RU2509785C2 - Method of modifying surface of polyethylene terephthalate granulate - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polymer chemistry and can be used in production of containers, packaging, fibres and tribotechnical articles. The method of modifying the surface of polyethylene terephthalate granulate involves treatment thereof with a modifier while heating, the modifier used being fluorine-containing prepolymers in amount of 2 wt % per 100 wt % polyethylene terephthalate in weight ratio 90(I):3(II):7(III), obtained in advance in form of a product of reacting a hexamethylene diisocyanate trimer containing 21.8-22.1% isocyanate groups with 1,1,7-trihydroperfluoroheptanol-1 in the presence of catalytic amounts of di-n-butyltin dilaurate with molar ratio of reactants of 1:1:0.005, respectively. The reaction is carried out in a medium of nitromethane and n-hexane in volume ratio of 1:6 at 90°C and ultrasound frequency of 40 kHz for 2 hours. Modification is carried out in a medium of chlorobenzene at 150°C for 4 hours in the presence of catalytic amounts of di-n-butyltin dilaurate.

EFFECT: invention increases heat resistance of the polymer.

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Description

The invention relates to the field of polymer chemistry, and more specifically to a new method for modifying the surface of a granulate of polyethylene terephthalate (PET) with functional additives to increase thermo-, photo-, wear- and hydrolytic resistance, as well as to reduce the gas permeability of polymeric materials, which can be used in the manufacture of containers, packaging, fibers and tribological products.

There is a method of modifying PET with a functional additive, which is sodium oligoethylene oxide sulfonate (Copyright certificate of the Russian Federation No. 1407014, IPC ⁵ C08G 65/48, publ. 15.08.1994):

HO- (CH ₂ CH ₂ O) _n -CH ₂ -CH (SO ₃ Na) -CH ₂ OH (n = 8-20).

The disadvantages of this method are the polymolecularity of the modifier, which determines its different reactivity to chemical bonding with the polymer, as well as undesirable partial sweating from the polymer matrix.

A known method of obtaining a heat-resistant polymer composition for structural materials, including complex polyester (PET) and a modifier, the latter of which is a polyarylate oxime based on dichlorohydrides of tere- and isophthalic acids and phenol ketoxime containing a phthalide moiety, containing a modifier in the polymer matrix of 0.05- 1 wt.% (RF Patent No. 2303612, C08L 67/02, C08K 5/10, publ. 07.27.2007):

The disadvantages of this method include the complexity of the chemical binding of modifier molecules to polyethylene terephthalate and the inaccessibility of the modifier used.

Heat-resistant polyesters are known, obtained by esterification of aromatic polycarboxylic acid (or its anhydride) with alcohol H (CF ₂ CF ₂ ) _n CH ₂ OH (n = 1-5) or a mixture of telomeric alcohols in the presence of an acid catalyst and having the formula (m = 3- 4, n = 1-5) (US Patent 3004061, 1962; RZhKhim, 1963, 1P170; Ponomarenko, V.A. Fluorine-containing heterochain polymers / V.A. Ponomarenko, S.P. Krukovsky, A.Yu. Albina .-- M.: Science. - 1973. - 271 p.):

C ₆ H _6-m [COOCH ₂ (CF ₂ CF ₂ ) _n H] _m

The disadvantages of this method are the complexity of the esterification reaction due to the low reactivity of polyfluorinated telomeric alcohols, as well as a partial decrease in the molecular weight of the polyester due to acid hydrolysis with an acidic esterification catalyst.

Heat-resistant polyesters based on hexafluoropentanediol and 1,5-diphenoxypentan-n, n ^/ -dicarboxylic acid (structure I) and poly (hexafluoropentamethyleneoxy-bis-benzoate) (structure II) (Ponomarenko, V.A. Fluorine-containing hetero-chain polymers are known) / V.A. Ponomarenko, S.P. Krukovsky, A.Yu. Albina. - M.: Science. - 1973. - 271 p.):

The disadvantages of these methods for producing heat-resistant polyesters are the reduced reactivity of fluorinated alcohols, which makes it difficult to obtain polymers with high yields.

A known method of producing complex fatty-aromatic polyesters with increased heat resistance, based on the use of heat-stabilizing systems, including spatially hindered phenol, trinonylphenyl phosphate or three (2,4-ditretbutylphenyl) phosphite, calcium hypophosphite, and organically modified clay (bentonite, nalchikite) (RF Patent No. 2345098, C08G 63/183, C08G 63/84, published January 27, 2009).

The disadvantages of this method are the multicomponent stabilizing composition, as well as the low compatibility of inorganic components with an organic polymer matrix.

The closest is the method of volumetric modification of polymeric materials (granules, films, fibers) without changing their geometric shape (RF Patent No. 2110404, B29C 71/00, C08J 7/12, publ. 05/10/1998). This method involves heating a polymeric material (PET) in the range from the temperature of the first relaxation transition to a temperature lower than the melting point or the temperature of destruction and treatment with vapor of a modifying substance (crystalline anthracene) in an appropriate temperature range at a partial air pressure of no higher than 10000 Pa.

The disadvantages of this method are the low adhesion of the modifier to the polymer surface, due to the lack of chemical interaction between anthracene and PET, the difficulty of uniform distribution of the modifying additive on the polymer surface, and the use of vacuum to modify the polymer.

Objective: the development of a technologically advanced method for modifying the surface of polyethylene terephthalate granulate to obtain polyethylene terephthalate with increased heat resistance.

The technical result of the proposed method is the possibility of expanding the temperature range of operation of products made of polyethylene terephthalate due to chemical bonding of the modifier used (fluorine-containing prepolymer with isocyanate groups) to the complex polyester by reaction of isocyanate groups of the prepolymer with terminal carboxyl groups of polyethylene terephthalate with subsequent branching of the macromolecular molecular chain biuret and acylurea groups, as well e associative interaction perfluorocarbon chain methylene-polyester fragments, thereby increasing the heat resistance of the polymer.

The technical result achieved is achieved in a method of modifying the surface of a polyethylene terephthalate granulate by treating it with a modifier when heated, and fluorine-containing prepolymers in an amount of 2% by weight are used as a modifier. 100% of the mass. polyethylene terephthalate of the following general formulas with a mass ratio of 90 (I): 3 (II): 7 (III):

preliminarily obtained as the product of the interaction of the trimer of hexamethylene diisocyanate with the content of isocyanate groups of 21.8-22.1% with 1,1,7-trihydroperfluoroheptanol-1 in the presence of catalytic amounts of tin di-n-butyldylaurinate at a molar ratio of reactants 1: 1: 0.005, respectively , in a medium of nitromethane and n-hexane with a volume ratio of 1: 6, at a temperature of 90 ° C, an ultrasound frequency of 40 kHz for 2 hours, while the modification is carried out in a medium of chlorobenzene at 150 ° C for 4 hours in the presence of catalytic amounts di-n-butyldyl tin Rinat.

The chemical interaction of the isocyanate groups of the prepolymer with the terminal carboxyl groups of PET under the conditions of catalysis with tin di-n-butyldylaurinate leads to the formation of a mixed anhydride, which is able to eliminate carbon dioxide to form amide groups. The branching of the macromolecular chain occurs due to the interaction of the isocyanate groups of the fluorine-containing prepolymer with the HN groups of the extended macromolecular chain and with the HN groups of neighboring prepolymer molecules:

The advantages of the surface modification method for PET granulate are the high solubility of the modifier in chlorobenzene, which provides a more uniform surface modification of polyethylene terephthalate, and the interaction between the functional groups of the fluorine-containing prepolymer with a complex polyester contributes to the chemical “fixing” of the modifier on the surface of the PET.

Use PET granulate produced by POLIEF OJSC with a content of terminal carboxyl groups equal to 30 mEq / kg (TU 2226-008-39989731-2009).

As the organotin catalyst, tin di-n-butyldylaurinate (TU 6-02-818-78) is used in the form of 0.5% by weight. solution in chlorobenzene.

As solvents, nitromethane, n-hexane and chlorobenzene of qualification “Ch.D.A.” are used.

As a modifier, a fluorine-containing prepolymer with isocyanate groups obtained by the reaction of a hexamethylene diisocyanate trimmer with 1,1,7-trihydroperfluoroheptanol-1 in the presence of catalytic amounts of tin di-n-butyldylaurinate is used as a modifier.

Example. In a glass flask with a reflux condenser equipped with a calcium chloride tube, 40 ml of a mixture of nitromethane and n-hexane are placed in a volume ratio of 1: 6, respectively, 1 g (0.002 mol) of hexamethylene diisocyanate trimer, 0.4 ml (0.002 mol) of 1.1.7 -trihydroperfluoro-heptanol-1 and 0.1 ml of tin di-n-butyldylaurinate are added dropwise in the form of 0.5% by weight. solution in nitromethane. The flask was thermostated at a temperature of 90 ° C for 2 hours at an ultrasound frequency of 40 kHz. The resulting reaction product is subjected to fractionation: prepolymer (I) is soluble in chlorobenzene at 25 ° C, prepolymer (II) is slightly soluble at 25 ° C in chlorobenzene and prepolymer (III) is soluble in chlorobenzene at 80 ° C. The product is washed with n-hexane, dried over anhydrous calcium chloride and stored in sealed ampoules. The degree of conversion of 1,1,7-trihydroperfluoroheptanol-1 is 61.25%. The content of isocyanate groups in the mixture of prepolymers 10.4-11.7% of the mass.

Prepolymer (I). The liquid is a dull white color. Found: N 5.56-5.70%, F 45.67-46.12. IR spectrum, ν, cm ^-1 : 3182-3071 (ν _NH ), 2900-2987 (ν _CH ), 2342 (ν _NCO ), 1817 (ν _{C = O} , carbamic), 1662 (amide I), 1558 ( amide II), 1461 (amide III), 1207-1193 (CF). ¹ H NMR spectrum (CCl ₄ ), δ, ppm: 6.83 s (C (O) NH ), 5.71 t (CF ₂ H , J ₁ = 50.2 Hz, J ₂ = 6.0 Hz), 4.68 t (C H ₂ -CF ₂ , J = 13.9 Hz), 3.51 m (C H ₂ -NCO, C H -NCO), 3.17 m (C H -NHC (O), C H ₂ -NHC (O)), 1.27-1.52 m (6H, (CH ₂ ) ₃ ). ¹³ C NMR spectrum (DMSO-d ₆ ), δ, ppm: 160.20 (> C = O carbamic), 110.42-118.50 ( C F ₂ ), 122.30 (N C O) 58.10 (O- C H ₂ -CF ₂ ), 25.07-44.20 ( C H ₂ , C H).

Prepolymer (II). The liquid is a dull white color. Found: N 3.35-3.38%, F 53.86-54.02. IR spectrum, ν, cm ^-1 : 3320-3100 (ν _NH ), 2912-2931 (ν _CH ), 1820 (ν _{C = O} , carbamic), 1663 (amide I), 1556 (amide II), 1469 ( amide III), 1211-1115 (CF). ¹ H NMR spectrum (CCl ₄ ), δ, ppm: 6.84 s (C (O) N H ), 5.70 tp (CF ₂ H , J ₁ = 50.2 Hz, J ₂ = 6.0 Hz), 4.69 t (C H ₂ -CF ₂ , J = 13.9 Hz), 3.51 m (C H ₂ -NHC (O), C H -NHC (O)), 3.15 m (C H -NHC (O), C H ₂ -NHC (O)), 1.29-1.50 m (6H, (CH ₂ ) ₃ ). ¹³ C NMR spectrum (DMSO-d ₆ ), δ, ppm: 157.40 (> C = O carbamic), 112.03-115.97 ( C F ₂ ), 57.18 (O- C H ₂ -CF ₂ ) 24.11-46.41 ( C H ₂ , C H).

Prepolymer (III). The liquid is a dull white color. Found: N, 6.12-8.01%; F, 35.12-37.03. IR spectrum, ν, cm ^-1 : 3345-3118 (ν _NH ), 2927-2990 (ν _CH ), 1881 (ν _{C = O} , carbamic), 1874 (ν _{C = O} , isocyanurate), 1660 (amide I ), 1551-1560 (amide II), 1460-1485 (amide III), 1201-1182 (CF). ¹ H NMR spectrum (CCl ₄ ), δ, ppm: 6.90 s (C (O) NH), 5.71 t (CF ₂ H , J ₁ = 50.2 Hz, J ₂ = 6.0 Hz), 4.68 t (C H ₂ -CF ₂ , J = 13.9 Hz), 3.50 m (C H ₂ -NHC (O), C H -NHC (O)), 3 17 m (CH-NHC (O), C H ₂ -NHC (O)), 1.26-1.48 m (CH ₂ ). ¹³ C NMR spectrum (DMSO-d ₆ ), δ, ppm: 158.57 (> C = O, carbamic), 154.12 (> C = O, isocyanurate), 111.82-116.05 ( C F ₂ ), 55.07 (O- C H ₂ -CF ₂ ) 24.43-45.82 ( C H ₂ , C H).

The claimed method is as follows.

A solvent (chlorobenzene), granulate PET, a modifier (fluorine-containing prepolymer with isocyanate groups) and catalytic amounts of tin di-n-butyldylaurinate are placed in the flask, heated to 150 ° C and incubated for 4 hours, then the modified PET granulate is separated and dried.

The invention is illustrated by the following example.

100 g of PET granulate, 2 g of a fluorine-containing prepolymer with isocyanate groups, 150 ml of chlorobenzene containing 0.001 g of tin di-n-butyldylaurinate are charged into a glass flask. The flask was thermostated at a temperature of 150 ° C for 4 hours. The modified PET granulate was separated and dried at 100 ° C in vacuo. The degree of conversion of the fluorine-containing prepolymer with isocyanate groups is 81.7%.

Modified PET granulate. IR spectrum, ν, cm ^-1 : 3392 (superposition of ν _{0-H (COOH)} and ν _NH ), 2873 (v _CH ), 1820.4 (ν _{C = O} , anhydride), 1780 (ν _{C = O} , ester, carbamic and amide).

The table shows the data of thermo-oxidative degradation of the initial and modified PET.

Table Thermooxidative degradation of the starting and modified PET * Sample Temperature at which corresponding weight loss occurs, ° C T _beg Δm = 5% Δm = 10% Δm = 15% Δm = 20% Δm = 30% Δm = 40% Δm = 50% PAT 282 368 382 387 392 394 400 487 Modified PET 287 382 398 409 412 417 420 490 * studies were conducted in the temperature range 23-600 ° C.

The temperature of the surface modification of PET granulate, which was 150 ° C, is optimal, since it provides high solubility of the fluorine-containing prepolymer with isocyanate groups in chlorobenzene, as well as the reactivity of isocyanate groups to the formation of allophanate, biuret, and acylurea fragments. An increase in the modification temperature above 150 ° C leads to an undesirable partial dissolution of PET granulate and their shape deformation, as well as dehydrofluorination of the perfluorocarbon chain. Lowering the temperature to less than 150 ° C reduces the degree of conversion of the modifier and the thermo-oxidative stability of the modified PET.

The increase in the time of surface modification of PET granulate over 4 hours contributes to their partial dissolution. Reducing the modification time of less than 4 hours leads to a decrease in the degree of conversion of the modifier and the thermal oxidative stability of the modified PET.

The increase in the amount of modifier over 2 parts by weight leads to a decrease in the temperature of the onset of thermal oxidative degradation. The decrease in the content of the modifier is less than 2 parts by weight helps to reduce thermal oxidative stability over the entire investigated temperature range.

The use of catalytic amounts of tin di-n-butyldylaurinate has a positive effect on increasing the degree of conversion of the modifier, which helps to increase the thermo-oxidative stability of the modified PET.

IR spectra of substances were recorded on a Nicolet-6700 IR Fourier spectrometer and a Specord-M82 spectrometer.

NMR spectra ( ¹ H and ¹³ C) of the substances were recorded on a Varian Mercury Plus instrument (operating frequency 300 MHz, internal standard tetramethylsilane).

The thermal oxidative stability of the samples of the starting and modified PET was studied in the temperature range 23–600 ° C on a Q-1000 derivatograph of the Paulik – Paulik – Erdey system (MOM, Hungary) in an air atmosphere.

Thus, a technological method has been developed for modifying the surface of PET granulate by treating it with a fluorine-containing prepolymer with isocyanate groups in chlorobenzene at 150 ° C for 4 hours in the presence of catalytic amounts of tin di-n-butyldylaurinate, which allows to increase the thermal-oxidative stability of modified PET, which allows to extend the interval operation of polyester products and increase the convenience of processing this polymer.

Claims (1)

A method of modifying the surface of a granule of polyethylene terephthalate, including treating it with a modifier when heated, using fluorine-containing prepolymers in an amount of 2 wt.% Per 100 wt.% Polyethylene terephthalate of the following general formulas with a mass ratio of 90 (I): 3 (II): 7 ( III)

preliminarily obtained as the product of the interaction of the trimer of hexamethylene diisocyanate with the content of isocyanate groups of 21.8-22.1% with 1,1,7-trihydroperfluoroheptanol-1 in the presence of catalytic amounts of tin di-n-butyldylaurinate at a molar ratio of reactants 1: 1: 0.005, respectively , in a medium of nitromethane and n-hexane at a volume ratio of 1: 6, at a temperature of 90 ° C, an ultrasound frequency of 40 kHz for 2 hours, while the modification is carried out in a medium of chlorobenzene at 150 ° C for 4 hours in the presence of catalytic amounts di-n-butyldyl tin urinata.