CS244359B1 - Method of modified polyesters preparation - Google Patents

Abstract

A method for preparing modified polyesters based on terephthalic acid and ethylene glycol, where the modifying component is polyfunctional alcohols that cause branching of macromolecules, in which during the preparation of polyesters, two to six polyfunctional alcohols are added to the reactants. Polyfunctional alcohols of the general formula H-(OH)n, where n is in the range of 3 to 10 and R is an organic radical, are added in a total concentration of 0.01 to 3.0 mol. % relative to the acid component of the polyesters. The process according to the invention makes it possible to independently control several properties of modified polyester fibers in the desired manner, such as wettability, strength, pilling and dyeability.

Description

(54)

Method of preparing modified polyesters

A method for preparing modified polyesters based on terephthalic acid and ethylene glycol, where the modifying component is polyfunctional alcohols that cause branching of macromolecules, in which during the preparation of polyesters, two to six polyfunctional alcohols are added to the reactants. Polyfunctional alcohols of the general formula H-(OH) _n , where n is in the range of 3 to 10 and R is an organic radical, are added in a total concentration of 0.01 to 3.0 mol. % relative to the acid component of the polyesters. The process according to the invention makes it possible to independently control several properties of modified polyester fibers in the desired manner, such as wettability, strength, pilling and dyeability.

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The invention relates to an improvement of the method for preparing modified polyesters based on terephthalic acid and ethylene glycol, where the modifying component is polyfunctional alcohols that cause branching of macromolecules.

The preparation of polyesters by the reaction of dibasic acids or their lower aliphatic esters with difunctional alcohols is well known from the technical literature. The reaction mixture is heated gradually to a temperature of 260 to 290°C under appropriate pressure and in the presence of catalysts, stabilizers, matting agents or other additives to form higher molecular weight polyesters. In particular, those polyesters which are obtained by the reaction of terephthalic acid or its methyl ester or a mixture of some of these substances and other dibasic acids or their esters, in which terephthalic acid or its methyl ester predominate, with ethylene glycol or with mixtures of ethylene glycol with other difunctional alcohols in which ethylene glycol predominates, are suitable for the preparation of fibres. However, fibers prepared from these polyesters generally pill easily in fabrics, which significantly reduces the utility properties of fabrics made from these fibers alone or from mixtures of these fibers with other fibers, such as wool, cotton, viscose, and the like. Pilling of polyester fibers is usually reduced by chemical modification of the polymer, which allows increasing the dynamic viscosity of the melt and thus spinning polymers with reduced molecular weight and therefore with reduced specific viscosity of the polymer. It has been found that pilling of fibers in fabrics correlates with the resistance of fibers to bending, which increases with molecular weight. Increasing the dynamic viscosity of the polymer melt

- 2,244,359 is achieved, for example, according to US 3,033,824 and US 3,576,773 by the addition of a modifying component which contains short polar and bulky side substituents, such as -SO^M groups, where M is Na or K, or by the addition of a modifying component which causes branching of the basic polymer. As agents causing branching of polyesters, polyfunctional alcohols are most often used, less often phenols, organic hydroxy acids and organic acids or lower aliphatic esters of these acids or their anhydrides. These polyfunctional compounds are used in a pure state. Only small amounts of impurities arising during the preparation of polyfunctional compounds do not, according to the processes described so far, such as in US 2,895,946 and in US 3,033,824, impair the use of polyfunctional compounds as branching agents. The processes used so far for the preparation of branched polyesters using the addition of polyfunctional alcohols are applied, in addition to the anti-pilling treatment of polyester fibers, also in the preparation of fibers with a non-staining treatment, fibers having improved heat and light resistance and fibers with improved dyeability, as described, for example, in US 3,461,468, US 3,668,188, US 3,669,935, US 3,671,495 and US 3,684,768. However, these processes do not utilize the possibilities for influencing the properties of branched polyesters, which result from the existence of different types of branching of macromolecules. For example, the properties of polymer fibers, such as crystallinity, dyeability, wettability and density, are influenced primarily by the presence of a larger number of shorter side chains of the comb-type. Longer side chains of the star-shaped and comb-type will mainly affect the strength of the fibers. The dynamic viscosity of the polymer melt is mainly influenced by the tree-like type of branching or the star-like type with very long branches. Existing preparation methods allow the preparation of branched macromolecules with only one type of branching, which then affects only one of the above-mentioned properties of the resulting polymer. Another disadvantage of the previously used and described methods of preparing polyesters with the addition of a polyfunctional compound is the required purity of these modification components.

The above-mentioned shortcomings of the used methods for preparing polyesters based on terephthalic acid and ethylene glycol, modified with polyfunctional alcohols, are eliminated by the solution according to the invention,

244,359

- ₃ _ the essence of which is that polyfunctional alcohols are added to the reactants in the amount of two to six, preferably in a mixture formed during their industrial production. The addition of polyfunctional alcohols can be carried out, for example, at the beginning of the esterification of terephthalic acid or the reesterification of dimethyl terephthalate with ethylene glycol, during this esterification or reesterification or after its completion, at the beginning of the polycondensation reaction or during its course, but at the latest before the completion of the polycondensation so that the reaction of polyfunctional alcohols with polymer chains occurs to form branched macromolecules. Polyfunctional alcohols are added according to the invention in a total concentration of 0.01 to 3.0 mol.%, preferably 0.04 to 0.8 mol.%. At a concentration lower than 0.01 mol.%, their effect on the properties of polyester fibers is no longer noticeable, and at a concentration higher than 3.0 mol.%, problems arise due to the excessively high dynamic viscosity of the polymer melt. In the production of modified polyesters according to the invention, polyfunctional alcohols of the general formula R-(OH) _n are added to the reaction, where n is equal to 3 to 10 and R is a polyvalent hydrocarbon or ether radical. Examples of these alcohols may be glycerol, sorbitol,

1,2,6-hexanetriol, 1,1,i-trimethylolethane, 1,1,1-trimethylolpropane, pentaerythritol, cyclohexanehexaol, dipentaerythritol, tripentaerythritol, diglycerol, triglycerol and the like. The reactivity of functional groups in esterification reactions varies and is higher for primary alcohols than for secondary alcohols. If polyfunctional alcohols are added to the reaction in the preparation of modified polyesters in a mixture, then the amount of alcohols of the type R-(OH)^ and R-(OH)^ is 15 to 98 wt.% and the amount of alcohols with n equal to 5 to 10 is 2 to 85 wt.%. The stated concentration range allows the use of different properties of various polyfunctional alcohols to influence the properties of polyesters.

The advantage of the process according to the invention is the possibility of maintaining sufficient dynamic viscosity of the polymer melt in the production of polyesters based on terephthalic acid and ethylene glycol, while maintaining good spinnability and at the same time influencing other properties of polymer fibers such as strength, bending and abrasion resistance, density, dyeability and wettability. The addition of a larger number of polyfunctional alcohols of different concentrations and different reactivity of functional groups,

- 4 244 399, possibly with different residence times in the reaction, will allow influencing the structure by creating the required amount of side chains of both comb-like, star-like and tree-like branching with different length side chains, which will then influence the required properties of polyester fibers, such as strength, density, wettability and dyeability of the fibers while maintaining their sufficiently high strength and sufficiently low bending resistance. The addition of two or more polyfunctional alcohols in the mixture can also be advantageously used in the production of modified polyesters in the case that the mixture is a technical production product, which is often more accessible and more affordable. This procedure is therefore advantageous in the case of mixtures such as glycerol with polyglycerols and pentaerythritol with dipentaerythritol or even with tri pentaerythritol. The addition of mixtures with glycerol or pentaerythritol compared to the addition of pure glycerol or pentaerythritol is also advantageous because these mixtures contain, in addition to a trifunctional or tetrafunctional alcohol, which mainly causes comb-like branching, also polyfunctional alcohols with a larger number of functional groups in the molecule, which cause tree-like and star-like branching. In contrast to the usual practice, when impurities in the technical product used have an adverse effect on the course of the reaction, in this case they have a positive effect. The combination of a mixture of polyfunctional alcohols and a comonomer containing a polar bulky group -OSO^M, where M is Na or K, also appears to be advantageous, when the reduction of the molecular weight by the action of a relatively expensive and production-intensive comonomer can be partially replaced by the action of a mixture of polyfunctional alcohols. In this case, while maintaining a higher affinity for basic and disperse dyes and low pilling, modified polyesters can be produced more cheaply. The method of implementation is clear from the following examples.

Example 1

1500 g of dimethyl terephthalate, 942 ml of ethylene glycol, 0.77 g of manganese acetate tetrahydrate and 1.0 g of anhydrous antimony acetate were placed in a stainless steel reactor. The re-esterification was carried out with constant stirring for 210 minutes at a gradually increasing temperature from 160°C to 230°C. After the re-esterification was completed, 1.7 ml of trisnonylphenyl phosphite and 30 ml of a 20 wt.% suspension of TiO ₂ in ethylene glycol were added to the reaction mixture. The pressure in the reactor was reduced to the desired value with constant stirring and the temperature was increased to a value in the range of 265 to 280°C. After reaching the values of the stirrer speed corresponding to the desired and in all cases approximately the same molecular weight of the polymer, the melt was extruded from the reactor with nitrogen and granulated. The polymer core was spun after drying and the unstretched fibers were stretched to the total stretch ratio according to the natural stretch ratio and then dried and fixed in a drying oven at a temperature of 125°C for 15 minutes. Modification with polyfunctional alcohols was carried out in the following ways. In the first case, only sorbitol (S) was added to the reaction mixture at the beginning of the reesterification, in the second case only 1,1,1-trimethylolpropane (TMP) was added to the reaction mixture during the polycondensation and in the third case both of these compounds were added to the reaction mixture in the same way. Data on the concentrations of polyfunctional alcohols in relation to the amount of dimethyl terephthalate added, the course of the polycondensation, the viscosity of the polymer measured as a 1% solution at 30°C in the mixed solvent phenol - 1,1,2,2-tetrachloroethane 1 ί 3, and the properties of the fibers are given in the following table No. 1.

Table No. 1

Type of modification Concentration of modification Polycondensation time Specific viscosity of a polymer Strength of the fibers (mol.%) (minutes) (1) (N) With 0.05 70 0.705 0.139 TMP 1.0 60 0.718 0.158 S + TMP 0.05 + 1.0 55 0.700 0.157

Type Ductility Specific Density Moisture Color- modification fibers bending resistance fibers fibers ability at 13O°C (%) (swings/dtex) (g/cm^) (%) (mg/g) With 31 327 1,398 0.43 13.3 TMP 35 341 1,378 0.69 15.7 S + TMP 34 330 1,359 0.92 19.2

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The shortest polycondensation time was achieved with the simultaneous addition of sorbitol and 1»1,1-trimethylolpropane. Fibers modified simultaneously with sorbitol and 1»1,1-trimethylolpropane showed lower density, higher wettability and higher dyeability compared to fibers modified with each component individually. At the same time, sufficiently high strength and low bending resistance were achieved in the fibers. Example 2

Modified polyesters were prepared using the same procedure as in Example 1, with the difference that after the end of the reesterification, monopentaerythritol (MPE) was added to the reaction mixture in the first case, dipentaerythritol (DPE) in the second case, tripentaerythritol (TPE) in the third case, a mixture of monopentaerythritol and dipentaerythritol in the fourth case, and technical pentaerythritol (PERT) with a composition of 83 wt.% monopentaerythritol, 13 wt.% dipentaerythritol and 3 wt.% tripentaerythritol in the fifth case. Data on the concentrations of polyfunctional alcohols with respect to the amount of dimethyl terephthalate added, the course of the polycondensation reaction and the properties of the preparation

The fibers are listed in the following table no. 2. Table No. 2 Type of modification Modification concentration Polycondensation time Specific viscosity of a polymer Strength of the fibers (mol.%) (minutes) (1) (N) MPE 0.08 ' 65 0.692 0.139 DPE 0.04 ⁶⁰ 0.695 0.145 TPE 0.02 55 0.702 0.153 MPE + DPE 0.08 + 0.04 50 0.709 0.149 PERT 0.12 55 0.703 0.156

Type of modification Fiber ductility Specific bending strength Fiber density. Wetness of fibers Colorability at 130°C (*) (swings/dtex) (g/cm3) (%) (mg/g) MPE 30 365 1,382 0.66 15.3 DPE 34 332 1,389 0.56 14.8 TPE 31 324 1,395 0.45 13.9 MPE + DPE 32 351 1,375 0.72 17.9 PERT 34 364 1,369 0.76 18.6

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The shortest polycondensation time was achieved with the simultaneous addition of monopentaerythritol and dipentaerythritol. Fibers modified simultaneously with monopentaerythritol, dipentaerythritol and tripentaerythritol showed the lowest density value and the highest wettability and dyeability values compared to fibers prepared individually from monopentaerythritol, dipentaerythritol and tripentaerythritol.

Example 3

Modified polyesters were prepared by the procedure as in Example 1, with the difference that the polyfunctional alcohols were added to the reaction mixture before the end of the reesterification. Technical pentaerythritol (PERT) was added with the composition as in Example 2 and in concentrations of 0.04; 0.08; 0.12; 0.16 and 0.20 mol.$ relative to the amount of dimethyl terephthalate added. The course of the polycondensation reaction and the properties of the prepared fibers are characterized in the following Table No. 3.

Table No. 3

Concentration The time of the poles- Specific Fortress Ductility Specific PERT condensation viscose fibers fibers resistance polymer in bend· (minor) (minutes) (D (N) (%) (swings/dtex) 0.04 65 0.697 0.148 33 325 0.06 55 0.703 0.156 34 3K 0.12 55 0.710 0.156 34 364 0.16 50 0.728 0.145 33 327 0.20 45 0.730 0.141 29 320 0.20 40 0.695 0.140 31 313 0.20 65 0.882 0.168 39 847 The polycondensation time of the polymer depends on the specific viscosity polymer i on concentration . modifier components, whereas specific

The flexural strength depends primarily on the specific viscosity of the polymer and is independent of the concentration of the modifying component.

Example 4

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A modified polyester was prepared by the same procedure as in Example 1, except that the polyfunctional alcohols were added to the reactants before reesterification. A mixture of glycerol and polyglycerols with a total concentration of 0.5 mol.% and a composition of 15 wt.% glycerol, 34 wt.% diglycerol, 30 wt.% triglycerol, 11 wt.% tetraglycerol, 6 wt.% pentaglycerol and 3 wt.% hexaglycerol was added, based on the amount of dimethyl terephthalate added. The polycondensation was completed after 55 minutes at a specific viscosity of the polymer of 0.746. The drawn and fixed fibers with a fineness of 0.40 tex had the following properties: strength of 0.157 N, elongation of 27%, bending resistance of 1427 swings, relative loop strength of 78%, density of 1.381

O g/cm and humidity 0.55%.

Example 5

75.0 kg of dimethyl terephthalate, 2.04 kg of sodium 3,5-dicarboxybenzenesulfonate dimethyl ester, 0.025 kg of NaCl, were charged into a stainless steel pilot-scale melting and re-esterification reactor.

52.0 kg of ethylene glycol, 0.021 kg of zinc acetate dihydrate and 0.053 kg of technical pentaerythritol, i.e. 0.1 mol.% with respect to the amount of dimethyl terephthalate added, with a composition of 86 wt.% pentaerythritol, 11 wt.% dipentaerythritol and 2 wt.% tripentaerythritol. The re-esterification was carried out with constant stirring at a gradually increasing temperature from 155°C to 220°C. After the re-esterification was completed, 0.042 kg of anhydrous antimony triacetate, 2.9 ml of 85% H^PO^, 2.1 l of a suspension of TiO ₂ in ethylene glycol with a concentration of 13 wt.% were added to the reaction mixture. Then the mixture was transferred to a stainless steel polycondensation reactor, where the pressure was reduced to the desired value while stirring and the temperature was increased to a maximum value of 283°C. After reaching the value of the mixer load corresponding to the desired molecular weight of the polymer, the melt was extruded from the reactor with nitrogen and granulated. The polycondensation was completed at a specific viscosity of the polymer of 0.669, based on the total volume, measured as a 1% solution at 30°C in a mixed solvent of phenol - 1,1,2,2-tetrachloroethane 1:3. After drying, the polymer core was spun and the unstretched fibers were stretched according to the natural stretching ratio and then dried and fixed in a drying oven at

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- 9 at a maximum temperature of 125°C for 18 minutes. The elongated and fixed fibers with a fineness of 0.43 tex were cut into a staple with a staple length of 110 mm, which had the following properties: strength of 0.115 N, elongation of 33%, relative loop strength of 92% and bending resistance of 759 swings. The produced staple was spun in a mixture with wool in a ratio of 45% wool/% PES and knitted fabrics were made from the yarn, which had excellent pilling resistance, better hand and good dyeability with disperse and basic dyes.

Example 6

A modified polyester was prepared by the procedure as in Example 5, except that 75.0 kg of dimethyl terephthalate, 53.1 kg of ethylene glycol and 0.040 kg of manganese acetate tetrahydrate were charged to the melting and re-esterification reactor. Before the re-esterification was completed, 0.048 kg of anhydrous antimony acetate, 80 ml of trisnonylphenyl phosphite, 1.3 l of a suspension of TiO^ in ethylene glycol with a concentration of 20 wt.% and 0.092 kg of technical pentaerythritol, i.e. 0.175 mol.% relative to the charged amount of dimethyl terephthalate, with a composition of 84 wt.% pentaerythritol, 13 wt.% dipentaerythritol and 2 wt.% tripentaerythritol were added to the reaction mixture. The polymer pulp was spun after drying and the unextended fibers were elongated, fixed under tension, fanned, curled, dried and fixed in the free state at a maximum temperature of 130°C for 15 minutes and cut into staple fibers. The properties of the produced staple fibers are given in the following table no. 4.

Table No. 4

Subtlety Step Firmly Ductility Bending resistance tex mm N % swings 0.36 65 0.135 40 1380 0.28 56 0.099 31 963 0.17 38 0.065 26 628

^10,244,359 were spun together with wool or cotton to produce fabrics that had excellent durability, improved hand feel and reduced basis weight.

The staples and yarns produced were anti-pilling^ Example 7 of a melt of modified polyester with a specific viscosity of £ wo _Λ ·_*. » __ · _ _ ___ v _ _z · _ · _ _ m Z, R ·» Z l.

0.678 and the same fiberization fixed in free ίο chemical composition as in example 6 was obtained from unstretched fibers, which were further stretched under tension, avivated, curled, dried and fixed at a maximum temperature of 125°C for 15 minutes. The produced fibers were deposited in the form of tear or cutting cables, table δ. 5· whose properties are given in the following

Table δ. 5

Fineness of fibers tex

Souate fineness ktex

Fiber strength

N

Fiber elongation %

Resistance to bending of the pendulum

Tear cord Cutting cord

0.35

0.36

0.126

0.122

1358

1320

The cables were then spun, processed on tearing or cutting machines together with wool, and the yarns were used to make fabrics that had excellent pilling resistance, improved hand feel, and reduced basis weight.

The process according to the invention could also be used in the production of polyester monofilaments, such as fishing lines, and also for the production of those polyester products which are prepared by pressing, extrusion, injection molding and the like.

Claims (3)

DIS δ E DIS fi T OF THE INVENTION 244 359 A process for preparing modified polyesters by reacting a dibasic acid or a lower aliphatic ester thereof with a divalent alcohol, after which the resulting reaction product is polycondensed to form a polyester, wherein said dibasic acid or ester thereof contains at least 75 mol. % of the terephthalate component and the bifunctional alcohol comprises at least 70 mol. % of ethylene glycol, characterized in that during the preparation, but at the latest before the end of the polycondensation reaction, polyfunctional alcohols of the formula R- (OH) _n in the number of two to six, preferably a mixture formed in the industrial production of polyfunctional alcohols, are added to the reactants. with a total concentration of 0.01 to 3.0 mol. preferably 0.04 to 0.8 mol. % relative to the acid component, wherein n is 3 to 10 and R is a polyvalent hydrocarbon or ether radical and a plurality of R- (OH) and R- (OH) type alcohols. in the mixture j is 4 15 to 98 wt. % and the amount of alcohols with n equal to 5 to 10 in the mixture is 2 to 85 wt. %. 2. A process according to claim 1, wherein the mixture of polyfunctional alcohols of the R- (OH) _{n type} is glycerol, diglycerol, triglycerol, tetraglycerol, pentaglycerol and hexaglycerol. 3. A process for the preparation of modified polyesters according to claim 1, characterized in that the mixture of polyfunctional alcohols of the R- (OH) _n type consists of pentaerythritol, dipentaerythritol and tripentaerythritol.