The present invention relates to the use of zirconium tetrachloride as a catalyst in polymerizing aromatic vinyl compounds.

More specifically, the present invention is directed to the making of copolymers of styrene with alpha-methyl styrene, or more preferably, terpolymers styrene with alpha-methyl styrene and a third monomer, most preferably limonene. There can also be used other terpenes such as alpha-pinene, beta-pinene or dipentene in place of all or part of the limonene. Normally, the limonene is employed as the more readily available di-limonene. There can also be used in place of the terpene vinyl toluene, e.g., p-vinyl toluene or t-butyl styrene, e.g., p-t-butyl styrene.

There can be formed styrene homopolymers as well as homopolymers of t-butyl styrene, d-limonene, alpha-methyl styrene, etc. There also can be formed tetrapolymers of styrene, t-butyl styrene, alpha-methyl styrene and a terpene, preferably d-limonene although the other terpenes set forth above can be used.

The use of zirconium tetrachloride produces light-colored resins with or without the d-limonene or other third monomer.

One of the advantages of using zirconium tetrachloride as a catalyst is that there are obtained good yields (over 90% based on the monomers) of resins having high melting points, i.e., over 95 Ring) Thus, resins can be prepared having melting points up to 155 C and even higher with t-butyl styrene homopolymer. In the working examples, the melting points ranged from 103 the styrene homopolymer, the styrene-alpha methyl styrene copolymer, C, styrene-alpha-methyl styrene-d-limonene terpolymer.

When t-butyl styrene is present it generally yields a higher melting product. Thus, the tetrapolymer of styrene, t-butyl styrene, alpha-methyl styrene and di-limonene had a melting point of 125 homopolymer of t-butyl styrene can be made with a melting point even above 155

The zirconium tetrachloride is usually employed in an amount of 0.1 to 8% by weight of the total polymerizable monomers. The catalyst employed preferably consists of or consists essentially of the zirconium tetrachloride.

The reaction can be carried out over a wide temperature range, e.g., 20 to 55 temperature, however, is not a critical feature of the invention.

If there is utilized aluminum chloride as a replacement for zirconium tetrachloride wherein the catalyst is added to the monomer/solvent (direct method) there is experienced severe flash back, e.g., the localized heat of reaction violently erupts the reaction materials. When there is utilized aluminum chloride wherein the catalyst is first slurried in the solvent then the monomer is added over a period of time (reverse addition method) the resin obtained is low in melting point and yield. Zirconium tetrachloride gives better yields and higher melting points than aluminum chloride.

Boron trifluoride also gave lower melting point/lower yield resins in reverse additions than zirconium tetrachloride. Zinc chloride was ineffective as a catalyst. Ferric chloride gave a resin which was almost black in color.

Another advantage of the zirconium catalyst resins is that these resins when compounded into a hot melt adhesive exhibit excellent heat age characteristics and in this respect were superior to boron fluoride catalyzed resins.

Applicants have found that when utilizing the reverse addition method using zirconium tetrachloride the yield and melting point are significantly lower than when utilizing the direct method of catalyst addition.

The resins of the invention have utility as dry cleaning sizing agents which are utilized to give body to clothes after dry cleaning. They also are useful in hot melt adhesive compositions, particularly with paraffin wax and resinous ethylene-vinyl acetate copolymers, e.g., Elvax.

Compatibility of the resins of the invention is controlled by the monomer composition of the resin. Styrene in general promotes incompatibility with paraffin wax and ethylene vinyl acetate. Vinyl toluene and p-t-butyl styrene are more compatible than styrene, but not as compatible as limonene styrene. Terpenes such as those set forth above, e.g., d-limonene promote compatibility as does alpha-methyl styrene.

The polymers can also be molded to form cups. The optimum resin does not use a single monomer since styrene by itself produces a 100% yield of a much too incompatible water-white resin. Alpha-methyl styrene by itself produces a resin which has too low a melting point. d-Limonene also by itself produces a soft resin with a poor yield. In order to optimize compatibility, yield, and a melting point it is necessary to judiciously select the proper monomers and ratios.

Applicants have found that for use in hot melt adhesives that the ratio of 10-40 weight percent of styrene and 90-60 weight percent of alpha-methyl styrene is optimum for a copolymer.

In making terpolymers there is generally employed 5 to 50% by weight styrene, 5 to 80 % alpha-methyl styrene and 5 to 50 % of terpene, e.g., p-limonene or other third component. In making tetrapolymers there is generally employed 5 to 50 % styrene, 5 to 80 % alpha-methyl styrene, 5 to 60 % terpene and 5 to 50 % t-butyl styrene.

When the reaction is carried out in a solvent there can be used as solvents, e.g., aromatic hydrocarbon such as xylene, benzene, toluene, or aliphatic hydrocarbons, e.g., heptane or mineral spirits.

Unless otherwise indicated all parts and percentages are by weight.

Example 1

______________________________________A Alpha-methyl styrene   750 gramsB Styrene                250C Xylene                 650D Zirconium tetrachloride                     10E Water                  100F Water                  100G Water                  100______________________________________

Materials A, B, and C were placed in a three-neck flask equipped with agitator, reflux condenser and thermometer. The temperature was brought to 30 was controlled by cooling to maintain 30 reaction was held at 30 material E was added. The mixture was stirred for 1/2 hour, then the bottom water layer was removed. The resin solution was subsequently washed with materials F and G similarly. The resin was then distilled atmospherically to 200 melting point of 103

Example 2

______________________________________A Alpha methyl styrene   333 gramsB Styrene                333C d-limonene             333D Xylene                 650E Zirconium tetrachloride                     20F Water                  100G Water                  100H Water                  100______________________________________

Materials A, B, C, and D were placed in a three-liter, three-necked flask equipped as in Example 1. The temperature was brought to 30 Material E was added over 20 minutes controlling the temperature at 30 30 at 75 water layer was removed. Material G was added and the resin solution was again washed and the water layer removed. Material H was similarly utilized to wash the resin solution. The resin was then distilled atmospherically to 200 minutes. The yield was 950 grams (95%), MP was 120 color was less than 1 on the Gardner Scale.

Example 3

______________________________________Hot Melt adhesive Formulation______________________________________A Paraffin Wax           25 partsB Resin                  40 partsC Elvax 260*             35 parts______________________________________ Ethylene vinyl acetate copolymer, melt index (5-6), vinyl acetate content 28% product of E.I.DuPont de Nemours

Procedure

Load A into a 250 ml Beaker. Bring to 300 dissolve it. Add C gradually keeping the temperature at 325 350

Thermal Stability Studies

Hot melt adhesives were prepared using the formulation of Example 3. The resins of Examples 1 and 2 were compared with commercially available hot melt resins for resistance to thermal degradation showing their much increased resistance to color change and resistance to skimming.

Then grams of hot melt sample was placed in an aluminum weighing dish with an exposed surface area of approximately three square inches. The dish was placed in an oven at 350 melt adhesive was noted upon removal from the oven and compared with an original sample for color change and skimming. The less skim and the lighter the color the better the aging character.

______________________________________   Original  Aged at 350   Color Skim    Color      Skim______________________________________Example 1 White   None    Egg white                              NoneExample 2 White   None    Off white                              NoneCRJ-683(1)     Grey    None    Black    Small Amount     brownWingtac 95(2)     Light   None    Black    Small Amount     yellowST-5115(3)     Yellow  None    Dark brown                              Medium                              Amount______________________________________ (1)CRJ-683 is a commercially available piperylene stream resin having a M of 95 (2)Wingtac-95 is a commercially available piperylene resin manufactured b Goodyear Chemical with a MP of 95 (3)ST-5115 is a commercially available terpene resin (a beta pinene resin melting at 115

The cloud point of a hot melt adhesive, i.e., the temperature at which the molten adhesive becomes turbid, is controlled by the ratios of monomers in the resin. For example:

______________________________________d-limonene (grams)           38      35 1/2  34 1/2                                 33 1/2Alpha-methyl styrene (grams)           38      35 1/2  34 1/2                                 33 1/2Styrene (grams) 24      29      31    33 1/2Cloud point of hot meltadhesive        145                   160                           186                                 230______________________________________

As can be seen, minor changes in the percentage of styrene cause major changes in compatibility (cloud point). The above resins all utilized two percent zirconium tetrachloride as a catalyst (based on total monomers) and they were produced similarly to Example 2.

Example 4

______________________________________A p-t-butyl styrene      750gramsB Styrene                250C Xylene                 650D Zirconium Tetrachloride                    3.5E Water                  100F Water                  100G Water                  100______________________________________

The above formulation was processed in a similar manner to Example 1 yielding 997 grams of water white resin with a melting point of 155

Example 5

______________________________________A alpha methyl styrene   750gramsB Styrene                250C Heptane                650D Zirconium Tetrachloride                     5E Water                  100F Water                  100G Water                  100______________________________________

The above formulation was processed in a similar manner to Example 1 yielding 978 grams of a water white polymer with a melting point of 120

Example 6

______________________________________A Styrene                1000gramsB Xylene                  650C Zirconium Tetrachloride                      5D Water                   100E Water                   100F Water                   100______________________________________

The above ingredients were processed in a similar manner to Example 1 yielding 1042 grams of a water white resin with a melting point of 110

Example 7

______________________________________A Styrene                250 gramsB p-t-butyl styrene      250C alpha methyl styrene   250D d-limonene             250E Xylene                 650F Zirconium Tetrachloride                     10G Water                  100H Water                  100I Water                  100______________________________________

The above formulation was processed in a similar manner to Example 1 with A, B, C .[.and.]. D .Iadd.and E .Iaddend.being placed in flask initially yielding 1011 grams of a water white resin with a melting point of 125

The ranges of proportions of terpolymers and tetrapolymers can be varied at the will of the synthesizer. Normally the blends of monomers are selected to obtain whatever solubility parameter is desired. It is even possible to prepare viscous liquid polymers, e.g., homopolymers of d-limonene, which are useful as adhesives.