Source: https://patents.justia.com/patent/4647617
Timestamp: 2020-07-03 10:57:18
Document Index: 664538359

Matched Legal Cases: ['arts    5', 'arts\n3', 'arts     5', 'arts\n4', 'arts     5', 'arts\n5', 'arts     5']

US Patent for Water absorbent crosslinked polymer and a method of producing the same containing cellulosis fibers Patent (Patent # 4,647,617 issued March 3, 1987) - Justia Patents Search
Justia Patents Cellulose Or Derivative, E.g., Cotton, Paper Pulp, Etc.US Patent for Water absorbent crosslinked polymer and a method of producing the same containing cellulosis fibers Patent (Patent # 4,647,617)
Jan 16, 1986 - Hayashikane Shipbuilding & Engineering Co., Ltd.
To obviate such a difficulty, there have been proposed the following polymerization methods. One of them is a reverse phase suspension polymerization method in which polymerization is effected in a dispersion having fine particles of the aqueous reaction solution dispersed in an oily phase. With respect to this method, reference may be made to, for example, Japanese Patent Application Laid-Open Specification No. 53-46389/1978. Another is a method in which polymerization is effected using a redox system radical initiator in a reaction vessel, which has a large contact area and thus can be advantageously utilized permitting control of the temperature, at a relatively low temperature, i.e. a temperature less than 80.degree. C., over a prolonged period of time. In this method, crosslinking during the polymerization step can be prevented, and crosslinking of the polymer molecules can be effected during the heat drying step by the use of a polyhydric alcohol as a crosslinking agent. With respect to this method, reference may be made to Japanese Patent Application Laid-Open Specification No. 55-84304/1980.
In the present invention, in an aqueous solution containing at least 30% by weight, based on the total weight of the aqueous solution, of a monomeric component is dispersed a fibrous cellulosic material in an amount ratio of monomeric component to cellulosic material of from 95/5 to 50/50 by weight, so that when the mixture is heated in step 3, the maximum temperature of the mixture is controlled in the range of from just above 100.degree. C. to about 110.degree. C. The resulting mixture is subjected to polymerization reaction. That is, the mixture is heated at a temperature of about 60.degree. to about 110.degree. C., preferably about 80.degree. to 100.degree. C. The heat of polymerization can be removed due to the smooth evaporation of water from the mixture. The polymerization reaction proceeds rapidly under controlled conditions, and generally terminates within 10 minutes. A preferred content of a monomeric component in the aqueous solution is 30% by weight or more from the viewpoint of production efficiency. It is especially preferred that the content do not exceed 60% by weight from the viewpoint of the solubility of alkali metal acrylates in water.
The fibrous cellulosic material incorporated in the aqueous solution exerts its effect by the formation of passages through which the steam can smoothly evaporate from the polymerization mixture heated by the heat of polymerization up to a temperature exceeding 100.degree. C. It is surprising that the incorporation of a fibrous cellulosic material has a marked effect even in a small amount as shown in the drawing. Thus, it is to be noted that an aqueous solution containing acrylic acid in a high concentration can be subjected to polymerization in a simple form of reactor under controlled conditions. Therefore, the method of the present invention is extremely advantageous over the conventional methods from the economical point of view.
120 parts of the resulting aqueous solution were sprayed over 40 g of commercially available absorbent cotton. The solution was allowed to permeate evenly into the cotton to obtain a mixture. The mixture was put in a reaction vessel, flushed with nitrogen gas and closed. The vessel was heated. When the temperature of the mixture was elevated to about 80.degree. C., initiation of polymerization reaction was observed. When the temperature of the mixture was further elevated and water evaporation was observed, heating of the vessel was stopped. At this time, the temperature of the mixture was about 100.degree. C. The polymerization reaction terminated within about 5 minutes. The maximum temperature of the mixture was about 103.degree. C.
Thereafter, the resulting product was dried at a temperature of 120.degree. C. and pulverized into a powdery material. It was found that the powdery material contained 40% of fibrous cellulosic material based on the weight of the dried product. The absorbency of the product was measured as follows. 1 g of the powdery product was separately put in a large volume of water and a 0.9% sodium chloride aqueous solution, and 30 minutes later the formed gel was filtered with a 60-mesh sieve and subjected to weighing. Results are shown in Table 1.
Water 0.9% NaCl Solution
Powder        180     22
Polymer*      450     54
*Absorbency of the polymer contained in the powdery product
Example     aqueous solution
absorbent pulp
2           110 parts    5 parts
3           70 parts     5 parts
4           50 parts     5 parts
5           30 parts     5 parts
These mixtures were heated in nitrogen atmosphere while stirring substantially in the same manner as described in Example 1. Polymerization reaction proceeded with vigorous generation of steam and terminated within 10 minutes. It was found that the temperature of the reaction mixture never exceeded 104.degree. C.
The above-obtained products were dried on a drum drier having a surface temperature of 130.degree. C., and further in a drier kept at 120.degree. C. After drying, the products were pulverized.
Content of            0.9% NaCl
Example   Pulp (%)   Water (g/g)
2   Powder     9         565      53
Polymer              620      58
3   Powder    15         520      48
Polymer              610      56
4   Powder    21         480      40
Polymer              605      51
5   Powder    30         410      31
Polymer              580      44
To 100 parts of the above-obtained aqueous solution was added 12 parts of commercially available absorbent pulp to obtain a uniform mixture. The mixture was heated in nitrogen atmosphere while stirring substantially in the same manner as described in Example 1. Polymerization reaction proceeded with the generation of steam and terminated within 10 minutes. Temperature of the reaction system rose up to 103.degree. C. The obtained product was treated in substantially the same manner as in Examples 2 to 5 to obtain a dried powder. The powder contained 25% of pulp. Results of measured absorbency are shown in Table 4.
Powder        410     35
Polymer       550     47
5.8 parts of absorbent pulp were dispersed evenly in 80 parts of the resulting aqueous solution to produce a mixture. The mixture was heated in nitrogen atmosphere while stirring substantially in the same manner as described in Example 1. Polymerization reaction proceeded with the generation of steam and terminated within 10 minutes. The maximum temperature of the reaction system was 103.degree. C. The obtained product was treated in substantially the same manner as in Examples 2 to 6 to obtain a dried powdery product. The product had a pulp content of 12% as calculated on the basis of the weight of the dried product. Results of the measured absorbency are shown in Table 5.
Powder        405     37
Polymer       460     42
5 parts of absorbent pulp was dispersed evenly in 80 parts of the above-obtained aqueous solution to prepare a mixture. Then, the mixture was heated in nitrogen atmosphere while stirring substantially in the same manner as described in Example 1. Polymerization reaction proceeded with the generation of steam and terminated within 10 minutes. Maximum temperature of the reaction system was 103.degree. C.
Separately, another portion of the product was dried in a drier at 130.degree. C. for 2 hours and thereafter pulverized to obtain a powdery product. The powdery product had a pulp content of 16% as calculated on the basis of the weight of the powdery product. Results of measured absorbency are shown in Table 6.
Powder        320     31
Polymer       380     37
An aliquot of the aqueous solution as employed in Examples 2 to 5 was poured into a vessel made of stainless steel to form a thin layer of the solution having a thickness of 4 mm. The vessel was put on a hot plate maintained at a temperature of 100.degree. C. and the vessel was flushed with nitrogen gas. Because the reaction mixture was in the form of a thin layer, water evaporation was smooth, and the polymerization reaction was completed within about 10 minutes.
The resulting product obtained in the form of a sheet was dried in a dryer at a temperature of 120.degree. C. for 4 hours and pulverized into a powdery product to obtain a comparative sample. The powdery product obtained in Example 2 and the above-mentioned comparative sample were sifted with a sieve to obtain respective powdery products having a particle diameter of 40 to 80 mesh (Tyler). The absorbencies of the respective powdery products for water and 0.9% NaCl solution were measured by the method described in Example 1. Results are shown in Table 7.
Example 2       570     53
(Polymer*)      (620)   (57)
630     56
Thereafter, the absorption rates of both samples were respectively measured. 0.5 g of the powdery product of each sample was put in a tea bag made of a nonwoven rayon fabric having a size of 7 cm.times.7 cm. The tea bag was put in a 0.9%. NaCl solution, lifted after predetermined periods of time and weighed to measure the absorbency. Results are shown in Table 8.
Example 2  (Polymer*)
2       39         (43)      29
5       44         (48)      36
30      45         (50)      46
60      45         (50)      52
2. A polymer according to claim 1, wherein in step (3), the mixture is heated at a temperature of about 60.degree. to about 110.degree. C.
3. A polymer according to claim 2, wherein the mixture is heated at a temperature of about 80.degree. to about 100.degree. C.
5. A polymer according to claim 1, wherein the aqueous solution is mixed with the fibrous cellulosic material in an amount ratio of monomeric component to fibrous cellulosic material of 95/5 to 50/50 by weight, so that when the mixture is heated in step (3), the maximum temperature of the mixture is controlled in the range of from just above 100.degree. C. to about 110.degree. C.
3682856 August 1972 Adams et al.
3953386 April 27, 1976 Murphy et al.
2612846 October 1976 DEX
53-46389 April 1978 JPX
0204673 November 1984 JPX
Application Number: 6/819,790
Current U.S. Class: Cellulose Or Derivative, E.g., Cotton, Paper Pulp, Etc. (524/733); Wood Or Wood Cellulose Fiber Or Flour (524/13); Monomer Is Carboxylic Acid Or Derivative (524/832); Unsaturated Carboxylic Acid Or Derivative Reactant (527/314)
International Classification: C08L 108; C08F25102; C08F12006;