SE514446C2 - Concentration determination method for alkyl ketene dimers in grist and back water - Google Patents

Abstract

The method determines transmitted and/or diffused light at temperatures below and above phase conversion in an alkyl ketene dimer sample of grist or back water, the difference between the two measurements is calculated. This difference amounts to the difference in turbidity (delta NTU). Turbidity is measured after removal of coarse fibres. The coarse fibres are removed by the addition of acid and possible filtration of the grist solution or back water. A grist soln. or back water with known concentration is produced and used as standard. The concentration of alkyl ketene dimers in the sample is calculated in accordance with standard addition technique.

Description

o oooocm .v Mr f. : - _ .. 4,. f, n n .. «._ .kr» n occc te n - - r .r ox x <i <r t oc m- or »u 2 Backwater is the water that is separated from the stock on the paper machine wire and pressed. The backwater generally contains fiber residues, sometimes also fillers, dyes, AKD, resin adhesives, etc. and is generally recycled in the process.

WO 93/07484 (Roberts et al.) Relates to a method for analyzing samples of AKD by treating the sample or extract thereof with a reagent, preferably consisting of an amino-substituted pyridine ring, which reacts with AKD to a detectable derivative thereof. detection is accomplished by spectroscopy of said derivative.

Paperchem no. 65-01523, entitled "Analysis of Alkyl Ketene Dimer (AKD) by potentiometric titration", Nyarku et al., Discloses a potentiometric titration method for determining milligram amounts of AKD in non-aqueous solvents. The method involves the addition of chloroform solutions of AKD to an excess of an organic base followed by titration of an excess base with perchloric acid in glacial acetic acid.

Thus, there is no simple method available today for analyzing AKD at paper mills or as an at-line or on-line method at the paper machine. The method used in paper mills today is, for example, HPLC, which is a rather complicated method that must be handled by experts.

There is thus a great need for a simple method for AKD analysis and the inventors have therefore for many years tried to find a suitable method for measuring AKD, which can easily be used for frequent analyzes at paper mills, such as at-line or on-line. measurements of AKD.

With the present invention, which is based on a specific physical property of AKD, namely phase conversion between molten and solid AKD, a suitable and simple method for determining AKD in stock and backwater has been obtained, which method solves the above-mentioned problems. ». <- r e - n <. <4 r _ _: z. .. c er eo r r c rv. .. 1.:. e am .. c 1 <- c ~ _ .t .n cec: co e \ oc f. n - .n år. e <c <«. . <«. ae mr cor na (mr. f. 3 The melting point of AKD is between 45-65 ° C depending on the nature of the fatty acid tail. When AKD is heated, a single-phase conversion is obtained which is approximately 10 ° C below the melting point. However, when AKD is cooled, said phase conversion changes to a lower temperature of about 2s-35 ° c.

We have noted that the transmitted and / or scattered light such as the turbidity of dilute pure AKD solutions is significantly affected when said solutions are cooled / heated. The transmitted and / or scattered light of the AKD solutions depends partly on the particle size and partly on the refractive index. The AKD's refractive index changes during the phase transformation that affects the transmitted and / or scattered light as well as the turbidity and is lower at a temperature above the point for phase transformation that is related to the melting of AKD.

The measurement of the transmitted and / or scattered light as well as the turbidity is easy to carry out because it is really only a matter of visual determination based on the measurement of the attenuation of transmitted and / or scattered light. Either visual comparison with known standards or photoelectric detection can be used to measure the amount of light transmitted and / or scattered by the cloudy solutions.

The turbidity values are normally expressed as NTU.

An example of a commercially available turbidimeter is Analite Novasina, Pfäffikon, Switzerland.

However, the absolute level of turbidity in stock or backwater can not be correlated to the concentration of AKD, as said system also contains a high proportion of other colloids and particles which also affect the turbidity (background noise, ie fine fibers and small amounts of fillers, and the variations are too great). According to the present invention, the effect of the phase change on the transmitted and / or scattered light and according to a preferred embodiment of the invention the turbidity, which is specific for AKD, is used to determine the concentration of AKD in stock and backwater. The difference in transmitted and / or scattered light as well as the turbidity at the temperature before and after the phase change depends on the concentration of AKD and can be used as a method for determining the concentration. Thus, according to a preferred embodiment of the invention, the turbidity is measured before and after the phase transformation and the difference (delta turbidity) is determined. The size of the said difference depends only on the concentration of AKD and the background turbidity is of less importance for reliability.

The method according to the invention can be used on stock and backwater containing from 1 ppm AKD.

Methods other than the use of turbidity, based on measurements of transmitted and / or scattered light, can of course be used according to the invention.

The transmitted light of the primary beam refers to the amount of light scattered in the sample and it is therefore also possible to use this signal according to the invention.

AKD is preferably desorbed from fibers / fillers in stock or backwater by the addition of acids such as sulfuric acid, hydrochloric acid and nitric acid, etc. and the samples are optionally stirred and filtered to remove coarse fibers.

When calcium carbonate is used as a filler (eg chalk), the addition of an acid to the sample also gives a solution of calcium carbonate which results in lower background turbidity.

The addition of a salt such as aluminum chloride, calcium chloride, etc. can thus give a more efficient desorption of AKD from fibers / fillers. e _ r. <.-. rn (- en r 1 .. <vo or <-: cf »: crf fevo <«; e \ rxr L r cr. om n: 5 The method according to the invention can be used not only to determine the concentration of AKD in stock and backwater_ by using the standard addition method or by a calibration method but also for determining the first passenger retention by the following equation: Delta NTU in the headbox - delta NTU in backwater Delta NTU in the headbox The method according to the invention is further defined in the claims and the following examples.

Example 1 The applicability of the method was tested on a laboratory stock consisting of 0.2 g / l birch fibers and 0.2 g / l filler chalk.

An AKD dispersion (15% dry matter content) was added to the stock so that the concentration became 40 mg / l. This stock was analyzed according to the developed method by a person who was unfamiliar with the concentration of AKD in the stock.

The stock was divided into two parts, named A and B (500 ml each) by said person. The methodology of the analysis was according to the "standard addition" method, which involved the addition of a known amount of substance to be analyzed to a portion of the unknown solution and the concentration in the starting solution was then calculated. In this case, AKD was added to stock B in an amount corresponding to an addition of 22.5 mg / l. To each stock was added 5 ml of a solution containing aluminum chloride (20%) in 6M hydrochloric acid. The stock was then transferred to a Britt Dynamic drainage vessel where it was filtered by vigorous stirring (3000 rpm) through a wire (mesh 200) and the filtrate was recovered.

The filtrate was then heated to 60 ° C and cooled. The turbidity was determined at 3 ° C and 1 ° C. the difference in turbidity at the two temperatures (delta NTU) was calculated. Said value is related to the AKD concentration. The following results were obtained .1 c r .- 1 | r v: «1« 1 <- c rr r cur <-c «a ~ cv. f- »= 6 -for the two stock solutions as a result of the determination of the turbidity.

Stock A (x mg / l AKD) Stock B (x + 22.5 mg / l AKD) Turbidity (NTU) '35 ° c 52.7 67.2 15 ° c 72.0 96.5 Delta NTU 19.3 The 29.3 AKD content can now be determined by the "standard addition" method 19.3 / 29.3 = x / (x + 22.5) which gives x = 43 mg / l, ie. well corresponding to the actual concentration in sample A (40 mg / l).

Example 2 Analyzes were performed on a typical laboratory-prepared fine paper stock. The stock consisted of 70% of a mixture of bleached sulphate pulp (60/40 hardwood and softwood) and 30% filler chalk fi The concentration of the stock was 5 g / l and a number of samples with varying AKD concentration were prepared from said stock.

The samples were acidified with aluminum chloride / hydrochloric acid in the same manner as in Example 1 and filtered and analyzed by turbidity measurements and standard addition methodology. The test personnel who made the mentioned measurements were unfamiliar with the AKD concentration in the samples. The results of the analyzes are shown below.

Actual AKD concentration AKD (mg / l) analyzed (mg / l) according to the invention 20 18.3 30 30.5 40 39.2 20 18.3 30 29.2 40 36.8 15 15.0 25 25.6 35 30.8 ... . (-0 '* _ _ V. e. («, .. 1. f. F”. I: _. = - «» i. <1 <<' “'_ _, o ..,. W» 7 18 17.2 38 37.3 22 20.4 8 10.1 18 18.8 12_ 19 30 42 20 23.2 20 22.1 30 34.6 25 24.5 as 37.9 21.7 24 20 Example 3 The method according to the invention was tested on a commercial cardboard machine, the cardboard produced with this machine consisting of four layers, the fiber pulp used consisted partly of bleached chemical pulp (bleached sulphate (hardwood / softwood) and partly of CTMP (chemical mechanical pulp ).

Samples were taken from each layer from the cardboard machine, one from the headbox and one from the backwater, a total of 8 samples from the four skis. The samples were acidified to pH 2 with a brine, 30% CaCl 2 x 2 H 2 O in 6M hydrochloric acid. The samples were filtered in the same manner as described in Example 1.

The turbidity was then determined for each sample at two temperatures, 10 and 40 ° C, and the turbidity difference was calculated (Delta NTU). A portion of each sample was also taken to determine the AKD concentration by HPLC (High Pressure Liquid Chromatography).

The following results were obtained for these analyzes. . 17.1 514 446 8 r _ l _ _ Tmbidire: _ 'rurbidiwz .beiga NTU' Arm-koncen- * 1o ° c (Nm) 7 4o ° c (NTU) '(NTuy uammïPLc ÛMM) Inloppslåda 1 ass 344 44 32 2 - _ ... 304 ~ 284 å 20 25 3 116 108 s 9 E 4 214 210 4 6 Bakvanen 1 17s 166 12 12 2 171 162 9 10 3 66 s1 s 6 4 77 76 1 2 Delta NTU according to the invention shall be related to the AKD concentration and as can be seen from the results, a good correlation is obtained between delta NTU and AKD concentration. The correlation coefficient in this case is 0.96.

Claims (7)

z. f '-mi' .ß f = f '_ 1 _ ~ ..._ ~ f »ß (., .t V« .x: “UKS« «« 1... n »<-. noe : _ more 9 PATENT REQUIREMENTS Method for determining the concentration of AKD in stock and effluent, characterized in that an optical method is used for determining the transmitted and / or scattered light on the one hand at a temperature during the phase transformation and on the other hand at a temperature above the phase transformation in an AKD-containing sample of stock or backwater and that the difference thereafter is calculated. 2. A method according to claim 1, characterized in that the difference in transmitted and / or scattered light relates to the difference in turbidity (delta NTU). 3. A method according to claims 1-2, characterized in that the turbidity is measured after the removal of coarse fibers. 4. A method according to claims 1-3, characterized in that the coarse fibers are removed by adding acid and possibly filtering the stock solution or the backwater. 5. A method according to claims 1-4, characterized in that a stock solution or effluent of known concentration is prepared and used as standard. 6. A method according to claims 1-5, characterized in that the turbidity is measured by visual determination by standard optical methods. A method according to any one of the preceding claims, characterized in that the concentration of AKD in the sample is calculated according to the standard addition technique.