Modified zeolites and methods of making thereof

The present invention relates to zeolites and the process for forming such zeolites. In addition, the instant invention relates to modified zeolites having a reduced water content while retaining the reactivity toward the acid species. The reduction in the water content is achieved by shock annealing or coating. The modified zeolite is useful as a stabilizer for halogen containing polymers.

FIELD OF INVENTION
 This invention relates to small particle size zeolites which have a small
 mean particle size, and narrow particle size distribution. In addition,
 this invention relates to modified zeolites that have a reduced water
 content. The modified zeolites can be formed from large particle size
 zeolites having a narrow particle size distribution as well as small
 particle size zeolites having a narrow particle size distribution. These
 modified zeolites which retain reactivity toward acid species such as HCl
 yet exhibit minimal water absorption are particularly useful as
 stabilizers in halogen containing polymers. Furthermore, the invention
 relates to a method of preparing the small particle size zeolites as well
 as modified zeolites.
 BACKGROUND OF THE INVENTION
 Zeolites are highly crystalline materials containing tetra-coordinated
 aluminum atoms, each associated through four oxygen atoms with adjacent
 silicon atoms in the crystalline matrix. These zeolites tend to have large
 particle sizes. For example, commercially available zeolite 4A has a
 particle size of about 3 to about 6 microns. Furthermore, due to the
 microporous structure of the zeolite, the material absorbs moisture.
 Therefore, often times the zeolites are used as adsorbents. Additionally,
 zeolites are used as catalysts. Various processes have been used to form
 zeolites.
 For example, U.S. Pat. No. 3,528,615 describes a method of reducing the
 particle size of crystalline zeolites. In this process, the zeolite is
 heated to an elevated temperature. This temperature is below the
 temperature at which the loss of crystallinity occurs. The heated zeolite
 is then quenched in a liquid medium which is maintained below the elevated
 temperature. The thermal shock fractures the zeolite to produce smaller
 crystals without a significant reduction in the crystallinity.
 Another example of a prior art process for zeolites is disclosed in U.S.
 Pat. No. 4,581,214. This patent discloses a shock calcination method.
 According to this method, the zeolite is precalcined at a relatively low
 temperature. The zeolite is then heated to a relatively high calcination
 temperature for a relatively short period of time because prolonged
 exposure of the zeolite to the high temperature would destroy the original
 structure of the zeolite. The patentee notes that it is very important to
 prevent mineralization reactions from occurring by this rapid heating
 steps. The zeolite is then rapidly cooled. The process described in U.S.
 Pat. No. 4,581,214 alters the zeolite surface acidity. This zeolite is
 then used as a catalyst.
 Zeolites are effective acid scavengers for halogen containing polymers and
 enhance the thermal stability of halogen containing polymers. Acid
 scavengers are compounds that react with acids to form a compound that is
 typically chemically inert. However, the use of zeolites as stabilizers or
 acid scavengers in halogen containing polymer compounds has been limited
 for several reasons. First, the zeolites generally have a large particle
 size, generally in the range of about 3 to about 6 microns. The large size
 of the zeolite particles not only causes surface blemishes on the
 finishing of the end product made from such a polymer but also diminishes
 the physical properties of such polymers. Further, outgassing occurs
 frequently with polymers containing zeolites when the polymer is heated
 during processing due to the evolution of water from the zeolite during
 the heating. As a result, there is foaming.
 Halogen containing polymers tend to degrade or deteriorate when processed.
 Generally, the difference between the processing temperature and the
 degradation temperature is very small. Therefore, there is a risk that
 during the processing of these halogen containing polymers, that the
 polymer will degrade. When such polymers degrade, it is believed that a
 halide acid is generated by the polymer. This acid attacks the components
 of the processing equipment. Also, this acid further catalyzes elimination
 reactions and additional degradation of the polymer.
 Stabilizers have been developed to help deter such degradation. For
 example, organic compounds are commonly used. In some instances, zeolites
 have also been used as stabilizers.
 U.S. Pat. No. 4,000,100 discloses a thermal and light stabilized polyvinyl
 chloride resin. The stabilizer used in the composition comprises an
 unactivated zeolite A molecular sieve or an unactivated naturally
 occurring molecular sieve of essentially the same pore size range as
 zeolite A and a conventional inorganic, organometallic or organic
 stabilizer. The unactivated zeolite molecular sieve has adsorbed water
 molecules. According to the patentee, the combination of the unactivated
 zeolite and the conventional stabilizer produces a compound with allegedly
 improved stability as compared to a compounds produced with either of the
 two stabilizers separately.
 Similarly, U.S. Pat. No. 4,338,226 discloses a process for the
 stabilization of polyvinyl chloride and stabilizer compositions. The
 patent describes admixing sodium aluminosilicate of small particle size
 (preferably, 0.1 to 20 microns), calcium salts of fatty acids, zinc salts
 of fatty acids, partial esters of polyols and fatty acids, thioglycolic
 acid esters of polyols and polyvinyl chloride or copolymer of vinyl
 chloride. An aluminosilicate that can be used is crystalline sodium
 zeolite A. The composition is used for molding mixtures.
 U.S. Pat. No. 4,371,656 describes a metal substituted zeolite for use as a
 stabilizer for halogen containing resins. The stabilizer comprises a
 crystalline aluminosilicate substituted with ions of metallic elements
 belonging to Group II or Group IVA of the Periodic Table for the Group I
 (M) metal ion contained in the aluminosilicate. The stabilizer also must
 contain 10% by weight or less as M.sub.2 O of residual Group I metal ions.
 The stabilizer, zeolite A, according to the patentee claims to have a
 water content of 8% by weight or less. This patent also discloses the use
 of organic substances to cover the voids of the zeolite particles and
 prevent moisture reabsorption.
 Stabilized chloride containing resins are also described in U.S. Pat. No.
 5,004,776. The stabilizer consists essentially of: (a) an overbased
 alkaline earth metal carboxylate or phenolate complex; (b) zeolite; (c)
 calcium hydroxide; and (d) a complex of at least one metal perchlorate
 selected from the group consisting of sodium, magnesium, calcium, and
 barium perchlorates with at least one compound selected from the group
 consisting of polyhydric alcohols and their derivatives. This stabilizer
 apparently prevents the discoloration and deterioration in physical
 properties of the chlorine containing resin resulting from thermal
 degradation when the resin is subject to thermoforming or exposed to a
 high temperature atmosphere for a long period of time.
 Stabilizer compositions for use in halogen containing polymer are also
 described in U.S. Pat. No. 5,216,058. The stabilizer composition comprises
 hydrotalcite and a molecular sieve zeolite. The molecular sieve zeolite
 comprises a Group IA or IIA aluminosilicate.
 Thus, there currently exists a need for an zeolite having a small particle
 size and a narrow particle size distribution. Furthermore, a need exists
 for a modified zeolite having a reduced water content while retaining
 reactivity with acid species. Preferably, the water content is less than
 10 weight percent. The modified zeolite can be comprised a zeolite having
 a mean diameter greater than 1.5 microns with a narrow particle size
 distribution, or a zeolite having a mean particle diameter less than 1.5
 microns and a narrow particle distribution, or a mixture of the two. In
 addition, a need exists for a modified zeolite which maintains its
 stabilizing activity. Moreover, a need exists for a method to form such
 small particle size zeolite and modified zeolite.
 SUMMARY OF THE INVENTION
 The present invention comprises a novel small particle size zeolite. The
 small particle size zeolite has a mean particle diameter in the range of
 about 0.25 to about 1.5 microns and a &lt;90% particle diameter value (90% by
 weight of the particles are of a particle diameter below the range) of
 about 0.30 to about 3.0 microns. Another aspect of the invention is a
 method of preparing such a small particle size zeolite.
 A further aspect of the invention is a modified zeolite. The modified
 zeolite comprises a small particle size zeolite having a narrow particle
 size distribution or a large particle size having a narrow particle size
 distribution or a mixture of the two particles. These particles are then
 either shock annealed, or coated to produce a modified zeolite which is
 reactive toward acid species such as HCl. If used in halogen containing
 compounds, these zeolites improve the process stability of the compound
 without adversely diminishing its physical properties.
 DETAILED DESCRIPTION
 Zeolites are well known. Zeolites comprise basically of a three dimensional
 framework of SiO.sub.4 and AlO.sub.4 tetrahedra. The tetrahedra are
 crosslinked through the sharing of oxygen atoms so that the ratio of
 oxygen atoms to the total of the aluminum and silicon atoms it equal to 2.
 This relationship is expressed as O/(Al+Si)=2. The electrovalence of the
 tetrahedra containing aluminum and silicon is balanced in the crystal by
 the inclusion of a cation. For example, the cation can be an alkali or
 alkaline earth metal ion. The cation can be exchanged for another
 depending upon the final usage of the aluminosilicate zeolite. The spaces
 between the tetrahedra of the aluminosilicate zeolite are usually occupied
 by water. Zeolites can be either natural or synthetic.
 The basic formula for all aluminosilicate zeolites is represented as
 follows:
EQU M.sub.2/n O:[Al.sub.2 O.sub.3 ].sub.x :[SiO.sub.2 ].sub.y :[H.sub.2
 O].sub.z
 wherein M represents a metal, n represents the valence of the metal and X
 and Y and Z vary for each particular aluminosilicate zeolite. Essentially
 it is believed that any aluminosilicate zeolite according to the instant
 invention can be used as a stabilizer in halogen containing compounds,
 provided that the ratio of the silicon to aluminum in such aluminosilicate
 zeolite is less than 3.0 and the aluminosilicate zeolite can be
 incorporated into the halogen containing polymer. Preferably, the ratio of
 the silicon to aluminum in the aluminosilicate zeolite is less than 1.5
 and most preferably the ratio is about 1.0.
 It is further believed that the following zeolites which can be used in the
 instant invention include but are not limited to zeolite A, described in
 U.S. Pat. No. 2,822,243; zeolite X, described in U.S. Pat. No. 2,822,244;
 zeolite Y, described in U.S. Pat. No. 3,130,007; zeolite L, described in
 Belgian Patent No. 575,117; zeolite F, described in U.S. Pat. No.
 2,996,358; zeolite B, described in U.S. Pat. No. 3,008,803; zeolite Q,
 described in U.S. Pat. No. 2,991,151; zeolite M, described in U.S. Pat.
 No. 2,995,423; zeolite H, described in U.S. Pat. No. 3,010,789; zeolite J,
 described in U.S. Pat. No. 3,011,869; and zeolite W, described in U.S.
 Pat. No. 3,102,853.
 The preferred zeolites include alone or in combination with another Group I
 metal hydrated silicates of aluminum incorporating sodium of the type
 Na.sub.2 O.cndot.xAl.sub.2 O.sub.3.cndot.ySiO.sub.2.cndot.zH.sub.2 O.
 These preferred zeolites include zeolites A, X, and Y. The most preferred
 zeolite is zeolite 4A. Zeolite 4A, preferably has the following formula:
EQU M.sub.2/n O:[AlO.sub.2 ].sub.12 :[SiO.sub.2 ].sub.12 :[H.sub.2 O].sub.27
 wherein M is sodium.
 Any method can be used to form such small particle size zeolites provided
 that the mean particle diameter of the zeolite is less than 1.5 microns,
 and the zeolite has a &lt;90% value particle diameter of about 0.30 to about
 3 microns.
 Depending upon the final usage of the small particle size zeolite, it may
 be desirable to incorporate an active metal other than the metal which was
 used to synthesize the small particle size zeolite. This can be
 accomplished by any numerous means such as for example, ion exchange,
 impregnation, coprecipitation, cogelation. Alternatively, the metal may be
 added by synthesis.
 A relatively simple process is used in the preparation of the small
 particle size zeolite of the instant invention. First, the zeolite is
 synthesized. The exact synthesis will vary dependent upon the specific
 zeolite being used; this synthesis is well within the skill of one of
 ordinary skill in the art. Generally, however, a mixture of the aqueous
 solution of the materials which can be represented as mixtures of oxides,
 Na.sub.2 O; Al.sub.2 O.sub.3 ; SiO.sub.2 and H.sub.2 O are reacted at a
 temperature in the range of about 50.degree. C. to about 100.degree. C.
 for a period of about 45 minutes to about 2000 minutes. Alternatively, the
 mixture of the reactants are allowed to age from about 0.1 to 48 hours at
 ambient conditions prior to the crystallization step. Preferably, the
 temperature of the reaction is in the range of about 50.degree. C. to
 about 80.degree. C. and the reaction is carried out for about 60 to 420
 minutes. Most preferably, the temperature is 60.degree. C. to 70.degree.
 C. with a reaction of time of 90 to 300 minutes. The result of this
 reaction is a zeolite having a mean particle size in the range of about
 0.25 to 1.5 microns. The &lt;90% particle size value is in the range of 0.30
 to 3.0 microns.
 After the small particle size zeolite is formed, it is washed. Preferably,
 the small particle size zeolite is washed in deionized water. For example,
 the small particle size zeolite may be washed four times with deionized
 water. The washed small particle size zeolite is then filtered and dried
 at 100-200.degree. C. Any means can be used to dry the small particle size
 zeolite, including air drying. After being dried, the small particles are
 then dehydrated at about 250 to about 500.degree. C. Any means available
 to dehydrate the small particle sized zeolite can be used, including but
 not limited to furnace dehydration. It is believed that the small particle
 sized zeolite has better reactivity when incorporated into halogen
 containing polymers if it is dried. If furnace dehydrated, any suitable
 furnace can be used provided that the desired temperature can be reached.
 Generally if furnace dehydrated, the zeolite is heated to the range of
 about 250 to 500.degree. C. for about 2 to 6 hours. Alternatively, the
 small particle size zeolite can be dehydrated in vacuo at approximately
 200.degree. C. for about 2 to about 6 hours.
 The small particle size zeolites formed according to the instant invention
 can be used in any application in which small particle size zeolites are
 desired. For example, these small particle size zeolites can be used as
 adsorbents, absorbents, or thickening agents. Additionally, the small
 particle size zeolites can be used for enhancing the thermal stability of
 halogenated polymers, while maintaining the desired physical properties of
 the polymers.
 In another embodiment of the instant invention, zeolite particles are
 modified. Modified zeolite particles have a water content of less than ten
 weight percent. The particles can be modified by chemically altering the
 surface of the zeolite particles or by shock annealing the zeolite
 particles or by coating the zeolite particles, or a combination of shock
 annealing and coating.
 The zeolite particles used to form the modified zeolite particles can be
 either small size zeolite particles having a narrow particle size
 distribution or large zeolite particles having a narrow particle size
 distribution. For purposes of the modified zeolite particles, small
 particle zeolites are those having a mean particle diameter in the range
 of about 0.25 to about 1.5 microns and a &lt;90% particle diameter value in
 the range of about 0.30 to about 3.0 microns. The small size zeolite
 particles can be formed by the process described above or any other
 process provided that the desired size and distribution are obtained. Most
 preferably, the small size zeolite particles are formed by the above
 process. Likewise, for the purposes of large particle size zeolites to be
 used in the modified zeolite, these particles have a mean particles size
 greater than or equal to 1.5 microns and a distribution of about 90%
 within the limits represented by 1/4 times the median at the lower limit
 and 2 times the median at the upper limit.
 Furthermore, these modified zeolites if added to a halogen containing
 compound should impart process stability to the compound without adversely
 diminishing its physical properties. The modification prevents the zeolite
 particles from absorbing water but still allows the zeolite particles to
 react with the acid released upon the deterioration or degradation of the
 halogen containing polymer when processed.
 If coating is the method used for the modification of the zeolite
 particles, an organic, inorganic or low molecular weight (&lt;10,000) coating
 or coating mixture can be used provided that it has the following
 characteristics. First, in the case of inorganic coatings, they cannot be
 redox active; namely, the composition should have its d shell filled.
 Second, the coating cannot be water soluble or water permeable. Third, the
 coating should be reactive or permeable to the halogen acid. Fourth, the
 coating should not be a Lewis Acid. Preferably, the coating used is
 miscible with the halogen containing polymer. Examples of suitable
 coatings include oxides such as magnesium oxide, paraffin waxes, low
 molecular weight organic matrices such as calcium stearate, high molecular
 weight matrices such as siloxanes, and acrylic polymers such as
 methacrylate polymers. Preferably the coating is either dibutyl tin
 thioglycote or polydimethylsiloxane. A commercially available dibutyl tin
 thioglycolate is Mark 292 from Witco Chemical. A commercially available
 polydimethylsiloxane is SF100, available from GE Plastics.
 The coating can be prepared in situ during the formation of the zeolite
 particles or applied to the zeolite particles in a separate step. If
 applied in a separate step, care should be taken to ensure the uniform
 application of the coating as well as to avoid clumping. Furthermore, the
 coating cannot be too thick or too thin, therefore, a balance must be
 obtained so as to ensure low water absorption but retain activity of the
 zeolite particles as acid scavenger.
 Alternatively, the zeolite particles can be modified by shock annealing the
 particles. With the use of a shock annealing process for the zeolite
 particles, a phase transformation occurs at the outer surface of the
 zeolite particle shell. It is believed that the phase transformation
 causes the collapse of the zeolite structure at the outer surface. The
 shock annealing occurs at a temperature above the phase transformation
 temperature of the zeolites followed by rapid cooling. The shock annealing
 is carried out for the appropriate time to cause the outer surface of the
 particles to collapse. Exposure time to this temperature above the phase
 transformation temperature is however limited to minimize the bulk
 absorption of thermal energy and to limit the phase transformation to the
 outer surface of the particles. The temperature at which the zeolite is
 heated during the shock annealing process is dependent upon the particular
 zeolite being shock annealed. The temperature as well as the time to shock
 anneal is well within the skill of one of ordinary skill in the art.
 For example, in one approach to shock annealing, the zeolite particles are
 then placed in a furnace during the shock annealing step. Preferably, the
 particles are placed in a preheated crucible which can be made from
 quartz, high temperature steels or aluminum oxide. The crucible with the
 particles is returned to a muffle furnace. Any furnace can be used so long
 as it reaches the desired temperature. In the most preferred embodiment,
 an aluminum oxide crucible containing small particle size zeolites is
 preheated to approximately 700 to 1200.degree. C. prior to the addition of
 a small particle size zeolite.
 Once the zeolite is added, it is heated from about 1 to about 30 minutes in
 the temperature range of about 700 to 1200.degree. C. After the particles
 are heated, they are rapidly cooled. Any cooling means can be used so long
 as the temperature is cooled below the phase transformation temperature in
 a matter of seconds, for example, about 600.degree. C. for zeolite 4A. The
 particles can be cooled by air, water, carbon dioxide or liquid nitrogen.
 As a result of this process, a modified zeolite is formed.
 The modified zeolite can be used in any application in which zeolites which
 are nonhygroscopic yet reactive towards acids are desired. For example,
 the particles can be used as stabilizers for halogen containing polymers,
 and acid scavenger for polyolefins. The modification prevents the
 aluminosilicate zeolites from absorbing water while still allowing the
 particles to react with the acid released upon deterioration or
 degradation of the halogen containing polymer. If chlorinated polyvinyl
 chloride is the halogen containing polymer, preferably the water content
 of the modified aluminosilicate zeolite is less than 8 weight percent. The
 zeolites formed according to the instant invention maintain their
 stabilizing activity in halogen containing compounds.

The following non-limiting examples serve to further illustrate the present
 invention in greater detail.
 EXAMPLE I
 A zeolite 4A powder was synthesized by individually preparing the following
 solutions: a sodium silicate solution; a sodium aluminate solution; and a
 sodium hydroxide solution.
 The sodium silicate solution was prepared by dissolving 255.6 grams of
 Na.sub.2 SiO.sub.3.cndot.9H.sub.2 O in 650 grams of water. The sodium
 aluminate solution was prepared by dissolving 270.0 grams of NaAlO.sub.2
 in 320 grams of water wherein the sodium hydroxide solution was prepared
 by adding 500 grams of NaOH in 650 grams of water. An additional solution
 of 10.0 grams of ZnCl.sub.2 and 90.0 grams of water was also prepared. All
 solutions were maintained at approximately 55.degree. C. after all solids
 were dissolved in solution. The sodium hydroxide solution was then added
 to the sodium aluminate solution while stirring. The resulting sodium
 aluminate/sodium hydroxide solution was added concurrently with the zinc
 chloride solution to the sodium silicate solution, again while stirring.
 The reaction temperature was maintained at 60.degree. C. for 2 hours. The
 solution was then filtered and rinsed.
 The zeolite A powder had a mean particle diameter of 0.9 .mu.m and &lt;90%
 value of 1.8 .mu.m as determined using a Coulter LS Particle Size
 Analyzer.
 A sample dehydrated at 350.degree. C. exhibited a weight gain of 22% after
 2 days of exposure to ambient conditions. Generally, commercial zeolite 4A
 will pick up moisture in the range of about 18 to about 22 weight percent
 within 48 hours.
 The Dynamic Thermal Stability (DTS) measured according to ASTM D 2532 of a
 TempRite.RTM. 3104 CPVC compound (commercially available from The
 B.F.Goodrich Company; TempRite is a registered trademark of The
 B.F.Goodrich Co.) was evaluated with and without the above zeolite A
 described above using a Brabender torque rheometer set at a 208.degree. C.
 bowl temperature, 35 rpm and a 70 gram loading. The DTS time of the
 TempRite.RTM. 3104 CPVC control was 13 minutes. With the addition of 3
 parts per hundred resin (phr) of the zeolite 4A prepared according to
 Example I to the TempRite.RTM. 3104 compound, the DTS time of the compound
 was increased to 36 minutes. This example illustrates a 157% increase over
 the control value. The DTS increase is defined as (DTS.sub.zeolite
 containing -DTS.sub.control (no zeolite) /DTS.sub.control.times.100%). A
 longer DTS time is indicative of a compound with enhanced stability.
 EXAMPLE II
 A 20.0 gram portion of a dehydrated zeolite prepared according to Example I
 was calcined by gradually heating to 840.degree. C. for 1 hour and
 gradually cooled to room temperature under vacuum. The resulting material
 exhibited virtually no weight gain due to water uptake upon exposure to
 ambient conditions for 500 hours. The DTS time of the TempRite.RTM. 3104
 CPVC control was unchanged upon addition of 3 phr of the calcined zeolite.
 (0% increase over control DTS value indicating that the zeolite has lost
 its reactivity under these calcination conditions).
 EXAMPLE III
 An 100 mL Al.sub.2 O.sub.3 crucible was heated to 840.degree. C. in a
 muffle furnace. The crucible was removed from the furnace and a 20.0 gram
 portion of a dehydrated zeolite prepared according to Example I was added
 to the crucible which was then returned to the furnace and heated for 15
 minutes. The heated zeolite powder was then poured into another crucible
 at room temperature immediately after removal from the muffle furnace. The
 resulting material exhibited 0.7% weight gain due to water uptake upon
 exposure to ambient conditions after 48 hours. The DTS time of the
 TempRite.RTM. 3104 CPVC control was increased upon addition of 3 phr of
 the shock-annealed zeolite from 13 minutes to 30 minutes (131% increase
 over control DTS value). This example demonstrates the synthesis of a
 zeolite which is non-hygroscopic yet active as a polymer stabilizer.
 EXAMPLES IV-XX
 Another zeolite 4A powder was synthesized by individually preparing the
 following solutions: (1) a sodium silicate solution; (2) a sodium
 aluminate solution; and (3) and a sodium hydroxide solution. The sodium
 silicate solution was prepared by dissolving 255.6 grams of Na.sub.2
 SiO.sub.3.cndot.9H.sub.2 O and 10 grams of C.sub.11 H.sub.23 COOH in 650
 grams of water. The sodium aluminate solution was prepared by dissolving
 270.0 grams of NaAlO.sub.2 in 320 grams of water and the sodium hydroxide
 solution was prepared by adding 500 grams of NaOH in 650 grams of water.
 An additional solution of 10.0 grams of ZnCl.sub.2 and 90.0 grams of water
 was also prepared. All solutions were maintained at approximately about
 55.degree. C. after all solids were dissolved. The sodium hydroxide
 solution was then added while the solution was stirred to the sodium
 aluminate solution. The resulting sodium aluminate/sodium hydroxide
 solution was added concurrently with the zinc chloride solution to the
 sodium silicate solution, again while stirring. The reaction temperature
 was maintained at about 60.degree. C. for 2 hours. The product was
 filtered and rinsed.
 A 100 ml Al.sub.2 O.sub.3 crucible was heated to 840.degree. C. in a muffle
 furnace. The crucible was extracted from the furnace and a 20.0 gram
 portion of a dehydrated zeolite prepared according to Example I was added
 to the crucible which was then returned to the furnace and heated for 15
 minutes. The heated zeolite powder was then poured into a stainless steel
 cup; and cooled with dry ice immediately after removal from the furnace.
 The resulting material exhibited 0.4% weight gain due to water uptake upon
 exposure to ambient conditions after 48 hours. The DTS time of the
 TempRite.RTM. 3104 CPVC compound control was increased upon addition of 3
 phr of the shock-annealed zeolite A, prepared as discussed above from 14
 minutes to 29 minutes (107% increase over control DTS value). Similarly
 prepared zeolites were shock-annealed according to the parameters listed
 below. The (s) in the subscript CO.sub.2(s) means the carbon dioxide was
 solid.
 TABLE I
 Ex- %
 am- Temperature Time H.sub.2 O DTS increase
 ple Coolant (.degree. C.) (min.) Uptake (%) (min) in DTS
 4 air 840 15 0.8 30.5 118%
 5 air 840 15 1.0 33.6 140%
 6 air 790 20 1.1 28.0 100%
 7 air 830 15 1.1 33.4 139%
 8 air 785 20 1.2 30.5 118%
 9 air 810 15 1.5 33.3 138%
 10 CO.sub.2 (s) 840 15 0.4 29.4 110%
 11 CO.sub.2 (s) 820 15 0.8 33.6 140%
 12 CO.sub.2 (s) 830 15 0.9 33.0 136%
 13 CO.sub.2 (s) 810 15 1.1 31.9 128%
 14 CO.sub.2 (s) 820 15 1.5 34.0 143%
 15 CO.sub.2 (s) 800 15 3.9 31.4 124%
 16 CO.sub.2 (s) 840 10 4.4 33.3 138%
 17 CO.sub.2 (s) 790 15 5.7 32.5 132%
 18 CO.sub.2 (s) 820 10 6.7 31.0 121%
 19 CO.sub.2 (s) 750 15 8.0 34.0 143%
 20 CO.sub.2 (s) 770 15 10.5 34.5 146%
 These examples show that a balance of reactivity (DTS) and % H.sub.2 O
 uptake can be achieved with various conditions (temperature, time, cooling
 conditions).
 EXAMPLES XXI-XXXII
 Another series of zeolite 4A powders were synthesized by individually
 preparing the following solutions: (1) a sodium silicate solution; (2) a
 sodium aluminate solution; and (3) a sodium hydroxide solution. The sodium
 silicate solution was prepared by dissolving 255.6 grams of Na.sub.2
 SiO.sub.3.cndot.9H.sub.2 O in 650 grams of water. The sodium aluminate
 solution was prepared by dissolving 270.0 grams of Na.sub.2 AlO.sub.3 in
 320 grams of water, and the sodium hydroxide solution was prepared by
 adding 500 grams of NaOH in 650 grams of water. All solutions were
 maintained at about 55.degree. C. after all solids were dissolved. An
 additional solution of 10.0 grams of ZnCl.sub.2 and 90.0 grams of water
 was also prepared and used as shown in the table below. 10 grams of
 C.sub.11 H.sub.23 COOH was also added to the sodium silicate solution as
 also shown in Table II below. The sodium hydroxide solution was then added
 with stirring to the sodium aluminate solution. The resulting sodium
 aluminate/sodium hydroxide solution was added concurrently with the zinc
 chloride solution (when used) to the sodium silicate solution, again with
 stirring. The reaction temperature was maintained at 60.degree. C. for 2
 hours and then filtered and rinsed.
 In the several of the experiments, shock annealing was used. A 100 mL
 Al.sub.2 O.sub.3 crucible was heated to 840.degree. C. in a muffle
 furnace. The crucible was extracted from the furnace and a 20.0 gram
 portion of a dehydrated zeolite prepared accordingly was added to the
 crucible which was then returned to the furnace and heated for 15 minutes.
 The heated zeolite powder was then poured into a Al.sub.2 O.sub.3 crucible
 at room temperature and cooled immediately after removal from the furnace.
 The resulting material exhibited the weight gain tabulated below due to
 water uptake upon exposure to ambient conditions after 48 hours. The DTS
 time of the TempRite.RTM. 3104 CPVC control was increased upon addition to
 3 phr of the respective zeolite from 14 minutes to the values also listed
 below:
 TABLE II
 Particle Size
 &lt;90%
 mean median Particle %
 Example ZnCl.sub.2 C.sub.11 H.sub.23 COOH Shock- diameter diameter
 diameter increase H.sub.2 O uptake
 # added added annealed (.mu.m) (.mu.m) (.mu.m) in DTS
 (at 48 hrs.)
 21 yes yes yes 1.4 1.1 2.9 100
 0.6%
 22 yes yes no 1.7 1.2 2.5 171
 12.3%
 23 yes no yes 1.5 1.1 2.6 93
 1.0%
 24 yes no no 1.4 1.1 2.5 150
 14.1%
 25 no yes yes 2.1 1.4 5.6 79
 0.5%
 26 no yes no 1.9 1.6 4.1 129
 10.9%
 27 no no yes 11.8 6.9 5.6 93
 0.8%
 28 no no no 27.3 14.9 91.9 114
 2.1%
 29 yes yes yes 1.4 1.1 2.2 93
 1.0%
 30 no no no 1.9 1.5 4.7 121
 12.0%
 31 com- com-
 mercial mercial yes 4.3 4.0 7.1 57
 2.8%
 zeolite zeolite
 32 com- com- no 3.9 3.6 6.5 143
 16.2%
 mercial mercial
 zeolite zeolite
 In Example #28, the zeolite was not formed under the specified conditions.
 The commercial zeolite used in the above examples was molecular sieve
 zeolite 4A, having a particle diameter in the range of about 5 microns,
 available from Aldrich and bearing the product number 23,366-8 (lot #03024
 JQ).
 This series of examples was designed to examine the effects of ZnCl.sub.2,
 C.sub.11 H.sub.23 COOH and shock-annealing on particle size distribution
 to balance the zeolite reactivity and H.sub.2 O uptake. Additionally, the
 experiment was designed to show the effect of shock-annealing on Dynamic
 Thermal Stability of the compound. The shock annealing conditions were not
 optimized for this series.
 EXAMPLE XXXIII
 Another zeolite 4A powder was synthesized by individually preparing the
 following solutions: sodium silicate, sodium aluminate and sodium
 hydroxide solutions. The sodium silicate solution was prepared by
 dissolving 195 g. of Na.sub.2 SiO.sub.3.cndot.5H.sub.2 O and 1.5 g. of
 sodium lauryl sulfate in 525 g. of water. The sodium aluminate solution
 was prepared by dissolving 115 g. of NaAlO.sub.2 in 415 g. of water,
 wherein the solution of NaOH WAs prepared from 210 g. of NaOH in 420 g. of
 water. The resulting sodium aluminate/sodium hydroxide solution was added
 to the sodium silicate solution while stirring at room temperature. A
 thick gel was formed immediately. The agitation was continued for a couple
 of minutes until a consistent mixture is obtained. The system was allowed
 to age for about 16 hours at room temperature. After this period of aging,
 the agitation was started again and the system was heated to 60.degree. C.
 The reaction temperature was maintained for 3 hours. The solution was then
 filtered and rinsed.
 The zeolite 4A powder formed by this method as confirmed by X-ray
 diffraction has a mean particle diameter of 0.35 microns and &lt;90% value of
 0.5 microns as determined using a Coulter LS Particle Size Analyzer.
 A sample dehydrated at 350.degree. C. exhibited a weight gain of 22.6%
 after 4 days exposure at ambient conditions. The DTS measured according to
 ASTM D 2532 in a TempRite.RTM. 3104 CPVC compound (commercially available
 from The B.F.Goodrich Co.) was evaluated with and without the above
 zeolite 4A using a Brabender torque rheometer set at 208.degree. C. bowl
 temperature, 35 rpm, and a 70 g. loading. The DTS time of the
 TempRite.RTM. 3104 CPVC control was 20 minutes. However, the DTS time
 increased to 35 minutes with the addition of 3 parts per hundred resin
 (phr) of the zeolite 4A prepared according to this example. The addition
 of the zeolite 4A to the CPVC compound resulted in a 75% increase in
 thermal stability over the control.
 EXAMPLE XXXIV
 A commercial zeolite 4A powder (Aldrich product #23,366-8, lot #03024-JQ)
 has the following particle size distribution as determined using a Coulter
 LS Particle Size Analyzer: a mean particle diameter of 2.5 .mu.m, a median
 particle diameter of 2.4 .mu.m and a &lt;90% value of 4.6 .mu.m. A sample
 dehydrated at 350.degree. C. exhibited a weight gain of 21% after 2 days
 of exposure to ambient conditions.
 A 100 mL Al.sub.2 O.sub.3 crucible was heated to 840.degree. C. in a muffle
 furnace. The crucible was extracted from the furnace and a 20.0 gram
 portion of the dehydrated commercial zeolite described above was added to
 the crucible, which was then returned to the furnace and heated for 15
 minutes. The heated zeolite powder was then poured into another crucible
 at room temperature immediately after removal from the furnace. The
 resulting material exhibited 1.0% weight gain due to water uptake upon
 exposure to ambient conditions after 48 hours. The DTS time of the
 TempRite.RTM. 3104 CPVC control was increased upon addition of 3 phr of
 the shock-annealed zeolite from 16 minutes to 31.5 minutes (97% increase
 in DTS).
 EXAMPLE XXXV
 A commercial zeolite 4A powder (Aldrich product lot #23,366-8, lot
 #03024-JQ) has the following particle size distribution as determined
 using a Coulter LS Particle Size Analyzer: a mean particle diameter of 2.5
 .mu.m; a median particle diameter of 2.4 .mu.m; and a &lt;90% value of 4.6
 .mu.m. A sample dehydrated at 350.degree. C. exhibited a weight gain of
 21% after 2 days of exposure to ambient conditions.
 A 100 mL Al.sub.2 O.sub.3 crucible was heated to 820.degree. C. in a muffle
 furnace. The crucible was extracted from the furnace and a 20.0 gram
 portion of a dehydrated commercial zeolite described above was added to
 the crucible, which was then returned to the furnace and heated for 15
 minutes. The heated zeolite powder was then poured into a stainless steel
 cup cooled with dry ice immediately after removal from the furnace. The
 resulting material exhibited 3.2% weight gain due to water uptake upon
 exposure to ambient conditions after 48 hours. The DTS time of the
 TempRite.RTM. 3104 CPVC control was increased upon addition of 3 phr of
 the shock-annealed zeolite from 13 minutes to 25 minutes (92% increase in
 DTS).
 EXAMPLE XXXVI
 3 phr of a shock-annealed commercial zeolite 4A powder (as received-Aldrich
 product #23,366-8, lot #03024-JQ) was added to a commercial CPVC compound
 (TempRite.RTM. 3104 CPVC). The zeolite had the following particle size
 distribution a mean particle diameter of 2.5 .mu.m, a median particle size
 of 2.4 .mu.m and a &lt;90% value of 4.6 .mu.m using a Coulter LS Particle
 Size Analyzer. The same sample dehydrated at 350.degree. C. exhibited a
 weight gain of 21% after 2 days of exposure to ambient conditions. The DTS
 time of the TempRite.RTM. 3104 CPVC control was increased upon addition of
 3 phr of the commercial zeolite from 13 minutes to 33 minutes (154%
 increase in DTS). However, staircase drop impact at 22.8.degree. C.
 dropped 52% (control: 25 ft.lb. vs. compound with zeolite 4A: 12 ft.lb)
 and hoop stress at 82.2.degree. C. dropped 16% (control: 4900 psi vs.
 compound with zeolite 4A: 4120 psi) as measured on extruded 3/4 in. SDR 11
 pipe prepared from TempRite.RTM. 3104 CPVC.
 EXAMPLE XXXVII
 3 phr of shock annealed commercial zeolite 4A powder (Aldrich zeolite 4A,
 (product #23,366, lot #03024-JQ) shock-annealed at 840.degree. C. for 15
 minutes) was added to a commercial CPVC compound (TempRite.RTM. 3104
 CPVC). The particle size distribution of the shock-annealed zeolite was
 determined as follows: a mean particle diameter of 3.1 .mu.m; 3.1 .mu.m a
 median particle diameter of 3.1 .mu.m; and a &lt;90% value of 5.7 .mu.m using
 a Coulter LS Particle Size Analyzer. The shock-annealed sample exhibited a
 weight gain due to water uptake of &lt;2% after 2 days of exposure to ambient
 conditions. The DTS time of the TempRite.RTM. 3104 CPVC control was
 increased from 16 minutes to 33 minutes (106% increase in DTS). However,
 the staircase drop impact at 22.8.degree. C. dropped 44% (control: 25
 ft.lb. vs. compound with shock-annealed zeolite: 14 ft.lb.) and hoop
 stress at 82.2.degree. C. dropped 9% (control: 4900 psi vs. compound with
 shock-annealed zeolite: 4460 psi) as measured on extruded 3/4 in. SDR 11
 pipe prepared from TempRite.RTM. 3104 CPVC.
 EXAMPLE XXXVIII
 Two compounds using PVC 103EPF76 resin from The Geon Company were made in
 the following manner. The ingredients were mixed in an Henschel mixer at
 3500 rpm for 15 min. Strips (2 inches wide and 0.035 inches thick) were
 extruded at 200.degree. C. via a Haake conical twin screw extruder at
 200.degree. C. The zeolite used in this case was prepared as described in
 Example XXXIII and dried in a furnace at 450.degree. C. before use. Its
 characteristics are summarized in the following table. Variable Height
 Impact Test (VHIT) values were measured on the strips to quantify impact
 properties (ASTM D 4226).
 The following recipe was used:

PVC 103EPF76 100 phr
 Dibutyl tin bis-(2ethylhexylmercapto acetate) 1.6
 Calcium stearate 1.5
 Paraffin wax 1.5
 Oxidized polyethylene 0.1
 Acrylic processing aid 1.0
 Impact modifier 5
 The following results were obtained:
 TABLE IX
 Control Compound 1
 Zeolite content 0 2
 &lt;90% Zeolite Particle diameter -- 0.6
 (.mu.m)
 Mean Particle diameter (.mu.m) -- 0.35
 H.sub.2 O content (%) -- 0
 VHIT values (in.lb./in.) 2.43 .+-. 0.18 2.45 .+-. 0.13
 This example illustrates that a small particle size zeolite with reduced
 water content yields good impact properties as illustrated by the VHIT
 values of the PVC strips.
 In summary, novel and unobvious modified zeolites have been described as
 well as the process for forming such zeolites. Although specific
 embodiments and examples have been disclosed herein, it should be borne in
 mind that these have been provided by way of explanation and illustration
 and the present invention is not limited thereby. Certainly modifications
 which are within the ordinary skill in the art are considered to lie
 within the scope of this invention as defined by the following claims.