MXPA98002538A - Thermoplastic copolytheres with improved barrier properties to ga - Google Patents

Abstract

Thermoplastic copolyesters having improved gas barrier properties and which can be produced with little or no acetaldehyde are disclosed. These copolyesters are particularly useful in the manufacture of products for packaging, trays for food, film and bottles for beverages that require good properties of oxygen and carbon dioxide barrier. The copolyesters comprise repeating units of from 10 to 100 mol percent of repeated units of naphthalene dicarboxylic acid, 90 to 0 mol percent of repeating units of terephthalic acid and repeating units of essentially 100 mol percent of 1,4-cyclohexanedimethanol, wherein said 1.4- cyclohexanedimethanol has a cis isomer content of at least 50% said copolyester having an IV of 0.4

Description

THERMOPLASTIC COPOLYESTERS WITH IMPROVED PROPERTIES OF BARRIER TO GASES Technical Field This invention relates to thermoplastic copolyesters having improved gas barrier properties and which can be produced essentially without containing acetaldehyde. These copolyesters are especially useful in the manufacture of food packaging products, food trays, film and bottles. for drinks that require good oxygen and carbon dioxide barrier properties BACKGROUND OF THE INVENTION The present invention provides high molecular weight copolyesters and have improved oxygen and carbon dioxide barrier properties and in which very little or no acetaldehyde is produced in the manufacturing or processing process. The invention provides copolyesters having better Oxygen and carbon dioxide barrier properties than poly (ethylene terephthalate) which is used universally for food packaging, bottles for carbonated soft drinks and packaging applications that require good oxygen barrier properties and carbon dioxide Poly (ethylene terephthalate) can undergo degradation during its preparation and conversion to film, bottles and other packaging materials with the evolution of acetaldehyde. Finally, acetaldehyde is entrained within the polyester. Products made from it can be adversely affected by the taste of the food This is because it diffuses from the material to the food. The polyesters described here do not generate acetaldehyde and have barrier properties equal to or greater than those of poly (ethylene terephthalate). These polymers have better oxygen barrier properties and carbon dioxide meets the needs that require better barrier properties than those that can be provided with the poly (ethylene terephthalate) In US Pat. No. 2,901, 466 to Kibler, Bell and Smith, a polyester copolyester (1, 4-c? clohex? lenod? methylene) terephthalate with cis and trans isomers of 1,4-c? clohexanod? methanol There are numerous patents where pol? (2,6-naphthale Ethylene carboxylate is considered to have excellent oxygen and carbon dioxide barrier properties. I am not aware of any description of a copolyester having good oxygen and carbon dioxide barrier properties. n where the copolyester is made from repeated units of naphthalene dicarboxylic acid, terephthalic acid, and 1,4-c? clohexanod? methanol with high cis isomer content DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION We have unexpectedly discovered an ester flake system with oxygen and carbon dioxide barrier properties superior to those of poly (ethylene teraphthalate), a polyester which is used extensively in bottles for soft drinks These thermoplastics are useful as film, fiber bottles and food packaging devices such as food trays and lid materials. These polyesters have excellent physical properties as well as oxygen barrier and carbon dioxide properties equal to or considerably better than those of poly (ethylene terephthalate) which makes them extremely useful as barrier materials Therefore, in accordance with this invention, flake esters which have improved barrier properties with respect to oxygen and carbon dioxide and which comprise repeating units of from 10 to 100 mole percent of naphthalene dicarboxylic acid, are provided. 90 to 0 mol percent of terephthalic acid and essentially 100 mol percent of 1,4-c-chlorhexanod? Methanol, wherein 1,4-c? Clohexanod? Methanol has a cis isomer content of at least 50%, the copolyester having an inherent viscosity value of 0-4-1 (IV) Conventional processes that are well known in the art can be used to produce the copolyesters from terephthalic acid or lower dialkyl esters thereof, dicarboxylic acid from 2,6-naphthalene or lower dialkyl esters thereof, and 1,4-c-chlorhexanodomethanol containing an isomer content - > cis of at least 50% The terephthalic acid and the 2,6-naphthalene dicarboxylic acid and its lower dialkyl esters (especially dimethyl esters) are well-known monomers and are commercially available 1,4-c-Clohexanod? Methanol with high or isomer content cis (at least 50% cis isomer) can be prepared by those skilled in the art A method for isolating CHDM with a cis content of 50-100% will now be described. An equilibrium mixture containing 32% cis isomer is dissolved in hot ethyl acetate at a temperature of 70 ° C. The mixture is cooled to 23 ° C. whereby an essentially pure trans-CHDM is crystallized and separated in a centrifuge. The cis-rich filtrate is subjected to a vacuum, whereby the ethyl acetate solvent is removed by vacuum distillation to leave a CHDM residue having a content of cis isomer 50% (by weight) or more Other methods of or separation are well known in the art Minor amounts of modifying dicarboxylic acids and glycols can be used in the preparation of the copolyesters. If used (preferably of the order of less than 20%) the acids and glycols can be selected from ethylene glycol, diethylene glycol, propane-1,3-d. ? ol, butane-1, 4-d? ol, polytetramethylene, polyethylene glycol, polypropylene, neopentyl glycol and the like, isoptalic dibenzoic acid adipic sebacic, decane-1, 10-d? carboxyl? -glycolic acid and the like In general, copolyesters they would be prepared using a combination of a first phase of molten stenfication and subsequently a solid stenfication phase and a polycondensation phase, both processes being well known in the art. The process is continued until the desired IV is reached (inherent viscosity) In addition, the polymer blend can include additive slots that do not adversely affect the polymer in use, such as stabilizers, for example antioxidants or ultraviolet light protection agents, extrusion aids, additives designed to render the polymer more degradable or fuel such as oxidation catalysts, as well as dyes and pigments Following the preparation, the copolyesters are usually pelletized by well-known means and subsequently are formed into useful articles such as by extrusion molding, injection, model combinations by extrusion or injection with blow molding, etc.

EXAMPLES The following examples are presented for a better understanding of the invention Typical Copolyester Preparation In a 500 mL round bottom flask, equipped with a round glass head, a stirring arrow, nitrogen inlet and side arm, 48 5 grams (0 25 moles) of dimethyl terephthalate are charged, grams (0-25 moles) of dimethyl 2,6-naphthalene carboxylate, 79 2 grams (0 55 moles) of 1,4-cyclohexanedimethanol mixture (95 5/4 5) (cis / trans) and 1 42 mL of butanol solution of titanium tetraisopropoxide containing 0 0102 grams of titanium per milliliter The bottle was immersed in a Belmont metal bath pre-heated to 200 ° C and as soon as the bottle was submerged the temperature of the bath was reset to 290 ° C The reaction mixture was stirred for about 45 minutes until the bath temperature reached 290 ° C. After this time the theoretical amount of methanol had been collected and the pressure in the flask was reduced to 0 1 to 0 5 mm of mercury This temperature and pressure were maintained uring 1 hour The metal bath is removed from the bottle, the vacuum outlet is covered, the nitrogen inlet is opened, the bottle is allowed to reach atmospheric pressure under a nitrogen blanket. The copolymer is allowed to cool to room temperature This copolyester prepared in the molten phase has an inherent viscosity of 0 72. This is a typical laboratory preparation of copolyesters which are described in this invention.

All copolyesters were film extruded and the film was stretched and oriented in 3 x 3 array using a T.M Long stretch apparatus. The oxygen and carbon dioxide transmission rates were determined on the film l i using ASTM standards D3985 and D1434, respectively.

Table 1 consists of nine film examples showing the apparent viscosity, glass transition temperature and oxygen permeability of the ester composition so that it can be used in the molding of bottles for or refreshments, the oxygen barrier is l / 100 in2 for 24 hours is 6 61 This is a typical value for any poly (ethylene terephthalate) bottle for soft drinks Examples 1, 2 and 5 in Table 1 show three copolyesters containing more than 90% 1, 4-c? Clohexanod? Methanol cis (CHDM) copolimenzado, with 10, 30 and 50 mol percent of 2,6-naphthalene-d? Carbox? Lato These show an oxygen barrier of 1 to 2 4 times better than that of the poly (ethylene terephthalate) shown in Example 9, Table 1 Example 6, which contains a 50/50 mixture of cis / trans isomers of 1,4-c-chlorhexanod-methanol and does not contain , 6- naphthalenedicarbixilate has much worse oxygen barrier properties than the? Ol? (Ethylene terephthalate) mo In Example 9, Example 7, Table 1, does not contain 2,6-naphthalend? carboxylate and high (90% cis CHDM) and is approximately equivalent in oxygen permeability to Example 9 (polyethylene terephthalate) Permeabilities to oxygen are 6 31 and 661 ce m? l / 100 in2 for 24 hours, respectively, whose difference is probably within the margin of experimental error and which is considered not to represent an important difference Example 8 is a copolyester containing 100 percent mole of 2,6-naphthalene dicarboxylic acid, CHDM isomer with high cis content (85%) and has oxygen barrier properties of more than 4 times better than the poly (ethylene terephthalate) shown in or Example 9 Example 3 is composed of 50/50 mole percent of dimethylterephthalate and 2,6-d? Methanophthalate and 50/50 cis / trans isomer of 1,4-c? Clohexanod? Methanol The oxygen permeability of this polymer is 6 51 cem? l / 100 in2 for 24 5 hours compared to 6 61 for the pol? (ethylene terephthalate) shown in Example 9 These values are not considered to be significantly different This example shows that still a low cis CHDM concentration (50%) is useful Example 4 can be compared to Example 1 Example 4 contains either 75 mole percent cis isomer rather than 95 mole percent as in Example 1 The oxygen barrier is still about 1 3 times better than those of pol (ethylene terephthalate) shown in Example 9 It is intended that these examples show that a family of co-esters 5 with excellent oxygen barrier properties has been discovered and that the combination of 1,4-c-clohexanod? Methanol of high cis content is necessary to reach the improved barrier and that the discovered isomorphism of 2,6- for naphthalenedicarboxylate and terephthalate with 1,4-c-clohexanod? methanol provides the ability to make these copolyesters polymers with excellent oxygen barrier. u c? 00 * _o c _? _ 00 0) si- The I V is measured in a solution of 60/40 parts by weight of phenol / tetrachloroethane at 25 ° C and at a concentration of 0.5 grams of polymer in 100 mL of solvent Oxygen permeability is measured by ASTM D 3985, in cubic centimeters, permeating a sample of 1 millimeter thick, 100 square inches, for a period of 24 hours under a partial pressure difference of oxygen of one atmosphere at 30 ° C and 68% relative humidity using a MOCON Oxtran 10-50 instrument Unless otherwise specified, all parts, proportions, percentages, etc. They are by weight The invention has been described in detail and with particular reference to the preferred embodiments thereof, but it will be understood that variations and modifications may be made within the spirit and scope of the invention.

Claims (3)

1. Novelty of the Invention 1 Copolyesters with improved barrier properties with respect to oxygen and carbon dioxide, which comprise repeating units of 10 to 100 mol percent of repeated units of naphthalene dicarboxylic acid, 90 to 0 mol percent of repeating units of terephthalic acid and repeating units of essentially 100 percent mol of 1,4-c-chlorhexanod? methanol, wherein said 1,4-cyclohexanedimethanol has a cis isomer content of at least 50% said copolyester having an IV of 0-4. -1 2
2. 2 Copolyesters according to claim 1, wherein the I V is 0 7-0 8

   An article of manufacture comprising the copolyester of claim 1

   A container comprising the copolyester of claim 1

   Extract of the Description Thermoplastic copolyesters having improved gas barrier properties and which can be produced with very little or no acetaldehyde are described. These copolyesters are especially useful in the manufacture of products for food packaging, food trays, film and bottles for beverages that require good oxygen and carbon dioxide barrier properties The copolyesters comprise repeating units of 10 to 100 mole percent of repeated units of naphthalene dicarboxylic acid, 90 to 0 mole percent of repeat units of terephthalic acid and repeating units of essentially 100 percent mol of 1,4-c-chlorhexanodomethane, wherein said 1,4-cyclohexanedimethanol has a cis isomer content of at least 50%, said copolyester having an IV of 0 4-1 2