KR100280052B1 - Zeolite dispersion - Google Patents

Abstract

Aqueous dispersions comprising zeolite particles having hydrophobicity measured with less than 0.9% by weight of residual butanol as determined by residual butanol tests include stabilizing amounts of biogum. The dispersion preparation method comprises mixing the zeolite particles into a biogum and a dry mixture; Mixing the dry mixture into a homogeneous mixture with water under stirring. This dispersion is used to bond the zeolite particles to the fibers. In forming paper or cardboard by forming and dehydrating a cellulose fiber suspension in which dehydration is carried out in the presence of zeolite particles, a dispersion is added to the suspension prior to dehydration. Prior to making dry paper, nonwoven or fluff pulp in which the cellulose fibers are carried by the gasstream, the dispersion is dispersed in the fibers while the fibers are carried by the gasstream.

Description

Zeolite dispersion

Storage stability zeolite aqueous dispersions are disclosed in Japanese Patent Application Laid-Open No. 82-61614, in which a water-soluble cellulose derivative is used in combination with a water-soluble salt to stabilize the dispersion. However, the dispersion is not useful when the zeolite binds to the fiber surface. The dispersion according to JP 82-61614 is virtually unstable when applied to hydrophobic zeolites.

The present invention relates to an aqueous dispersion of hydrophobic zeolite particles and to the use of the dispersion as an adjuvant for bonding hydrophobic zeolites to the surfaces of natural and synthetic fibers in dry and wet conditions. Moreover, the present invention relates to dry and wet methods for the production of fibrous materials such as paper, cardboard, nonwovens, flake-dried pulp, the dispersions being used to increase the retention of added hydrophobic zeolites. By "holding power" is meant the relationship between the amount of additives preserved by the fibers and the total amount of additives added to the fibers in the processing step.

Thus, a problem to be solved by the present invention is to provide a stable aqueous dispersion of hydrophobic zeolite particles, which is useful when the hydrophobic zeolite binds to fibers. By hydrophobic zeolite is meant a zeolite having hydrophobicity measured with less than 0.9% by weight of residual butanol as measured by the residual butanol test.

This problem is solved by the aqueous dispersion described in the characterizing part of claim 1, wherein the dispersion comprises a biogum in a stabilizing amount.

Zeolite is an inorganic crystalline compound mainly composed of SiO ₂ and Al ₂ O ₃ in tetrahedral coordinates. The term “zeolite” in the present invention also includes other crystalline compounds of zeolite structure such as aluminum phosphate. Crystalline compounds of zeolite structure that can be used in the present invention are defined in “Atlas of zeolite structure types” (Second Edition, WM Meier, Butterworths, London, 1987).

In the present invention, the zeolite has a limited water absorption capacity. This hydrophobicity (water resistance) relates to the ability of organic substances to bind with non-polar compounds that make up the largest group. The present invention may include one or more kinds of zeolites, such as two hydrophobic zeolites or a combination of one or more hydrophobic zeolites and one or more hydrophilic zeolites.

In the present invention, the molar ratio of SiO ₂ to Al ₂ O ₃ in the tetrahedral coordinates should be at least 10: 1, in particular 12: 1 to 1000: 1, even 20: 1 to 500: 1.

The hydrophobicity of zeolites is determined by the residual butanol test published in GB-A-2,014,970. In this test the zeolite is activated by heating in air at 300 ° C. for 16 hours. 10 parts by weight of activated zeolite is then mixed with a solution consisting of 1 part by weight of 1-butanol and 100 parts by weight of water. The resulting slurry is stirred slowly at 25 ° C. for 16 hours. Finally, the residual content of 1-butanol in the solution is measured and expressed in weight percent. Thus, lower values indicate higher hydrophobicity.

In the present invention, hydrophobicity is distinguished by residual butanol content of less than 0.9% by weight, in particular less than 0.6% by weight. The residual butanol content is preferably at 0.001 to 0.5% by weight, in particular 0.0002 to 0.3% by weight.

Zeolites with high hydrophobicity after denaturation are pentasil, faujasite, mordenite, erionite and zeolite L. US-A-3,702,886 and US-A-4,061,724 disclose methods for preparing pentasil-type zeolites. Examples of pentasil zeolites are ZSM-5, ZSM-11, ZSM-8, ZETA-1, ZETA-3, NU-4, NU-5, ZBM-10, TRS, MB-20, Ultrazed, TsVks, TZ- 01, TZ-02 and AZ-1. Preferred zeolites in the present invention are ZSM-5 or ZSM-11 as defined in "High-Silica Aluminosilicate Zeolite Synthesis" (P.A. Jacobs). "Surface Science and Catalytic Reactions" (Vol. 33, Elsevier, 1987, 167-176) is incorporated by reference. Examples of posersite zeolites are Linde X, Linde Y, SAPO-37, CSZ-37, and LZ-210 (“Atlas of zeolite structure type”).

Many present dispersion / stabilizers, particularly low molecular weight dispersion stabilizers, adsorb to the inner surface of the zeolite to block the zeolite's ability to absorb; The same problem applies to surfactants. Biogum, however, is a heteropolysaccharide having a high molecular weight of 1 million or more and is produced by fermentation of carbohydrates under the action of microorganisms. An example of a biogum that can be used in the present invention is the biogum mentioned in US-A-5,234,493, which relates to a suspension of silica particles rather than zeolite particles and requires a stable surfactant compared to the present dispersion. Biogum is Xanthomonas, Arthrobacter, Azobacter, Agrovector, Alkali bacteria, Erwinia, Root muscle, Corticum, Serotinia, Stromatinia Or by carbohydrate fermentation by bacteria or fungi of Sclerotion; Mixtures of such biogum are useful in the dispersions of the present invention. The term "obtainable" means that the fermentation can be obtained through a synthetic process, not the only way to obtain the biogum. Preferred biogum is a gum that is obtainable by fermentation of bacteria of the genus Chisantomonas, ie xan gum.

The electrical conductivity of the dispersion of the invention is at least 3 mS / cm. Below this conductivity value, the stability of the dispersion rapidly decreases to a hard precipitate. In order to keep the heat content low in textiles, the conductivity is preferably less than 20mS / cm. The preferred conductivity of the dispersion is 4 to 15 mS / cm, in particular 4 to 8 mS / cm. The conductivity of the dispersion can be controlled by adding an appropriate amount of an electroactive material such as an alkali metal such as sodium sulfate, aluminum sulfate or sodium chloride or an inorganic acid such as sulfuric acid, hydrochloric acid or nitric acid.

The pH of the aqueous dispersion of the present invention is 2-7, in particular 3-5, to optimize dispersion stability.

The size of the hydrophobic zeolite particles can also affect the stability of the dispersion. Therefore, the particle size is preferably smaller than 15㎛. That is, about 50% by volume of the hydrophobic zeolite should have a particle size of less than 15 μm.

It is desirable that the dry solids content of the hydrophobic zeolite dispersion be as high as possible. The present invention makes it possible to obtain hydrophobic zeolite dispersions having a dry solids content of about 30-50% by weight using biogum of 0.1-8.0% by weight relative to the weight of hydrophobic zeolite particles; These dispersions have a moderate viscosity.

This dispersion can be used in the manufacture of packaging materials as described in EP-B-0 540 075 or in the sizing of paper published in US-A-5,374,335 to reduce dust problems and lower energy and labor costs. The activity of the hydrophobic zeolite powder is blocked by adsorption of material from the air prior to suspension in water, but once the hydrophobic zeolite is suspended in water, such deactivation adsorption is prevented; Thus, the dispersion ensures the activity of hydrophobic zeolites. Known suspensions are unstable and, if not steadily stirred, produce precipitates and cause problems with administration, measurement and delivery. This problem is eliminated by the present invention to produce deliverable hydrophobic zeolite dispersions.

Another advantage of the present dispersion is that it simplifies the surface application to paper and cardboard compared to the more unstable known dispersions.

The dispersions provide good dehydration and preservation when added to the fiber stock in the wet manufacturing process of pulp or paper. This effect is at least as good as the best results obtained when known stabilizers are used. The present invention therefore relates to a process for forming paper or cardboard by forming and dehydrating suspensions of cellulose fibers and auxiliary fillers, dehydration is carried out in the presence of hydrophobic zeolite particles and the dispersion is added to the suspension prior to dehydration. In addition, the present dispersions provide very good retention in terms of fluff and fluff pulp, and the preserved amount of hydrophobic zeolite in the fluff is increased by the present dispersion after the shredding of the fluff pulp. . The preservation of hydrophobic zeolites in the fluff obtained by dry-truffing the fluff pulp to which hydrophobic zeolites are added while the pulp is in the aqueous suspension is 20-30% when the present dispersion is used instead of the conventional hydrophobic zeolite / water slurry. Can be increased.

The hydrophobic zeolite dispersion may also be used for hydrophobic zeolite applications on the surface of natural and synthetic fibers when added to the fibers while in the dry state. Accordingly, the present invention relates to a process for producing dry paper, nonwoven or fluff pulp, wherein the dispersion is dispersed in the fiber while the fiber is in a dry state, in particular by the flow of gas such as air, nitrogen or carbon dioxide Is carried.

Conservation is a significant variable compared to the results published in EP-B-0 540 075 and US-A-5,374,335. The present invention provides high shelf life in dry and wet systems regardless of the type of fibers used or whether other preservatives are present in the system.

Apart from cellulosic fibers obtainable by CTMP or kraft processes, the dispersions can also be applied to various synthetic fibers made of nylon, polyacetate, viscose, polyaramid.

The present hydrophobic zeolite dispersion can be prepared by the following method:

I) hydrophobic zeolite powder is mixed into a biogum and dry mixture;

II) the dry mixture is mixed with water and a homogeneous mixture with stirring;

III) The conductivity or pH of the homogeneous mixture is controlled.

Adjuvants such as fungicides may be added to the dispersion.

Mixing of the hydrophobic zeolite particles with biogum in the dry state gives the dispersion the best stability.

Another process for preparing dispersions consists of the following steps:

I) preparing an aqueous solution in which hydrophobic zeolite particles are dispersed in water;

II) conductivity or pH control of the aqueous solution;

III) Dispersion of biogum in aqueous solution.

Example 1

The hydrophobic zeolites used were ZSM-5 type, having a molar ratio of SiO ₂ to Al ₂ O ₃ in tetrahedral coordinates of 32 and hydrophobicity measured with residual butanol of less than 0.9% by weight as measured by the residual butanol test. This hydrophobic zeolite powder has a pH of 3.7 in an aqueous slurry. The dry solids content of the hydrophobic zeolite is 96% by weight and the average particle size is about 10 μm. 208 g hydrophobic zeolite powder is mixed with 0.8 g dry xanthan gum. The dry mixture is poured into about 290 g of water and forced to stir. After stirring for 10 minutes the pH is 3. and the conductivity measured according to SIS 028123 is 033 mS / cm. 2.5 g of anhydrous Na ₂ SO ₄ are added under stirring and stirred for 5 minutes. The conductivity is then 5.5mS / cm. The filtered dispersion is poured into a plastic bottle by a stirrer for 3 days after filtration. The resulting dispersion, which is easy to stir, does not show a transparent phase and no precipitate is found in the plastic bottle. The conductivity is 4.36 mS / cm and the pH is 3.6. After two weeks the dispersion according to the invention is still easy to stir and no precipitate is present.

Example 2

Example 1 was repeated except that Na ₂ SO ₄ was not added. After 3 days a 12 mm clear liquid phase appeared and the rest of the sample was hard as stone. The conductivity was 0.23 mS / cm and the pH was 4.0. This example shows that the electrical conductivity of the dispersion may be an important feature in the present invention.

Example 3

Example 1 was repeated except that the pH was adjusted to 2.5 by sulfuric acid and no Na ₂ SO ₄ was added. After 3 days the entire dispersion sample was as hard as a stone. The conductivity was 1.378 mS / cm and the pH was 2.7. This example showed that the electrical conductivity of the dispersion is an important feature in the present invention.

Example 4

Hydrophobic zeolite powder of the same kind as used in Example 1 and having a pH of 10.0 in an aqueous slurry was used. The dry solids content of the hydrophobic zeolite was 96% by weight and the average particle size was 8 μm. 208 g hydrophobic zeolite powder was mixed with 0.8 g dry xanthan gum. The dry mixture is poured into 290 g of water and vigorously stirred. After 10 minutes the conductivity was 0.33 mS / cm. Sulfuric acid was added and stirred for 5 minutes to adjust the pH to 3.0. The conductivity was then 5.5 mS / cm. After filtration the dispersion was stirred for 3 days as in Example 1. The resulting dispersion showed no phase separation and was easy to stir. The conductivity is 5.02 mS / cm and the pH is 3.0. After 2 weeks the dispersion was still easy to stir and showed no phase separation.

Example 5

Example 4 was repeated except that half sulfuric acid was added and Na ₂ SO ₄ was added until the same conductivity reached in Example 4 was obtained. After 3 days no phase separation was detected and the dispersion was easy to stir. The conductivity was 5.48 mS / cm and the pH was 7.4. After 2 weeks the dispersion was easy to stir and there was no phase separation.

Example 6

Example 1 was repeated except that ethyl hydroxyethyl cellulose was used instead of xan gum. Some of the samples were not stirred; This site shows a transparent phase and a small amount of precipitate, which is easily slurried by stirring. However, stirring made the sample very hard. The conductivity is 6.85 mS / cm and the pH is 3.7. This example shows that the known art does not provide a stable dispersion of hydrophobic zeolites.

Example 7

Example 1 was repeated except that half of the xanthan gum used was replaced by ethylhydroxyethyl cellulose. Some of the samples were not stirred; This site shows good stability. Agitation, however, produced precipitates that were difficult to slurry by stirring. The conductivity is 6.85 mS / cm and the pH is 3.7. This example shows that the present invention can be used to improve dispersions of the prior art.

Example 8

An aqueous dispersion of hydrophobic zeolites of the same kind as in Example 1 was prepared using Dispex N-40, an anionic dispersion, at concentrations of 0.2, 0.5 and 1% by weight relative to dry hydrophobic zeolite. The dry content of the dispersion was 20-40% and the pH was 4.5, 7 and 9. The precipitate appeared very quickly in the dispersion regardless of the mixing conditions. After one day the hydrophobic zeolite material precipitated out as a sea cake hard. This example shows that the known art does not provide a stable dispersion of hydrophobic zeolites.

Example 9

Example 1 was repeated except that 21 g of Na ₂ SO ₄ was added instead of 2.5 g of Example 1. After stirring for 3 days, a 3 mm thick precipitate was deposited on the bottom. The conductivity is 25 mS / cm and the pH is 3.0. This example shows that the electrical conductivity of the dispersion is an important feature in the present invention.

Example 10

The hydrophobic zeolite and xanthan gum used in Example 1 were added to a fiber suspension comprising fibers from kraft pulp of 60% hardwood and 40% softwood, and Table 1 shows the retention test results. Pulp concentration is 1% by weight. Hydrophobic zeolite is added in an amount of 10 kg per tonne of dry pulp. The suspension was dehydrated and the fibers formed into sheets and dried at 105 ° C. The degree of preservation of the hydrophobic zeolite is determined by the ash content which burns at 925 ° C. for 120 minutes and the residual amount is measured. In Test Nos. 1 and 3, hydrophobic zeolites were added to the fiber suspension separately from xanthan gum and in Test Nos. 2 and 4, the hydrophobic zeolites were mixed with xanthan gum before being added to the fiber suspension. In Table 1 the addition of hydrophobic zeolite and xan gum was calculated for 1 ton of dry pulp.

Obviously, the premixing of xan gum and hydrophobic zeolite shows better preservation than the separate mixing.

Example 11

In test A, an aqueous dispersion of hydrophobic zeolite was prepared and added to the fiber suspension described in Example 10 while stirring at 1000 rpm. The amount of hydrophobic zeolite added is 10 kg per ton of dry pulp. The suspension is dehydrated and the fibers are formed into sheets and dried at 105 ° C. The recontent of the sheet after formation is measured as in Example 10. Thereafter, the recontent of the obtained fluff is measured by drying-torn into the fluff with a sheet. In test B, the hydrophobic zeolite aquatic product further comprises 40 g of xanthan gum per tonne of dry pulp. The test results are described in Table 2. The recontent was converted to the amount of hydrophobic zeolite present in the pulp sheet and fluff.

As can be seen from Table 2, the preservation of the hydrophobic zeolite after formation and dry-tear is better when using the dispersion according to the invention.

Example 12

An aqueous solution containing 2 g / L of hydrophobic zeolite used in Example 1 was sprayed onto the prepared pulp sheet as described in Example 10. The amount of hydrophobic zeolite added corresponds to 3 kg of hydrophobic zeolite per ton of dry pulp. In test C, the solution additionally contained 0.04% xanthan gum and no biogum was added in test D. After spraying the pulp sheet is torn in a hammer mill and the recontent is measured as in the previous example and converted to the amount of hydrophobic zeolite present in the torn pulp. The test results are shown in Table 3.

The shelf life of hydrophobic zeolites is better when using the dispersions according to the invention.

The hydrophobic zeolites used were Y-type and had a hydrophobicity measured with 0.28 wt% residual butanol as measured by the SiO ₂ : Al ₂ O ₂ ratio of 29, residual butanol test. This hydrophobic zeolite powder has a pH of 3.7 in an aqueous slurry. The dry solids content of the hydrophobic zeolite is 96% by weight. 208 g hydrophobic zeolite is mixed with 0.8 g dry xanthan gum. The dry mixture is poured into 290 g of water and stirred for 10 minutes as in Example 1, the pH is 3.6 and the conductivity is 0.33 mS / cm. 2.5 g of Na ₂ SO ₄ was added as in Example 1 and the conductivity was then 5.6 mS / cm. The stirred dispersion is poured into a plastic bottle for 3 days after filtration. The resulting dispersion is easy to stir and shows no transparent phase and no precipitate is found in the plastic bottle. Even after 1.5 weeks the dispersion was easy to stir and no precipitate was present.

Claims (18)

An aqueous dispersion comprising zeolite particles having a hydrophobicity measured with residual butanol of less than 0.9% by weight as measured by the residual butanol test, wherein the dispersion comprises a biogum in an amount to stabilize the dispersion. The aqueous dispersion of claim 1 wherein the electrical conductivity of the dispersion is between 3 mS / cm and 20 mS / cm. The biogum of claim 1, wherein the biogum comprises Xanthomonas, Asrovector, Azovector, Agrovector, Alkali, Erwina, Root muscle, Corticum, Shererotinia ( Aqueous dispersion, characterized in that it is obtainable through fermentation of carbohydrates by bacteria or fungi such as Scherotinia, Stromatinia or Sclerotiom. The aqueous dispersion of claim 1 or 2, wherein the biogum is xan gum. The aqueous dispersion according to claim 1 or 2, characterized in that the zeolite has a hydrophobicity measured with less than 0.6% residual butanol as measured by the residual butanol test. The aqueous dispersion according to claim 1 or 2, characterized in that the dispersion has a pH of 2-7. The aqueous dispersion according to claim 1 or 2, characterized in that the conductivity of the dispersion is 4 to 15 mS / cm. The aqueous dispersion according to claim 1 or 2, characterized in that the dispersion comprises 0.1 to 0.8% by weight of biogum and has a dry solids content of 30 to 50% by weight relative to the zeolite particles. A process for preparing a dispersion comprising a zeolite particle having hydrophobicity measured as 0.9 wt% residual butanol as measured by the residual butanol test, comprising: I) mixing zeolite particles and biogum into a dry mixture and II) stirring the dry mixture with water Dispersing to form a homogeneous mixture. 10. The method of claim 9, wherein the electrical conductivity or pH of the homogeneous mixture is controlled. A process for preparing a dispersion comprising a zeolite particle having hydrophobicity measured as 0.9% by weight residual butanol as measured by a residual butanol test, comprising: I) preparing an aqueous solution in which zeolite particles are dispersed in water; II) dispersing the biogum in an aqueous solution. The method of claim 11, wherein the pH or electrical conductivity of the aqueous solution is adjusted before the biogum is dispersed in the aqueous solution. A dispersion comprising zeolite particles having hydrophobicity, which is used to bind zeolite particles to the fiber surface and is measured as 0.9% by weight residual butanol as measured by residual butanol test. The dispersion of claim 13 wherein the dispersion is applied to the fiber while the fiber is in a dry state. 15. The dispersion according to claim 13 or 14, wherein the fibers are used in flake-dry pulp, fluff pulp, dry-paper or nonwoven manufacturing processes. 14. The dispersion as claimed in claim 13, wherein said dispersion is applied to the fiber and used to make pulp, paper, cardboard or nonwovens while the fiber is suspended in an aqueous solution. A process for producing paper or cardboard by forming and dehydrating a cellulose fiber suspension in which dehydration is carried out in the presence of zeolite particles, wherein the dispersion comprises a zeolite particle having hydrophobicity measured as 0.9% by weight residual butanol as measured by a residual butanol test. The method of claim 1, characterized in that added to the suspension prior to the dehydration. In a method for producing a dry paper, nonwoven fabric or fluff pulp carried by a stream of cellulose fibers, a dispersion comprising hydrophobic zeolite particles as measured by 0.9% by weight residual butanol as measured by a residual butanol test results in a fiber Dispersion in the fibers while being carried by the stream.