阅读说明：本技术 用作过氧化物稳定剂的成分 (Ingredients used as peroxide stabilizers ) 是由 李志蛟 刘瑞 于 2018-11-07 设计创作，主要内容包括：提供了一种在纸浆漂白中用作过氧化物稳定剂的组合物,其包含亚氨基二琥珀酸(IDS)或其盐和聚天冬氨酸钠盐(PASP)。(A composition for use as a peroxide stabilizer in pulp bleaching comprising iminodisuccinic acid (IDS) or a salt thereof and polyaspartic acid sodium salt (PASP) is provided.)

1. A composition for use as a peroxide stabilizer in pulp bleaching, said composition comprising:

-iminodisuccinic acid (IDS) or a salt thereof, and

polyaspartic acid sodium salt (PASP),

wherein the weight ratio of the iminodisuccinic acid (IDS) or the salt thereof to the polyaspartic acid sodium salt (PASP) is 1: 20 to 20: 1, preferably in a weight ratio of 1: 10 to 10: 1, more preferably in a weight ratio of 1: 1 to 3: 1.

2. composition according to claim 1, characterized in that it comprises, in a weight ratio of 2: 1 or a salt thereof and polyaspartic acid sodium salt (PASP).

3. Composition according to claim 1 or 2, characterized in that the molecular weight of the polyaspartic acid sodium salt is in the range of 2000-.

4. Composition according to any one of the preceding claims, characterized in that the pH of the composition is in the range of 9-12, preferably pH > 10.

5. Use of a composition according to any of the preceding claims as a peroxide stabilizer in the bleaching of high yield pulp.

6. The use according to claim 5, wherein the high yield pulp comprises high yield mechanical pulp, high yield chemimechanical pulp, semichemical pulp or any combination thereof.

7. A method for bleaching pulp, wherein a composition according to any of the preceding claims 1-4 is added to the pulp before and/or during bleaching.

8. A method according to claim 7, characterized in that the composition is added to the pulp in a pretreatment stage of the pulp.

9. The method according to claim 7 or 8, characterized in that the pulp comprises high-yield mechanical pulp, high-yield chemimechanical pulp, semichemical pulp or any combination thereof.

10. The method according to any of the preceding claims 7-9, characterized in that the composition is added in an amount of 0.1-5kg/t pulp (dry) or 0.5-5kg/t pulp (dry).

Technical Field

The present invention relates to a composition for use as a peroxide stabilizer in pulp bleaching and a process for bleaching pulp according to the independent claims presented below.

Background

Hydrogen peroxide is commonly used as a bleaching chemical in pulp bleaching processes. However, hydrogen peroxide will decompose to hydroxyl radicals under the high temperature and high alkali conditions found in pulp production. Hydrogen peroxide is also catalytically decomposed in the presence of metal ions such as iron, manganese and copper. The hydroxyl radicals formed by the decomposition of hydrogen peroxide will deteriorate and darken the fibers. Furthermore, due to the decomposition, higher amounts of hydrogen peroxide have to be used in the bleaching process, leading to increased costs.

To increase the efficiency of hydrogen peroxide, stabilizers are usually added during the preparation of the peroxide bleach. Sodium silicate (water glass) is commonly used to stabilize hydrogen peroxide when bleaching mechanical pulp to high brightness because of its relatively high cost-effectiveness. Although silicate is an effective stabilizer and is beneficial for peroxide bleaching, it can have serious detrimental effects in pulp and paper making processes. Silicates can deposit on the paper machine and they also introduce anionic properties (anionicity) into the paper making system, resulting in higher wet end chemical consumption. Thus, there is a continuing need for cost-effective silicate-free peroxide stabilizers that address the above-mentioned problems.

Furthermore, due to the low price, phosphorus sequestrants such as diethylenetriamine penta (methylene phosphonic acid) (DTPMP) and hydroxyethylidene diphosphonic acid (HEDP) are commonly used as peroxide stabilizers in mechanical pulp bleaching. However, the phosphorus sequestrants can cause severe fouling not only in the pulp lines, but also in the evaporators, and the fouling further leads to reduced pulp production, and even to shutdown for cleaning. Phosphorus chelating agents can also be environmentally hazardous.

There is a continuing need for cost-effective peroxide stabilizers, especially in the bleaching of high-yield pulps. High yield pulps have low production costs and it would be advantageous if bleaching could also be performed in a cost-effective manner.

Summary of The Invention

It is an object of the present invention to reduce or even eliminate the above-mentioned problems occurring in the prior art.

It is an object of the present invention to provide a novel, cost-effective hydrogen peroxide stabilizer in a pulp bleaching process, particularly suitable for use in high yield pulp bleaching processes.

It is an object of the present invention to provide a biodegradable phosphorus-free peroxide stabilizer, especially in pulp bleaching processes.

Furthermore, it is an object of the present invention to provide a peroxide stabilizer composition which provides a synergistic effect by improving or at least maintaining the stability of the peroxide during bleaching and providing high whiteness to high yield pulp. In order to be able to replace low yield bleached chemical pulp in various products, it is necessary to achieve higher brightness and reduce the chemical cost of bleaching high yield pulp.

To achieve the objects stated above in particular, the invention is characterized by what is stated in the characterizing part of the appended independent claim.

Some preferred embodiments of the invention will be described in the other claims.

The embodiments and advantages mentioned herein relate, where applicable, to the compositions, methods and uses according to the invention, even if not always explicitly mentioned.

A typical composition for use as a peroxide stabilizer in pulp bleaching according to the present invention comprises:

-iminodisuccinic acid (IDS) or a salt thereof, and

polyaspartic acid sodium salt (PASP),

wherein the weight ratio of the iminodisuccinic acid (IDS) or the salt thereof to the polyaspartic acid sodium salt (PASP) is 1: 20 to 20: 1, preferably in a weight ratio of 1: 10 to 10: 1, more preferably in a weight ratio of 1: 1 to 3: 1.

a typical process according to the invention comprises adding the composition according to the invention to the pulp, preferably to a high yield pulp, before and/or during bleaching. High Yield Pulp (HYP) refers to pulp produced from raw materials at yields in excess of 85% by mechanical processes or combined chemical and mechanical processes.

It has been found that a mixture of iminodisuccinic acid (IDS) or a salt thereof and polyaspartic acid sodium salt (PASP) provides good stabilization of hydrogen peroxide during pulp bleaching and also provides better whiteness. The composition according to the invention is also capable of chelating heavy metal ions, thereby preventing decomposition of hydrogen peroxide.

The peroxide stabilizer composition according to a preferred embodiment of the present invention is phosphorus-free and biodegradable, which is beneficial to the environment. The composition according to the invention also makes it possible to suppress the scaling that is common in pulping processes and also makes it possible to reduce the scaling caused by shutdown, which makes it possible to reduce cleaning costs and dust problems.

The composition according to the invention comprises iminodisuccinic acid (IDS) or a salt thereof and polyaspartic acid sodium salt (PASP) in a weight ratio of 1: 20 to 20: 1, preferably in a weight ratio of 1: 10 to 10: 1, more preferably in a weight ratio of 1: 1 to 3: 1. in a preferred embodiment according to the invention, the composition comprises a mixture of two or more of the following components in a weight ratio of 2: 1 or a salt thereof and polyaspartic acid sodium salt (PASP).

In one embodiment according to the invention, a composition comprises a water soluble salt of iminodisuccinic acid, such as tetrasodium iminodisuccinate, which is the sodium salt of iminodisuccinic acid.

Polyaspartic acid sodium salt (PASP) is a biodegradable water-soluble polymer based on the amino acid aspartic acid. According to one embodiment of the present invention, the molecular weight of the sodium salt of polyaspartic acid is in the range of 2000-8000Da, more preferably in the range of 3000-5000 Da.

The composition according to the invention is an alkaline liquid product, so that the composition can be added directly to the pulping and bleaching process and/or mixed with other pulping chemicals. The alkaline composition according to the invention may be added anywhere in the pulping process, for example, pretreatment of the pulp, bleaching of the pulp, storage towers, or mixing with other chemicals. In an exemplary embodiment according to the invention, the pH of the composition is in the range of 9-12, preferably the pH is > 10.

The composition according to the invention is preferably premixed. The viscosity of the premix composition comprising iminodisuccinic acid (IDS) or a salt thereof and polyaspartic acid sodium salt (PASP) according to the invention is typically about 10-40 mPas.

The composition according to the present invention may further comprise a chelating agent, a dispersing agent, a penetrant, an activator, or any combination thereof. The chelating agent may include, for example, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), ethylenediamine-N, N' -disuccinic acid (EDDS), aspartic Acid Ethoxysuccinate (AES), diethylenetriaminepenta (methylenephosphonic acid) (DTPMP), and/or hydroxyethylidenediphosphonic acid (HEDP). The dispersant may include, for example, polyacrylic acid (PAA) and/or polyacrylic acid sodium Salt (PAAs). The osmotic agent may include, for example, fatty alcohol polyoxyethylene ether AEO, OEP, AEP, JFC, and/or APG. Activators may include, for example, sodium nonanoyloxybenzene sulfonate (NOBS), Tetraacetylethylenediamine (TAED), and/or polyalkylene glycol PAG.

The composition according to the invention is used as a peroxide stabilizer in pulp bleaching. In a preferred embodiment according to the present invention, the composition is used as a peroxide stabilizer in the bleaching of high yield pulp, providing a cost-effective bleaching process and allowing the chemical costs of high yield pulp to be kept low and the whiteness of the pulp to be maintained high. The high-yield pulp may include high-yield mechanical pulp, high-yield chemimechanical pulp, high-yield semichemical pulp, or any combination thereof. High yield mechanical pulp can be produced by a variety of mechanical pulping processes, such as Thermal Groundwood (TGW) pulping, Stone Groundwood (SGW) pulping, Pressure Groundwood (PGW) pulping, disc Refiner Mechanical (RMP) pulping, pressure disc refiner mechanical (PRMP), thermomechanical pulping (TMP), Extrusion Mechanical Pulping (EMP), and/or Bio-mechanical pulping (Bio-MP). The chemi-mechanical pulp may be, for example, chemi-thermo-mechanical pulp (CTMP), thermo-mechanical chemical pulp (TMCP), thermo-chemical-mechanical pulp (TCMP), bleached chemi-thermo-mechanical pulp (BCTMP), chemi-mechanical pulp (CMP), Alkaline Peroxide Mechanical Pulp (APMP) and/or pre-treated disc refiner chemical alkaline peroxide mechanical pulp (PRC-APMP). The high yield pulp may comprise semichemical pulp (SCP), neutral sulfite semichemical pulp (NSSC) and/or alkaline sulfite semichemical pulp (ASSC).

According to one embodiment of the invention, the composition is added in an amount of 0.1-5kg/t pulp (dry) or 0.5-5kg/t pulp (dry) in order to achieve the desired stabilization.

Experimental part

The invention will be better understood from the following examples, which are given for the purpose of illustration and are not to be construed as limiting the invention.

Stability test

The physical properties and stability of IDS, PASP and mixtures of IDS and PASP (mass ratio 2: 1) were examined.

The pH was measured by a Mettler Toledo SN657 pH meter without dilution. The viscosity was measured by a Brookfield viscometer (#61 spindle, 60 rpm). The density was measured by a Mettler Toledo DA-100M densitometer at 20 ℃.

Method for testing the solids content: about 10g of the sample was weighed on a weighed aluminum plate. The sample was dried at 120 ℃ for 4 hours and then cooled in a desiccator (exicator) for 20 minutes. Dry samples were weighed on an aluminum plate.

Table 1 test results for pH, viscosity, solids content and density.

The stability of the samples over one month was studied at 5 ℃, 20 ℃ and 45 ℃.

TABLE 2 stability test results

All three samples were stable and homogeneous over a month at 5 ℃, 20 ℃ and 45 ℃. The molecular weight of the PASP used in the test (CAS number 181828-06-8, 35608-40-6) was about 4800 as analyzed by GPC instruments. The IDS used in the test was tetrasodium iminodisuccinate.

Application examples: peroxide stabilizer evaluation using mixed soda

And (3) testing procedures:

1. a 30g sample of bleached chemithermomechanical pulp (BCTMP) at an o.d. consistency of 35% was weighed.

2. The stabilizers used in the test were diluted to 10%. The mixed soda and diethylenetriaminepentaacetic acid (DTPA) were mixed together.

3. The pulp sample was heated in a microwave oven for one minute, and then stabilizer, premixed mixed soda and DTPA, peroxide and balance water were added to the pulp sample. The pulp sample was then placed in a water bath under bleaching conditions.

4. After bleaching, 5g of o.d. pulp was taken out and diluted to 1000mL with DI water and the pH was adjusted to 4.7-5.2. Handsheets using a buchner funnel were removed and compacted, then air dried for 24 hours, compacted again and then analyzed for whiteness.

5. A 10g or 15g o.d. pulp sample was taken and diluted to 10% with ID water. The pH and residual peroxide were measured from the filtrate.

The stabilizers used in the tests are described in table 3. PASP and IDS are the same as those used in the stability test. The results are shown in Table 4. Test 1 is a reference measurement.

As a summary of the application examples, mixtures of IDS and PASP according to the invention provide better whiteness than IDS or PASP alone. The composition according to the invention provides similar whiteness gains compared to commercial Fennobrite C5022 (camila) stabilizer. The mixture of IDS and PASP according to the invention provides effective bleaching due to less residual peroxide.

Table 3.

TABLE 4 results