RU2338022C2 - Production method of paper base meant for vulcanising or parchmentising - Google Patents

Abstract

FIELD: textile industry, paper industry.

SUBSTANCE: method (version) relates to production of paper base meant for vulcanising and parchmentising and can be used in paper-pulp industry. The method includes the following stages. Energy radiation of cellulose fiber in dry condition. Grinding and refining of irradiate fiber in aqueous media till homogeneous fiber solution is prepared. Formation of web from prepared fibrous suspension, which is dewatered and dried to prepare paper base. According to another version, after paper web forming paper base is exposed to radiation to decrease polymerisation degree of fiber.

EFFECT: development of clean and economically effective process of paper base production for vulcanising and parchmentising as well as decrease of environmental pollution.

26 cl, 4 tbl, 3 ex

Description

The invention relates to a method for manufacturing a paper base for curing or parchment. Thus, it also relates to a base obtained using vulcanization or parchment processes.

Specialists in this field are known processes of vulcanization and parchmentation, therefore, in this application they are not described in more detail. The main thing is that vulcanization is an operation consisting in processing a paper base by immersing it in a solution of zinc chloride, and parchmentation is a similar operation in which zinc chloride is replaced with sulfuric acid. The present invention does not apply to real processes of vulcanization and parchmentation, but relates to a method for the manufacture of paintings that can be processed using these two types of operations.

The ability to process the base using vulcanization or parchmentation processes depends mainly, if not exclusively, on the reactivity of the cellulose fibers that make up the fabric with respect to zinc chloride or sulfuric acid solutions. Thus, the more chemically active, i.e. susceptible to chemical components contained in ionic solutions, cellulose fiber, the more satisfactory are the processes of vulcanization or parchment. The reactivity of the fibrous web depends on several factors, one of which is especially significant - the degree of polymerization (SP) of the cellulose that the fiber is made up of, the latter corresponding to the number of repeating units that make up the cellulose polymer molecule. In general, it seems that the weaker the degree of polymerization, the more reactive the fiber.

In the subsequent part of the application, the effectiveness of the vulcanization or parchmentation processes is controlled by evaluating the degree of protection provided by the paper subjected to vulcanization or parchmentation according to the techniques described in the examples below.

Currently, a number of canvases intended for vulcanization are obtained from textile waste coming mainly from the “jeans industry”, since jeans are 100% made of long-fiber cotton with a staple length of 20-50 mm. In practice, a flap, or rag, from jeans production comes in the form of a bale, which is then loosened and the size of the flap segments is reduced using various operations, for example, cutting and grinding. After completing these steps, the crushed pieces of denim are boiled in a solution of soda with a concentration of 7% in a hermetically sealed reactor under pressure and at a temperature of about 150 ° C. This is followed by the step of washing the digested fiber with water until the cooking liquor is completely removed. Performing all these necessary operations of such an intermittent process can take about 24 hours.

The baking process using soda contributes both to the separation of the cotton fibers and to a decrease in the degree of polymerization of cellulose. In practice, if the average degree of polymerization of the cotton fiber that makes up the denim is about 2000 before digestion, since the fiber is intended for vulcanization or parchmentation, immediately after the digestion step, the degree of polymerization is only 600. It is believed that the value 600 is actually sufficient to achieve reactivity and, therefore, satisfactory ability of the base paper to cure or parchment.

The bundles of digested fiber are treated in an aqueous medium to separate the fibers, after which the individual fibers are refined, i.e. their structure is subjected to deformation by mechanical action, providing optimization of the susceptibility of the fiber. The suspension containing the disengaged cotton fibers obtained immediately after these steps is then injected onto the mesh conveyor of the paper machine in the presence or absence of fibers of a different or the same nature, for example wood fibers, to form a web in a known manner, which is then dehydrated and dried to obtain the finished paper base.

As mentioned above, it is necessary, prior to vulcanization or parchmentation, to distribute the most reactive cellulose fiber in the paper, and this reactivity is obtained by greatly reducing the degree of polymerization of the cellulose fibers.

The digestion step by which these results are obtained, however, has some disadvantages. First, the capital investment in installing an industrial reactor is relatively high. In addition, a large amount of chemicals, in this case, soda, is consumed during the digestion process. And, finally, above all else, digestion leads to the formation of colored filtrates of concentrated soda, whose pH is 13.5 and the removal of which is especially difficult, and they cause environmental pollution. The yield after digestion and washing of the flap is usually about 85%, which means a loss of feedstock of about 15%.

In other words, the invention aims to solve the problem by creating a clean and cost-effective (product yield above 85%) method of manufacturing a paper base intended for vulcanization or parchmentation, which would be at least as reactive with respect to zinc chloride or sulfuric acid solutions as well as the bases obtained by methods that use the stage of chemical digestion of cellulose fiber having a high degree of polymerization.

In this connection, the applicant had the idea to replace the stage of digestion in a concentrated soda solution with the stage of energy irradiation, and this stage of irradiation can be carried out either by acting on the cellulose fiber in a dry state immediately before the fiber is separated and refined in an aqueous medium, or by acting on the finished paper dry condition.

In other words, in a first embodiment, the invention relates to a method for manufacturing a paper base for curing or parchment, comprising the following steps:

- irradiation with energy of cellulose fiber in a dry state;

- separation and refining in an aqueous medium of the irradiated fiber to obtain a homogeneous fibrous dispersion;

- forming the web from the obtained fibrous suspension, which is then dehydrated and dried to obtain a finished paper base.

The expression "homogeneous fiber suspension" means a suspension in which the cellulosic fiber is dispersed in an aqueous solution to a dryness of about 1-10 wt.%. The suspension is called homogeneous, since the fibers were correctly separated due to hydration and mechanical mixing effects, thus eliminating the formation of fiber complexes.

In other words, the method consists, first of all, in lowering the degree of polymerization of the cellulose fiber by irradiating it with energy in a dry state, and after reaching a degree of polymerization at which the reactivity of the fiber is sufficient, the fiber is separated in an aqueous medium and refined; in the inlet of the fibrous suspension onto the mesh conveyor of a paper machine for forming the web, which is then dehydrated and dried.

In another embodiment of the invention, the cellulosic fiber is not irradiated with energy before the web is molded, and after it is molded, the finished paper substrate for vulcanization or parchment is directly irradiated.

In this case, the method includes the following steps:

- separation and refining in an aqueous medium of the cellulose fiber contained in the mixture of fibers to obtain a homogeneous fibrous suspension;

- forming the web from said suspension, which is then dehydrated and dried to obtain a finished paper base;

- and, finally, irradiation with energy of the paper base.

In the rest of the description and in the claims, the expression "cellulose fiber" means a fiber formed by processing cellulose, for example cotton fiber or any other fibers of annual plants (flax, manila hemp), wood fiber, and these fibers of different origin differ from each other in structural characteristics, for example, the shape, cross-section, wall thickness and the average degree of polymerization (SP) of the cellulose from which they consist.

In an embodiment according to which the energy is irradiated to produce a sheet, a cellulosic fiber of the same origin, whether or not irradiated with energy, and / or a cellulose fiber of another origin, subjected to or not exposed to energy, and / or synthetic, and / or mineral non-cellulose fiber.

The substantially cellulosic fiber irradiated with energy is preferably annual plant fiber, and especially cotton fiber, and it comprises at least 20 wt.%, And preferably at least 50 wt.%, Of the fibrous suspension.

In the embodiment according to which the paper base is irradiated directly, all the cellulosic fibers contained in the paper are irradiated with electron beams, regardless of their origin. It is understood that the fiber blend may further comprise cellulosic fiber, synthetic and / or mineral non-cellulosic fibers. In practice, cellulosic fibers comprise at least 20 wt.%, Preferably at least 50 wt.%, And most preferably 100 wt.% Of the fibrous composition. In a preferred embodiment, the cellulosic fiber consists solely of cotton fiber.

If the paper base contains cotton fiber as cellulosic fiber, then cotton fiber may come from two significant sources.

First of all, the cotton fiber can be primary cotton fiber, preferably long-fiber, with a staple length of 20-50 mm. In practice, the cotton manufacturer receives the cotton fiber in a dry state, either in the form of sheets or in the form of a compressed pulp, thus containing 100% cotton fiber.

In this case, irradiation with energy is carried out by irradiation with an electron beam or x-ray radiation.

If irradiation is carried out before sheet formation and using x-ray radiation, then the penetration of radiation is sufficient for direct processing of the cotton mass in a bale of 1 m ³ .

If irradiation is carried out before sheet formation and by means of an electron beam, then the sheet or compressed paper pulp is defibrated in the dry state (before the irradiation stage), and these operations are performed so that the material passed under the beam has a low surface flux density (< 0.6) and a small thickness of the stream (of the order of one centimeter) so that the cotton fiber can be processed evenly and efficiently.

As mentioned above, paper substrates intended for vulcanization or parchmentation can also be advantageously obtained from cotton fiber coming in the form of textile waste. In a preferred embodiment, the cotton fiber introduced into the fiber suspension comes from the jeans industry. In this case, the raw materials are denim flaps pressed into bales.

In practice, the pile is first loosened, the jeans flap is cut, possibly sorted to remove foreign objects, for example, metal elements, and then crushed.

If the paper base is produced in a continuous mode, then the cellulosic fiber obtained after grinding is separated and refined in an aqueous medium.

If the paper base is produced in an intermittent mode, then the fiber obtained by grinding, again stored in the form of bales, which are then loosened, the cellulose fiber is separated and finally refined in an aqueous medium.

In the first embodiment, if the irradiation is irradiation with electron beams, and it is carried out before forming a paper sheet, then irradiation can be performed either immediately after the cutting step and before the grinding step, or immediately after the grinding step.

In the second embodiment, the radiation is x-ray radiation, which is applied directly to the bale containing a cut and chopped flap of jeans material.

As mentioned above, the reactivity of cellulose fiber depends on its degree of polymerization (SP).

The applicant has found that in order to obtain cotton fiber treated with energy irradiation, which would become as reactive as fiber processed by digestion, it is necessary to lower the degree of polymerization below the level of the same parameter of the digested fiber.

In addition, as has already been said, it is known that the degree of reactivity of cotton fiber does not have to be at the same level, whether it is intended for vulcanization or parchment.

In addition, the applicant noted that in order to achieve the same level of reactivity, the degree of polymerization of the cellulose fiber, which absorbed the given radiation dose before sheet formation, was higher than the degree of polymerization of the same fiber, which absorbed the same radiation dose in the finished paper.

A case in which a cotton fiber is irradiated with energy (electron beam or x-ray radiation) before sheet formation.

If the degree of polymerization of the digested fiber intended for vulcanization is about 600, then in order to achieve a reactivity of at least equal to the reactivity of the same fiber subjected to energy irradiation, it is necessary to reduce the degree of polymerization to between 350-500, preferably 450. To achieve such values of the degree of polymerization, the dose of radiation absorbed by the cotton fiber should be in the range of 10-30 kGy.

The degree of polymerization of the digested processed cellulose fiber for parchmentation is about 1000. To achieve a reactivity with concentrated sulfuric acid of at least equal to the reactivity of the same fiber irradiated with energy, it is necessary to lower this degree of polymerization to 700 so that the dose of radiation absorbed by the fiber is in the range of 5-20 kGy.

Typically, the dose of radiation absorbed by the cellulose fiber, necessary to obtain the optimum reactivity of the substrate with respect to vulcanization and parchmentation, depends on the processing conditions and, in particular, on the type of equipment used.

The case in which cotton fiber is irradiated after sheet formation

If a paper sheet made only of cotton fiber is intended for vulcanization, the degree of polymerization of the fiber of which the resulting paper sheet is less than 700, preferably in the range of 200-300, more preferably 250. The applicant noted that to achieve this the dose of radiation absorbed by the cotton fiber should be in the range of 10-50 kGy. However, these values may be applicable only in the case of vulcanization.

In the case of parchment, if the paper is made only of cotton fiber, the degree of polymerization of the fiber of which the resulting paper sheet is comprised is in the range of 400-600, and preferably 500. The applicant noted that in order to achieve such a value, the radiation dose absorbed by the cotton fiber should be in the range of 5-30 kGy.

A method of manufacturing a paper base according to the invention, depending on whether the irradiation is performed with energy before or after forming the sheet, can be carried out continuously or intermittently.

The invention and its advantages obtained by its use, will become more clear when reading the following examples of implementation of the invention.

Example 1

In this example, the method is performed intermittently, and it consists of cutting textile waste, removing foreign objects and grinding the flap to form a bale. This sequence of steps is carried out continuously using appropriate cutting, sorting and grinding machines known to those skilled in the art.

The bale packaging step facilitates the storage of raw material prepared for use until the subsequent step of dispersing the fiber in an aqueous medium.

When the papermaker re-takes the bale of jeans waste, he breaks it in a dry state so that the bale is loosened. The flap of jeans material is then separated, defibrated, and then refined in an aqueous medium; the resulting fibrous suspension is then fed to a paper machine, on which, after dehydration and drying, the finished paper is obtained.

In the known methods, the obtained crushed pieces of denim after loosening the bales in a dry state are subjected to the stage of digestion in a digester at a temperature of about 150 ° C in soda solutions with a concentration of up to 7%; then the resulting mass is washed and defibrated and finally refined in an aqueous medium.

In an exemplary embodiment of the method according to the present invention, these stages of digestion and washing are replaced by the step of irradiation with electron beams.

This irradiation step can be performed by treating the cotton fiber before making paper, and it can be performed either immediately after the storage step, or immediately after the grinding step, or directly on the finished sheet.

Example 2

In this example, the paper to be vulcanized is made entirely from 100% cotton fiber, processed either by digestion or by irradiation before forming the sheet.

A) Method

For two samples, the degree of polymerization of the boiled cotton fiber and the fiber subjected to electron beam irradiation was determined before the paper was transformed by vulcanization, as well as the reactivity of the finished sheet after vulcanization. The degree of polymerization of the cotton fiber was determined by calculating the measured viscosity of a solution based on cupriethylenediamine (CED) in which cellulose fiber was dissolved.

Tests, the results of which determined the degree of polymerization, were performed as follows:

- put the fiber in a polyethylene container containing 10 ml of deionized water, with stirring;

- then 10 ml of cupriethylenediamine was added;

- air was removed from the tank, compressing its walls;

- closed the container with a stopper;

- mixed the solution for 40 minutes until the fibers were completely dissolved;

- filtered the solution using a mechanical filter;

- measured the viscosity of the lower part of the filtrate using a capillary viscometer CANON-FENSKE 200.

The reactivity of paper (DL) was evaluated after vulcanization by measuring the level of protection using a colored solvent. The tests were performed as follows:

- prepared a sample of paper for testing size 10 × 10 cm;

- laid on one side a sample of test paper on carbon paper;

- applied a colored solution of terpentine on the entire surface of the paper to be tested; contact time was 3 minutes.

Estimates are given in table 1:

Table 1 Rating Test paper side Copy paper 5 Lack of spots Lack of spots four 4 spots maximum Lack of spots 3 Few spots Lack of spots 2 - 4 spots maximum one - Few spots 0 - 1-2 spots measuring 5-20 mm -one - More than 2 spots of size 5-20 mm -2 - Spot size greater than 200 mm -3 - The whole surface is painted

Typically, the higher the DL value of the cured conversion paper, the higher the reactivity of the base paper. The reactivity of the paper was then determined by the level of protective ability of the resulting finished product.

C) Measurement results

1) The SP and DL indicators for fiber irradiated with various doses of absorbed energy before sheet formation are shown in the following table 2.

table 2 Dose, kGy Surface density, g / m ² The degree of polymerization (SP) DL 0 111 2010 0 10 109 640 one fifteen 109 525 2 twenty 107 515 2 25 112 370 2 thirty 110 390 3 fifty 110 330 3

It can be seen from the results that in order to achieve the degree of reactivity of paper treated with irradiation of the same level as paper obtained from the digested fiber (DL = 3), it is necessary to reduce the degree of polymerization of the treated fiber to a value of about 390.

2) The values of the degree of polymerization and DL of paper whose cotton fiber was boiled or processed by an electron beam are shown in the following table 3, but it should be remembered that the degree of polymerization was estimated from the fiber before the paper was transformed by vulcanization.

Table 3 Degree of polymerization DL 1 Boiled cotton fiber 600 3 2 Irradiated paper, dose 50 kGy 250 3 3 Irradiated fiber, dose 30 kGy 390 3

Examples 2 and 3 of the table show the difference that occurs when the raw material is irradiated before the paper is made, compared with the irradiation of the finished paper. To achieve the same level of paper conversion after vulcanization, i.e., it can be said to achieve the same level of paper reactivity, a much larger radiation dose had to be reported to the finished paper than to the raw material.

Example 3

In this example, the paper that was supposed to be parchment was made entirely from 100% cotton fiber, treated by irradiation before forming the sheet.

A) Method

The samples were characterized by the degree of polymerization of the cotton fiber subjected to electron beam irradiation before the parchment paper conversion operation, as well as the reactivity of the sheet with respect to parchment.

The degree of polymerization (CP) of the cotton fiber was determined by calculating the measured viscosity of a solution based on cupriethylenediamine (CED) in which cellulose fiber was dissolved.

The reactivity of paper (DL) was evaluated after parchmentation by measuring the protective level using a colored solvent.

C) Measurement results.

Table 4 Dose, kGy Degree of polymerization DL 0 2010 one 10 640 5 thirty 400 5 fifty 320 5

As can be seen, when irradiating cotton fiber with electrons prior to paper manufacture, a dose of 10 kGy is sufficient to lower the degree of polymerization of cellulose below 700, which makes it capable of a good level of parchment.

Claims (27)

1. A method of manufacturing a paper base intended for vulcanization or parchment, comprising the following steps: dry cellulose fiber energy irradiation; separation and refining of the irradiated fiber in an aqueous medium to obtain a homogeneous fibrous suspension; forming the web from the obtained fibrous suspension, which is then dehydrated and dried to obtain a finished paper base. 2. The method according to claim 1, in which a cellulose fiber of the same origin, whether or not irradiated with energy, and / or a cellulose fiber of another origin, whether or not exposed to energy, and / or is added to a fiber suspension subjected to energy irradiation, and / or synthetic and / or mineral non-cellulose fiber. 3. The method according to claim 1, in which the fibrous suspension contains at least 20 wt.%, And preferably at least 50 wt.% Of the cellulose fiber subjected to energy irradiation. 4. The method according to claim 1, in which the cellulose fiber subjected to irradiation with energy, is a cotton fiber. 5. The method according to claim 4, in which the cotton fiber subjected to irradiation with energy, is the primary cotton fiber coming in the form of sheets or compressed paper pulp. 6. The method according to claim 5, in which the irradiation with energy is irradiation with electron beams or x-rays. 7. The method according to claim 4, in which the cotton fiber subjected to energy irradiation is a waste of the textile industry. 8. The method according to claim 7, in which the cotton fiber is a waste of jeans material, first subjected to cutting, then sorting and grinding, and the fiber is irradiated with electron beams either immediately after the cutting step and before the grinding step, or immediately after the grinding step. 9. The method according to claim 7, in which the cotton fiber is a waste of denim material in the form of bales containing a denim flap, possibly chopped and then ground, the entire bale being subjected to x-ray irradiation. 10. The method according to claim 4, in which if the paper is supposed to vulcanize, then the dose of radiation absorbed by the cotton fiber is in the range of 10-30 kGy. 11. The method according to claim 4, in which if the paper is supposed to vulcanize, then the degree of polymerization of the irradiated cotton fiber is in the range of 350-500. 12. The method according to claim 4, in which if the paper is supposed to be parchment, then the dose of radiation absorbed by the cotton fiber is in the range of 5-20 kGy. 13. The method according to claim 4, in which if the paper is supposed to be parchment, then the degree of polymerization of the irradiated cotton fiber is 700. 14. A method of manufacturing paper that is supposed to vulcanize or parchment includes the following steps: separation and refining in an aqueous medium of the cellulosic fiber contained in the mixture of fibers to obtain a homogeneous fibrous suspension; forming the canvas from a suspension, which is then dehydrated and dried to obtain a finished paper base; reducing the degree of polymerization of the fiber by irradiating the energy of the paper base 15. The method according to 14, in which the fiber mixture contains at least 20 wt.%, Preferably at least 50 wt.%, And most preferably 100 wt.% Cellulose fiber. 16. The method according to 14, in which the cellulose fiber is a completely primary cotton fiber coming in sheets or compressed into a bale. 17. The method according to 14, in which the cotton fiber, defibrated and then refined in an aqueous medium, comes in the form of textile waste. 18. The method according to 17, in which the textile waste comes from the "jeans industry". 19. The method according to 14, in which the fibrous suspension contains 100 wt.% Cotton fiber. 20. The method according to 14, in which the irradiation is carried out by electron beams. 21. The method according to claim 19, in which if the paper is supposed to vulcanize, then the dose of radiation absorbed by the cotton fiber is in the range of 10-50 kGy. 22. The method according to claim 19, in which if the paper is supposed to vulcanize, then the degree of polymerization of the irradiated cotton fiber is less than 700, and preferably in the range of 200-300. 23. The method according to claim 19, in which if the paper is supposed to be parchment, the polymerization degree of the irradiated cotton fiber of which the resulting paper sheet consists is in the range of 400-600, and preferably 500. 24. The method according to claim 19, in which if the paper is supposed to be parchment, then the dose of radiation absorbed by the cotton fiber is in the range of 5-30 kGy. 25. The use of paper obtained by the method according to any one of claims 1 to 11, for vulcanization. 26 The use of paper obtained by the method according to any one of paragraphs.14-22, for vulcanization. 27. The use of paper obtained by the method according to any one of claims 1 to 9, 12, 13, for parchment. 28. The use of paper obtained by the method according to any one of paragraphs.14-20 or 23-24, for parchment