Process for hydrotreating resins to lighten colour

Abstract: The color of hydrocarbon resins having carbon-carbon double bonds and containing color bodies is lightened by a hydrotreating process consisting essentially of contacting a substantially noncrystalline resin with hydrogen at a hydrogen pressure of 1 to 20 bar (14.5 to 290 psi) in the presence of a catalyst that promotes the hydrogenation of the color bodies without substantially changing the softening point or the content of carbon-carbon double bonds in the resin. When the catalyst is nickel/zinc oxide, the catalyst activity for color reduction remains essentially unchanged at chlorine loads up to 4.2% by weight.

Description: This invention relates to a process for lightening the color of resins and resins produced by this process. Methods for hydrogenating hydrocarbon resins to lighten the color are well known and generally produce a product that is "water white" in color. The aliphatic and/or aromatic unsaturation present in the resin is partially or completely eliminated, providing a product with improved oxidative stability, UV resistance and color stability. However, particularly in the case of resins derived from aromatic feedstreams, hydrogenation also alters the physical properties of the resin, which can make it less desirable for use in products such as adhesives, caulks and sealants, plastic and rubber modifiers, and printing inks. Processes for improving the color of "hydrocarbon fractions" and hydrocarbon resins by selective hydrogenation of color bodies and color body precursors have been proposed. For example, European Patent Application 617,053 describes a process for hydrotreating hydrocarbon resins in the presence of a catalyst that promotes the hydrogenation of color bodies without changing the content of carbon-carbon double bonds in the resin or its physical properties. A hydrogen pressure of 50 psi up to 2500 psi (344 - 17,235 kPa) was used, and the preferred catalysts were copper chromite and copper/zinc. EP-A-0 389 119 discloses a process for catalytically hydrogenating petroleum resin which contains a small content of halogen. The hydrocarbon resin is prepared in a solvent which is contacted with a sulphide activated catalyst including oxides selected from Group VIII metal, an oxide of W or Mo and a basic promoter oxide including an element from Group IA, IIA, lanthanides or actinides of the Periodic Table. There is still a need for additional processes to reduce the colour of a resin without changing its other desirable physical characteristics. According to the present invention, there is provided a process for lightening the color of a substantially non-crystalline hydrocarbon resin having a weight average molecular weight of 250-10,000, having carbon-carbon double bonds and which contains color bodies, comprising contacting the resin with hydrogen at a hydrogen pressure of 100-2000 kPa (14.5 to 290 psi) in the presence of a nickel/zinc oxide catalyst which promotes hydrogenation of the color bodies without substantially changing the softening point or the content of carbon-carbon double bonds in the resin. The invention is also directed to a process for preparing a substantially non-crystalline hydrocarbon resin having a weight average molecular weight of 250-10,000 and having carbon-carbon double bonds comprising the steps of: (i) polymerizing monomers in a solvent to form a hydrocarbon resin, and (ii) lightening the colour of the hydrogenation resin according to the above described process whilst the resin remains dissolved in the solvent used for the polymerization. The invention provides a method for hydrotreating normally colored resinous materials to lighten the color, preferably to water white (less than Gardner color 1). Normally measured properties other than color are substantially unchanged. When a Ni/Zn oxide catalyst is used for the hydrotreating process, the activity of the catalyst for color reduction remains essentially unchanged in spite of a high chlorine load. Products containing these lighter colored resins exhibit properties substantially the same as those of products that contain untreated resins, while providing a more pleasing visual appearance. The use of a low hydrogen pressure reduces the equipment and operating costs associated with the practice of the process of this invention. The process of this invention for contacting a colored resin with hydrogen in the presence of a catalyst is subsequently referred to as "hydrotreating". The process is a selective hydrogenation process, since the color bodies present in the resin are hydrogenated and the content of carbon-carbon double bonds in the resin remains substantially unchanged. Carbon-carbon double bonds include both ethylenic and aromatic double bonds. In addition, color body precursors are not hydrogenated in this process. In conventional catalytic hydrogenation processes, the color bodies, the color body precursors and carbon-carbon double bonds in the resin are hydrogenated. The process of this invention can be used to lighten the color of a wide variety of hydrocarbon resins such as C-9 resins, C-5 resins, mixed C-9/C-5 resins, vinyl aromatic-modified C-5 resins, dicyclopentadiene resins, aromatic-modified dicyclopentadiene resins, terpene resins terpene-phenolic resins, mixed C-9/C-4 resins, and coumerone-indene resins. The term "resin" as used in this specification indicates a low molecular weight synthetic polymer made by polymerizing unsaturated monomers either thermally or in the presence of an acidic catalyst, e.g., a Friedel-Crafts catalyst. These polymers have a weight average molecular weight (M w ) of 250-10,000, preferably 400-6,000, and most preferably 400-2,000. The notations "C-5" and "C-9" indicate that the monomers from which the resins are made are predominantly hydrocarbons having 4-6 and 8-10 carbon atoms respectively. All of the resins mentioned above typically have a yellow or amber color before treatment. The softening point of the resin to be treated is not critical, unlike known hydrogenation processes where the resinous starting material is stripped to obtain a resin with a particular softening point before hydrogenating. Catalysts useful in the process of this invention are hydrogenation catalysts that are selective enough in their action so that only the color bodies are hydrogenated. Color bodies are highly conjugated, polyunsaturated organic compounds that may also contain polar atoms such as oxygen, sulfur and nitrogen, e.g., indoles and quinones. The carbon-carbon double bonds in the resin are not substantially hydrogenated. Therefore the properties of the resin that are commonly measured, e.g., softening point, cloud point, molecular weight, and heat stability, are also unaffected. In addition, color body precursors are not substantially hydrogenated. Color body precursors are defined as colorless materials that become colored after aging. The catalysts can be used directly or can be carried on a suitable support such as silica, alumina, or carbon. Nickel/zinc oxide on a silica support is most preferred. It should be noted that the selectivity of a particular catalyst can be different under different processing conditions. Additional processing steps such- as stripping the resin to a particular softening point before hydrotreating and then redissolving, or stripping the resin after hydrotreating to a particular softening point, can be used. However, one of the advantages of this invention is that they are not needed. Standard procedures such as isolating the hydrotreated resin by stripping and steam sparging, or neutralizing catalyst residues from the polymerization of the monomers used to make the resins can be included. Quenching agents such as organic phosphites and reactive diluents such as olefinic diluents are not required. A reactive diluent is defined as a diluent that reacts with the hydrogen or the resin. Such diluents are described in U.S. Patent 5,171,793. The temperature, pressure, reaction time and amount of catalyst used in the process of this invention depend upon various factors such as the type of resin that is being treated, the final color desired and the economics of the process, e.g., some catalysts are very expensive and it would not be commercially feasible to use large amounts. The hydrogen pressure ranges between 1 and 20 bar (14.5 to 290 psi), more preferably between 1 and 15 bar (14.5 to 218 psi), and most preferably between 1 to 10 bar (14.5 to 145 psi). The temperature preferably ranges between 100° and 300°C, more preferably between 150° and 300°C, and most preferably between 200° and 300°C. The treatment time typically is between 1 and 10 hours. The amount of catalyst used preferably ranges between 0.01 and 50%, based on the weight of the resin, more preferably between 0.5 and 40%, and most preferably between 1 and 35%. In general, higher reaction temperatures or longer reaction times are required if the weight percent catalyst is low. When the resins are made by polymerization of monomers in a solvent; the hydrotreating process of this invention can be carried out in the original polymerization solvent after the resins are neutralized and polymerization catalyst residues are removed. The solvent can be recovered after the treatment and recycled in the process. The process can also be carried out in an aromatic or aliphatic solvent solution of redissolved resin, or the resins can be treated in the molten state (neat). The process can be a batch or continuous process. In batch reactions, the catalyst can be recycled several times. In the past, when the resins to be hydrogenated were made by polymerizing monomers in the presence of a chlorine-containing catalyst, the feedstocks were typically dechlorinated before hydrogenation to prevent deactivation of the hydrogenation catalyst. A significant advantage of the process of this invention is that when a Ni/Zn oxide catalyst is used, the catalyst activity for color reduction remains essentially unchanged despite chlorine loads up to about 4.2%. At the same hydrogenation temperature and the high hydrogen pressures used in hydrogenation processes, the catalyst would be poisoned by these high chlorine loads and lose its activity. Using the process of this invention, the color of aliphatic hydrocarbon resins is preferably lightened to less than Gardner 3, more preferably less than Gardner 1. The color of aromatic resins is preferably lightened to Gardner 5 or less, preferably Gardner 3 or less, and most preferably less than Gardner 1. The color of mixed aromatic/aliphatic resins is preferably lightened to Gardner 3, more preferably less than Gardner 1. After hydrotreating, an antioxidant is generally added to improve heat and color stability, e.g., butylated hydroxytoluene or IRGANOX® 1010, a hindered phenol available from Ciba-Geigy, Hawthorne, NY, U.S.A. IRGANOX® 1010 is tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane. The antioxidant is preferably used in an amount of 0.05 to 1.0% by weight based on the total weight of the resin. The light colored resins prepared by the process of this invention can be used in all known applications for hydrocarbon resins and hydrogenated hydrocarbon resins, such as tackifiers for hot melt adhesives and hot melt pressure sensitive adhesives. These adhesives can be used, for example, in nonwoven products such as feminine care products and disposable diapers, and in packaging tape and roadmarking compositions. The light colored resins made by the process of this invention can be used with a wide variety of polymers in these adhesive compositions, for example, styrene-isoprene-styrene, styrene-butadiene-styrene, styrene/ethylene-butylene/styrene, ethylene/butylene/acrylate, and ethylene/methacrylate polymers, as well as styrene/butadiene rubbers, and natural rubbers. The Mettler Drop Softening Point (MDSP) is determined using a modified ASTM D 3461-76 method on the Mettler FP800 thermosystem consisting of the FP800 central processor and the FP83 dropping cell available from Mettler Instrumentation B.V., Tiel, the Netherlands. The sample cup used is a modified type ME 18732 with an opening of 4.5 mm. A starting temperature of approximately 15°C below the expected softening point is chosen and a heating rate of 3°C/min is used. MMAP is the mixed methylcyclohexane aniline cloud point, which is determined using a modified ASTM D 611-82 (1987) procedure. Methylcyclohexane is substituted for the heptane used in the standard test procedure. The procedure uses resin/aniline/methylcyclohexane in a ratio of 1/2/1 (5 g/10 ml/5 ml) and the cloud point is determined by cooling a heated, clear blend of the three components until complete turbidity just occurs. Hydrogenation of the unsaturated portion of a resin, particularly aromatic unsaturation, would result in an increase in the MMAP. In the process of this invention, the difference between the MMAP of the resin before hydrotreating and the MMAP after hydrotreating is 5°C or less, preferably 3°C or less and most preferably 2°C or less, indicating that the content of carbon-carbon double bonds in the resin is essentially unchanged. To determine Gardner color, 50 weight percent resin is mixed with reagent grade toluene at room temperature until it dissolves. The color of the resin solution is determined according to standard method ISO 4630 (also ASTM D 1544-80) on the LICO-200 photometer available from Dr. Lange, Nederland B.V., Kesteren, the Netherlands. The color values range from 1 to 18, with 18 being the darkest. A color of less than Gardner 1 indicates a water white solution. In this specification all parts and percentages are by weight unless otherwise noted. Example 1 This example describes the hydrotreatment of a C-9 hydrocarbon resin. Hercures® A120 C-9 hydrocarbon resin was dissolved in an aliphatic solvent (35% resin by weight) and placed in a fixed basket, stirred autoclave. Hercures® A120 hydrocarbon resin is available from Hercules BV, Middelburg, the Netherlands. The resin feedstock typically contains styrene, alpha-methylstyrene, vinyltoluenes, indene and alkyl-substituted indenes as reactive compounds, and is polymerized using a BF 3 catalyst. A pelleted Ni/ZnO hydrogenation catalyst on a SiO 2 carrier was activated at 250°C under hydrogen and the evolving water was removed by a nitrogen purge. The activated catalyst (350 g) was then added to 2850 g of the resin solution at reaction temperature. The catalyst is Type H10126 RS, available from Katalysatorenwerke Hüls GmbH, Marl, Germany. The hydrotreatment was carried out at 10 x 10 5 Pascals (Pa) (10 bar or 145 psi) hydrogen pressure for 2.5 hours at 265°C. After filtration, the resulting resin was isolated by conventional stripping techniques, followed by a steam sparge at 210°C. The hydrotreated resin had a Gardner color (G) of 0.3 measured as 50% resin in toluene; a Mettler drop softening point (MDSP) of 125.1°C, and a mixed methyl aniline cloudpoint (MMAP) of 4°C. The untreated C-9 resin had a Gardner color of 5.4, a MDSP of 128.1°C, and a MMAP of 2°C. Example 2 This example describes the hydrotreatment of a C-9 hydrocarbon resin that was still dissolved in the polymerization solvent. The C-9 feedstock used was Hercures® A120 hydrocarbon resin, available from Hercules BV, Middelburg, The Netherlands. The resin was still dissolved in the polymerization solvent containing about 70% resin and 30% oligomeric oils and recycled, unreacted resin oils. The low boiling fraction had already been removed by partial distillation. A pelleted Ni/ZnO catalyst on a SiO 2 carrier was used as the hydrogenation catalyst. Before reaction the catalyst was activated at 250°C under hydrogen, and evolving water was removed by a nitrogen purge. The catalyst was Type H10126 RS, available from Katalysatorenwerke Hüls GmbH, Marl, Germany. The activated catalyst (350 g) was added to 2500 g of the resin solution at reaction temperature. The hydrotreatment was carried out at 10 x 10 5 Pa (10 bar, 145 psi) hydrogen pressure for 8 hours at 265°C. After filtration, the resulting resin was isolated by conventional stripping techniques, followed by a steam sparge at 210°C. The resulting resin had a Gardner color of 0.8 measured as 50% resin in toluene and a MMAP of 3°C. The untreated C-9 resin had a Gardner color of 5.4 and a MMAP of 2°C. Example 3 This example describes the hydrotreatment of an aromatic-modified C-5 hydrocarbon resin that was still dissolved in the solvent that was used for polymerization. The C-5 resin used was Hercotac® 205 hydrocarbon resin, available from Hercules BV, Middelburg, the Netherlands. The resin is made from the C-9 resin oil described in Example 1 and piperylene concentrate. The major components of the piperylene concentrate were pentenes; (di-)cyclopentadiene; )cyclopentadiene; trans-pentadiene-1,3; cyclopentene; and alkanes. The resin was still dissolved in the solvent used for the polymerization containing about 70% resin and 30% oligomeric oils and recycled, unreacted resin oils/piperylene concentrate. The low boiling fraction of the polymerizate had already been removed by a partial distillation. The catalyst used for the hydrotreatment was pelleted Ni/ZnO on a SiO 2 carrier. Before reaction the catalyst was activated at 250°C under hydrogen, and evolving water was removed by a nitrogen purge. The catalyst was Type H10126 RS, available from Katalysatorenwerke Hüls GmbH, Marl, Germany. The activated catalyst (350 g) was added to 2000 g of the resin solution at reaction temperature. The hydrotreatment was carried out at 10 x 10 5 Pa (10 bar, 145 psi) hydrogen pressure for 8 hours at 265°C. After filtration, the resulting resin was isolated by conventional stripping techniques followed by a steam sparge at 210°C. The resulting resin had a Gardner color of 2.1 measured as 50% resin in toluene, and a MMAP of 44°C. The untreated C-5 resin had a Gardner color of 7.0 and a MMAP of 39°C. Example 4 This example describes the effect of chlorine uptake on the decolorization activity of the catalyst. The catalyst used was pelleted Ni/ZnO on a SiO 2 carrier and is available as Type H10111 RS from Katalysatorenwerke Hüls GmbH, Marl, Germany. The same batch of catalyst (100 g) was used for six successive hydrotreatment runs. In each run, a solution of 1500 g of Hercures® A101 hydrocarbon resin containing 416 mg/kg chlorine in 1500 g of aliphatic diluent was hydrotreated in a fixed bed, stirred autoclave for 3-5 hours at 265°C using a hydrogen pressure of 10 x 10 5 Pa (10 bar, 145 psi). Hercures® A101 is a C-9 aromatic resin available from Hercules BV, Middelburg, the Netherlands. During each run the decolorization activity was calculated from δE color reduction. The chlorine uptake by the catalyst was calculated from the chlorine reduction in the resin. The results are shown in Table 1. Run No. 2 4 6 Feed A101® C-9 aromatic resin 1500 g 1500 g 1500 g Aliphatic diluent 1500 g 1500 g 1500 g Catalyst Ni/ZnO 100 g 100 g 100 g Chlorine uptake % 1.8 3.0 4.2 Activity Decolorization k(δE) 1.9 1.8 1.7 Calculations: Total color difference (δE) from Hunter Lab color scale δE = (δL) 2 +(δa) 2 +(δb) 2 Activity (k) k = (ln C0 Ct ) x Wr Wc x t Where C0 = Color at time = 0 (Start of reaction) Ct = Color at time = t hour Wr = Weight resin (g) Wc = Weight catalyst (g) t = Time (h) The results show that the activity for color reduction k(δE) remains practically unchanged despite chlorine loads of the catalyst up to 4.2%. Example 5 This example describes the hydrotreating of a C-5 hydrocarbon resin that was still dissolved in the solvent used for the polymerization. The resin used was Hercures® C hydrocarbon resin, available from Hercules BV, Middelburg, the Netherlands. The resin was prepared from piperylene concentrate using an AlCl 3 catalyst. The major components of the concentrate were pentenes; (di-) cyclopentadienes; trans-pentadiene-1,3; cyclopentene; cis-pentadiene-1,3 and alkanes. The resin was still dissolved in the polymerization solvent containing about 70% resin and 30% oligomeric oils and recycled unreacted piperylene concentrate. The low boiling fraction had already been removed by a partial distillation. The catalyst used for the hydrotreatment was pelleted Ni/ZnO on a SiO 2 carrier, available as type H10126 RS from Katalysatorenwerke Hüls GmbH, Marl, Germany. Before reaction the catalyst was activated at 250°C under hydrogen, and evolving water was removed by a nitrogen purge. The catalyst (350 g) was added to 2000 g of the resin solution at reaction temperature. The hydrotreatment was carried out at 10 x 10 5 Pa (10 bar, 145 psi) hydrogen pressure for 6 hours at 265°C. After filtration, the resulting resin was isolated by conventional stripping techniques followed by a steam sparge at 210°C. The resulting resin had a Gardner color of 1.3 measured as 50% resin in toluene, and a MMAP of 99°C. An untreated C-5 resin had a Gardner color of 6.3 and a MMAP of 94°C. Example 6 (Reference Example - not in accordance with the invention) This example describes the hydrotreatment of an aromatic-modified C-5 hydrocarbon resin. Hercotac® 205 hydrocarbon resin was dissolved in an aliphatic solvent (35% resin by weight) and dechlorinated by a conventional method to prevent deactivation of the catalyst by chlorine. Hercotac® 205 is an aromatic-modified C-5 hydrocarbon resin made from the C-9 resin oil described in Example 1 and the piperylene concentrate described in Example 3, using an AlCl 3 catalyst. The resin is available from Hercules BV, Middelburg, the Netherlands. The catalyst used for the hydrotreatment was a palladium-on-carbon extrudate, available as Type X4560 from Engelhard, Rome, Italy. The catalyst (100 g) was added to 2850 g of the resin solution at reaction temperature. The hydrotreatment was carried out at 10 x 10 5 Pa (10 bar, 145 psi) hydrogen pressure for 4 hours at 265°C. After filtration, the resulting resin was isolated by conventional stripping techniques followed by a steam sparge at 210°C. The resulting resin had a Gardner color of 4.0 measured as 50% resin in toluene, and a MMAP of 37°C. The untreated C-5 resin had a Gardner color of 6.6 and a MMAP of 33°C.

Claims: A process for lightening the color of a substantially non-crystalline hydrocarbon resin having a weight average molecular weight of 250-10,000, having carbon-carbon double bonds and which contains color bodies, comprising contacting the resin with hydrogen at a hydrogen pressure of 100-2000 kPa (14.5 to 290 psi) in the presence of a nickel/zinc oxide catalyst which promotes hydrogenation of the color bodies without substantially changing the softening point or the content of carbon-carbon double bonds in the resin. A process according to Claim 1, wherein the hydrogen pressure is 100-1500 kPa (14.5 to 218 psi). A process according to Claim 2, wherein the hydrogen pressure is 100-1000 kPa (14.5 to 145 psi). A process according to any preceding Claim, wherein the catalyst is on a silica support. A process according to any preceding Claim, wherein the catalyst activity for color reduction remains essentially unchanged at chlorine loads up to 4.2% by weight. A process according to any preceding Claim, wherein the resin is an aliphatic hydrocarbon resin and the Gardner color is less than 3 after the contacting step. A process according to Claim 6, wherein the Gardner colour of the resin is 5 or less after the contacting step. A process according to any preceding Claim, wherein the substantially noncrystalline hydrocarbon resin contains color body precursors and the color body precursors are not hydrogenated during the contacting step. A process according to any preceding Claim, wherein the resin is a C-5 hydrocarbon resin, a C-9 hydrocarbon resin, a mixed C-5/C-9 hydrocarbon resin, a vinyl aromatic-modified C-5 hydrocarbon resin, a dicyclopentadiene resin, an aromatic-modified dicyclopentadiene resin, a terpene resin, a terpene-phenolic resin, a mixed C-9/C-4 resin or a coumerone-indene resin. A process according to any preceding Claim, wherein the contacting step takes place while the resin is in the molten state (neat). A process for preparing a substantially non-crystalline hydrocarbon resin having a weight average molecular weight of 250-10,000 and having carbon-carbon double bonds comprising the steps of: (i) polymerizing monomers in a solvent to form a hydrocarbon resin, and (ii) lightening the colour of the hydrocarbon resin according to the process of any preceding Claim whilst the resin remains dissolved in the solvent used for the polymerization. A process according to Claim 11, wherein the polymerization solvent is recovered after the contacting step and recycled.

Inventors: BERREVOETS ERIK, VAN DRONGELEN JAN, BERREVOETS, ERIK, VAN DRONGELEN, JAN
Applicants: HERCULES INC, HERCULES INCORPORATED
Application year: 1995
Main classification: C08F8
IPC codes: C08J9, C08F6, C08F8