SU567309A1 - Method of waste processing - Google Patents

Description

The invention relates to the production of polymeric materials and can be used for obtaining granular polyethylene terephthalate (PET) from secondary raw materials,

It is known that during the processing of fibrous and film waste into granular PET by extrusion, significant degradation of the polymer occurs due to the presence of residual moisture in the waste, which cannot be removed by drying and causes violent hydrolysis of the polymer during extrusion, and increased, in comparison with the primary material , content of end groups.

This disadvantage leads to a limitation of the use of recycled granular PET and in most cases causes its use in the main production in which waste is generated. The degradation process reduces the viscosity of the polymer melt, which makes it difficult to extrude waste and obtain a granular product from it.

There is a known method of regeneration (PET) from waste, according to which an increase in the molecular weight of the polymer is achieved by passing 0.1-2% of ethylene oxide through its melt. Subsequently, the excess ethylene oxide is removed from the melt. The disadvantages of this method are:

a) the use of a gaseous modifying agent (ethylene oxide), which complicates the process and significantly complicates the design of extrusion and other types of equipment for melting polymer waste;

b) the need to introduce an additional stage of the process - removal of excess ethylene oxide;

c) the multistage process and the use of gaseous products, which limits the possibility of reducing the thermal load on the recycled PET waste.

There is also known a method of reusing linear polyester resins, which consists in the fact that a linear polyester high polymer is mixed with 0.15-0.47 mol (per 1 mol of a dicarboxylic acid unit in the polymer) of water or compounds from which the polyester is obtained, at 260-320 ° C and a pressure of 1.4-21 kg / cm ² in a screw extruder, thus a degraded material is obtained, the degree of polymerization of which depends on the duration of the process, i.e. the purpose of this method is the degradation of the high polymer to obtain low molecular weight products in the extruder.

The method for solid-phase polymerization of PET waste provides for the processing of crushed polymer waste in an oven at 220-250 ° C (i.e. below the melting temperature) in an inert gas atmosphere. In this case, solid-phase polycondensation of the polymer and an increase in viscosity occur due to the intensive removal of volatiles, glycol and reaction water from the dispersed material (film thickness 2-20 microns). The duration of the operation is 2-4 hours. Then the depolymerized material is either rapidly cooled in a dry atmosphere, or in a heated state is fed into the extruder.

The prototype of the invention is a method for processing polyester waste (including PET waste) by extrusion of a mixture of waste with 0.015-0.047 mol per 1 mol of acid contained in the polymer, a destructive agent, which is used as glycols, organic dicarboxylic acids and lower alkyl or phenyl esters organic dicarboxylic acids, at 260-320 ° C.

However, this method provides for depolymerization of high molecular weight polyesters to obtain low molecular weight products, followed by loading the obtained products into a reactor, where additional polycondensation is carried out for 105-129 minutes in a known manner in order to obtain a high polymer. During PET extrusion, a sharp decrease in specific viscosity occurs and the extruded product is no longer suitable for use: in the production of films, fibers, for injection molding compositions.

The purpose of the invention is to increase the thermal stability of recycled polyethylene terephthalate raw materials during its processing.

An increase in the thermal stability of secondary PET should be understood as the resistance of the secondary material to destructive depolymerization when the material is exposed to elevated temperatures. developed during PET extrusion.

This goal is achieved in that 0.022% by weight of dry waste of a compound selected from the group consisting of anhydrides of organic dicarboxylic acids, phenyl esters of inorganic polybasic acids and esters of polybasic inorganic acids and substituted phenol is used as a functional additive.

Anhydrides of organic dicarboxylic acids are used in an amount of 0.05-2.0% of. mass of dry crushed PET, and esters of inorganic polybasic acids in the amount of 0.02-2.00%.

The optimum concentration of anhydride in the processed waste is 0.05-0.5%. A further increase in its content somewhat reduces the effect of reducing the degree of destruction of waste in the process of extrusion. This phenomenon is explained by an increase in the content of free anhydride in rPET.

The amount of anhydride is selected depending on its reactivity and compatibility with the polymer melt. Therefore, the amount of higher melting point and less reactive anhydrides is the highest, up to 2%. This is especially true for the anhydrides of heterocyclic compounds; imidazole, pyrosol, pyrazine, pyrol (which also play the role of antioxidants in the extrusion process), as well as for anhydrides based on condensed aromatic compounds: naphthalene, carbazole, pyrene, etc.

The optimum concentration of phenyl ethers in secondary PET is 0.04-0.3%. A further increase in concentration is undesirable due to the fact that the presence of a free inorganic acid in the polyester leads to the destruction of the ester group, i.e. a decrease in the molecular weight of PET. Therefore, the introduction of esters of weaker acids (carbonic) is preferable.

Thus, the concentration of esters (percentage of the weight of dry PET waste) is selected taking into account the possibility of using compounds with a large molecular weight (such as tridodecylphenyl phosphate, etc.), the reactivity of the esters, and possible fluctuations in the moisture content in the processed waste.

During the extrusion process, the functional additive interacts with the water contained in the waste, preventing hydrolysis of PET. The anhydrides of organic dicarboxylic acids form a dicarboxylic acid. The proposed method uses anhydrides of aromatic, cycloaliphatic and heterocyclic dicarboxylic acids, which are easily hydrolyzed and are well combined with PET.

Acid anhydrides are used: phthalic, methyltetrahydrophthalic, maleic. amber, pyrazine-2,3-dicarboxylic, imidazole dicarboxylic, etc.

Secondary PET contains an excessive amount of terminal hydroxyl groups in comparison with carboxyl groups, which contributes to the thermal destruction of the polymer. The dicarboxylic acid formed as a result of hydrolysis of the anhydride increases the content of carboxyl groups and, thus, a correspondence between the hydroxyl and carboxyl groups in the secondary polymer is achieved. At the same time, 5 dicarboxylic acid interacts with the hydroxyl groups of PET, crosslinking its macromolecules and thereby increasing the molecular weight of secondary PET. The water released in this case is bound by the dicarboxylic anhydride present in some excess.

When phenyl esters of inorganic polybasic acids are used, phenol or 15 of its substituted acids are liberated during extrusion. The inorganic acid interacts with the hydroxyl end groups of secondary PET macromolecules, the increased content of which. in comparison with carboxyl, 20 allows the released acids to crosslink macromolecules, thereby increasing the molecular weight of secondary PET. Free phenol or its substituted plays the role of a plasticizer, stabilizer 25 of oxidative destruction And nucleating structure in secondary PET, while improving its physical and mechanical properties. It becomes possible to regulate them. ’

The proposed method uses: diphenyl ester of carbonic acid, triphenyl ester of orthophosphoric acid, triphenyl ester of phosphorous acid and esters of the above polybasic acids and substituted phenols of the general formula S> -o-p-o- <X

R - about ^R 0 where R is CH3, C2H5, Hal. NO2.

Before extrusion, the waste is pre-dried even when processing PET waste directly in the composition of film or fiber production, the equilibrium moisture content of the material is at the level of 0.2-0.3%. If the waste is collected at various plants and transported to an enterprise for centralized processing, then the process scheme provides for the cleaning and drying of the crushed material.

Thus, in the existing production environment, drying in the proposed process is necessary.

Residual moisture in the amount of 0.01-0.02% is quite sufficient for a very noticeable depolymerization of PET during extrusion.

The additives used bind water both present in the secondary PET prior to extrusion, and released as a result of thermooxidative destruction of the waste material during extrusion.

Table 1 shows the properties of secondary PET, regenerated by the proposed method.

The obtained granular PET possesses a sufficiently high melt viscosity and can be used as an additive to primary raw materials in the production of fibers, films, and other products and as an independent material.

The use of anhydrides of dicarboxylic acids makes it possible to increase the molecular weight of secondary PET by 3000-4000 (up to 15000-18000).

The structure-forming effect of esters of inorganic acids is manifested in an increase in the degree of crystallinity of injection molded articles made of secondary PET from 4 to 17% when molded into a cooled mold.

PRI me R 1. Waste, cleaned from contamination, generated during the production of polyethylene terephthalate film, crushed on a rotary grinder of plastics to obtain particles of 1-5 mm in size. The crushed waste is mixed with 0.1% phthalic anhydride. Then the mixture is dried at 60-70 ° C to a residual moisture content of 0.01-0.02% and extruded at 265 ° C into a granular material. The resulting secondary PET has a specific solution viscosity of 0.25 (initial viscosity of the waste material is 0.29) and can be processed into articles by extrusion and injection molding.

Example 2. The fibrous polyethylene terephthalate waste purified from contamination is crushed on a rotary knife grinder of plastics to a fiber size of 1-20 mm and then mixed with 0.1% methyltetrahydrophthalic acid anhydride. The resulting mixture is dried at 60-70 ° C to a residual moisture content of 0.01-0.02% and then extruded into granular secondary PET.

The reclaimed polymer has a solution specific viscosity of 0.27 with a waste starting material of 0.31.

PRI me R 3. Same as in example 1. 0.2% of succinic anhydride is used as an additive. The resulting polymer has a specific solution viscosity of 0.26. End group content, g-eq: 10 ⁶ : OH 137, COOH 128.

Example 4. Same as in example 1. As an additive, pyrazine-2,3-dicarboxylic acid anhydride is used in an amount of 0.25%. A polymer with a specific solution viscosity of 0.24 is obtained. End group content, g-eq: 10 ^b : OH 145, COOH 131.

PRI me R 5. Waste, cleaned from contamination, generated during the production of polyethylene terephthalate film, crushed on a rotary grinder of plastics, to obtain particles with a size of 1-5 mm. The crushed waste is mixed with 0.1% diphenyl ester of carbonic acid, the mixture is dried at 60-70 ° C to a residual moisture content of 0.01-0.02% and extruded at 265 ° C into granular material. The resulting secondary PET has a specific solution viscosity in tricresol of 0.26 at a feed viscosity of 0.29 and can be processed into articles by extrusion and injection molding. The degree of crystallinity is 14%.

PRI me R 6. The fibrous polyethylene terephthalate waste cleaned from contamination is crushed on a rotary knife grinder of plastics to a fiber size of 1-20 mm and then mixed with 0.05% triphenyl phosphate. The mixture is dried at 60-70 ° C to a residual moisture content of 0.010.02% and extruded at 265 ° C into a granular material. Regenerated PET has a specific solution viscosity in tricresol of 0.26 at a feedstock viscosity of 0.31. The degree of crystallinity is 15%.

PRI me R 7. The same as in example 5. As an additive used 0.1% dikresyl ester of carbonic acid. Get secondary PET with a specific viscosity of the solution in tricresol 0.26. The degree of crystallinity is 16%.

PRI me R 8. The same. that in example 6. As an additive used 0.1% dikresyl ester of carbonic acid. A polymer with a specific solution viscosity of 0.27 is obtained. The degree of crystallinity is 15%.

PRI me R 9. The same as in example 1. As an additive use 1.75 May. % anhydride of 1,5-imidazole dicarboxylic acid and 0.25 wt.% (then the mass of dry ground material) anhydride 1,8 naphthalenedicarboxylic acid. A polymer with a specific solution viscosity of 0.23 is obtained. End group content, g-eq: 10 ⁶ : OH 192, COOH 141.

PRI me R 10. The same as in example 1. As an additive used 0.02 wt.% (By weight of dry ground material) maleic anhydride. A polymer with a specific viscosity of 0.25 is obtained. The content of end groups for the resulting granulate in g-eq: 10 ^b : OH 137; COOH 141.

Example 11. The same as in example 5. As an additive, 2% tri-n-to-N-ecylphenylphosphite is used. Get secondary

PET with a specific viscosity of a solution in tricresol of 0.25. The degree of crystallinity of the samples cast into a mold cooled to 3035 ° C is 11%.

PRI me R 12. The same as in example 5. The moisture content of the feedstock is 0.05%. 2% tri-n-octylphenyl phosphate is used as an additive. A polymer with a solution viscosity of 0.24 is obtained. The crystallinity of the cast samples is 13%.

PRI me R 13. The same as in example 5. As an additive used 0.02% (by weight of dry PET waste) triphenylphosphite. A polymer with a solution viscosity of 0.25 is obtained. The degree of crystallinity is 15%.

PRI me R 14. The same. that in example 5. As an additive used 0.1% tricresyl phosphite. A polymer with a solution viscosity of 0.26 is obtained. The degree of crystallinity is 17%.

PRI me R 15. The same. that in example 6. 20 As an additive used 0.1% triethylphenylphosphite. A polymer with a solution viscosity of 0.27 is obtained. The degree of crystallinity is 16%.

PRI me R 16. The same. that in example 6. As an additive used 0.05% tri-chlorophenylphosphite. A polymer with a solution viscosity of 0.27 is obtained. The crystallinity is 19%.

PRI me R 17. The same as in example 6. As an additive used 0.05% tri-pnitrophenyl phosphate. A polymer with a solution viscosity of 0.26 is obtained. The degree of crystallinity is 18%. ...

Table 2 shows the physical and mechanical properties of injection molded samples obtained from granulated secondary PET by extrusion.

The described method of processing PET waste into granular material and articles by extrusion provides a decrease in material destruction and an increase in the molecular weight of the secondary material.

The proposed method can be used to obtain granular PET and products from waste and provides the regeneration of PET, which slightly differs in its properties from the feedstock. The secondary high-molecular-weight product can be used for the production of fiber, film and injection molded products.

The above calculations show that the economic effect from the production of secondary granular PET and the subsequent use of its primary material will amount to 700-750 rubles / ton.

instead of (56) US Patent No. 3350328, cl. 260-2.3. 1967.

French application No. 2004490, cl. C 08 g 53/00, 1970.

US patent No. 3767601. class. 260-2.3. 1973.

US patent No. 3703488. class. 260-2.3, 1972.

Table 1

Material The content of terminal groups, TSP-d ^s · 10 Specific viscosity 0.5% solution in tricresole IT soon Waste film ori- oriented 150 72 0.29 Granulate obtained by extrusion of film waste 189 117 0.19 Granulate obtained by extrusion of film waste with the addition of: a) 0.1% methyltetrahydrophthalic acid anhydride 144 126 0.23

³ 11

Continuation of table. 1

Material End group content, g-eq · 10 " Specific viscosity of 0.5% solution in tricresol IT UNSD b) 0.05% triphenyl phosphate Waste fiber Waste fiber, granulated by extrusion Granulate from waste fiber with an additive: a) 0.1% phthalic an- hydride b) 0.1% of diphenyl ether of coal, acid 99 164 191 ¹³⁵ 128 135 68 126 142 ... 92 ' 0.23 0.31 0.21 0.25 ⁰²⁷

Table 2

Material Breaking strength, kg / cm ² Elongation at break. % Flexural strength, kgf / cm ² Impact strength, kg.cm / cm ² Wounded from waste 370 17 350 13 film production (GOPP) 130 * 230 35 470 90 18 GOPP + 0.1% diphenyl carbonate 440 155 24 210 18 nineteen GOPP + 0.1% 420 22 610 sixteen triphenylphospha- 170 thirty 140 ^sixteen 'that ..

* - In the denominator, data on the same properties, but at 80 ° C.

Lfo-rmula invention

Claims (1)

METHOD FOR PROCESSING WASTE η of polyethylene terephthalate by extrusion of a mixture of PET waste with a functional additive at 260 - 320 * C, characterized in that, in order to increase the thermal stability of secondary polyethylene terephthalate raw materials during its processing, 0.02 - 2% of the dry weight is used as a functional additive waste compounds selected from the group consisting of anhydrides of organic dicarboxylic acids, phenyl esters of inorganic polybasic acids and esters of polybasic inorganic acids and substituted phenol.