Composition and Process for Making a Green Colored Polyester

The present invention relates to a green colored polyester made using specific color-imparting compounds.

Heretofore, various desired colors have been imparted to items, for example, glass, paint, paper, etc., through the use of various minerals, pigments, inks, and the like. However, to impart a color, for example, green, to a polyester which can be made into a container, e.g., a bottle, for containing liquids or solids as for human consumption, requires that specific safe color-imparting compounds be used. Furthermore, the pigments or catalysts must not adversely affect the properties of the polymer.

U.S. Pat. No. 3,127,375 to Keck relates to the use of columbium (now called niobium) compounds as catalysts for ester interchange reactions between glycols and esters of polycarboxylic acids or mixtures of esters of such acids. The patent states that a polyester is formed which has good color, that is freedom from discoloration, and the examples state the melt color is yellow.

U.S. Pat. No. 3,758,438 to Freitag relates to the utilization of niobium as in the form of niobium pentoxide to impart a golden hue to the polyester.

Neither of these patents, however, suggest the production of a green colored polyester, or of the utilization of the niobium catalysts with titanium pigments or catalysts together with phthalocyanine blue to obtain a green color.

It is therefore an object of the present invention to provide a polyester resin having a green color.

It is yet another object of the present invention to provide a green colored polyester resin wherein the color can be imparted to any known polyester and wherein any known or conventional process for making the polyester is utilized.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein said resin is made according to a melt state polymerization, or in combination with a subsequent solid state polymerization.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein said polyester has a slight yellowish tinge.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein the color imparting compounds are added during the esterification and/or the polycondensation stage of the polymerization. It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein a niobium catalyst is used as a color imparting compound.

It is yet another object of the present invention to provide a green colored polyester resin, as above, in which a titanium catalyst is utilized.

It is yet another object of the present invention to provide a green colored polyester resin, as above, in which a phthalocyanine blue pigment is also utilized.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein said resin is poly(ethylene terephthalate) (PET) prepared by conventional methods from dimethylterephthalate or terephthalic acid with ethylene glycol.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein said resin can be utilized to replace glass in the making of bottles and other containers.

It is yet another object of the present invention to provide a green colored polyester resin, as above, wherein said resin is suitable for beverage bottles.

These and other objects of the present invention will become apparent from the following description of the invention.

In general, in a polyester article, the improvement comprises: a small amount of color-imparting compounds contained in a polyester for imparting a green color thereto; said color-imparting compounds comprising a niobium catalyst, and a blue pigment; the proportion of said compounds being sufficient to effect a green color.

Additionally, a green colored polyester resin, comprises: color-imparting compounds dispersed in the polyester resin, said compounds being a niobium compound and a blue pigment, the amount of said compounds being such so that a green color is imparted to said polyester resin.

In general, a process for making a polyester resin having a green color, comprises the steps of: preparing a polyester resin; adding a niobium compound to said polyester resin during preparation thereof; adding a blue pigment to said polyester resin during preparation thereof; and imparting a green color to said resin by utilizing sufficient amounts of said niobium compound, and said blue pigment.

According to the concepts of the present invention, a green colored polyester resin suitable for the production of containers, packages, etc., and especially for carbonated beverages, is produced. The polyesters to which a green color can be imparted are conventional or known polyesters made according to conventional or known methods, processes and the like. Generally, such polyesters include polymers formed from dicarboxylic acids containing a total of from 2 to 16 carbon atoms reacted with polyhydric alcohols such as gylcols or diols containing from 2 to 12 carbon atoms. The alkyl dicarboxylic acids may contain a total of from 2 to 16 carbon atoms. Preferably, the acids are aryl or an alkyl substituted aryl acid containing from 8 to 16 carbon atoms. Specific examples of linear or alkyl dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and the like. Specific examples of an aryl acid include the various isomers of phthalic acid, such as paraphthalic acid (terephthalic acid) and naphthalic acid. Specific examples of alkyl substituted aryl acids include the various isomers of dimethylphthalic acid such as dimethylisophthalic acid, dimethylorthophthalic acid, dimethylterephthalic acid, the various isomers of diethylphthalic acid such as diethylisophthalic acid, diethylorthophthalic acid, diethylterephthalic acid, the various isomers of dimethylnaphthalic acid such as 2,6-dimethylnaphthalic acid and 2,5-dimethylnaphthalic acid, and the various isomers of diethylnaphthalic acid. Generally, terephthalic acid is highly preferred.

It is well known to those skilled in the art, in lieu of the various dicarboxylic acids, the various diesters thereof may be utilized. Thus, alkyl diesters containing a total of from 2 to about 20 carbon atoms as well as alkyl substituted aryl diesters containing from about 10 to about 20 carbon atoms may be utilized. Examples of diesters include the diesters of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, or sebacic acid, and the like. Specific examples of various alkyl esters of di acids include the various isomers of dimethylphthalate such as dimethylterephthalate, a preferred compound, the various isomers of diethylphthalate, the various isomers of dimethylnaphthalate, and the various isomers of diethylnaphthalate.

The diols or glycols may be straight chained or branched. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, 1,2-butane diol, 1,3-butane diol, 1,4-butane diol, 2,3-butane diol, neopentyl glycol, and the like. Of the various glycols, those having from 2 to 8 carbon atoms are preferred with ethylene glycol and 1,4-butane diol being highly preferred. In lieu of the various glycols, another class of polyhydric alcohols, such as the glycol ethers containing from 4 to 12 carbon atoms, can be utilized as for example dimethylene glycol and 1,4-dihydroxyethoxy benzene.

The polyesters can be made according to melt polymerization, or melt and solid state polymerization. As known to those skilled in the art, polyesters are generally made in two stages. In the first stage or esterification stage, the diacid is reacted with the diol at elevated temperatures and pressures with water being produced. In the second stage or the polycondensation stage, a vacuum is gradually applied, generally catalysts are utilized, and water and a diol are withdrawn as a condensation product. Various polyesters can be made by such a polymerization including poly(ethylene terephthalate), a preferred polyester resin. Moreover, the process may be modified slightly by reacting the dicarboxylic acid with the diol in a solvent which is a low molecular weight linear polyester in a manner as set forth in U.S. Pat. No. 4,020,049 to Rinehart, which is hereby fully incorporated with regard to the method of making the polyester resin. Another well known variation utilizes dimethylterephthalate which is reacted with ethylene glycol in the presence of a catalyst with a transesterification reaction yielding a bishydroxyethylterephthalate compound. A stabilizer may then be added as well as a catalyst and a polycondensation reaction is carried out to yield a polyester. Regardless of the exact process, such reactions can be carried out in situ.

Solid state polymerization can also be utilized. In this process, the polycondensation product is carried out until generally the intrinsic viscosity of the polymer melt reaches about 0.20 or higher, for example, up to about 0.80. At this point, the melt is cooled to produce a solid which is then pelletized, chopped, etc. The pellets are then subjected to a solid state polymerization wherein the vacuum is applied at a temperature below the melting point of the partially formed polymer. Thus, the polymer is actually polymerized in a solid state, with the polycondensation reaction being continued in such a state. Generally, the solid state polymerization is continued until the intrinsic viscosity reaches any desirable level, such as from about 0.60 to about 1.0, or even higher. Desirably, the intrinsic viscosity ranges from about 0.70 to about 0.85 and preferably from about 0.70 to about 0.80. By intrinsic viscosity it is meant that the value obtained when n.sub.specific /C or LOG n.sub.rel. /C is extrapolated to zero concentration; where the relative viscosity is defined as the quotient of the solution viscosity, n.sub.soln. and the viscosity of the solvent n.sub.solv., i.e., ##EQU1## The specific viscosity n.sub.sp. =n.sub.rel. -1. The units are deciliters/gram using a 60/40 phenol/tetrachloroethane at 25.degree. C. The symbol n is for the Greek letter eta.

When the polyester resin is intended for use in contact with food, only those polyesters which are regulated by the Federal Food and Drug Administration should be utilized, such as set forth in Title 21, .sctn.177.1630, for example, the polyethylenephthalate polymers, and such polyesters are preferred in the present invention.

A green colored polyester resin is produced by utilizing specific color-imparting compounds to produce the green color. Specifically, a yellow color-imparting compound is utilized with a blue compound to yield an intermediate green color. The resin color is measured by a Gardner Colormeter, or a Hunter Lab instrument is utilized for beverage bottle measurements. The Gardner meter utilizes reflectance (Rd) values as a measure of brightness, whereas the Hunter instrument utilizes luminance (L) for this measurement. The color hue is defined in either case by (a) or (b) values. Positive (a) coordinates (that is, an X axis) measures redness whereas Negative (a) values indicate greenness. Positive (b) (that is, positive Y coordinates) define yellowness whereas negative (b) values indicate blueness. The brightness (reflectance or luminance) of the sample is required as a point from 0 (black) to 100 (white) using both instruments. These measurements enable an approximation of the visual color used in the instrument coordinates. The measured (a) and (b) values therefore place a resin or a bottle made from the resin in one of the colored quadrants formed by their axes. In an anti-clockwise direction, starting at the three o'clock position, the first quadrant is red/yellow, the second quadrant is yellow/green, the third quadrant is green/blue, and the fourth quadrant is blue/red. The color green of the present invention is in the second quadrant, that is basically a green compound with a yellow tinge thereto.

Regardless of the type (that is, chemical formulation) of polyester or the process utilized, a green color is imparted to the polyester by utilizing specific color-imparting compounds. The compounds which are utilized include iron catalysts, titanium catalysts and a blue pigment. Additionally, the polyester can contain conventional additives such as stabilizers, antioxidants, and the like.

Considering first the iron compound, it is generally an iron salt including the various hydrates thereof, which thermally decomposes during the polymerization process to produce an iron oxide, that is, alpha-Fe.sub.2 O.sub.3. Alpha-Fe.sub.2 O.sub.3 has a yellow color. It is to be understood that whenever the term "iron salt" is used in this specification, it includes the various hydrates thereof. The iron salt serves as a catalyst during the polycondensation step and may be added preferably during such step or may be added initially, as during the esterification step. As noted, during the polymerization, the salt is thermally decomposed to an iron oxide compound. Such iron oxide compound serves as a yellow pigment. The polymerization temperature is a temperature to cause the iron salt or catalyst compound to thermally decompose, as for example, 250.degree. C. or greater, or preferably 270.degree. C. or greater. The iron salt is a true catalyst in that it can often completely replace the polycondensation catalyst normally utilized. Specific examples of iron salts include ferric nitrate, that is Fe(NO.sub.3).sub.3.9H.sub.2 O, ferric citrate such as FeC.sub.6 H.sub.5 O.sub.7.3H.sub.2 O, ferric acetylacetonate, ferric ammonium citrate, ferrous sulfate such as FeSO.sub.4.7H.sub. 2 O, ferric sulfate such as Fe.sub.2 (SO.sub.4).sub.3.6H.sub.2 O, ferrous chloride such as FeCl.sub.2.4H.sub.2 O, and ferric chloride such as FeCl.sub.3.H.sub.2 O. Of these specific compounds, ferric nitrate is preferred. Additionally, a preformed ferric oxide which gives good dispersion can also be utilized. Based upon the weight of the final polyester resin produced, the amount of iron salt-catalyst as iron (Fe) ranges from about 50 to about 300 parts by weight per million parts, desirably from about 80 to about 150 parts, and optimally is about 100 parts.

The titanium catalysts can be alkyl esters having from 3 to 10 carbon atoms, or titanium chelates having from 4 to 50 carbon atoms with from 6 to 32 carbon atoms being preferred. The titanium catalysts act as a polycondensation catalyst as well as influence the yellow shade (reddening effect) produced by the iron. Of the numerous titanates which may be utilized, the following are desirable, titanium triethanolamine, titanium acetyl acetonate, tetrabutyl titanate, tetraisopropyl titanate, and titanium glycolate. Examples of suitable titanium chelates include titanium acetyl acetonate, triethanolamine titanium chelate, lactic acid titanium chelate, tetraoctylene glycol chelate, and the like. The first two chelates are often referred to as titanium alkyl esters and thus have also been previously listed as such. A specific source of chelates are by the DuPont Co. under the name "TYZOR". Of the various titanium compounds, titanium acetyl acetonate is preferred with titanium triethanolamine being highly preferred. The amount of the titanium catalysts as titanium (Ti), based upon one million parts by weight of the final amount of polyester resin produced generally ranges from about 2 parts to about 250 parts, with from about 50 to about 150 parts being desirable and approximately 100 parts by weight being preferred. The titanium catalysts can be added during the esterification or polycondensation stage.

A blue pigment is utilized so that in combination with the yellow iron oxide compound produced and the titanium catalysts, an intermediate color, green or green with a yellow tinge, is produced. That is, the green color desired for the present invention resides within the second above-noted color quadrant. Based upon the (a) and (b) coordinates, the color utilizing a one-eighth inch solid state resin cube having a density of approximately 1.4 grams per cc is as follows. Gardner values of from about minus 5 to about minus 20 and preferably from about minus 9 to about minus 15 on the (a) scale, and from about 1 to about 10 and preferably from about 2 to about 5 on the (b) scale or coordinate. The Hunter value ranges from about minus 5 to about minus 25 and preferably from about minus 10 to about minus 18 on the (a) coordinate and from about 1 to about 10 and preferably from about 2 to about 5 on the (b) coordinate. When a bottle is produced, the Hunter values range from about minus 5 to about minus 30 and preferably from about minus 14 to about minus 25 on the (a) coordinate and from about 1 to about 15 and preferably from about 5 to about 15 on the (b) coordinate. Thus, essentially a green color is produced or more exactly, a green color having a yellow tinge thereto.

The blue pigment which is utilized can be any blue pigment which produces, in combination with the other catalysts, the desired green color. Desirably, a pigment blue number 15 is desired, that is C.I. (color index number) of 74160. A specific example of the blue pigment which is preferably added during the esterification stage, but it can also be added during the polycondensation stage, is phthalocyanine blue. Phthalocyanine blue is commercially available from many suppliers such as Paliofast Blue manufactured by BASF, or as Monastral Blue, manufactured by DuPont. The amount of phthalocyanine blue utilized per million parts of the final polyester resin produced ranges from about 20 to about 100 parts by weight, with a preferred range being from about 30 to about 50 parts by weight.

The polyester resins of the present invention can be utilized in various conventional process apparatus such as calenders, injection molding machines, blow molding machines, extrusion machines, and the like, to produce any desired article which has a green color thereto. A particular area of use is a container area, such as bottles, and more particularly beverage bottles, for example soft drink bottles.

The invention will be better understood by reference to the following examples.

Green PET resins have been prepared according to the invention via batch processes (although continuous processes can also be utilized) in amounts ranging from about 50 grams to about 1,500 or 2,000 pounds. In the following examples, the iron and titanium catalyst level used are indicated by parts per million of Fe or Ti by weight of PET. The phthalocyanine blue pigment amount used is also in parts per million by weight of PET.

The appropriate amounts of phthalocyanine blue is slurried in ethylene glycol and added to a low molecular weight oligomeric mixture of PET at 270.degree.-290.degree. C. in a manner as set forth in U.S. Pat. No. 4,020,049 to Rinehart. A portion of this esterified product mixture is transformed to another vessel where separately prepared solutions of ferric nitrate and Tyzor TE (titanium triethanolamine) and ethylene glycol are added. The pressure of the vessel is gradually reduced to less than 1 millimeter of mercury to polycondense the mixture to a green PET with the desired molecular weight (I.V.). A solid state polymerization is then carried out to yield a desired I.V. resin for conversion to carbonated beverage bottles. The amounts of the various compounds as well as the color is set forth in Table I.

As apparent from the above table, the bottle tends to have a slightly different color than the solid state resin. This is due to the fact that the bottle thickness is generally thinner and the resin is opaque and thus imparts a different color. In any event, a suitable end color can be readily achieved.

According to the present invention, niobium catalysts can be used in lieu of iron to produce a polyester resin having a green color. That is, the polyester contains a mixture of niobium catalysts and a phthalocyanine blue pigment, and optionally a titanium catalyst.

With regard to the blue pigment, the compound is the same as that set forth above. Additionally, the amount of phthalocyanine blue utilized per million parts of the final polyester resin ranges from about 20 to about 100 parts by weight, with a preferred range being from about 30 to about 70 parts by weight.

The titanium catalysts are the same as set forth above. However, their range when utilized in association with the niobium and phthalocyanine blue compounds is from about 5 to about 150 parts by weight of elemental titanium per million parts of polyester and preferably from about 10 to about 50 parts. As before, the titanium catalyst can be added during either the esterification or polycondensation stage. Although the use of a titanium catalyst is optional, it is generally preferred that such a compound be utilized, especially in solid state polymerizations.

A niobium catalyst is utilized in lieu of an iron salt to produce a generally yellow shade which, in combination with a phthalocyanine blue compound and the optional titanium compound yields a green color. Generally, any niobium compounds, which is somewhat soluble in the polyester melt, can be utilized. Specific examples include, in order of decreasing solubility, niobium penta-hydrogen oxalate, Nb(HC.sub.2 O.sub.4).sub.5 ; niobium oxalate, H[NbO(C.sub.2 O.sub.4).sub.2 ]5H.sub.2 O+H.sub.3 Nb (C.sub.2 O.sub.4).sub.4 ; hydrated niobium pentoxide having at least 5 percent by weight of water, desirably greater than 50 percent, and preferably from about 80 to about 90 water by weight; and calcined niobium pentoxide, Nb.sub.2 O.sub.5. Since the niobium compounds tend to be costly, the less costly compounds are desired. Accordingly, niobium penta-hydrogen oxalate is desired with niobium oxalate and hydrated niobium pentoxide being preferred. The amount of the niobium compounds by weight of elemental niobium ranges from about 5 to about 150 parts by weight per one million parts by weight of the final polyester resin produced, and preferably from about 20 to about 50 parts per million.

The various niobium compounds are readily available and can be purchased from commercial sources. Thus, for example, niobium penta-hydrogen oxalate can be purchased from Gallard-Schlesinger, Inc.; niobium oxalate is manufactured by Kawecki Berylco Industries, as well as Gallard-Schlesinger; the hydrated niobium pentoxide is manufactured by Teledyne Wah Chang Albany; and the calcined niobium pentoxide is produced by Kawecki. The niobium can be added during either the esterification stage or the condensation stage.

As before, the green color desired for the present invention, based upon (a) and (b) coordinates, resides within the second quadrant. Utilizing the Gardner scale for a feed polymer or melt polymer, the Rd value ranges from about 2 to about 12, with a value of from about 3 to about 8 being preferred. The (a) coordinate ranges from about minus 8 to about minus 25, with from about minus 11 to about minus 20 being preferred. The (b) coordinate ranges from about 2 to about 10 with a value of from about 5 to about 8 being preferred. The solid state has Gardner values as follows: Rd of 10 to about 30, with from about 18 to 25 being preferred, (a) coordinate values of from about minus 15 to about minus 30, with from about minus 18 to about minus 25 being preferred; and (b) coordinate value of from about 3 to about 12, with from about 5 to about 9 being preferred. The Hunter values for the solid state material are an L value of from about 35 to about 50, with from about 40 to 50 being preferred, and (a) value of from about minus 16 to about minus 26 or from about minus 20 to about minus 25 being preferred, and a (b) coordinate value of from about 1 to 8, with from about 1.5 to about 6 being preferred. Thus, a green color is produced, or more exactly a green color having somewhat of a yellow tinge thereto. The Gardner and Hunter values are for 1/8 inch cubes of feed or solid state resin. It is noted that these values may change for different sized cubes. The polyester resins of the present invention are utilized in various conventional process apparatus as noted above, with a particular area of use being the container area such as bottles, more particularly beverage bottles, for example soft drink bottles. The Hunter values for a standard 2 liter bottle are an L value of from about 60 to about 85, with from about 70 to about 80 being preferred; an (a) coordinate value of from about minus 10 to about minus 40, with a value of from about 20 to about minus 35 being preferred; and a (b) coordinate value of from about 1 to about 15, with a value of from about 2 to about 9 being preferred. The invention will be better understood by reference to the following examples.

Generally, the preparation of the resin was the same as set forth above with regard to the iron example. That is, the amount of phthalocyanine blue as set forth in Table II was slurried in ethylene glycol and added to a low molecular weight oligomeric mixture of PET at 270.degree.-290.degree. in a manner as set forth in U.S. Pat. No. 4,020,049 to Rinehart. Additionally, the amount of niobium, based upon the elemental content, was added as niobium oxalate (from Kawecki Berylco) in the form of a glycol solution. The solution was then esterified. A portion of the esterified product mixture was transformed to another vessel where an optional amount of Tyzor TE (titanium triethanolamine) and ethylene glycol was added. The pressure of the vessel was gradually reduced to less than 1 millimeter of mercury to polycondense the mixture to a green PET with the desired molecular weight (I.V.). Alternatively, solid state polymerization was then carried out to yield a desired I.V. resin for conversion to carbonated beverage bottles. The amount of the various compounds as well as the color is set forth in Table II.

Table II reveals the fact that a green color is produced with a slight yellow tinge. All examples generally have the same color although B and C tend to be more economical.

While having described the best mode as well as the preferred embodiments of the present invention, in accordance with the patent statutes, it is noted that the invention is not limited thereto, the scope of the invention being measured by the attached claims.