JPS5951567B2 - Method for crushing water-soluble vinyl polymer hydrogel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for crushing a hydrogel of a water-soluble vinyl polymer used as a polymer flocculant.

More specifically, the present invention relates to a method of crushing the water-containing gel of the water-soluble vinyl polymer into particles or strings at a specific temperature range. Various polymer flocculants are used for purposes such as clarification of various types of water, flocculation of suspended particles, and dewatering of various types of sludge, among which acrylamide, acrylate, and dimethylaminoethyl methacrylate are used. A mineral acid salt, a quaternized product of dimethylaminoethyl methacrylate (refers to a quaternary ammonium salt in which the amino group is alkylated with methyl chloride, etc.).

Water-soluble vinyl polymers, such as homopolymers and copolymers such as There is.
It is well known that the higher the molecular weight of a polymer flocculant, the better its performance. This is because the aggregation of fine particles caused by the polymer flocculant occurs through cross-linking between the particles due to the polymer, and therefore, the higher the molecular weight, the greater the cross-linking effect. For example, in the case of polyacrylamide, it is desired to have a molecular weight of over 10 million, and depending on the application, a molecular weight of over 15 million. The water-soluble vinyl polymer used as a polymer flocculant is obtained by polymerizing a vinyl monomer in an aqueous solvent using a polymerization initiator to obtain an agar-like hydrogel of a water-soluble vinyl polymer. This hydrogel is dried and then ground to produce a powdered product.

In order to increase the surface area for efficient drying of the hydrogel, the hydrogel is crushed into particles or strings prior to drying. The hydrogel is usually crushed using a screw extruder, and is crushed into particles or strings having a diameter of 1 to 10 mm. Granular products can be obtained using an extruder equipped with a rotating knife at the tip of the screw, and string-like products can be obtained using an extruder without a rotating knife. Water-soluble vinyl polymer hydrogel is difficult to crush with a normal crusher or mixer due to its elasticity, but the screw type extruder can crush such hydrogel into granules. Suitable for making into objects or string-like objects.

However, such a method of crushing a hydrogel using a single-screw extruder has major drawbacks. That is, during the process of crushing the hydrogel using the Starille type extruder, the molecular weight of the water-soluble vinyl polymer decreases. In order to increase the drying efficiency of hydrogel, the smaller the hole diameter of the die of the single-screw extruder, the more difficult it is to obtain particles or strings with smaller diameters. Significant decrease in molecular weight. Moreover, the higher the molecular weight of the water-soluble vinyl polymer before crushing, the greater the degree of molecular weight reduction during the crushing process. This decrease in molecular weight is caused by
It is thought that this is caused because the hydrogel is kneaded inside the Starille type extruder and some of the molecular chains of the water-soluble vinyl polymer are cut. It is clear that these drawbacks are a very serious obstacle when attempting to produce a high molecular weight, water-soluble vinyl polymer with excellent performance as a polymer flocculant. As a result of intensive research to solve these drawbacks, the present inventor found that when crushing a hydrogel using a single-screw extruder, if the crushing is performed within a specific temperature range, the molecular weight can be reduced during the crushing process. The present inventors have discovered that the crushing capacity per unit time of the single-screw extruder can be significantly improved without causing any deterioration, and have completed the present invention.

That is, the present invention is directed to the following A used as a polymer flocculant:
,B,C,D,EA. Acrylamide homopolymer B. Homopolymer of unsaturated fatty acid and its salt C. Homopolymer D of unsaturated fatty acid aminoalkyl esters, their salts and quaternized compounds thereof D. Copolymers of two or more monomers selected from acrylamide, the unsaturated fatty acids described in B and their salts E. A water-soluble vinyl polymer selected from the group of copolymers of two or more monomers selected from acrylamide, unsaturated fatty acid aminoalkyl esters described in C, salts thereof, and quaternized products thereof. The combined water-containing gel is crushed at a temperature of 70° C. or more and 110° C. or less through a screw-type extruder equipped with a rotating screw inside a cylinder and a die having a plurality of holes in the cylindrical protrusion. This is a method for crushing a water-soluble vinyl polymer hydrogel.

The homopolymers described in B include homopolymers of unsaturated fatty acids such as acrylic acid and methacrylic acid, and homopolymers of salts of the unsaturated fatty acids with caustic soda, caustic potash, etc.

Among the homopolymers described in C, homopolymers of unsaturated fatty acid aminoalkyl esters such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate; Included are homopolymers of salts such as hydrochloric acid and sulfuric acid, and homopolymers of quaternary compounds such as methyltaloride of the unsaturated fatty acid aminoalkyl ester and dimethyl sulfuric acid. Among the copolymers described in D, acrylamide and acrylic acid, atarylamide and sodium acrylate, acrylic acid and sodium arylate, acrylic acid and methacrylic acid, sodium arylate and sodium methacrylate, sodium acrylate and acrylic acid Copolymers of combinations of potash, acrylamide, atarylic acid, and sodium acrylate are included.
Among the copolymers described in E, acrylamide and dimethylaminoethyl metatarylate (abbreviated as DM), sulfates of acrylamide and DM, methyltalolide quaternized products of acrylamide and DM, sulfates of DM and DM , DM and methyl chloride quaternized product, DM sulfate and DM
Methyl chloride quaternized product, DM and diethylaminoethyl methacrylate (abbreviated as DE), DM sulfate and DE sulfate, DM sulfate and DM hydrochloride, DM methyl chloride quaternized product and DE methyl chloride quaternized products, methyl chloride quaternized products of DM, dimethyl sulfate quaternized products of DM, acrylamide and DM sulfates, acrylamide, DM, and methyl chloride quaternized products of DM,
Acrylamide and DM sulfate and DM methyl chloride quaternized product, atarylamide and DM and DM sulfate and D
Copolymers of combinations such as quaternized methyl chloride of M are included. As long as the water solubility of the polymer is not lost,
The water-soluble vinyl polymers A to E may contain other vinyl monomers such as acrylonitrile, methyl methacrylate, etc. in the form of a copolymer.

In this case, in order not to lose water solubility, the amount of other vinyl monomers is 10 mol% or less. The water-soluble vinyl polymer hydrogel is a highly elastic agar-like substance containing the water-soluble vinyl polymer and water. The content of the water-soluble vinyl polymer and water is usually in the range of 10 to 70% by weight for the water-soluble vinyl polymer and 30 to 90% by weight for water. The hydrogel may have a size and shape that can be fed to a screw type extruder. Such a water-containing gel can be prepared by adding the vinyl monomers described in A to E above in an aqueous solvent and using a common polymerization initiator such as a peroxide such as potassium persulfate or ammonium persulfate, azobisisobutyronitrile, It can be obtained by polymerization using an azo compound such as azobiscyanovaleric acid or a redox catalyst in which the above-mentioned peroxide is combined with a reducing substance such as sodium bisulfite or triethanolamine. The screw type extruder of the present invention includes:
It has a rotating screw inside a cylinder, and a die with multiple holes at the exit of the cylinder.
Meat chips (1) or structures similar to these.

A screw type extruder is used to crush a water-soluble vinyl polymer hydrogel into granules or strings. A screw-type extruder can be provided with a rotating knife before or after the cylindrical outlet, and when a screw-type extruder having a structure with a screw-type knife is used, the water-containing gel is crushed into granules; When using a screw type extruder having no structure, the hydrogel is crushed into strings. A cylindrical exit die with a hole diameter of 1 to 10 mm is used. In order to increase the efficiency of drying the crushed hydrogel, it is preferable to use a die with a small hole diameter of 1 to 5 mm. In the present invention, when crushing a hydrogel of a water-soluble vinyl polymer using a screw extruder, it is an essential requirement that the hydrogel be crushed at a temperature of 70°C or higher and 110°C or lower.

At temperatures lower than 70° C., the effect of the present invention appears and the molecular weight decreases.

In addition, at temperatures higher than 110°C, water evaporates from the hydrogel so much that it becomes impossible to maintain the hydrogel state, and the surface of the hydrogel foams, making it difficult to crush with an extruder. becomes. It is necessary to maintain the hydrogel residing in the extruder at a temperature of 70° C. or higher and 110° C. or lower by heating the hydrogel before or during supply to the screw type extruder. The method of heating the hydrous gel may be any method that can be normally performed, such as wrapping the hydrogel in a polyethylene bag and heating it in heated water or heated air, or heating the hydrogel on a heated metal plate. A heating method, a method of heating a hydrous gel with microwaves, etc. can be used. According to the method of the present invention, a hydrogel can be easily crushed into granules or strings without reducing the molecular weight of the water-soluble vinyl polymer.

Furthermore, the ability to crush hydrogel (the amount of crushing per unit time) of the screw type extruder can be significantly improved. According to the method of the present invention, even if the hole diameter of the screw-type extruder die is set to 5 mm or less and the hydrogel is crushed into small-diameter particles or strings, the molecular weight of the water-soluble vinyl polymer can be reduced. Therefore, it is possible to efficiently dry the granular or string-like hydrogel and obtain a high molecular weight water-soluble vinyl polymer product with excellent performance as a polymer flocculant. Next, the method of the present invention will be specifically explained using Examples.

Example 1 A 30% by weight aqueous solution of acrylamide was prepared in a polyethylene bottle, and nitrogen gas was blown into the bottle, and the solution was blown into a polyethylene bottle, and then the azobiscyanovaleric acid 2000p monomer standard (hereinafter referred to as Plm?) was prepared. (Same as above), ammonium persulfate 50P11m, and sodium bisulfite 20ppn were added to carry out polymerization to obtain an agar-like hydrogel.

The hydrous gel was cut into a plate shape of 50 mm x 50 mm x 10 mm, wrapped in a polyethylene bag and heated in hot water at 60°C, 80°C and boiling water at about 100°C for 30 minutes. Remove the heated plate-shaped gel from the polyethylene bag and immediately place it in a meat grinder (screw diameter 70 mm, length 156 mm,
The powder was crushed by supplying it to a machine (having a pitch number of 3.3, a rotation speed of 180 rpm, and a rotating cross-shaped knife in front of the die) to obtain a granular crushed product. Using the above method, the hydrogel was crushed by changing the hole diameter of the die of the meat grinder, and the crushing speed was measured.
Polyacrylamide obtained by hot air drying for 1 hour at 30℃
The intrinsic viscosity in a 1N aqueous sodium nitrate solution was measured, and the molecular weight was determined using the following formula.

[η]=3.73×10-4Mw0.66 (however, [
η] is the intrinsic viscosity of polyacrylamide in a 1N aqueous sodium nitrate solution at a temperature of 30°C, and MW is the weight average molecular weight of polyacrylamide.

), and instead of crushing the heated hydrogel with a meat grinder, the polyacrylamide was cut into 3 mm square pieces with scissors and similarly dried with hot air, and the intrinsic viscosity of the obtained polyacrylamide was measured to determine the molecular weight.

The results are shown in Table-1.

Although cutting with scissors is not suitable for industrial use, there is little damage due to a decrease in molecular weight, unlike when crushing using a single-screw extruder.

Displayed as an illustrative example for comparison. Example 2 Polyacrylamide hydrous gel obtained by polymerization in the same manner as in Example 1 was cut into plates of 50 mm x 50 mm x 10 mm, placed in a stainless steel box of the same size, and sealed tightly.
It was heated in heated air at 110°C and 120°C for 1 hour.

The heated gel plate was taken out and immediately fed to the same meat grinder as in Example 1. The hydrogel heated to 110° C. could be crushed without any problem, but the hydrogel heated to 120° C. caused significant foaming due to water evaporation, making it difficult to crush.

The measurement results of crushing speed and molecular weight are shown in Table 2. Example 3 A 25% by weight aqueous solution of sodium acrylate was prepared and polymerized in the same manner as in Example 1 to obtain a hydrogel.

The hydrogel was heated in the same manner as in Example 1 and then crushed into granules using a meat grinder, and the crushing speed was measured. In addition, 3 of sodium polyacrylate obtained by drying the crushed material in the same manner as in Example 1.
The intrinsic viscosity was measured in an aqueous solution of 2N caustic soda at 0°C. Further, in the same manner as in Example 1, the heated gel was cut with scissors and the intrinsic viscosity of the obtained sodium polyacrylate was measured. The results are shown in Table-3.

At 60°C, the molecular weight decreases significantly, but at 80°C,
It is shown that no decrease in molecular weight occurs at 100°C.

Example 4 A 65% by weight aqueous solution of dimethylaminoethyl metatarylate quaternized with methyltalolide was prepared, and in the same manner as in Example 1, 3000 ppn of azobiscyanovaleric acid, 200 pIm of ammonium persulfate, and 8 ml of sodium bisulfite were added.
Polymerization was carried out by adding 0 ppn to obtain a hydrogel.

The hydrogel was heated in the same manner as in Example 1 and then crushed into granules using a meat grinder, and the crushing speed was measured. Further, the intrinsic viscosity of the polymer obtained by drying the crushed material in the same manner as in Example 1 was measured in a 1N aqueous solution of sodium nitrate at 30°C. Further, in the same manner as in Example 1, the heated gel was cut with scissors, and the intrinsic viscosity of the dried polymer was measured. The results are shown in Table 4.

At 60°C, a decrease in molecular weight occurs, but at 80°C, 1
In the case of 00°C, it is shown that no decrease in molecular weight occurs.

Example 5 28% by weight of acrylamide, 7% by weight of sodium acrylate
An aqueous solution was prepared, and polymerization was carried out in the same manner as in Example 1 to obtain a hydrogel.

The hydrogel was heated in the same manner as in Example 1 and then crushed into granules using a meat grinder, and the crushing speed was measured. Further, the intrinsic viscosity of the polymer obtained by drying the crushed material in the same manner as in Example 1 in an aqueous solution of 1N sodium nitrate at 30° C. was measured. Further, in the same manner as in Example 1, the heated gel was cut with scissors, and the intrinsic viscosity of the dried polymer was measured. The results are shown in Table-5.

At 60°C, the molecular weight decreases significantly, but at 80°C,
It is shown that no decrease in molecular weight occurs at 100°C.

Next, some of the obtained polymers were selected and subjected to an agglomeration test using a 2.5% suspension of kaolin (Iil7.4).

300ml of kaolin suspension in a 500ml cylinder with a stopper
1 was added, 1 ml of an aqueous polymer solution dissolved at 0.1% was added thereto, and the mixture was inverted and stirred five times. The size of the flocs formed, the sedimentation rate, and the light transmittance of the supernatant were measured.

The results are shown in Table-6.

Claims (1)

[Claims] 1. The following A, B, C, D used as a polymer flocculant:
, EA, homopolymer B of acrylamide, homopolymer C of unsaturated fatty acids and their salts, homopolymer D of unsaturated fatty acid aminoalkyl esters, salts thereof and quaternized products thereof, acrylamide, unsaturated as described in B Copolymer E of two or more monomers selected from fatty acids and salts thereof, acrylamide, 2 selected from unsaturated fatty acid aminoalkyl esters, salts thereof, and quaternized products thereof described in C. A hydrogel of a water-soluble vinyl-based polymer selected from the group consisting of copolymers of more than one type of monomer is heated at a temperature of 70°C or higher and 110°C or lower inside a cylinder with a rotating screw at the outlet of the cylinder. 1. A method for crushing a water-soluble vinyl polymer hydrogel, which comprises crushing the hydrogel through a screw extruder equipped with a die having a plurality of holes.