HK1040391B - Aromatic acid monomers, polymers, products and processes for their manufacture - Google Patents

Description

Aromatic acid monomers, polymers, products and processes for making them

RELATED APPLICATIONS

The present application claims the benefit of U.S. provisional patent application No.60/138,344 entitled "aromatic acid monomers, polymers, products, and methods for making them" filed on 9.6.1999 and U.S. provisional patent application No.60/103,393 entitled "aromatic acid monomers, polymers, products, and methods for making them" filed on 7.10.1998.

Technical Field

This invention relates generally to polymers formed from aromatic acid monomers, and more particularly, this invention relates to aromatic acid monomers containing small amounts of materials that provide unexpected advantages during polymerization or copolymerization of these acidic monomers, and to processes for preparing such aromatic acid monomers and polymers.

Background

The preparation of aromatic acids for use as monomers is generally a complex, multi-step process. For example, 2, 6-naphthalenedicarboxylic acid (2, 6-NDA) can be prepared by a five-step synthesis process comprising the steps of reacting o-xylene with butadiene in an olefination reaction to produce 5-o-tolylpentene, cyclizing the 5-o-tolylpentene to form 1, 5-dimethyltetralin (1, 5-DMT), dehydrogenating the 1, 5-DMT to produce 1, 5-dimethylnaphthalene (1, 5-DMN), isomerizing the 1, 5-DMN to produce 2, 6-dimethylnaphthalene (2, 6-DMN), and oxidizing the 2, 6-DMN to produce 2, 6-NDA.

Crude NDA prepared by this method will contain a wide variety of process-related substances that are considered undesirable. Most of these materials are isomers of 2, 6-NDA or mono-or tri-functional reaction products. Other undesirable process-related materials contained in crude NDA are reactants such as metal catalysts throughout the various reaction steps, as well as colored materials formed during the reaction. The term "process-related materials" as used herein refers to any materials formed or added during any of the processing steps associated with the production of the aromatic acid monomer product, including, but not limited to, catalysts, side reaction products, undesired oxidation products, undesired isomers, and the like.

It is believed that in the preparation of polyesters from monomers such as NDA, monomer purity is critical in order to obtain high molecular weight polymers and sufficiently fast kinetic polymerization rates. For this reason, the preparation of polymers generally requires that monomer impurities such as mono-and trifunctional diols and carboxylic acids be minimized or removed from the monomers used in the polymerization reaction. For example, it is generally desirable that the terephthalic acid and isophthalic acid content is less than 200ppm or less based on the total weight of the monocarboxylic and tricarboxylic acids. Similarly, ethylene glycol used in polymerization reactions is generally expected to contain undetectable impurities.

Tricarboxylic acids are considered undesirable because such trifunctional compounds can cause undesirable crosslinking of the polymer chains. This crosslinking reportedly can lead to slow crystallization and polymer brittleness, both of which are undesirable in many applications. In addition, when crosslinking becomes severe, the "gel point" is approached. At this point the polymer cannot be melt polymerized or melt cast and is no longer considered a thermoplastic.

Monocarboxylic acids and other monofunctional species are considered undesirable components of the monomer because they act as "chain terminators", inhibiting molecular weight build-up, and because they reduce reaction kinetics. If the concentration of these substances is too high, the polymerization rate becomes zero due to the termination of other reactive end groups.

Various colored substances in the monomers are considered undesirable. The presence of the colored species in the monomer results in a color in the polymer that is much greater than the seemingly small amount of visible color in the monomer, and thus even a minute amount of colored species in the monomer is not desirable. The term "colored material" as used herein refers to any carboxylic acid present in the monomer or polymer that contains process-related materials that, when present in sufficient quantity, result in the monomer or polymer being colored.

Metals such as those produced by metal catalysts are also considered undesirable components of the monomer. For example, the resulting cobalt and manganese oxidation catalysts are considered undesirable monomer impurities because they can affect the polymerization rate and the color of the polymer in an unpredictable manner. These metals are also believed to sometimes affect the amount of color visible in the monomer or polymer.

Since the presence of undesired process-related substances such as by-products, reactants and impurities such as color substances in the monomer is believed to lead to a poor polymer product, the purity of the monomer such as 2, 6-NDA is greatly improved to provide a product quality deemed acceptable by the customer.

Pure aromatic acids have been prepared from crude aromatic acids, for example, by the following method; the material resulting from the crude aromatic acid oxidation process is slurried, the slurry is passed through a plurality of heaters until the reaction product is dissolved, the resulting solution is passed over a purification catalyst, and the purified product is then crystallized. This process requires more time and energy than the production of the crude aromatic acid, thus greatly increasing the cost of the monomer.

Alternatively, high purity monomers can be prepared from relatively high purity starting materials, such as hydrolysis of relatively pure 2, 6-naphthalenedicarboxylate (2, 6-NDC) to form relatively pure NDA. This process also adds cost because it is complicated and expensive to produce relatively pure NDC feedstock.

What is needed is a cost effective way to produce aromatic acids such as NDA suitable for polymer applications.

Brief description of the invention

We have surprisingly found that the presence of a certain amount of process-related substances in aromatic acid monomers can lead to performance comparable to or better than high purity aromatic acid monomers when used in many polymer applications.

In some applications, the presence of certain amounts of metal catalysts can result in faster polycondensation and solid state polymerization reactions, thereby improving the economics of these polymerization reactions without affecting the desired properties of the polymerization product.

In other applications, the presence of certain amounts of trifunctional species in the aromatic acid monomer product can provide branching of the polymer chains, thereby increasing melt strength, which is useful for making molded articles from the polymer.

In still other applications, the presence of certain amounts of metallic impurities and colored substances can impart a brownish character to the aromatic acid monomer, which is useful in packaging particular end use products, including, but not limited to, beverages such as beer in brown polymer bottles.

Whilst in some cases the aforementioned aromatic acid monomers may be directly obtained as a product as a solid isolated from the oxidation reaction product, typically the aromatic acid monomers of the present invention may be prepared by relatively simple work-up of the oxidised aromatic feedstock, for example by slurrying or washing the crude aromatic acid in a suitable solvent under suitable process conditions. The monomer products prepared in this manner are both low cost and have advantages in certain end use applications. Detailed description of the invention

The following detailed description of the preferred embodiments focuses on the advantages of the present invention in the preparation of 2, 6-naphthalenedicarboxylic acid monomer products and polymers prepared therefrom. As will be described in more detail later, the advantages of the present invention are also believed to be applicable to other aromatic acid monomers such as phthalic acid, terephthalic acid, and other isomers of naphthalene dicarboxylic acid.

As previously described, 2, 6-naphthalenedicarboxylic acid (2, 6-NDA) can be prepared by a five-step synthesis process comprising the steps of reacting o-xylene with butadiene in an olefination reaction to produce 5-o-tolylpentene, cyclizing the 5-o-tolylpentene to form 1, 5-dimethyltetralin (1, 5-DMT), dehydrogenating the 1, 5-DMT to produce 1, 5-dimethylnaphthalene (1, 5-DMN), isomerizing the 1, 5-DMN to produce 2, 6-dimethylnaphthalene (2, 6-DMN), and oxidizing the 2, 6-DMN to produce 2, 6-NDA. The aromatic feedstock, such as 2, 6-DMN that is oxidized in the process, preferably contains at least 97 mole percent of the feedstock that can be oxidized to acid, based on the mole percent of all aromatic species in the feedstock.

The crude 2, 6-DNA prepared by the above method preferably contains at least 90 mole%, more preferably at least 93 mole% of acid monomers, and is typically expected to contain unacceptable amounts of one or more of the following; trifunctional substances, 1-bromo-2, 6-DNA, 2-naphthoic acid, 6-formyl-2-naphthoic acid, cobalt, manganese, bromine, iron and various colored substances. We have found that the presence of certain amounts of metals, trifunctional compounds and coloured materials in the 2, 6-DNA monomer product used in the polymerisation reaction is generally not detrimental and in most cases advantageous. In most cases, acceptable and advantageous levels of these materials can be obtained by relatively simple processing of the oxidation product of 2, 6-DMN, thereby eliminating the need for costly purification steps such as recrystallization.

Acceptable and preferred levels of such materials suitable for the present invention are listed in table 1 below. The ppm ranges listed refer to ppm by weight of the material present in the NDA monomer product.

TABLE 1

Substance(s) Acceptable content level Preferred contentLevel of

Trifunctional material 50-10000150-8500

Monofunctional substance 50-5000150-3500

Metal (Co + Mn) 50-10000500-

50-50050-250 of colored substance

NDA monomers containing one or more of the foregoing materials in concentrations according to the invention can be prepared simply by, for example, slurrying the crude NDA oxidation product to remove a portion of these materials while leaving a suitable or at least non-hazardous portion of these materials in the monomer. The term "slurrying" as used herein refers to any process of washing or dispersing the crude oxidation product with a solvent, but specifically excludes any process, such as a recrystallization step, that is capable of dissolving greater than about 10 mole percent of the desired aromatic monomers present in the crude oxidation product. Other examples of "slurrying" processes according to the invention include using higher amounts of solvent volume in the reactor where the aromatic feedstock is oxidized to make the process-related materials more soluble, thereby partially reducing the amount of process-related materials present in the product, adding or increasing the volume of solvent in the crystallizer train of the oxidation process to reduce the presence of process-related materials by dilution, and washing with a solvent-containing filtrate to reduce the level of process-related materials remaining in the monomer product.

For example, crude 2, 6-naphthalenedicarboxylic acid can be recovered directly from the mother liquor of the oxidation of 2, 6-DMN. The crude 2, 6-NDA can then be redispersed or reslurried in a suitable solvent such as water, a low molecular weight carboxylic acid, or a mixture of water and a low molecular weight carboxylic acid in a weight ratio of about 0.1 to 1 part 2, 6-naphthalenedicarboxylic acid per part solvent. Preferred operating conditions for the repulping process include a temperature of 60 to 125 deg.C, more preferably 75 to 110 deg.C, and a pressure of about 0.5 to 3 atmospheres, more preferably 1 to 2 atmospheres. The ratio of solvent acid to water can vary from 100% acid to 100% water, with a preferred acid to water part ratio of about 90: 1 to 50: 50, and a most preferred range of about 80 parts acid and 20 parts water.

It is preferred that the solvent used to redisperse or repulp the 2, 6-naphthalenedicarboxylic acid in this manner is at least partially the process material or material derived from the process, such as the overhead concentrate of the oxidation reaction mixture. In this case, the solvent containing water and an acid such as acetic acid may be at least partially recycled back to the oxidation reactor. Alternatively, the solvent may be distilled and the low molecular weight carboxylic acid recovered for recycle to the oxidation reactor. The solvent may contain other process species, such as alcohols or acetates, produced during the process that do not substantially affect the slurry process or the properties of the monomer product. But such process material should contain little or no process-related materials that need to be reduced in the slurrying process.

The above-described slurry step provides relatively pure 2, 6-naphthalenedicarboxylic acid. In most cases, such 2, 6-NDA monomer products according to the invention are suitable or preferred for use in certain applications, whereas monomer products resulting from more complex processes require additional purification steps.

After this slurrying step, the 2, 6-naphthalenedicarboxylic acid may be separated from the solvent by any method known in the art for separating solids from the liquid phase, such as centrifugal filtration, or precipitation.

Of particular interest in repulped NDA are the concentration of catalyst metals, such as cobalt and manganese, the ratio of cobalt to manganese metals, the level of polyfunctional aromatic compounds, and the level of colored impurities.

The level and proportion of catalyst metal content is important not only because they will affect the rate of polymerization of the monomers, but also because their presence may in some cases affect the color of the final polymer. For NDA applications, the total amount of Co and Mn present in the repulped material should be no greater than about 10000ppm, preferably 500-2000ppm, and most preferably 1000-1500ppm by weight of the repulped product. The molar ratio of Co to Mn is in the range of 5: 1 to 0.2: 1, preferably in the range of 4: 1 to 0.25: 1, and most preferably in the range of 3: 1 to 0.5: 1.

The level of polyfunctional material is important when additional melt strength is required for the polymer prepared from the aromatic monomer. For NDA applications, the trifunctional naphthalene moiety in the mixture is the more likely moiety, primarily 1, 2, 6-, 1, 3, 7-, and 2, 3, 6-naphthalenetricarboxylic acids. Preferably, these trifunctional moieties are present in the repulped NDA in an amount of from 50 to about 10000ppm by weight, preferably from about 200 to 9000ppm by weight, most preferably from about 150 to 8500ppm by weight. While other aromatic monomers such as PTA are the subject of the present invention, trifunctional acids such as 1, 2, 3-, 1, 2, 4-, and 1, 3, 5-trimellitic acid and mixtures thereof are the more likely trifunctional moieties and may be present in the range of naphthalene trifunctional moieties described above. Of course, mixtures of any and all of the above trifunctional impurities may be present in accordance with the invention, and impurities having a functionality greater than 3 may also be advantageously employed in accordance with the invention. The term "trifunctional material" as used herein refers to any process-related material having three functional groups reactive with a diol under polymerization conditions. The term "multifunctional material" refers to any such material having three or more functional groups.

Polyester color is a very important performance requirement in some applications, while color is not important in other applications. Sometimes certain packaging products require a color such as brown. Brown is typically obtained by the addition of dyes, which are generally high molecular weight organic compounds. Dyes are undesirable because they can detract from the properties of the polyester, particularly the barrier to permeation of gases such as oxygen and carbon dioxide. In addition, the dyes are expensive and are not ideal from the aspects of environmental protection and recycling. Thus, colored species present in aromatic acid monomers can be used to introduce a color, such as brown, into a subsequently formed polymer. Useful colored materials according to the present invention include benzocoumarin (benzcoumarins), pentaalkanones, pentacenes, and fluorenone structures containing carboxylic acid functionality. Typically, these colored materials should be present in an amount of about 50 to 500ppm by weight, more preferably about 50 to 250ppm by weight, and most preferably at a level of about 150 ppm.

The slurried NDA according to the present invention may also contain monofunctional impurities including, but not limited to, aromatic acid impurities such as benzoic acid and benzoic acid bearing substituents such as methyl, bromine, and formyl, and 1-and 2-naphthoic acid bearing substituents such as methyl, bromine, and formyl, and mixtures thereof. The concentration of monocarboxylic acid in the repulped NDA is typically about 50 to 5000ppm by weight, preferably 100 to 4000ppm by weight, and most preferably about 150 to 3500ppm by weight. The term "monofunctional material" as used herein refers to any process-related material having a functional group that can react with a diol under typical polymerization conditions.

If the desired advantages resulting from these materials are not required in the desired monomer application, each of the above materials need not be present in the amounts described above.

As an example, crude NDA may be repulped to yield NDA monomers having similar specifications as listed in table 2 below.

TABLE 2

Substance(s) Content level

Trifunctional material 5500+/-1500ppm

Monofunctional materials 2000+/-1000ppm

Metals (Co + Mn) 1000+/-500ppm

Coloured substances 150+/-120ppm

Examples 1 and 2 below illustrate the effect of cobalt and manganese metals on the rate of polymerization of aromatic polymers. The effect of the catalyst metal in the NDA monomer in the Pure Terephthalic Acid (PTA)/Naphthalene Dicarboxylic Acid (NDA) polymer was demonstrated by comparing the polymerization of a 92 mole% PTA/8 mole% NDA mixture catalyzed by antimony with ethylene glycol polymerization (the polymer will be hereinafter referred to as "PETN-8") with a similar mixture of 90ppm by weight cobalt (as cobalt acetate) and 30ppm by weight manganese (as manganese acetate) with "no recycle". The polymerization times of the pressure esterification, the atmospheric esterification and the polycondensation of these two mixtures were measured.

Example 1

This example illustrates the melt polymerization of PETN-8 without cobalt and manganese in the concentration ranges of the present invention. The following materials were charged to a 56 liter helical stirred reactor: 12.86 kg of ethylene glycol, 27.53 kg of terephthalic acid, 3.12 kg of 2, 6-naphthalenedicarboxylic acid, 1.34 g of tetramethylammonium hydroxide, 8.46 g of antimony trioxide, and 3.00 g of cobalt acetate (20 ppm based on the polymer yield). The reactor temperature was initially 107 ℃ and the reactor was pressurized with 40psig of nitrogen. The melting temperature was increased to 223-246 ℃ while the pressure was maintained at 40psig and water was removed. When the evaporation of water is stopped, the pressure is reduced to normal pressure, and the pressurized esterification is completed. The pressure esterification time was 218 minutes.

The melt temperature was then raised to 263 ℃ and normal pressure esterification was continued for 60 minutes. An additional 100 grams of ethylene glycol and 3.83 grams of phosphoric acid were added. The reactor pressure was reduced from atmospheric to 3 mmhg over a period of 65 minutes while the melting temperature was increased to 285 ℃. The melt polycondensation was continued for an additional 108 minutes for a total polycondensation time of 173 minutes to achieve a stirrer torque value of 1800 lb-in. The product is kneaded, quenched and granulated. The inherent viscosity of the product, measured in 60/40 phenol/tetrachloroethane at 30 ℃ and at a concentration of 0.4g/dL, was 0.58 dL/g.

Example 2

The following examples illustrate the melt polymerization of PETN-8 containing cobalt and manganese in the concentration ranges of the present invention. Example 1 was repeated with the same starting materials and weights except that 4.42 grams (28 ppm based on the weight of the polymer) of manganese acetate was added and the amount of cobalt acetate added was 13.59 grams (91 ppm based on the weight of the polymer). Exactly the same temperature and pressure were used and the pressure esterification time was 220 minutes. The esterification time was 60 minutes at atmospheric pressure and the polycondensation time required to obtain a torque value of 1800 lb-in at a melt temperature of 285 c was 117 minutes. The inherent viscosity of the product was 0.59 dL/g.

As can be seen by comparing examples 1 and 2, the pressure and atmospheric esterification reactions were completed in about 220 and 60 minutes for the "spiked" samples of examples 1 and 2 and the comparative sample, respectively. It is beneficial, however, that the polycondensation reaction for the "spiky" sample was completed in about 117 minutes, while the comparative sample was about 173 minutes. The significant reduction in reaction time is believed to also provide significant economic benefits in use.

Example 3 below illustrates that the presence of mono-and tricarboxylic acid impurities does not adversely affect the melt polymerization of PETN-8.

Example 3

Example 1 was repeated for comparison with the same starting materials and weights, except that 12.57 g of trimellitic acid, 3.8 g of 2-formyl-6-naphthoic acid, 2.22 g of 2-naphthoic acid and 0.19 g of 2-methyl-6-naphthoic acid were added. High purity NDA obtained from hydrolyzed NDC was used for comparison, while repulped crude NDA obtained directly from DMN oxidation was used for the inventive samples. The compositions and properties of the comparative samples and samples with mono-and tri-functionality are listed below. Colored material was present in the crude sample and was not quantified.

Impurity (ppm) comparative sample the inventive sample

Tricarboxylic acid anhydride 4029

Monocarboxylic acid 1091993

Amount of catalyst (ppm)

Cobalt 2090

Manganese is 30 or less

Antimony 200200

Processing time (minutes)

Pressurized esterification 218215

Esterification reaction 6060 under normal pressure

Polycondensation reaction 173118

Properties of polyester

Inherent viscosity, dL/g 0.580.56

The color of the color(s) is (are),^*b value-0.38 +14.62

The reduction of the polycondensation reaction time from 173 minutes to 118 minutes according to the invention is of economic importance.

Regarding color, it should be noted that the above-mentioned b color values of the markers are tristimulus color values on the blue/yellow scale. On the scale, negative values show blue and positive values yellow, but on the scale^*At b values above +10, the color seen is brown. Thus, the polyesters prepared according to the invention are particularly suitable for use in beer bottles and other brown container applications without the need for the addition of costly and environmentally conscious organic dyes or pigments. Such inventive colored material-containing polyesters are also useful as relatively low cost polyesters for applications that do not require a white color, such as industrial fibers and insulation films.

Example 4 below illustrates the improved solid state polymerization capability of the polymer of the present invention.

Example 4

3.0 grams of polymer pellets produced from the materials of examples 1 and 2 were crystallized in an oven at 150 ℃ for 2.0 hours. The particles were placed in a test tube and vacuum was applied, and the test tube was placed in an oil bath at room temperature. The oil was heated to 410 ° F over 200 minutes, which 410 ° F was considered the starting point for the solid state polymerization. Samples were periodically removed from the oil bath and the following data were obtained:

inherent viscosity in time (hours) (dL/g)

Comparative sample inventive sample

Start 0.600.58

1.0 0.61 0.62

2.0 0.62 0.64

4.0 0.65 0.68

6.0 0.71 0.73

8.0 0.75 0.77

Rate (dL/g) 0.01880.0238

The above data show an increase in the solid state polymerization rate of the present invention of about 40% compared to the comparative sample.

Examples 5 and 6 below illustrate that films can be formed and stretched from the polymers of the present invention and show that the presence of foreign impurities in the polymer does not have a negative impact on the film product.

Example 5

The solid polymer pellets of the invention of example 4 were dried at 150 ℃ for 16 hours and melt extruded using a Killion model KL-125 single screw extruder with a 1.25 inch screw having an aspect ratio of 24: 1 (L/D24/1). The extruder was equipped with a six inch adjustable lip die and three cold warm rolls for take-off. The temperature profile of the heater used was 515/525/530/530/530/500 ° F (feed throat to die) and the screw speed was 75 rpm. Producing a high quality amorphous sheet with a thickness of about 23 mils.

Example 6

The sheet sample of example 6 was biaxially oriented in a t.m.long stretcher. The sample was heated to 226 ℃ 244 ℃ F. for 2.0 minutes and stretched at a contamination rate of approximately 300%/second to give a 3X 3 biaxially oriented film.

The following film properties were measured:properties of Comparative sample Inventive sampleDegree of crystallinity,% 25.023.7 carbon dioxide Permeability 34.231.2 (cc-mil/100in2-day-atm @35 ℃ C.)

From the above data, it can be seen that the PETN-8 copolyester sample of the present invention containing high concentrations of monocarboxylic and tricarboxylic acids exhibits substantially the same level of crystallinity as the comparative sample and both films have similar carbon dioxide transmission values. However, for packaging applications, the low permeability values of the present invention translate into long shelf life. Both films were strong and showed no signs of shine.

Other preferred polyesters that may use the NDA monomer product of the invention include any PTA/NDA polymer having a molar ratio of PTA to NDA of from 99: 1 to 0: 100. A preferred range of NDA to PTA in an NDA/PTA polyester is from 2 to 15 mole percent NDA to 98 to 85 mole percent PTA, more preferably from 2 to 9 mole percent NDA to 98 to 91 mole percent PTA. The NDA used in the present invention may be any polymerizable isomer such as 2, 6-, 1, 5-, 1, 4-and 2, 7-NDA, and mixtures thereof. The polyester may also include up to about 15 mole% of other carboxylic acids such as isophthalic acid and/or adipic acid. The polyester may also incorporate less than about 10 mole% of a diol such as diethylene glycol, 1, 4-butanediol, polybutylene glycol, or 1, 4-cyclohexyldimethanol, or mixtures thereof. In view of the ranges of process-related materials listed in Table 1 above, it should be noted that high levels of monomer impurities are advantageous when the monomer product is used as the minor component of the copolymer, while low levels of impurities are advantageous when the monomer product is a homopolymer as the major or terminal product of the copolymer.

The inherent viscosity of the product, measured at 30 ℃ and at a concentration of 0.4g/dL in 60/40 phenol/tetrachloroethane solution, is typically from about 0.40 to 1.00dL/g, preferably from about 0.50 to 0.90dL/g, and most preferably from about 0.60 to 0.80 dL/g.

The dicarboxylic acid component of the polyester of the present invention may optionally be modified with 15 mole% or less of one or more other dicarboxylic acids other than terephthalic acid and 2, 6-naphthalenedicarboxylic acid. The other dicarboxylic acids include aromatic dicarboxylic acids preferably having 8 to 14 carbon atoms, aliphatic dicarboxylic acids preferably having 4 to 12 carbon atoms, and alicyclic dicarboxylic acids preferably having 8 to 12 carbon atoms. Examples of dicarboxylic acids that are included are phthalic acid, isophthalic acid, cyclohexanediacetic acid, 4 '-diphenyldicarboxylic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, azelaic acid, sebacic acid, 1, 4-cyclohexanedicarboxylic acid, resorcinol diacetic acid, diglycolic acid, 4-oxybis (benzoic acid), 1, 12-dodecanedioic acid, 4' -sulfonyl dibenzoic acid, 4 '-methylenedibenzoic acid, trans-4, 4' -diphenylethylene dicarboxylic acid, 2, 6-dicarboxy tetrahydronaphthalene, 2, 6-dicarboxy decahydronaphthalene, and the like.

Other additives and stabilizers well known in the art, such as glass fibers, mineral extenders, oxygen scavengers, diethylene glycol inhibitors, visual brighteners and phosphorus containing stabilizers, may be added to the monomer products and polymers made therefrom according to the present invention.

The monomers according to the invention can also be used for the preparation of homopolymers and copolymers from relatively pure acids by means of the stated substances in the amounts stated above.

For example, metal salts particularly suitable for use in preparing the metal-containing monomer include cobalt and manganese alkyls such as acetates, halides, especially bromides, and organic acid salts, especially aromatic salts. When the salt is added to a relatively pure aromatic acid, the concentration of the metal may range from about 20 to 10000ppm by weight, more preferably from about 50 to 2000ppm by weight, and most preferably about 100 to 1000ppm by weight.

If Co and Mn are added to make the monomers according to the invention, the molar ratio of Co to Mn is in the range of 5: 1 to 0.2: 1, preferably 4: 1 to 0.25: 1, most preferably 3: 1 to 0.5: 1.

The polymers according to the invention can be prepared in the same way as polymers from the same pure acid monomers. Such polymerization reactions are well known in the art. See, for example,transforming Encyclopedia of academic and industrial technologyVol.18, pp.531-594, John Wiley and sons (1982), the disclosure of which is incorporated herein by reference.

The copolyester and homopolyesters prepared according to the present invention may be used to make sheets, biaxially oriented films, fibers, stretch blow molded containers, and any other article typically using such polyesters. See, for example,plastic engineering handbookFourth edition, Van nonstand Reinhold company (1976), the disclosure of which is incorporated herein by reference.

The presence of metals, colored species and other impurities in the acid monomers of the present invention makes the presence of the color of these monomers desirable or non-objectionable and particularly useful in NDA copolymer applications where enhanced high temperature performance is desired. Typical articles particularly suitable for use with the copolymers of the present invention are containers for food or beverages which require heating or pasteurization and must exhibit two-dimensional stability during and after the heating or pasteurization process. This is particularly true when the material being packaged contains carbon dioxide or other gases which, when heated, create significant internal packaging pressure. Specific examples of such articles are pasteurisable bottles for beer and bottles for fruit juices, such as prune juice, where the heating properties and colour of the package are desirable packaging characteristics. The utility of the NDA/PTA copolymer is demonstrated by example 7 below.

Example 7

Half liter capacity, pasteurizable, long neck amber beer bottles with champagne colored bases were produced from test copolymers containing repulped acid monomers having the compositions set forth in table 2 above.

In example 7A, the PETN-3 copolymer used contained 3 mole% repulped NDA and 97 mole% pure terephthalic acid. In this example, a 35.0 gram injection molded preform was prepared. The preform contained approximately 15 grams of copolymer in its shoulder region, approximately 10 grams of copolymer in its sidewall region, and approximately 10 grams of material in its bottom region.

In example 7B, PETN-5 copolymer was used containing 5 mole percent repulped NDA and 95 mole percent of the same pure terephthalic acid. In this example, a 34.1 gram injection molded preform was prepared. The preform contained approximately 14.7 grams of copolymer in its shoulder region, approximately 10 grams of copolymer in its sidewall region, and approximately 9.4 grams of material in its base region.

The preforms of examples 7A and 7B were blown into 0.5 liter bottles using a Sidel SBL2/3 stretch blow molding machine. Carbonated water containing approximately 2.9-3.1 volumes of carbon dioxide was added to each bottle to a predetermined fill line and the cap was closed.

The capped bottle was placed in a pasteurization chamber and sprayed with water at 71 c until the interior of the bottle approached a temperature of about 63 c. The temperature of the spray water was then reduced to 64 ℃ to maintain the interior of the bottle at 63 ℃ for an additional 15 minutes. The temperature of the sprayed water was then lowered until the interior of the bottle was close to 40 ℃, after which the bottle was chilled to room temperature in a cold water bath.

Several physical parameters of the pasteurized bottle were measured to determine the effect of the pasteurization process on the bottle. The results of the measurement are shown in Table 3 below.

TABLE 3

Bottle material PETN-3 PETN-5

Resin IV 0.800.80

Two dimensional change (% increase)

Height 0.430.26

Diameter of

Upper bumper 1.942.15

Intermediate side wall 1.740.48

Bottom bumper 1.031.04

Neck 1.271.36

Fill line drop in 0.600.69

Perpendicularity (inches from center line) 0.1190.152

Pressure (volume) 2.712.68

In the case of examples 7A and 7B, the two-dimensional variation of both bottles was judged to be acceptable in terms of pressure retention (at least 75% of the pasteurisation pressure was retained when starting to fill about 3 volumes of pressure) and verticality (the vertical deviation of the vertical radial symmetry axis of the bottle, measured from the top, is less than 0.25 inch when the pasteurised bottle was placed at the bottom). A filling line drop of less than 3% is also preferred.

Injection blow molded bottle preforms containing about 40-60 wt.% material in the shoulder region, 26-32 wt.% material in the sidewall region, and 25-31 wt.% material in the bottom region were also found to be the most successful in the pasteurization test. These approximate preform weight distributions and geometries are believed to be useful for half-liter bottles made with other polymers and scalable for making pasteurized bottles of other volumes.

While the above examples describe the invention in certain aspects of the naphthoic acid monomer product, one of ordinary skill in the art will recognize that the invention is equally applicable when correcting for differences in molecular weight between naphthalene and other aromatic monomers in connection with monomers having process-related species present in approximately the same ranges, such as terephthalic acid, isophthalic acid, and the like. In addition, when the monomers of the invention are used to make polymers, the process-related substances present according to the invention may, for example, be present in any one monomer or in more than one monomer. For these reasons, the present invention is to be limited only by the scope of the following claims.

Claims (5)

1. A process for preparing a naphthalenedicarboxylic acid monomer product useful in the manufacture of polyesters, said process comprising the steps of:

oxidizing a naphthalene raw material to generate crude naphthalenedicarboxylic acid;

processing said crude naphthalenedicarboxylic acid to produce a naphthalenedicarboxylic acid monomer product containing at least 90 mole% of said acid monomer and one or more process-related substances selected from the group consisting of 50-5000ppm monofunctional substances, 50-10000ppm trifunctional substances, 50-500ppm colored substances and 50-10000ppm metals;

wherein the processing step comprises slurrying the crude naphthalenedicarboxylic acid in a solvent selected from the group consisting of water, aliphatic organic acids having 2-4 carbon atoms, and mixtures thereof;

and the slurrying step is conducted at a temperature of about 75-110 deg.C, a pressure of about 1-2 atmospheres, and a weight ratio of solvent to crude naphthalenedicarboxylic acid of about 1: 1 to 10: 1, wherein the solvent contains at least 50 mole% acetic acid.

2. The method of claim 1 wherein the process-related material is selected from the group consisting of 150-.

3. The method of claim 1 wherein the process-related material comprises 500-2000ppm of a metal selected from the group consisting of cobalt, manganese, and mixtures thereof.

4. A process for preparing a naphthalenedicarboxylic acid monomer product, said process comprising the steps of:

oxidizing a naphthalene raw material to generate a crude naphthalenedicarboxylic acid containing a naphthalenedicarboxylic acid used as a monomer in polymerization and process-related substances formed during the production of the crude naphthalenedicarboxylic acid;

slurrying the crude naphthalenedicarboxylic acid in a solvent to remove a portion of the process-related materials from the crude naphthalenedicarboxylic acid;

recovering solid monomer from the slurry to obtain a naphthalenedicarboxylic acid monomer product containing at least 93 mole% of said acid monomer and one or more process-related substances selected from the group consisting of 50-5000ppm monofunctional substances, 50-10000ppm trifunctional substances, 50-500ppm colored substances and 50-10000ppm metals;

wherein the processing step comprises slurrying the crude naphthalenedicarboxylic acid in a solvent selected from the group consisting of water, aliphatic organic acids having 2-4 carbon atoms, and mixtures thereof;

and the slurrying step is conducted at a temperature of about 75-110 deg.C, a pressure of about 1-2 atmospheres, and a weight ratio of solvent to crude naphthalenedicarboxylic acid of about 1: 1 to 10: 1, wherein the solvent contains at least 50 mole% acetic acid.

5. The process of claim 4, wherein no recrystallization step is performed between the oxidation step and the recovery step.