DE1468835A1 - Process for the preparation of alkali salts of carboxymethyl cellulose - Google Patents

Description

E. I. DU PONT DE NEMOUHS AND COMPANY, IQth and Market Streets, Wilmington 98, Delaware, V. St "A",

Process for the production of alkali salts of carboxymethyl cellulose

The invention relates to improvements relating to the production of alkali salts of carboxymethyl cellulose, hereinafter often abbreviated to CMC.

The invention relates to a process for the production of alkali salts of carboxymethyl cellulose by etherification of alkali cellulose in a liquid two-phase system, which is a water-miscible aliphatic alcohol, preferably in an amount of at least? % By weight of the total liquids initially present, wherein one phase is aqueous alcohol and the other is a mixture of an inert, water-immiscible liquid with alcohol contains, and the water preferably initially in an amount of 0.0? up to 3 * 4 parts and all of the liquid

H? th in an amount of 4 to 20 parts per part by weight of dry

^ q kener cellulose, present _v treat the obtained Gart- = · CD

^ ₃ - O'xymethylcellulose in the liquid two-phase system with a

Bleaching agent to reduce its viscosity and recover the bleached carboxymethyl cellulose from the liquid two-phase system, generally by removing liquid and using conventional methods o The bleaching agent is expediently added to the liquid system while the usual agitation is continued, preferably for at least 1 minute, for example for up to 20 minutes, and while the bleaching action is allowed to continue, if desired, and the system is still at etherification temperatures, for example 40 ~ 80 ° C, generally after more than about 90% of the etherification agent has reacted with the alkali cellulose, the exact time depends on the reaction conditions, for example, only about 5 minutes at 80 ° C and up to about 160 minutes at 40 ° C, the time is measured from that point on _$ where the tem- 'perature is reached first. The CMC obtained can be obtained by ordinary working methods. Details of the etherification conditions, including suitable materials and proportions, are more fully provided in US Pat. No. 2,976,278, which corresponds in part to British Pat. No. 772,183, and the DAS. .. "... (patent application P 36 648 IVb / 12o) specified.

Suitable bleaching agents include customary reducing agents such as peroxides, perborates, periodates, hypohelogenites

BAO ORIGINAL

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especially hypochlorites or hypobromites, and chlorites, J ^ in the form of their free acid or hydrogen derivatives or

O ₀ usually preferably as the sodium salt or other alkali

cd "

<t- salt, for example potassium ™, lithium, rubidium and cesium

salt, but hydrogen peroxide itself is generally preferred as such, if desired the agent can be formed in situ, for example, by passing chlorine through the alkaline slurry to form of a chlorite * The amount of agent is preferably 0.001 to 0.1 parts per part by weight of the original cellulose, although higher amounts are often permissible, for example up to 1 part. The exact one for someone special Approach amount chosen depends on the conditions and materials and the desired degree of bleaching and degradation the viscosity, with higher temperatures, for example, increasing the effectiveness of the bleaching process. Bleach times of 15 to 30 minutes are preferred, but can even only 1 minute or even up to 2 hours in a few Cases are desirable.

The following example illustrates the invention without it restrict. All parts and percentages are based on weight, unless otherwise stated. The terms used have the same meanings as in

the DAS (patent application P 36 648 IVb / 12o). the

The following abbreviations have the meanings given below:

, 909803/1010

T.D.E.

actual degree of etherification, determined by analysis of the product; Average number of ether groups which per anhydroglucose unit of the cellulose molecule (Cell ·) a » have been conducted. This code number is used to classify the ether in terms of its solubility, for example in water and aqueous alkaline solutions.

! Theoretical degree of etherification; Number of moles of etherifying agent, depending on the reaction mixture Anhydroglucose unit have been added.

Alkalization

Excess alkali

Reaction efficiency; Ratio of the actual to the theoretical degree the etherification in percent.

Process of mixing cellulose with alkali in a three-component system before adding the etherifying agent.

j χ 100, in which A mol monochloroacetic acid used and B mol alkali used.

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The color (i.e. whiteness or reflection) of the bleached CMC is measured with a "photoelectric photovolt reflector"

xionsmeßgerät ⁿ (Photovolt Photoelectric Reflection Meter) model 610 measured against a ceramic standard. The light hits the sample at an angle of 90 ° C and is viewed at 45 ° C. Four ceramic standards with approximate reflectance 55 »65» 75 and 85 are used. A blue tristimulus filter is used. The meter is set to the correct value for a standard with a reflectance closest to the sample from CMC. The sample cell is filled to the brim and brought into position. The reflection is read directly from the measuring device. The higher the reflection, the whiter the cellulose derivative o

example 1

25 parts of 0.25 mm cellulose (60 mesh US standard) (degree of polymerization - 600) with a 6 % moisture content are mixed with 141.2 parts of benzene and 108.6 parts of 92.4% ethanol Mixture is agitated and 24.4 parts 48.2% aqueous NaOH (25 % excess alkali) are added and the slurry is alkalized at 30 ° C for 30 minutes. 12.3 parts of monochloroacetic acid are added and the slurry is agitated at 35 ° C. for 10 minutes. The slurry is then heated to 63 ° C and agitated for 55 minutes to effect etherification. Then 0.63 parts of 35% hydrogen peroxide are added and agitation is continued for 15 minutes. The slurry is then neutralized with acetic acid and filtered. The product will

ORIGINAL INSPECTED

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washed with aqueous ethanol and dried. It has a D.E. of 0.68, a viscosity (2 ft. solution) of 30.5 cP and a color of 65

In contrast to this, a control test under the appropriate conditions, but with the peroxide omitted, yields a product with a viscosity (2 %) of 400 cP and a color of 75? and another control experiment in which the peroxide is increased to 1.5 parts, but is added to the reaction medium immediately after the addition of the cellulose, d. h «before the addition of monochloroacetic acid, a product with a viscosity (2 %) of 34.6 cP and a color of 73, which shows that the time of adding the bleach is indeed critical o

Klan repeated the same procedure with the exceptions given in Table I, whereby in experiments 7 to 10 the stated amount of H ^ O ^ was added after 40 minutes of etherification and in experiment 10 the liquid medium was 54% benzene and 8 % water instead of 53.5% benzene and 8.5% water.

TABLE I

_g55% gr 0 /

Port T.D.E. Excess g cellulose paint D.E. Viscosity (2%)

(CP)

2 0.9 36 0.037 - ~ 0.68 24, O 3 0.9 36 0.032 85 0.68 26, 4th 4th 0.9 36 0.027 87 0.68 30, 5 5 1.0 25th P.O37 0.80 3

TABLE I continued

g35% HpOp /

No. T.D.E. Excess g cellulose paint D.E. Viscosity (2%)

(cP)

6th 1.0 25th 0.053 87 0.79 24.9 7th 1.0 25th 0.031 0.81 33.4 8th 1.0 12.5 0.031 0.79 51.8 9 1.0 50 0.031 0.78 18.5 10 1.0 25th 0.040 85 0.77 29.0

⁺ The reflection of the cellulose derivative was not measured, but the color was visibly affected and the bleaching effect is retained after cleaning.

The procedure used in experiment 10 is carried out for wood pulp with a degree of polymerization of 1600 using the in Table II indicated bleach repeated o,

TABLE II

Bleach viscosity (1 #) color

Sodium perborate.

Calcium hypochlorite sodium chlorite

10, 3 85 , 5 410 83 , 5 1076 87 , 0

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The working method is based on the use of sodium periodate instead of perborate repeated with similar results.

In contrast, however, in a control experiment the same procedure except that no bleach is added, a product with a viscosity of Ή60 and a color of 779 5 received.

It should be noted in connection with Runs 7 through 9 that it is important that the color be retained after cleaning, as some known bleaching treatments can provide temporary improvement in the further cleaning is subsequently lost.

It is very surprising that the method according to the invention can give good results, since the importance of the Adding the bleaching agent to alkali cellulose in a slurry medium prior to adding the etherifying agent or the Remove liquid from the final CMC by centrifugation before adding the bleach as complete separate and costly treatment stage to avoid a reaction between the alcohol in the slurry medium and the bleach was emphasized.

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Claims (1)

September 29, 1965 ■ ν / P a t e η t ε η a ρ r Process for the preparation of alkali salts of carboxymethyl- ^? cellulose "by alkalizing cellulose with alkali in ^ j- a liquid two-phase system which contains a water-miscible alphatic alcohol with 2 to 4 carbon atoms, in particular ethanol", one bubble of aqueous alcohol and the other of alcohol and one with water immiscible inert liquid, preferably an aromatic hydrocarbon, in particular benzene, toluene or xylene, and subsequent etherification of the alkali cellulose obtained with a suitable etherifying agent, such as monochloroacetic acid _s in the same liquid two-phase system and removal of the liquid from the product obtained, characterized in that the Viscosity of the product is improved by treatment with a bleach after the etherification is practically completed and before the liquid is removed from the product. - 9 909803/1010