CS262095B1 - Process for preparing microporous sorbent from polyethylenterephthalate and copolymers thereof - Google Patents

Abstract

Microporous selective sorbents of polyethylene terephthalate and copolymers thereof in the form of dust, granules, fibers, hollow, planar and shaped bodies are obtained by treating a polymer containing from 5 to 50% by weight of calcium carbonate with an aqueous solution of 1.0 wt. to 20 forming water-soluble calcium salts, preferably hydrochloric acid and acetic acid, at a temperature of 20 to 95%; for 1 to 100 hours in both static and dynamic conditions, with the relative viscosity of the polymer being at least 25 ml. g "1 and the degree of porosity is at most 50%. The sorbents are useful in the food and healthcare industries, as well as dye and chemical sorbents, for the separation of gaseous and liquid substances and as sorbents for wastewater filters.

Description

The present invention relates to a process for the preparation of a microporous sorbent from polyethylene terephthalate and its copolymers with selective sorption and separation properties by treating an aqueous solution of an acid with a calcium carbonate-containing polymer.

A number of processes are currently known for preparing sorbents from polyethylene terephthalate. For example, JP 167 969/85 describes a process for preparing moisture-absorbing polyester fibers having a thick skin with pores formed by dissolving at least 2% of the surface of a dispersed polyethylene glycol-5-Na-sulfoisophthalic acid type compound. According to JP 87 807/85, the hollow fibers are coated with polymer by passing two successive solutions. The first solution comprises a polymer forming a polycondensation polymer. EP 150 699 discloses a process for the production of a polyphosphazene-coated porous laminated membrane. JP 222 112/85 discloses hollow filter fibers prepared by polymerizing an organic sulfo compound containing a benzene core. JP 133 105/86 describes the production of membranes from an oriented crystalline polymer which is treated with a surfactant in the form of an aqueous solution or suspension. Reagent · enters the micropores and the membrane is then dried. These are mostly complicated methods of sorbent preparation, which use organic components to achieve microporosity. Powder sorbent is produced on this basis in Czechoslovakia, eg according to AO No. 171923, when the powdered polyester is dissolved in the lactams melt. The resulting homogeneous melt, or the solidified mixture upon cooling, is transferred to the lactam solvents, and the precipitated powdered polyester is separated. This method of production is demanding in the treatment and disposal of waste water.

For the preparation of microporous fibers for textile purposes using an inorganic additive - calcium carbonate in amounts up to 5 wt. A process for the preparation of microporous polymers for technical purposes, predominantly in the form of non-oriented polyester structures with high calcium carbonate contents throughout the polymer cross-section, with different shape characteristics and predominantly low relative viscosities of the polymer, is not disclosed.

Disadvantages of the prior art are eliminated by a process for the preparation of a microporous polymer sorbent from polyethylene terephthalate and its copolymers with selective sorption and separation properties, in the form of dust, granules, fibers, hollow, planar and shaped bodies, which consists in 5 to 50% of calcium carbonate is treated with an aqueous solution of acid at a concentration of 1.0 to 20% by weight, forming water-soluble calcium salts, preferably hydrochloric and acetic acid, at a temperature of 20 to 95 ° C for 1 to 100 hours in static and dynamic state, the relative viscosity of the polymer is at least 25 ml.g ^-1 and the degree of porosity is at most 50 ° / o.

The advantage of the preparation of the sorbents according to the invention is a simple technological process, common additive and other necessary chemicals. Production can be carried out on existing machines and equipment. By controlling the relationships between the amount of calcium carbonate in the polymer, the viscosity and shape of the polymer, the type of acid, its concentration, time and temperature of action, the selectivity of both sorption and separation properties can be influenced, which is an advantage of the process. The chemically inert additive allows the use of sorbents, especially in the food and medical industries. The higher performance in comparison with prior art methods is achieved by the universal properties of sorbents even in specific applications. A higher effect is also achieved by the fact that the sorbent used can be regenerated, thereby reducing the cost of the process. The high sorption efficiency allows the use of sorbents in water purification and removal of even trace amounts of undesirable substances in aqueous solutions, which is of particular importance in the environmental field. The sorbents prepared according to the invention are used in the areas which are hitherto tied to import or high domestic prices.

The principle of carrying out a process for preparing a microporous sorbent from polyethylene terephthalate and its copolymers is illustrated in the following examples, the percentages being by weight.

Example

Polyethylene terephthalate polymer was produced with a standard process containing 45% calcium carbonate with a relative viscosity of 38 ml. g ^_1 . The polymer was further processed to a granule of oval cross-section of 3x2 mm and a length of 3 mm, which was poured into a water bath containing 5% hydrochloric acid and kept under stirring at 60 ° C for 84 hours. The bath was then drained, the granulate washed 3 times with water and dried. The granulate thus prepared has a porous character with a porosity of 15 to 20%.

Example 2

Of polyethylene terephthalate polymer containing 23% calcium carbonate with a relative viscosity of 54 ml. g ^-1 , an undrawn fiber having a length of 1.9 tex was produced. At winding, a 13.5 percent acetic acid solution was applied to the fiber at 25 ° C. After 50 hours of solution treatment, the fiber was passed through a water bath and heat treated at 170 ° C. The crystallized fiber was ground to a dust with a porosity of 12-15%.

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Example 3

Of polyethylene terephthalate polymer containing 13% calcium carbonate with a relative viscosity of 63 ml. g ^-1 , a hollow fiber having a length of 2.45 tex and a cavity size of 14% of the total cross-section was produced. The fiber was passed through a water bath containing 5% acetic acid at 35 ° C for 38 hours. The fiber was then lengthened to a length of 0.69 tex in a standard manner and processed to a staple length of 85 mm.

Example 4 'Ή' (in k '·

A mixture of hard crushed polyethylene terephthalate waste containing 17% calcium carbonate, polyethylene terephthalate and modified polymers with 2 mole% sulfoisophthalic units was spun. The undrawn fiber was treated with a 10% hydrochloric acid solution at 8-5 ° C for 16 hours. The elongated 1.1 tex fiber, containing 5.2% calcium carbonate with a porosity of 8 to 10 percent, was processed into a sheet.

The microporous polymeric sorbent of polyethylene terephthalate according to the invention can be used in the food and medical industry as sorbents of dyes and chemicals, as well as carriers thereof, as sorption fillers of filters, for the separation of gaseous and liquid substances and the like.

Claims (1)

Process for the preparation of microporous sorbent from polyethylene terephthalate and its copolymers with selective sorption and separation properties, in the form of dust, granules, fibers, hollow, planar and shaped bodies with a porosity degree of not more than 50%, characterized in that a viscosity of at least 25 ml. g- ¹ with a content of 5 to 50% by weight of calcium carbonate acts with an aqueous solution of acid at a concentration of 1.0 to 20% by weight, forming water-soluble calcium salts, preferably hydrochloric and acetic acid at a temperature of 20 to 95 ° C for 1 to 100 hours in static and dynamic state.