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KR-102964250-B1 - Method for manufacturing cross-linked cellulose ether

KR102964250B1KR 102964250 B1KR102964250 B1KR 102964250B1KR-102964250-B1

Abstract

A method for preparing a cross-linked cellulose ether comprising: (i) contacting at least one cellulose material with a mixture comprising (ia) at least one crosslinking agent and (ib) at least one alkalizing reagent to form an activated cellulose material; and (ii) contacting the activated cellulose material of step (i) with at least one etherifying reagent; wherein the at least one etherifying reagent reacts with the activated cellulose material to form the cross-linked cellulose ether; and a cross-linked cellulose ether prepared by the method.

Inventors

  • 힐트, 알렉산드라
  • 노이바우어, 외르크
  • 멘츠, 존야
  • 슈프레헤, 마티아스
  • 슈레크, 미카엘

Assignees

  • 다우 글로벌 테크놀로지스 엘엘씨

Dates

Publication Date
20260513
Application Date
20200417
Priority Date
20190501

Claims (12)

  1. A method for manufacturing cross-linked cellulose ether, (i) a step of contacting at least one cellulose material with a mixture comprising (ia) at least one crosslinking agent and (ib) at least one alkalizing reagent to form an activated cellulose material; and (ii) a step of contacting the activated cellulose material of step (i) with at least one etherifying reagent; wherein the at least one etherifying reagent reacts with the activated cellulose material to form the cross-linked cellulose ether, and The above at least one etherification reagent is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, methyl chloride, ethyl chloride, and mixtures thereof, and A method in which at least one of the crosslinking agents is a diglycidyl ether type crosslinking agent having the following chemical structure formula (I). Structural formula (I) In the above formula, n is 3 to 25.
  2. A method for manufacturing cross-linked cellulose ether, (A) (a) a step of mixing at least one crosslinking agent with (b) at least one alkalizing agent to form a crosslinking agent/alkalinizing agent mixture; (B) a step of contacting at least one cellulose material with the mixture of step (A) to form an activated cellulose material; and (C) a step of contacting the activated cellulose material of step (B) with at least one etherification reagent; said at least one etherification reagent reacts with said activated cellulose material to form a cross-linked cellulose ether, and The above at least one etherification reagent is selected from the group consisting of ethylene oxide, propylene oxide, butylene oxide, methyl chloride, ethyl chloride, and mixtures thereof, and A method in which at least one of the crosslinking agents is a diglycidyl ether type crosslinking agent having the following chemical structure formula (I). Structural formula (I) In the above formula, n is 3 to 25.
  3. A method according to claim 1 or 2, further comprising the step of applying one or more of purification, washing, drying, granulation, and milling steps to the cross-linked cellulose ether.
  4. A method according to claim 1, wherein the activated cellulose material is formed at a pressure of 500 kilopascals or less and a temperature of 50°C or less.
  5. A method according to claim 1, wherein the cross-linked cellulose ether is formed at a pressure of 1,000 kilopascals or more and a temperature of 70°C or more.
  6. ◈Claim 6 was waived upon payment of the establishment registration fee.◈ A method according to claim 1, wherein at least one alkalizing reagent is selected from the group consisting of solutions of sodium hydroxide, potassium hydroxide, lithium hydroxide, and mixtures thereof.
  7. ◈Claim 7 was waived upon payment of the establishment registration fee.◈ A method according to claim 1, wherein at least one cellulose material is selected from the group consisting of wood pulp, cotton linter, and mixtures thereof.
  8. ◈Claim 8 was waived upon payment of the establishment registration fee.◈ A method according to claim 1, wherein steps (i) and (ii) are performed in an inert atmosphere.
  9. The method of claim 1, wherein the at least one crosslinking agent is present in the mixture of step (i) at a concentration of 0.0001 mole of the crosslinking agent per mole of anhydrous glucose unit of the cellulose ether to 0.05 mole of the crosslinking agent per mole of anhydrous glucose unit of the cellulose ether; and the at least one alkalizing reagent is present in the mixture of step (i) at a concentration of 1 mole of the alkalizing reagent per mole of anhydrous glucose unit of the cellulose material for forming the activated cellulose material to 3.5 moles of the alkalizing reagent per mole of anhydrous glucose unit of the cellulose material.
  10. The method of claim 1 further comprises the step of crushing at least one cellulose material to form a crushed cellulose floc material; wherein the crushing step is performed before contacting the at least one cellulose material with the mixture of step (i).
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Description

Method for manufacturing cross-linked cellulose ether The present invention relates to a method for producing cross-linked cellulose ether and cross-linked cellulose ether produced by such method. Cellulose derivatives, such as cellulose ethers, are widely used for various purposes—e.g., thickeners, adhesives, binders and dispersants, water retention agents, protective colloids, stabilizers, suspending agents, emulsifiers, and film-forming agents—due to their excellent properties and physiological safety. Additionally, cellulose ethers are known to be used in dry-mix mortars in various construction applications to improve the fluidity of the mortar. Furthermore, cellulose ethers are used in mortars to impart water retention properties that limit water loss from the mortar to the absorbent substrate. This allows the hydraulic binder (cement or gypsum) to utilize sufficient water during the curing reaction, thereby increasing the mechanical strength of the final product. A lack of water results in incomplete curing, poor mechanical strength, crack formation, and low abrasion resistance. To date, cellulose ethers have been produced by widely known conventional methods comprising applying a cellulose starting material, such as cellulose pulp, to two process operations (steps), namely (1) an alkalization operation and (2) an etherization operation. A widely known, modern conventional procedure for producing cellulose ethers is exemplified and described, for example, in U.S. Patent No. 6,235,893 B1. The conventional method comprises (1) a step of alkalizing the cellulose pulp; and (2) a step of etherizing the alkalized cellulose pulp to form cellulose ethers. For example, in the conventional method, the cellulose pulp is alkalized with sodium hydroxide and etherized with methyl chloride and alkylene oxide (ethylene oxide or propylene oxide). Additionally, the alkalization and etherification operations can each be performed stepwise, that is, in a single step or in two or more separate individual steps, and each step can be performed for a set period under specific process conditions of pressure and temperature. After the cellulose ether is prepared, the cellulose ether may undergo additional desired process steps, for example, (3) a step of washing the cellulose ether; (4) a step of drying the cellulose ether; and (5) a step of milling the cellulose ether into a fine particle form. Typically, the alkalization and etherification operations can be performed in a single reactor or in two or more reactors. More recently, conventional methods for producing cellulose ethers have been improved by using a crosslinking technique to produce crosslinked cellulose ethers. The crosslinking technique comprises cellulose ethers that can be chain-extended or crosslinked using a difunctional crosslinking agent such as methylene dichloride, epichlorohydrin, or various diglycidyl ethers. For example, U.S. Patent No. 6,958,393 B2 (identical to European Patent EP1384727B9) discloses a method for producing a polyether group containing a crosslinked cellulose ether using a crosslinking technique. The crosslinked cellulose ether is produced by crosslinking the cellulose ether at 90°C (°F) or lower in an inert atmosphere, for example, nitrogen ( N₂ ), in the presence of a polyether group containing a crosslinking agent and in the presence of a corrosive agent or an alkali. The crosslinking of the above cellulose ether occurs in the presence of the above corrosive agent or alkali in the reactor in which the above cellulose ether itself is produced. In contrast to pure, uncrosslinked cellulose ether, for example in dry-mix mortar formulations, one advantage of using crosslinked cellulose ether is that by crosslinking the cellulose ether with a crosslinking agent, the viscosity of the aqueous solution of the cellulose ether can be increased, and the resulting crosslinked cellulose ether with increased or high viscosity can still remain water-soluble in the aqueous solution. Additionally, crosslinked cellulose ether with increased or high viscosity, prepared using crosslinking technology, can be used at reduced dosage levels, for example in mortar applications, without compromising the product and application performance. Cellulose ether is a relatively expensive component used in mortar formulations, and any reduction in the dosage of cellulose ether in said formulation can reduce the cost of the formulation. In previously known methods, the dosage of the crosslinking agent used to crosslink cellulose ethers is kept very low to prevent "over-crosslinking," which ultimately provides a crosslinked polymer product that remains water-insoluble and does not affect the viscosity of the aqueous solution. However, it is very difficult to achieve a uniform distribution of a small amount of crosslinking agent added to the contents of a large reactor using previously known methods. With respect to crosslinking cellulose ethers, "over-crosslinking" as