JPH07310221A - Bum fiber gum removal - Google Patents

Abstract

PURPOSE: To obtain a bast fiber excellent in tearing strength, breaking strength and swelling characteristics, and suitable for a rope, seal, etc., by adding an aqueous alkali solution to a bast fiber of a striped bark under a reduced pressure, effecting under a reduced pressure for removing a gum from the above bast fiber efficiently. CONSTITUTION: This method for removing a gum from a bast fiber is to add an aqueous alkali solution such as an alkali metal hydroxide or carbonate (concentration of preferably 1-5 N) under <=200 mmHg reduced pressure to a bast fiber of a striped bark such as a ramie, hemp, flux, etc., and effect under a reduced pressure, atmospheric pressure or under a pressure at 80-150 deg.C temperature for removing a gum from the above bast fiber. Further, a liquid ratio of the above bast fiber/aqueous alkali solution is preferably in a range of (1/0.8)-(1/2), and also it is preferable to have >=2.8% braking elongation, >=2.7 mean swelling factor and <=0.2 standard deviation of swelling factor along the fiber of the obtained bast fiber.

Description

Detailed Description of the Invention

[0001]

The present invention relates to ramie, flax, cannabis,
It relates to an improved method for the chemical degumming of debarked bast fibers such as Manila hemp, jute, kenaf, sisal and the like, and to bast fibers with improved tear strength and improved swelling properties obtained by this method.

[0002]

BACKGROUND OF THE INVENTION As is well known, cellulosic fibers obtained from ramie plants have been used in West Asia for thousands of years and were introduced to Europe around the mid-19th century.
It is especially distinguished by its surprising tensile strength, low elongation, high wet strength and high resistance to decay when compared to other fibers.

Therefore, ramie fibers are outstandingly suitable for the production of ropes, seals and the like. Especially for industrial materials (eg industrial belt reinforcements, building reinforcements), papermaking, household textiles and garments, to optimize the smoothness, texture, luster, comfortability, etc. The fibers are often mixed with other natural or synthetic fibers.

In the first manufacturing step, the leaves of the ramie plant are dropped and the bark is peeled off.

The well-known method of bark stripping is followed by a thorough degumming and submersion step to remove lignin and to remove glue on plants that still have cellulosic fibers adhered to the bark stripped stem material. Be seen. This issue has not been fully resolved.

According to current methods, the fibers in the stem are first exposed by stripping the bark. Attempting substantial gum dissolution with pressure and water during bark stripping has proven to be less economical in practice. Therefore,
Generally, the degumming method must be performed after the bark has been peeled off.

Known gum removal methods are based on the biological and / or chemical degradation of gums.

In the well-known chemical method, the gum is prepared by the following methods: a) At atmospheric pressure, the fiber bundles are hung in a cooking tank or spread on a net; b) Under pressure, the gum removal is accelerated. C) removal of the gum under pressure, followed by a rapid drop in pressure to atmospheric pressure, which further facilitates the separation of the individual fibers and the gum;

More recent biological methods are based on enzymatic or bacterial degradation. However, the cost of enzymatic degradation is considerable. On the other hand, bacterial degradation requires ensuring that a constant pH is maintained in order to maintain the desired bacterial population and thus avoid fiber damage as much as possible. However, even when using well-selected bacterial strains, it has been found that bacterial strains tend to mutate and impair the cellulose content of the fiber.

Therefore, the most commonly used gum removal method is based on the chemical decomposition of plant gums by heating in an aqueous solution of a strong base. In addition to inorganic bases, organic bases such as C
Sodium, potassium and tetramethylammonium salts of _{6- C18} fatty acids and their fatty acids and primary
Salts with secondary, secondary or tertiary amines are also proposed. However, inorganic bases, especially sodium hydroxide,
Potassium hydroxide, sodium carbonate or potassium carbonate are usually used.

Degumming is typically carried out by boiling the bark of the bark of the bark several times in an alkaline medium at atmospheric pressure or under pressure at about 100 ° C. or higher. Usually, detergents, dispersants, sequestering substances and / or substances having a reducing action are also added to the alkaline medium. The liquid ratio of debarked ramie / gum removal solution is about 1: 8 to 1: 2.
0, the processing time is generally up to 12 hours per batch, ie the known chemical degumming methods result in a relatively high consumption of water, chemicals and energy (in the form of heat supply), thus they are The environment is inconvenient and expensive.

The content of unseparated fibers in the degummed ramie fibers by these methods is 1 to 5%. Thus, if the plant is substantially devoid of glue, the fibers will remain unstable and fragile, thus reducing availability. If one attempts to reduce the gum balance by repeated boiling in alkaline solution, on the contrary, the risk of unwanted fiber damage due to cellulolysis is increased.

[0013]

SUMMARY OF THE INVENTION The present invention is an improved process for the chemical degumming of debark bast fibers such as ramie, flax, cannabis, Manila hemp, jute, kenaf, sisal, etc., and a method thereof. Bast fibers having improved tear strength and improved swelling properties.

[0014]

Surprisingly, if the alkaline solution is added to the bark of the bark under reduced pressure, the drawbacks of the known method can be avoided, while at the same time obtaining fibers with improved properties. It turned out to be. In contrast, the actual decomposition reaction can be carried out under atmospheric pressure, under pressure, or preferably also under reduced pressure, it is only important that the addition is carried out under reduced pressure. And, surprisingly,
This method is also outstandingly suitable for other bast fibers such as flax, cannabis, manila, jute, kenaf, sisal, etc., so that a similar improvement can be achieved in the quality of the barked fiber. There was found.

Accordingly, the present invention relates to a method for removing gum from debarked bast fibers by adding an aqueous alkaline solution under reduced pressure and allowing the debarked bast fibers to act on the debarked bast fibers under reduced pressure, atmospheric pressure or pressure.

In the present invention, the term "bast fibers" refers to all types of fibers normally included under this term such as ramie, flax, cannabis, Manila hemp, jute, kenaf and sisal, especially ramie, cannabis and flax. including.

The degumming process of the present invention employs conventional inorganic and / or organic bases, optionally with the addition of conventional additional agents such as detergents, dispersants and substances having sequestering, reducing and oxidizing effects. Additives can be used at conventional temperatures and base concentrations.

Generally, as the inorganic base, alkali metal hydroxides and alkali metal carbonates such as sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate are particularly preferable. In addition, sodium or potassium salts of C ₆ -C ₁₈ fatty acids, triethanolamine, the skilled person is familiar with the term “softeningri”.
conventional materials as nses) ", that is, in particular, C ₆ ~C
_It is also preferred to use cationic surfactants such as tetraalkylammonium salts of ₁₈ fatty acids or quaternary alkanolamine fatty acid esters instead of or with an inorganic base. For example, an aqueous alkaline solution can be added by impregnating debarked bast fibers with an alkaline solution under reduced pressure.

As a result of the addition under reduced pressure, the aqueous alkaline solution diffuses rapidly and completely into and along the fibers.
A more gentle and more uniform degumming is carried out in this way, i.e. a fiber product is produced with little damage and with permeation and swelling properties which are significantly superior to those which can be achieved up to now. Is known. This resulted in a uniformly degummed product, which significantly reduced the content of unseparated fibers, but which was not damaged. For example, in the case of ramies, the content of unseparated fibers after degumming according to the invention and before combing is about 0.1-0.5%, according to known methods about 1-5%. Is.

Surprisingly, the present invention can also reduce processing time by about an order of magnitude. For example, the gum removal treatment time with a 10% strength sodium hydroxide solution at 100 ° C. according to the method of the present invention is about 1 hour for ramie, while up to about 12 hours is required according to conventional methods. Due to this rapid gum removal, the manufacturing process is reduced by at least 50%.

Moreover, surprisingly, a minimum amount of liquid is already sufficient to carry out the degumming according to the invention, ie a considerable saving of water, chemicals and energy and a waste of water of about 80%. It has been found that it can be reduced to%. A debark bast fiber / alkaline solution liquor ratio of 1: 0.8 to 1: 2 is generally sufficient to carry out the process of the invention, while a liquor ratio of 1: 8 to 1:20 is well known. Be conventional in the way. For example, liquid ratios of up to 1: 5 are of course used in the present invention, although this is generally neither necessary nor suitable.

The advantages of the process according to the invention are always obtained after the addition of the aqueous alkaline solution under reduced pressure, regardless of whether the gum removal treatment is carried out under atmospheric pressure or under pressure or under reduced pressure. However, preferably, the total gum removal process can be carried out substantially or completely with the exclusion of air, whereby oxidative damage to the fibers in the presence of alkaline reagents can be substantially completely avoided in this way. Further, the removal of the reaction reagent is promoted when the gum removal is completed.

To obtain the advantages and effects of the invention, a partial vacuum is in principle sufficient during the addition of the aqueous alkaline solution and, if desired, during the subsequent degumming. However, preferably, the pressure during the addition of the aqueous alkaline solution is
About 200 mmHg or less, particularly preferably 100
mmHg or less, and the lowest limit of the pressure range is determined by the vapor pressure of the aqueous solution. The depressurization can be performed using a conventional vacuum pump, for example, a water jet pump.

Preferably, the degumming reaction can be carried out in a closed reaction system, ie under partial vacuum of air, in order to avoid as much as possible oxidative damage to the fibers. Depending on the reaction temperature, the vapor pressure of the aqueous solution and thus the total pressure in this case may rise, and under certain circumstances atmospheric pressure or higher values may be reached. However, it is also possible to eliminate the vacuum, ie to carry out the actual degumming under atmospheric pressure, or to let the reaction vessel contain air and / or an inert gas during the degumming reaction. Only the addition of the alkaline solution under reduced pressure is essential to the method of the invention.

Preferably, the method of the invention is a vacuum vessel (eg, glass or alkali resistant metal vessel) or vacuum bag (eg, glass or alkali resistant metal vessel) that is sufficiently resistant to heat and chemicals as is well known in the packaging industry. It is carried out in a vacuum bag made of PVC, polyethylene, rubber or the like. Due to the mechanical resistance of the bast fibers, a suitable vacuum can be achieved if a flexible container is used. In this case, preferably, the method puts the debarked bast fibers in a vacuum bag,
It can be done by evacuating, sealing the bag and then injecting the alkaline solution, for example using an injection needle. Evacuation reduces the volume, thus achieving optimal impregnation of the alkaline solution and making it easier to maintain the preferred solution ratio of 1: 0.8 to 1: 2.

As a result of the gentle gum removal and reduced processing time, relatively high base concentrations can be used in the process of the invention,
Therefore, pectin, fats and waxes are also separated from the fiber and still maintain the degree of polymerization.
Base concentration is not critical; however, in general, 1
The use of ~ 5N alkaline aqueous solution is preferred.

The temperature is also not important; however,
The gum removal (after addition of the alkaline solution) is expediently carried out at high temperature. Temperatures of 80 ° C to 150 ° C, for example about 100 ° C, are generally preferred.

If desired, the aqueous alkaline solution is a detergent (for example, alkali-resistant soap or sulfonates), a dispersant (for example, an alkali-resistant naphthalenesulfonic acid derivative), a substance having a sequestering effect (for example, ED).
TA, polyphosphates or complexing agents such as sulfite waste liquors), substances with a reducing action (eg sodium sulfite or sodium dithionite) and / or substances with an oxidizing action (eg peroxides such as hydrogen peroxide). Acid salts or peracid compounds (per-compound)
Conventional amounts of conventional additives such as s)) can be included.

The gums of the fibers obtained by the method of the present invention are low, generally about 3-8%. If desired, the gum balance can be adjusted by changing the gum removal conditions and treatment time.

When the gum removal is complete, the solution can be separated from the fibers by well known methods, such as suction filtration or centrifugation. The fibers are rinsed with water and further neutralized by conventional methods, for example conventional acids such as sulfuric acid, hydrochloric acid or acetic acid, and "oiling" (addition of lubricants and / or spin finishes), drying and breaking. Can be further processed by. It is also possible to neutralize with carbon dioxide (eg with flue gas) according to the new desired method. The separated liquid and, if necessary, part of the rinse water can be concentrated to the original concentration and, if desired, can be used in the subsequent degumming step.

If desired, a portion of the liquid can be suction filtered during the gum removal process, thus removing the gum with a minimum amount of rinse water. Water and additives can be added to the removed liquid. With this method, the amount of rinse water can be reduced even further. If desired, the separated gum itself can be utilized for heating purposes on activated carbon or in well-known fashion.

The process according to the invention can be carried out batchwise or continuously.

Compared to the known gum-removing bast fibers, the gum-removing bast fibers obtainable according to the invention have markedly improved properties and an intact fiber structure which has hitherto been impossible to achieve. Distinguished by. In the case of swellable ramie, flax and cannabis fibers, this manifests itself as a significantly improved swelling property, characterized in a manner known as the swelling factor, which can be measured as follows: a) fibrous material A relatively large number of individual dry fibers, optionally drawn from, are taut on a glass slide and covered with a cover glass. The fiber width (fiber thickness) of each dry fiber is calibrated. Eyepiece calibrated eye
It is measured at several points along each fiber under a microscope equipped with a piece of micrometer. b) The fibers on the microscope slide are then covered with a layer of water and left in a moist, sealed container for several hours. After removing excess water, the moist fiber is covered with a layer of zinc chloride / iodide solution (66 parts zinc chloride, 3 parts potassium iodide and 1 part iodine in 34 parts water). After 30 minutes, maximum swelling is generally reached. The excess solution is removed, a cover slip is overlaid, and then the width of the swollen fiber is measured microscopically for each case of the same fiber at the same point as a) along the fiber. Can be measured.

The swelling factor is defined as the quotient of the width of the swollen fiber and the width of the dry fiber.

A comparative examination of the conventional degumming fiber and the inventive degumming fiber shows that the latter has a significantly higher average swelling factor, in particular a fairly uniform swelling characteristic. For conventional degummed ramie fibers, average swelling factors in the range of about 1.4 to 2.5 were obtained, with a standard deviation of about 0,0 for the values obtained at various points along the fiber. It was in the range of 4-0.8. In contrast, the degummed ramie fibers of the present invention had an average swelling factor of 2.7-3.3 with a standard deviation along the fiber of about 0.1 or less. Similar results were obtained with flax and cannabis, with an average swelling factor of about 3 having a standard deviation along the fiber of about 0.1 or less for cannabis and flax fibers degummed according to the present invention.

Therefore, the present invention is at least 2.7.
Degumming ramie having an average swelling factor of and a standard deviation of the swelling factor along the fiber of about 0.2 or less,
Regarding cannabis and flax fibers. Ramie, cannabis and flax having an average swelling factor of at least 2.9 and a standard deviation of the swelling factor along the fiber of 0.1 or greater are preferred.

The swelling characteristics of the fibers depend to some extent on the type of plant, the growth state, the climate, the developmental stage of the fibers and the like. When comparing fibrous materials of different origin, a relatively wide range of deviations between fibers occurs under some circumstances. However, if fibers of the same origin are compared, the swelling factor varies little between fibers and, in the case of degummed fibers according to the invention, the range of variation is that of fibers degummed by conventional methods. Remarkably lower than the case. For example, in the case of conventional degummed fibers, the standard deviation of the swelling factor between fibers is 0.4 to 0.8 or higher, while for degummed ramie, cannabis and flax fibers according to the invention it is about A standard deviation of 0.3 or less was obtained.

If fibers of the same origin are used, the method of the invention can be used to produce fibrous materials having very uniform swelling properties both in the longitudinal direction of the fibers and also between the fibers.

Accordingly, the present invention provides a number of degumming ramies having an average swelling factor of at least 2.7 with a standard deviation of the swelling factor of 0.2 or less along the fibers and 0.3 or less between the fibers. , A fiber material containing flax or cannabis fibers.

As a result of the improved swelling properties of degummed fibers according to the invention, the penetration and absorption of dye molecules or matrix substances by the fiber-reinforced composite material is substantially enhanced. Fibers that have generally lost their swellability also lose their ability to absorb such materials.

Further, normal swelling means that there is no damage to the fiber structure and the molecular structure of cellulose and the molecular structure that binds cellulose fibrils to each other are still normal. Furthermore, the intactness of this structure has also been observed in the less swollen Manila hemp, jute, kenaf and sisal hemp.

The degummed bast fibers obtainable according to the invention are approximately 25 to 3 compared to the fibers obtainable by conventional methods.
Distinguish by 0% higher average elongation at break and significantly higher work at break. In the present invention, "work at break" means the product of the average break elongation in percent of the product and the force required. The values of the average elongation at break and work at break described in the present invention are given by Zellweger (Zellweger).
It was measured at 60% relative humidity under standard conditions by a Tesokide strength tester manufactured by Uster.
For example, when the degummed ramie fiber according to the present invention was measured, an average breaking elongation of 3.11 was obtained, while a commercially available conventional gum-depleted ramie fiber obtained a value of 2.24. In the case of degummed ramie fibers according to the invention the breaking work is 1
4.6 cN / denier and for commercial ramie fibers it was 6.3 cN / denier.

The process according to the invention thus produces degummed bast fibers with qualities hitherto unobtainable, which are distinguished in particular by their high mean elongation at break, which likewise relates to the invention. A preferred embodiment relates to degummed ramie fibers having an average elongation at break of at least 2.8%.

[0044]

The present invention will be described in more detail by the following examples. The examples were carried out using a vacuum bag.

Example 1 20 g of bark-peeled ramie was impregnated with a 10% strength (weight / volume) sodium hydroxide aqueous solution in a vacuum of 100 mmHg or less, and then treated at 100 ° C. for 1 hour while maintaining the vacuum. After the degumming step, the ramie fibers were thoroughly rinsed with hot water, acidified, treated with a spin finish, dried and treated with dry rub. The ramie fibers produced have the following properties: Fiber content not separated: 0.1-0.5% DP / degree of polymerization: 4200 Gum remaining: 3-8% Strength of test yarn: Decreased

Example 2 20 g of debarked ramie, containing the reaction solution suction filtered and the first rinse water from the previous degumming batch, was treated with sodium hydroxide and sulfonate (Invazine (Inv.
adin) EL, manufactured by Ciba AG Basel) Impregnation is performed in a vacuum container of 100 mmHg in a vacuum state containing 40 ml of the residual liquid supplemented with 1.3 g. Then, the vacuum vessel is heated at 100 ° C. for 1 hour. The degummed fiber was hot water washed and further treated as in Example 1. The ramie fibers produced have the following properties: Content of fibers not separated: 0.2% DP / degree of polymerization: 4100 Gum remaining: 3-8% Strength of test yarn: No decrease

Example 3 20 g of the bark-peeled ramie was treated with 60 g of sodium hydroxide per liter in a vacuum of 100 mmHg or less, Tinoclarit CBB (hydrogen peroxide stabilizer commercially available from Ciba AG Basel), 35 Impregnation with 40 ml of a gum removing aqueous solution containing 10% hydrogen peroxide and 10 ml Invadine EL (manufactured by Ciba AG Basel). The mixture is then treated at 100 ° C. for 1 hour. After removing gum
The fibers were washed with hot water, neutralized with acetic acid, produced with a spin finish and dried. The ramie fibers produced have the following properties: Content of fibers not separated: 0.4% DP / degree of polymerization: 3900 Gum remaining: 3-8% Strength of test yarn: Slight decrease

Claims (13)

[Claims] 1. A method for removing gum from debarked bast fibers using an alkaline aqueous solution, which comprises adding an alkaline aqueous solution under reduced pressure and causing the debarked bast fibers to act on the debarked bast fibers under reduced pressure, atmospheric pressure or pressure. 2. The method according to claim 1, wherein ramie, cannabis or flax are used as the bast fibers. 3. The method according to claim 1, wherein a debark bast fiber / alkali aqueous solution having a liquid ratio of 1: 0.8 to 1: 2 is used. 4. The method according to claim 1, wherein an aqueous solution of an alkali metal hydroxide or carbonate is used as the aqueous alkali solution. 5. The method according to claim 1, wherein the alkaline aqueous solution is added under a pressure of 200 mmHg or less. 6. The method according to claim 1, wherein a 1-5N alkaline aqueous solution is used. 7. The method according to any one of claims 1 to 6, wherein an alkaline aqueous solution is applied to the debarked bast fibers at 80 to 150 ° C. 8. The method according to claim 1, wherein an alkaline aqueous solution containing a substance having sequestration, a reducing or oxidizing action, a detergent and / or a dispersant is used. 9. A degummed bast fiber having a high average elongation at break as a product of the method according to any one of claims 1-8. 10. The degummed ramie fiber of claim 9 having an elongation at break measured at 60% relative humidity of at least 2.8%. 11. Degummed lamina, cannabis or flax having an average swelling factor of at least 2.7 and a standard deviation of the swelling factor along the fiber of 0.2 or less. 12. Degummed lamina, cannabis or flax having an average swelling factor of at least 2.9 and a standard deviation of the swelling factor along the fiber of 0.1 or less. 13. A huge number of gum removals wherein the average swelling factor of the fibers is at least 2.7, the standard deviation of the swelling factor is 0.2 or less along the fibers and 0.3 or less between the fibers. Fibrous material containing ramie, cannabis or flax fibers.