SK278607B6 - Method for preparation of the shaped segments from the cellulose derivatives - Google Patents

Abstract

This patent describes a procedure closed to the preparation of the shaped segments based on the cellulose derivatives, while the alkaline solution of xanthogenate and carbamate are used and mixed, however the mixture solution, containing 1 up to 99 percent of carbamate, while 20 up to 60 percent of is suitable to use, is spinned into the acid coagulation bath.

Description

Technical field

The invention relates to the chemical part of the production of chemical shaped articles, in particular films and fibers, by mixing two cellulose derivatives, xanthate and carbamate in the form of alkaline solutions. It belongs to the fiber industry and packaging industry.

BACKGROUND OF THE INVENTION

The most widespread method for producing cellulose-based shaped cells is the carbon-carbon process for producing cellulose xanthate by the action of carbon disulfide on alkali cellulose. The cellulose xanthate dissolves in dilute alkali to form viscoses, which is passed through a defined opening into an acid bath where coagulation and concomitant release of carbon disulphide and hydrogen sulfide by-products occur. The resulting pollutants pollute the working and municipal air.

The negative impact on the environment dominates in determining the development trend in natural cellulose processing and predetermines its further development. This is in particular taken to replace the viscose process for producing shaped cells from regenerated cellulose. Either direct processes for dissolving and forming cellulose using organic solvents or solutions of various cellulose derivatives with possible subsequent saponification to form regenerated cellulose cells are monitored. An example of direct dissolution may be a process that involves mixing chemical pulp with one member of a group of antioxidants of chemical solvents, after which the mixture is passed through a continuous dissolution unit to obtain a clear but viscous solution. This is filtered and spun into an aqueous amine oxide solution which precipitates cellulose in the form of a fiber which is washed and dried. The resulting fiber may be in the form of staple or cable.

The second direction of development follows various derivatives and their processing, suitable for the preparation of shaped cells, respectively. takes the path of modification. The development and processing of cellulose derivatives seems to be more important in terms of fundamentally influencing and eliminating negative environmental impacts.

Of the derivatives suitable for the production of shaped articles, hydroxyalkyl cellulose or a mixture of hydroxyalkyl cellulose and cellulose hydrate (AO 181 830, 182 938) is known. Other derivatives that can be mixed with viscose are aqueous and alkaline sulfonate solutions (JP / A / 146810/86). Prospective derivatives include cellulose carbamate. The product itself is well researched and protected. US 2 132 826 discloses a process for obtaining cellulose carbamate by reacting cellulose with isocyanic acid in a liquid ammonia medium, generally urea and biuret. EP 57 105 describes a process for the preparation of alkali-soluble cellulose derivatives (these are derivatives prepared by reacting cellulose with a solution of urea in liquid ammonia), WO 2278/83 a process for preparing cellulose carbamate for fiber production such that cellulose is irradiated prior to reaction with urea. , 5-10 Mrad. According to CS 254 982, the cellulose to which urea biuret has been added is heated at a temperature above 170 ° C for a time sufficient to produce sufficient isocyanic acid to form cellulose carbamate and to complete the reaction between cellulose and isocyanic acid. CS PV 6730-85 provides a method for precipitating cellulose carbamate, PV 6731-85 or PV

6732-85, in turn, a cyclic process for producing a solution of cellulose carbamate in an alkali (precipitating cellulose carbamate in an alkali solution and recovering with recycling chemicals), PV 4846-88 a method for reducing the carbamate group content of cellulose carbamate products or several alkali metal salts selected from the group consisting of carbonates, sulfates, phosphates, borates and acetates). Another method is known in which the pulp is impregnated with an aqueous solution of hydroxide, alkaline hydroxide and urea in heat (EP 178 292). The cellulose carbamate according to PL 150 106 can be obtained in a different way. The process is based on the cellulose being activated in an aqueous NaOH solution in the presence of an activator such as urea, thiourea, sodium or potassium aluminate for up to 120 minutes. at 18 to 60 ° C, and then the activated cellulose is treated to remove excess NaOH. Such cellulose is then treated with urea, heated to 120-180 ° C for less than 60 minutes. The cellulose carbamate obtained is purified by extraction with alcohol or water. It contains 1 to 8% nitrogen and is soluble in aqueous alkali metal solutions of 3 to 12%.

Cellulose carbamate is a stable product and its solubility in aqueous NaOH solution is advantageous in view of the novel preparation of shaped cells. It is known to date to form shaped cells from cross-linked cellulose aminomethanate (US 4 762 564, EP 283 846). This is crosslinked with a polyhydric crosslinking agent and prepared by reacting the mercerized and pre-hydrolyzed cellulose with urea, then dissolving in a dilute alkali solution and extruding e.g. on a film that coagulates in a bath containing H ₂ SO ₄ and Na ₂ SO ₄ .

SUMMARY OF THE INVENTION

The present invention is based on a process for the preparation of cellulose derivative articles formed by alkaline solutions of cellulose xanthate and carbamate, wherein the mixed solution contains from 1 to 99 wt. % cellulose carbamate is formed by extrusion through a die in an acid coagulation bath. The mixed solution preferably contains 20 to 60 wt. % cellulose carbamate.

A solution of cellulose xanthate in dilute NaOH, i.e., a classical viscose solution, is mixed with an alkaline solution of cellulose carbamate in a predetermined ratio. Another procedure is similar to the classical processing of viscose. The advantage of this process is to reduce the amount of exhalates, such as CS ₂ and H ₂ S, in proportion to the amount of xanthogenate replaced by cellulose carbamate. The physico-mechanical properties of the shaped articles are suitable for further use.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

To the viscose having a composition of 8.2 wt. % of the spinning fraction and 6.1 wt. % NaOH is added a solution of cellulose carbamate with 8.2 wt. % spinning fraction and 6.5 wt. % NaOH in an amount of 5 wt. % by weight of viscose. After mixing and venting, the solution was passed through a 30 micron orifice nozzle into a 45 ° C acid coagulation bath having a composition of 135 g / l H ₂ SO ₄ , 180 g / l Na ₂ SO ₄ and 11 g / l ZnSO ₄ . The resulting infinite cell was then refined in the next process and had the following physico-mechanical properties: air-conditioned strength 17.5 mN / dtex, elongation 16.2%, SN 125% (secondary fiber swelling: air-dry fiber is soaked in the swelling agent (H ₂ O) under precisely defined conditions, is centrifuged after swelling (swelling. From the retained amount of water as the swelling agent, the secondary swelling of the fiber in weight%) is determined. 10

Example 2

The solution of viscose and cellulose carbamate as in Example 1 is mixed in a ratio of 70 wt. % viscose and 30 wt. % cellulose carbamate. This solution was treated by spinning into an acid bath through 2000 holes with a hole size of 60 microns. The obtained fiber had a fineness of 2.65 dtex, the strength in the conditioned state

23 mN / dtex and elongation 15.8%. 20 Example 3 To the viscose composition of 9.0 wt. % spinning and 6.0 wt. % NaOH was added a cellulose carbamate solution with 8.8 wt. % of spinnable fraction and 6.3 wt. % NaOH in an amount of 5 wt. %. The solution was perfectly homogenized, filtered, vented and extruded on the film at operating parameters. The film has a basis weight of 39.2 g / m 2, along its strength 49.3 N / 15 mm and elongation 19.7%, width 28.5 N / 15 mm, elongation 68.6%. The water content was 7.1%. 25 30 Example 4 Cellulose carbamate composition as in Example 3 was added to the viscose in an amount of 90 wt. %. The film obtained by extrusion has a basis weight of 35.5 g / m @ 2, a strength of 43.1 N / 15 mm, an elongation of 19.1%, a width of 23.2 N / 15 mm, an elongation of 58.4%. Water content 6.5%. 35

Industrial usability 40 The process of the invention can be applied to those cellulose derivative molded cell manufacturers who urgently address the ecology of operation in a more prominent manner, such as trapping and purifying exhales. Continuous improvement of this activity in combination with the gradual replacement of viscose from cellulose xanthate with cellulose carbamate solution allows continuous operation. 45 50

PATENT CLAIMS

A process for the preparation of shaped articles from cellulose derivatives, namely alkaline solutions of cellulose xanthate and carbamate, characterized in that a mixed solution containing 1 to 99 wt. % cellulose carbamate is formed by extrusion through a die in an acid coagulation bath. 55 Method for preparing the cellulose derivative shaped articles according to claim 1, characterized in that the mixed solution comprises 60

Claims (1)

PATENT CLAIMS A process for the preparation of shaped articles from cellulose derivatives, namely alkaline solutions of xanthate and cellulose carbamate, characterized in that a mixed solution containing 1 to 99 wt. % cellulose carbamate is formed by extrusion through a die in an acid coagulation bath. 55 Method for preparing the cellulose derivative shaped articles according to claim 1, characterized in that the mixed solution comprises 60 20 to 60 wt. % cellulose carbamate.