molecular weights that are readily available. In addition, the products must be structures that are stable to, and will not interfere with, the bromination process.

The polymerization of bromostyrene has several advantages over the bromination of polystyrene. As mentioned, it provides a more thermally stable product because side chain halogenation is avoided. Also, this method can be used to produce a continuum of molecular weights and bromine contents not otherwise available. Further, the polymerization can be accomplished without the use of solvents, and is readily adaptable to more economical continuous production processes. In addition, a broad spectrum of copolymer compositions may be produced simply by adjusting the monomer feed. Finally, production of convenient non-dusting pellets (with the option of incorporating auxiliary additives) is a natural by-product of the inventive polymerization process, and may be provided at no additional cost.

Nowhere in the literature of bromostyrene polymers is there any indication that the practical bulk polymerization of these monomers to produce a highly brominated compositions has been addressed. One reason for this omission may be the lack of thermal stability of the brominated materials. Conditions that would normally be used to prepare commercial polystyrene (such as flash devolatilization at temperatures approaching 300.degree. C.) would cause thermal breakdown of most brominated materials, and product discoloration and equipment corrosion would result. Processes using solution and emulsion techniques avoid any possibility of decomposition, even though they are at an economic disadvantage.

A need therefore exists for improved methods of continuously polymerizing bromostyrenes. In particular, a need exists for a method of polymerizing bromostyrenes without the need of solvents and their associated disadvantages. A need also exists for a method of polymerizing bromostyrenes in which the reaction is run to a high degree of completion in a relatively brief period of time. The present invention addresses these needs.

SUMMARY OF THE INVENTION

Briefly describing one aspect of the present invention, there is provided a process for the solventless polymerization of brominated styrenes, comprising the steps of: (a) blending monomers of brominated styrenes with a polymerization initiator; (b) feeding the monomer/polymerization initiator mix into a prepolymerizer wherein the monomers begin to polymerize; and (c) feeding the monomer/polymerization initiator mix and the partially polymerized bromostyrene into a screw-type extruder to drive the polymerization to a high degree of completion in a short period of time. Optionally, the monomers may be preheated before mixing with the initiator, or a heater may be included in the prepolymerizer. Also, a second initiator may be used to facilitate polymerization in the extruder reaction zone.

One object of the present invention is to provide a continuous process for producing brominated styrene homo- and copolymers, wherein the process uses an extruder for at least a portion of the polymerizations.

A further object of the present invention is to provide a screw-type extruder effective for providing a high degree of conversion from monomer to polymer while maintaining an unexpectedly high molecular weight.

A further object of the present invention is to provide an improvement to the basic polymerization process in which the early stages of the polymerization are carried out in a prepolymerizer which may optionally be preceded by a preheater.

It is also an object of the present invention to provide an improved polymerization process in which the free radical source for the prepolymerizer is selected so as to provide rapid initiation at temperatures below 100.degree. C.

Another object of the present invention is to provide an improved polymerization process in which desired additives may be introduced continuously into the brominated polymer during polymerization, thereby avoiding the expense of a separate compounding step.

An additional object of the present invention is to provide polymers that contain about 50% or more by weight of brominated styrene and that are useful as flame retardant additives.

A further object of the present invention is to provide a flame retarding polymer comprised predominantly of brominated styrene and having an APHA solution color of less than 500 following heat ageing for eight hours at 243.degree. C. in a test tube.

Additional objects and advantages of the present invention will be apparent from the following description of preferred embodiments.
__________________________________________________________________________________________________

Download Full Text

In contrast, produced water is naturally occurring water found in shale formations that flows to the surface throughout the entire lifespan of the gas well. This water has high levels of TDS and leaches out minerals from the shale including barium, calcium, iron and magnesium. It also contains dissolved hydrocarbons such as methane, ethane and propane along with naturally occurring radioactive materials (NORM) such as radium isotopes.

At some point, the water that is recovered from a gas well makes a transition from flowback water to produced water. This transition point can be hard to discern, but it sometimes identified according to the rate of return measured in barrels per day (bpd) and by looking at the chemical composition. Flowback water produces higher flowrate over a shorter period of time, greater than 50 bpd. Produced water produces lower flow over a much longer period of time, typically from 2 to 40 bpd2. The chemical composition of flowback and produced water is very similar so a detailed chemical analysis is recommended to distinguish between flowback and produced water.

For additional information, see:

1. Marcellus-Shale. US. 2011. Flowback and Brine Treatment in Pennsylvania. Retrieved March 21, 2011 from http://www.marcellusshale.us/drilling_wastewater.htm

2. Vidic, R.D. 2010. Sustainable Water Management for Marcellus Shale Development. Retrieved March 21, 2011 from http://www.temple.edu/environment/NRDP_pics/shale/presentations_TUsummit/Vidic-Temple-2010.pdf

Primary Author: Erich Schramm —- Posted: 24 March 2011 —- Version: Original

Schramm, E. 2011. What is flowback, and how does it differ from produced water? Institute for Energy and Environmental Research of Northeastern Pennsylvania Clearinghouse website. http://energy.wilkes.edu/pages/205.asp.

> Connate water which is present in the reservoir prior to production
> Condensed water which is condensed from the produced gas in the production tubing and topside equipment
> Injected water which is originated from the injection wells adjacent to producing well

Produced water composition

Physical and chemical properties of produced water vary depending on many factors including:

> Reservoir geology
> Hydrocarbon composition
> Geographical location
> Water injection history

The chemical composition of produced water will change during the production lifetime of a reservoir. Most production wells produce dry oil at the beginning of the field life. Produced water volumes increase slowly as connate water begins to contaminate the oil. The water cut increases at an accelerated rate once the water/oil interface reaches the wells, this being known as “water breakthrough”. Composition of the produced water will reflect an increase in the proportion of injected water. As oilfields age, water becomes the predominant fluid to be treated.

SUGGESTED CITATION

High Impact PVC/Polycarbonate Alloy Compositions, E. J. Termine, D. J. Honkomp, and N.A. Favstritsky, United States Patent No. 5,219,936.
Available at: http://termine.com/archives/488

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to impact and thermal distortion resistant thermoplastic resin compositions, and more particularly relates to impact-modified polyvinyl chloride/polycarbonate alloy compositions.

2. Description of the Prior Art

Polyvinylchloride (PVC) is a high volume, relatively inexpensive polymer. However, the use of PVC is often limited because it lacks properties required for many service applications. Efforts to develop PVC blends or alloys with other materials which meet the demands of commercial service applications have therefore continued.

For example, PVC alone lacks the dimensional stability under heat required for many service applications. To address this problem, it is known to alloy PVC with polycarbonate to form an alloy composition having dimensional stability under heat surpassing that of PVC alone. For example, Abdrakhmanova et al., SU 84-3788283, 31 Aug. 1984, describe a mixture of 100 parts polyvinyl chloride and 1-8 parts oligomeric bisphenol A polycarbonate. PVC/polycarbonate alloys, however, often lack acceptable impact strength. Efforts have therefore been made to discover impact modifiers that can be added to PVC/polycarbonate alloys to make an overall composition having both acceptable impact strength and dimensional stability under heat.

In this connection, U.S. Pat. No. 3,882,192 issued to Elghani et al. in 1975 describes molding compositions consisting of 5-95 parts by weight of a polycarbonate, 5-95 parts by weight of a vinyl chloride polymer, and 5-95 parts by weight of an acrylonitrile butadiene styrene copolymer or a styrene/maleic anhydride copolymer or an ethylene-vinyl acetate copolymer.

On the other hand, U.S. Pat. No. 4,680,343 issued to Lee in 1987 describes chlorinated polyvinyl chloride (CPVC) alloys containing aromatic polycarbonates, ethylene-based functional polymers and optionally an impact modifier. The Lee patent notes that CPVC and PVC are different materials and that PVC prior art is not analogous to patentability issues relating to CPVC since PVC processes easily and CPVC does not, since CPVC has heat resistance but PVC does not, and furthermore, since CPVC has a high melt viscosity but PVC does not.

Despite these and other efforts, the need continues for PVC/polycarbonate alloy compositions having high impact properties. Efforts to find such compositions have been frustrated because the effects of differing impact modifiers on PVC/polycarbonate blends vary greatly, and it is thus difficult to discover impact modifiers which provide overall alloys having high impact and other desirable properties.

The applicant’s invention now addresses this need and provides impact and thermal distortion resistant PVC alloys having other advantageous properties as well.

SUMMARY OF THE INVENTION

One preferred embodiment of the invention provides a rigid thermoplastic resin composition having high impact strength and resistance to thermal distortion. The thermoplastic resin composition includes an alloy of a vinyl chloride resin and a polycarbonate (hereinafter sometimes referred to as a “vinyl chloride resin/polycarbonate alloy”). The thermoplastic composition further includes at least about 3 parts by weight of a butadiene-modified acrylic (“BMA”) impact modifier per 100 parts by weight of the vinyl chloride resin/polycarbonate alloy. This composition demonstrates highly advantageous physical and chemical properties, including for instance superior impact strength as can be measured by the Gardner impact test, as well as high resistance to heat distortion.

As another feature of the invention, a particularly preferred thermoplastic resin composition includes both butadiene-modified acrylic and an ethylene-vinyl acetate (EVA) copolymer. It has been discovered that using these two impact modifiers together can provide synergistic results in which high impact properties are retained while the composition has greater ductility than similar compositions modified only with the individual impact modifiers.

Still another preferred embodiment of the invention provides a method for preparing a thermoplastic resin composition having high impact strength and resistance to heat distortion. This method includes the step of incorporating into a vinyl chloride resin/polycarbonate alloy an effective amount of butadiene-modified acrylic polymer to increase the impact strength of the alloy.

Additional aspects, features and preferred embodiments of the invention will be apparent from the following description.
__________________________________________________________________________________________________

Download Full Text

SUGGESTED CITATION

Flame Retardant Polypropylene Molding Compositions, E. J. Termine, R. W. Atwell, D. L. Collison, N. A. Favstritsky, and H. A. Hodgen, United States Patent No. 5,124,404.
Available at: http://termine.com/archives/485

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention resides in the field of flame retardant polymers. More particularly, it relates to flame retardant polymer molding compositions which include graft copolymers of isotactic or syndiotactic polypropylene and brominated vinyl aromatics such as brominated styrenes.

2. Description of the Prior Art

By way of background, polypropylene has proven to be one of the most useful and versatile polymers. Its physical properties make it ideal for many applications including molded articles, spun fibers, hot melt adhesives and many others. These properties include, for instance, good surface appearance and solvent and stain resistance, and low moisture absorption. However, polypropylene does not possess adequate flame retardancy for certain applications. In view of its other desirable physical properties, it has naturally been a matter of great interest to provide polypropylene compositions with greater flame retardancy.

Improvement of flame retardancy has relied on modifications to polypropylene, or on additives for the polypropylene, but disadvantages have been associated with both approaches. Although a vast number of modified polypropylene compositions have been described or theorized in the prior art, few if any suitable flame retardant polypropylene derivatives have been identified. Similarly, numerous additives for increasing the flame retardancy of polypropylene have been studied and some are commercially available. Nonetheless, there is at present no commercially available flame retardant additive for polypropylene which provides adequate retention of polypropylene’s physical properties, and demonstrates high thermal stability, non-migration of additive to the surface, and absence of solids at processing temperatures. The present invention contemplates a modification of polypropylene which yields a composition that retains the desirable physical properties of polypropylene, and avoids the disadvantages of alternate approaches.

In particular, the modified polypropylene of the invention avoids the frequently encountered migration or “bloom” of inert additive-type flame retardants to the surface of molded articles. Such bloom leads to unsightly surface discoloration on articles molded from the polypropylene and thereby effectively limits the amount of additive which can be used. Further, these inert additives frequently remain solid at Processing temperatures, and can damage or foul processing equipment. For example, inert additives remaining solid at processing temperatures are known to cause problems by clogging spinnerettes used in equipment for producing spun fibers. This type of equipment fouling not only reduces the efficiency of processing but can also necessitate the costly refurbishment or premature replacement of equipment.

The applicants’ preferred modified polypropylenes also avoid many other problems encountered in the prior art by having only low levels of unreacted styrene monomer, typically less than 1% by weight. For example, by this aspect the applicants’ invention provides a vehicle to avoid monomer juicing problems known to occur in prior art graft modified compositions. It is also significant that the compositions of the present invention can be efficiently processed without the release of excessive volatile monomer into the surrounding environment, which can be hazardous to those working with or near the materials. The prior art has failed to appreciate these substantial advantages of the compositions of the present invention.

As noted above, known flame retardant additives for polypropylene have recognized drawbacks. One such additive is hydrated alumina, which retards flame by releasing water under fire conditions. However, high loadings of hydrated alumina are necessary to give desired efficacy, and this results in poor physical properties of the polypropylene and articles molded therefrom. Among other defects, this results in undesirable changes in physical properties such as excessive stiffness, a reduction in tensile elongation, an increase in specific gravity, and a loss of “living hinge” capability.

Certain other available additives remain solid at normal polypropylene processing temperatures and thus complicate processing. Such additives include, for example, a bisimide-containing aliphatic bromine additive known as BN-451 from Ethyl Corp. of Sayreville, New Jersey, and a ring brominated polystyrene additive known as Pyro-Chek 68PB from Ferro Corp. of Cleveland, Ohio. The latter use of ring brominated polystyrene as an additive to polypropylene, rather than as a graft onto polypropylene, is a particularly clear demonstration of the failure of the prior art to recognize the present invention. Other available additives, such as decabromodiphenyl oxide, not only remain solid at processing temperatures but also are known to rise or “bloom” to the surface of molded articles. In U.S. Pat. No. 3,474,067, issued to Praetzel et al. on Oct. 21, 1969, there is described the use of ungrafted halogenated polystyrene homopolymer as a flame retardant additive for polyolefins in general, including polypropylene.

Aside from these inert additives, reports exist in the literature of attempts to chemically bond or graft flame retardants to polypropylene. To the applicants’ knowledge, none of these techniques has been commercialized. For instance, M. Hartmann, et al., Z. Chem., 20(4), 146-7 (1980), report preparing graft copolymers of atactic polypropylene and four respective vinylphosphonic acid derivatives. Two of the four copolymers prepared were reported as self extinguishing when containing greater than 3% by weight phosphorous. P. Citovicky et al., Thermochim. Acta.. 93, 171-4 (1985), disclose a two-step procedure in which glycidyl methacrylate was grafted to isotactic polypropylene followed by reaction with various flame retardants including bromoacetic acid, 3,3′,5,5′-tetrabromo-2,2′-dihydroxybiphenyl, dichloroacetic acid, or phenyldihydrogen phosphate. The copolymer reacted with phenyldihydrogen phosphate gave the highest limiting oxygen index value and was also reported the most thermally stable. In general, this technique is not particularly advantageous since it requires two steps and the flame retardant must be a functionalized molecule capable of reaction with an epoxide.

B. J. Hill et al., Comm. Eur. Communities [ReP.]EUR, EUR 6718 (1980), report irradiation grafting of bis(2-chloroethyl)vinylphosphonate to polyester and polypropylene fabrics to render them self-extinguishing. The authors report that the bis(2-chloroethyl)vinylphosphonate had poor reactivity toward the fabrics. Comonomers were therefore required which in some instances diminished flame retardancy and/or stiffened the fabrics.

K. Nakatsuka et al., Japan JP 44/3965 (Feb. 19, 1969), report air oxidizing polypropylene at elevated temperatures to introduce peroxy groups to the polymer followed by graft polymerization with CH.sub.2 CClCO.sub.2 Me. The product was reported to be self-extinguishing.

Outside of the field of flame retardancy, various modifications to polyolefins have been proposed. For example, U.S. Pat. No. 4,179,401, issued to Garnett et al. in 1979, relates to a process for producing a heterogenous catalyst for the hydrogenation, hydroformylation, isomerization, cracking or dehydrogenation cf organic molecules. The Garnett process comprises the steps of radiation grafting a monomer having an alpha- unsaturated bond to a metal or an organic polymer and complexing a nitrogen, halogen, or phosphorous containing group to the monomer. The Garnett et al. patent lists many possible polymer/monomer combinations. Identified polymer substrates included polyvinyl compounds, polyolefins, polyvinylidenes, polysiloxanes, polydienes, polyethers, polyimides, polysulphones, polyesters, polyamides, polyurethanes, polycarbonates and polyureas. Listed as possible monomers for use in the described process were p-nitrostyrene, p-amino styrene, p-chlorostyrene, vinyldiphenylphosphine, cis-bis (1,2-diphenylphosphino) ethylene, triallylphosphine, divinylphenylphosphine and many more.

Similarly, U.S. Pat. No. 3,177,270, issued to Jones et al. in 1965, describes a method for modifying polyethylene and other substrates for the purpose of improving tensile strength, elongation and/or flexural modulus. The Jones et al. patent specifically described the preparation of ethylene polymer modified with styrene, a styrene/acrylonitrile mixture, dichlorostyrene or a mixture of isomeric vinyltoluenes. The Jones et al. patent additionally lists other possible polymeric substrates for use in the described method as including polypropylene, polyisobutylene, polybutene, and copolymers of ethylene and propylene, ethylene and butene, ethylene and styrene, ethylene and vinyl acetate, and ethylene and methyl methacrylate. Possible graft monomers are listed as including styrene, vinyltoluene, vinylxylene, ethylvinylbenzene, isopropyl styrene, para-tert-butyl styrene, dichlorostyrene, bromostyrene, fluorostyrene, or mixtures thereof with acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, methyl methacrylate or maleic anhydride.

In U.S. Pat. No. 4,279,808, issued to Hornbaker et al. on Jul. 21, 1981, there is described a method for the preparation of polybromostyrene resin by the addition polymerization of nuclear brominated styrene. The Hornbaker et al. patent is limited to the addition polymerization of bromostyrene in the presence of specified rubbery polymers, namely SBR rubber (butadiene-styrene copolymers), EPR rubber (ethylenepropylene copolymers), EPDM rubber (i.e. terpolymers of ethylene, propylene and a diene monomer), polyisoprene rubber (e.g. cis 1,4 polyisoprene and trans-1,4-polyisoprene), Neoprene (i.e. polymers and copolymers of 2-chloro-1,3-butadiene), cis-1,4-polybutadiene, and polybutadienes having mixed structures (e.g. cis-1,4; trans-1,4 and 1,2 structures), with the polybutadienes being particularly preferred.

As is evident from the foregoing, past efforts to provide a polypropylene composition with improved flame retardancy have not been fully satisfactory. Available inert flameproofing additives have exhibited drawbacks such as bloom and interference with desired physical properties. Additionally, polypropylene materials have not been provided with grafted fire retardants which perform as well as the present inventive compositions. Accordingly, there has remained a need for fire retardant polypropylene compositions demonstrating good physical properties, and the applicants’ invention addresses this need.

SUMMARY OF THE INVENTION

Accordingly, a first preferred embodiment of this invention provides a flame retardant graft copolymer composition comprising: ##STR3## in which n is an integer >1, P is a moldable polypropylene, and S is a side chain grafted to the polypropylene and having brominated monomeric units of the formula: ##STR4## wherein x=1 to 4, R.sub.1 is H or CH.sub.3, and R.sub.2 is H or a C.sub.1-4 lower alkyl group. In an alternate embodiment, the composition additionally includes a homopolymer of the brominated monomeric units.

Another preferred embodiment of this invention provides a flame retardant polymer composition comprising a blend of (i) moldable polypropylene, and (ii) a polymer composition including a graft copolymer according to the first embodiment above and constituted about 10% to about 60% bromine by weight. Such a blend can be prepared by diluting or “letting down” the bromine-concentrated polymer composition (ii) with a desired amount of polypropylene (i). After let down, the blend preferably comprises about 1% to about 20% bromine by weight of the blend.

It is an object of this invention is to provide flame retardant polypropylene-based molding polymer compositions which retain a desirable balance of physical properties, and which do not require flame retardant synergists.

Further objects include the provision of a flame retardant polypropylene molding composition which is characterized by high thermal stability, an absence of abrasive solids, a glossy surface appearance, an inherent whiteness, living hinge properties, and an immunity to water extraction.

Additional objects and advantages will be apparent from the description which follows.
_________________________________________________________________________________________________

Download Full Text

SUGGESTED CITATION

Flame Retardant Graft Copolymers of Polypropylene, E. J. Termine, R. W. Atwell and N. A. Favstritsky, United States Patent No. 5,077,337.
Available at http://termine.com/archives/466

BACKGROUND OF THE INVENTION

This invention resides in the field of flame retardant polymers. More particularly, it relates to flame retardant polymer compositions which include graft copolymers of polypropylene and brominated vinyl aromatics such as brominated styrenes, and to methods for making these compositions.

By way of background, polypropylene has proven to be one of the most useful and versatile polymers. Its physical properties make it ideal for many applications including molded articles, spun fibers, hot melt adhesives and many others. These properties include, for instance, good solvent resistance, surface appearance and stain resistance, and low moisture absorption. However, polypropylene does not possess adequate flame retardancy for certain applications. In view of its other desirable physical properties, it has naturally been a matter of great interest to provide polypropylene compositions having greater flame retardancy.

Improvement of flame retardancy has relied on modifications to polypropylene, or on additives for the polypropylene, but disadvantages have been associated with both approaches. Although a vast number of modified polypropylene compositions have been described or theorized in the prior art, few if any suitable flame retardant polypropylene derivatives have been identified. Similarly, numerous additives for increasing the flame retardancy of polypropylene have been studied and some are commercially available. Nonetheless, there is at present no commercially available flame retardant additive for polypropylene which provides adequate retention of polypropylene’s physical properties, and demonstrates high thermal stability, non-migration of additive to the surface, and absence of solids at processing temperatures. The present invention contemplates a modification of polypropylene which yields a composition that retains the desirable physical properties of polypropylene, and avoids the disadvantages of alternate approaches.

In particular, the modified polypropylene of the invention avoids the frequently encountered migration or “bloom” of inert additive-type flame retardants to the surface of molded articles. Such bloom leads to unsightly surface discoloration on articles molded from the polypropylene and thereby effectively limits the amount of additive which can be used. Further, these inert additives frequently remain solid at processing temperatures, which can damage or foul processing equipment. For example, inert additives remaining solid at processing temperatures are known to cause problems by clogging spinnerettes used in equipment for producing spun fibers. This type of equipment fouling not only reduces the efficiency of processing but can also necessitate the costly refurbishment or premature replacement of equipment.

The applicants’ preferred modified polypropylenes also avoid many other problems encountered in the prior art by having only low levels of unreacted styrene monomer, typically less than 1% by weight. For example, by this aspect the applicants’ invention provides a vehicle to avoid monomer juicing problems known to occur in prior art graft modified compositions. It is also significant that the compositions of the present invention can be efficiently processed without the release of excessive volatile monomer into the surrounding environment, which can be hazardous to those working with or near the materials. The prior art has failed to appreciate these substantial advantages of the compositions of the present invention.

As noted above, known flame retardant additives for polypropylene have recognized drawbacks. One such additive is hydrated alumina, which retards flame by releasing water under fire conditions. However, high loadings of hydrated alumina are necessary to give desired efficacy, and this results in very poor physical properties of the polypropylene and articles molded therefrom.

Certain other available additives remain solid at normal polypropylene processing temperatures and thus complicate processing. Such additives include, for example, a bisimide-containing aliphatic bromine additive known as BN-451 from Ethyl Corp. of Sayreville, N.J., and a ring brominated polystyrene additive known as Pyro-Chek 68PB from Ferro Corp. of Cleveland, Ohio. The latter use of ring brominated polystyrene as an additive to polypropylene, rather than as a graft onto polypropylene, is a particularly clear demonstration of the failure of the prior art to recognize the present invention. Other available additives, such as decabromodiphenyl oxide, not only remain solid at processing temperatures but also are known to rise or “bloom” to the surface of molded articles.

Aside from these inert additives, reports exist in the literature of attempts to chemically bond or graft flame retardants to polypropylene. To the applicants’ knowledge, none of these techniques has been commercialized. For instance, M. Hartmann, et al., Z. Chem., 20(4), 146-7 (1980), report preparing graft copolymers of atactic polypropylene and four respective vinylphosphonic acid derivatives. Two of the four copolymers prepared were reported as self extinguishing when containing greater than 3% by weight phosphorous.

P. Citovicky et al., Thermochim. Acta., 93, 171-4 (1985), disclose a two-step procedure in which glycidyl methacrylate was grafted to isotactic polypropylene followed by reaction with various flame retardants including bromoacetic acid, 3,3′,5,5′-tetrabromo-2,2′-dihydroxybiphenyl, dichloroacetic acid, or phenyldihydrogen phosphate. The copolymer reacted with Ph dihydrogen phosphate gave the highest limiting oxygen index value and was also reported the most thermally stable. In general, this technique is not particularly advantageous since it requires two steps and the flame retardant must be a functionalized molecule capable of reaction with an epoxide.

B. J. Hill et al., Comm. Eur. Communities [Rep.] EUR, EUR 6718 (1980), report irradiation grafting of bis(2-chloroethyl)vinylphosphonate to polyester and polypropylene fabrics to render them self-extinguishing. The authors report that the bis(2-chloroethyl)vinylphosphonate had poor reactivity toward the fabrics. Comonomers were therefore required which in some instances diminished flame retardancy and/or stiffened the fabrics.

K. Nakatsuka et al., Japan JP 44/3965 (Feb. 19, 1969), report air oxidizing polypropylene at elevated temperatures to introduce peroxy groups to the polymer followed by graft polymerization with CH.sub.2 CClCO.sub.2 Me. The product was reported to be self-extinguishing.

Outside of the field of flame retardancy, various modifications to polyolefins have been proposed. For example, U.S. Pat. No. 4,179,401, issued to Garnett et al. in 1979, relates to a process for producing a heterogenous catalyst for the hydrogenation, hydroformylation, isomerization, cracking or dehydrogenation of organic molecules. The Garnett process comprises the steps of radiation grafting a monomer having an alpha- unsaturated bond to a metal or an organic polymer and complexing a nitrogen, halogen, or phosphorous containing group to the monomer. The Garnett et al. patent lists many possible polymer/monomer combinations. Identified polymer substrates included polyvinyl compounds, polyolefins, polyvinylidenes, polysiloxanes, polydienes, polyethers, polyimides, polysulphones, polyesters, polyamides, polyurethanes, polycarbonates and polyureas. Listed as possible monomers for use in the described process were p-nitrostyrene, p-amino styrene, p-chlorostyrene, vinyldiphenylphosphine, cis-bis (1,2-diphenylphosphino) ethylene, triallylphosphine, divinylphenylphosphine and many more.

Similarly, U.S. Pat. No. 3,177,270, issued to Jones et al. in 1965, describes a method for modifying polyethylene and other substrates for the purpose of improving tensile strength, elongation and/or flexural modulus. The Jones et al. patent specifically described the preparation of ethylene polymer modified with styrene, a styrene/acrylonitrile mixture, dichlorostyrene or a mixture of isomeric vinyltoluenes. The Jones et al. patent additionally lists other possible polymeric substrates for use in the described method as including polypropylene, polyisobutylene, polybutene, and copolymers of ethylene and propylene, ethylene and butene, ethylene and styrene, ethylene and vinyl acetate, and ethylene and methyl methacrylate. Possible graft monomers are listed as including styrene, vinyltoluene, vinylxylene, ethylvinylbenzene, isopropyl styrene, para-tert-butyl styrene, dichlorostyrene, bromostyrene, fluorostyrene, or mixtures thereof with acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile, methyl methacrylate or maleic anhydride.

As is evident from the foregoing, past efforts to provide a polypropylene composition with improved flame retardancy have not been fully satisfactory. Available inert flameproofing additives have exhibited drawbacks such as bloom and interference with desired physical properties. Additionally, polypropylene materials have not been provided with grafted fire retardants which perform as well as the present inventive compositions. Accordingly, there has remained a need for fire retardant polypropylene compositions demonstrating good physical properties, and the applicants’ invention addresses this need.

SUMMARY OF THE INVENTION

Accordingly, a first preferred embodiment of this invention provides a flame retardant graft copolymer composition comprising: ##STR3## in which n is an integer >1, P is polypropylene, and S is a side chain grafted to the polypropylene and having brominated monomeric units of the formula: ##STR4## wherein x=1 to 4, R.sub.1 is H or CH.sub.3, and R.sub.2 is H or a C.sub.1-4 lower alkyl group. In an alternate embodiment, the composition additionally includes a homopolymer of the brominated monomeric units.

Another preferred embodiment of this invention provides a flame retardant polymer composition comprising a blend of (i) polypropylene, and (ii) a polymer composition including a graft copolymer according to the first embodiment above and constituted about 10% to about 60% bromine by weight. Such a blend can be prepared by diluting or “letting down” the bromine-concentrated polymer composition (ii) with a desired amount of polypropylene. After let down, the blend preferably comprises about 1% to about 20% bromine by weight of the blend.

Another preferred embodiment of this invention provides a method for producing a flame retardant polymer composition which comprises the step of graft polymerizing polypropylene with a monomer having the formula: ##STR5## wherein x=1 to 4, R.sub.1 is H or CH.sub.3, and R.sub.2 is H or a C.sub.1-4 lower alkyl group. The invention provides a flame retarding amount of bromine in the graft polymerization product.

One object of this invention is to provide flame retardant polypropylene-based polymer compositions.

Another object of this invention is to provide a method for Producing flame retardant polypropylene-based polymer compositions.

Additional objects and advantages will be apparent from reading the description which follows.
________________________________________________________________________________________________

Download Full Text

SUGGESTED CITATION

Low Smoke Intumescent Flame Retardant For Thermoset Composites, E. J. Termine and K. G. Taylor, Reinforced Plastics, 34, 28 (1990).
Available at: http://termine.com/archives/457

ABSTRACT

The use of a new low smoke intumescent flame retardant for thermoset composites is described. This material, CN-1197 flame retardant, is a phosphorous-based compound which is very effective in promoting an intumescent char on the polymer surface during flammability tests.

CN-1197 flame retardant allows fabrication of composites with excellent physical property retention. The utility of CN-1197 is broad, especially in unsatuturated polyesters, vinyl esters and epoxies.

Composites formulated with CN-1197 received very low smoke values. For example, Class I reinforced polyester systems with smoke development values less than 100 are achieved with a 10-20 weight percent loading.

This paper reports recent studies to broaden the utility of CN-1197 in thermoset applications. Specifically, formulation information is presented, covering flammability and physical property performance, and processing consideration.
________________________________________________________________________________________________

Download Full Text