DE1151494B - Process for the production of a viscose which is preferably suitable for film production - Google Patents

Description

It is known to convert solutions of cellulose xanthate, namely viscose, into films of regenerated cellulose to process. In this process, a film is cast from the viscose with the help of a film caster, which then coagulates, regenerates, washed, desulfurizes in appropriate treatment baths, is bleached, glycerinized and dried. It is used as the starting product for the production of viscose natural CeEulose in question, such as those made from wood pulp, cotton linters, ramie, hemp, or flax Sugar cane residues can be obtained.

In the individual work steps for the production of the viscose, however, you have to use the cellulose Subject to the ripening process in order to break down the cellulose molecule To such an extent ensure that a viscose solution with one for casting and spinning purposes suitable viscosity is present. For this purpose one has already in the context of the first work steps the alkali cellulose by treatment with atmospheric oxygen or chemical oxidizing agents Subject to maturation process. However, this procedure takes a lot of time and, above all, has been very difficult ensure even molecular breakdown, especially when in the presence of catalysts was worked on the basis of cobalt and manganese. In general one then obtains matured alkali cellulose with widely varying molecular weights.

This is where the invention comes in. According to the new procedure the molecular degradation of the cellulose can take place during each work step. Special advantages lie in the continuous production of the viscose, because an interruption at some point in the Manufacturing process is unnecessary.

The method of the invention relates to manufacturing of viscose by alkalizing cellulose, sulfiding the alkali cellulose with carbon disulfide, Dissolving the cellulose xanthate in alkali and filtering the viscose and is thereby characterized in that cellulose, alkali cellulose, cellulose xanthate and or or the viscose of ionizing radiation of 0.05 to 60, especially 10 to 30 watt seconds each Exposing grams of cellulose.

The term watt seconds is used to describe the radiation power, i.e. the total energy emitted in the unit of time expressed. This is the product of activity (with the unit Curie) and the radiation energy a source (MeV), i.e. MeV times Curie. One watt second equals 169 MeVCurie each Second.

Under ionizing radiation is in the sense of the invention process for production

one preferably for film making

suitable viscose

Applicant:

EI du Pont de Nemours and Company,
Wilmington, Del. (V. St. A.)

Representative: Dr.-Ing. A. v. Kreisler,

Dr.-Ing. K. Schönwald and Dr.-Ing. Th. Meyer,

Patent attorneys, Cologne 1, Deichmannhaus

Claimed priority:
V. St. v. America 2 January 1957 (No. 632 007)

Bruce Emerson Englund, Richmond, Va.,

and John Willard Jones, Wilmington, Del. (V. St. A.) have been named as inventors

dung nuclear radiation in the form of highly accelerated components of matter as well as radiation based to understand electromagnetic waves. As particle radiation is an emission of accelerated Electrons or from core components such as protons, neutrons, α-rays, or deuterons / 5-rays, which then point to the to be irradiated Hit cellulose. Known arrangements, such as cathode ray tubes, cavity resonance accelerators, Van de Graaff accelerators, betatrones, synchrotrons or cyclotrons, are used for Acceleration of the chosen particle. One works with beams of more than 0.1 MeV. Neutron radiation can be made more suitable by irradiation, for example consisting of beryllium Create light metal plates with positive particles of high energy. Particle radiation can also with the help of a nuclear reactor, with the help of radioactive isotopes or other natural or artificial Achieve radioactive substances.

Ionizing electromagnetic radiation within the meaning of the invention is produced by bombarding Metal plates, for example made of tungsten, with electrons of the appropriate energy. One then speaks of X-rays. These are short-wave and have a spectral distribution in the area of longer waves.

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treatment, the energy of which is determined by the plate material and the voltage applied. Ionizing electromagnetic radiation can also be reduced by switching on a nuclear reactor or under Application of natural or man-made radioactive materials, such as cobalt 60, generate, with then Gamma radiation arises, which differs from the X-ray radiation only by its origin and its spectra distribution differs. Gamma rays are in contrast to those produced by electron bombardment Panels produced X-rays essentially monochromatically.

The same physical characteristics apply to the energy of the irradiated ionizing radiation, even if different types of radiation, such as particle radiation or electromagnetic Radiation. For the method of the invention, irradiation with at least 0.000005 MeV required, preferably 0.000005 to 0.003 MeV or even up to ao 0.1 MeV. A particularly strong penetrating radiation, as is the case with continuous operation of The advantage is that it even requires radiation energies of 0.1 to 5 MeV. For the level of radiant energy are the cost of radiation generation and the desired penetration are decisive. Notes on the relationship between penetration and the level of radiant energy are given in the tables of L. E. Glenndenin reproduced (see "Nucleonics", Vol. 2, No. 1, p. 21, 1948).

It depends on the particularities of the viscose production process in which work step the irradiation is carried out shall be. The type of starting cellulose is important here, and it depends on whether wood pulp is supplied in the form of sheets or shredded flakes or whether cotton linters should be processed.

With most commonly used radiation devices, especially with Van-de-Graaff accelerators, the for the desired Cellulose degradation required irradiation dose easily by hand or automatically agitated, wherein the radiation intensity and / or the throughput rate of the cellulose material is set will.

The depolymerization can take place in the range between room temperature and dry ice temperature. If cellulose sheets are irradiated, it is with a view to the influence of moisture on the degradation It is important to ensure that the radiation effect has a low moisture content. For liquid-moist alkali cellulose the radiation effect is essentially independent of the moisture content. She corresponds here in all cases about 85% of that for air-dry ones Wood pulp measured value.

No oxygen is required for the ripening of the cellulose, achieved by irradiation, and the depolymerization is in the presence of air of the electron energy and dosage essentially addicted. In the production of viscose, wood-cement is used in the form of continuous webs from a roll unwound and introduced into the process, the irradiation can be carried out immediately when unwinding from the Role.

Alkali cellulose can be in a compressed and in a fiberized state or as a pulp suspended in lye be irradiated while taking the cellulose xanthate irradiated itself or its suspension in alkali. Finally, the ripening process can can also be brought about by irradiating the viscose. According to a special embodiment, irradiation takes place during several operations, for example by briefly irradiating wood cellulose or alkali cellulose with additional irradiation the viscose.

In detail, the following embodiments have proven themselves for the method of the invention:

A. When irradiating wood cellulose

or cotton linters

1. The cellulose is passed through the irradiation chamber while being unwound from a roller and then slurried or continuously with guide rollers through the liquid guided or shredded in chopping machines. You can then also use the irradiated, frayed one Filling and storing cellulose before further processing into viscose or by rewinding Produce cellulose bales if the further processing into viscose is not immediate he follows.

2. Wood or cotton cellulose can be guided through the irradiation chamber as plates on conveyor belts and, as indicated under A, 1, be treated further. ·

3. Wood or cotton cellulose are used as cutlets, leaves or in a pulpy state the irradiation chamber and, as indicated under A, 1, either stored or immediately further processed.

B. When irradiating alkali cellulose

1. Pressed flakes of alkali cellulose are continuous with the help of a conveyor belt behind the working press passed through the irradiation chamber. Then it is xanthated.

2. A slurry of alkali cellulose is passed through the irradiation chamber, then pressed and xanthogenized or immediately xanthogenized as sludge without pressing.

C. When the CeUulxanthogenate is irradiated

The xanthate is passed through the irradiation chamber.

D. When irradiating the viscose

The viscose is passed through the irradiation chamber.

The desired degree of depolymerization is checked by measuring the 1% CED viscosity according to the method of TAPPI, method T 230 Sm-50, F. L. Strauss and R. M. Levy, Paper Trade Journal, Vol. 114, No. 3, pp. 31-34, January 15, 1942.

By irradiating wood cellulose or alkali cellulose in the range from 0.05 to 60 watt seconds per gram of cellulose, products with a 1% CED viscosity of 5 to 12 are obtained. Than 1% -CÄD viscosities which viscosities of a l ^e / o dispersion of the substance in cupric ethylene diamine apply. The viscosity values must be measured after diving in order to ensure that they are measured with diving

to eliminate the associated slight drop in the 1 ° / o-CÄD viscosity.

The following examples illustrate the invention. All quantities are, as far as nothing otherwise stated, to be regarded as amounts by weight.

example 1

A sample of bleached sulfite wood pulp from Brown DurNatus was sent for irradiation passed a 2 MeV Van de Graaff accelerator operating at 250 microamps. Scanning width of the beam: 20 cm; Window to sample distance: 10 cm; Passage speed: 2 cm / second.

In this and all subsequent examples, the thickness of the samples was adjusted to 1 watt-second per square centimeter corresponded to a watt-second per gram. Corresponded in the same way 10 watt seconds then 1 megarad.

In the present case, the irradiation was 12.5 watt seconds per square centimeter. The sample was then at 30 ° C for about 30 minutes in an 18% Immersed in NaOH solution. It was then pressed to a compression weight ratio of 2.7 (2.7 parts of Pressings thus contained 1 part of dry matter) and defibrated at 25 ° C for about 25 minutes to 55 minutes.

During the dipping process and the defibering process, the degree of depolymerization was checked Several samples were taken at certain time intervals with a 20% acetic acid solution were neutralized. The samples were then washed, dried and their CAD viscosities checked determined by the Tappi method mentioned above (see table).

Radiation dose:
12.5 watt-seconds-per square centimeter

IO

30th

35

Time
in minutes lo / o-CÄD-
viscosity Dive time I 0
10
20th
30th
55
85 6.6
6.4
6.2
5.8
6.3 Time of fiberization \

40

45

Good films made of regenerated cellulose can be produced within a viscosity range from 6.5 to 7.5 produce. At the end of the defibering, the samples were xanthogenized immediately without further ripening and then converted into viscose and filtered. One from this viscose in a known manner The physical behavior of the film produced fully corresponded to that of the usual ones Manufacturing process obtained films from regenerated cellulose. In the known manufacturing processes however, treatment times of 8 to 40 or more hours must be required for the viscose maturation the defibration must be accepted.

Example 2

Bleached sulfite wood pulp from Brown DurNatus was, as described in Example 1, with Irradiated electrons. Radiation dose: 12.5 watt-seconds per square centimeter. The irradiated product was immersed in an 18.0% NaOH solution at 30 ° C. for 30 minutes, then the obtained alkali cellulose pressed to a compression weight ratio of 2.7, for 30 minutes at 30.degree fiberized and immediately afterwards xanthated for 90 minutes at 28 ° C. After 90 minutes After long mixing, the viscose was filtered at a viscosity of 73 poises at 14 ° C. After this A sample was taken from the defibering operation and found to have a 1% CED viscosity of 6.78. A completely clear viscose was obtained which could be cast into perfect films.

Example 3

A bleached sulfite Hokcellulose from Brown DurNatus was 30 minutes at 30 ° C in immersed in a 18.0% NaOH solution. The accruing Alkali cellulose was pressed to a press weight ratio of 2.86, 45 minutes at 30 ° C frayed and immediately xanthated for 60 minutes. After a mixing time of 45 minutes, the viscose had a viscosity of 357 poises at 22 ° C.

A sample of the viscose produced in this way was, as described in Example 1, a Subjected to electron irradiation. Dose: 3.79 watt seconds per gram of cellulose. The irradiated Viscose had a viscosity of 68 poises at 22 ° C. It was of excellent clarity and left process themselves into completely flawless films.

Good regenerated cellulose films can be made from viscose with viscosities within the range of 15 to 145 poises can be obtained at 18 ° C. However, it is preferable to process viscose with viscosities between 45 and 80 poises at 18 ° C.

Example 4

The bleached sulfite wood cellulose from Brown DurNatus according to Example 3 was 30 minutes immersed in a 18.0% NaOH solution at 30 ° C. The resulting alkali cellulose was reduced to a press weight ratio pressed from 2.86, defibrated at 30 ° C for 45 minutes, air-dried for 19 hours and xanthated for 60 minutes. After 15 minutes of thorough mixing, the viscose had a viscosity of 87 poises at 22 ° C. A sample of the viscose produced in this way was after Example 1 irradiated with electrons at a dose of 0.8 watt seconds per gram of cellulose. The irradiated Viscose had a viscosity of 53 poises at 22 ° C. It showed excellent clarity and allowed himself to be poured into impeccable films, whose physical behavior resembles the well-known The films produced by the method were completely equivalent.

The method of the invention combines a number of technical advantages on other, for the purpose Degradation of the cellulose molecule during the production of viscose known in its entirety could not be reached. It is of the greatest value here that the new process only takes depolymerization times of a few seconds or even less, the degradation of the molecules being completely unsystematic and is done arbitrarily so that the desired uniform molecular weight distribution in is achieved to a high degree. It is also very important that the average degree of depolymerization is accurate can be adjusted by adjusting the radiated energy accordingly.

None of the in

ripening processes known in the art. Depolymerization with atmospheric oxygen in the presence of Cobalt catalysts can be reached relatively quickly, but are difficult to monitor. The chemical breakdown of the alkali cellulose by treatment with hydrogen peroxide is rapid and is also easy to adjust, but due to its topochemical nature leads to products with more non-uniform Molecular weight distribution. The acid-catalyzed hydrolytic depolymerization of cellulose, as it comes into question, for example, in the production of wood pulp, can be controlled quickly and easily perform, but gives insufficient yields. This procedure is undesirable also working with low-solids sludge, which results in high operating and system costs. One lets as the cellulose ripens under treatment with air, products of fairly uniform molecular weight distribution become products obtain. This working method is also easy to monitor, but a treatment time of up to 60 hours is a heavy burden represent.

Further technical advances in the new process are that as a result of the great rapidity ongoing irradiation process no intermediate stacking to carry out the Maturation process is necessary. With the uniform molecular breakdown achieved, only small amounts fall of cellulose with very low molecular weights, so that a high pulp yield is achieved and only small amounts of waste product have to be discharged. Since there is no catalytic work, is in the event of malfunctions, the risk of undesirable and not overlooked subsequent ripening is eliminated. One There is no need for careful temperature control, since the irradiation process is essentially temperature-independent runs. The energy to be radiated and the viscosity of the viscose can be automatically coupled and in this way obtain a particularly uniform product, which is particularly suitable for processing the viscose is important to rayon or regenerated cellulose films.

The process of the invention can, in modified form, be applied to all types of viscose production transfer.

Claims (1)

PATENT CLAIM: Process for the production of viscose by alkalizing cellulose, sulfiding the alkali cellulose with carbon disulfide, dissolving the cellulose xanthate in alkali and filtering the viscose, characterized in that the cellulose, the alkali cellulose, the cellulose xanthate and / or the viscose an ionizing radiation of 0 .05 to 60, in particular 10 to 30 watt seconds per gram of cellulose. Considered publications:
German patent specification No. 834267. © 309 647/281 7.