Biocide-Polyester concentrates and biocidal compositions prepared therefrom

Abstract: Concentrates of various classical biocides in a polyester carrier resin when incorporated into a substrate resin, preferably a polyolefin such as polypropylene or polyethylene, provide the substrate polymer which biocidal activity with superior resistance to discoloration (yellowing) than when the biocide is directly incorporated into the substrate polymer as a powder at the same total concentration.

Description: The instant invention pertains to concentrates which comprise a biocidal compound and a polyester carrier resin. The addition of such concentrates into polymer substrates provides biocidal activity to said polymer substrate while preventing discoloration of the substrate. WO-A-92/07031 teaches the process for preparing a soluble-stable dispersion of a solid biocide comprising a swellable vinyl polymer with a liquid carrier to enable the incorporation of difficultly soluble biocides into polymer resins. GB-A-2 262 468 describes the application of a composition comprising a biocide in a poly-(vinyl alcohol) carrier medium to the surface of a mold or former in order to render a plastic acticle biocidally active during the manufacturing process. JP-A-62 000 544 teaches the incorporation of an antibiotic by premixing it with poly(ethylene glycol) or silicone oil and melt blending the pre-mixture into a polyester resin or by preparing a master batch containing the antibiotic in a higher concentration and melting blending the master batch into the polyester. U.S. 5,929,132 discloses an improved process for preparing a storage-stable dispersion of a biocide which comprises the stepts of (a) dispersing a solid biocide and a carrier to form a biocide concentrate, (b) heating said biocide concentrate to an elevated temperature to provide a storage-stable mixture of biocide, resin and carrier, and (c) cooling said mixture under continuous stirring to provide a homogeneous, storage-stable liguid dispersion. U.S. 5,639,803 discloses a multi-step process for preparing a storage-stable dispersion of a biocide which comprises the steps of (a) contacting a heat-swellable resin with a carrier to provide a liquid mixture of a resin and a carrier, (b) heating said liquid mixture to an elevated temperature to cause the resin to swell by virtue of carrier absorption into the resin to provide a swelled resin in said liquid mixture, and (c) adding a biocide to said swelled resin and mixing to provide a homogeneous, storage-stable liquid dispersion. EP-A-0 843 963 discloses a pesticide formulation which comprises a pesticide compounded with a biodegradable thermoplastic aliphatic polyester resin. The pesticide formulation provides pesticidal effect for controlled release by releasing active ingredient gradually and by degrading aliphatic polyester resin which can be disappeared by microbial attack in soil. While the process for putting biocides into plastics by adding the neat active biocidal compound into the polymer substrate during processing or manufacturing is known, this process can lead to discoloration of the final biocidally active substrate. The instant process involves preparing first a biocide-polyester concentrate which is then subsequently added to the polymer substrate. This leads to a final product which is both biocidally active and is resistant to discoloration. One object of this invention provides for biocide-polyester concentrates useful for later incorporation into polymer substrates. Another object of this invention provides for biocidally active polymer compositions resistant to discoloration made by the incorporation of said biocide-polyester concentrate into the polymer. The instant invention pertains to a biocide-polyester concentrate which consists of (A) 1-75% by weight of a biocide selected from the group consisting of (a) 2,4,4'-trichloro-2'-hydroxydiphenyl ether (Irgasan® or Irgaguard®, Ciba Specialty Chemicals Corp.); (b) methylene-dithiocyanate,2-N-octyl-4-isothiazolin-3-one, 3,5-dimethyl-tetra-hydro-1,3,5-2H-thiodiazine-2-thione; (c) 2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine (Irgarol® 1051, Ciba Specialty Chemicals Corp.); (d) copper sulfate, copper nitrate or copper-bis(8-hydroxyquinoline); (e) tributyltin oxide; and (f) silver and zinc compounds or oxy-bis-phenoxyarsine; and (B) 99-25% by weight of a polyester carrier resin. Preferably, component (A) is 10-50% by weight of a biocide, and component (B) is 90-50% by weight of a polyester carrier resin. An especially preferred biocide (A) is 2,4,4'-trichloro-2'-hydroxydiphenyl ether. The polyester carrier resin (B) is a homopolyester or a copolyester prepared from aliphatic, cycloaliphatic or aromatic dicarboxylic acids and diols or hydroxycarboxylic acids. Preferably, the polyester of component (B) has dicarboxylic acid repeat units selected from the group consisting of aromatic dicarboxylic acids having 8 to 14 carbon atoms, aliphatic dicarboxylic acids having 2 to 40 carbon atoms, cycloaliphatic dicarboxylic acids having 6 to 10 carbon atoms, aliphatic hydroxycarboxylic acids having 2 to 12 carbon atoms, aromatic and cycloaliphatic hydroxycarboxylic acids having 7 to 14 carbon atoms, and mixtures thereof. Preferably such aromatic diacids are terephthalic acid, isophthalic acid, o-phthalic acid, 1,3-, 1,4-, 2,6- and 2,7-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, di(4-carboxyphenyl) sulfone, 4,4'-benzophenonedicarboxylic acid, 1,1,3-trimethyl-5-carboxy-3-(p-carboxyphenyl)indane, di(4-carboxyphenyl) ether, bis(p-carboxyphenyl)methane and bis(p-carboxyphenyl)ethane. Most preferably, the aromatic diacids are terephthalic acid, isophthalic acid and 2,6-naphthalenedicarboxylic acid. Suitable aliphatic dicarboxylic acids are linear or branched. Preferably such aliphatic dicarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, trimethyladipic acid, sebacic acid, azelaic acid and dimeric acids (products of the dimerization of unsaturated, aliphatic acids such as oleic acid), alkylated malonic acid, alkylated succinic acid, and mixtures thereof. Suitable cycloaliphatic dicarboxylic acids are 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3- and 1,4-cyclohexanedicarboxylic acid, 1,3- and 1,4-(dicarboxymethyl)cyclohexane and 4,4'-dicyclohexyldicarboxylic acid. The diol or glycol portion of the polyester of component (B) are derived from the generic formula HO-R-OH where R is an aliphatic, cycloaliphatic or aromatic moiety of 2 to 18 carbon atoms. Preferably such diols or glycols are ethylene glycol, diethylene glycol, triethylene glycol, 1,2-and 1,3- propane-diol, 1,2-, 1,3-, 2,3- and 1,4-butane-diol, pentane-1,5-diol, neopentane glycol, hexane-1,6-diol, dodecane-1,12-diol, 1,4-cyclohexanedimethanol, 3-methylpentane-2,4-diol, 2-methylpentane-1,4-diol, 2,2-diethylpropane-1,3-diol, 1,4-di-(hydroxyethoxy)benzene, 2,2-bis(4-hydroxycyclohexyl)-propane, 2,4-dihydroxy-1,1,3,3-tetramethylcyclobutane, 2,2-bis-(3-hydroxyethoxyphenyl)propane, 2,2-bis-(4-hydroxypropoxyphenyl)ethane, 1,4-dihydroxycyclohexane, p-xylylene glycol, poly(ethylene glycol), poly(propylene glycol), and mixtures thereof. Preferably, the diol is 1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol, ethylene glycol, 1,4-butanediol, 1,2-propylene glycol and 1,3-trimethylene glycol. Most preferably, the diol is ethylene glycol. It is furthermore possible for the polyester to be branched by small amounts, for example 0.1 to 3 mol %, based on the dicarboxylic acid present, of monomers having a functionality greater than two, e.g. pentaerythritol, trimellitic acid, 1,3,5-tri(hydroxyphenyl)benzene, 2,4-dihydroxybenzoic acid or 2-(4-hydroxyphenyl-2-(2,4-dihydroxyphenyl)propane. In the polyester comprising at least two monomers, the polymer can have randomly distributed units or units arranged in the form of blocks. The polyester of component (B) is preferably poly(ethylene terephthalate) PET, poly(ethylene 2,6-naphthalene-2,6-dicarboxylate) PEN or poly(ethylene/1,4-cyclohexylenedimethylene terephthalate) PETG copolyester, EASTAR® 6763 (Eastman Chemical); most preferably, poly(ethylene terephthalate) or the poly(ethylene/1,4-cyclohexylenedimethylene terephthalate) copolyester. It is also contemplated that the polyester of component (B) can also be a blend of polyesters or copolyesters including components mentioned above. The instant invention also pertains to biocidally active polymer compositions resistant to discoloration which comprises (I) a polymer substrate, and (II) an effective biocidal amount of a concentrate described above. The effective biocidal amount of the active component is for example 0.01 to 5% by weight based on the total composition. The polymer substrate of component (I) is for example a polyolefin, polystyrene, a polyamide (a nylon), a polycarbonate, a polystyrenic such as ABS, SAN or ASA; a polyurethane, an acrylate, a polyacrylonitrile, a rubber modified styrenic, poly(vinyl chloride), poly(vinyl butyral) or a polyacetal (polyoxymethylene). Preferably, the polymer substrate is a polyolefin or a polystyrenic, especially polypropylene or polyethylene, most especially linear low density polyethylene (LLDPE), low density polyethylene (LDPE) or high density polyethylene (HDPE). The instant invention also relates to a process for preparing a biocidally active polymer composition, which is resistant to discoloration, which comprises incorporating into said polymer an effective biocidal amount of a biocide-polyester concentrate as described above. The incorporation of the instant biocide-polyester concentrate into the polymer substrate affords a number of real advantages over using a neat biocide for the same purpose. These advantages are better handling; improved industrial hygiene and environmental concerns; and improved control of dosing accuracy for insertion of biocide into the polymer substrate. Most of all and surprising is the advantage that the use of the biocide-polyester concentrate, when added to a variety of polymer substrates, leads to resistance to discoloration in the biocidally active polymer substrate as compared to the incorporation of neat biocide directly into the polymer substrate. The instant invention relates therefore also to a process for stabilizing a biocidally active polymer against discoloration which comprises incorporating into said polymer an effective biocidal amount of a biocide-polyester concentrate as described above. A preferred embodiment of the present invention is the use of a biocide-polyester concentrate as described above for stabilizing a polymer substrate against discoloration. The following examples are meant for illustrative purposes only and are not to be construed to limit the scope of the instant invention in any way whatsoever. Example 1 : Preparation of biocide-polyester concentrate. A commercial poly(ethylene/1,4-cyclohexylenedimethylene terephthalate) PETG copolyester (Eastar®6763, Eastman Chemical), is predried in vacuo under nitrogen in an oven at about 70°C to a moisture level of about 30 ppm as verified on a Mitsubishi VA-06 moisturemeter. 75 Parts by weight of this dried resin is dry blended with 25 parts by weight of 2,4,4'-trichloro-2'-hydroxydiphenyl ether (Irgasan® or Irgaguard®, Ciba Specialty Chemicals Corp.). The blended resin is then melt compounded under nitrogen into pellets at 180°C using a Leistritz extruder with corotating, non-intermeshing twin screw at 100 rpm. Example 2 : Prepartion of biocidally active composition using a biocide-polyester concentrate. 100 parts polypropylene homopolymer (Profax® 6501, Montell Polyolefins), stabilized with 0.05 parts of neopentanetetrayl tetrakis(3,5-di-tert-butyl-4-hydroxyhydrocinnamate), 0.10 parts of tris(2,4-di-tert-butylphenyl) phosphite and 0.05 parts of calcium stearate is dry blended without a biocide; or with 0.25 parts or with 0.50 parts of 2,4,4'-trichloro-2'-hydroxydiphenyl ether (Irgasan® or Irgaguard®, Ciba Specialty Chemicals Corp.) either as a neat powder or as a concentrate as prepared in Example 1. The parts of components are by weight. These various mixtures are melt compounded in one, two and three passes at two different temperatures (260°C and 288°C) in a Superior/MPM extruder using a 24:1 L/D screw with a Maddock mixing head at 80 rpm. The extruded pellets are compression molded into 125 mil plaques (5.08 cm x 5.08 cm) at 232°C for nine minutes (three minutes at low pressure; three minutes at high pressure; three minutes cooling). Yellowness Index (Yl) values are determined on the plaques according to ASTM D1925 on a DCI SF600 spectrophotometer. A low Yellowness Index value denotes little discoloration, a high Yellowness Index value denotes severe discoloration of the samples. The results are summarized in Tables 1 and 2. Example Biocide (% by weight) Yellowness Index (YI) after multiple pass extrusion at 260°C First Second Third 2a a) ― 7.8 9.4 14.5 2b a) 0.25 % Powder 8.4 8.8 9.7 2c a) 0.50 % Powder 8.8 9.7 9.2 2d b) 0.25 % Concentrate -0.4 -2.0 -0.6 2e b) 0.50 % Concentrate -0.1 -0.2 0.0 Example Biocide (% by weight) Yellowness Index (YI) after multiple pass extrusion at 288°C First Second Third 2f ― 10.4 11.9 10.4 2g 0.25 % Powder 6.4 6.3 6.6 2h 0.50 % Powder 7.1 7.2 7.4 2i 0.25 % Concentrate 0.3 -2.3 -0.7 2k 0.50 % Concentrate -1.8 -1.1 0.5 These results clearly show that the plaques which contain the biocide incorporated therein using the concentrate are far superior in color performance (much lower YI values) than the plaques containing the same concentration of biocide added as a neat powder. Example 3 : Prepartion of biocidally active composition comparing a biocide-polyester concentrate with a biocide-polyethylene concentrate. Following the general procedure of Example 1, a concentrate of 10 % by weight of 2,4,4'-trichloro-2'-hydroxydiphenyl ether (Irgasan® or Irgaguard®, Ciba Specialty Chemicals Corp.) is prepared in low density polyethylene. Following the general procedure of Example 2, polypropylene homopolymer (100 parts) mixtures without biocide; and with 0.25 and 0.50 parts of the biocide-polyethylene concentrate made above; and with 0.25 and 0.50 parts of the biocide-polyester concentrate made in Example 1. The parts of components are by weight. These mixtures are melt compounded in three passes at 288°C as seen in Example 2. The extruded pellets are compression molded and the Yellowness index (Yl) values are determined according to ASTM D1925 on a DCI SF600 spectrophotometer. A low Yellowness Index value denotes little discoloration, a high Yellowness Index value denotes severe discoloration of the samples. The results are summarized in Table 3. Example Biocide (% by weight) Yellowness Index (YI) after multiple pass extrusion at 288°C First Second Third 3a ― 8.9 8.8 12.5 3b 0.25 % Polyethylene concentrate 5.6 n.m. 5.0 3c 0.50 % Polyethylene concentrate 9.3 11.8 10.6 3d 0.25 % Polyester concentrate 0.3 n.m 1.3 3e 0.50 % Polyester concentrate 1.2 1.0 1.5 The results disclosed in Table 3 show a far superior performance with regard to color stability of the plaques prepared with the biocide-polyester concentrate as compared to the plaques prepared with the biocide-polyethylene concentrate.

Claims: A biocide-polyester concentrate which consists of (A) 1-75% by weight of a biocide selected from the group consisting of (a) 2,4,4'-trichloro-2'-hydroxydiphenyl ether; (b) methylene-dithiocyanate, 2-N-octyl-4-isothiazolin-3-one, 3,5-dimethyl-tetra-hydro-1,3,5-2H-thiodiazine-2-throne; (c) 2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine; (d) copper sulfate, copper nitrate or copper-bis(8-hydroxyquinoline); (e) tributyltin oxide; and (f) silver and zinc compounds or oxy-bis-phenoxyarsine; and (B) 99-25% by weight of a polyester carrier resin. A biocide-polyester concentrate according to claim 1 wherein component (A) is 10-50% by weight of a biocide, and component (B) is 90-50% by weight of a polyester carrier resin. A biocide-polyester concentrate according to claim 1 wherein the biocide of component (A) is 2,4,4'-trichloro-2'-hydroxydiphenyl ether. A biocide-polyester concentrate according to claim 1 wherein the polyester carrier resin (B) is a homopolyester or a copolyester prepared from aliphatic, cycloaliphatic or aromatic dicarboxylic acids and diols or hydroxycarboxylic acids. A biocide-polyester concentrate according to claim 4 wherein the dicarboxylic acid is terephthalic acid, isophthalic acid or 2,6-naphthalenedicarboxylic acid. A biocide-polyester concentrate according to claim 4 wherein the diol is 1,4-dihydroxycyclohexane, 1,4-cyclohexanedimethanol, ethylene glycol, 1,4-butanediol, 1,2-propylene glycol or 1,3-trimethylene glycol. A biocidally active polymer composition resistant to discoloration which comprises (I) a polymer substrate, and (II) an effective biocidal amount of a biocide-polyester concentrate according to claim 1. A composition according to claim 7 where the effective biocidal amount of the active component is 0.01 to 5% by weight based on the total composition. A composition according to claim 7 wherein the polymer substrate of component (I) is a polyolefin, polystyrene, a polyamide, a polycarbonate, a polystyrenic, a polyurethane, an acrylate, a polyacrylonitrile, a rubber modified styrenic, poly(vinyl chloride), poly(vinyl butyral) or a polyacetal (polyoxymethylene). A composition according to claim 7 wherein the polymer substrate is a polyolefin or a polystyrenic. A process for stabilizing a biocidally active polymer against discoloration which comprises incorporating into said polymer an effective biocidal amount of a biocide-polyester concentrate according to claim 1. The use of a biocide-polyester concentrate according to claim 1 for stabilizing a polymer substrate against discoloration.

Inventors: STADLER URS LEO, STADLER, URS LEO
Applicants: CIBA SC HOLDING AG, CIBA SPECIALTY CHEMICALS HOLDING INC.
Application year: 2000
Main classification: A01N25
IPC codes: A01N31, C08L67, C08L101, A01N61, C08K5, A01N25, C08J3